TOPICS IN CIVIL ENGINEERING , SCIENCE AND TECHNOLOGY STRUCTURAL ENGINEERING AND CONSTRUCTION MATERIALS

Therefore, the present study investigated the effect of different combinations of polymer and pozzolan namely Styrene Butadiene Rubber (SBR) and Fly Ash (FA) respectively on the surface absorption of mortar using initial surface absorption test (ISAT) [2]. BS 1881: Part 5 defines ISAT as a measurement of the rate of flow of water into concrete or mortar surface per unit area at fixed intervals under constant heat and temperature. The results can be used to indicate the quality of mortar in terms of resistance against water absorption of water that is directly related to durability. SBR is one of the synthetic polymer additives from aqueous polymer latex group used in polymer composite. The presence of polymer membranes gives a sealing effect that enhances the waterproofness or watertightness , increase air permeation and chemical resistance of polymer modified mortar [3] [4]. In other words, the addition of SBR into mortar can improve its resistance against water absorption [5][6]. Meanwhile, FA decreases the permeability by reducing bleed channels, capillary channels and void spaces inside the concrete and mortars through pozzolanic reaction [8][9]. Figure 1: Interaction between material properties, environmental factors and transportation mechanisms of durability of concrete [2]. MATERIALS AND METHODS MATERIALS Polymer and pozzolan used in this study were Styrene Butadiene Rubber (SBR) (Synthomer Grade 29Y46) from Synthomer UK and Fly Ash (FA) respectively. Ordinary Portland Cement (OPC) (ASTM Type 1 recognized by ASTM C150) manufactured by Cahaya Mata Sarawak Cement Sdn. Bhd (CMS) exceeded the quality requirements specified in the Malaysian Standard MS 52: Part 1: 1989 Specifications for Ordinary Portland Cement. The raw materials were clinker (90%), limestone (5%), and gypsum (5%). The chemical and mineralogical characteristics of the OPC are given in Table 1. To study the combination effect of polymer and pozzolan on ISAT, mixtures were prepared with two water to cement ratios (w/c) of 0.3 and 0.4 with different combinations of 5%, 7% & 10% SBR additive and 10%, 20% and 30% FA cement replacement. The mix proportions of all samples are shown in Table 2 and 3. The cement to sand ratio for all samples was 0.6.All samples that were casted into steel moulds of 150 mm X 150 mm X 150 mm cubes. 95

Table 1: Chemical Composition of OPC. Table 2: Mix proportion of 0.3 w / c Table 3: Mix proportion of 0.4 w / c 96

INITIAL SURFACE ABSORPTION TEST (ISAT) Figure 2: Setting of initial surface absorption test according to BS 1881: Part 5 and Part 208. The initial surface absorption was measured through a known mortar surface area. The surface contact area was definite by a plastic cell sealed and clamped onto mortar surface. The volumetric flow rate was obtained by observing the length of flow along a capillary with a known dimension. The general arrangement of the test apparatus is shown in Figure 2. The reservoir and capillary tube were assembled with support board of two stands. The capillary tube was installed up to 200 mm on top of the horizontal surface of specimen or 200 mm above the midlevel of vertical surfaces to create pressure on the surface of mortar. All apparatus were washed in a soap solution to minimize the surface tension. A circular cap with a surface area of at least 5000 mm2 was clamped tightly onto the mortar surface and filled with distill water from a reservoir. The other end of the tube was connected to a horizontal, calibrated glass capillary tube. RESULTS AND DISCUSSION Figure 3 and 4 show the ISAT rate for mortar with 0.3w/c and 0.4w/c respectively. Both graphs show ISAT rate gradually decreased with time as sample was becoming saturated with water. It can also be seen that the ISAT rate for 0.4 w/c mortar is lower than 0.3 w/c mortar. This means that 0.3 w/c mortar has more capillary or void compared to 0.4 w/c mortar due to due to lack of water for full hydration. Figure 3: Initial Surface Absorption Rate of 0.3 Figure 4: Initial Surface Absorption Rate of 0.4 w/c w/c 97

Figure 5: Initial Surface Absorption Rate for different combination of SBR and FA modified mortar of 0.3 w/c Data were presented in terms of ISAT rate in 0.01 ml/m2/ s per unit versus time in minutes. The data were taken every 15 minutes in order to see the pattern starting from 1 minute, 15 minutes, 30 minutes, 45 minutes, and 60 minutes. Based on Figure 5, 0.3 w/c mortar has the highest ISAT rate meanwhile modified mortar of 10% SBR and 10% FA of 0.3w/c has lowest ISAT rate. This shows that the best combination of both polymer and pozzolan in modified mortar was the one with highest SBR and lowest FA content. From the graph, it is also shown that the ISAT rate for specimens were decreasing from specimen that have lower SBR (5 %) and higher FA (30 %). Besides, ISAT rate decreased with time for all specimens. These entire patterns can also be observed in Figure 6 for all 0.4 w/c samples. The combination of polymer and pozzolan has improved the 0.3 mortar by making it water resistance. Polymer block the pores and the presence of FA caused pozzolanic activity in which helped decrease the permeability by reducing bleed channels, capillary channels and void spaces inside the mortar. Figure 6: Initial Surface Absorption Rate for mortar of 0.4 w/c with different combination of SBR and FA . 98

CONCLUSION Modified mortar showed better water absorption resistance compared to unmodified mortar. The specimen with higher addition of SBR and lowest replacement of FA gave better resistance against water absorption compared to the other combination. As a conclusion, higher addition of SBR into the mortar will improve the permeability of mortar. However lower amount of FA was favorable since the amount of water available for hydration during curing period increases as the amount increases. It can be concluded based on this study that high percentage of polymer addition and low percentage of pozzolanic cement replacement in mortar can enhance its resistance to water absorption. ACKNOWLEDGMENT The authors wish to acknowledge University Malaysia Sarawak for supporting this work under the FRGS/03(04)/772/2010(53) grant. REFERENCES [1] Bhattacharjee, B. (2008). Module 7 Lecture -1: Durability of Concrete. Department of Civil Engineering, IIT Delhi [2] Dhir, R. K, McCarthy, M. J. & Newlands, M. D. (1997) Challenges In Designing Concrete Durability: A Sustainable Approach. Concrete Technology Unit. University of Dundee, UK [3] Ohama, Y. (1997). Recent Progress In Concrete - Polymer Composites. [4] Ohama, Y. (1994). Classification of Concrete - Polymer Composities. [5] Boonpradit, P. S. A. N. (2006). Use of Liquid Polymer to Prevent Moisture Loss during Curing and to Improve Watertightness at the Hardening Stage. Thammasat Int. J. Sc. Tech. 11(2): 41- 46. [6] Radonjanin, R. (1998). Experimental Research On Polymer Modified Concrete. ACI Material Journal 95. [7] Z.Su, K. S., J.M.J.M Bijen, H.M. Jennings, & A.L.A. Fraaij (1996). The Evolution of Microsructure in Styrene Acrylate for Polymer-Modified Cement Pastes at Early Stage of Cement Hydration. Advanced Cement Based Material 3: 87-93 [8] Mehta, P.K. (n.d.). High – Performance, High – Volume Fly Ash Concrete For Sustainable Development. International Workshop on Sustainable Development and Concrete Technology. 99

CHAPTER 15 THE INFLUENCE OF FINELY GROUND MINERAL ADMIXTURE (FGMA) ON EFFLORESCENCE Ong Ming Wei and Norsuzailina Mohamed Sutan* ABSTRACT Efflorescence phenomenon on concrete is not new and found in the form of white deposits on surfaces of concrete. Incorporation of Finely Ground Mineral Admixture (FGMA) in concrete to prevent occurrence of efflorescence is based on reduction of portlandite, densified microstructure and thus enhanced watertightness. The magnitude of efflorescence in term of percentage of calcium carbonate formation of FGMA modified mortar were evaluated at water-cement ratio of 0.3, 0.4 and 0.5 with 10%, 20%, and 30% of cement replacement by weight. The samples were tested with chemical analysis at 7, 14, 21, 28, 60 and 90 days. The FGMA additions into mortar were comparing with ordinary mortar to evaluate enhanced performance of FGMA modified mortar toward efflorescence. The results of this experiment showed that addition of FGMA into mortar caused less formation of calcium carbonate as partial replacement of cement with certain w/c ratio and percentage of cement replacement. Keywords: Efflorescence, Fly Ash, Silica Fume, Calcium Hydroxide, Calcium Carbonate INTRODUCTION Research and development on enhancing cement based system is done progressively through past decades especially on aspect of durability. The utilization of FGMA can contribute to engineering benefits, economic benefits and ecological benefits [1]. The efflorescence is not new issues in construction industry and concluded as aesthetic problems in durability aspect. It caused unpleasant aesthetic for the construction industry especially precast concrete manufacturer and concrete or mortar for decorative purpose [2]. Efflorescence is the phenomenon of salt deposits formation, usually white, on or near surface of cement product and cause changes in appearance [3]. The salts deposit usually is calcium carbonate which is cause by transport of dissolve calcium hydroxide through surface and react with carbon dioxide and thus evaporate to become salt deposits [4].The mechanism of efflorescence formation is by dissolve calcium hydroxide at surface and reacts with carbon dioxide to form calcium carbonate. Equation 1 shows the chemical reaction formation of calcium carbonate. Ca(OH)2 + CO2 +H2O → CaCO3 + 2H2O (1) It is not water in concrete migrate to surface and entrain the calcium hydroxide. It is the calcium hydroxide diffuses up through the water-filled capillary system of the concrete to the surface and react accordance as shown in Equation 1[5]. *Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia. Email: [email protected] 100

To effectively avoid efflorescence, it can reduce the migration of calcium ions to concrete surface, reducing size of capillary and make carbonation take place below surface of concrete [6].FGMA (e.g. fly ash and silica fume) is well known of improving concrete properties in term of workability in fresh state and enhancing in strength and impermeable in hardened state [7],[8]. Fly ash and silica fume enhances concrete properties by physical mechanisms and chemical mechanisms such as reduced bleeding, provision of nucleation sites, denser packing density of solid particles and form additional calcium-silicate hydrate (CSH) [9],[10]. The purpose of the present investigation is to develop modified cement system with enhanced mechanical properties and reduce tendency of efflorescence phenomenon by introducing FGMA to alter the properties of cement based system. This research was carried out to determine influence of fly ash and silica fume on efflorescence tendency of mortar. The efficiency of FGMA incorporation in mortar against efflorescence is evaluated based on the percentage of CaCO3 formation compare to Ordinary Portland mortar. MATERIALS AND METHODS MATERIALS AND MIX PROPORTIONS Cement used in this experiment was Ordinary Portland Cement (OPC), produced by local manufacturer, Cahaya Mata Sarawak (CMS) with specific gravity of 3.16. The fine aggregate used is river sand (dry condition) with specific gravity of 2.6. Tap water was used throughout the experiment. FGMA used is fly ash and silica fume in powdered form as cement replacement (by wt) of 10%, 20% and 30%. Table 1 shows the mix proportion of mortar mixtures with 10%, 20% and 30% of FGMA to cement ratio at w/c ratio of 0.3, 0.4 and 0.5. These mortar mixes were conducted with chemical analysis and evaluated in term of percentage of calcium carbonate formation in comparison to the ordinary mortar as the control. Table 1: Mix Proportion for Mortar Samples FGMA Replacement w/c 0.3 w/c 0.4 w/c 0.5 0% 1:0.3:1.67:0 1:0.4:1.67:0 1:0.5:1.67:0 10 % 1:0.3:1.67:0.1 1:0.4:1.67:0.1 1:0.5:1.67:0.1 20 % 1:0.3:1.67:0.2 1:0.4:1.67:0.2 1:0.5:1.67:0.2 30 % 1:0.3:1.67:0.3 1:0.4:1.67:0.3 1:0.5:1.67:0.3 CURING CONDITION The mortar specimen is demolded after 24 hours of casting and immediately added with 10mm height of water at the surface. The added surface water is then left to evaporation or absorbed by specimens. The curing condition is wet curing and exposed to laboratory environment with relative humidity of 85% and temperature of 28⁰C. All the specimens were subjected to tests at the end of curing period of 7, 14, 21, 28, 60 and 90th days after demolding. CHEMICAL ANALYSIS All mortar mixes were conducted with chemical analysis with respect to its predetermined curing period. White deposits were observed for the samples after certain period. The surfaces of samples were then grinding into powdered form. Hydrochloric Acid is added to the sample in powdered form to determine the percentage of calcium carbonate in tested amount of powdered sample. The percentage of calcium carbonate obtained was representing the amount of calcium carbonate formed at surface of mortar. 101

Chemical analysis was proposed as it gives a reliable quantitative measure of the percentage of calcium carbonate (CaCO3) produce by efflorescence. The CaCO 3 may form beneath the surface of concrete/ mortar. Hence, those tests to evaluate efflorescence magnitude by concrete brightness test measures may not be that accurate due to ignoring the surface beneath CaCO3 [6]. Therefore, this method of chemical analysis is preferable to be used to evaluate the percentage of CaCO 3 formation in a given sample and comparable with other type of mortar samples. RESULTS AND DISCUSSION RESULTS Figure 1: % of CaCO3 versus curing periods of mortar mix at w/c 0.3 Refer to Figure 1, it can found that most of the mortar sample exhibit higher tendency of efflorescence in term of calcium carbonate at earlier time except for FA 10% composite specimen. Most of the mortar sample exhibit similar trend except for mortar with 10% fly ash replacement by reduction of calcium carbonate percentage as hydration process continues. Except of mortar with 10% fly ash replacement, others mortar generally exhibit poorer results in term of higher percentage of calcium carbonate formation compared to control mortar, w/c 0.3. For silica fume modified mortar, none of the mortar incorporate silica fume gives enhancement toward efflorescence. Based on Figure 1, fly ash replacement of 10% shows lesser formation of calcium carbonate compared to control mortar, w/c 0.3. It can be concluded that maximum replacement of fly ash is 10% at w/c 0.3. 102

Figure 2: % of CaCO3 versus curing periods of mortar mix at w/c 0.4 By referring to Figure 2, mortar samples with replacement of 20% FA gives most favorable result for 28 and 90 days curing period compare to other types of mortar samples at w/c ratio of 0.4 in term of percentage of CaCO3 formation. However, for mortar sample with w/c ratio of 0.4, the poorest performance is mortar with 30% SF, 30% FA and 10% FA for curing period of 28 days in descending order. However, SF 20% mortar samples exhibit strange trend of percentage of efflorescence formation and gives very high percentage of CaCO3 at later age. The improved performance of mortar samples after replacement by FA and SF is mortar sample with FA 20% and SF 10% at w/c 0.4. However, the mortar with SF 10% almost having same percentage of calcium carbonate formation with control mortar at w/c ratio of 0.4. It is concluded that for mortar sets of w/c ratio of 0.4, the only improvement in resistance toward efflorescence is mortar with replacement of 20% FA. Figure 3: % of CaCO3 versus curing periods of mortar mix at w/c 0.5 By referring to Figure 3, the poorest performance is mortar sample with 30% SF for 28 and 90 days. It is also observed that mortar samples with SF of 20% and 30% generally give high percentage of calcium carbonate for mortar sets at w/c ratio of 0.5 except mortar with 20% SF which gives lowest percentage of CaCO3 formation at the first 7 days of curing. 103

The best performance of efflorescence resistance is mortar sample with 20% FA at w/c ratio of 0.5 at later age. Mortar sample with 10% FA and 10% SF also gives improvement compare to control mortar sample but it is not having significant improvement. It is found that, mortar samples with FGMA replacement at 30% do not enhance resistance toward efflorescence but worsen it. DISCUSSION I. The expected outcome of fly ash and silica fume addition in concrete is reduction in porosity and has better durability properties due to densified of interfacial transition zone. This may be explain by reduction in amount of calcium hydroxide as pozzolanic reaction by fly ash or silica fume particles to form additional calcium silicate hydrate gel which contribute to reduction in porosity, densified of interfacial transition zone [11],[13],[14]. II. This is out of the expected results whereas cement replacement by FA or SF generally should improve the resistance toward efflorescence by enhancing microstructure and reduce permeability of mortar [12]. III. The optimum percentage replacement of FGMA in mortar for minimum tendency and severity of efflorescence is not clear from this experiment as it varies with water-cementitious ratio. The optimum percentage replacement at w/c 0.3 for fly ash is 20% but only at earlier time. In case of w/c 0.4, there is only mortar sample with 20 % fly ash gives enhancement in properties against efflorescence. Whereby, only mortar sample with 20% fly ash and 10% silica fume gives less severity of efflorescence formation at w/c 0.5. The improvement of mortar sample at same w/c with lesser CaCO 3 formation than control mortar is only for mortar sets at w/c 0.4 and w/c 0.5. IV. Incorporation of FGMA increased the specific surface area of mortar and deduction in mix water due to mix water absorption on dry surface of FGMA. Especially for silica fume modified mortar, increase in water demand is significant due to high fineness of silica fume and tends to have large specific surface area [11], [13]. In this experiment, no superplasticizer was introduced for fly ash and silica fume modified mortar. V. It can be concluded that the water-cement ratio does have significant effects on FGMA modified mortar against efflorescence. Apparently, the higher the content of silica fume or fly ash added and more cement is replaced; due to fixed water-cement ratio, more water is deducted from the specimen and not only that, the fly ash and silica fume in dry powder tend to absorb a certain amount of remaining water to form into cementitious properties. Thus, without sufficient of mix water, higher percentage of FGMA replacement would not gives improvement in properties of mortar due to insufficient mix water for hydration process and pozzolanic reaction to develop. VI. Hence, the sample becomes absolutely dry and porous surface of mortar is formed. This porous structure of mortar samples in general having high permeability and thus eases the transport of calcium hydroxide or fluid leaching out or ingress thru mortar surface. As consequence, more dissolved calcium hydroxide leaches out to surface to react with carbon dioxide to form calcium carbonate and on the other hand, more water is capable ingress thru the porous surface due to large capillary pores. VII. The Scanning Electron Microscope (SEM) image of the control mortar, fly ash modified mortar and silica fume modified mortar in Figure 4 and Figure 5 shows significant improvement in the microstructure in terms of pores and lesser calcium hydroxide is observed for mortar with FGMA addition as confirmed by previous findings 104

(a) (b) Figure 4: Scanning Electron Microscope (SEM) of control mix (a) and mortar with 20% fly ash (b) at w/c 0.5 Figure 5: Scanning Electron Microscope (SEM) of mortar with 30% silica fume at w/c 0.4 CONCLUSION The incorporation of FGMA into mortar can reduce the severity of efflorescence by improving the properties of mortar.The employment of fly ash with cement replacement of 10% and 20% is effectively reduced severity of efflorescence whereas 30% cement replacement is not favourable in resistance to efflorescence compare to control mix. However, it is not enhanced efflorescence resistance when w/c below 0.4 for fly ash modified mortar. The addition of silica fume as cement replacement does not enhance the resistance against efflorescence compare to control mix for w/c below than 0.5 and as well as cement replacement rate more than 10%. It is obvious silica fume modified mortar require higher w/c ratio than fly ash modified mortar due to its high fineness particles. The poor performance can conclude is lack of appropriate water content for pozzolanic reaction to develop and FGMA acts as filler rather than binder. It is recommended to test the mortar sample with higher w/c ratio to determine the true extent of pozzolanic reaction in mitigation of efflorescence. Other durability test like absorption test can use to establish relationship with efflorescence formation. 105

ACKNOWLEDGMENT The authors wish to acknowledge University Malaysia Sarawak for supporting this work under the FRGS/03(04)/772/2010(53) grant. REFERENCES [1] V. M. Malhotra, and P. Kumar Mehta, “Pozzolanic and cementitious materials”, in Advances in Concrete Technology, [2] Vol. 1. Taylor & Francis, London and New York, 2004, pp. 4-5. [3] T. Abeile, A. Keller, and R. Zurbriggen, “Efflorescence mechanism of formation and ways to prevent, Elotex AG,Swizerland. [4] Cement Concrete & Aggregates Australia, “Efflorescence”, Cement Concrete & Aggregates Australia, St Leonards,N.S.W., Australia [5] J. Bensted, “Efflorescence – a visual problem on buildings”, Construction Repair, vol. 8, no 1, pp. 47-49, 1994 [6] P. Kresse, “Efflorescence – mechanism of occurrence and possibilities of prevention”, Concrete Plant + Precast Technology, vol. 53, pp. 160-168, 1982 [7] P. Kresse, “Coloured concrete and its enemy: efflorescence”, Chemistry and Industry, no. 4, pp. 93-95, 1989 [8] V. M. Malhotra, and P. Kumar Mehta, “Pozzolanic and cementitious materials”, in Advances in Concrete Technology, Vol. 1. Taylor & Francis, London and New York, 2004, pp. 90-91. [9] CUR-report 144, “Fly ash as addition to concrete”, CUR, Gouda, 1992, pp. 39-45. [10]ACI Committee 234 Report, “Guide for the use of silica fume in concrete”, American Concrete Insitute, ACI 234R-06, 2006. [11]ACICommittee 232.2 Report, “Use of fly ash in concrete”, American Concrete Institute, ACI 232.2R96, 1996. [12]H. A. Toutanji and T. El-Korchi, “The influence of silica fume on the compressive strength of cement paste and mortar”, Cement and Concrete Research, Vol. 25, No. 7, pp. 1591-1602, 1995 [13]S. F. U. Ahmed, Y. Ohama and K. Demura, “ Comparison of mechanical properties and durability of mortar modified by silica fume and finely ground blast furnace slag”, Journal of Civil Engineering, vol. 27, no. 2, 1999 [14]C. F. Christy and D. Tensing, “ Efflect of Class-F fly ash as partial replacement with cement and fine aggregate in mortar”, Indian Journal of Engineering & Materials Sciences, vol. 17, pp. 140- 144, 2010 [15]D. P. Bentz and P. E. Stutzman, “Evolution of porosity and calcium hydroxide in laboratory concretes containing silica fume”, Cement and Concrete Research, Vol. 24, no. 6, pp. 1044- 1050, 1994 106

CHAPTER 16 CHARACTERIZATION OF EARLY POZZOLANIC REACTION OF CALCIUM HYDROXIDE AND CALCIUM SILICATE HYDRATE FOR NANOSILICA MODIFIED CEMENT PASTE J.Z. Chong, N.M. Sutan* and I. Yakub ABSTRACT This study intends to investigate the early pozzolanic reaction of Nanosilica (nS) modified cement paste (NMCP) by the characterization technique of Calcium Hydroxide (CH) and Calcium Silicate Hydrate (C-S-H ) using Fourier Transform Infrared Spectroscopy (FT-IR). NMCP samples were prepared with water-binder ratio of 0.50. nS of 5-15nm particle size were used as 1%, 3% ,5% ,7% and 10% replacement of cement by weight. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared and tested at day 1,7,21 and 28. It was found that characterization technique used were able to give satisfactory qualitative indication of pozzolanic reactivity of NMCP by the presence and absence of C-S-H and C-H that can indicate which replacement has higher pozzolanicity. NMCP exhibited a higher pozzolanic reactivity compare to conventional cement paste by which cement performance was enhanced. Keywords: Nanosilica, CH, C-S-H, FT-IR, Cement Paste INTRODUCTION Concrete is the most widely used material in construction industry and consumes almost the total 90% cement production in the world. The consumption of large quantity of cement causes greenhouse effects to environment producing global warming issues. This is due to the emission of significant amount of carbon dioxide, CO 2 as by-product from the combustion of fuel fossil and calcination of limestone during its production. As much as 1.25 tonnes of CO2 is emitted to produce every ton of cement and the CO2 emission from cement industry is responsible 5% for the total global gas emissions of CO2 [1]. One of the alternatives to reduce the amount of CO2 emitted is reducing the amount of cement used in cement based material by partial replaced it with supplementary cementitious materials such as fly ash, ground granulated blast furnace slag, silica fume and natural pozzolans. *Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia. Email: [email protected] 107

Introduction of nanotechnology in cement industry has the potential to reduce the amount of CO2 emissions by partial replacement of cement in cement based material with nanoparticles. Previous research found that remarkable improvements in the mechanical and chemical properties of cementitious materials can be observed with incorporation of nanomaterial such as SiO2, ZnO2, Al2O3, TiO2, carbon nanotubes, nanoclays, carbon nanofibers and other nanomaterial. In the recent development, the addition of nanosilica (nS) has attracted increasing interest because of its filling effect which improve the particle size distribution thus reduced the porosity and permeability of cement based materials in effect increase durability and sustainability [2]. The aspect that makes nS an excellent cement replacement material is due to its high pozzolanicity resulted in enhanced durability of cement based material. It has proven to be an excellent admixture for cement to improve strength and durability and decrease permeability [2]. Besides that, nS is also typically a highly effective pozzolanic material and addition of nS into cement paste will improved the microstructure of the paste and reduced calcium leaching as nS reacts with CH and form additional C‐S‐H gel [3]. Highly pozzolanicity of nS particles is due to its size which is typically 5 - 100 nanometers (nm) with specific surface area (SSA) in the 25 - 50 m2/g range and its fine vitreous particles approximately 1000 times smaller than the average cement particles. According to ASTM C125 pozzolan is a siliceous and aluminous material which itself possesses little or no cementitious value but which will in finely divided form in the presence of moisture, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties [4]. Pozzolanic reaction in cement system is the reaction of silica with Calcium Hydroxide (CH) formed during the hydration of the OPC. It produces additional Calcium Silicate Hydrate (C-S-H) which is the main constituent for the strength and density in the harden binder paste. The pozzolanic activity includes two parameters; the maximum amount of lime (CaOH2) that pozzolan can react to and the rate of reaction. The rate of the pozzolanic activity is related to the surface area of pozzolan particles where higher surface area of pozzolan particle gives higher pozzolanic reactivity. Larsen investigated and analyzed pozzolanic reaction by monitoring the production of CH based on changing cement and admixture [5]. Through his findings in 1961, it was determined that the concentration of CH, commonly known as Portlandite, can be used to quantify the C-S-H formed in the same specimen. There should be a decrease in the amount of Portlandite in a given specimen based on addition of silica and maximum nominal size of the graded silica due the pozzolanic reaction [5].The objective of this study is to investigate the early pozzolanicity of nS modified cement paste (NMCP) by monitoring the presence of crystalline form CH and its subsequent reduction in abundance with time as the pozzolanic proceeds to form more amorphous C-S-H gel. MATERIALS AND METHOD MATERIALS AND SAMPLE PREPARATION Nanosilica (nS) used in this study was Silicon Dioxide Nanopowder (CAS 14808-60-7) of 5- 15nm particle size (BET) with 99.5% silica purchased from Sigma-Aldrich, Germany. Cement used was Ordinary Portland Cement (OPC) (ASTM Type 1 recognized by ASTM C150) manufactured by Cahaya Mata Sarawak Cement Sdn. Bhd (CMS).The chemical and mineralogical characteristics of the OPC are given in Figure 1. NMCP samples were prepared with water-to-cement ratio (w/c) of 0.5 and 1%, 3%, 5%, 7% and 10% cement replacements by weight. Universal Containers 30ml (28 mm diameter , 85mm height) were used as moulds. All samples were cured in the concrete laboratory at daily room temperature (T) and relative humidity (RH) in the range of 18-28oC and 65-90%, respectively. Powdered samples were prepared from small samples collected from the demoulded samples. 108

Figure 1: Chemical Composition of OPC METHOD Early pozzolanic reaction of Nanosilica Modified Cement Paste (NMCP) samples was analysed using characterization technique namely Fourier Transform Infrared Spectroscopy (FT-IR) at day 28. Test was performed on all samples with a Shimadzu Fourier Transform Infrared Spectroscopy (FT- IR) 81001 Spectrophotometer. The spectrum measurement method applied in this FT-IR study is Attenuated Total Reflection (ATR) method. Transmission infrared spectrum of each sample was recorded using a Fourier Transform Infrared Spectrophotometer (IRAffinity-1) in the region of 400 to 4000 cm-1 with 2.0 cm-1 resolution. RESULTS AND DISCUSSION Cement contains several chemical components with various functional groups, such as SiO2, SO4, H2O, OH, and CO3, which are infrared active. The absorbed infrared wavelengths of the functional groups are dependent on the chemical surroundings of the group. Hence, there will be shifts of the absorption bands of the functional groups [6]. The main products of hydration, calcium hydroxysilicate of the C2SH2 and CSH (β) types can be detected in the IR spectra from the ν3 (Si-O) absorption band at 965–975 cm-1 and calcium hydroxide (CH) from the v (OH) absorption band at 3640 cm-1 [7]. ANALYSIS SAMPLE WITHIN THE SAME PERCENTAGES OF NS REPLACEMENT WITH AGE DEVELOPMENT Figure 2.1 to 2.5 showed the FT-IR spectrum for different percentages of nS replacement from day 1 to 28. When the hydration progresses from day 1 to 28, the CH band around 3630 cm-1 for 1%, 3%, and 5% NMCP shown a decrease in intensity (as shown in Figure 2.1B, 2.2B and 2.3B) which indicated that the CH contents were reduced with the age development. The trend of CH development is opposite if compared with control set. 109

Figure 2.1A: C-S-H band of cement paste Figure 2.1B: CH band of cement paste sample sample with 1% NMCP at (A) 1 day (B) 7 days with 1% NMCP at (A) 1 day (B) 7 days (C) 21 (C) 21 days and (D) 28 days days and (D) 28 days Figure 2.2A: C-S-H band of cement paste Figure 2.2B: CH band of cement paste sample sample with 3% NMCP at (A) 1 day (B) 7 days with 3% NMCP at (A) 1 day (B) 7 days (C) 21 (C) 21 days and (D) 28 days days and (D) 28 days Figure 2.3A: C-S-H band of cement paste Figure 2.3B: CH band of cement paste sample sample with 5% NMCP at (A) 1 day (B) 7 days with 5% NMCP at (A) 1 day (B) 7 days (C) 21 (C) 21 days and (D) 28 days days and (D) 28 days 110

Figure 2.4A: C-S-H band of cement paste Figure 2.4B: CH band of cement paste sample sample with 7% NMCP at (A) 1 day (B) 7 days with 7% NMCP at (A) 1 day (B) 7 days (C) 21 (C) 21 days and (D) 28 days days and (D) 28 days Figure 2.5A: C-S-H band of cement paste Figure 2.5B: CH band of cement paste sample sample with 10% NMCP at (A) 1 day (B) 7 days with 10% NMCP at (A) 1 day (B) 7 days (C) 21 (C) 21 days and (D) 28 days days and (D) 28 days This phenomenon is due to the pozzolanic reaction of nS where nS reacts with CH to produce additional C-S-H. The CH band for 7% and 10% NMCP samples have shown an increasing intensity (as shown in Figure 2.4B and 2.5B). The increasing intensity of the CH band indicated that there was no reduction of the CH content in the sample. Therefore, pozzolanic reactivity did not occur for 7% and 10% NCMP. This may be due to the agglomeration of nS that prevented its participation in hydration reaction. The intensity of the C-S-H band increased as hydration progresses for all samples (as shown in figure 2.1A-2.5A). The C-S-H content for sample with 1%, 3% and 5% NMCP were more than 7% and 10% NMCP. This was due to the pozzolanic reactivity that produced an additional C-S-H that was purely from the cement hydration. As a summary, 1%, 3% and 5% NMCP showed pozzolanic reactivity and produced additional C-S-H to the cement sample. Meanwhile 7% and 10% NMCP did not show pozzolanic reactivity due to the agglomeration of nS. 111

COMPARISON BETWEEN SAMPLES WITH DIFFERENT PERCENTAGES OF NS REPLACEMENT AT DAY 28. Figure 2.6 A and B showed comparison between samples with different percentages of nS replacement at day 28. The C-S- H band peak around 970 cm-1 for 1%, 3% and 5% NMCP samples (as shown in Figure 2.6A) have higher intensity compare to the control sample. The increasing trend of the C-S-H band indicated that there were more C-S-H produced in NMCP samples due to the pozzolanic reactivity of nS. The C-S-H band had shown the strongest intensity for the cement paste sample in 3% NMCP since it menifested the deepest and steepest downward peak for the C-S-H band as shown in Figure 2.6A. The 7% and 10% NMCP samples had low intensity in C-S-H band compare to the control sample. These indicated that there was lesser C-S-H produced in 7% and 10% NMCP sample. It can be concluded that, 3% was the optimum dosage for 5-15nm NMCP. Figure 2.6A: C-S-H band around 970 cm-1 for Figure 2.6B: CH band around 970 cm-1 for (A) (A) Control (B) 1% (C) 3% (D) 5% (E) 7% and Control (B) 1% (C) 3% (D) 5% (E) 7% and (F) (F) 10% NMCP sample at 28 day 10% NMCP sample at 28 day CONCLUSION In conclusion, 1%, 3% and 5% NMCP samples have shown pozzolanic reactivity. The CH content in 1%, 3% and 5% NMCP samples decreased as the hydration progressed from day 1 day to day 28. The reduction of the CH is due to the pozzolanic reaction between nS and CH content in hydrated cement paste that produced additional C-S-H gel. Meanhile 7% and 10% NMCP samples did not show pozzolanic reactivity due to agglomeration of nS that did not permit the nS to join the hydration process. Analysis done between samples with different percentages of nS replacement had found that the optimum dosage of nS by comparing the C-S-H content was 3%. Therefore, 3% NMCP was the optimum and the most effective percentage replacement that produced pozzolanic reactivity that can improve the microstructure of the cement system. ACKNOWLEDGMENT The research work reported in this paper has been funded by University Malaysia Sarawak (SGS/03(S113)/894/2012(26)). 112

REFERENCES [1] Malhotra, V.M, “Making Concrete Greener with Fly Ash”, Concrete International, Vol.21, No.5, May 1999, pp.61-66 [2] Sololev, K., (2009). Engineering of Silica nano particles for optimal performance in nano cement based materials: Nano Technology in Construction, Proceedings of the NICOM3, Prague, 139- 148. [3] V . Ershadi; T. Ebadi; A.R Rabano; L. Ershadi; H. Soltanian. (2011). The Effect of Nanosilica on Cement Matrix Permeability in Oil Well to Decrease the Pollution of Receptive Environment. International Journal of Environmental Science and Development vol. 2. [4] American Society for Testing and Material (ASTM) C-125, Standard terminology relating to concrete and concrete aggregates. [5] Larsen, G. “Microscopic Point Measuring: A Quantitative Petrographic Method of Determining the Ca(OH)2 Content of the Cement Paste in Concrete”. Magazine of Concrete Research. 1961. [6] Ylemen, E.R., (2013) Early Hydration of Portland Cement – An Infrared Spectroscopy Perspective Complemented by Calorimeter and Scanning Electron Microscopy. Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden 2013. [7] Conjeand, M., and Boyer, H. (1980), Some Possibilities of Raman Microprobe in Cement Chemistry, Cem. Concr. Res., 10:61. 113

CHAPTER 17 STRENGTH CHARACTERISTICS OF MORTAR CONTAINING DIFFERENT SIZES GLASS POWDER N. Tamanna, N. Mohamed Sutan*, I. Yakub and D. T. C. Lee ABSTRACT A greater portion of nonrecyclable waste glass is accumulated on landfills creating a serious environmental problem. Recent studies have been carried out to utilize the waste glass in construction as partial replacement of cement. This paper investigates the fineness properties of four sizes glass particles and strength characteristics of mortar in which cement is partially replaced with glass powder in the replacement level with 10%, 20%, 30% and 40%. Mortar cubes containing with varying particle sizes in the ranges of 212 µm, 75 µm, 63-38 µm and lower than 38 µm and in a water to cement ratio 0f 0.50 and 0.45 have been prepared. Room temperature and relative humidity have been maintained 32ºC and 90% respectively during the curing process. Replacement of 10% cement with glass powder reveals the higher compressive strength at 28days than other levels of replacement. The reduction in compressive strength increases with the level of cement replacement. Keywords: Waste glass powder, cement replacement, compressive strength, 28days. INTRODUCTION The generation of waste materials has increased according to the rapid growth of industry and population explosion. The greater portion of these materials do not decompose by itself accumulated on the landfill areas, will remain in the environment for many years, thereby contributing to the environmental problems. The utilization of waste material in construction industries has been increased significantly, in the recent years owing to the short or long term properties of concrete without compromising concrete performance [1]. Waste glass is one such material, which is encouraged for recycling. Theoretically, glass is a 100% recyclable material; it can be indefinitely recycled without any loss of quality [2]. Nevertheless, the recycling rate of waste glass is quite low compared to the other solid wastes because of expensive cleaning and color sorting cost [3]. Environmental regulations and deficiency of landfill space are also encouraging the use of waste glass in concrete production.Several studies were carried out on the use of waste glass as an aggregate for concrete production in the 1960s. The first practice was conducted by Schmidt and Saia [4], 1963 to the use of glass chips to produced architectural exposed aggregate for concrete. The effect on mechanical properties of using waste glass in concrete had been studied by many other researchers, including Johnston (1974), Figg (1981)[5]-[6]. *Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia. Email: [email protected] 114

Owing to high disposal cost of waste glass and environmental regulation the use of glass as cement concrete aggregates has attracted again under attention of the researchers in the last 20 years [7]- [13]. This aggregate was applied in road construction and also used for production of glass tiles, wall panels, bricks, glass fibre, agriculture fertilizer landscaping reflective beads and tableware [14]. Alkali silica reaction considered as an extreme barrier that restrains the waste glass utilization [15]. The feasibility of using waste glass as cement replacement was 1st introduced by Patttengil and Shutt [16]. It was examined that if the glass was powder to a particle size of 300 µm or smaller, the ASR would not be harmful in concrete production [17]. It can act as a pozzolanic material to react with portlandite in hydrated cement to form C-S-H in increasing strength and durability of concrete because of the high silica content in glass powder [18]-[23]. This paper deals the strength characteristics of mortar containing different sizes of glass powder with different water to cement ratio. Cement is replaced by glass powder at rates varying from 10 to 40 percent. Particle size distribution, morphology and compressive strength are studied and made a comparison with control samples. MATERIALS AND METHODS RAW MATERIALS: PORTLAND CEMENT Ordinary Portland Cement (OPC) ASTM Type 1 which is manufactured by Cahaya Mata Sarawak Cement Sdn. Bhd (CMS) was used throughout the research, and it confirmed the quality requirements specified in the Malaysian Standard MS 522: Part 1: 1989 Specifications for OPC. The relevant physical properties and chemical composition of the OPC ASTM Type 1 obtained from the manufacturer are shown in tables 1. Table 1: Physical properties and chemical composition of ordinary Portland cement 115

GLASS POWDER Waste Glass used in this study was soda-lime clear glass bottles collected from recycle center and from the manufacturer. Glass bottles were cleaned with water to remove paper on the surface and to eliminate contaminations. The glass powder is obtained from the grinding machine (Los Angeles Abrasion Machine) in civil engineering laboratory and subjected to mechanical sieve analysis to get the desired particle size. To study particle size effect, four different sizes are used.  Glass Type 1: Glass powder having particles passing a #70 sieve (212 micron) and retained on a #100 sieve (150 micron).  Glass Type 2: Glass powder having particles passing a 100 sieve (150 micron) and retained on a #200 sieve (75 micron).  Glass Type 3: Glass powder having particles passing a #200 sieve (75 micron) and retained on a #400 sieve (38 micron).  Glass Type 4: Glass powder having particles passing a #400 sieve (38 micron). SAND AND WATER Sand used as a fine aggregate was obtained from Civil Engineering Laboratory, UNIMAS which is free from organic or chemical substance and passing through ASTM sieve no.16 aperture 1.18mm sieve. Water used as mixing water was collected from laboratory. PARTICLE SIZE DISTRIBUTION The particle size distribution of cement and four sizes glass powder was measured by using CILAS 1090 Laser Particle Size Analyzer. SCANNING ELECTRON MICROSCOPE In this research, SEM was carried out to analyze the particle size and shape of waste glass powder using Analytical Scanning Electron Microscope (JSM-6390LA) supplied by JEOL Company Limited, Tokyo, Japan. Waste glass powders were spread on a double sided adhesive conductive carbon tape to prevent scattering of loose particles. Then the samples were coated with platinum in argon gas atmosphere at a high vacuum of 30MPa in order to provide the samples electrically conductive in nature. The photographs, captured at a magnitude of 200 are presented in result and discussion section. COMPRESSIVE STRENGTH TEST Compressive strength of four type glass powder as cement replacement was investigated in the concrete laboratory. Mortar samples were prepared by glass powder containing 212 µm and 75 µm, 75-38 µm, <38 µm with water to cement ratio 0.50 and 0.45 respectively. Type 1 glass powder was replaced in the level of 10%, 20% & 30% by weight casted into 150mm X 150mm X 150mm and type 2,3,4 glass powder were replaced in the level of 10%, 20%, 30% & 40% by weight casted into 50mm X 50mm X 50mm cube. All the samples were cured in the concrete laboratory with average temperature of 32˚C and relative humidity of 90%. 116

RESULTS AND DISCUSSION MORPHOLOGY OF GLASS PARTICLE UNDER SCANNING ELECTRON MICROSCOPE Scanning electron microscope shows the typical shape of four different sizes of glass powder. Glass powder type 1 which represents 212-150 µm exhibit angular shapes but not in uniform sizes. A large number of fine particles present in 212 µm glass powder where as angular flaky particles consist in both 75 µm and 38 µm glass powder. Moreover, 38 µm glass powder shows more angular shapes than glass powder type 1 and 2 as shown in figure1 (c). Glass powder which is lower than 38 µm contains homogeneous angular particles with a sharp edge than any other glass powders, shown in figure 1 (d) that gives similar particle size distribution as Portland cement. (a) (b) (c) (d) Figure 1: Shape of glass powder (a) 212-150µm (b) 150-75 µm (c) 75-38 µm & (d) <38 µm 117

PARTICLE SIZE DISTRIBUTION Figure 2 represents the particle size distribution of ASTM Type 1 portland cement and four sizes glass powder. It can be seen that the glass particles lower than 38 µm exhibit almost the same as that of Portland cement. The mean diameter of Portland cement is 21.19 µm while the particles lower than 38 µm is 21.35 µm. Portland cement contains about 50% of particles lower than 18.13 µm whereas glass powder contains 17.15micron. Only one difference is lower than 38 µm glass particles maintain about 10% of particles nearly 4 µm where Portland cement maintains 2.79 µm. Figure 2: The particle size distribution Glass type 3 (38<X<75) shows a coarser distribution than Portland cement and glass type 4(X<38). The particle size distribution of glass type 3 is very similar in mean diameter but slightly finer than glass type 2(75<X<150).Glass type 3 keeps up about 10% of particles finer than 7.50 µm on the contrary glass type 2 keeps up coarser than 18 µm. Glass type 1 (150<X<212) displays coarser distribution than all type glass and Portland cement wherein 10% of particles contain higher than 64micron but Portland cement does not. COMPRESSIVE STRENGTH TEST OF MORTAR The compressive strength of different batches at 28days is shown in figure 3-4. The compressive strength results of 212 µm glass powder (type 1) are plotted in figure 3. Control sample reveals the highest compressive strength than different percentage of replacement. Mortar containing 10% glass indicates slightly lower strength than control sample which is very close to that mortar containing 20% glass. It can be seen that the reduction in compressive strength increases with the level of cement replacement. The reduction in compressive strength is caused by a reduction in the quantity of cement content available for the hydration process. 118

Figure 3: Compressive strength of 212 µm glass powder The compressive strength results of control sample and type 2, 3, 4 glass powder are plotted in figure 4 at 28days of curing. Glass particles lower than 38 µm exhibits higher compressive strength than the control sample at 10% level of replacement that is confirmed by Khatib et al. [24]. Another 75 µm and 75-38 µm glass particles show comparatively higher value of strength at 10% replacement. Figure 4: Compressive strength of different sizes glass particles with control sample at 28days CONCLUSION In the present study, the glass powder can be used as a partial replacement of cement. Replacement of 10% cement with glass powder reveals the higher compressive strength at 28days than other levels of replacement. Finer size glass particle exhibits comparatively better result than coarser particles. Particle size, finer than 38µm shows almost the same strength as Portland cement, due to the similar particle size distribution. Utilization of waste glass in cement replacement would be beneficial for environment by saving landfill and by reducing CO2 at atmosphere. ACKNOWLEDGMENT The authors acknowledge the research grant provided by Ministry of Education and Universiti Malaysia Sarawak under Fundamental Research Grant (FRGS): FRGS/03(07)/839/2012(73). 119

REFERENCES [1] Patel D., Yadav R.K., Chandak R., “Strength characteristics of pre cast concrete blocks incorporating waste glass powder,”ISCA J. Engineering Sci.,Vol.1(1),68-70,July(2012). [2] Sobolev K., Turker P., Soboleva S., Iscioglu G., 2006, “Utilization of waste glass in ECO-cement: strength properties and microstructural observations,” Waste Management 27 (7), 971–976. [3] Kiang H.T., Hongjian D., “Use of waste glass as sand in mortar: part I-fresh, mechanical and durability properties,” Cement & concrete composites 35(2013)109-117. [4] Schmidt A., Saia W.H.F., (1963), “Alkali-aggregate reaction tests on glass used for exposed aggregate wall panal work,” ACI Mat. J., 60, 1235-1236. [5] Johnson C.D., “Waste glass as coarse aggregate for concrete, J. Test. Eval, 2(5), 1974,pp. 344- 350. [6] Figg J.W., (1981), “Reaction between cement and artificial glass in concrete,” Proc., Conf. on Alkali-aggregate reaction in concrete, Capetown, South Africa. [7] Pollery C, Cramer SM, De La Cruz RV. “Potential for using waste glass in portland cement concrete”. J Mater Civ Eng 1998;10(4): 210–9. [8] Topcu IB, Canbaz M. Properties of concrete containing waste glass. Cem Concr Res 2004;34: 267–74. Van Roode M, Douglas E, Hemmings RT. X-ray diffraction measurement of glass content in fly ashes and slags. Cem Concr Res 1987;17(2):183–97. [9] Meyer C, Baxter S. Use of Recycled Glass for Concrete Masonry Blocks Final Report 97-15. Albany, New York: New York State Energy Research and Development Authority; 1997. [10] Meyer, C., and Baxter, S., 1998. “Use of recycled glass and fly ash for precast concrete”. Rep. NYSERDA 98-18 (4292-IABR- IA-96) to New York State Energy Research and Development Authority, Dept. of Civil Engrg. and Engrg. Mech.,Columbia University, New York. [11] Chen CH, Huang R, Wu JK, Yang CC. “Waste E-glass Particles used in cementitious mixtures”.Cem Concr Res2006; 36:449–56 [12] Byars EA, Morales-Hernandez B, Zhu HY. “Waste glass as concrete aggregate and pozzolan”. Concrete 2004; 38(1):41–4. [13] Bazant ZP, Zi G, Meyer C. “Fracture mechanics of ASR in concretes with waste glass particles of different sizes”. J Eng Mech 2000; 126:226–32. [14] Reindl J. Report by recycling manager, dane County, Department of Public Works, Madison, USA, August 1998. [15] Dhir R.K.,Dyer T.D., Tang A.,and Cui Y., (2004), “Towards maximizing the value and sustainable use of glass,” Concrete for the Construction Industry, 38(1), 38-40. [16] Pattengill M., and Shutt T.C., (1973), “ Use of ground glass as a pozzolan,” Proc., Int. Symp. on Utilization of Waste Glass in Secondary Products, ASCE, Albuquerque, N.M. [17] Meyer C., Baxter S., Jin W. 1996. Alkali-silica reaction in concrete with waste glass as aggregate. in: K.P. [18] Chong (Ed.), Materials for a New Millennium, Proceedings of ASCE Materials Engineering Conference, Washington, D.C., pp. 1388–1394 [19] Shao Y, Lefort T, Moras S. Damian Rodriguez. “ Studies on concrete containing ground waste glass”. Cement and Concrete Research 2000;30(1):91–100. [20] Shayan A, Xu A. “Value-added utilisation of waste glass in concrete”. Cement and Concrete Research 2004; 34(1):81–9. [21] Shi C, Wu Y, Riefler C, Wang H. “Characteristics and pozzolanic reactivity of glass powders”. Cement and Concrete Research 2005;35(5):987–93. [22] Shayan A, Xu A. “Performance of glass powder as a pozzolanic material in concrete: a field trial on concrete slabs”. Cement and Concrete Research 2006;36(3):457–68. [23] Ozkan O, Yuksel I. “Studies on mortars containing waste bottle glass and industrial by-products”. Construction and Building Materials 2008;22(6):1288–98. [24] Taha B, Nounu G. “Properties of concrete contains mixed colour waste recycledglass as sand and cement Replacement”. Construction and Building Materials 2008;22(5):713–20. [25] Khatib J.M., E.M. Negim, H.S. Sohl And N. Chileshe, “Glass powder utilization in concrete production,” European Journal of Applied Sciences 4(4): 173-176,2012. 120

CHAPTER 18 INFLUENCE OF SILICA BASED WASTE MATERIALS ON THE MECHANICAL AND PHYSICAL PROPERTIES OF MORTAR S.I. Balang1, N. Mohamed Sutan1*, I.Yakub1, M.S. Jaafar2 and K.A. Matori2 ABSTRACT This is an investigation on the influence of silica based waste materials namely silica fume (SF) and recycled vase (RV) on the physical and mechanical properties of mortar. Results showed that 15%SF modified mortar achieved the highest strength and lowest water absorption capability compared to Control mortar and other mixtures. The result was confirmed by water absorption capability test for the same mixtures where 15% SF modified mortar was found to absorb the least. Furthermore, combination of 15% SF and 10% RV achieved the lowest water absorption compared to other combinations samples but higher than Control and 15% SF modified mortar. The results of this study indicated that SF is highly pozzolanic material that can be an excellent cement replacement material to produce high- performance concrete. Study on pozzolanc behavior of SF samples subjected to longer hydration time is needed. Further microstructural investigation is needed to confirm the hypothesis on retardation of hydration due to unreactive RV. Keyword: Silica Fume, Recycle Vase, Mortar, Compressive Strength, Water Absorption INTRODUCTION The increased in the utilization of waste materials in construction product came from greater awareness of current and potential potential uses of alternative and recycled materials and wider realization of the environmental benefits accrued. The practice of partially replacing cement in concrete and mortar with waste and other less energy intensive processed materials will contribute environmental protection and sustainable construction in the future. To be qualified as a candidate for cement replacement for concrete or mortar, the waste material must be silica based and very fine. The specific chemical property is the classification of a material to be pozzolanic. Pozzolan is defined as a siliceous material which, in itself, possesses little or no cementing property but which will, in finely divided form and in the presence of moisture, react chemically with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties that can improve concrete and mortar properties [1]. 1*Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan, Sarawak, Malaysia Email: [email protected] 2 Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor,Malaysia. 121

Silica Fume (SF), a byproduct or waste from silicon metal or ferrosilicon alloys production, is a very reactive pozzolan due to its chemical and physical properties which are high in silica and fine particle size, therefore it can be used as partial cement replacement for concrete and mortar production [2-6]. One possible source of pozzolanic waste material is calcined clay [7-9]. Waste calcined clay used in this study, which is derived from recycled vase (RV) in the form of vase powder. Therefore, this study is designed to investigate the combination of waste calcined clay and silica fume as partial cement replacement or only silica fume as partial cement replacement on the improvement of durability properties of concrete modified mortar. The purpose of this research is to investigate the pozzolanic activity of binary binder system of by-product silica fume (SF) as partial cement replacement, and ternary binder of SF and waste calcined clay (RV). The objective of this research is to investigate the mechanical and physical properties of SF, RV modified mortar and their combination on namely their compressive strength and water absorption capability. These properties can be used as an indirect indication of extent of hydration and pozzolanic reactivity of modified mortar. MATERIALS MATERIALS AND METHODS Silica based materials chosen as cement replacement were Silica Fume (SF) according to ASTM C 1240 obtained from Grace Construction and Recycle Vase (RV) or waste vase collected from Naga Emas Ceramic Ind. Sdn. Bhd. The waste vase was cleansed with water to remove dirt and washable contaminants. It was then crushed into smaller pieces and finely grounded to particle size finer than 75 µm. Table 1 shows the chemical composition of OPC and RV obtained from X-ray fluorescence (XRF) analysis. Cement used was Ordinary Portland Cement (OPC) (ASTM Type 1 recognized by ASTM C150) manufactured by Cahaya Mata Sarawak Cement Sdn. Bhd. (CMS). The physical properties and chemical compositions of the OPC and RV are shown in Table 1. SF contains up to 97% SiO2. Water and fine aggregate used in this study were regular tap water and natural river sand, respectively. Glenium was used as superplasticizer (SP). Table 1. Physical properties and chemical composition of OPC and RV 122

SAMPLE PREPARATION FOR COMPRESSIVE STRENGTH (CS) AND WATER ABSORPTION TESTS. The mix proportion for mortar was set at 0.6 binder to sand ratio (b/s) and 0.5 water to binder ratio (w/b) for all specimens that were casted into 150 mm cubes for compressive strength (CS) and water absorption tests. Cement was replaced by SF (10%, 15% and 20%) by weight as binary binder and combination of SF (15%, 20%) and RV (10%, 20% and 30%) by weight as ternary binder. All samples were prepared using the mix proportion as shown in Table 2 and were wet cured in the concrete laboratory at Universiti Malaysia Sarawak for 3, 7, 14, 21, and 28 days. All mixes except Control has an SP dosage of 1 litre per 100kg of binders. Table 2. Mix proportions for all specimens COMPRESSIVE STRENGTH (CS) AND WATER ABSORPTION TESTS. CS and water absorption tests were performed on day 3, 7, 14, 21, and 28 according to BS 1881- 116 (1983) [10] and BS 1881 Part-5 (1983) Part 122, respectively [11]. CS test was used to determine the maximum compressive load that a sample can carry per unit area. Meanwhile water absorption test was used to evaluate water absorption capability of a sample. Both tests give the overall picture of the quality of mortar as it hydrates. Each strength and water absorption values were the average of value of three specimens. Compressive strength for each sample was calculated by using Equation (1)[10]. Meanwhile, water absorption capability for each sample was determined by using Equation 2[11]. 123

RESULTS AND DISCUSSION COMPRESSIVE STRENGTH (CS) TEST Figures 1 and 2 show the compressive strength of SF and SFVC samples compared to Control samples. The increasing compressive strength as cement hydration proceeded from day 3 to 28 in both figures is an expected and established trend [12]. Figure 1 shows 15%SF sample has the highest 28 day comprehensive strength compared to other samples. This is caused by pozzolanic reaction of silica in SF with Calcium Hydroxide ( CH ) from cement hydration that produced more Calcium Silicate Hydrate (C-S-H) that refines the pores and densifies the cement matrix[1-9][12]. Figure 1. Comparison of Compressive Strength between Control and SF modified mortars Figure 2 shows that the combination of 15% SF and 10% RV produced higher strength than other combinations of SF and RV but there was no significant reduction in the compressive strength of these mixtures when compared to the control mortar and 15% SF sample. Figure 2. Comparison of Compressive Strength between Control, SF and SFRV modified mortars 124

RV may not have reactive silica that can produce pozzolanic behaviour. Besides, the presence ofRV may retard the reactivity of SF and cement hydration. Further microstructural investigation need to be done to confirm this hypothesis. WATER ABSORPTION TEST Figure 3 and 4 show the water absorption of SF and SFVC compared to Control samples. From Figure 3,15% SF sample has the lowest water absorption at day 28 which indicated that there are less interconnected capillary voids in the sample [4][5].Figure 4 shows that the combination of 15% SF and 10% RV achieved the lowest water absorption compared to the other combinations samples. However, the absorption is still higher than 15% SF and Control. This is an indication that the unreactive RV may retard hydration [8][9]. The water absorption trend for all samples is the opposites of compressive strength trend and this fact has already been an established trend [12]. Figure 3. Comparison of 24-hr water absorption capability between Control and SF modified mortars CONCLUSIONS The results of this study confirmed that SF is highly pozzolanic material that can be an excellent cement replacement material to produce high-performance concrete. In terms of compressive strength, 15% SF modified mortar achieved the highest strength and lowest water absorption capability compared to Control mortar and other mixtures. The result was confirmed by water absorption capability results for the same mixtures where 15% SF modified mortar absorbed the least. Furthermore, combination of 15% SF and 10% RV achieved the lowest water absorption compared to other combinations samples but higher than Control and 15% SF modified mortar. The results of this study indicated that SF is highly pozzolanic material that can be an excellent cement replacement material to produce high-performance concrete. Study on pozzolanc behavior of SF samples subjected to longer hydration time is needed. Further microstructural investigation is needed to confirm the hypothesis on retardation of hydration due to unreactive RV. ACKNOWLEDGMENT The authors wish to acknowledge Ministry of Education and Universiti Malaysia Sarawak for supporting this work under ERGS/TK04(02)/1011/2013 (08) and RACE/c(1)/1108/2013(16) grants. REFERENCES [1] P. K . Mehta, “ Natural Pozzolans: Supplementary Cementing Materials in Concrete,” CANMET Special Publication 86, pp.1-33 ,1987 [2] M.J. Shannag, “High strength concrete containing natural pozzolan and silica fume,” Cement and 125

Concrete Research, vol 22,no. 6, pp. 399–406,Dec.2000 doi:10.1016/S0958-9465(00)00037-8 [3] Houssam A. Toutanji, “The influence of silica fume on the compressive strength of cement paste and mortar,” Cement and Concrete Research, vol 25,no. 7, pp. 1591–1602, Oct.1995 doi:10.1016/0008-8846(95)00152-3 [4] G.Appa Rao, “Investigations on the performance of silica fume-incorporated cement pastes and mortars,” Cement and Concrete Research, vol 33,no. 11, pp. 1765–1770, Nov.2003 doi:10.1016/S0008-8846(03)00171-6 [5] S. Bhanja, B. Sengupta, “Influence of silica fume on the tensile strength of concrete,” Cement and Concrete Research, vol 35,no. 4, pp. 743–747,Apr.2005 doi:10.1016/j.cemconres.2004.05.024 [6] J. Zelić, D. Rušić, D. Ve za & R. Krstulović, “The role of silica fume in the kinetics and mechanisms during the early stage of cement hydration,”Cement and Concrete Research, vol 30,no. 9, pp. 1655–1662, Oct.2000 doi:10.1016/S0008-8846(00)00374-4 [7] B.B. Sabir, S. Wild & J. Bai, “Metakaolin and calcined clays as pozzolans for concrete : a review,” Cement and Concrete Research, vol 23,no. 6, pp. 441–454, Dec.2001 doi:10.1016/S0958- 9465(00)00092-5 [8] K. Scrivener, J. F. Martirena & M. Antoni, “Tackling social housing through the commercial use low clinker cementitious systems: Innovation on the use of calcined clay as Supplementary Cementitious material,” in Conference Proceedings 2012 nternational Conference of Tackling Technologies for sustainable development: A way to reduce poverty? pp.1-15 [9] R. D. Toledo Filho, J.P. Gonçalves, B.B. Americano, E.M.R. Fairbairna, “Potential for use of crushed waste calcined-clay brick as a supplementary cementitious material in Brazil,” Cement and Concrete Research, vol 37,no. 9, pp.1357–1365, Sept.2007. doi:10.1016/j.cemconres.2007.06.005 [10] BS 1881-116(1983) Testing concrete Method for determination of compressive strength of concrete cubes [11] BS 1881 Part-5 (1983) Part 122. Method for determination of water absorption. [12] A.M. Neville, Properties of Concrete England: Pearson Education Limited (2002) 126

CHAPTER 19 EFFECT OF CURING AND MIXING METHODS ON THE COMPRESSIVE STRENGTH OF MORTAR CONTAINING OIL M H. Almabrok, R G. McLaughlan and K. Vessalas ABSRACT Oil contaminated fine aggregate is a major environmental concern and can arise as a by product of industrial activities (e.g. oil well drilling and land contamination). Cement–based stabilisation/solidification of oil contaminated materials is an emerging technology however there are some issues that have not been fully addressed. This paper reports the results of a study conducted to investigate the effect of different curing and mixing methods on cement solidification and its consequent effect on the compressive strength of the resultant cementitious product. This work has been done to address leaching concerns during the curing period. The normal curing method for samples to be tested for compressive strength is lime saturated water. However, this method invalidates any subsequent leaching tests. Accordingly, bag curing (BC) and lime saturated water curing (LSW) have been applied using mortar mixed with mineral oil up to 10% by sand mass under water wet (WW) or oil wet (OW) mixing methods. The results indicate that development in 28 day compressive strength can be achieved without applying water by external means if the moisture movement from the mortar samples is prohibited, irrespective of the mixing methods used. Keyword: Mortar, curing, compressive strength, mixing method, mineral oil INTRODUCTION One of the most important aspects regarding the performance of monolithic solidified/ stabilised (S/S) material is its ability to resist mechanical stress in the form of a compressive strength test. Compressive strength is linked to the progress of the hydration reaction and the durability of a monolithic S/S material, and is therefore a key variable [1]. The development of the compressive strength of the resultant cementitious product (e.g. mortar) is largely depends on the curing conditions (temperature and humidity) during the curing period [2]. Curing is the process of controlling the rate and extent of moisture loss from mortar during cement hydration. Generally the hydration of cement takes place only if there is enough moisture. This happens at sufficient relative humidity (≥ 80%) whereas if the humidity within the capillaries drops below 80%, the hydration almost ceases [3], [4]. Keeping mortar in a moist environment is important in relation to the development of hydration products as it reduces the porosity in hydrated cement and increases the density of the microstructure in mortar [2], [4]. To prevent the moisture movement or evaporation, a proper curing method is needed. This can be accomplished by keeping the mortar elements as saturated as possible in order to produce a strong and durable specimen [5], [6]. School of Civil and Environmental Engineering, Faculty of Engineering, University of Technology, Sydney, Australia 127

Several researchers have discussed the effect of curing condition on the properties of the cementitious product [7-9]. However, the effect of the non-standard curing method on the mortar containing oil has not been studied to date. The objective of this paper is to primarily investigate the effect of different curing and mixing methods on the performance (i.e. compressive strength) of mortar containing mineral oil. The fresh properties (flow, wet density and air content) have been tested to identify if they have any effect on the resulting strength. METHODOLOGY MATERIALS General Purpose Cement (Cement Australia) which meets the general purpose (GP) requirements specified in AS 3972 [10] was used. The chemical properties of the cement used are shown in Table 1. The fine aggregate was that of Calga double washed sand (Rocla Quarry Products Pty Ltd) with an absorption capacity of 0.65%, specific gravity of 2.57 and median particle size of 0.5mm. The particle size distribution of Calga sand by sieving method (AS 1411.11.1) [11] is illustrated in Figure 1. The water sourced was of drinking water standard (pH 7.4; 2.29 µS/cm). Glenium, a polycarboxylate ether polymer based high-range water reducing admixture (HWR) (BASF Construction Chemicals Pty Ltd) was used. The mineral oil (Castrol Motorcycle Fork Oil – SAE 10) employed had a viscosity similar to medium crude oil (~ 35 mm2/sec @ 40 °C). Table 1 Chemical properties of cement Chemical entity Proportion Portland cement clinker < 97 % Gypsum (CaSO4·2H2O) 2-5% 0 – 7.5 % Limestone (CaCO3) 0-3% Calcium Oxide < 20 ppm Hexavalent Chrome (Cr VI) < 0.04 - 0.5 % Crystalline Silica (Quartz) 3 - 3.2 Specific gravity 128

Figure 1 Particle size distribution (sieving method) of Calga double washed sand MIX PROPORTIONS The composition of the mortar was in accordance with AS 2350.12 [12] with the mix proportions being 1 part of cement and 3 parts of sand (by mass) at a fixed water/cement ratio (w/c) of 0.50. Each mortar batch comprised cement (225g), fine aggregate (675g), water (112.4g), and HWR (0.2ml) with between 0 to 10% of added oil (by sand mass). This has been reported as 0 to 67.5 grams. MIXING AND CASTING OF TEST SAMPLES The mixing process followed the procedure outlined in AS 2350.12 [12] except for the oil addition using the Hobart mixer (model N-50 G) mixer. Two different mixing protocols (water-wet; oil- wet) were used. For the water wet method, mineral oil was weighed (% by sand mass) and premixed thoroughly with sand for 5 – 7 minutes using a spatula before adding to the other ingredients. For the oil wet method, the same mixing procedure as specified for the water wet method was followed unless the oil was mixed with cement instead of sand. All laboratory work was conducted at 22 ± 2 C°. HWR was added directly to water before the commencement of mixing and it was used with all the mixes to give reproducible flow (60 ± 10%). This proved to be most suitable for proper consolidation of the samples by hand. The protocol for moulding the mortar (ASTM C109) [13] was adopted and modified to minimise any impact of the protocol on any subsequent leaching tests. No mould-release agent was used; instead, cube moulds were lined with non-sticking tape. The moulds containing consolidated mortar were sealed in zip lock plastic bags to prevent moisture loss and stored in a moist atmosphere for 24 hours. Demoulding took place thereafter and triplicate mortar specimens having 50 x 50 x 50 mm dimensions were then again sealed in zip lock plastic bags and placed into a curing tank filled with water for up to 28 days at a temperature of 22 ± 0.5°C. Testing for fresh properties was also done on triplicate samples. CURING METHODS Once the samples were stripped from their respective mould, demoulding took place and the samples were cured under two types of curing until the day of testing. These were bag curing (BC) and lime saturated water curing (LSW). In bag curing, the samples were sealed in zip lock plastic bags and thereafter placed in plastic container with lid filled with water. In lime saturated water, lime (3 g/L) was used to saturate the curing water. The curing temperature was maintained at 22 ± 2 ºC in all of the curing methods. 129

TESTING PROCEDURES Flow was determined by the spread diameter on a hand driven flow table. Wet density was assessed based on the mass per unit volume of freshly mixed mortar. The air content was measured by the means of the air entrainment meter (TESTING Bluhm & Feuerherdt GmbH).The compressive strength was determined using an Avery Compression Testing Machine (ACTM) with a maximum capacity of 1993kN following the listed procedures of the test method ASTM C109 [13]. Vertical load at a rate of 1.5kN/sec was exerted on the samples and the maximum load indicated by the testing machine (load at failure) was recorded. EXPERIMENTAL RESULTS AND DISCUSSION FRESH PROPERTIES The flow of all mortar mixes were 60 ± 10% with 0.2 ml HWR whether the water wet or oil wet are used as the mixing method indicating that the mixing method has no significant effect on flow (Table 2). Wet densities were found to decrease with increasing oil addition levels irrespective of the type of mixing method (Table 2). The reduction in the wet density ranged from approximately 2% to 9% for both methods compared to the control mix. This reduction can be attributed to the oil free mortar (2270 kg/m3) being replaced by lower density oils (866 kg/m3) when it is placed in a mould of a fixed volume rather than being the result of any effects of the mixing method. As a general trend, the percentage of air content decreases with increased oil content in the mortar mixes (Table 2). However, it is noted that the air content is not of a significant effect due to the use of different mixing methods (water wet and oil wet) where the air content in the both methods varies from 3 – 7%. Table 2 Fresh properties of mortar for water wet and oil wet mixing methods Oil content Flow Wet density Air content (%) (g) Mix (%) STDEV (kg/m3) STDEV (%) STDEV 00 method 54 1.0 2270 1.2 6.4 0.5 2 13.5 70 1.0 2222 1.0 7.0 0.2 4 27.0 WW 63 2.1 2176 1.5 6.3 0.3 6 40.5 WW 62 1.7 2136 0.6 5.7 0.4 8 54.0 WW 62 1.4 2096 1.5 4.8 0.2 WW WW 10 67.5 WW 70 1.3 2060 1.2 3.2 0.3 2 13.5 OW 69 1.7 2224 1.2 6.5 0.5 4 27.0 OW 64 1.3 2180 1.0 5.9 0.6 6 40.5 OW 62 1.7 2139 0.6 5.5 0.4 8 54.0 OW 61 1.3 2100 1.2 4.3 0.2 65 1.0 2062 1.0 3.2 0.2 10 67.5 OW WW: water wet OW: oil wet STDEV: standard deviation 130

COMPRESSIVE STRENGTH The behaviour of 7 and 28 days compressive strength of all samples incorporating oil was quite different from that without oil (Figure 2, Figure 3). All mixes follow a similar trend where higher oil contents in mortars resulted in decreased compressive strength. An increase in the compressive strength with age (7 versus 28 days) was noted in all the mortar samples, irrespective of the curing or mixing methods utilised. However, for the water wet oil containing samples, the compressive strength development is greater at 7 and 28 days in the lime cured samples than for the bags cured ones. The difference is not significant based on the scatter which was evident in the error bars (Figure 2). The 7 day compressive strength for the BC oil wet samples has greater early stage development compared to the equivalent 7 day LSW cured samples. However at later times (28 days) there is no significant difference based on the samples variability measured by error bars (Figure 3). Further work is needed to better understand these early stage hydration processes in oil contaminated mortars. The overall finding of this investigation indicated that the curing methods do not have a significant effect on the development of 28 day compressive strength. This is attributed to there being sufficient moisture and suitable vapour pressure present in both methods which together work to maintain the hydration of the cement. The results of the bagged cured generally indicate that the development in compressive strength can be achieved without applying water by external means if the moisture movement from the mortar samples is prohibited. Reference [14] also tested different curing methods and indicate that regardless of the curing method used, the compressive strength of concrete increases with increasing age and there is no significant difference between the methods employed. Indeed, they found that the compressive strength of water cured microsilica concrete was 56.60 and 64.81 MPa at 28 and 91 days, respectively. Wrapped curing (equivalent to BC) produced a compressive strength close to that of water curing. Wrapped curing provided a compressive strength of 55.50 and 62 MPa at 28 and 91 days, respectively. Figure 2 Variation in compressive strength for mortar mixes containing mineral oil using the water wet (WW) method for bag curing (BC) and lime saturated water curing (LSW) (Error bars equal average ± standard deviation) 131

Figure 3 Variation in compressive strength for mortar mixes containing mineral oil using the oil wet (OW) method for bag curing (BC) and lime saturated water curing (LSW) (Error bars equal average ± standard deviation CONCLUSION Cement – based stabilisation/solidification of oil contaminated material is an emerging technology however there is limited knowledge on the effects of the curing and mixing methods in relation to the properties of the resultant cementitious mix. With regard to the inhibition of cement hydration and its consequent effects on compressive strength, the overall finding of this investigation indicates that the fraction of oil in the mortar plays a more important role than the curing or mixing methods. Despite the fact that in the oil wet method, the oil is coated the cement particles prior to contacting the water, the water wet and oil wet methods exhibit the same trend, whereby higher oil content in mortar results in decreased compressive strength with strength developing from 7 to 28 days. Furthermore, it was found that a bag-cured protocol developed for this research was able to produce mortars with almost similar physical properties to that produced by the standard lime saturated curing protocol. The development of compressive strength with maturity shows that cement hydration occurs in all mixes but to varying degrees. This may be attributed to there being sufficient moisture and suitable vapour pressure present in both methods which in tandem works to maintain the hydration of the cement. ACKNOWLEDGMENT The authors gratefully acknowledge the financial support provided by the Libyan Embassy in Australia for this research. The authors also acknowledge the support and cooperation provided by Mr. Rami Hadad, Manager, Civil Laboratories at the University of Technology, Sydney. Finally, the authors extend their special gratitude to the Rocla Quarries for providing the Calga sand used in this investigative work. 132

REFERENCES [1] AL-Tabbaa, A. S. Perera,“Stabilisation/solidification treatment and remediation. Part IV: Testing and performance criteria,” In Proceedings of the International Conference on Stabilisation/Solidification Treatment and Remediation, Cambridge, UK, 2005, pp. 415– 435. [2] M. R. Aminur, M. R. Harunur, D. C. L. Teo and M. M. Abu Zakir, “Effect of aggregates and curing conditions on the compressive strength of concrete with age,” UNIMAS e-Journal of Civil Engineering, vol. 1, issue. 2, pp. 1– 6, 2010. [3] M. Neville, Properties of Concrete. 4th and Final ed. UK: Pearson Education Limited, 2009. [4] M. Safiuddin, S. N. Raman, and M. F. M. Zain, “Effect of different curing methods on the properties of microsilica concrete,”Australian Journal of Basic and Applied Sciences, vol. 1, issue. 2, pp. 87–95, 2007. [5] N. Gowripalan, J. G. Cabrera, A. R, Cusens and P. J. Wainwright, “Effect of curing on durability,”in Durable Concrete (ACI Compilation 24), American Concrete Institute, Michigan: Farmington Hills, January 1992, pp. 47–54. [6] M. F. M. Zain and Y. Matsufuji,“The influence of curing methods on the physical properties of high strength concrete exposed to medium temperature (20–50 ºC), ”In the proceeding of the 5th international Conference on Concrete Engineering and Technology, Kuala Lumpur, Malaysia, 1997. [7] S. Al-Gahtani, “Effect of curing methods on the properties of plain and blended cement concretes,”Construction and Building Materials, vol. 24, pp. 308–314, 2010. [8] M. N. Qureshi and S. Ghosh, “Effect of curing conditions on the compressive strength and microstructure of alkali- activated GGBS paste,” International Journal of Engineering Science Invention, vol. 2, issue. 2, pp. 24 –31, 2013. [9] K. Tan and O. E. Gjorv, “Performance of concrete under different curing conditions,” Cement and Concrere Research, vol. 26, issue. 3, pp. 355–361, 1996. [10]AS 3922, “Portland and blended cements,” Standards Australia International Ltd, 2010. [11]AS 1141,“Method for sampling and testing aggregates. Method 11.1: Particle size distribution - sieving method,”Standards Australia International Ltd, 2009. [12]AS 2350.12, “Methods of testing portland, blended and masonry cements. Method 12 : Preparation of a standard mortar and moulding of specimens,” Standards Australia International Ltd, 2006. [13]ASTM C109/C109M, “Standard test method for compressive strength of hydraulic cement mortars (using 50 mm cube specimens),”ASTM International, 2008 [14]M. Safiuddin, S. N. Raman and M. F.M. Zain, “Effect of different curing methods on the properties of microsilica concrete,” Australian Journal of Basic and Applied Sciences, vol. 2, issue. 1, pp. 87–95, 2007. 133

CHAPTER 20 IMPROVING THE STRENGTH PERFORMANCE OF HIGH VOLUME PERIWINKLE SHELL ASH BLENDED CEMENT CONCRETE WITH SODIUM NITRATE AS ACCELERATOR Akaninyene A. Umoh1, Anthony O. Ujene2 ABSTRACT The objective of this study is to examine the effect of accelerator (NaNO3) on the strength properties of High volume Periwinkle shell ash blended cement concrete. A mix ratio and water- binder ratio of 1:2:4 (cement: sand: gravel) and 0.60, respectively was used as the reference. The cement was then replaced with 30% Periwinkle Shell Ash (PSA) by weight of cement. Sodium nitrate in the dosages of 1, 2, and 3% by weight of cement was added to the blended mixture of cement and PSA. The strength properties investigated were compressive and splitting tensile strength tested at 7, 14 and 28 days hydration. The results indicated that the compressive strength and the splitting tensile strength generally increases with curing age, and that sodium nitrate of up to 2% dosage greatly improved the strength performance of high volume PSA blended cement concrete over that of the reference. The study concluded that the inclusion of 2% sodium nitrate by weight of cement in the mixture could be considered the optimum dosage for the improvement of both compressive and splitting tensile strength of concrete incorporating up to 30% PSA content. Keywords: compressive strength, periwinkle shell ash, tensile splitting strength, sodium nitrate, accelerator INTRODUCTION Periwinkles are marine snails belonging to the family of gastropoda found on land, in fresh water and in salt water. The species that is commonly found in the Niger Delta of the South – South region of Nigeria is termed Tympanotonus fuscatus and their habitat is mainly the brackish water creeks and mangrove swamps in the Niger Delta area at the inter-tidal zone, where they are found in clusters [1], [2]. They are dark and have thick elongated conical shape with narrow deep posterior canals and siphonal notches. A study indicated that there are about 40.3 tonnes of periwinkle per year being harvested from 35 mangrove communities of Delta and Rivers states [3]. When the edible part of periwinkle has been removed, the shell is being dump as waste. In communities’ border with rivers, and in coastal regions of Nigeria where periwinkles are used as food, the shells posed environmental nuisance in terms of its unpleasant odour and unsightly appearance in open–dump sites. The utilization of these shells by burning it under control condition to form ash, that is Periwinkle shell ash, and used as partial replacement of cement in concrete have been reported [4 - 6]. The assessment of the suitability of periwinkle shell ash (PSA) as partial replacement for ordinary Portland cement (OPC) in concrete [7] reported that the compressive strength of concrete specimens decreased as the percentage of PSA content increased. 134

Similar studies [4,6] separately indicated that periwinkle shell ash with replacement level up to 10% in binary blended system in concrete have been reported to enhance concrete strength and durability. The use of PSA in concrete as reported by various researchers [6,8-9] pointed to the fact that only 10% replacement is effective in contributing to properties of the concrete. To enhance the performance of concrete in terms of its strength and durability, the use of admixtures, mineral or chemical admixture, as a component of the concrete material has been advocated. According to National Ready Mixed Concrete Association, NRMCA [10], chemical admixtures are used to enhance the properties of concrete in the fresh and hardened state. These properties may be modified to increase compressive and flexural strength at all ages, decrease permeability and improve durability, inhibit corrosion, reduce shrinkage, accelerate or retard initial set, increase slump and workability, improve pumpability and finishability, increase cement efficiency, and improve the economy of the mixture. Seven functional categories of chemical admixtures have been presented [11] to include retarding admixtures, accelerators, air-entraining agents, anti-freezing admixtures, anti-washout admixture, shrinkage reducing admixtures and high-range water reducers. This study is concerned with the use of accelerators. Accelerators speed up the setting and rate of strength gain [10] and thereby making the concrete stronger to resist damage from freezing in cold weather. Accelerators are also used in fast track construction requiring early form removal, opening to traffic or load application on structures. Many substances are known to act as accelerators for concrete and include Alkali Hydroxides, Silicates, Fluoro-Silicates, Calcium Formates, Calcium Nitrates, Sodium Nitrate, Calcium Thio Sulphates, Aluminium Chlorides, Potassium Carbonates, Sodium Chlorides and Calcium Chlorides. However, non- chloride admixtures are preferred as those containing chlorides are believed to accelerate corrosion of reinforcement. The enhancement of concrete strength through the use of chemical admixtures in concrete has form the thrust of this study to improve the strength performance of concrete blended with high volume periwinkle shell ash up to 30% by weight of cement using sodium nitrate as an accelerator. METHODOLOGY Ordinary Portland cement (Unicem brand) was used which production conforms to the Nigeria Industrial Standard [12]. Erosion sand and granite chippings were used as fine and coarse aggregate, respectively. The sieve analysis of the erosion sand shows that it is in zone 2; while the coarse aggregate were predominantly of maximum aggregate size of 15mm and both met the requirement of BS 882 [13]. Water used for the study was tap water while sodium nitrate (NaNO3) was used as chemical admixture. The periwinkle shells were obtained from Ishiet, Akwa Ibom State. The shells were calcined in a gas furnace at 600 for 20-30 minutes and allowed in the furnace for 24 hours in order for it to cool. Thereafter, the ash was removed from the furnace, pound and sieved to particle sizes less than 75 µm to obtain a fine ash. Chemical analysis conducted on the ash and as presented in Table 1shows that it has a higher content of calcium oxide (CaO). Table 1 Chemical Composition of Periwinkle Shell Ash Elemental Oxide SiO2 AL2O3 Fe2O3 CaO MgO SO3 K2O Na2O Mn2O3 % 27.20 6.42 4.64 52.10 0.82 0.26 0.25 0.26 0.14 135

A mix ratio of 1:2:4 (cement: erosion sand: granite chipping) by weight and water-cement ratio of 0.60 was adopted as a reference mix. The cement constitute in the reference mix was replaced by weight with 30% quantity of periwinkle shell ash (PSA) and thereafter a Sodium nitrate (NaNO3) of various dosages of 1, 2 and 3% by weight of cement were added to the 30% PSA blended cement concrete mix.The essence was to assess the effect of the NaNO3 on the strength performance of the concrete when compared to the reference and blended mixes. Mixing was done manually using a shovel. The materials, cement or PSA or both, and aggregates were measured and mix dry until a uniform consistency was attained. The required water and sodium nitrate were measured and gradually added to the already mixed materials and thoroughly mixed until a workable mix was obtained. The wet mixture was then cast in 100 mm cube moulds and properly marked for identification prior to de-moulding after 24 hours of casting. The de-moulded concrete specimens were water cured for 7, 14 and 28 days corresponding to their testing ages. The compressive strength test was carried out at testing ages of 7, 14 and 28 days using a compression test machine of capacity 1000 KN, and as specified by [14]. The compressive strength values were calculated from (1) thus: Where Cs is the Compressive strength of the concrete cube specimens in N/mm2, P is the failure load in Newton, and A is the Area of the cube specimen in mm2 Tensile Splitting Strength test was equally carried out using concrete cube size 100 mm. The test was done in line with [15]. The tensile splitting strength values were calculated from (2) thus: Where ST is the tensile splitting in N/mm2, Ps is the splitting load in Newton, and l is the length of each side of the specimen in mm. RESULTS AND DISCUSSION COMPRESSIVE STRENGTH The results of Compressive Strengths of PSA blended cement concrete tested at 7, 14 and 28 days are presented in Tables 2. The results indicated that the reference mix (that is mix with 0% NaNO3 and 0% PSA content) had compressive strength values of 16.67 N/mm2, 21.12 N/mm2 and 24.86 N/mm2 at 7, 14 and 28 days hydration, respectively; but with the replacement of cement with 30% PSA content, the strength was noticed to reduce to 14.60 N/mm2, 17.22 N/mm2 and 20.66 N/mm2 at 7, 14 and 28 days, respectively. The value of 20.66 N/mm2 recorded at 28 days by the mix containing 30% PSA is comparable to the values obtained by [6, 7] which used the same mix proportion of 1: 2: 4 with 30% PSA content replacing cement in their investigation. The inclusion of sodium nitrate in the mixture was noted to enhance the strength performance of the concrete. The strength increases with increase in the quantity of sodium nitrate up to 2% content and start to reduce at 3% dosage. Therefore a peak compressive strength was noted to attain with 2% dosage of NaNO3 at all the curing ages. This indicate that 2% sodium nitrate inclusion in the mixture could be considered the optimum dosage for the improvement of compressive strength of concrete incorporating up to 30% PSA content. 136

Table 2 Compressive Strength of PSA blended cement concrete at Various Ages. PSA (% replacement of cement NaNO3 (% replacement of Compressive Strength (N/mm2) by weight) cement by weight) 7 Days 14 Days 28 Days 0 0 16.67 21.12 24.86 30 0 30 1 14.60 17.22 20.86 30 2 30 3 17.07 20.16 23.30 19.83 22.50 25.10 17.90 20.24 23.83 TENSILE SPLITTING STRENGTH The results of Tensile Splitting Strength as presented on Table 3 show that the reference mix recorded a tensile splitting strength that range between 1.67 N/mm2 and 1.86 N/mm2, and with the inclusion of 30% PSA in the mix the values were reduced to a range of 1.16 N/mm2 and 1.63 N/mm2 for the testing period of 7 to 28 days, respectively. These results agree with the findings [5] that tensile splitting strength increase with curing age and decreases as the percent weight of PSA increases from 15% to 30%. The incorporation of NaNO3 up to 2% content was noticed to enhance the strength and thereafter the strength decline with increased in NaNO3 beyond 2% content. Periwinkle shell ash blended cement concrete incorporating 2% NaNO3 was observed to attain the highest tensile splitting strength at all the curing ages of 7, 14 and 28 days, this was closely followed by mix containing 30% PSA and 3% NaNO3 especially at 28 days hydration. These findings indicate that sodium nitrate can be used to improve tensile strength performance of high volume periwinkle shell ash blended cement concrete. Table 3 Tensile splitting Strength of PSA blended cement concrete at Various Ages. PSA (% replacement of cement NaNO3 (% replacement of Tensile splitting Strength (N/mm2) by weight) cement by weight) 7 Days 14 Days 28 Days 0 0 1.67 1.72 1.86 30 0 30 1 1.16 1.27 1.63 30 2 30 3 1.36 1.44 1.80 1.68 1.79 2.87 1.60 1.66 2.76 CONCLUSIONS The study revealed that the inclusion of NaNO3 in high volume periwinkle shell ash blended cement concrete had contributed to the enhancement of the concrete compressive and splitting tensile strength performances. It was equally observed that there was continuity of performance with curing age and therefore, it is recommended that NaNO3 in the dosage of 2% of cement weight should be added to high volume periwinkle shell ash blended cement concrete mix to improve its performance. 137

REFERENCES [1] M. A. O. Badmus, T. O. K. Audu, and B. U. Anyata, “Removal of Lead Ion from Industrial Wastewaters by Activated Carbon prepared from Periwinkle Shell (Typanotonus Fuscatus),” Turkish Journal of Engineering and Environmental Science, vol. 31, pp. 251-263, 2007. [2] N. Jamabo, and A. Chinda, “Aspects of the Ecology of Tympanotonous fuscatus var fuscatus (Linnaeus,1758) in the Mangrove Swamps of the Upper Bonny River, Niger Delta, Nigeria,” Current Research Journal of Biological Sciences, vol. 2, no. 1, pp. 42-47, 2010. [3] P.C. Mmom, and S.B. Arokoya, “Mangrove Forest Depletion, Biodiversity Loss and Traditional Resources Management Practices in the Niger Delta, Nigeria,” Research Journal of Applied Sciences, Engineering and Technology, vol. 2, no. 1, pp. 28-34, 2010.A. [4] A. Umoh, and K. O. Olusola, “Compressive strength and static modulus of elasticity of periwinkle shell ash blended cement concrete,”International Journal of Sustainable Construction Engineering & Technology, vol. 3, no. 2, pp. 45-55, 2012. [5] A. Umoh, A. Olaniyi, A. J. Babafemi, and O. O. Femi, “Assessing the Mechanical Performance of Ternary Blended Cement Concrete Incorporating Periwinkle Shell and Bamboo Leaf Ashes,” Civil and Environmental Research, vol. 3, no. 1, pp. 26-35, 2013. [6] I. O. Dahunsi, and J. A. Bamisaye, “Use of Periwinkle Shell Ash (PSA) as Partial Replacement for Cement in Concrete, Proceedings the Nigerian Materials Congress and Meeting of Nigerian Materials Research Society, Akure, Nigeria, 2002, Nov.11 – 13, pp. 184-186. [7] F. A. Olutoge, O. M. Okeyinka, and O. S. Olaniyan, “Assessment of the suitability of periwinkle shell ash (PSA) as partial replacement for ordinary Portland cement (OPC) in concrete,” IJRRAS, vol. 10, no. 3, pp. 428-433, 2012. [8] K. O. Olusola, and A. A. Umoh, “Strength Characteristics of Periwinkle Shell Ash Blended Cement Concrete,” International Journal of Architecture, Engineering and Construction, vol. 1, no. 4, pp. 213-220, December 2012. [9] B. R. Etuk, I. F. Etuk, and L. O. Asuquo, “Feasibility of Using Sea Shells Ash as Admixtures for Concrete,” Journal of Environmental Science and Engineering A 1, pp. 121-127, 2012. [10] National Ready Mixed Concrete Association, NRMCA, “Concrete in practice, what, why & how?” NRMCA Publication No.173, 2001. [11] P. Mihai, and R. B. Rosca, “Characteristics of concrete with admixtures,” Gheorghe Asachi Technical University Bulletin 56, no. 58, 2008. [12] NIS 444, Cement: Part 1-Compositiojn, Specification and Conformity Criteria for Common Cement, Abuja, Nigeria, 2003. [13] BS 882, Specification for aggregate from natural sources for concretes part II, London, British Standard Institution, 1992. [14] BS EN 12390, Testing hardened Concrete: Compressive strength of test specimens, part 3, London, British Standard Institution, 2009. [15] BS 1881, Testing hardened Concrete: Tensile Splitting strength of test specimens, part 117, London, British Standard Institution, 1983. 138

CHAPTER 21 CHLORIDE RESISTANCE OF BLENDED ASH GEOPOLYMER CONCRETE Mohd Azreen Mohd Ariffin* and Mohd Warid Hussin ABSTRACT Chloride attack on concrete is a mechanism of deterioration which causes corrosion of steel reinforcement. Geopolymer, an alternative aluminosilicate binder material, has attracted attention for its structural and durability performance as well as for environmental benefits in reducing the CO2 emissions associated with concrete production. However, the understanding of its behaviour in the chloride resistance of geopolymer concrete especially from mixtures of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) is scarce. In this study, geopolymer concrete using blended ashes from agro-industrial waste were tested for chloride content using ASTM 1543-10a (Standard Test Method for Determining the Penetration of Chloride Ion into Concrete). The geopolymer concrete samples were prepared using a mix of the PFA and POFA as the main binder components at the range of alkaline/binder ratio of 0.4 together mixed with coarse and fine aggregates. The ambient temperature (26-30°C) of curing regimes was used. The specimens were cast in 100mm3 molds. After achieving the targeted compressive strength (25-30 MPa), the specimens were immersed for 18 months to 2.5% solution of sodium chloride (NaCl). The normal OPC concrete with similar compressive strength were also prepared for direct comparison. X-ray diffraction (XRD), Fourier Transformed Infrared Spectrometer (FTIR), Thermogravimetry analyser (TGA-DTG) and Field Emission Scanning electron microscopy images with energy dispersive X-ray (FESEM-EDX) were performed to analyze the microstructural characterisation of the materials. In particular, geopolymer concrete had shown a better resistance to chloride penetration as compared to OPC concrete Keywords: Geopolymer, Palm Oil Fuel Ash (POFA), Chloride, Durability INTRODUCTION With an annual production of almost 3 Gt, Ordinary Portland cement (OPC) is the dominant binder of the construction industry [1-2]. The production of one ton of OPC generates almost one tone of CO2. Manufacturing of cement accounts for as much as 5% of global CO2 emissions to the environment, making one of the main contributors to global climate change [3]. Research works carried out so far in the development of alkali-activated cements showed that much has already been investigated and also that an environmental friendly alternative to Portland cement is rising [4]. Davidovits [5] was one of the author to address the carbon dioxide emissions of these binders stating that they generate just 0.184 tons of CO2 per ton of binder. Geopolymer is a potentially valuable new material for use in the concrete and construction industry. Made from industrial by products or wastes from processes such as pulverized fuel ash (PFA), and iron manufacture (slag), these low- CO2 binders have proven to give comparable mechanical properties to normal Portland cement concrete, and ongoing work, including the study presented in this paper, is giving increased confidence in its likely durability in service. Faculty of Civil Engineering, Universiti Teknologi Malaysia, Malaysia Email: [email protected] 139

Geopolymer is synthesized from a combination of an alkaline solution with a reactive aluminosilicate powder such as metakaolin, fly ash and/or slag. The reaction of the aluminosilicate with the alkali results in the dissolution of the solid raw material, forming a disordered alkali aluminosilicate gel phase known as the geopolymeric gel binder, which also contains some embedded partially reacted solid precursor particles, and the water used in mixing [6]. The development of understanding of aggressive environments attacks on concrete is probably the most extensively observed and researched aspect of concrete durability worldwide. Chloride attack is one of an important durability and serviceability concern for geopolymer materials used in construction. Corrosion of embedded steel bars is the main consequence when chloride penetrates into concrete. The 23 applications of de-icing salts, marine exposure, airborne salt or sodium chloride are the sources of chloride ions that can pose threats to concrete structures. Steel embedded in concrete usually has a protective passive layer, which is formed as an oxide layer while the pH of the pore solution is sufficiently high. However, when chloride ions are present, the protective layer will be destroyed, leading to corrosion of the steel reinforcement. Furthermore, different types of chlorides such as NaCl and CaCl2 would also cause the changes of microstructure of concrete [7]. To date, there have been limited investigations on the effects of chloride ingress in geopolymer concrete. This paper generally focuses on the use XRD, FTIR, FESEM-EDX and TGA-DTG techniques for investigating blended ash geopolymer (BAG) concrete using PFA and POFA from agro-industrial wastes. The durability of BAG concrete in comparison with OPC concrete immersed in sodium chloride with 2.5% concentration up to 18 months was investigated. METHODOLOGY In the present experimental work, dry pulverized fuel ash (PFA) obtained from the silos of Kapar Power Station, Selangor, Malaysia was used. While, Palm Oil Fuel Ash (POFA) was obtained as a result of burning of palm oil shell and husk from Kahang mill in Johor, Malaysia. The PFA and POFA have a mean particle size of 45 μm. The main chemical compositions of the PFA, POFA and ordinary Portland cement (OPC) as determined by X-Ray Fluorescence are shown in Table 1. The silica/alumina ratio (SiO2/Al2O3) is approximately 1.3 for PFA whereas POFA has higher silica content and reactive silica. To activate the blended ash, a commercial grade sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions were used as alkaline activator. Local crushed granite sand with a specific gravity of 2.62 and aggregates (10mm sizes) were used for making concrete. In order to improve the workability, high range water reducing super plasticizer (naphthalene sulphonate) and extra water was added to the mixture. Table1. Chemical Composition (%) of PFA, POFA and OPC Geopolymer concrete can be manufactured by adopting the conventional techniques used in the manufacture of OPC concrete. In the laboratory work, the blended ash and the aggregates were first dry mixed in 80 litre capacity pan mixer for five minutes. Both coarse and fine aggregates were in saturated surface dry condition. The alkaline liquid containing sodium hydroxide and sodium silicate was added and mixed for another five minutes. All geopolymer concrete specimens were prepared with an alkaline solution to blended ash ratio of 0.4 by mass and the concentration of NaOH in 140

solution was 14Molar. The ratio of sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) was 2.5 by mass. The super plasticizer was used to achieve the workability of geopolymer concrete in between 80-100mm slump. Some additional water was also added to the mixture. A class F PFA and POFA have been activated in an alkaline solution to form Geopolymer gel and further binding aggregates to make concrete. The preparation process and composition of the investigated materials were developed and published earlier [8]. The salt ponding test is one of the tests that are commonly used around the world in identifying the chloride penetration into a concrete. Modified to ASTM C1543-10a (Standard Test Method for Determining the Penetration of Chloride Ion into Concrete by Ponding), this process is done by exposing the top surface of samples 100mm concrete cubes to a solution containing chloride where sodium chloride (NaCl) is used. The solution is ponded, at least 20mm high as to create enough amount of chloride to penetrate the sample and the process is set to at least 18 months so that a significant result can be achieved.Immediately after completing the immersion period, the samples are then dried of the solution and left to dry for one day, where deposits of white salts can be found on the surface of the sample, brush off the salts before further tests can be done. In Figure 1, the samples are sliced at a depth of 10-20mm (Disc1), 25-35mm (Disc2), 40–50mm (Disc3) and 55– 65mm (Disc 4). Figure 1 Depth of sample The samples were then ground to powder forms in order to determine the chloride ion content. The tests are carried out by using the chloride penetration machine (HACH Machine). Control specimens (without salt ponded test) are kept in ambient condition for comparison. OPC concrete with water/binder (w/b) ratio 0.6 was used. The specimens with w/b = 0.6 had the same consistency as the geopolymer specimens at w/b = 0.4. Thus, the specimens were compared as having the same consistency at the time of testing. The compressive strength of OPC and BAG concrete at the age of 28days were 27 MPa and 28MPa respectively. 2.5% concentration of the sodium chloride solution (NaCl) is used as the permeating reagent. All surfaces of the specimens are coated with a sealant except one. The test was done for 18 months where the sample was left to be submerged in the solution for the whole duration in order to permeate the sample through the uncoated surface; this will give the ideas on how much chloride can penetrate through the specimens. OPC concrete was also prepared as a comparison. In order to obtain the result of chloride content from the solid specimens in powder form of the discs, it needed to be changed into the liquid form by a dilution process with distilled water as shown in Figure 2. 141

Figure 2. Samples in liquid form Equation (1) was based on American Public Health Association Standard Methods (APHA) shows the conversion of of chloride content, mg/L obtained from HACH Machine DR5000 into percentage (%) of the chloride for each of the specimen tested: Where, 142

RESULTS AND ANALYSIS CHLORIDE ANALYSIS Table 2 shows the chloride content for both OPC and BAG concrete. The first layer (Disc 1) of the sample gives a higher chloride penetration. This resulted due to the disc being exposed more of the solution than others after 18 months chloride ingress by the absorption process. Table 2. Chloride Content (%) of BAG and OPC concrete after 18month immersion From Figure 3, BAG concrete shows a lower amount of chloride content compared to OPC concrete samples. The ingress of chloride is significantly less in samples that are made of geopolymer compared to OPC. At the critical point, Disc 1 (10-20mm depth) shows that for BAG concrete, it does not exceed 0.20% while in OPC give the highest value up to 0.25%. At the lowest point, Disc 4 (55- 65mm depth), samples of OPC give the highest content of chloride that is 0.13% while BAG concrete gives the value of 0.09%. This result shows that the durability of the BAG concrete is significantly higher compared to OPC concrete in term of chloride penetration Figure 3. Chloride content (%) at different depth 143

The BAG concrete showed better performance than the OPC concrete when immersed in NaCl with 2.5% concentration due to difference in chemical composition. The chemistry of the material was certainly very important for its durability. The chloride penetration of OPC is higher due to the chemical composition with high calcium content whereas the BAG specimens with low Ca content performed significantly better than OPC specimens. X-RAY DIFFRACTION (XRD) ANALYSIS X-ray diffraction (XRD) technique was used to obtain a better understanding of the possible transformation in the original materials as well as the samples immersed in NaCl. The reaction between PFA, POFA and the alkaline activator i.e. sodium silicate and sodium hydroxide resulted in a partial crystalline phase. The broad peaks of the geopolymer component can be seen in the region 25-30ºC 2ϴ. Mineralogical characterization of the reaction product of alkali activation of the BAG concrete in Figure 4, shows crystalline quartz (Q), albite (A) and gmelinite (Gm).The main phase of BAG concrete discovered was a crystalline N-A-S-H phase, similar to albite (NaAlSi3O8, PDF03- 0451) [9-12]. Another phase in BAG concrete was gmelinite which produced from the reaction product of geopolymerisation and its represent the nanostructure of the zeolite precursor [13-15]. Figure 4, shows the XRD analysis results for the BAG concrete which consists of the samples (Disc1-4) after immersion in NaCl. In the initial sample, a semi-crystalline aluminosilicates gel (N-A- S-H) is detected as a main phase and it is still observed after immersing in NaCl. Figure 4. XRD for BAG concrete after 18 months immersion in NaCl Conversely, the OPC concrete shows a different picture when immersing in NaCl. Chloride penetration in concrete based on Portland cement is generally attributed to the formation of Friedel’s salt, and ettringite, with the presence of chloride ion and/or sulphate ion [16-18]. Figure 5, presents the XRD for the OPC concrete before and after immersion of NaCl. The OPC concrete, shows strong intensity peaks for quartz and C-S-H phase which similar to anorthite (CaAl2Si2O8, PDF10-0379)[8]. When the OPC concrete immersed in NaCl (Disc1-3), the chloride ions intrude into concrete and react with portlandite Ca(OH)2 to generate calcite. The absence of portlandite is described by its chemical reaction in the presence of CO2 to form calcium carbonate (calcite)[17-18]. Contrary to the samples of the depth interval (Disc1-3), the XRD for the Disc 4 shows the peaks for Portlandite phase and ettringite. However, the peak for calcite is not appearing which suggests the absence of severe carbonation at particular depths (Disc4). The absence of CaCO3 is connected by the presence of portlandite. Sulphate ions may penetrate into concrete from an external environment, its can react with C3A during its hydration process to form monosulphoaluminate or ettringite. 144