Fly Ash Based Geopolymer Mortar Research Articles

Feasibility of using slacked lime in producing high calcium fly ash based geopolymer mortar

Many efforts have been made to decrease ordinary Portland cement (OPC) consumption in the construction world. One of which is developing research on geopolymer material. A type of base material to produce geopolymers is fly ash that rich silica and alumina. This paper aims to the study possibility of using hydrated lime in producing high calcium fly ash based geopolymer mortar. The test material is then given curing treatment for 3 and 7 days before being tested for compressive strength. The test results of material characteristics indicate that the compressive strength at 7 days can be used as a concrete brick for class IV wall pairs for the level of quality of hollow concrete brick of 20 kg / cm2 based on SNI 03-0349-1989.

The Effect of Activator to Binder Ratio on the Compressive Strength of Fly Ash Based Geopolymer Mortar in Sulphate Environment

One of the significant characteristic material needed to consider is durability. Sulphate ion contained in soil is one of aggressive agents that could cause degradation of concrete members which led to loss of compressive strength. The current research is to elaborate the effect of activator to binder ratio on the compressive strength of the fly ash based geopolymer mortar in the sulphate environment. Two different types of geopolymer mortar were casted i. e. mortar made of 100% fly ash and mortar contained 95% fly ash + 5% slaked lime. The fly ash used in this research is classified as F fly ash from the Mpanau power plant the variation of activator to binder ratio of 0. 40; 0. 50; and 0. 60, and water/solid ratio variations of 0. 32, 0. 34 and 0. 36. The composition of sulfuric acid was by 5% of the sample volume. Geopolymers mortar compressive strength test is conducted on the immersed samples in a solution of 5% sulfuric acid with age of 0, 7, 14, 28, 56, and 84 days, respectively. The compressive strength test results showed that the highest compressive strength of geopolymers mortar (resistant to sulfuric acid attack) was geopolymers mortar made from fly ash with activator to binder ratio 0. 60, water / solid ratio 0. 32, and percentage of lime to binder 5% at the age of 84 days.

Very high strength Na2SiO3 and NaOH activated fly ash based geopolymer mortar

The paper presents the results of research of high-strength geo-polymer mortars, prepared from two types of siliceous fly ash. Sodium hydroxide and mixtures of sodium hydroxide and sodium silicate in the form of solutions were used as activators. The activator was added in amounts ranging from 6 to 15% NaOH in relation to the ash mass. After preparation, the mortars were cured at the temperature of 60ºC, 80ºC or 100ºC for various times, from 24 hours to 7 days. Increasing the addition of sodium or a higher curing temperature increase the flexural and compressive strength of the tested mortars. The best results - compressive and flexural strength of 100 MPa and 20 MPa, respectively, were obtained for mortar activated with 15% sodium hydroxide, cured at 100°C for 24 hours. Blended activator – sodium silicate and sodium hydroxide also allowed to obtain high strengths, but lower than sodium hydroxide alone. Extending the curing time at high temperature beyond 24 hours did not produce favourable results in most cases. Fly ash geopolymer mortar, activated with 15% NaOH by mass of ash, cured at 100°C for 24 hours, showed about 18% reduction in greenhouse gas emissions compared to common Portland cement mortar.

Performance of Crumb Rubber Incorporated Ferro Geopolymer Panels under Flexure

This research work presents the overview of geopolymer mortar application into the ferro cement panel with the incorporation of crumb rubber and Nano fly ash. The geopolymer mortar is prepared by using industrial wastes as a base material such as fly ash and ground granulated blast furnace slag (GGBFS) which generally helps to reduce the level of CO2 emission. Also, the recycled tyre crumb rubber is utilized as a sustainable innovative construction material which is used a partial substitution for sand upto 5% for enhancing the ductility without any strength degradation. These reduces land fill problems and ground water quality degradation problems. Crumb rubber has the ideal capacity to absorb energy from static and other kind of loads. The geopolymer binder preparation is done by utilizing material such as fly ash, GGBFS, alkaline liquid made of NaOH and Na2SiO3 , Nano fly ash. The Nano fly ash is used as an additive which helps in increasing the strength and durability of the element by its pore filling capability. This project aims to enhance the strength of fly ash based geopolymer mortar with the help of GGBFS incorporation. The molarity of alkaline activator, solution to binder ratio and silicate to hydroxide ratio is fixed as 12, 0.4 and 1.5 throughout the process. The mortar cubes and panels were heat cured under hot air oven at 80ᵒ C for 48 hours. The mechanical behavior of geopolymer mortar is assessed by compressive strength test water absorption test. The panel is made of high strength geopolymer mortar and expanded metal mesh with chicken mesh for obtaining higher energy absorption capacity with good deforming ability and less crack pronouncement. The investigation involves finding the initial crack load, ultimate failure load and residual flexural strength ratio. The results show that the tyre inclusion enhances the flexural strength of the ferro geopolymer panel by means of its ductile enhancing capacity

Resistance of fly ash based geopolymer mortar to both chemicals and high thermal cycles simultaneously

Geopolymer has already been used at a commercial airport, Brisbane West Wellcamp Airport (BWWA), and in mainline railway sleepers in Australia. It has also been proposed for use at military airbases to repair degraded concrete or any other special construction needs. Rigid pavements at military airbases, especially aprons, are frequently exposed to high thermal shocks by jet exhaust, and often get saturated by chemicals such as hydrocarbon fluids (HFs): aircraft’s engine lubricating oil, hydraulic fluid and jet fuel. To promote wider and reliable use of geopolymer at military airbases, the resistance of geopolymer to both HFs and high thermal cycles should be thoroughly assessed. The present study investigates the resistance of fly ash (FA) based 3-day and 28-day old geopolymer mortars to both HFs and high thermal cycles simultaneously and separately. This study has identified that irrespective of the age of the geopolymer mortar, they experience saponification when expose to both HFs and high thermal cycles simultaneously. Soap and salt compounds, e.g., sodium carboxylate and sodium phosphates were identified in the geopolymer mortar after the saponification occurrence. The crystal lattices of the 3-day old geopolymer mortar were significantly affected and decomposed when exposed to HFs and high thermal cycles simultaneously. Upon 60 cycles of heat exposure, 3-day and 28-day old geopolymer mortar treated with HFs lost 42.52% and 33.85% of their compressive strength, respectively. The geopolymer mortar exposed to HFs at ambient temperature did not suffer from saponification process, and the reduction in the compressive strength was almost insignificant. The effect of high thermal cycles in reducing the compressive strength of the geopolymer mortar was substantial. This paper also reports mass loss characteristics, microstructures and degrading mechanisms of geopolymer mortar after exposure to HFs and high thermal cycles.

UTILIZATION OF CRUMB RUBBER AS AGGREGATE IN HIGH CALCIUM FLY ASH GEOPOLYMER MORTARS

This research was carried out to find out the possibility of utilizing tire crumb rubber waste as fine aggregate in fly ash-based geopolymer mortars (GPMs). The effect of replacement of river sand with crumb rubber at the levels of 0, 25, 50, 75, and 100% by volume on the geopolymer mortar properties including workability, dry density, compressive strength, flexural strength, thermal conductivity, ultrasonic pulse velocity (UPV), water absorption, and porosity were studied. The results were compared to those of the Portland cement-based mortars (PCMs). The test results demonstrated that the higher crumb rubber content resulted in the less dense matrix of mortar. However, GPMs with crumb rubber resulted in a significant improvement in flexural strength. The average ratio of flexural to compressive strengths of GPMs was 25% compared to 15% of PCMs. Also, the lower dry density and thermal conductivity of GPMs indicated better insulating properties than those of PCMs.

Effect of Curing Conditions on Microstructure and Pore-Structure of Brown Coal Fly Ash Geopolymers

This study reports the effect of heat curing at 120 °C on the geopolymeric reaction and strength evolution in brown coal fly ash based geopolymer mortar and concrete. Moreover, an examination of this temperature profile of large size geopolymer concrete specimens is also reported. The specimen temperature and size were observed to influence the conversion from the glassy (amorphous) phases to the crystalline phases and the microstructure development of the geopolymer. The temperature profile could be divided into three principal stages which correlated well with the proposed reaction mechanism for class F fly ash geopolymers. The geopolymerisation progressed more rapidly for the mortar specimens than the concrete specimens with 12 to 14 h providing an optimum curing time for the 50 mm mortar cubes and 24 h being the optimum time for the 100 mm concrete cubes. The 50 mm and 100 mm concrete specimens’ compressive strengths in excess of 30 MPa could be obtained at 7 days. The structural integrity was not achieved at the center of 200 mm and 300 mm concrete specimens following 24 h curing at 120 °C. Hence, the optimal curing time required to achieve the best compressive strength for brown coal geopolymer was identified as being dependent on the specimen size.

Effect of the particle size range of construction and demolition waste on the fresh and hardened-state properties of fly ash-based geopolymer mortars with total replacement of sand

This study seeks the valorization of industrial residues (fly ash and construction and demolition waste (CDW)) through the production of geopolymer mortars. The effect of the sand substitution by CDW and the influence of the particle size range of CDW fine aggregates on the fresh and hardened properties of the mortars were evaluated. Geopolymer mortars were produced using biomass fly ash waste and metakaolin as a binder, CDW as fine aggregates, and an alkali solution of sodium silicate and sodium hydroxide as activator. The geopolymer mortars were characterized in fresh state by the flow table test and in the hardened state through chemical, physical/microstructural analyzes. The mortars produced with CDW showed lower flowability when compared to the ones prepared with sand. The compressive and flexural strength of hardened mortars, respectively, obtained with residues were higher when compared to sand: 40MPa and 8.5MPa with CDW, against 23MPa and 3.1MPa for sand-based samples. It was observed that mortars developed with recycled aggregate and natural aggregate present similar chemical and mineralogical compositions. The superior results obtained in the mechanical properties of mortars produced with CDW are related to the recycled aggregate-geopolymer paste interface.

Optimization of the design parameters of fly ash-based geopolymer using the dynamic approach of the Taguchi method

The dynamic approach of the Taguchi method is applied to optimize the mixture proportions and manufacturing conditions of fly ash-based geopolymer (FAGP) mortar using fly ash produced at two different thermal power plants in the Kyushu region, Japan. Ground granulated blast-furnace slag (GGBS) is also used as an activation powder. The design parameters of a system, with the volume ratio of powder to alkaline activating solution as the input value and the flow value as well as the flexural and compressive strengths as the output values, are optimized based on the calculation of the signal-to-noise ratio. As a result, optimum values for the mass ratio of sodium silicate solution to sodium hydroxide solution, concentration of sodium hydroxide solution, GGBS replacement ratio, mixing time, curing temperature, and cumulative temperature in heat curing are obtained. The values of the optimized design parameters are almost the same, regardless of the type of fly ash. The compressive strength of the optimized FAGP mortar ranged from 28.8 N/mm2 to 47.1 N/mm2 at 2 days, corresponding to the input values. Furthermore, it is confirmed that the optimized FAGP mortar has strength stability and sulfuric acid resistance up to 91 days sufficient for practical purposes.

Performance characteristics of micro fiber-reinforced geopolymer mortars for repair

Abstract Fiber reinforced geopolymer materials are recently being considered as prominent sustainable repair materials for concrete retrofitting/repair due to their good bonding properties. The addition of fibers to geopolymers materials may considerably improve their mechanical properties but they also effect on physical properties such as setting, workability, density, porosity. It is crucial to understand these characteristics of micro fiber reinforced geopolymer mortars before optimizing the micro fiber for geopolymer mortars for repair. In this study, the effects of micro fiber type and fiber volume fraction on the physical characteristics and on flexural behavior are investigated. In addition, the influence of different heat curing durations on the properties of micro fiber reinforced geopolymer mortars is also examined. Six types of micro fibers (high-strength steel, waste steel wool, polyvinyl alcohol, polypropylene, polyester & carbon) at low fiber volume fractions of 0.5%, and 1.0% are considered to study the physical properties (workability, and total porosity) and flexural behavior of fly ash-based geopolymer mortars. High strength steel fibers imparted the least change in workability whereas with polyester fibers the flow was the lowest. Porosity as well was highest for polyester fiber reinforced mortars followed steel wool and polypropylene. Significant improvements in the flexural behavior and compressive strength due to micro fiber reinforcement are noted particularly in steel and polyvinyl alcohol fibers. Deflection hardening was observed for mortars with 1% polyvinyl alcohol fibers, and for both 0.5% and 1% steel fibers. The overall flexural performance of polyester, steel wool, and carbon fibers reinforced geopolymer mortars was dismal. Increasing the duration of heat curing from 4 h to 24 had little change in total porosity and compressive strength. In flexural behavior however, the effect of prolonged heat curing was more noticeable.

Influence of some additives on the properties of fly ash based geopolymer cement mortars

In order to minimize CO2 emission due to manufacture of Portland cement, researches have been focused on alternative construction materials such as geopolymer cement. Geopolymer cement is made from waste materials such as fly ash by alkali-activation. This paper reports the properties of fly ash based geopolymer mortars activated by sodium hydroxide/potassium hydroxide and sodium silicate/lithium silicate. Alccofine powder, aluminum powder and calcined clay were added during geopolymerization. Curing was done at 80 °C. Compressive strength of geopolymer mortar was found maximum in the presence of potassium hydroxide–lithium silicate—5% alccofine powder—10% calcined clay. Durability of cubes in sulphuric acid was studied. Fire resistant properties of some of the mortars at 600, 800 and 1000 °C were also studied.

Abrasion resistance behaviour of fly ash based geopolymer using nanoindentation and artificial neural network

Abstract This study presents the investigation of the abrasion resistance of fly ash based geopolymer via the application of nanoindentation. Nine fly ash based geopolymer mixes with four variables: silica fume (SF), sand to cementitious ratio (s/c), liquid to solid ratio (l/s) and superplasticizer (SP) were investigated with statistical methods to obtain the plasticity index of the four fly ash based geopolymer phases. The results suggest that the pure fly ash based geopolymer paste with no SF, no SP, no sand and l/s ratio of 0.60 provides the highest abrasion resistance. Artificial neural network (ANN) is also adopted to predict the abrasion performance of the fly ash based geopolymer where good correlation is found. With the application of deconvolution method, it is reported that the plasticity index of N-A-S-H, partly activated slag and non-activated slag phases show a decreasing trend of plasticity index with increasing hardness or modulus. The non-activated compact slag phase shows no clear trend with changes in hardness and modulus. The relationship between degree of activation versus plasticity index (PI) is also studied, it was found that high degree of activation leads to formation of high volume fraction of N-A-S-H which this correlates with increased compressive strength and improved abrasion resistance. The application of nanoindentation with deconvolution method is suitable in quantifying the PI of the phases and abrasion resistance of the fly ash based geopolymer mortar.

Performance of Na2SiO3 solution fly ash based geopolymer mortar under ambient curing

The aim of this study is to investigate the effects of sodium silicate solution with varying concentrations on aluminosilicate- based geopolymer mortars. The total binder content of 600 kg m−3 is maintained in all the mix design. The sodium silicate solution with a modular ratio (SiO2/Na2O) of 2 had been used. The molarity of the sodium silicate solution varies in the region of 1 < M < 2.5. It can be observed from the test results that there is a significant effect of silicate solution on aluminosilicate based geopolymer under ambient curing. The mix FG2.5 with a high concentration (2.5 M) of Na2SiO3 solution had achieved 110 mm mortar flow with sticky mortar because of the high viscosity nature of solution which shows compressive strength of 46 MPa at 28-day. The geopolymer mortar mixes containing 2 M, 1.75 M and 1.5 M showed low viscosity mortar with a slight decrease in strength as compared to 2.5 M. The SEM and EDX analysis revealed that, with a high concentration of the solution, the geopolymer matrix was densely formed. However, the increase in the concentration of the solution resulted in, low micro cracks on the surface of the specimens at a magnification of 2 μm. The Si/Al ratio of all the mixes laid in between 3.37 to 4.1. Therefore, the concentration of the solution in the region 1.25 < M < 2 has shown the better results with consideration of mortar flow, compressive strength, and microstructural observation.

Workability and Strength Properties of Class C Fly Ash-Based Geopolymer Mortar

Fly ash-based geopolymer mortar normally achieves expected properties by heat curing. This becomes one of the obstacles for in-situ applications. The development of high calcium fly ash-based geopolymer mortar, suitable for ambient curing, will gain the applicability of such a material in civil structures. This article reports the results of an experimental study on mortar workability and the increasing of compressive strength of class C fly ash-based geopolymer mortar created in ambient curing condition. The main synthesis parameters such as alkali to the cementitious mass ratio varied from 30% to 40% by an increment of 5% and absolute volume of paste to absolute volume of voids of the aggregate ratio varied from 1 to 2 by an increment of 0.25. These parameters were designed to figure out their individual effects on mortar workability and the mechanical properties for the production of geopolymer mortar. The results suggested that the workability of mortar generally increased by using alkali to the cementitious mass ratio. The compressive strength of 60 MPa and the direct tensile strength of 2.8 MPa, the ratio of alkali to the cementitious mass of 0.35 and absolute volume of paste to absolute volume of voids of the aggregate ratio was 1.5; it was obtained at ambient temperature after 28 days of age. The results will be useful for developing the knowledge for the use of class C fly ash in producing geopolymer concrete, which is currently in progress. Hopefully, this contribution of research will improve the applications of such new binding material in the future.

Effect of Alkaline Concentration and Solid Liquid Ratio on the Acid Resistance of Fly Ash Based Geopolymer Mortar

Ordinary Portland cement (OPC) is one of the most widely used binders in building materials. However, OPC production is related with high CO2 emission and high energy consumption. Currently geopolymer cements are found to be the alternative substitute for OPC. Geopolymers most commonly are covalently bonded alkali-aluminosilicates which are X-ray amorphous at ambient and medium temperatures. The current study focusses on fly ash which is a byproduct of coal combustion process and due to its amorphous nature and chemistry, it is considered an appropriate raw material for geopolymer synthesis. In this study the effect of alkali concentration and solid liquid ratio on the acid resistance of fly ash based geopolymer mortar was studied. The fly ash was obtained from ayka Addis Textile, Addis Ababa, Ethiopia. Samples were prepared with different solid to liquid ratio and NaOH molarity and were tested for mechanical and durability properties. It was found that as the molarity of NaOH solution and solid to liquid ratio increase the initial and final setting time become shorter. Compressive and flexural strength show that after 28 days of curing sample with high Liquid to solid ratio and higher molarity show higher strength and smaller water absorption percentage. Sample were immersed in a 2% H2SO4 solution for 25 days and the sample with higher strength with smaller water absorption percentage show higher resistance.

Behaviour of Geopolymer Mortars after Exposure to Elevated Temperatures

In this study it was investigated the behavior of class F fly ash based geopolymer mortars subjected to elevated temperatures. Geopolimer composites were prepared with CEN-sand, water, fly ash as the binder, nSiO2Na2O and NaOH mixture combination as alkali activator. After mixing fresh geopolymer mixture, prismatic specimens were prepared using 40 mm × 40 mm × 160 mm prism molds. After molding, fresh geopolymer mortar samples with their mold were subjected to heat curing at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C and 100 °C temperature for 48 hours in an oven. After 48 hours initial heat curing, the hardened samples were taken out of their mold. Then, they were further cured by leaving them in laboratory environment at about 22 ± 2 °C temperature, until 28 days together with heat curing duration. At the end of 28 days, geopolymer mortar samples developed flexural strength values between 2,9 MPa and 8,51 MPa. Geopolymer mortar samples developed compressive strength values between 7,63 MPa and 50,64 MPa. High temperature experiments were conducted to observe behaviour of geopolymer mortars at elevated temperatures. The control cement mortar mixtures were also prepared and subjected to high temperature exposure in comparison to geopolymer mortar mixtures. Control cement mortars were cured at laboratory environment for 28 days without initial temperature curing. Control cement mortar mixtures and geopolymer mortar mixtures were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C temperature. The unit weight, ultrasonic pulse velocity, flexural and compressive strength of all mixtures were measured before and after high temperature exposure. Scanning electron microscope (SEM) images of the mixtures were taken and X-ray fluorescence (XRF) spectrometer analyses were carried out. It was observed that there was an increase in the flexural and compressive strengths of some geopolymer mortars after high temperature exposure. In general, geopolymer mortars exhibited better performance at elevated temperatures in comparison to control cement mortar mixture. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18829

Some Studies on Sustainable Utilization of Iron Ore Tailing (IOT) as Fine Aggregates in Fly Ash Based Geopolymer Mortar

This study presents the sustainable utilization potential of Iron Ore Tailings (IOT) as a replacement material against natural fine aggregates in the preparation of fly ash based geopolymer mortar. Low calcium fly ash is used as the source material and a mixture of sodium hydroxide and sodium silicate is used as the alkaline activator in the mix. Systematic studies such as setting times and compressive strength of the various mixes with different alkali binder ratio’s were investigated in detail. It is to be noted that setting times of the mixes were found to be increasing with the increase in alkali binder ratio (0.4 to 0.8). Alkali binder ratio of 0.6 is found to be the optimum with respect to the compressive strength, irrespective of the type of fine aggregate. Scanning electron microscopy also reveals that microstructure of the fly ash based geopolymer mortar produced had a dense matrix with utilization of the Iron ore tailing. It can be concluded from the study that IOT is found to be a best alternative against the natural sand as a fine aggregate.

Microstructure and strength development of fly ash-based geopolymer mortar: Role of nano-metakaolin

Geopolymer mortar is a novel binder material that exhibits the same properties as of cement. However, being a waste material geopolymer binder has an edge over cement binder because of environmental safety. This paper elucidates the fluctuations in compressive strength and microstructure of fly ash based geopolymer mortar using 14 M molar concentrations of alkali activator solution along with different replacement levels of nano-metakaolin (0%, 2%, 4%, 6%, 8% and 10% of fly ash). The mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) in the ratio of 1:2.5 was used as an alkaline activator solution. All the specimens were cured for 24 h temperature curing and tested after 3,7,14 and 28 days of ambient curing followed to temperature curing. Geopolymer mortar with 4% nano-metakaolin shows appreciable improvement in compressive strength at all curing ages. The phase composition and microstructure of fly ash based geopolymer incorporated with nano-metakaolin were investigated using scanning electron microscope (SEM) technique.

Alternation of traditional cement mortars using fly ash-based geopolymer mortars modified by slag

The use of local aluminosilicates to serve the local engineering applications could resolve the issue of unpredicted properties of the geopolymer caused by the wide variance in aluminosilicates reactivity. The locally available aluminosilicate byproducts (e.g., fly ash [FA] and granulated ground blast-furnace slag [GGBS]) in Qingdao were used to synthesize geopolymer cement in this study. Six geopolymer cement mortars with different FA/GGBS ratios were compared with ordinary Portland cement (OPC) and magnesium potassium phosphate cement (MKPC) mortars in terms of workability, setting time, strength development, volume stability and chloride permeability. The use of high volume of GGBS equips the geopolymer mortars with fast setting and high early strength despite poor volume stability. Thus, GGBS geopolymer mortars could potentially replace the high-cost MKPC mortar for rapid rehabilitation in construction. The geopolymer cement mortar with a FA/GGBS ratio of 4 behaves similar to OPC mortars in terms of fluidity, setting time, strength development, volume stability and chloride permeability. Therefore, FA-based geopolymer mortar blended with 20% GGBS could be considered as a high-efficiency, low-cost, eco-friendly and sustainable replacement of OPC mortar. Overall, the geopolymer cement properties could be engineered based on the FA/GGBS ratio in order to serve local engineering applications for the maximum utilization in different scenarios.

Properties of class F fly ash based geopolymer mortar produced with alkaline water

In this study class F fly ash based geopolymer mortar is produced with water containing an alkaline substance such as sodium bicarbonate (NaHCO3). Subsequently, compressive strength, density, absorption and porosity of the produced mortar mixture were tested after 28 days and compared with controlled geopolymer mortar produced with pure distilled water. A mixture of NaOH and Na2SiO3 solutions along with an elevated curing regime of 70 °C for 24 h was used to activate the geopolymerization process. The entire process involved in designing 21 mortar mixtures in 04 different batches by varying three processing parameters with different levels. The processing parameters and levels varied are as follows: Concentrations of sodium hydroxide solution expressed in molarity (10 M, 12 M and 14 M), the ratios of sodium silicate (Na2SiO3) to sodium hydroxide (NaOH) solution (1.0, 2.0 and 2.5) and varying concentrations of sodium bicarbonate (0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 7.5 g/L and 15 g/L) spiked in distilled water. A ratio of 3.0 fine aggregate to fly ash was kept constant for all mortar mixtures. Results indicated that with 12 M NaOH solution, 1.5 proportion of Na2SiO3 to NaOH solution, 1.0 g/L concentration of sodium bicarbonate in distilled water, geopolymer mortar of 41 MPa compressive strength with low porosity and good quality of mixture along with a low rate of absorption could be produced. Up to a concentration of 1.5 g/L of sodium bicarbonate in water is beneficial and higher levels are detrimental towards the properties of geopolymer mortar.