Geopolymer Concrete Samples Research Articles

Effect of Salt Solution on the Mechanical Behaviours of Geopolymer Concrete under Dry-Wet Cycles

Seawater splashing and frequent rainfall in the coastal area will often cause the concrete members to be affected by dry-wet cycles. In order to investigate the effect of salt solution on the mechanical behaviours of geopolymer concrete under dry-wet cycles, a series of tests on erosion of geopolymer concrete by three different salt solutions were carried out by using the mass loss rate, compressive strength, erosion resistance coefficient, and elastic modulus. The results show that, with the increase of dry-wet cycles, the mass of the specimen increases slightly at 20 dry-wet cycles and then decreases gradually. Then, the stress-strain curve of geopolymer concrete can be divided into three stages: linear growth stage, deceleration growth stage, and slow decline stage, which correspond to the elastic deformation stage, elastic-plastic deformation stage, and crushing stage, respectively. The overall trend of the stress-strain curve is similar under different dry-wet cycles, and the peak stress decreases with the increase of dry-cycle. The relationship between stress and strain of geopolymer concrete samples with different salt solutions is similar, while their strength characteristics have changed obviously. Furthermore, with the increase of dry-wet cycles, the compressive strength and the relative elastic modulus of geopolymer concrete gradually decrease, which reflects that sulfate erosion will lead to the strength loss of geopolymer concrete, causing its internal damage, thus having adverse effects on it. Different salt solutions have the great influence on the mass loss rate, compressive strength, erosion resistance coefficient, and elastic modulus of geopolymer concrete. In detail, the mixed salt solution erosion results in the greatest damage to geopolymer concrete and accelerates the damage. Chloride salt solution erosion causes middle damage to geopolymer concrete. Compared with the other two salt solutions, sulfate solution erosion leads to the least damage to geopolymer concrete and then sulfate has a certain inhibitory effect on the damage of geopolymer concrete. In addition, based on the test results, the constitutive model considering dry-wet cycles damage of salt solution is proposed, and the correctness is verified. This study has a good guiding value for geopolymer concrete engineering in coastal areas.

Performance of glass powder substituted slag based geopolymer concretes under high temperature

Geopolymer concretes provide advantages in terms of recycling waste materials. Geopolymer concretes are advantageous in terms of both limiting the use of Portland cement and recycling waste materials. In this study, 5 different geopolymer concrete mixture groups were prepared by replacing slag with 0.5%, 10, 15 and 20% by weight glass powder (GP). Geopolymer concrete samples prepared by using 12 M sodium hydroxide solution as an alkali activator were cured in the laboratory environment. The samples, which completed their curing periods, were kept at 150, 300, 450, 600 and 750 °C temperatures for 1 h. Compressive strength, weight change and sorptivity values of these samples were determined. These results were interpreted together with the visual inspections and microstructure analyzes (SEM and EDS) of the samples. As the GP substitution rate increased, the mechanical properties of geopolymer concretes decreased. However, GP improved the performance of geopolymer concretes exposed to high temperatures. Cooling in air affected the samples less negatively than cooling in water. While the Ca/Si ratios of the samples decreased at 450 °C and above, the Si/Al ratio increased.

Materials characterization of various lunar regolith simulants for use in geopolymer lunar concrete

Concrete materials are a feasible option for construction on the Moon utilizing the in-situ resources. An important part of any concrete material is the proper characterization of the raw materials to inform the mixture design and allow for interpretation of the end properties. Since lunar regolith simulants are the only near-term option for progressing the creation of a concrete material out of the lunar materials, it is important to use multiple simulant manufacturers to gain a well-rounded knowledge. In this study, five different lunar regolith simulants were characterized in detail and the data was used to create geopolymer concrete samples for compressive strength testing and subsequent microstructure analysis. Characterization results were also compared to available Apollo missions’ sample data and discussed in terms of geopolymer lunar concrete. The 28-day compressive strength of the samples varied from 2653 psi to 7809 psi depending on the type of lunar regolith simulant. The lunar regolith simulants proved feasible for such concrete technology but exhibit variability due to their mineralogy, amorphous (glass) content, and particle size and shape distributions.

APPLICATIONS OF DUYEN HAI - 1 THERMAL POWER PANT’S FLY ASH AND HOA PHAT STEELMAKING PLANT’S BLAST FURNACE SLAG IN GEOPOLYMER CONCRETE FABRICATION

Currently, non-cement alkaline activated concretes, using fly ash instead of conventional cement binder, have been widely used in construction around the world. However, in Viet Nam researches on geopolymer concretes are still very limited. Meanwhile, coal-fired thermal power plants in Viet Nam annually generate about 13 million tons of fly ash, potentially causing environmental pollution. Therefore, the use of these raw materials for concrete making not only minimizes environmental pollution but also avoids wasting resources. This paper presents study results on the mechanical properties of geopolymer concrete using fly ash of the 1,245 MW Duyen hai - 1 thermal power plant and blast furnace slag of Hoa Phat steelmaking plant. The suitable ratio of liquid glass/NaOH used in this study was about 3.7. At this value, the compressive, flexural and tensile strengths of the geopolymer concrete have reached 43.2 MPa, 6.62 MPa and 87,780 N, respectively. In addition, geopolymer concrete samples were impervious and their mechanical properties were almost unchanged after soaking in various solutions for a period of 4 months. Furthermore, interlocking blocks were fabricated from this geopolymer concrete (with the same composition as sample M6), based on the TCVN 9901:2014 standard on Hydraulic structures and Requirements for sea dike design. These blocks were used to reinforce the sea dike against this year’s typhoon season in central Viet Nam. The success of this project greatly contributes to the effective application of fly ash and reducing environmental pollution.

Investigating mechanical characteristics of geopolymer concrete under the influence of Nano-fillers

The mechanical characteristics of a geopolymer-based cementitious materials (GeoPC) are examined in this study to see how varying amounts of nano-titania (TiO2) affect their compressive, tensile and flexural characteristics. Geopolymer concrete (GeoPC) mixtures with four distinct nano-titania fractions (0, 1, 2, and 4) were developed to meet this objective.The ground granulated blast furnace slag (GGBFS) had been employed in the preparation of (GeoPC) mixtures and they were cured at room temperatures with an alkaline activator/binding material ratio of 0.51. The influence of nano-titania blending fraction on GeoPC samples' performance were determined by conducting hardened concrete testing using splitting tensile, flexural, and compressive strength investigations. The findings showed that the mechanical characteristics of GeoPC specimens were significantly improved by utilising a mixture containing the optimal amount of nano-titania (2%) in comparison to all other combinations. The corresponding improvement in splitting tensile, compressive and flexural strengths were observed as 25.26%, 37.04%, and 37.58%, respectively improved for the GeoPC after one week curing period in the presence of nano-titania.

Comparative study on mechanical properties of fly ash & GGBFS based geopolymer concrete and OPC concrete using nano-alumina

Nanomaterials, which are inferable from their exceptional properties, are known to enhance the microstructure of concrete, upgrades the fresh and strengthened state characteristics of cement concrete, and are broadly utilized in cementitious ingredients. The primary goal of this investigation is to compare the mechanical properties of geopolymer concrete (GPC) based on fly ash (FA) and ground granulated blast furnace slag (GGBFS) to that of ordinary portland cement concrete using Nano-Alumina. The Nano-Alumina particles are added to the GPC and OPC concrete at dosages of 1%, 2%, and 3% by weight of the binder, respectively, and the counterparts of the same test samples without Nano-Alumina are prepared. All the Geopolymer concrete samples were cured at room temperature and had a consistent liquid/binder ratio of 0.48. The current study also proposed using Quartz and Feldspar (QF-mineral sand) as fine aggregate in all the mixtures due to the natural depletion of river sand. The experimental results reveal that inclusion of 2 wt% Nano-Alumina particles was optimal for increasing the mechanical properties of OPC concrete and GPC.

Mechanical and Electromagnetic Properties of Self-Compacted Geopolymer Concretes With Nano Silica and Steel Fiber Additives

Mechanical and electromagnetic properties (over 2-16 GHz) of self-compacted geopolymer concrete (SCGC) samples with different amounts of nano-silica (NS) and steel-fiber (SF) have been examined. From the mechanical tests, it is observed that while the amount of NS added to SCGC samples does not make any noticeable change in compressive strength and modulus of elasticity values, an increase in amount and/or aspect ratio of SF additives improves these values. From the electromagnetic tests, it is noted that the effect of SF on reflection properties of SCGC samples is relatively smaller than the effect of NS. Besides, while incorporation of NS improves the resonance characteristics of transmission properties, additives of SF decreases these properties over the entire frequency band. Finally, the sample C7, which has 1% SF with a smaller diameter and 2% NS in reference to the mass of binder, has the optimum NS and SF additives, producing maximum absorbance values.

Developing Environmentally Sustainable and Cost-Effective Geopolymer Concrete with Improved Characteristics

Improving the efficiency and quality of construction mainly depends on the cost of building materials, which is about 55–65% of total capital-construction costs. The study aimed to obtain geopolymer fine-grained concrete with improved quality characteristics that meet the construction field’s sustainable development criteria and that have environmental friendliness, economic efficiency, and advantages over competing analogues. The dependences of strength characteristics on various compositions of geopolymer concrete were obtained. It was found that the most effective activator is a composition of NaOH and Na2SiO3 with a ratio of 1:2. The increase in the indicators of the obtained geopolymer concrete from the developed composition (4A) in relation to the base control (1X) was 17% in terms of compressive strength and 24% in tensile strength in bending. Polynomial equations were obtained showing the dependence of the change in the strength characteristics of geopolymer concrete on the individual influence of each of the activators. A significant effect of the composition of the alkaline activator on the strength characteristics of geopolymer fine-grained concrete was noted. The optimal temperature range of heat treatment of geopolymer concrete samples, contributing to the positive kinetics of compressive strength gain at the age of 28 days, was determined. The main technological and recipe parameters for obtaining geopolymers with the desired properties, which meet the ecology requirements and are efficient from the point of view of economics, were determined.

Behavior of geopolymer concrete deep beams containing waste aggregate of glass and limestone as a partial replacement of natural sand

The geopolymer concrete has outstanding physical properties and positive impact on environment compared to conventional concrete. Present endeavor highlights a strategy for management of glass and limestone waste to recycle them in geopolymer concrete deep beams. In this study, 126 geopolymer concrete samples were made for investigating the mechanical properties of geopolymer concrete with the sand replacement ratio of 0–15% by weight in increments of 5%. In addition, seven Reinforced geopolymer concrete deep beams of 600,150,150 mm were casted with respect to the concrete mix and their performance was examined in four-point bending test as per ASTM C78/C78M considering sand replacing ratio of 0–15%. Moreover, proper material constitutive relationships were selected to simulate the performance of geopolymer concrete incorporating waste aggregate. Consequently, a nonlinear finite element solution in ANSYS 11.0 was developed using these constitutive models to predict the behavior of beams. Experimental observations revealed that the use of waste lime and waste glass aggregates reduced the compressive and tensile strength of geopolymer concrete. Furthermore, the loss in strength using waste glass aggregate was less than 15% when compared to geopolymer concrete with waste limestone. Whereas, 5–15% sand replacing with waste aggregate resulted in an average reduction of 19% in loading capacity of the deep beams. The degradation in the ultimate load of the beams with limestone aggregate was 46.6% lower than that for members containing waste glass aggregate. The strain energy of the deep beams containing waste limestone was enhanced by increasing the waste aggregate content from 5% to 15%. Whilst increasing the ratio of replacement for glass mixes led to a decrease in final compressive strain. The outputs of the numerical analysis, in terms of loading capacity of the geopolymer concrete deep beams, were in good matching with the experimental results.

Compressive Strength Prediction of Ferrochrome Slag Based Geopolymer Concretes Produced Under Different Curing Conditions by Using Prediction Methods

In this study, compressive strength (CS) values of ferrochrome slag (FS) based geopolymer concretes in different curing conditions were investigated. Ground FS was activated with the mixture of sodium hydroxide and sodium silicate. The silica modulus (Ms) of the geopolymer concrete samples were selected as 1.25, 1.50 and 1.75. Also, samples were prepared by substituting 0%, 10% and 20% silica fume (SF) replacement the FS. Thus, 9 groups geopolymer concrete samples were produced. The CS values of the samples were determined on different curing times (24, 48, 72 and 96 hours) and curing temperatures (23, 40, 60, 80 and 100 °C). At the same time, multilayer perceptron neural network (MLPNN), extreme learning machine neural network (ELMNN) and M5 model tree were modeled for the CS prediction of the samples, the predict and experimental results were compared. According to the experiment results, it was determined that the CS values generally increased as the curing time increased, but with the addition of SF, the CS values generally decreased. The highest CS was obtained in the sample containing 100% FS that had silica modulus of 1.25 and cured at 100 °C for 24-48-72 or 96 hours. The R2 values of MLPNN, ELMNN and M5 model tree in testing phase were 0.956, 0.935 and 0.922, respectively. MLPNN, the model that gave the best predict result, had root mean square error (RMSE) of 0.723 and normalized root mean square error (NMRSE) of 26.485 in testing.

Effect of elevated temperatures on mechanical properties of lightweight geopolymer concrete

This study aims to examine the effect of high temperatures on lightweight geopolymer concrete (LWGC) and lightweight ordinary concrete (LWOC) made of natural pumice and lightweight expanded clay aggregate (LECA) with the addition of trapped air. To this end, a geopolymer concrete matrix has been synthesized by the alkali-activation of fly ash (FA) and granulated blast furnace slag (GBFS). The geopolymer concrete samples were cured for 24 h at a temperature of 80 °C. To study the properties of fresh concrete, slump and slump flow tests and unit weight were applied. The mechanical properties were also measured by the compressive strength, splitting tensile, flexural strength, and elastic modulus tests. High temperatures of 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C were applied on the geopolymer concrete samples to obtain the residual compressive strength. In general, pumice and LECA can be used as an alternative to the dolomite aggregate to produce LWGC and LWOC. The mixture F-50D50P-A achieved the lowest of unit weight of 1660 kg/m, a slump flow of 555 mm, and compressive strength of 32.9 MPa at 91-days. Lightweight geopolymer concrete containing 50 % fly ash and 50 % GBSF achieved the best compressive strength test results. The results showed a similarity in the behaviour of LWGC with LWOC under the influence of all the variables applied in this study.

Improving elevated temperature performance of geopolymer concrete utilizing nano-silica, micro-silica and styrene-butadiene latex

Geopolymer binders (GPBs) have gained an increasing research potential in recent years due to their environmental, economic and durability advantages. This paper aims to improve elevated temperature performances of volcanic tuff (VT) based geopolymer concrete (GPC) by utilizing nano-silica (NS), micro-silica (MS) and styrene-butadiene latex (SBL). To this end, NS, MS and SBL additives were added to GPC samples at 2%, 2% and 5% ratios by weight of binder, respectively. GPB was obtained by activating ground VT with 12 M NaOH solution. Produced GPC samples were exposed to elevated temperatures (100, 300, 500 and 700 °C) for 1 h after reaching the target temperature. Changes in compressive strength, water absorption, visual appearance, weight and microstructure of GPC samples were investigated after the influence of elevated temperatures. The experimental findings displayed that compressive strength of GPCs increased up to 300 °C independently of the type of additive used, but higher temperatures than 300 °C caused decrease in compressive strength values. As a result of mechanical tests and microstructure investigations, it was determined that MS additive significantly increased the elevated temperature performance of GPCs. Additionally, color of GPC samples turned gray after elevated temperatures due to dehydration of GPB and microstructural transformations occurring in aggregates.

Effect of Liquid to Binder Ratio and Curing Temperature on the Engineering Properties of the Geopolymer Concrete

Geopolymer concrete(GPC) is a perfect alternative to conventional cement concrete. This experimental investigation examines the physical properties, chemical properties, mechanical properties, non-destructive test, and microstructural analysis of the various geopolymer concrete samples, varying the liquid-to-binder(LBR) ratio from 0.40 to 0.70, and curing temperature from 60 °C to 120 °C. After the experimental investigation, the workability increases with the increment of the liquid-to-binder ratio in the design mix, but the mix specimen density decreases with the same. In the mechanical properties, the compressive strength optimum at the ratio of 0.60 of liquid-to-binder ratio, and the poisson’s ratio increases with the increment of liquid to binder ratio from .14 to .18 consecutively. All the mixes mechanical properties got the optimum point at the ratio of 0.60 of LBR in both ambient and oven curing conditions. The curing temperature directly increases the gain strength rate at early ages, but it reduces beyond the 100 °C temperature. The drying shrinkage increases with the increment of curing temperature, similarly the modulus of elasticity increase with the increment of curing temperature, but it reduces beyond the 100 °C curing temperature. The thermal stability of the GPC specimens is higher and shows the weight remained up to 92% of the original at the 850 °C temperature.

Experimental study on metakolin and baggashe ash based geopolymer concrete

In this experimental study, the bagasse ash and metakaolin is used to develop the geopolymer concrete. The fly ash based geopolymer concrete was prepared with bagasse ash and metakaolin which were used to replace fly ash at different percentages i.e., 10%, 20%, 30%, and 40% to study the microstructure, mechanical and durability properties. Geopolymer Concrete was prepared with the use of alkaline solutions NaOH and Na2Sio3. Geopolymer concrete samples for bagasse ash and metakaolin based were cured at oven for 24 h at 90˚C and then kept under room temperature for curing. Metakaolin contained geopolymer concrete has shown better mechanical and durability properties as compared with bagasse ash contained geopolymer concrete. Geopolymer concrete is raw material based concrete that leads to the usage of materials which are produced as a raw material from industries and when these raw materials were induced in the geopolymer preparation it leads to the reduction of carbon emissions and acts as a greener concrete towards environment. Microstructure studies concluded that the metakaolin contained geopolymer concrete has denser intermolecular bonding of materials as compared to the bagasse ash contained geopolymer due to which metakaolin shows better results in mechanical and durability properties when compared with bagasseash.

Durability and leach-ability evaluation of K-based geopolymer concrete in real environmental conditions

Geopolymer Concrete (GPC) as an alternative to Portland Cement Concrete (PCC) is a cement-less and green construction material which is produced by mixing industrial by-products with an alkaline solution. In this study, PCC and Potassium-based (K-based) GPC synthesized with 50 % fly-ash and 50 % bottom-ash were exposed to the real environmental conditions to evaluate their chemical metals leach-ability and durability over 150 and 240 days of exposure respectively. The mix contained potassium hydroxide concentration of 12 molarity, potassium silicate/potassium hydroxide ratio of 1.47, alkaline solution/ashes (fly-ash and bottom-ash) ratio of 0.54 and total aggregate content of 1800 kg/m3. To develop GPC, two methods of curing (steam curing and dry curing) were used to increase the compressive strength of GPC. According to the result of compression test, the compressive strength of steam-cured GPC increased 3.5 times when temperature elevated from ambient temperature (̴10 °C) to 80 °C. While, an increase in compressive strength of dry-cured GPC samples was 2.3 times. Non-Destructive Tests (NDT)s including Schmidt hammer, ultrasonic pulse velocity and resonant frequency test were employed to measure the relative dynamic modulus of elasticity. In this study, paver block has been selected as an application since to the best of our knowledge, there is no work reported the effect of real environmental conditions on leach-ability and mechanical properties of K-based GPC paver blocks. Two areas were paved with a total of 150 GPC and 210 PCC paver blocks. The results of the NDTs in area 1 show that the average velocity and compressive strength of GPC decreased approximately 11.6 % and 23.4 % respectively. While, the average velocity and compressive strength of PCC decreased about 8.3 % and 8.2 % respectively. In area 2, the average rate of velocity and compressive strength loss of GPC was about 12.03 % and 19.51 % respectively. Whereas, maximum decrease in average velocity and compressive strength of PCC over 240 days of exposure was 5.28 % and 9.65 % respectively. Leach-ability of GPC as another innovative aspect of current study was also measured using HACH strips since the release of heavy metals can be a concern in GPC. The results indicate that due to the heat-treatment of GPC paver blocks, all the parameters including total alkalinity, total hardness, pH, total chlorine, phosphate, copper, ammonia, iron, nitrate and nitrite were within the standard domain and were constant over 150 days of exposure. The relative dynamic modulus of elasticity power function model and exponential function model were established to find a suitable damage predictive model for both types of concrete. It was concluded that due to the higher values of Adj.R2 for both GPC (0.96) and PCC (0.92), the power function relationship compared well with the exponential function.

Influence of nano TiO2 on strength and durability properties of geopolymer concrete

Geopolymer concrete (GPC) is treated as an ecologically pure construction material because cement is completely retrieved by pozzolanic materials that are abundant in alumina and silica. GPC is actuated with alkaline liquids to begin as a binder in concrete. Geopolymer concrete evince many outstanding properties just as rapid strength, less shrinkage, and less creep, better resistance against sulphate and chloride attacks. The current review is to explore the effect of nano titanium dioxide (nano-TiO 2 ) on fly ash based geopolymer concrete (FAGPC) with oven curing at 60 0 c for 48 hrs. As an initial study, GPC with 10 M was carried out for dissimilar ratios of sodium silicate (Na 2 SiO 3 ) to sodium hydroxide (NaOH) solutions between 1.5 and 3.5. Out of all mixes, alkaline activator ratio harmonize to the highest compressive strength was ascertained at 2.5. This ratio was kept constant for further study in GPC carried out by replacing fly ash with nano TiO 2 between 1% and 5%. For all mixes of GPC with and without nano titanium dioxide, mechanical and durability properties were observed and evaluated. The test results depict that, percentage increase of nano TiO 2 , gives rise to decline in workability and improves strength properties of concrete. The maximum strength enrichment was noticed when 5% of nano-TiO 2 was incorporated in GPC. As percentage of nano TiO 2 hiked in GPC, the results of RCPT, Water absorption and Sorptivity decreased. All these GPC specimens are immersed individually in 5% magnesium sulphate and 5% sodium chloride to know the resistance of geopolymer concrete against sulphate and chloride attacks. Results of this study concluded that increase in nano TiO 2 percentage gives better performance against sulphate and chloride solutions. Change in microstructure and mineral phases of reference geopolymer concrete samples and maximum strength obtained geopolymer concrete samples containing nano TiO 2 was investigated using SEM and XRD analyses.

Production of lightweight geopolymer concrete

Lightweight concrete has been known all around the world for decades. As a masonry material, there is an advantage: it has sufficient mechanical strength despite of its light weight. This research focuses on the production of recycled concrete based lightweight geopolymer concrete samples using glass foam aggregates. During the research geopolymer and concrete samples were made and finally their properties were investigated and compared. In the research work an alkaline silicate reaction (ASR) was also studied on the glass foam lightweight aggregates, which is very important for concrete failure. Material structural and morphological tests were obtained by scanning electron microscopy (SEM) to characterize the geopolymer concrete samples. Compressive strength of lightweight concrete and lightweight geopolymer was determined at the age of 7 days. Glass foam is suitable for use as a lightweight aggregates for workability. Based on the 7 days compressive strength results no crust typical of the ASR reaction was detected on the surface of the mixtures.

Influence of activator solution on microstructural and mechanical properties of geopolymer concrete

Geopolymer Concrete (GC) is an innovative and Eco-friendly construction material and an alternative to Portland cement concrete. The binders such as fly ash, Ground Granulated Blast Furnace Slag (GGBS), and cement used to produce GC in this research work. These binders activated through two types of solutions (an alkaline solution which prepared in the laboratory and activator solution purchased commercially). An attempt has made to observe the advantages of commercially available activator solutions on properties of GC. The test results of laboratory prepared alkaline solution based GC specimens compared with commercially available activator solution based GC. The mechanical properties were investigated with 20% and 30% addition of GGBS and cement to fly ash based GC samples. Besides, the analysis of the specimen through SEM and EDS indicated that the components having a considerable influence on the structure of the GC were the Al and Si components. The XRD results revealed that there were no practical differences in the intensity according to the differences in the chemical elements of the alkaline/activator solutions. However, the TG/DT analysis made it possible to identify changes in mass loss of different proportions based GC. The alkaline solution based mixes attained enhanced mechanical properties compared to activator solution based GC samples. The microstructural studies revealed the reasons behind the strength improvement of fly ash-GGBS based GC.

Optimization of production parameters of geopolymer mortar and concrete: A comprehensive experimental study

Geopolymers are a new type of material offered as an alternative to traditional Portland cement. Geopolymers, produced by activation of natural and waste pozzolans with alkali activators such as NaOH (SH) and Na2O·3SiO2 (SS) solutions, have been widely supported and investigated due to environmental and economic advantages. In this study, a detailed experimental program was conducted to investigate the influence of activator type, activator concentration and curing temperature on mechanical and microstructural properties of volcanic tuff based geopolymer mortar (GPM) and concrete (GPC) samples. A total of 1080 GPM and GPC samples were produced and a number of parameters were investigated with 360 combinations. Maximum compressive strength was obtained as 37.09 MPa in 90-day samples in which the SH concentration was 16 M, activator/binder (a/b) ratio was 0.45 and the curing temperature was 120 °C. As a result of optimization of the production parameters, a considerable development in mechanical and microstructural properties of GPM and GPC samples was obtained. Experimental results demonstrated that alkali activation with sole SH bring about superior characteristics compared to alkali activation with SH + SS. Higher a/b ratio led to higher UPV values because of more dense and compact microstructure resulting from increase in gopolymerization reactions. This is also supported by compressive strength and microstructure findings.

Effects of Seawater Content in Alkaline Activators to Engineering Properties of Fly Ash-Based Geopolymer Concrete

This paper illustrates a special investigation on geopolymer concrete synthesized from fly ash, sand, coarse aggregates (solid phases) in conditions of sodium silicate solution and seawater (liquid phases). The mixtures of geopolymer concrete were designed with proportion changes of among materials to evaluate effects of the proportions to engineering properties of products. The specimens were molded into cylinder with 200 mm in length and 100 mm in diameter, and then cured at room condition (28 °C, 80 % of humidity) for testing engineering properties for 7 days, 28 days, 90 days, and 180 days. The engineering properties of geopolymer concrete samples included compressive strength (MPa), water absorption (kg/m3), and volumetric weight (kg/m3). The results showed that the fly ash-based geopolymer concrete using sodium silicate solution and seawater was very good performance with value of 180 day-compressive strength at 58 MPa, water absorption and volumetric weight were at 180 kg/m3 and 2200 kg/m3, respectively.