Geopolymer Concrete Mix Research Articles

Evaluation of fly ash-based geopolymer concrete incorporating coarse and fine recycled aggregates

Geopolymer Concrete (GC) is emerging as a promising material due to its lower carbon footprint compared to conventional Portland Cement (PC) concrete. One of the ways to further enhance the sustainability of GC is by incorporating Recycled Aggregates (RA). This study focuses on evaluating the performance of GC made with Coarse Recycled Aggregate (CRA) and Fine Recycled Aggregate (FRA). The mechanical property in terms of compressive strength and long-term durability properties, such as the Capillary Suction Test (CST), Initial Surface Absorption Test (ISAT), and acid attack test, were evaluated for all GC mixes. Ultrasonic Pulse Velocity (UPV) test and the electrical resistivity test, have also been done on all GC mixes. The results show that FRA beyond 25%, along with 50% CRA, is having an adverse impact on the long-term durability properties of GC. The GC mix with a combination of 50% CRA and 25% FRA shows at par compressive strength and electrical resistivity values relative to the Natural Aggregates (NA) GC. The findings from this study are expected to provide valuable insights into the optimal use of RA in GC and contribute to the broader goal of developing sustainable construction materials.

Influence of alkaline activators on mechanical properties of environmentally friendly geopolymer concrete under different curing regimes.

Previous studies highlighted the significance of tailoring alkaline activators (AA) to specific fly ash (FA) sources for optimal properties of geopolymer concrete (GPC). This study examines the influence of various AA's properties on mechanical properties and microstructures of local low-calcium FA-based GPC under varying curing conditions. A comprehensive investigation consists of several factors such as NaOH molarities (10M, 12M, 14M, 16M), ratios (1.5, 2.0, 2.5) and ratios (0.5, 0.6). The results reveal a complex relationship, demonstrating that NaOH molarity positively influences compressive strength up to a threshold of 14M, beyond which an adverse effect was observed while, the flexural strength was increased up to 16M. Moreover, the study highlights the complex relationship between ratios and mechanical strengths. Notably, these properties exhibited an increase as the ratio rose up to 2.0, but a subsequent decrease was observed when the ratio reached 2.5. Moreover, proposed regression equations predict the compressive and flexural strengths of both ambient-cured GPC and heat-cured GPC with marginal statistical errors. The optimal GPC mix exhibited 49% lower embodied emissions than the corresponding OPC concrete. GPC has higher cost, but it exhibited lower cost-to-strength ratio compared to OPC concrete.

Harnessing explainable Artificial Intelligence (XAI) for enhanced geopolymer concrete mix optimization

Geopolymer concrete (GC) emerges as a sustainable alternative yet faces challenges in achieving optimal resource utilization for strength development. Balancing these aspects is crucial for its large-scale adoption as a sustainable material. The type and dosage of precursors, activator, curing, and mixing conditions influence compressive strength, setting time, and workability. Moreover, multiple experimental trials are required for a desirable geopolymer blend. Even the experimental parameters alone do not meet the design principles concerning sustainable construction. This paper presents a study on the mix design and interpretation of machine learning techniques (MLT) with XAI. To train the model, extensive experimental databases using the shapley additive explanations (SHAP) technique rank input factors that impact the strength aspect. The prediction models' performance was compared using coefficient of determination (R2) and root mean square error (RMSE). SHAP interpretations reveal that temperature, Na to Al ratio, and NaOH molarity are the main factors influencing the compressive strength of GC. Further, these parameters were crucial in developing the dense geopolymer matrix. By integrating XAI into the MLT approach, we have also opened new criteria for understanding the complex relationships between geopolymer concrete potential parameters and their compressive strength.

An innovative approach to fly ash-based geopolymer concrete mix design: Utilizing 100 % recycled aggregates

Concrete is a widely used construction material globally, known for its ability to incorporate substantial quantities of industrial by-products such as fly ash (FA) and construction and demolition (C&D) debris. These by-products, originating from thermal power plants and construction activities, often pose environmental challenges when disposed of improperly. To address this issue, recycled aggregate geopolymer concrete (RAGPC) has emerged as a promising solution. However, the lack of a suitable mix design method has hindered the structural application of RAGPC. This study aims to introduce a novel mix design method utilizing 100 % recycled aggregate (RA) combined with FA through geopolymer technology, offering a simpler and more rational approach than previous methodologies. The proposed approach was validated through various concrete tests, utilizing a sodium silicate to sodium hydroxide ratio of 1.5 and a concentration of sodium hydroxide of 16 M as alkaline activation content (AAC), with an AAC to binder (B) ratio ranging from 0.3 to 0.8. Results indicate that incorporating FA and RA into concrete, coupled with elevated curing at 60 °C for 24 h for RAGPC hardening, yields compressive strengths (CS) ranging from approximately 14 to 35 MPa after a 28-day curing period. SEM and XRD tests were also conducted to analyse the polymerization processes, revealing the significant positive influence of FA on RAGPC performance. The findings suggest that fly ash has a superior synergistic influence on recycled aggregate geopolymer concrete performance. Moreover, due to its excellent resistance to chloride ingress and seawater corrosion, geopolymer concrete is well-suited for marine applications, including the construction of ports, harbours, offshore platforms, and coastal protection structures.

Proposed simplified methodological approach for designing geopolymer concrete mixtures

The development of geopolymer concrete offers promising prospects for sustainable construction practices due to its reduced environmental impact compared to conventional Portland cement concrete. However, the complexity involved in geopolymer concrete mix design often poses challenges for engineers and practitioners. In response, this study proposes a simplified approach for designing geopolymer concrete mixtures, drawing upon principles from Portland cement concrete mix design standards and recommended molar ratios of oxides involved in geopolymer synthesis. The proposed methodology aims to streamline the mix design process while optimizing key factors such as chemical composition, alkali activation solution, water content, and curing conditions to achieve desired compressive strength and workability. By leveraging commonalities between Portland cement concrete and geopolymer concrete, this approach seeks to facilitate the adoption of geopolymer concrete in practical construction applications. The proposed mix design guidelines have been validated through examples for concrete cured under different conditions, including outdoor and oven curing. Future research should focus on validating the proposed methodology through experimental studies and exploring cost-effective alternatives for alkali activation solutions to enhance the feasibility and scalability of geopolymer concrete production. Overall, the proposed simplified approach holds promise for advancing the utilization of geopolymer concrete as a sustainable alternative in the construction industry.

Characterization of geopolymer composites for 3D printing: a microstructure approach

Given the importance of geopolymer in terms of 3D printing performance and the scarcity of information on the subject, as well as previous research findings, the purpose of this study is to propose a design methodology for geopolymer concrete mix that can be used in the 3D printing process by studying the effect of fine aggregate size and type, binder type (either slag or metakaolin) and ratio (slag/metakaolin), and alkaline solution amount and ratio (NaOH/Na2SiO3). The study concluded that MK has lower fluidity than BFS under the same conditions that used the same amount of SP. However, it can be improved by adding slag. The best dosage was chosen, which is 50% MK and 50% BFS. Because of these proportions, the mixture is very dense, homogeneous and compact, which increases its microstructure analysis behavior.

Effect of Iron Ore Tailings and High Magnesium Nickel Slag on Flyash - Ggbs Based Geopolymer Concrete (GPC)

Abstract: The cement industry is a major producer of carbon dioxide (CO2), a powerful greenhouse gas which contaminate the environment by emitting massive volumes of CO2. The building sector contributes both directly and indirectly to environmental degradation, natural resource depletion, and global warming. From a sustainability standpoint, it is critical that cement manufacturing be reduced. Geopolymer concrete (GPC) is a new material that does not require portland cement as a binder, instead, materials rich in Silicon (Si) and Aluminum (Al), such as Flyash (FA) and Ground granulated blast furnace slag (GGBS) are activated by alkaline liquids to produce the binder. The use of iron ore tailings (IOT) in place of traditional aggregates in concrete has been discovered to be feasible. Concrete made using IOT aggregate performed well with respect to strength and durable studies. GPC mix of 12M was prepared using FA, GGBS, aggregates, alkaline alkali activators such as Sodium hydroxide (NaOH) and Sodium silicate (Na2SiO3). A study on using iron ore tailings (IOT) in replacement of fine aggregates in percentages of 20, 30, 40 and 50 are studied in GPC. After achieving optimum strength in above mix then high magnesium nickel slag (HMNS) was replaced with varying percentages 5, 7.5, 10 and 12.5. As alkaline activators with 12M NaOH and Na2SiO3 solutions are used with a ratio of 2.5. Mechanical properties such as Compressive, Split tensile and Flexural strength are evaluated to determine the influence of IOT and HMNS replacement in GPC.

Mechanical Properties of Rubberised Geopolymer Concrete.

The environmental impact of non-biodegradable rubber waste can be severe if they are buried in moist landfill soils or remain unused forever. This study deals with a sustainable approach for reusing discarded tires in construction materials. Replacing ordinary Portland cement (OPC) with an environmentally friendly geopolymer binder and integrating crumb rubber into pre-treated or non-treated geopolymer concrete as a partial replacement of natural aggregate is a great alternative to utilise tire waste and reduce CO2 emissions. Considering this, two sets of geopolymer concrete (GPC) mixes were manufactured, referred to as core mixes. Fine aggregates of the core geopolymer mixes were partially replaced with pre-treated and non-treated rubber crumbs to produce crumb rubber geopolymer concrete (CRGPC). The mechanical properties, such as compressive strength, stress-strain relationship, and elastic modulus of a rubberised geopolymer concrete of the reference GPC mix and the CRGPC were examined thoroughly to determine the performance of the products. Also, the mechanical properties of the CRGPC were compared with the existing material models. The result shows that the compressive strength and modulus of elasticity of CRGPC decrease with the increase of rubber content; for instance, a 33% reduction of the compressive strength is observed when 25% natural fine aggregate is replaced with crumb rubber. However, the strength and elasticity reduction can be minimised using pre-treated rubber particles. Based on the experimental results, stress-strain models for GPC and CRGPC are developed and proposed. The proposed models can accurately predict the properties of GPC and CRGPC.

Full-scale static behaviour of prestressed geopolymer concrete sleepers reinforced with steel fibres

Profusive cracking leading to the deterioration of prestressed concrete sleepers has retained the sleepers from being exploited to their full extent. In addition, excess utilization of cement in producing the same has paved the way for developing its counterpart, geopolymer concrete (GPC), involving primary industrial residues as their precursors. This study presents a comprehensive investigation into the development and performance of high-strength geopolymer concrete sleepers for railway applications. The research focuses on the complete replacement of ordinary Portland cement with Fly ash and Ground Granulated Blast Furnace Slag in the geopolymer concrete mix, for mainline prestressed railway sleepers following Indian Railway Standards (IRS). Notably, the study includes experimental validations of long steel fibers as secondary reinforcement to the primary prestressing strands, aiming to enhance the ductility of the member. Experimental validations were performed on full-scale (1:1) sleeper members under static loading conditions. The main aim of this article was to assess the load carrying capacity at cracking and ultimate limits, rail seat bending moment, ductility indices, failure mechanism, electrical impedance, bond strength, and the eco-efficiency for the proposed prestressed geopolymer concrete sleeper members (with and without steel fibres) with reference to the conventional prestressed cement concrete sleepers. The considered GPC mix was found to achieve higher load and moment carrying capacity by about 8.3% and 8.54% respectively compared to the conventional concrete mix. The addition of steel fibres in the GPC increased the load and moment capacity of sleepers by 23% and 24.21% respectively. Additionally, the steel fibre reinforced GPC showed improved displacement ductility demand over the plain geopolymer concrete averaging 25%, 28.5%, and 3% corresponding to ultimate, failure, and residual ductility index respectively. Though inclusion of steel fibers improves the performance of sleepers in terms of load and ductility, they were found incompatible with regard to the electrical impedance property when used in conjunction with the pre-stressing strands.

Impact of calcium content and pH value on MICP crack healing of geopolymer concrete

In recent years, microbial-induced carbonate precipitation (MICP) is becoming a popular method of soil stabilisation and concrete crack healing. In MICP, calcium is a necessary reactant, and pH value is a crucial factor for living bacteria. Both parameters (i.e., calcium and pH) are adjustable for geopolymer concrete mix design. Given the attractive potential for future applications of geopolymer concrete, understanding the impact of calcium content and pH value of MICP crack healing in geopolymer concrete mix design is of great importance. In this study, it was found that high calcium content in geopolymer concrete mix design is helpful to improve the healing effect. When CaO% in mix design increases from 7.5 % to 18.3 %, the healing degree increases. When Na2O% increases from 4.4 % to 11.6 %, the pH value of geopolymer concrete is improved by around 1, and it was also found that the impact of pH value depends on the way healing is implemented. In the case where bacteria were applied from outside of the healing surface cracks, the effect of pH value was almost negligible. However, when bacteria were used for internal healing, the lower pH value of the geopolymer mix design was beneficial for bacteria to provide a more suitable environment for bacterial activity and thus generate healing products. Therefore, the adjustment of calcium content and pH value in the geopolymer mix design can enhance the effectiveness of MICP crack healing for geopolymer concrete.

Strength and durability study on alccofine based geo-polymer concrete

Geopolymer concrete (GPC) emerging as the most innovative construction material, which not only reduces the requirement of Ordinary Portland cement (OPC) but also enhances the properties of the concrete as well, and decreases the ejection of harmful gases into the atmosphere like Carbon dioxide (CO2), Nitrogen, and Sulphur, Which is a prime concern for the environment. The need for concrete is raising uncharacteristically and so does for the OPC, to minimize the demand for OPC cementitious materials like Fly ash, Ground Granulated Blast Furnace Slag (GGBS), Silica Fume, Alccofine, Metakaolin, namely mineral admixtures used as partial or full replacements to the OPC. This present paper reports the properties of GPC made with Flyash, GGBS, and Alccofine for Mix M40- grade concrete the outcomes were contrasted with Nominal concrete which is made using 100 percent cement, Fly ash content of 50% was kept constant throughout the investigation whereas GGBS and Alccofine content varied with an interval of 5%. The concrete was tested for workability, strength, and durability aspects, an increment in the slump, and in the strength was noted, and great resistance was observed under the acid attack test for a GPC mixes, a combination of 50% Fly ash, 35% GGBS, and 15% Alccofine GPC mix was shown optimum results.

Effect of Addition of Cement in Binary Blended Geopolymer Concrete

The construction industry contributes significant greenhouse gases to the climate by consuming vast amounts of cement. Researchers are looking at alternative cement methods to decrease the adverse effects, one of which is Geopolymer Concrete (GPC). The GPC is made from industrial waste materials high in silica and activated with sodium hydroxides (NaOH) to form sodium silicate (Na2SiO3) because Geo polymer is a material that is just two decades old and is an area of extensive research. To study the effect of the addition of cement to GPC’s mechanical properties by replacing up to 50% of the ground granulated blast furnace slag (GGBFS) and fly ash with ten per cent increments. The outcomes are contrasted with the Geo Polymer Concrete control mix. For this study, an analysis of activators to fly ash at 0.35, NaOH to Na2SiO3 at 2.5, and the molarity of sodium hydroxide was set at 8M. At different ages, the compressive strength of cubes was calculated, as well as their split and flexural strengths following a 28-day curing period. The findings revealed that adding cement to the mix improves the mechanical properties. The best results are obtained at 40% cement, fly ash, and GGBFS at 60%.

Carbonation and permeation behaviour of geopolymer concrete containing copper slag and coal ashes

The current study primarily evaluates the carbonation and permeation resistance of coal bottom ash (CBA) and copper slag (CS) based geopolymer concrete (GPC). The strength parameters along with non-destructive tests were also performed for reference. CS and CBA were used as a 10%, 30% and 50% replacement of natural fine aggregates (NFA). Fly Ash (FA) was used as a binder and all seven mixes were subjected to oven curing at 65 °C for 24 h. The molarity of NaOH was kept constant (12 M) along with Sodium Silicate/Sodium Hydroxide ratio of 2. With inclusion of CS the carbonation depth, initial and capillary absorption has been decreased by 30%, 23% and 19% respectively with respect to control mix. The above-mentioned values have been increased by 28%, 27% and 58% in CBA based GPC. GPC mix containing 30% replacement of CS as sand has been considered to be appropriate for carbonation and permeation aspects.

Effects of slag and alkaline solution contents on bonding strength of geopolymer-concrete composites

Geopolymer has received widespread attention due to their excellent mechanical properties and more environmentally friendly characteristics. Studying the bonding performance between geopolymer and concrete is of great significance for the development of a building material for repairing damaged concrete. The paper studied the effects of slag and alkaline solution contents on bonding strength of geopolymer-concrete composites (GCC). Firstly, 15 groups of geopolymer concrete mix proportions with 5 groups slag contents and 3 groups alkaline solution contents were designed. GCC specimens were prepared by casting geopolymer concrete on cement concrete substrates. Secondly, the splitting tensile test was conducted on GCC specimens. The strain field during the testing process of GCC specimens was analyzed based on the digital image correlation (DIC) technique. Thirdly, the effects of slag and alkaline solution contents on the splitting tensile strength of GCC specimens were discussed. Finally, the optimal mix proportion of geopolymer concrete which has the highest bonding strength with cement concrete was proposed. The results show that the splitting tensile strength of GCC specimens increases first and then decreases as the slag content increases. The splitting tensile strength of GCC specimens decreases linearly as the alkaline solution content increases. In addition, the crack growth rate of GCC specimens increases with the increase of slag content during the splitting processing. The geopolymer concrete with 50.0 % slag content and 0.7 alkaline solution-binder ratio shows the highest bonding strength with cement concrete, which is recommended for the potential application in the pavement repair works.

The Effect of Superplasticizer (SP) on the Workability and Skid Resistance of Geopolymer Concrete (GPC) Containing High Calcium Precursor (HCP)

A superplasticizer (SP) is one of the admixtures that may be used to improve the workability of concrete. However, its effects on geopolymer concrete (GPC) have yet to be well known or published, especially regarding its skid resistance and workability performance. This research aims to study the impact of the superplasticizer on the skid resistance and workability of geopolymer concrete containing high calcium precursor (HCP) in different proportions of SP, which are 0, 0.5, 1.0, 1.5 and 2.0 % by the weight of the HCP. Seven mix designs were produced: 1 conventional concrete mix, 5 geopolymers concrete mix, and 1 bituminous cold-mix asphalt mix. Slump flow and skid resistance tests were performed in this study. A skid resistance test is achieved using a British Pendulum Tester (BPT) on a 220 mm x 220 mm x 50 mm rectangle. This study found that the effect of SP on skid resistance is insignificant. However, the skid resistance of all GPC mix designs is higher than CC and asphalt mix. The workable flow of geopolymer concrete containing HCP and 0 - 2 % SP was 118-123 mm. However, less than 2 % of SP is given an insignificant difference. The optimum mix design of GPC is mix design GPC with an added 2 % SP (M6) that gives a high workability compared to other GPC mix designs and good skid resistance of 95 BPN. This study also found that workability correlates with skid resistance. The higher the spreading width value, the smaller the skid resistance value. In other words, the higher the flowability value, the less rough the sample surface. Hypothetically, the higher the percentage of SP, the higher the workability and the lower the skid resistance.

Evaluating Effect of Palm Kernel Shell Ash Additives on Compresive Strength Properties of Geopolymer Concrete of Clay from Ire Ekiti and Ikere Ekiti

With abundance and viability of Clay soil at Ire Ekiti and Ikere Ekiti which can be use as geopolymer source material and abundance of Palm kernel shell ash (PKSA) in south western Nigeria, this study is to evaluate effect of PKSA- an agricultural waste, as additive on compressive strength of Ire and Ikere clay geopolymer concrete. Palm kernel shell was ashed at 650°C for 2 hours at the furnance of glass technology department, federal polytechnic, Ado- ekiti. Ire and Ikere Clay was similarly procured, air dried and calcined in a furnace at 750°C for 2 hours. The Pulverized calcined clay as source material for the geopolymer with 12M of NaOH and Na2SiO3, with NaOH to Na2SiO3 at ratio 2:5. River sand and 12 mm aggregate size of granite were adopted as filler in the geopolymer concrete mix at ratio 1:2:3. PKSA in mass percentages of the Ire and Ikere Clay in order of 0, 7.5 and 15% were added to the geopolymer concrete mixes for different specimen and maturities of 7, 14 and 28 days. Compressive strength of Ire Clay geopolymer concrete with PKSA as additives at room temperature has its highest compressive strength at 7.67 N/mm2 at 28 days with 15% additive while that of Ikere Clay Geopolymer has 10 N/mm² at 28 days maturity with 15% additive.

Review of geopolymer concrete in high grade infrastructure construction

The construction industry must ensure a new occupant experience that is connected, safe, and comfortable. Due to its versatility, concrete is the most frequently used building material worldwide. Cement is an essential ingredient of concrete, but it is not considered environmentally friendly. The production of Portland cement consumes a considerable amount of energy and emits a significant amount of carbon dioxide. By creating and utilizing alternative materials, like geopolymers, construction may become much more sustainable. Cement production has a significant environmental impact, which must be reduced by developing new binder types. With the use of various industrial byproducts, the workability, impacts of temperature change, usage of admixtures, use of fibers, and effects of the water-binder ratio of geopolymer concrete are all investigated. It indicates that the regulated geopolymer concrete mix's compressive strength is inferior to that of geopolymer concrete with additional hooked-end steel fibers. As a recent innovation in concrete, Geopolymer is a substance in which fly ash, which is activated by an alkaline solution to act as a binder, completely replaces cement. Geopolymer concrete was analyzed with different ratios of activators for strength analysis. To select the correct ingredients for geopolymer concrete to achieve the desired strength at the desired workability, the grading of geopolymer concrete following the Indian Standard Code has been the subject of experimental effort. Assessing the amount and fineness of fly ash, the amount of water, or the amount of alkaline liquid is a step in the mix design process, along with the W/C ratio, fine aggregate quality, fine aggregate proportion to total aggregate, and superplasticizer content. Premixed geopolymer concrete's compressive strength, shear strength, flexural strength, and bonding strength will be evaluated after the materials' internal reactivity has been verified.

The Effect of Polypropylene Fiber and Steel Fiber on Geopolymer Concrete

One of the environmentally friendly concrete as an alternative to cement concrete in the future is geopolymer concrete which used a cement substitute in the form of fly ash. To prevent premature cracking of the concrete, this study added fiber types such as polypropylene fiber, and steel fiber (dramix), this experiment with 3 variables namely the addition of polypropylene fiber by 0%, 0.40%, 0.80%, 1.2%, steel fiber of 0.25%, 0.50%, 0.75%, 1.00%, as well as a combination of polypropylene fiber and steel fiber (0.4%P;0.50%D), (0.8%P;0.75%D), (1.2%P;1.00%D) of the weight of the concrete. In this study, using a beam specimen measuring 10x10x50 cm, for each percentage of fiber usage there are 2 beam trials. Geopolymer concrete in this study uses a ratio of NaOH and Na2SiO3 is 2:1 and a constant concentration of 10 Molar, to test the Flexural Strength Test of Concrete at the age of 28 days of concrete. The results of the highest average flexural strength of geopolymer concrete without fiber σl = 78.77 kg/cm2, using polypropylene 0.80% σl =50.50 kg/cm2, and 0.25% steel fiber σl =68.87 kg/cm2, the combination of both fibers (P0.4%; D0.25%) σl =65.34 kg/cm2. These results do not produce good workability, thus affecting the decrease in flexural strength. By increasing the ratio A = 0.35 to 0.45, the geopolymer concrete mix produces better workability with the highest average flexural strength of geopolymer concrete with polypropylene fiber 0.8% σl = 80.107 kg/cm2.

Prediction of compressive strength of geopolymer concrete using a hybrid ensemble of grey wolf optimized machine learning estimators

Geopolymer concrete (GPC) has the potential to replace conventional concrete. But, the mixed proportion of GPC poses several difficulties due to various contributing factors. The design of a reliable prediction model becomes challenging because of the non-linear relationship between the proportion of GPC mix and compressive strength (CS). This study implements a hybrid ensemble machine learning model (HEML) from grey wolf optimized conventional machine learning (CML) models to predict the CS of GPC. An experimental database of 1123 records was compiled from different published research work. The database was used to train and test three optimized CML models namely random forest regressor (RFR), Neural network (NN), and Multivariate regression spline (MARS). Utilizing a meta-learner XGBoost algorithm, the CML models' predicted outputs were trained to develop HEML. Statistical parameters notably R2, Adjusted R2, RMSE, MAE, MAPE, VAF, index, and the Shapiro-Wilk statistical test were used to compare the HEML and CML models' predicted outputs. The HEML model showed better performance in both the training and testing phase than the CML models. Two sensitivity analysis methods were adopted to analyze the impact of various parameters on the compressive strength of geopolymer concrete based on the model with the highest prediction accuracy.

Mechanical and bond behaviour of high volume Ultrafine-slag blended fly ash based alkali activated concrete

The development of Geopolymer concrete (GPC) mixes by employing large volume of ultrafine ground granulated blast furnace slag (UBFS) blended with Fly ash (FA) and activated by sodium hydroxide (SH) has been presented in this study. Several GPC mixes has been prepared to investigate the effect of varying alkali content, fine aggregate to total aggregate ratio (s/a) and molar concentration (M) of alkali activator on the fresh and hardened characteristics, including the bond strength with Portland cement concrete (PCC). The properties of the GPC mixes are assessed by workability test, compressive strength test, split tensile strength test and slant shear test, including the microstructure through FESEM (Field Emission Scan Electron Microscopy) and X-ray diffraction (XRD). The test result shows that s/a ratio is a crucial factor in controlling segregation and bleeding in GPC. However, an ideal GPC mix with s/a ratio 0.41 provides a better packing resulting in improved mechanical properties. Application of high volume UBFS in the GPC exhibits better reaction products as shown by the microstructure at a relatively lower alkali concentration which ultimately leads to higher strength. Superior bond strength is achieved between the GPC and old PCC substrate; however, the molarity of SH significantly affects the adhesion property of GPC.