Geopolymer Concrete Specimens Research Articles

Evaluating the Influence of Palm Kernel Shell Ash on Ire Clay Geopolymer Concrete Cured at Ambient Temperature

There is an abundance of clay deposit in Ire Ekiti which can serve as geopolymer source material and Palm kernel shell exists as a massive agro waste in South Western Nigeria. This study evaluates the effect of palm kernel shell ash (PKSA) as an additive on the compressive strength of Ire clay geopolymer concrete. The objective of the study is to determine the selected properties of the obtained concrete at room temperature. Palm kernel shell was burned at 650oC for 2 hours in a furnace. Natural clay collected from Ire Ekiti was manually pulverized, air dried and calcined in a furnace at 750o for 2 hours. The geopolymer concrete was prepared at a mixing ratio of 1:2:3. The material constituents were calcined clay (source material), 12M of NaOH and Na2SiO3 (ratio of NaOH to Na2SiO3 was 2:5), river sand and 12.5mm granite were the fine and coarse aggregates respectively while PKSA of 0%,7.5% and 15% of the calcined Ire Clay content were used as additive in preparing the geopolymer concrete. geopolymer concrete specimens were cured at ambient temperature till testing at different maturity ages of 7, 14 and 28 days. It was generally observed that increasing the percentage of PKSA as additive strongly improved the compressive strength gain with maturity of the Ire clay geopolymer concrete. At 28 days maturity, 7.5% PKSA addition improved the compressive strength by 166% while 15% PKSA addition improved the strength by 181% increase. The highest compressive strength was 7.67N/mm2 at 15% PKSA addition on 28 day. Conclusively, Ire clay and PKSA are viable source material and additive respectively for geopolymer concrete production. The Ire clay geopolymer concrete can be practically applied like conventional concrete in structural work especially in a rural community like Ire Ekiti where cement needs to be transported over kilometers. Also, the concrete performing well at ambient temperature makes it cost effective compare to most geopolymers that require heating at high temperature. It is recommended that further study on the durability should be done.

Axial compressive behaviour of GPC filled FRP Tubes: Experimental and analytical investigations

The production of Ordinary Portland Cement (OPC) releases carbon dioxide (CO2), which is one of the main contributors in the rising level of Greenhouse Gases (GHG) into the atmosphere and adversely effecting the environment and subsequently causing the climate change. In this study, the fly ash (FA) an alternative of OPC is used to produce environmental friendly cementless geopolymer concrete (GPC). This study investigates the axial compressive behavior of GPC filled fiber reinforced polymer (FRP) tubes. Two types of FRP tubes, i.e., carbon FRP (CFRP) tubes and glass FRP (GFRP) tubes were prepared by the wet lay-up procedure using CFRP and GFRP sheets, respectively. A total of forty-five GPC specimens of 150 mm diameter and 300 mm height were prepared with five different molarity of NaOH (8–16 M) with Na2SiO3 to NaOH ratio of 1.5. The unconfined GPC (Control), GPC filled CFRP tube (GCT) and GPC filled GFRP tube (GGT) specimens exhibited a significant increase in the peak axial stress (fc) with the increase in the molarity of NaOH. The scanning electron microscopic investigation also exhibited a reduced number of unreacted fly ash particles in the GPC with increasing the molarity of NaOH. The fc and corresponding axial strains (∊c) of GCT and GGT specimens were significantly higher than those of unconfined GPC specimens. The GCT specimens exhibited higher fc and corresponding ∊c than the GGT specimens. The analytical axial stress–strain (fc-∊c) curves of GCT and GGT specimens developed using available fc-∊c models of FRP confined ordinary Portland cement (OPC) concrete matched well with the experimental fc-∊c curves of GCT and GGT specimens.

Effect of fibre characteristics on physical, mechanical and microstructural properties of geopolymer concrete: A comparative experimental investigation

AbstractThe main aim of this work is to comparatively reveal the effect of fibre type, length and content on compressive strength and microstructure of structural geopolymer concrete (GPC) produced under constant mixture and curing parameters in order to address the significant gap in present literature. Firstly, GPCs with different NaOH concentrations (i.e., 6, 9, 12 and 15 M) and activator solution/binder (a/b) ratios (i.e., 0.45 and 0.55) were produced in ambient curing condition, and optimum production parameters were determined based on the preliminary evaluations. Then, glass and polypropylene fibres in 6‐mm length (GS6 and PP6) and polyamide and polypropylene fibres in 12‐mm length (PY12 and PP12) were included in GPCs at ratio of 0.4%, 0.8% and 1.2% (by volume). Compressive strength, apparent porosity, bulk density, ultrasonic pulse velocity (UPV), X‐ray diffraction (XRD) and scanning electron microscope (SEM) analysis of GPC samples were carried out comparatively. The inclusion of GS6 fibre enhanced the compressive strength thanks to fibre surface being covered by geopolymer gel and the strong adhesion between GS fibre and geopolymer matrix. SEM images of fibre reinforced GPC (FRGPC) also confirmed the experimental findings, which were attributed to improvement in compressive strength. Regardless of the fibre type, the maximum compressive value strength was obtained from GPC specimens with 0.4% fibre and then decreased. Higher fibre inclusions led to poor compaction, workability issues and inhomogeneous fibre dispersions. A very good relation (R2 = 0.98) was acquired between UPV and compressive strength values of GPC/FRGPC samples.

The influence of low alkaline activator on the compressive strength and workability of geopolymer concrete

This paper presents the results of research on geopolymer concrete using a reasonably low alkaline activator. The key objective concerning this research is to investigate whether a low alkaline activator is still qualified to produce a concrete compressive strength that fulfills the structural requirements. The experimental program is carried out by making geopolymer concrete specimens, where the variables reviewed represented the amount of alkaline activator (4% and 5%), the ratio of alkaline activator to fly ash (AAS/FA) was 0.35, 0.4, 0.5, 0.6. The treatment temperatures of the specimens were room temperature (33°C) and 60°C. The experimental results of the compressive strength test have shown that the compressive strength of low alkaline geopolymer activator concrete still meets the requirements as a structural material (i.e. Indonesian Concrete Code). The weight of the resulting specimen is included in the category of normal weight concrete. The workability of geopolymer concrete with low alkaline activator tends to be better if the ratio AAS/FA also increases, but the compressive strength of concrete tends to decrease.

Effects of Cementitious Material Content and Sand Ratio on Mechanical Properties of the Dry-Mixing Geopolymer Concrete

The paper investigates the 7-day, 28-day and 56-day compressive & splitting tensile strength of thirty geopolymer concrete specimens using the dry mixing method. The cementitious material content, sand ratio, along with the water binder ratio were chosen as the variables. Influences of the parameters on the mechanical behavior of the dry mixing geopolymer concrete are discussed in the paper.

One-Year study of restrained shrinkage and creep behaviours of geopolymer concrete

The viability of geopolymer concrete (GPC) for industrial applications has been increasing in recent years by utilising solid alkali activators and curing at ambient temperature. With higher viability and desirability for engineering applications, their dimensional stability and serviceability properties remained a focal point for investigation. The one-year dimensional stability of GPC was studied using standard shrinkage and creep tests. Furthermore, a novel photogrammetry technique was introduced and utilised to measure the shrinkage of concrete slabs in restrained conditions. The 56-day drying shrinkage of GPC specimens was between 280 and 600 microstrain, which is suitable for most structural engineering applications. GPC experienced a slightly higher drying shrinkage in free condition than conventional concrete when the fly ash/slag mix ratio was 60/40. However, GPC displayed 38–57% lower shrinkage in restrained conditions than the conventional counterpart. GPC specimens also experienced lower creep strain and coefficient when compared to normal concrete. The GPC shrinkage and creep performance revealed that slag content played a crucial role, as the free shrinkage and creep strains in slag-dominant GPC were the highest.

Studies on the mechanical and durability performance of textile reinforced geopolymer concrete beams

The steel reinforcements used in structural elements are prone to corrosion due to adverse environmental effects. Hence, in recent years, the development of sustainable materials to replace steel reinforcement in concrete has been under research. In this paper, the mechanical and durability characteristics of Geopolymer Concrete (GC) and Epoxy-coated Carbon (EC) yarn against chemical attack were investigated. Tension tests were conducted on EC yarns immersed in acid, sulfate, marine water, and alkaline solution over an exposure period of 1 year. The test results reveal that better durability was achieved for GC specimens compared to cement concrete (CC) specimens in terms of water absorption, acid resistance, sulfate resistance, marine water attack, and chloride diffusion. Compressive strength and flexural strength obtained were 2.6–7.7 times and 1.65–2.36 times higher in GC compared to CC after immersion in various chemical solutions for 6 months. The chemical resistance of EC yarns over an exposure period of 1 year was measured with respect to loss in tensile strength and the reduction in strength was obtained as 29.6% for EC yarns immersed in acid solution, 14.71% in sulfate solution, 7.06% in alkali, and 3.82% in marine water. The study also investigated the flexural behavior of Textile Reinforced Geopolymer Concrete (TRGC) beams (100 × 100 × 500 mm) subjected to monotonic loading. The effectiveness of textile yarn spacing and the number of carbon textile layers to improve the load-bearing behavior of GC beams were evaluated. The reinforcing benefits of TRGC can be confirmed from the load-deflection graph in terms of ultimate load-carrying capacity, post-peak behavior, and failure mode. An energy absorption capacity of 80.06% was found for TRGC-4 L beams compared to TRGC-1 L beam specimens (43.76%), i.e., TRGC specimens with 4 layers showed improved strength and ductility compared to one layer of carbon textile. The failure surface of the TRGC sample was examined using Scanning Electron Microscope (SEM), and fiber-matrix interaction was identified. Hence, despite the high cost of carbon yarn, TRGC can be used for special applications where corrosion protection and durability are controlling parameters.

Effects of various additives on the crumb rubber integrated geopolymer concrete

The use of scrap tyres in construction materials has been promoted to curb the environmental exploitation caused by the open disposal of non-biodegradable waste rubber. Tyre grinds as aggregates in geopolymer concrete (GPC) would increase its sustainability value by reducing the consumption of natural aggregates. Although there is limited literature addressing the damage to GPC characteristics caused by rubber aggregates, this investigation was designed to determine the extent of possible side effects of using crumb rubber (CR) in GPC. Additionally, this investigation aims to address any resulting reduction in strength and durability using additives such as cement and fibres. Geopolymer specimens with CR replacement of fine aggregates by volume (0, 5, 10 and 15%) showed a compressive strength reduction of up to 17% when tested according to ASTM standards. Substituting the total binder by weight with Ordinary Portland cement (OPC) (0%, 5%, 10%, 15%, and 20%) improved the microstructural integrity of the rubberised geopolymer mix with the highest percentage of OPC. Despite producing new and additional binding products (CSH and CASH gels), the GPC surface readily disintegrated under acid exposure. Optimum glass fibres (GF) reinforcement (0.30%) effectively disrupted the GPC pore network, consequently reducing the acid permeability of the matrix. Further addition of steel fibres (SF) enhanced the GPC specimen's compressive and flexural strength. To analyse the cumulative effect of these additives on GPC microstructure, supporting tests such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were carried out. Although these additives enhanced the overall performance of rubberised geopolymer, it might somewhat reduce its green aspect.

Experimental modal analysis of fly ash-based geopolymer concrete specimens via modal circles, mode indication functions, and mode shape animations

The polymerization process of geopolymer concrete is entirely different from the hydration process of ordinary Portland cement concrete. Therefore, it is necessary to re-examine this new material's engineering properties from the ground up. To date, researchers have investigated many engineering properties, but in the whole literature, the available information about the modal characteristics is minimal. Additionally, since the evaluations in the literature are made only on the A ratio (sodium silicate to sodium hydroxide ratio), no significant relationship has been reported between damping and activators. So, this study is conducted to draw attention to this gap in the literature and examine the effect of fundamental geopolymer concrete component ratios on modal characteristics. For these purposes, large-scale heat-cured low-calcium fly ash-based geopolymer concrete mix variations are produced and investigated by performing experimental modal analysis via the advanced modal circle method and mode indication functions. It is found that individually analyzing the total amount of water from the activators and the pure chemical dosages provides more meaningful results than the traditional A ratio. According to the analysis from this perspective, increasing the dosage of pure sodium silicate in the mixture generally increases the damping; on the other hand, it decreases the resonance frequency and dynamic elasticity modulus. Obtained findings of this study reveal some of the methods and benefits of appropriately designing this sustainable material against dynamic loads.

Flexural performance of steel-reinforced geopolymer concrete one-way slabs: Experimental and numerical investigations

This paper investigated the out-of-plane flexural performances of ambient-cured steel-reinforced slag and fly ash-based geopolymer concrete one-way slabs, in which the activator was the blend of NaOH and sodium silicate solutions (SiO2/Na2O = 3.1–3.3). Twelve specimens were prepared and tested, which included six OPC concrete specimens. The test parameters were concrete type (i.e., geopolymer and ordinary Portland cement (OPC) concrete), concrete compressive strength (i.e., 30 MPa, 40 MPa, and 50 MPa) and longitudinal tensile reinforcement ratio (i.e., 0.82 % and 1.20 %). The failure modes, crack patterns, load–deflection relationships and load–strain relationships of all specimens were carefully studied and reported. Further, a two dimensional (2D) finite element (FE) analysis was conducted to validate the test results. The results of the study indicated that: (1) the geopolymer concrete specimens presented lesser crack width and crack spacing owing to the improved bond between rebar and geopolymer concrete; (2) the cracking load and initial stiffness of geopolymer concrete specimens were slightly lower than that of OPC concrete counterparts; (3) the current Codes of Practice GB50010-2010 and ACI 318-19 provided reasonable predictions of the cracking load and flexural load capacity of the steel-reinforced geopolymer concrete specimens; (4) the developed FE model provided a good prediction of the flexural performance of the tested slabs, and could be used for further parametric investigation.

Investigation of abrasion resistance of geopolymer concrete cured in ambient temperature for pavement applications

The viability of eco-friendly geopolymer concrete (GPC) for engineering applications such as pavements requires investigating the abrasion resistance and understanding the improving mechanisms. The produced one-part GPC can be used in various engineering applications showing a 28-day compressive strength between 25–42 MPa and flexural strength above 4.5 MPa. GPC slabs, compared to ordinary Portland cement-based concrete (OPCC), generally experienced higher abrasion. While the abrasion of the OPCC specimen in 28 days was 2.72 mm, the GPC specimens experienced an abrasion between 3.60 and 4.11 mm. The dominance of slag and increasing water content increased the abrasion. It is concluded that the strong connection between microstructural behaviour and macrostructural properties is the key element in GPC performance. Hence, it is recommended that careful attention be paid to the refinement of the microstructure in order to find a GPC that is viable and suitable for pavement and road applications.

Performance of Reinforced Foam and Geopolymer Concretes against Prolonged Exposures to Chloride in a Normal Environment.

The utilization of sustainable cement replacement materials in concrete can control the emission of carbon dioxide and greenhouse gases in the construction industry, thus contributing significantly to the environment, society, and the global economy. Various types of sustainable concrete including geopolymer concrete are tested for their efficacy for construction in laboratories. However, the performance and longevity of sustainable concrete for civil engineering applications in corrosive environments are still debatable. This paper aims to investigate the performance of the reinforced geopolymer (GPC) and foam concretes (FC) against corrosive chloride exposure. Two long term key parameters, i.e., corrosion rate and mechanical performance of reinforcing steel in geopolymer and foam concrete were assessed to evaluate their performance against chloride attack. For experiments, reinforced GPC and FC specimens, each admixed with 3 and 5% chlorides, were kept at varying temperatures and humidity levels in the environmental chambers. The corrosion rates of the reinforced geopolymer and foam concrete specimens were also compared with control specimens after 803 days and the tensile strength of the corroded reinforcing steel was also determined. Moreover, the long term efficacy of repaired patches (810 days), in a chloride-rich surrounding environment utilizing FC and GPC, was investigated. The results suggested greater performance of FC compared to GPC under standard environmental conditions. However, the simulated patch repair with GPC showed better resistance against chloride attack compared to FC. The research also undertook the fractographical examination of the surfaces of the reinforcement exposed to 5% admixed chloride and develops models for the corrosion rates of foam concrete as a function of the corrosion rates of geopolymer concrete and chloride content. A correlation model for the corrosion rates of FC and GPC was also developed. The findings of the current research and the model developed are novel and contribute to the knowledge of long term degradation science of geopolymers and form concrete materials. Furthermore, the findings and methodology of the current research have practical significance in the construction and repair industry for determining the remaining service life for any reinforced and steel infrastructure.

Comparative Analysis of Geopolymer Concrete with Different Proportions of Fly ash and GGBS with Conventional Concrete Considering the Strength and Durability Parameters

Abstract: The global demand of concrete for the construction of infrastructures is continuously increasing. The production of cement is highly intensive and it emits a lot of CO2 into the air which leads to the global warming. One of the effort to produce the environment friendly concrete is geopolymer concrete which emits less CO2. In the present study the feasibility of industrial by-products i.e.; Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) powder as eco-friendly and sustainable is studied. So the main aim of this study is to analyse the performance of fly ash and GGBS based geopolymer concrete with conventional concrete which are compared with respect to strength and durability parameters for (7days and 28 days) curing period. In this study strength parameters includes compressive strength, split tensile strength and flexural strength and durability parameters includes acid attack test and rapid chloride permeability test. The two different proportions of (70% fly ash+ 30% ggbs) and (60% fly ash+ 40% ggbs) are used in geopolymer concrete. The Alkaline solutions used are sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The study includes casting of geopolymer concrete and conventional concrete specimens and tested for (7 and 28 days) ages for both strength and durability. The results show that Geopolymer concrete gives good strength and durability compared to conventional concrete. Thus, the Geopolymer concrete can be considered to be an environmentally pollution free construction material.

High-strength geopolymer concrete based on coal washing waste

In recent years, geopolymers have gained significant attention as an environmental-friendly alternative to Ordinary Portland Cement (OPC). Geo-Polymer Concrete (GPC) can be made using different aluminosilicate sources but using waste aluminosilicate sources not only helps to reduce environmental pollution, also leads to efficient waste management. Coal Washing Waste (CWW) refers to the waste that remains after coal washing process in the purification plants. CWW (if properly activated) can be used as a high potential aluminosilicate source to produce GPC or a supplementary cementitious material in the production of Blended Cement (BC). Hence, this study aims to investigate the use of CWW as a waste aluminosilicate source for manufacturing GPC. In this regard, CWW subjected to various methods of thermal activation and the obtained ash was used to produce GPC specimens. Thereafter, the mechanical and physical properties of CWW based-GPC were studied and also compared with conventional concrete. Furthermore, CWW ash was used as an OPC partial replacement (15 %) for BC production. The obtained results indicated that thermal activation conditions of CWW have a significant effect on the properties of the obtained CWW ash. Rapid and abrupt cooling of ash after heat treatment resulted in higher pozzolanic reactivity and thus higher compressive strength. Moreover, CWW ash-based GPC offers higher mechanical strengths, as well as excellent resistance to acidic conditions and low water absorption capacity. Furthermore, CWW ash-based GPC provides proper resistance to evaluated temperatures so that it is almost stable up to 800 °C.

Investigation on engineering properties and micro-structure characteristics of low strength and high strength geopolymer composites subjected to standard temperature exposure

Fire accidents are common and one among the serious hazards faced by civil infrastructures; therefore, appropriate measures have to be taken while designing the buildings and structures to ensure the safety of the residents. Reducing the damage caused by fire and the collapse of structural elements are the primary significance in designing concrete structures. An experimental study was conducted to examine the mechanical properties of temperature exposed concrete specimens following ISO 834 standard fire curve. Present investigation examines the performance of Geopolymer concrete (GPC) after exposed to temperature exposure. Two types of concrete namely, low and high strength GPC were cured under two curing regimes viz, room temperature curing and oven curing was adopted in this study. The GPC specimens were heated to 821 °C, 925 °C, 986 °C and 1029 °C, following the rate of heating was in accordance with ISO 834. Influence of elevated temperature on GPC specimens were examined by visual inspection, weight loss, strength loss and micro-level studies including Scanning Electron Microscope (SEM). Results from the study reveals that, the strength of high strength concrete was more prone to temperature exposure. Room temperature cured GPC specimens possessed higher residual strength than oven cured specimens for all the heating durations (marginal variation less than 5%). Crushing Index (CI) of 8.1% was regarded as optimal value for coarse aggregates (CA) to sustain its strength at a temperature of 821 °C. The phase change and dehydration of geopolymeric gel were observed in SEM analysis, and strength loss of CA are considered as the influencing parameters for degradation of concrete at higher temperature exposure. High strength concrete is more prone to strength loss than low strength concretes.

Synthesis of Geopolymer Concrete Using Flyash

Geopolymer concrete (GPC) reduces the environmental impacts of conventional Portland cement concrete, therefore, this research aims to investigate the compressive characteristics of GPC by utilizing the readily available industrial waste i.e., coal based Flyash in the Khyber Pakhtunkhwa province of Pakistan. For the preparation of GPC, Na2SiO3 was used as an activator. After the preparation of GPC specimens, their compressive characteristics were investigated at different ages of specimens, Flyash content, curing time, and curing conditions. Moreover, the relationship between compressive strength and modulus of elasticity of GPC was also evaluated. From the testing of GPC specimens in a compression testing machine (CTM), their compressive strength was found to be similar to that of conventional Portland cement concrete i.e., in the range of 20-40 MPa tested at the age of 7 and 28 days respectively. Furthermore, elevated temperature curing was found to increase the compressive strength of GPC significantly as compared to that of ambient curing. From the cost analysis, Flyash-based GPC was found to be cost effective as compared to conventional Portland cement concrete

Effect of binder dosage and the use of waste rubber fiber on the mechanical and durability performance of geopolymer concrete

This paper was designed to find solutions to the fact that the availability of natural aggregates in accordance with the standards used in concrete is gradually decreasing, the environmental problems caused by cement threaten our future, and the recycling of used tire waste is very difficult. The effects of three different binder dosages (300, 400 and 500 kg/m3) on the mechanical and durability properties of geopolymer concrete (GPC) samples were investigated in binder contents consisting of 98% granulated blast furnace slag (GBFS) and 2% nano silica. As for the aggregate composition, natural sand was used as the fine aggregate, while the waste rubber fibers (WRF) were substituted in different proportions (0%, 5%, 10% and 15%) of the coarse aggregate by volume. Following the solid part was obtained as described, the alkaline activation of GPC specimens was provided using a 12 M NaOH solution. At the end of 28-day curing period, compressive strength, flexural strength, splitting tensile strength, impact resistance, capillary permeability and elevated temperature performance properties were investigated in detail and the results obtained from the mentioned tests were also confirmed by microstructural analysis. Experimental findings revealed that the increase in binder dosage resulted in significant increases in all of the mechanical properties, and it was speculated that this was due to the formation of a denser and more compact microstructure compared to their counterparts produced using lower binder dosage. Besides the negative effects of WRF usage on compressive strength and resistance of elevated temperature, the other performance criteria such as flexural strength, impact resistance and splitting tensile strength values of GPC samples significantly improved with the usage of WRF. As a result, experimental findings demonstrated that the usage of waste rubber fibers in the production of GPC was advantageous in terms of some mechanical and durability properties.

Experimental and Artificial Neural Network-Based Study on the Sorptivity Characteristics of Geopolymer Concrete with Recycled Cementitious Materials and Basalt Fibres

The environmental concerns regarding the production of the most widely consumed cement construction material have led to the need for developing sustainable alternatives. Using recycled industry waste products such as fly ash and slag via geopolymerisation has led to the development of geopolymer cement—an efficient replacement for ordinary Portland cement (OPC). Adopting geopolymer cement and concrete as a construction material reduces greenhouse gas and promotes the recycling of waste products. This study explores the suitability of a unique geopolymer concrete mix made of recycled cementitious materials including industry waste products such as fly ash, micro fly ash and slag for use in aggressive environments. Sorptivity tests are conducted to assess the durability of concrete and indicate the cementitious material’s ability to transmit water through the capillary forces. This study thus reports on the sorptivity characteristics of a newly developed self-compacting geopolymer concrete and two other fibre geopolymer concrete mixes containing 1% (by weight) of 12 mm- or 30 mm-long basalt fibres. The addition of basalt fibres indicated less water absorption and moisture ingress than the mix without fibres. The study used 18 specimens from three geopolymer concrete mixes, and the results showed that adding fibres improved the durability performance in terms of resistance to moisture ingress. Finally, an artificial neural network model is developed to predict the absorption rates of geopolymer concrete specimens using MATLAB. The prediction models reported excellent agreement between experimental and simulated datasets.

Flexural Behavior of Low Calcium Fly Ash Based Geopolymer Reinforced Concrete Beam

Pioneering studies have been conducted on alternative cementitious material in the manufacturing of conventional concrete to reduce carbon emission and improve the overall efficacy. However, there are limited studies on eco-friendly materials with low calcium fly ash. This study aims to examine the strength fly ash geopolymer concrete and reduce carbon emission. In this investigation, flexural test is done for conventional and geopolymer concrete (GPC) beam samples after the fulfillment of rest period and 24 h steam curing at 60 °C. The experimental results prove that the initial characteristics of both specimens are almost similar. When GPC specimens reached the service, yield, and failure stages, the load carrying capacity, deflection increased up to 21.5 and 8.75%, respectively and better load bearing capacity, moment resistance, and crack propagation were observed more than in conventional cement. Fresh property test results indicated the achievement of standard workability without the addition of any admixture. Our study show that low calcium based geopolymer can be used as an efficient material for the alternate of cement in cement-based industries with eco-friendly nature.

Feasibility study of compost as a partial substitute for fine aggregate in concrete

Abstract In this study, vermicompost is replaced for fine aggregate in geopolymer concrete (GPC). Initially mix design is made for GPC and mix proportion is proposed. The vermicompost is replaced at 5%, 10%, 15% and 20% with M sand in GPC. Result indicates the 5% replacement with vermicompost based geopolymer concrete (GPVC) has the compressive strength of 32 N mm−2 (M30 grade) whereas the compressive strength of control specimen made with GPC is 37 N mm−2. Other replacement shows 21 N mm−2, 14 N mm−2 and 11 N mm−2 respectively. The 5% replaced concrete cubes and control specimen are tested at an elevated temperature of 200°C, 400°C, 600°C and 800°C and compared with the control specimen. There is no significant difference observed in weight lost at control (GPC) and GPVC specimen. An elevated temperature, the weight loss is almost 4% at 200°C because of expulsion of water from the concrete. Afterwards only 2% weight loss is observed in remaining elevated temperature. The compressive strength loss is observed at an elevated temperature in GPC and GPVC specimen because of thermal incompatibility between aggregate and the binder. EDX results show M sand and compost contains Si, Al, C, Fe, Ca, Mg, Na and K and it is similar in the elemental composition and SEM image confirms vermicompost contains fine particles.