Reinforced Geopolymer Concrete Research Articles

Mechanical properties of basalt macro fibre reinforced geopolymer concrete

Growing public environmental awareness leads to an increased focus on utilizing green and sustainable materials in infrastructure construction. Geopolymer concrete (GPC) and basalt macro fibres (BMFs) are promising construction materials due to their eco-friendly merits and excellent mechanical properties. In this study, a new type of BMFs reinforced GPC (BMF-GPC) was developed, and the compressive and flexural properties of BMF-GPC were investigated. The effects of BMF content and length on the mechanical properties of GPC were studied. It was found that with the addition of 2 % BMFs, the compressive and flexural toughness (energy absorption capacities) of GPC were greatly enhanced by up to 126 % and 965 %, respectively. Increasing the content and length of BMFs resulted in favourable outcomes for strain softening of GPC under compression and post-cracking behaviour of GPC under flexural loads, whilst having limited effects on the modulus of elasticity and flexural strength. Additionally, an analytical model was proposed to predict the compressive stress-strain behaviour of BMF-GPC, which could be used for the design of BMF-GPC structures.

Experimental study on the flexural fatigue performance of slag/fly ash geopolymer concrete reinforced with modified basalt and PVA hybrid fibers

Geopolymer, owing to its inherent low-carbon emission advantages, emerges as a potential substitute to diminish reliance on high-carbon-emitting Portland cement. Nonetheless, similar to ordinary Portland cement concrete, geopolymer concrete tends to exhibit brittle fracture under cyclic bending loads. To improve its flexural fatigue performance, this paper incorporated the modified basalt (MB) fiber and PVA fiber in hybrid form into the geopolymer concrete. The flexural fatigue behavior of hybrid fibers reinforced geopolymer concrete was investigated, with a focus on the influence of varying hybrid fibers volume fractions. Digital Image Correlation technology was utilized to accurately track the evolution of crack length and the local strain field during the fatigue failure process. The results revealed that the incorporation of both MB and PVA fibers effectively delayed the initiation and propagation of cracks, leading to a more complex path of fatigue cracks. The PVA fiber demonstrated significant efficacy in inhibiting microcracks, while the MB fiber played a crucial role in controlling the expansion of macroscopic cracks. When the proportion of MB fiber was predominant in the hybrid mix, the crack development pattern mirrored that of samples containing MB fiber alone, exhibiting a greater extent of crack length. At a volume fraction of 0.9% for MB fiber and 0.2% for PVA fiber, a significant improvement in the fatigue life of the concrete was observed, resulting in a remarkable 136.23% increase compared to the control. This study has developed geopolymer concrete featuring enhanced crack resistance and superior flexural fatigue endurance under cyclic loading, promoting the application of environmentally friendly building materials in practical engineering.

Flexural performance and damage of reinforced fly ash and slag-based geopolymer concrete after coupling effect of freeze-thaw cycles and sustained loading

To better represent field conditions, the bending performance of reinforced geopolymer concrete (GPC) beams after the coupling effect of freeze-thaw cycling and sustained flexural load was investigated. Two types of GPC (G10 and G50) with different content of fly ash and slag were included and compared with ordinary Portland cement concrete (OPC). The mechanical strength of concrete and bond strength of rebars in concrete before and after freeze-thaw cycles were measured. It was found that the frost resistance of G10 was the weakest followed by OPC and G50. Three scenarios of bending tests on reinforced concrete beams were included: (1) control (without freeze-thaw damage); (2) individual freeze-thaw cycling; (3) coupling effect before bending. Rebound tests were conducted to evaluate frost damages at different areas of the beams as the base to analyze bending behaviors of the beams. The failure mode, load-displacement(strain) relationship, ultimate flexural strength, and bending stiffness of beams from bending tests are analyzed. All beams in scenario (1) were dominant in flexural failure. For scenario (2), G10 and G50 failed in debonding failure due to significant reduction in bond strength, while OPC failed in diagonal tension failure as OPC could sustain bond stiffness, thus preventing debonding failure. For scenario (3), damages in GPC were exacerbated, while damages in OPC were limited.

Experimental Evaluation of Mechanical Properties, Micro Structure and Post-Fire Strength of Fiber Reinforced Geopolymer Concrete

Geopolymer mixtures offer an enhanced alternative to implement an eco-friendly solution in construction industry. These mixtures exhibit similar or better mechanical and structural properties in comprising of cement and can use recycling and by-product materials. Against this background, an eco-friendly advantageous were achieved from the engineers and researchers by using waste materials to replace cement and attention to reduce CO2 emission during its procedure. This study attempted to evaluate compressive and tensile strength, micro structure and post-fire characteristic of the geopolymer mixtures. For this aim, the geopolymer mixtures were exposed to elevated temperature between 200, 500 and 800 0C. Then, the post-fire and mechanical behaviour were investigated. The proposed research supported the slight decrease in the GPC's compressive stress by fibres, and the 1.25% PP fibres displayed the least performance, indicating nearly 13% decrease than the unreinforced mixtures. As exhibited by the post-fire behaviour of mixtures, the GPC's compressive strength increased first for all mixes but in the range of 400 - 800°C it decreased at a higher rate because of the geopolymer matrix-related dehydration. Besides, fiber melting under high temperatures and the thermal reaction procedure related to free water evaporation reduce the mechanical properties under temperatures ranging from 400°C to 800°C. DOI: https://doi.org/10.52783/pst.349

Experimental and Analytical Investigations on Shear Performance of Ambient-Cured Reinforced Geopolymer Concrete Beams

Geopolymer concrete (GPC) has emerged as a sustainable alternative to ordinary Portland cement concrete (OPCC) as GPC significantly reduces embodied carbon dioxide emissions. This study compared the shear behavior of reinforced OPCC beams and GPC beams of the same cross-section and compressive strength. The study tested nine beams under three-point bending to evaluate the effects of concrete type and shear span on the shear strength. The results showed that OPCC and GPC beams exhibited relatively similar reduction rates in the shear strength with increasing a/d ratios, while the failure mode shifted from shear in OPCC beams to shear-flexure in GPC beams. The maximum deflection of GPC beams significantly increased with increasing a/d ratios. Moreover, empirical shear strength equations, intended for OPCC beams in various design codes, underestimated the shear strength of GPC beams by about 11.0-26.9% at the a/d ratio of 4.3 but significantly underestimated the shear strengths of GPC beams by 77% at lower a/d ratios of 1.6 and 2.9. Therefore, modifications are proposed to the existing design OPCC shear strength equations to significantly improve the prediction accuracy for the shear strength of GPC beams.

Behavior of Reinforced Geopolymer Concrete Beams under Repeated Load

Behavior of Reinforced Geopolymer Concrete Beams under Repeated Load

Experimental investigation and numeric modelling of the impact performance of basalt fiber reinforced geopolymer concrete

Geopolymer concrete (GC) has been found to have better results than Portland cement concrete (PCC), including lower carbon dioxide emissions, higher compressive strength, and greater durability. The study aims to determine the effects of basalt fiber on GC due to the impact caused by the sudden loading effect. Samples were prepared with different mixing ratios for the experimental process, with PCC used as the control sample. Basalt fibers were added to the samples in three different ratios based on optimal mixing ratios determined through physical and mechanical tests, such as UPV (Ultrasonic Pulse Velocity), compressive strength, and flexural strength. Subsequently, fibrous samples were analyzed using SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). A drop-weight experiment was conducted on GC plates measuring 50×50×5 cm, which contained two different fiber ratios that yielded the best mechanical and physical properties. The results were analyzed using numerical modeling methods. No changes in content were made. The sample with the highest impact resistance was found to be the 2% basalt fiber-reinforced GC, with a displacement value 21.21% lower than PCC. The language used is clear, concise, and objective, with a formal register and precise word choice. The text follows a logical structure with causal connections between statements and adheres to conventional academic formatting and citation styles. The ANSYS modeling results indicated an 89.63% similarity with the experimental data regarding the displacement values. Additionally, the study demonstrated that the inclusion of basalt fiber additives enhances the impact resistance of geopolymer concrete. Furthermore, numerical modeling can predict the impact behavior of concrete to a significant extent, eliminating the need for experimental processes.

Optimizing Fiber Reinforced Geopolymer Concrete: Investigating Alkaline-Activator Liquid to Fly Ash and Sodium Silicate to Sodium Hydroxide Ratio

Optimizing Fiber Reinforced Geopolymer Concrete: Investigating Alkaline-Activator Liquid to Fly Ash and Sodium Silicate to Sodium Hydroxide Ratio

Modulus of Elasticity of Flyash-Slag Based Reinforced Geopolymer Concrete Flexural Elements

Modulus of Elasticity of Flyash-Slag Based Reinforced Geopolymer Concrete Flexural Elements

Corrosion Resistance of High Calcium Fly Ash Based Reinforced Geopolymer Concrete in Marine Environment

Corrosion Resistance of High Calcium Fly Ash Based Reinforced Geopolymer Concrete in Marine Environment

Dynamic tensile properties of geopolymer concrete and fibre reinforced geopolymer concrete

Geopolymer concrete (GPC) has attracted much attention over the past decades because it utilizes industry wastes and has outstanding mechanical properties. To improve its ductility and energy absorption capabilities, various types of fibres have been incorporated into GPC. This paper carries out an experimental study to quantify the dynamic tensile properties of GPC and fibre reinforced GPC (FR-GRC) with hooked-end steel fibre and polypropylene (PP) fibre. Both quasi-static and dynamic split-tensile tests are performed on plain GPC and FR-GPC covering strain rates of 10-5s−1 to 16 s−1. The addition of 0.5% volume content of steel and PP fibres is found to effectively improve the ductility of GPC at both static and dynamic states. Under quasi-static loading, the crack opening displacements reach about 0.15 mm for GPC, 9 mm for SGPC and 8 mm for PPGPC upon failure, and when subjected to impact loading, the crack-opening rate of GPC is higher than that of FR-GPC. Fibre stretching process after concrete crack till pull-out/fracture is observed which considerably contributes to the reduction of crack expansion and the enhancement of energy dissipation capacity of GPC, with enhancements reaching up to 33% for PPGPC and 94% for SGPC. The split-tensile properties of both plain GPC and FR-GPC are found to be sensitive to strain rate, while geopolymer with PP fibre shows a similar behaviour as plain geopolymer, and GPC with steel fibres appears to be less sensitive to strain rate effect. Empirical relations are proposed to correlate the dynamic increase factor (DIF) of tensile strength for GPC and FR-GPC with strain rate. Comparison between plain GPC and FR-GPC shows that fibres can absorb additional energy to improve the impact resistance and deformation capacities.

The effect of polypropylene fiber on the mechanical properties between hybrid fiber geopolymer concrete and geopolymer concrete in elevated temperature

This paper has influence on discovering the behavior of hybrid polypropylene fiber reinforced geopolymer concrete under constant and elevated temperature with the purpose to determine the mechanical properties of the material. While the expertise and acquaintance with concrete behavior under constant temperature are well known, the behaviour under elevated temperature has to be seriously explored. This study objectives is to match between the mechanical properties of unburnt and burnt fiber reinforced geopolymer concrete. This study uses experimental investigation. Compression and splitting tensile tests were conducted on the 150 mm cilinder mold. Meanwhile, flexural tension test was conducted on 100 mm x 100 mm x 450 mm rectangular mold. The result of both materials, without set fire to and with set fire to, are analyzed. The gained findings for burnt material are the compression test value cut down, otherwise, the splitting tensile test and flexural tensile strength grade increase.

Experimental Investigation and Flexural behavior of Reinforced Geo polymer Concrete Beam by RCA

This research report presents the study on material characteristics of GPC by using natural aggregate and Recycled Coarse Aggregate. Experiments were conducted on the effect of variation of alkaline solution and different molarities on the mechanical properties of GPC. The alkaline liquid used for the present study was sodium silicate and sodium hydroxide solution with varying ratios of 2, 2.5 and 3. The molarities chosen for the sodiumhydroxidesolutionwere8M, 10Mand14M.Thetestspecimenswere150mmsizecubesand100x200mmcylindersheat-cured at 60 Cinanoven. The compressive strength was about 18to39 MP a and split tensile strength was in the range of3to3.8MParespectively.In this investigation on GPC using RCA, a total of 9 mixes were cast and tested, out of which three were conventional concrete mixes and six GPC mixes having varying combinations of fly ash, GGBS and RCA. The test specimens were 100mm size cubesand100x200mmcylinderscuredat90°Cinanovenfor18hours.Furthsize 150mm GPC cube specimens were cured at ambient temperature conditions. The studies showed that the compressive strength and spilt tensile strength of different mixes decreased with the increase in the percentage of recycled coarse aggregates.

Structural behavior of reinforced geopolymer concrete beams – A review

A potential novelconstructionmaterial that is relativelyeco-friendly in manufacturing and has a comparatively low carbon footprint is geopolymer concrete (GPC). GPC is a largely unexplored topic in the literature due to its novelty as a material, particularly in terms of itsstructural behaviour. Reinforced concrete (RC) beams are the most common concrete application in the construction industry. Therefore, this review study intends to provide a greater understanding of GPC by summarizing and discussing the most updated data on the structural performance of reinforced geopolymer concrete (RGPC) beams. The evaluation highlights the flexural and shear behaviour of RC beams made with GPC and compared with those of ordinary Portland cement concrete (OPCC). The reported literature demonstrated that the structural behaviour of RGPC beams is comparable to that of conventional OPCC beams. Further, the failure mode of RGPC beams in flexure and shear was nearly identical to that of OPCC beams. Review of the literature showed that GPC beams might be employed safely with the existing standards. However, to assure its viability in the industry, full-scale investigations on the structural behaviour are required for mass use in a variety of application areas and to promote cleaner and sustainable choices in the construction industry. Overall, this review offers guidance for researchers and civil engineers in conducting future studies on GPC.

Modeling of strength properties of Geo polymer concrete beam

Concrete is most versatile material used in construction process. Portland cement is most used material in India for upcoming innovative projects. Cement replacement process is being used by adding Ground granulated blast furnace slag (GGBS) and FLYASH. Continuous use of lime stone for manufacturing of cement will affect the environment. Manufacturing of cement produces carbon dioxide and it effects the environment and human health. In this study cement has been replaced with GGBS and FLYASH to reduce the carbon dioxide. Geo polymer concrete is presently used to construct huge structures. The aim of present study was to measure the strength properties of concrete made of several compositions of geo-polymer and model the strength parameters using different mathematical equations. Compression strength increased from 17.25 MPa to 37.25 MPa from in the time period of 7 days to 28 days for conventional specimen. In case of GPC samples the compression strength increased from 21.4 to 43.6 MPa for the same period of time. For HFRGPC5 the compression strength has been increased from 26.02 MPa to 52.36 MPa within the same time period. Compression strength results indicated that Hybrid Fiber Reinforced Geo polymer Concrete 5 has better strength properties compared to all other compositions of Hybrid Fiber Reinforced Geo polymer Concrete. Polynomial model fitted the best with highest R square value compared to linear and exponential equations.

A Review on Fresh, Hardened, and Microstructural Properties of Fibre-Reinforced Geopolymer Concrete

Alternative eco-friendly and sustainable construction methods are being developed to address growing infrastructure demands, which is a promising field of study. The development of substitute concrete binders is required to alleviate the environmental consequences of Portland cement. Geopolymers are very promising low-carbon, cement-free composite materials with superior mechanical and serviceability properties, compared to Ordinary Portland Cement (OPC) based construction materials. These quasi-brittle inorganic composites, which employ an "alkali activating solution" as a binder agent and industrial waste with greater alumina and silica content as its base material, can have their ductility enhanced by utilising the proper reinforcing elements, ideally "fibres". By analysing prior investigations, this paper explains and shows that Fibre Reinforced Geopolymer Concrete (FRGPC) possesses excellent thermal stability, low weight, and decreased shrinking properties. Thus, it is strongly predicted that fibre-reinforced geopolymers will innovate quickly. This research also discusses the history of FRGPC and its fresh and hardened properties. Lightweight Geopolymer Concrete (GPC) absorption of moisture content and thermomechanical properties formed from Fly ash (FA), Sodium Hydroxide (NaOH), and Sodium Silicate (Na2SiO3) solutions, as well as fibres, are evaluated experimentally and discussed. Additionally, extending fibre measures become advantageous by enhancing the instance's long-term shrinking performance. Compared to non-fibrous composites, adding more fibre to the composite often strengthens its mechanical properties. The outcome of this review study demonstrates the mechanical features of FRGPC, including density, compressive strength, split tensile strength, and flexural strength, as well as its microstructural properties.

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.

Corrosion of steel rebars embedded in One-part Alkali activated concrete mixes

To reduce CO2 emissions and turn a variety of industrial/agricultural wastes into valuable cementitious products, alkali-activated materials (AAM) are recognized as suitable substitutes for regular Portland cement (OPC). However, the concentrated aqueous alkali solutions used in conventional two-part alkali activated materials are highly corrosive, viscous, and are difficult to handle in direct field applications. As a result, the potential for developing so-called "just add water" type one-part AAMs, as compared to traditional two-part AAM, is being explored, particularly in cast-in-situ applications. In the present study on corrosion of reinforcing steel bars in fly ash-slag (FA-GGBS) based one-part AAC mixtures, three parameters—the total binder content, the relative proportions of GGBS and Fly-ash and the percentage of sodium oxide (Na2O) - are recognized as the key factors in determining the strength and durability performance (including corrosion of rebars embedded in it) of a given AAC mix. Accordingly, experiments were conducted on AAC mixes with three binder contents (440, 460, and 480 kg/m3), three Slag/FA ratios (80/20, 70/30 and 60/40, by volume) and three alternate Na2O percentages (5, 6, and 7%, by weight of total binder content). Prismatic cylindrical test specimens of reinforced geopolymer concrete were prepared and half-cell potential and corrosion rate measurements were made after 28-, 56-, and 90 days of continuous exposure to 3% of NaCl solution, to accelerate the corrosion process. Measured corrosion current density and corrosion rates using a Electro-chemical Corrosion Analyser have indicated that the AAC mixture having a total binder content 440 kg/m3, GGBS/FS ratio of 70/30 and 6% Na2O content, exhibits best corrosion resistance amongst the various mixes tested herein, as measured up to the end of 90-days.

Behaviour of Hybrid Fiber Reinforced Geopolymer Concrete Beams under Flexural Loading

This paper presents the behaviour of GPC beams with and without fiber under flexural loading. The work is presented in two parts. In the first part tests were conducted for mechanical properties of plain and hybrid fiber reinforced Geopolymer concrete to determine maximum strength characteristics of concrete. In the second part of the program two types of under-reinforced beams were cast with plain GPC and hybrid fiber reinforced GPC (HFRGPC) and tested under two points loading. The percentage of tensile rebar ratio is kept constant for two types of beams. The hybrid fiber reinforced GPC is prepared with 1.5%(1%Steel+0.5% Polypropylene) of fibers and used to cast the under reinforced beams .The cast specimens are tested after a specified curing period to determine first crack load, ultimate load, load-deflection behaviour and crack patterns. The results are compared with the theoretical values. From the test results, the fiber volume fraction has a compelling effect on the cracking load, ultimate load, crack pattern and failure mode. The flexural behaviour of the beams including the induced cracks, failure pattern, load deflection capacity and ductility index were compared. The ductility index of hybrid fiber reinforced beams is greater than that of GPC beams. The HFRGPC beams showed superior performance than that of GPC beams for parameters considered in this experimental study.

Comparative study of compressive strength of novel steel fiber reinforced geopolymer concrete and conventional concrete

The main aim of this study is to quantify the influence of steel fiber on the compressive strength of the geopolymer concrete. There were 2 groups taken for this study and a total of 18 samples were prepared per group. Many samples were calculated using clinical software by adopting the values from the old research papers. Different types of materials and apparatus were used during the preparation and testing of the samples. SPSS software, version 21 has been used to carry out the independent sample T-test. The mean compressive strength of geopolymer concrete with novel steel fibre sample is 32.2 N/mm2and the mean compressive strength of conventional concrete sample is 28.15 N/mm2. Independent samples t-test is performed to analyse the results. The significance(p) of the events was 0.115 (p > 0.05). It doesn't show any significant difference. The standard deviation of steel fiber reinforced geopolymer concrete was 75.73658. From this experimental study, it is concluded that the steel fiber reinforced M20 grade geopolymer concrete has a greater compressive strength than conventional concrete.