Search Results (10)

One of the important findings of the recent decades in the construction industry is composite sandwich panels (CSPs), which have benefits of being lightweight, providing thermal insulation, and aiding the economy; they are transforming continuously through many add-ons as needed by the industry. With the demand for sustainability in the field, CSPs need structural and sustainable enhancement. In the present study, an approach for the same has been attempted with geopolymer concrete (GPC) and novel nylon fibre to improve the sustainability and structural benefits, respectively. With various material combinations including GPC reinforced with fibres, six CSPs were cast and studied. The inherent limitations of GPC have been addressed by the nylon fibre reinforcement instead of using steel fibres, which have a similar strength, considering the aim of maintaining the density of the wythe material. A comparison of the flexural behaviour of the CSPs through the parameters of load–deflection, ductility, and toughness was made using the four-point loading test. The results of the test specify that the fibres enhance the performance of the CSPs under flexural loading. Full article

This paper presents an innovative flexural repair technique for pre-damaged reinforced concrete T-beams using eco-friendly steel-fibre-reinforced geopolymer concrete (SFRGPC). The study considers various parameters such as repair layer depth, location and configuration, and the use of additional reinforcement in one beam. The beams were preloaded to 50% of their ultimate flexural capacity. Extensive measurements were taken, including crack initiation and propagation, crack width, initial stiffness, load deflection, peak loads, ductility index, and strain values. The structural performance of the repaired T-beams under flexural loading was predicted using an analytical model. The repaired beams showed an increase in carrying capacity, stiffness, and ductility, but the failure mode was identical to the control samples. The study shows that SFRGPC shows great promise as a technique for not only repairing pre-damaged reinforced concrete beams but also for their strengthening. The best results were obtained with three-sided jackets with fibrous geopolymer concrete only, resulting in a load-carrying capacity increase of 25.8% compared to reference T-beams. The bonding between SFRGPC and existing concrete was effective, with no slippage or disintegration at the interface. The repaired beams’ structural behaviour and performance under flexural loads were successfully predicted using the analytical model, with a precision of about 98%. Full article

The fire resistance of construction materials is an essential part of safety requirements in the construction industry. In this work, experimental investigations were conducted to understand the thermal behaviour, spalling, transfer characteristics, strength, and microstructures of self-cured high-strength plain (HSGC) and steel-fibre-reinforced geopolymer concrete (S–HSGC) under severe fire scenarios with peak temperatures of 275, 560, and 825 °C; the peak was maintained for a period of 120 min after reaching it. Forty-eight standard cylindrical specimens for each mixture were prepared to test and analyse their time–heat response, gradients, visual appearance, spalling, density change, water absorption, and compressive strength before and after fire exposure. Additionally, Scanning Electron Microscopy (SEM) along with Energy Dispersive X-ray Analysis (EDX) were utilised to analyse the internal structures and phase transformations. The thermal analysis showed that no cases of explosive spalling were recorded during sample exposure to various fires, while the used hook-end steel fibres had an influence on the considered test variables. The sample cores almost reached the target heat, and the thermal saturation degree at the peak ranged from 55 to 97%. The experimental findings also revealed slight surface cracking after exposure to 560 °C fires, while the surface cracking was more obvious for specimens exposed to 825 °C. Moreover, the residual compressive strength of the S–HSGC at various fires was noticeably 10.20% higher than that of the HSGC. Also, state-of-the-art research data were used to discuss the prediction model’s performance. The SEM and EDX results showed that the self-cured geopolymerization process was effective and successful in producing gels, in addition to the significant phase transformations in microstructures at different fires. This study presented sophisticated data on the behaviour of HSGC and S–HSGC exposed to fires up to 825 °C. Full article

Beam–column joints are extremely vulnerable to lateral and vertical loads in reinforced concrete (RC) structures. This insufficiency in joint performance can lead to the failure of the whole structure in the event of unforeseen seismic and wind loads. This experimental work was conducted to study the behaviour of ternary blend geopolymer concrete (TGPC) beam-column joints with the addition of hybrid fibres, viz., steel and polypropylene fibres, under reverse cyclic loads. Nine RC beam-column joints were prepared and tested under reverse cyclic loading to recreate the conditions during an earthquake. M55 grade TGPC was designed and used in this present study. The primary parameters studied in this experimental investigation were the volume fractions of steel fibres (0.5% and 1.0%) and polypropylene fibres, viz., 0.1 to 0.25%, with an increment of 0.05%. In this study, the properties of hybrid fibre-reinforced ternary blend geopolymer concrete (HTGPC) beam-column joints, such as their ductility, energy absorption capacity, initial crack load and peak load carrying capacity, were investigated. The test results imply that the hybridisation of fibres effectively enhances the joint performance of TGPC. Also, an effort was made to compare the shear strength of HTGPC beam-column connections with existing equations from the literature. As the available models did not match the actual test results, a method was performed to obtain the shear strength of HTGPC beam-column connections. The developed equation was found to compare convincingly with the experimental test results. Full article

Geopolymer concrete is one of the innovative eco-friendly materials that has gained the attention of many researchers in the sustainable development of the construction industry. The primary objective of this experimental investigation is to study the flexural behaviour of the ternary blend geopolymer concrete (TGPC) with various proportions of hybrid fibres. In this study, 27 reinforced concrete beams were cast with a TGPC grade of M55 and tested under monotonic loading conditions. The specimens were beams of length 1200 mm, depth of 150 mm, and width of 100 mm. Crimped steel (metallic) fibres and polypropylene (non-metallic) fibres were used in hybrid form to study the effect on the TGPC beams under flexure. The volume fractions of steel fibres were varied up to 1% with an increment of 0.5%, and polypropylene fibres varied from 0.1% to 0.25% with an increment of 0.05%. The test results were analysed based on the first crack load, ultimate load, load-deflection behaviour, energy absorption capacity, moment-curvature relationship, and ductility behaviour and compared with TGPC specimens without fibres. The experimental study reveals that the TGPC is one of the best alternatives for conventional cement concrete. The addition of hybrid fibres potentially improves the flexural properties of TGPC to a great extent. The test results showcased that the HTGPC with 1% steel and 0.1% polypropylene fibres exhibited better flexural properties than the other combinations of hybrid fibres considered in this study. Additionally, an effort was made to develop a model to estimate the flexural strength of TGPC with hybrid fibres, and the predicted values were found satisfactorily with the test results. Full article

This study seeks to evaluate the effectiveness of glass-FRP-reinforced geopolymer concrete columns integrating hybrid fibres (GFGC columns) and steel bar-reinforced geopolymer concrete columns incorporating hybrid fibres (SFGC columns) under eccentric and concentric loadings. Steel fibre (SF) and polypropylene fibres (PF) are two types of fibres that are mixed into hybrid fibre-reinforced geopolymer concrete (HFRGC). Eighteen circular concrete columns with a cross-section of 300 mm × 1200 mm were cast and examined under axial loading up to failure. Nine columns were cast with glass-FRP rebars, whereas the other nine were cast with steel rebars. Using ABAQUS, a nonlinear finite element model was established for the GFGC and SFGC columns. The HFRGC material was modelled using a simplified concrete damage plasticity model, whereas the glass-FRP material was simulated as a linear elastic material. It was observed that GFGC columns had up to 20% lower axial strength (AST) and up to 24% higher ductility indices than SFGC columns. The failure modes of both GFGC and SFGC columns were analogous. Both GFGC and SFGC columns revealed the same effect of eccentricity in the form of a decline in AST. A novel statistical model was suggested for predicting the AST of GFGC columns. The outcomes of the experiments, finite element simulations, and theoretical results show that the models can accurately determine the AST of GFGC columns. Full article

The need to promote sustainable civil infrastructure is one of the most important concerns in the construction industry. Geopolymer composites are one of the promising eco-friendly materials for the development of low carbon concrete. The main objective of this experimental investigation is to study the effect of hybrid fibres on the shear strength of flexural members made with ternary blend geopolymer concrete (TGPC). A total number of 27 reinforced concrete beams of size 100 mm × 150 mm × 1200 mm were cast and tested for shear. M55 grade of concrete was considered in this study. Crimped steel fibres and polypropylene fibres with an aspect ratio of 66 and 300, respectively, were used in this work. The main variables considered in this investigation involve two volume proportions of steel fibres, viz., 0.5% and 1% as well as four volume proportions of polypropylene fibres viz., 0.1%, 0.15%, 0.2% and 0.25%. The hybrid fibre-reinforced ternary blend geopolymer concrete (HTGPC) beams were compared with TGPC beams without fibres. From the test results, it was clear that incorporating hybrid fibres improved the shear strength and changed the type of failure of the beam from shear to flexure. Moreover, a method to predict the ultimate shear strength of HTGPC was proposed, and the estimated values were found to be the same as the test results. Full article

The need to develop sustainable concrete in the civil infrastructure industry increases day by day, resulting in new eco-friendly materials such as geopolymer concrete. Geopolymer concrete is one of the eminent alternatives to conventional concrete for sustainable development by reducing the carbon footprint. Ternary blend geopolymer concrete (TGPC) is a sustainable and environmentally friendly concrete produced with three different source materials to form a binder. The main advantage of TGPC is that it possesses densely packed particles of different shapes and sizes, which results in improved properties. This paper deals with the experimental investigations to evaluate the durability properties of plain and hybrid fibre reinforced TGPC. The durability of concrete is defined as the ability to withstand a safe level of serviceability and different environmental exposure conditions without any significant repair and rehabilitation throughout the service life. Conventional concrete is vulnerable to cracking due to its low tensile and durability properties. The TGPC considered in this work consists of fly ash, GGBS and metakaolin as source materials, selected mainly based on the material’s silica and alumina content, shape, size, and availability. The grade of concrete considered was M55. The main variables considered in this study were the proportions of crimped steel fibres (V_f), viz., 0.5% and 1% and proportions of polypropylene fibres (V_p)viz., 0.1%, 0.15%, 0.20% and 0.25%. The durability properties like water absorption, sorptivity, resistance to marine attack, acid attack, sulphate attack, and abrasion were studied in this investigation. The experimental test results were compared with the requirements provided in the standard/literature and found to be well within limits. The study also indicates that the inclusion of fibres in a hybrid form significantly improves the durability parameters of TGPC. The TGPC with 1% steel fibre and 0.15% polypropylene fibre performs better than the other combination of fibres considered in this experimental investigation. Full article

The possibility of using geopolymer instead of Portland cement could effectively reduce carbon dioxide emissions from cement manufacturing. Fibre-reinforced self-compacting geopolymers have great potential in civil engineering applications, such as chord member grouting for concrete-filled steel tubular truss beams. However, to the best of the authors’ knowledge, the quantitative relationship between FF and the properties of the fibre-reinforced geopolymer has been rarely reported. In this research, 26 groups of mixtures were used to study the influence of the polypropylene fibre factor (FF) on the flowability and mechanical properties and also the compactness of the fibre-reinforced self-compacting geopolymer. At the same volume fraction, geopolymers with long fibres present worse flowability than those having short fibres due to the easier contacting of long fibres. By growing the FF the influence of fibre addition on the V-funnel flow rate is more significant than the slump spread. This can be ascribed to the consequence of fibre addition and friction by the V-funnel which estimates the restrained deformability. For FF lesser than critical factor Fc = 100, influence of fibres is negligible and fibres are far apart from each other and, thus, they cannot restrict cracking under load and transfer the load to improve the mechanical properties. For FF between the Fc = 100 and density factor Fd = 350, a noteworthy enhancement of mechanical properties was obtained and the geopolymer was still adequately workable to flow by weight of self, without any symbols of instability and fibre clumping. Under this condition, better fibre dispersal and reinforcing productivity can lead to better hardened properties. For FF higher than Fd = 350, fibres tend to come to be entwined together and form clumping resulting from the fibre balling, resulting in worse hardened properties. This research offers a sensible basis for the application of the workability regulator of the fresh properties of fibre-reinforced geopolymer as an operative way to basically obtain ideal mechanical properties. Full article

The current research on concrete and cementitious materials focuses on finding sustainable solutions to address critical issues, such as increased carbon emissions, or corrosion attack associated with reinforced concrete structures. Geopolymer concrete is considered to be an eco-friendly alternative due to its superior properties in terms of reduced carbon emissions and durability. Similarly, the use of fibre-reinforced polymer (FRP) bars to address corrosion attack in steel-reinforced structures is also gaining momentum. This paper investigates the bond performance of a newly developed self-compacting geopolymer concrete (SCGC) reinforced with basalt FRP (BFRP) bars. This study examines the bond behaviour of BFRP-reinforced SCGC specimens with variables such as bar diameter (6 mm and 10 mm) and embedment lengths. The embedment lengths adopted are 5, 10, and 15 times the bar diameter (d_b), and are denoted as 5 d_b, 10 d_b, and 15 d_b throughout the study. A total of 21 specimens, inclusive of the variable parameters, are subjected to direct pull-out tests in order to assess the bond between the rebar and the concrete. The result is then compared with the SCGC reinforced with traditional steel bars, in accordance with the ACI 440.3R-04 and CAN/CSA-S806-02 guidelines. A prediction model for bond strength has been proposed using artificial neural network (ANN) tools, which contributes to the new knowledge on the use of Basalt FRP bars as internal reinforcement in an ambient-cured self-compacting geopolymer concrete. Full article