Elevated Temperature Resistance Research Articles

Interface bonding characteristics of 3D printed ultra-high performance concrete after elevated temperatures

This study explored the influence of elevated-temperature exposure and interlayer time intervals on the interface bonding strength of hybrid-fibre 3D printed ultra-high-performance concrete (3DP-UHPC), and analysed the potential mechanisms driving these observed results. A relationship model for the bonding strength of hybrid fibre 3DP-UHPC in elevated-temperature environments was proposed. Results revealed that at 800 °C, localized damage occurred in 3DP-UHPC, but the addition of 0.5 % polypropylene fibres delayed the occurrence of spalling behaviour and enhanced its elevated-temperature resistance. Furthermore, as the time interval increased, the bonding strength of 3DP-UHPC gradually decreased, particularly at temperatures above 400 °C, where the melting and volatilization of polypropylene fibres negatively affected the bonding strength. The study suggested that polypropylene fibres inhibited spalling behaviour of 3DP-UHPC after elevated temperatures through moisture loss and thermal stability. However, they may also lead to interface weakening, resulting in a decrease in bonding strength. These findings provide important guidance for further development and design of 3DP-UHPC structures in elevated-temperature environments.

Durability and ecological assessment of low-carbon high-strength concrete with short AR-glass fibers: Effects of high-volume of solid waste materials

The goal of this research is to improve the mechanical characteristics and durability of concrete while adhering to green and sustainable development principles. Portland cement (PC) was replaced with ceramic waste powder (CWP), glass powder (GP), and granite waste powder (GWP) to create the low-carbon, high-strength concrete (HSC). These materials were incorporated at 0–50% as a partial replacement of PC. The short alkali-resistant (AR-) glass fiber content was added by 1.0% of the PC content. The changes in strength, microstructure, pore structure, as well as ecological assessment of HSCs was investigated. Various experiments on the durability properties and elevated temperature resistance of HSC were performed. The experimental results show that mechanical properties of HSC with 10%GP and 20%GWP were maximally enhanced at 28d, while the mechanical properties of HSC with 50% of all wastes are decreased. It was found also that HSC containing CWP showed significant reductions in carbonation depth (up to 65.89% lower than the control mixture), especially at higher replacement levels. Furthermore, the increment in substitution level of CWP has found an increment in pore volume, resulting in a reduction in preliminary strength performance. It was observed that a 50% substitution level of GP and GWP reduced the water penetration depth by 47.71% and 65.7% compared to the control mixture, respectively. The residual strength after 600 °C exposure for 10%CWP, 10% GP, and 20% GWP retained about 34.10%, 32.32%, and 43.29%, respectively, from their original strength. XRD tests and SEM micrographs showed that adding 10%GP and 20%GWP improve the hydration reactions. Finally, environmental assessments revealed that incorporating CWP, GP, and GWP into HSC led to reduced costs, energy consumption, and carbon footprint.

Effect of GGBS Content and Water/Geopolymer Solid Ratio on the Mechanical, Elevated Temperature Resistance, and Sorptivity Properties of FA/GGBS-Based Geopolymer Concrete

Effect of GGBS Content and Water/Geopolymer Solid Ratio on the Mechanical, Elevated Temperature Resistance, and Sorptivity Properties of FA/GGBS-Based Geopolymer Concrete

Reusing Ceramic Waste as a Fine Aggregate and Supplemental Cementitious Material in the Manufacture of Sustainable Concrete

A viable strategy for promoting sustainable development and a cleaner environment is the reuse of demolition-related ceramic waste and ceramic manufacturing byproducts in the production of concrete. The purpose of this study is to assess the possibilities for using ceramic waste in the production of concrete as a fine aggregate and cementitious material. The effectiveness of concrete mixtures incorporating 20–100% ceramic waste fine (CWF) as a replacement for natural fine aggregate and 10–30% ceramic waste powder (CWP) in place of cement was evaluated. Their influence was assessed with respect to workability, mechanical performance, durability, and elevated temperature resistance. The results were analyzed via energy dispersive x-ray (EDX) and scanning electron microscopy (SEM). The findings illustrated that the increase in the replacement levels of CWP and CWF decreases the concrete workability. The mechanical performance of concrete mixtures is enhanced under compression and flexural tests as the replacement ratios of CWF and CWP increase up to 50% and 10% as replacements of sand and cement, respectively. The increases in compressive and flexural strength were 5.33% and 8.14%, respectively, at age 28 days. The concrete water permeability significantly increases as the CWF replacement ratio increases, and the incorporation of CWP reduces this negative impact. After exposure to 200, 400, 600, and 800 °C, the residual compressive strengths of concrete mixtures incorporating CWF and CWP were up to 95.02%, 89.66%, 74.33%, and 51.34%, respectively, compared to control mixtures, which achieved 84.25%, 76.03%, 59.36%, and 35.84% of their initial strength. Microstructure analysis revealed that combining CWP and CWF significantly improves cement hydration when compared to the reference mixture. Thus, the use of CWF and CWP in the production of masonry mortar might be an economical alternative that would aid in raising the recycling rate of demolition and construction debris and supporting sustainable growth in the building sector.

Optimizing characteristics of high-performance concrete incorporating hybrid polypropylene fibers

The purpose of this investigation is to assess and optimize the impact of hybrid polypropylene fibers (coarse monofilament and staple fibers) on the mechanical characteristics and resistance to elevated temperature of high-performance concrete. Concrete mixtures were designed using central composite design under response surface methodology. Slump test, compressive strength, flexural strength, impact test, elevated temperature resistance and microstructure of concrete were the tests performed. The slump values were slightly decreased with the addition of polypropylene fibers. Concrete mixtures reinforced with hybrid polypropylene fibers have significantly improved in terms of compressive strength and flexural strength ranged from 1.96% to 12% and 14.28% to 41.9%, respectively, at age 56 days compared to control mixture without fibers. The hybridization of 5 kg monofilament and 0.75 kg staple fibers achieved the highest compressive strength (84.6 MPa), flexural strength (14.9 MPa), and the optimum impact resistance at age 56 days. The increase of coarse monofilament fibers significantly improved the spalling resistance performance. The residual compressive strength of mixture containing 5 kg monofilament and 0.75 kg staple fibers up to 63.8% of the initial strength after exposure to 800 C0. Strong relationships were obtained for predicting and optimizing compressive and flexural strength of concrete incorporating hybrid polypropylene fibers.

Strength and elevated temperature resistance properties of the geopolymer paste produced with ground granulated blast furnace slag and pumice powder

The production of cement results in large amounts of CO2 emissions. In order to reduce the energy consumption and gas emissions associated with cement production, a new technology called geopolymerisation has been developed to produce concrete without the use of cement by using aluminosilicate materials as raw materials. The purpose of this study is to evaluate the effect of various parameters on the geopolymer based slag/pumice paste. Slag (GGBFS) and pumice powder were used as binders in different slag/pumice ratios (100:0, 90:10, 80:20, 70:30 and 60:40) and activated with sodium hydroxide (NaOH) at 12 and 14 M concentration and cured for 3 and 7 days at 65 °C temperature. The effect of these parameters on compressive strength and resistance to elevated temperatures was investigated. Microstructural (SEM, EDX) and chemical (FT-IR, XRD) analyses were also carried out to determine the effect of slag/pumice ratio, NaOH concentration and curing time on the properties of the geopolymer pastes. The results showed that the use of slag significantly increased the compressive strength, while the use of pumice with slag increased the resistance of geopolymer pastes to elevated temperatures. For the geopolymer paste produced with slag, high compressive strength can be obtained by a long period of oven curing, whereas for pumice a short period of oven curing and a long period at low temperature can be used. In conclusion, the most effective of the different parameters was the percentage of slag/pumice in the first degree and then the molarities of NaOH, while the least effective parameter was the curing time.

A Review on Durability of Foam Concrete

Foam concrete is a promising material in building and construction applications, providing such outstanding properties as high specific strength, excellent thermal insulation, and effective acoustic absorption in human-inhabited buildings. However, because the porosity and permeable water absorption properties of foam concrete are significantly higher, its durability is often not comparable to that of ordinary concrete, and so the durability of foam concrete requires significant attention during the life cycle of building applications. Durable materials can greatly reduce the environmental impact of waste from maintenance and replacement and the consumption of natural resources resulting from the production of repair and replacement materials. After hardening, the durability of foam concrete includes freeze-thaw cycle resistance, elevated temperature resistance, carbonation resistance, efflorescence resistance, sulfate resistance, chloride resistance, alkali-silica reaction, and so on. This paper reviews articles on the durability of ordinary Portland cement (OPC) foam concrete, geopolymer foam concrete (GFC), magnesium phosphate cement (MPC) foam concrete, sulphoaluminate cement (SAC) foam concrete, and limestone calcined clay cement (LC3) foam concrete and compares their durability to provide a reference for the life cycle design and service life estimation of foam concrete members.

Performance of eco-friendly fly ash-based geopolymer mortars with stone-cutting waste

In this study, the physical and mechanical properties of the geopolymers formed by substituting red (RSW) and yellow (YSW) stone-cutting wastes into geopolymer mortars based on class F fly ash at 10–40 wt% rates were investigated. Sodium hydroxide (NaOH) solution was used as an activator in the production of the mortars. Produced samples were thermally cured at 90 °C for 24 h. Workability, unit weight, flexural strength, compressive strength, water absorption, porosity, and elevated temperature resistance tests (400, 600, and 800 °C) were applied to the produced geopolymer mortars. In addition, the chemical analysis (XRF), crystal phase analysis (XRD) of wastes/selected mortars, and microstructural analysis (SEM) of before and after elevated temparature resistance tests were carried out to investigate the effect of stone-cutting wastes on geopolymer mortars. SW up to 40% enhances mechanical strength up to 26–30.7 MPa from 16.4 MPa due to its high Si/Al ratios and Ca content and needle-like crystals formed by stone-cutting waste. The crystalline phases are determined to be mullite, quartz, anorthite, and zeolite derived from stone-cutting waste in the selected mortars. As a result, it was seen that the use of stone-cutting wastes up to 40% improved the physical, mechanical, and microstructural properties of fly ash-based geopolymer mortars.

Effect of addition diatomite powder on mechanical strength, elevated temperature resistance and microstructural properties of industrial waste fly ash-based geopolymer

Effect of addition diatomite powder on mechanical strength, elevated temperature resistance and microstructural properties of industrial waste fly ash-based geopolymer

Preparation and characterization of elevated and cryogenic temperature-resistant regolith-based epoxy resin composites

The construction of lunar bases, with their crucial role in future deep space exploration and extraterrestrial resource harvesting, requires the integration of multiple manufacturing techniques. Selecting appropriate solutions to meet the feature requirements is of particular importance. Extreme environments on lunar surfaces pose uphill challenges for construction, and transportation between Earth-to-Moon involves costs and risks. In-situ utilization of lunar regolith for fabrication has been proven feasible, among which polymer forming possesses promising prospects due to its sample manufacturing process, excellent mechanical properties, and low energy consumption. To investigate the feasibility of regolith-based polymer composites, specimens with varying proportions were prepared based on the Taguchi method. The lunar regolith simulants (LRS) and resulting polymer were characterized by laser particle analyzer and X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning electron microscopy (SEM). Their elevated (180°C) and cryogenic (-196°C) temperature resistance properties were investigated by compressive and flexural strength tests after shifting freeze–thaw cycle tests. The results revealed that curing temperatures and mass ratio of curing agents to the hybrid epoxy matrix significantly affect the compressive strength and flexural strength, respectively. The maximum 24 h compressive and flexural strength of regolith-based polymer composites was obtained as 156.22 MPa and 103.40 MPa, respectively. And remained stable over 160 MPa and 70 MPa after ten freeze–thaw cycles. Microstructural results imply variations in the curing agent’s and aggregate’s ratio, which tentatively explain the reaction mechanism of regolith-based polymer composites. This study demonstrates the feasibility of preparing polymer utilizing LRS that accommodates immense temperature fluctuation on the Moon, with undemanding fabrication, excellent mechanical properties, and low energy consumption, providing potential applications for future lunar construction, especially for rapid repair and reinforcement of launch pads and runways.

Effect of incorporating fibers in reactive powder concrete – A review

Modified form of High-Performance Concrete is a Reactive- Powder Concrete(RPC) which was first found by PierreRichard and Marcel Cheyrezy, they successfully built France laboratory using RPC. High compressive strength of over 200 MPa has been achieved, with flexural strength up to 40 MPa, and in certain cases crushing strengthup to 800 MPa with the introduction of hybrid fibre reinforcement. Cement OPC grade, silica fume, quartz sand, crushed quartz flour, water, a superplasticizer, and fibre reinforcement all contribute to making RPC.These materials have high durability characteristics as a result of their extremely low porosity, low permeability, limited shrinkage, and higher corrosion resistance. To increase package density, the powder combination of RPC should have a variety of granular particle classes. By dense packaging theory and grading optimization technique, the absence of coarse aggregate increased compactness. Because of its compactness, it reaches high strength. The rapid hydration of cement and silica fume at a high curing temperature of 100 °C as compete to 27 °C is something that causes the higher early strength. This paper discusses about the hybrid fibers incorporation in RPC under various curing conditions and its enhancement in strength than single fibers. Using micro and macro fibers dramatically improves the properties of RPC and thermal properties with various types of fiber. The mechanical characteristics of the RPC beam without the hybrid fiber, on the other end, are the lowest of all the mixtures. Apart from these characteristics, RPC can be utilized for industrial and nuclear waste storage facilities due to its ultra-dense microstructure, which provides ultra-high strength even at elevated temperature and water resistance. This paper infers that the addition of hybrid fiber in RPC considerably reduces the spalling of concrete at elevated temperatures and it exhibits superior strength and durability.

Experimental Evaluation of New Geopolymer Composite with Inclusion of Slag and Construction Waste Firebrick at Elevated Temperatures.

This study investigates the effect of elevated temperatures on slag-based geopolymer composites (SGC) with the inclusion of firebrick powder (FBP). There is a limited understanding of the properties of SGC with the inclusion of FBP when exposed to elevated temperatures and the effects of cooling processes in air and water. In this regard, in the preliminary trials performed, optimum molarity, curing temperature, and curing time conditions were determined as 16 molarity, 100 °C, and 24 h, respectively, for SGCs. Then, FBP from construction and demolition waste (CDW) was substituted in different replacement ratios (10%, 20%, 30%, and 40% by slag weight) into the SGC, with optimum molarity, curing temperature, and curing time. The produced SGC samples were exposed to elevated temperature effects at 300, 600, and 800 °C and then subjected to air- and water-cooling regimes. The ultrasonic pulse velocity, flexural strength, compressive strength, and mass loss of the SGCs with the inclusion of FBP were determined. In addition, scanning electron microscopy (SEM) analyses were carried out for control (without FBP) and 20% FBP-based SGC cooled in air and water after elevated temperatures of 300 °C and 600 °C. The results show that the compressive and flexural strength of the SGC samples are higher than the control samples when the FBP replacement ratio is used of up to 30% for the samples after the elevated temperatures of 300 °C and 600 °C. The lowest compressive and flexural strength results were obtained for the control samples after a temperature of 800 °C. As a result, the elevated temperature resistance can be significantly improved if FBP is used in SGC by up to 30%.

Combined effect of using steel fibers and demolition waste aggregates on the performance of fly ash/slag based geopolymer concrete

Developing sustainable construction products has been showing a rising trend recently. Geopolymer composites are remarkable binding materials fabricated based on recycling and sustainability. In this paper, an experimental investigation was conducted to study some mechanical and durability characteristics of steel fiber-reinforced fly ash/slag-based geopolymer concrete (GPC) with different proportions of recycled coarse aggregate. Steel fiber-reinforced geopolymer concrete mixtures incorporating recycled coarse aggregates of up to 40% at the interval of 10% were prepared, and the mixtures without recycled coarse aggregate were used as reference samples. The steel fiber ratio of 0.3% and 0.6% were used and the combined effect of steel fiber and recycled coarse aggregate on the geopolymer composites’ behavior regarding strength properties, sulfate resistance, elevated temperature resistance, abrasion resistance, and freezing-thawing resistance was addressed. A significant improvement in strength properties was observed in steel fiber reinforced recycled aggregate geopolymer concrete with increasing fiber content; however, the strength properties of geopolymer concrete were decreased with the increase of recycled coarse aggregate amount. Also, the properties such as abrasion resistance, resistance to elevated temperature, sulfate resistance, and freeze-thaw resistance were improved with the addition of steel fiber. It indicates that the synergetic effect of steel fiber and recycled aggregate helps to produce ecologically sound geopolymer concrete with good engineering properties and durability characteristics that will bring sustainability to the concrete sector. Generally, the results show that the recycled coarse aggregate ratio of up to 30% and 0.6% of steel fiber can be considered an ideal combination to make geopolymer concrete with better overall properties.

Pull‐out capacity prediction of sustainable cementitious composites with artificial intelligence and statistical methods

AbstractConcrete is used with reinforcement in structures so adherence gains importance especially in fire scenarios. To contribute production of sustainable concrete, by‐products like granulated blast furnace slag, fly ash, and silica fume were used, generally. In this study, to determine the elevated temperature resistance of by‐product‐added composites, samples were exposed to 250, 500, and 750°C and bonding behavior of composites was determined with pull‐out test. Moreover, prediction models were developed to estimate concrete‐reinforcement adherence values without experimentation and importantly before a fire. For the prediction models, considering the cross correlation, the mixture type, temperature, compressive strength, and flexural strength of concretes were selected as independent variables different from literature and pull‐out capacity (POC) as dependent variable. Artificial neural network (ANN) and adaptive neuro‐fuzzy inference system (ANFIS) were used for prediction models. As a statistical method, multiple linear regression was used. The performances of pull out prediction models were compared according to coefficient of correlation (R), mean square error (MSE), and mean percentage error (MPE). Among the statistical models, Quadratic and pure quadratic performance surpassed the ANFIS model, which is a combination of ANN and fuzzy techniques. The best performance was obtained in ANN model with 99.85%, 3.65 kg, 3.1% for R, MSE and MPE, respectively. Therefore, ANN can provide a new applicable model to effectively predict POC of by‐product‐added cementituous composites under fire effect.

In-situ formed intergranular TiB2 into lightweight SiC(rGO) composite PDCs enable elevated temperature resistance for aerospace components

Strengthening interface bonding for superior mechanical/ablation performances of SiC-based aerospace vehicle components remains a major challenge. Attractively, polycarbosilane-vinyltriethoxysilane-graphene oxide with addition of TiN/B (PVG(TiN, B)) were successfully synthesized for the first time. An ingenious route via re-pyrolyzing ball-milling-induced SiC(rGO, TiB2)p fillers/PVG(TiN, B) precursors blends was introduced to prepare lightweight SiC(rGO, TiB2) composite polymer-derived ceramics (PDCs). Interestingly, both SiC(rGO, TiB2)p and PVG(TiN, B) pyrolysis products, composed of β-SiC/SiOxCy/Cfree(rGO, TiB2), are tightly coupled by each other owing to plentiful Si-dangling bonds. In-situ formed intergranular TiB2/B4C, well compatible with amorphous ceramic network, can prevent β-SiC grain growth, strengthen interface bonding, and even hinder further crack propagation along the grain boundaries. Particularly, samples re-pyrolyzed at 1300 °C possess unique combination of good hardness (5.44 GPa), excellent fracture toughness (4.70 MPa·m1/2), high flexural strength (41.90 MPa) and outstanding compressive strength (126.33 MPa). Improved high-temperature and ablation resistance gives them distinct advantages of interlocked microstructure under exposure of butane flame. As demonstrated, SiC(rGO, TiB2) composite PDCs were developed into porous ceramics with good thermal insulation, focusing on manufacturing large-size bulk PDCs for thermal protection system of hypersonic vehicles.

Effect of waste COVID-19 face masks on self-compacting high-strength mortars exposed to elevated temperature

During the pandemic, it becomes customary to wear a disposable surgical(face) mask (SM) to guard against coronavirus illness 19 (COVID-19). However, because existing disposal procedures (i.e., incineration and reclamation) emit hazardous substances, vast generations of contaminated surgical masks pose an environmental risk. Therefore, many studies are currently being carried out worldwide to dispose of SM. The easiest and cheapest of these methods is the disposal of SMs in cement-based composites. This study cut waste SMs to macro size and used them in cement-based composites such as polypropylene fiber. The elevated temperature resistance of cement-based composites decreases as their compressive strength rises. Low-melting materials like polypropylene fiber are utilized to improve the high-temperature resistance of cement-based composites. Therefore, SM with a low melting temperature was used in the design of the mixtures. SM was added to the mix at rates of 0.3, 0.5, 0.8, and 1 by weight of cement. As the SM ratio increased, the workability of the mixtures decreased. Water absorption and apparent porosity increased as SM reduced the workability of composites. The mixes' 28-day compressive strength ranges from 36.6 to 79.4 MPa. It was observed that flexural strength raised in some mixtures when SM was used. In the mixes using 0.5 % SM, about 40 MPa compressive strength was obtained after 800 °C. Additionally, SEM images showed that SM changed into microfibre during mixing. As a result, it has been determined that SM can be used at low rates to increase the elevated temperature resistance of cement-based composites.

Properties of fly ash-based lightweight-geopolymer mortars containing perlite aggregates: Mechanical, microstructure, and thermal conductivity coefficient

It is known that studies on lightweight geopolymer using fly ash need more research. Therefore, in this study, class F fly ash-based lightweight geopolymer mortar samples were produced by using river sand, raw perlite, and expanded perlite as aggregates. The study was planned in two groups. In the first group, river sand, raw perlite, and expanded perlite were used as aggregates. In the second group, raw perlite and expanded perlite were used as aggregates. Expanded perlite replacement rates in both groups were determined as 0%, 20%, 40%, 60%, 80%, and 100%. The produced geopolymer mortar samples were cured at 75 °C for 24 and 48 h. After heat curing, unit weight, ultrasonic pulse velocity, water absorption, porosity, thermal conductivity coefficient, and flexural and compressive strength tests were performed on the samples. In addition, the elevated temperature resistance of the geopolymer mortar samples was tested at 300 °C, 600 °C, and 900 °C temperatures. Moreover, the microstructures of geopolymer mortar samples before and after elevated temperature were examined using a field emission scanning electron microscope. According to the results obtained, with the use of raw and expanded perlite, unit weight, UPV, flexural and compressive strengths of geopolymer mortar samples decreased, while water absorption and porosity increased. Using raw and expanded perlite resulted in an increase in the thermal insulation performance of the geopolymer mortar samples. Furthermore, the use of expanded perlite in geopolymer mortar samples increased the strength of geopolymer mortar samples exposed to elevated temperatures of 900 °C.

Development and performance of sustainable structural lightweight concrete containing waste clay bricks

Utilization of waste crushed bricks (WCB), which are obtained from brick factories and demolition waste as coarse and fine aggregate for preparing concrete, is an adequate strategy to reuse them and save natural resources to achieve environmental sustainability. This study investigates the possibility of developing eco-friendly structural lightweight concrete (SLWC) with a 100% replacement of WCB. Different contents (5%, 10%, and 15%) of supplementary cementitious materials such as silica fume, fly ash, metakaolin, and slag as a replacement by weight of cement were investigated. The slump test, dry density, and mechanical properties (compressive, splitting tensile, and flexural strengths), as well as elevated temperature resistance and water absorption, were evaluated. Microstructure tests, including thermogravimetric analysis, X-ray diffraction and scanning electron microscopy (SEM), were performed. The performance of the developed concrete under high temperature exposure of 200 °C, 400 °C, and 600 °C was evaluated. The experimental results indicated that SLWC can be obtained using WCB as a 100% replacement of aggregate and by using 15% metakaolin and 15% silica fume as alternatives to cement, with a 39.5 and 41.5 MPa compressive strength, respectively. Incorporation of 15% slag as cement replacement exhibited the best performance after 600 °C exposure compared to other fine materials. The SEM images showed an improvement in transition zone characteristics and increased bond between coarse aggregate and cement paste.

Evaluation of structural performances of metakaolin based geopolymer concrete

Last few decades, there has been a substantial advancement of geopolymer (GP) as a Portland cement substitute. It is vital to investigate potential building uses for geopolymer concrete (GPC). Six different mixes were cast for an alkaline to binder (A/B) ratio of 0.25–0.50 with an interval of 0.05. Metakaolin-based geopolymer were cured at ambient temperature and tested for 7, 14, 28, and 90 days. Metakaolin-Marble (MM00) mix was observed to have a maximum slump. For an A/B ratio of 0.35, maximum compressive, split tensile, flexural strength and modulus of elasticity was achieved. For elevated temperature resistance, geopolymer concrete cubes were exposed to temperatures (T) of 200, 400, to 600 C. As the temperature increased, compressive strength (CS) reduced. As the increase of the alkaline to binder (A/B) ratio, the strength of geopolymer concrete increases up to a specific limit beyond the limit strength decline. An empirical formula for split tensile (STS) value prediction using compressive strength values is proposed, valid for determining split tensile strength value. The correlation between compressive strength, split tensile strength, flexural strength, and bulk density varies linearly for a quadratic polynomial.

Properties of ultra-high performance geopolymer concrete incorporating recycled waste glass

One of the advantages of geopolymer technology is the ability to recycle a variety of wastes. In this paper, waste glass was incorporated into ultra-high performance geopolymer concrete (UHPGC). Recycled waste glass replaced fine sand in various ratios in UHPGC. Several mixtures were prepared by replacing natural sand with 0 %, 7.5 %, 15 %, and 22.5 % of waste glass (WG). The prepared samples were submerged in 2 % H2SO4 and 5 % MgSO4 solutions. Furthermore, the samples were subjected to high temperatures (200–800 °C) for 1.5 h. The effect of the WG on UHPGC’s flowability, strength, durability properties, and elevated temperature resistance was examined. The experimental results demonstrate that the flowability of the mixture was increased by glass content. Compressive strength was reduced from 126 MPa to 121 MPa for the substituted 22.5 % natural sand by WG at ambient curing. After 120 days of exposure, the strength loss of the control mix and samples containing 22.5 % WG submerged in MgSO4 solution was found to be 5.3 % and 1.16 %, respectively. While submerged in H2SO4, the control mix and samples with 22.5 % WG lost 7.7 % and 1.83 % of their strength, respectively. Additionally, mixtures incorporating WG showed better thermal stability as compared to the control mixtures after high temperature exposure. Finally, after being heated, microscopic studies showed that mixtures with WG had less microcracks and a better transition zone between the geopolymer paste and the fine aggregate.