Split Tensile Research Articles

Experimental study on flexural fatigue resistance of fiber-reinforced sustainable walnut shell ash mortar

In recent research on building materials, researchers have increasingly focused on replacing cement with agricultural waste. This approach offers significant advantages in terms of reducing global CO2 emissions and promoting the sustainability of building materials. In this paper, the use of the agricultural waste walnut shell ash (WSA) to partially replace cement in sustainable green mortars is explored. Specifically, equal amounts of WSA (5%, 10% and 15%) were used to replace cement. To offset the reduction in strength caused by the partial replacement of cement with WSA, basalt fibers were added to the mortar mixture. The effect of these fibers on the mechanical properties of the WSA-reinforced mortar was examined in compression tests, split tensile tests, and flexural fatigue cycle tests. In the flexural fatigue tests, the parameter and length of basalt fibers were varied and different stress levels (0.85, 0.8 and 0.75) were applied. The fatigue equations were developed using the Weibull model and p–s–n curves with a survival probability of 0.5 were derived. The results showed that the compressive strength and split tensile strength of the specimens increased with the addition of basalt fibers, with maximum values of 34.7 MPa and 3.8 MPa, respectively, and maximum increases of 8.78% and 21.95%, respectively. In addition, the average fatigue life of WSA mortar was 247,541 cycles, which increased by 139.26% when the stress level was 0.75, fiber length was 9 mm, and dosage was 0.3%. The linear regression fitting showed good correlation and provided valuable insights for practical engineering applications.

Fresh, hardened properties and microstructural analysis on the effect of NaOH molarities of industrial by-products based self-compacting geopolymer concrete

AbstractThe sodium hydroxide (NaOH) molarity in Self-compacting geopolymer concrete (SCGC) is essential for activating the precursor and aggregate to develop strength, workability, and microstructure. In this study, SCGC mixes prepared with 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBS) to investigate fresh and hardened properties with NaOH molarities (M) ranges from 8 to 16, the ratio of Na2SiO3 to NaOH kept constant at 2.5 and ratio of alkaline solution to the binder at 0.45 with 2% SP for the polymerization process. SCGC workability studies indicate the NaOH concentration increased, the slump flow decreased, and 14 M was the optimum molarity. The compressive, split tensile, and flexural strength results showed 39.4 MPa, 4.72 MPa, and 5.91 MPa at 28 days. The C–S–H gel enhanced the strength qualities studied from Fourier transform infrared spectroscopy. The scanning electron microscope showed microstructural densification of the entire system, which improved with the NaOH concentration, and the strength increased with the degree of polymerization and polycondensation. Hence, based on workability, the optimized NaOH concentration is 14 M with binder contents of FA (50%) and GGBS (50%). This study helps to improve the microstructure and strength properties with potential cost implications of SCGC.

Experimental studies on strength and workability of mineral admixture modified cement-based fibre-reinforced self-compacting concrete

ABSTRACT Mineral admixtures such as fly ash (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK), and silica fumes (SF) derived from industries are often referred to as secondary cementitious materials, as partial replacements for cement. Also, the use of fibres significantly enhances the flexural behaviour of concrete. Various kinds of literature highlight the performance of concrete with one or two types of admixtures. In this study, an attempt is made to explore the effect of the use of more than two admixtures viz. FA, GGBS and MK as a partial replacement to cement and fibrofor fibre (FF) on workability and strength properties of based Fibre-Reinforced Self-Compacting Concrete (FRSCC). The FF in Self-Compacting Concrete (SCC) is varied from 1.0 to 2.0 kg/cum. The SCC samples are tested for three curing durations. Based on the experimental investigations, the workability of all the mixes is found to be within the EFNARC limits. The variation in the compressive strength of SCC for various fibre dosages is within 10%, after 28 days of the curing period. It is noted that A-10 mix with fibre dosage of 1.0 Kg/cum yielded the highest compressive, split tensile, and flexural strengths after 56 days of curing, as compared to that of all other variations including conventional SCC mix.

Development of a novel DNA-shaped steel fiber and its performance on fresh and hardened concrete

Adding small discrete random fibers in concrete has enhanced concrete behavior in various ways. Diverse types of fibers are available in terms of materials, shapes, and applications. Different shapes of steel fibers are available like hooked ends, crimped, stranded, helix, spherical, etc. Having the grade of concrete and the fiber dosage added as constant, the structural behavior and performance will vary for different types of fibers. It shows that the shape of fiber has a great role in enhancing the properties of concrete. The challenges in existing two-dimensional steel fibers in concrete like the mechanism and contribution of fiber in arresting cracks developed in all directions and balling effect can be overcome by a new type of three-dimensional steel fiber. A novel three-dimensional DNA-shaped steel fiber is designed and fabricated. This paper presents the fresh concrete and hardened concrete properties of DNA-shaped fiber-reinforced concrete (DNAFRC) and compares it with hooked-end fiber-reinforced concrete (HEFRC) by incorporating a volume fraction varying from 0.5 to 2% of grade M30 concrete and aspect ratio of 60 for both fibers. The fresh properties of concrete were evaluated by measuring the slump for workability and wash-out test for the fiber distribution. The hardened concrete properties were assessed by compressive, split tensile, flexural, impact, shear, and pull-out strength which demonstrated considerable increase by 5% at 1.5% volume fraction, 32%, 136%, 21%, and 35% at 2% volume fraction respectively for DNAFRC than the HEFRC. Scanning Electronic Microscope (SEM) images were studied on failed samples to evaluate the bonding of DNA fiber with concrete.

Investigating the Sway of Marine Brown Seaweed Gel as Natural Polymer in Properties of Concrete

In the present study, the effects of the fresh properties as slump, consistency and setting time and hardened concrete's characteristics such as compressive, split tensile and flexural strength for various ages, the brown seaweed (Sargassum wightii) gel was added to cement throughout differing proportions (1, 2, 3, 4 and 5%) by the mass of concrete. Durability and thermal tests such as water absorption, sorptivity, RCPT, acid attack and thermal conductivity also determined at various ages. Micro structural properties of seaweed gel were found out by SEM, FTIR and XRD analysis. Test results show that seaweed gel act as retarding admixture in cement up to 5% of addition. For instance, 5% alginate collections as a percentage of concrete mass showed a comparable compressive strength of about 42MPa. The use of seaweed gel improved the thermal characteristics of concrete by reducing its thermal conductivity roughly 50% for a 5% addition. The seaweed gels up to 5% addition in concrete will significantly improve the fresh-state properties of concrete without affecting its hardened properties. The future is completely dependent on eco-friendly materials; hence the use of natural organic additives to improve the strength and durability of cement concrete would be the better option for sustainability.

Investigating the performance and durability of high mechanical milling nano pulverised refused SCMs

This study investigated the performance and durability of high-mechanical-milling nano-pulverized industrial reject supplementary cementitious materials (SCMs). The research utilized industrial reject (IR-1), specifically Ground Blast Furnace Slag (GBFS), as the SCM. As-received IR-1 GBFS was milled for 90 minutes to achieve nano-sized particles, and its properties were compared with the un-milled, or before-milled (BM) material. Three pozzolanicity tests were conducted to compare the before milled (BM) and after-milled (AM) materials. Additionally, M30 grade concrete mixes were developed with cement partially replaced by 30 %, 35 %, and 40 % using both BM and AM IR-1 materials. Mechanical performance, including compressive strength, flexural strength, and split tensile strength, along with durability tests such as water absorption, sorptivity, and rapid chloride penetration, were conducted for the BM and AM IR-1 blended concretes. The results showed that AM IR-1 blended concrete achieved the required design strength at a 30 % cement replacement level. Furthermore, the AM IR-1 blended concrete exhibited 40 % higher compressive strength, 39 % higher flexural strength, and 29 % higher split tensile strength compared to the control concrete. Durability testing also revealed significant improvements in AM IR-1 blended concrete, with reductions of 19.65 % in water absorption, 24.71 % in sorptivity, and 38 % in chloride penetration. This study demonstrates that industrial waste, such as GBFS, can be effectively utilized as a sustainable alternative to traditional materials in the construction industry. Additionally, nano-pulverization treatment significantly enhances the pozzolanicity and overall performance of materials that may not meet the physicochemical standards specified in IS 3812-(Part 1):2017 and ASTM C618–19.

Incorporation of Nanoalumina in Potassium Feldspar-based Phosphoric Acid Activated Geopolymer Composites: A Sustainable Approach

This study investigates the potential of potassium feldspar-phosphate-based geopolymer concrete as a sustainable replacement to traditional concrete, addressing the environmental concerns associated with CO2 emissions during cement production. While geopolymer concrete offers a promising path towards sustainability, its performance often falls short of Portland cement concrete. This study investigates the use of nanoalumina in improving the performance of geopolymer concrete. A ternary mix was formulated with potassium feldspar powder, metakaolin and rice husk ash, incorporating varying percentages of nanoalumina geopolymer concrete mixes. The mechanical characteristics of the resulting geopolymer composites were assessed through compressive and split tensile strength tests. The findings revealed that a 4% nanoalumina dosage (GC-N4) yielded the most significant improvement in strength and durability. The GC-N4 mix performed superior in all metrics, demonstrating the highest compressive (41.82 MPa) and split tensile (3.7 Mpa) strengths. Reduction in water absorption and durability aspects were also optimum in GC-N4. These results highlight the potential of incorporating nanoalumina into a ternary mix of potassium feldspar powder, metakaolin and rice husk ash to significantly enhance the overall performance of geopolymer concrete, promoting its wider adoption as a sustainable construction material.

Experimental study on pore structures and mechanical properties of ferroaluminate cement under sulfate attack

Ferroaluminate cement (FAC) emerges as a special cement with outstanding durability, offering promising applications. However, the resistance to sulfate attack of FAC remains inadequately understood. In this paper, the impact of sulfate attack on the pore structure of FAC concrete is explored through nuclear magnetic resonance (NMR) tests from a microscopic perspective. Meanwhile, the macroscopic mechanical characteristics of concrete attacked by sulfate are investigated under different loading conditions, including splitting tensile and conventional triaxial compression. NMR test analysis shows that as the degree of erosion increases, the number of mesopores and macropores in FAC concrete decreases while the number of micropores increases. The changes in pore structure distribution alter the mechanical response of specimens. The discussion of strength characteristics, deformation behavior, and energy parameters in conventional triaxial tests reveals that FAC concrete attacked by sulfate exhibits superior mechanical properties under confining pressure. Uniaxial strength results indicate that sulfate attack has less impact on specimens under tensile stress state than under compression. Based on the experimental findings, this paper introduces a sulfate attack impact factor to capture the uniaxial strength changes. Further, a multiaxial strength criterion is developed to describe the strength properties of sulfate-attacked concrete under triaxial stress conditions.

Comparative Study of Mechanical Properties of Self Compacting Concrete Using Binary Pozzolanic Materials

Abstract: The study examined the viability of using waste supplementary cementing materials (SCMs), such as fly ash (FA) and silica fume (SF), as partial replacement of Ordinary Portland cement. The way SCC's fresh properties and hardened were impacted by FA and SF. The study examined the fresh characteristics and hardened characteristics of various distinct SCC mixes using SCC with partial replacement of Ordinary Portland Cement with FA (class F) and SF. First, the cement was replaced by percentages in the mixes 0%, 10%, 15%, 20%, 25%, and 30% by FA and constant replacement of 10% by SF. Then cement was replaced by percentages in the mix with 25% FA constant and 4%, 6%, 8%, 10%, and 12% by SF. For every combination, the water/binder (w/b) ratio was set at 0.43. The EFNARC (Specification and Guidelines for Self-Compacting Concrete) standards were met by the slump flow, T50, and viscosity of the SCC. After 28 days of curing, the blend consisting of 65% PC, 25% FA, and 10% SF had a maximum compressive strength of 41.22 MPa which is 12.07% greater than the compressive strength of the control specimen which is 36.78 MPa. The Split Tensile Strength of the same blend is 4.37% is greater than the control specimen. Non-destructive tests were also performed after 28 days of curing and the regression equations give the excellent relationship between Rebound Number, Ultrasonic Pulse Velocity, and Compressive Strength. This is due to the formation of the proper matrix as the particle size of SF and FA is less than that of cement and the free lime of cement reacts with FA and SF to form C-S-H gel which provides strength.

Workability, mechanical, durability, and microstructural investigation of sustainable concrete utilizing secondary treated wastewater, fly ash, and sodium nitrite

ABSTRACT This study explored the use of secondary treated wastewater (STW) from three secondary-level wastewater treatment plants, along with fly ash (FA) and sodium nitrite (SN), to produce sustainable concrete, comparing it to concrete made with tap water. Key properties examined included workability (slump cone), strength (compressive, split tensile, and flexural), and durability (rapid chloride permeability and efflorescence). Scanning electron microscopy (SEM) analysis was performed to investigate the concrete's microstructure. The results indicated that FA and SN content had a notable influence on the workability, mechanical strength, and durability of the concrete mixtures. However, the type of water (STW or tap water) used in the concrete preparation showed no significant impact. Durability tests revealed that the penetrability of the mixtures ranged from low to moderate, signifying good quality, and no efflorescence was observed. Ultimately, the study concluded that concrete made with STW, when supplemented with 10% FA and 2% SN, demonstrated comparable performance to that made with tap water across key properties, offering a viable option for sustainable concrete production.

Triaxial creep test and damage model study of layered red sandstone under freeze-thaw cycles

To examine the creep behavior and degradation of stratified rock in cold areas, triaxial creep experiments and microscopic analyses were performed on layered red sandstone specimens under freeze-thaw (F-T) cycles. This study revealed the deterioration characteristics and damage mechanisms of red sandstone's creep behavior under the influence of F-T cycles and bedding inclination. The test results showed that: (1) The steady-state creep rates with bedding angles β=30°after 0, 40, 80, and 120F-T cycles were 0.0168 × 10−2·h−1, 0.0224 × 10−2·h−1, 0.0289 × 10−2·h−1, and 0.0368 × 10−2·h−1 respectively. The instantaneous deformation, creep deformation, and steady-state creep rates increased gradually with the increase of F-T cycles, while the long-term strength exhibited a decreasing trend. (2) After 40F-T cycles, the long-term strengths with bedding angles of 0°, 30°, 45°, 60° and 90° were 121.17 MPa, 65.47 MPa, 46.28 MPa, 77.64 MPa and 124.78 MPa, respectively. The bedding angle of 45° has the greatest influence on the triaxial creep properties of red sandstone, followed by the bedding angles of 30° and 60°, and the bedding angles of 0° and 90° have the least influence. (3) As the F-T cycles increases, the longitudinal wave velocity gradually decreases, and the pores and cracks on the sample surface continue to expand, leading to increased damage. The failure mode evolves from a single oblique shear plane to an “X”-shaped tensile splitting. Additionally, the bedding angle has a significant effect on the longitudinal wave velocity. As the bedding angle increases, the longitudinal wave velocity exhibits a “V”-shaped distribution, initially decreasing and then increasing. Based on the test results, a creep damage model of layered rock considering the influence of F-T cycles was established, and the rationality of the model was verified by test data. The research results can provide a scientific basis and technical reference for the long-term stability of layered rock engineering in cold regions.

Investigation of self-compacting concrete utilizing different supplementary pozzolanic materials for cement replacement

This study enhances self-compacting concrete (SCC) properties by adjusting the mix design, reducing the water-to-cement ratio, and adding permeability-reducing admixtures (GGBS, fly ash, silica fume, bentonite). Different admixture proportions were tested to improve mechanical characteristics. Four SCC mixtures were formulated, varying GGBS and fly ash (0-70%) and silica fume and bentonite (0-20%). Auromix 300 plus (0.6% by weight of cement) was used as a chemical admixture. Strength properties (compressive, flexural, split tensile, elastic modulus) were evaluated on specimens cured normally for 28 days, then in NaCl for 56-112 days. Optimal mixtures were found: GGBS 30% for compressive strength, bentonite 10% for flexural and split tensile strength. Results indicate increased strength and reduced porosity by incorporating these materials.

Mechanical and physical characteristics of concrete mixed with sugarcane bagasse ash and recycled polyethylene terephthalate

The goal of this study was to produce sustainable concrete by reducing reliance on cement, which contributes to high carbon footprints, and natural sand, which is being depleted. Sugarcane bagasse ash (SCBA) was used to partially replace cement at 5 %, 10 %, and 15 %, while recycled polyethylene terephthalate (RPET) was used to partially replace sand at 5 %, 10 %, 15 %, and 20 %. The effects of these substitutions on concrete's mechanical and physical properties were examined after 28 days of water curing. The study observed a decrease in fresh density by 0.36 %–2.67 % with SCBA and RPET inclusion. The slump values ranged between 93 mm and 140 mm, indicating good workability. The reference concrete's compressive strength was 39.65 MPa, while the mix with 5 % SCBA and 10 % RPET achieved 38.23 MPa. This mix also showed a 1.2 % higher split tensile strength than the reference concrete. Although the reference concrete's flexural strength was the highest at 4.56 MPa, all SCBA-RPET mixes remained within 86 % of this value. All modified mixes weighed less than the reference concrete, with the compressive strength-to-weight ratio of the mix with 5 % SCBA and 10 % RPET being closest to the reference mix with only a 2.44 % reduction. These findings suggest that SCBA and RPET can be effectively used to produce sustainable concrete with comparable mechanical properties to conventional concrete.

Experimental Study on Concrete Strength Behavior Using Plastic Waste as a Partial Replacement of Fine Aggregate

Waste from plastic materials is outstripped due to the growth of industrialization and urbanization. Plastic materials are non-biodegradable; decomposition is not possible all the time. The recycling of plastic materials by using them in concrete will be a great deal for plastic management. This research investigation aims to measure the optimum percentage of plastic in concrete without a reduction in concrete strength and shear behavior of reinforced concrete. Using the provision of Mix Design ACI 211.1-91, the M28 concrete grade was created. Plastic materials have been collected and passed through a No-4 sieve (4.76mm). The combination of fine aggregates and ground plastic materials (RPET, PP) in the weight fraction of fine aggregate mix (0%, 2%, 4%, 6%, 8%, 10%) was used in the concrete. Concrete beams (750´150´150 mm) are reinforced with two 12 mm longitudinal steel bars in the tension zone, with proper clear cover for testing the shear capacity. In order to conduct the compressive and tensile splitting test, concrete specimens with a diameter of 100 mm and a height of 200 mm were used. The experimental findings demonstrate guidelines for using plastic as a partial replacement within 2% to 4% of fine aggregate to produce the best outcomes.

Experimental study on effective utilization of industrial solid wastes in developing Ultra-High Performance Geopolymer Concrete

<p><a><span style="font-size:12.0pt"><span style="line-height:115%"><span style="font-family:"Times New Roman",serif">This experimental study explores the use of Ground Granulated Blast Furnace Slag(GGBS) and dolomite as alkali activated binders and copper slag as aggregate to achieve a cost-effective and sustainable Ultra-High-Performance Geopolymer Concrete(UHPGC). Several concrete compositions utilizing copper slag as a substitute for natural aggregates were formulated. Tests have shown that the inclusion of 100% copper slag fine aggregate leads to significant improvements in the mechanical properties and density of geopolymer concrete. Specifically, the compressive strength increased by 56.8% and the density increased by 17.5%. To understand the influence of dolomite in GGBS binder, several mixes varying dolomite proportion in GGBS were examined. The compressive strength of the 80% GGBS/20% dolomite geopolymer matrix is 32.8% higher compared to the compressive strength of UHPGC with 100% GGBS. The UHPGC mixture containing 1% crimped steel fibers showed the highest compressive strength, measuring 146.6 MPa. The split tensile and flexural strengths of the 20% dolomite matrix show a significant increase of 30.55% and 30.24% respectively compared to the 100% GGBS matrix. The water absorption and porosity of the 100% GGBS specimen were found to be lower compared to the 20% dolomite UHPGC specimen. The microscopic study reveals the positive impact of dolomite and GGBS on enhancing the bonding of the geopolymer matrix along with decreasing permeability. This study highlights the potential of geopolymer technology in producing ultra-high-performance concrete using GGBS, dolomite, and copper slag.</span></span></span></a></p>

Experimental Investigations on Tensile and Shear Behavior of the Interface Between UHP-ECC and Concrete

Ultra-high performance engineered cementitious composite (UHP-ECC), which is known for its exceptional compressive strength, tensile strength, and ductility, has been emerged as a promising option for repairing and strengthening reinforced concrete (RC) structures. The bond between UHP-ECC and normal concrete is the key issue for the material to be successfully implemented. This paper presents an experimental investigation focused on understanding the tensile and shear behavior of the bonding interface between UHP-ECC and concrete. A total of 78 specimens were prepared and tensile splitting tests and push-out tests were carried out. The study examined key parameters including the strength of the concrete substrate, the roughness of the interface, and the moisture condition at the interface. Various failure modes are observed in the specimens under tensile splitting force and direct shear force, and it is found that the influence of the key parameters varied depending on the type of failure mode. In specimens experiencing full interface debonding or interface failure combined with substrate cracks, the roughness of the interface and the moisture degree have a significant impact on the tensile and shear strength. Conversely, in specimens with full substrate disruption, the strength of the substrates plays a more significant role. Additionally, the study reveals that the grooving treatment is highly effective in improving the shear strength of the interface, but its impact on enhancing the tensile strength is comparatively less pronounced. Prediction models for the tensile and shear strength of the interface are established and verified against the test results. The proposed models provide valuable insights into the behavior of the UHP-ECC to concrete interface and can aid in predicting its performance in practical applications.

A Comparative Study for the Mesoscale Models of Concrete

Abstract This paper provides an overview of mesoscale models used to simulate concrete behavior. A comparative analysis was carried out using mesoscale models with two dimensions. The impact of material type on three tests: the indirect tensile splitting test, the three-point bending test, and the direct tensile test was examined in the study. Additionally, a comparison is made between the findings obtained with and without the application of ITZ and the analysis results obtained from the direct tensile test. The results showed that the fixed crack model had higher stiffness than isotropic damage model in both direct tensile test, and three-point bending test. In indirect tensile splitting test, only fixed crack model gave meaningful results. The models with ITZ had most of the cracks in ITZ rather than in the mortar.

Development of Ultra-High-Performance Concrete Using GGBS and Alccofine

Abstract: Ultra-high-performance concrete, or UHPC, is a cementitious mixture that is distinguished by its exceptionally high compressive strength—more than 120 MPa as well as its remarkable toughness, tensile ductility, and longevity. Ground Granulated Blast Furnace Slag (GGBS) and Alccofine (AF) are commonly used in the matrix composition to increase the particle system's packing density and subsequently enhance the matrix's strength in order to guarantee that UHPC has the proper strength. To investigate the engineering properties of ternary blended UHPC with GGBS, AF, a comparative study was conducted. In comparison to the control UHPC mix, the ternary blended UHPC mix's mechanical and durability qualities were improved by the percentage variation of AF within specific bounds. In this study, the experimental work included mix proportioning and preparation of ternary blended UHPC specimens and various tests like Compressive Strength, Split Tensile Strength, Flexure Strength and RCPT (Rapid Chloride Penetration Test) were performed in the laboratory. The results show that under normal water curing conditions, the strength qualities of UHPC based on GGBS are considerable, up to a cement replacement level of 40%. In addition, compared to the binary counterpart, the mixture of 20 Percent AF and 40 Percent GGBS showed better mechanical and durability properties.

Comparison of Coren mix design with other international mix (ACI and DoE) design methods

Because of its quality, which allows for veracities, Today, concrete is the most frequently utilized civil engineering material. Concrete has a low tensile strength and a high compressive strength. Even though Nigeria is Africa's giant, it has been discovered that its local contractor does not have a well-used standard mix procedure. Local Nigerian contractors have relied on an international mix. COREN recently established a mix design. It is critical that we determine whether this design process will be suitable for usage by local contractors. To assess the effectiveness of the published local mix against defined international standards, a complete experimental analysis of the COREN mix design with ACI and DoE was used in this study. With a target compressive strength of 30N/mm2, three concrete mix designs with 0.48 and 0.50 water/cement ratios were used, and this mix was subjected to compressive tests, split tensile tests, and three-point bending. With respect to all the test conducted and analyzed, this attests to the level of significance of COREN i.e. For 28days mix with 0.48w/c, compressive strength with COREN gave 32N/mm2 against 31N/mm2 and 30N/mm2 for ACI and DoE mix, respectively. Splitting tensile strength of 2.7 N/mm2 was achieved with COREN mix against 2.8N/mm2 and 2.7N/mm2 from ACI and DoE, respectively. Likewise, results of flexural strength are 4.7N/mm2, 5.3N/mm2 and 5.1N/mm2 for COREN, ACI and DoE, respectively. For 28days mix with 0.50w/c, compressive strength with COREN gave 29N/mm2 against 30N/mm2 for ACI and DoE mix, respectively. Splitting tensile strength of 2.5N/mm2 was achieved with COREN mix against 2.4N/mm2 and 2.8N/mm2 from ACI and DoE, respectively. Likewise, results of flexural strength are 5.1N/mm2, 4.7N/mm2 and 5.6N/mm2 for COREN, ACI and DoE, respectively.

Flexural behaviour of geopolymer concrete beams with hybrid natural–synthetic fibre reinforcement

The requirement of excellent flexural stiffness in construction elements has initiated the use of fibre reinforcement. However, the processing complexity involved in the manufacture of synthetic fibres is environmentally hazardous. The use of natural fibres in geopolymer concrete (GPC) structures was investigated in this work using a hybridisation of natural and synthetic fibre. Natural basalt fibre (BF) was used with synthetic steel fibre (SF) in various proportions in GPC and tests were conducted to evaluate the workability, compressive strength, split tensile strength and flexural strength. It was found that, compared with the plain GPC, the addition of 1.5% BF and 0.5% SF resulted in 45%, 27% and 12% improvements in compressive, split tensile and flexural strengths, respectively. The compatibility between the SF and BF resulted in enhanced post-peak flexural behaviour, with 37% improvements in the modulus of elasticity and stiffness. As BF possesses more tensile strength than SF, the use of 1.5% BF and 0.5% SF provided better flexural and ductility properties than the use of SF alone, which could lead to the development of ductile GPC members under dynamic loading conditions.