Experimental investigation on mechanical and durability characteristics of metakaolin-based fibre reinforced concrete

Supplementary cementitious materials (SCM) have turned out to be a vital portion of extraordinary strength and performance concrete. Metakaolin (MK) is one of SCM material is acquired by calcinations of kaolinite. Universally utilised as pozzolanic material in concrete to enhance mechanical and durability properties. This study investigates the fresh and hardened properties of conventional concrete (CC) and self compacting concrete (SCC) by partially replacing cement with MK in diverse percentages. In CC and SCC, partial replacement of cement with MK varies from 5-20%. Fresh concrete properties of CC are conducted by slump test and compaction factor tests and for SCC, slump flow, T500, J-Ring, L-Box, V-Funnel and U-Box tests. Hardened concrete characteristics are investigated by compressive, split tensile and flexural strengths at age of 7, 28 and 90 days of curing under water. Carbonation depth, water absorption and density of MK based CC and SCC was also computed. Fresh concrete test results indicated that increase in MK replacement increases workability of concrete in a constant w/b ratio. Also outcomes reveal that concrete integrating MK had greater compressive, flexural and split tensile strengths. Optimum replacement level of MK for cement was 10%, which increased mechanical properties and robustness properties of concrete.

Mechanical and environmental performance evaluation of meta-kaolin and silica fume-modified steel fiber embedded concrete: A sustainable construction

In this investigation, sustainable High Performance Lightweight Aggregate Concrete (HPLWAC) containing artificial aggregate as coarse lightweight aggregate (LWA) and reinforced with mono fiber, double and triple hybrid fibers in different types and aspect ratios were produced. High performance artificial lightweight aggregate concrete mix with compressive strength of 47 MPa, oven dry density of 1828 kg/m3 at 28 days was prepared. The Fibers used included, macro hooked steel fiber with aspect ratio of 60 (type S1), macro crimped plastic fiber (P) with aspect ratio of 63, micro steel fiber with aspect ratio of 65 (type S), and micro polypropylene fiber (PP) with aspect ratio of 667. Four HPLWAC mixes were prepared including, one plain concrete mix (without fiber), one mono fiber reinforced concrete mixes (reinforced with plastic fiber with 0.75% volume fraction), one double hybrid fiber reinforced concrete mixes (0.5% plastic fiber + 0.25% steel fiber type S), and a mix with triple hybrid fiber (0.25% steel fiber type S1+ 0.25% polypropylene fiber + 0.25% steel fiber type S). Fresh (workability and fresh density) and hardened concrete properties (oven dry density, compressive strength, ultrasonic pulse velocity, splitting tensile strength, flexural strength, static modules of elasticity, thermal conductively, and water absorption) were studied. Generally, mono and hybrid (double and triple) fiber reinforced HPLWAC specimens give a significant increase in splitting tensile strength and flexural strength compared with plain HPLWAC specimens. The percentage increases in splitting tensile strength for specimens with mono plastic fiber are, 20.8%, 31.9%, 36.4% and 41%, while the percentage increases in flexure strength are 19.5%, 37%, 33.9% and 34.2% at 7, 28, 60, 90 days age respectively relative to the plain concrete. The maximum splitting tensile and flexure strengths were recorded for triple hybrid fiber reinforced HPLWAC specimens. The percentage increases in splitting tensile strength for triple hybrid fiber reinforced specimens are 19.5%, 37%, 33.9% and 34.2%, while the percentage increases in flexure strength are 50.5%, 62.4. %, 66.8% and 62.2% at 7, 28, 60 and 90 days age respectively relative to the plain concrete specimens.

The safe disposal of waste tires has been seen as having a negative impact on the environment. To mitigate this impact, the components of waste tires can be used in the production of green concrete. This study explores the effects of the curing and drying regime on the mechanical properties and permeation characteristics of concrete containing both crumbed rubber and steel fibers that are removed from waste tires. Five concrete mixes were designed, and concrete cubes, cylinders, and prisms were cast using waste tires extracts. Crumb rubber was treated by submersion in sodium hydroxide and then used to partially replace 10% and 30% of fine aggregates in the concrete mix. Extracted steel fibers were added at the rate of 1% and 2% per volume of each mix. Compressive and indirect splitting tensile as well as flexural strengths were conducted after normal curing while observing several drying conditions. Additionally, air permeability was assessed using a portable apparatus that was developed to assess permeability easily. For the concrete test specimens containing 10% partial replacement of fine aggregate by crumb rubber and 1% steel fibers, it was discovered that the splitting tensile strength and flexural strength were higher than that of the control mix by 21% and 22.6%, respectively. For specimens that included the 10% crumb rubber and 1% steel fibers, when exposed to oven drying at 105°C for 12 h, the compressive strength results increased by 17% compared with the control specimens exposed to the same conditions. Unlike the compressive strength results, the splitting tensile and flexural strength results decreased after exposing the specimens to elevated temperature. The addition of crumb rubber and steel fibers as a partial fine-aggregate replacement resulted in increasing the air permeability of the concrete to different degrees depending on the percentages used. The oven-drying curing regime improved the permeability by reducing it in specimens containing the 10% crumb rubber and 1% steel fibers as indicated by increasing their permeability time index by 15% when compared with air-dried specimens. Using waste tire extracts as a partial replacement of concrete fine aggregate can be recommended for both indoor and outdoor applications. This study showed that this was a viable, economic, and environmentally friendly method for reducing carbon footprint.

In this investigation, sustainable High Performance Lightweight Aggregate Concrete (HPLWAC) containing recycled crushed clay brick from construction and demolition waste as coarse lightweight aggregate (LWA) and reinforced with mono fiber, double and triple hybrid fibers in different types and aspect ratios were produced. High Performance crushed brick lightweight aggregate concrete mix with compressive strength of 41.2MPa, oven dry density of 1930 kg/m3 at 28 days were prepared. The Fibers used including, macro hooked steel fiber with aspect ratio 60 (type S1), macro crimped plastic fiber (P) with aspect ratio 63, micro steel fiber with aspect ratio 65 (type S), and micro polypropylene fiber (PP) with aspect ratio 667. Six HPLWAC mixes were prepared including, one plain concrete mix (without fiber), two mono fiber reinforced concrete mixes ( reinforced with either steel fiber type S or plastic fiber with 0.75% volume fraction), two double hybrid fiber reinforced concrete mixes (0.5% steel fiber type S +0.25% polypropylene fiber and 0.5% plastic fiber + 0.25% steel fiber type S), and one mix with triple hybrid fiber (0.25% steel fiber type S1+0.25% polypropylene fiber +0.25% steel fiber type S). Fresh (workability and fresh density) and hardened concrete properties (oven dry density, compressive strength, splitting tensile strength, flexural strength and absorption) were studied. In general mono and hybrid (double and triple) fiber reinforced HPLWAC specimens give significant increases in splitting tensile strength and flexural strength compared with plain HPLWAC specimens. The percentages increase in splitting tensile strength for specimens with mono steel fiber are 55.8%, 65.9%, 82% and 91.9%, while for specimens with mono plastic fiber the percentages increase are 34%, 45.5%, 61.5% and 71.2% at 7, 28, 60, 90 days age respectively relative to the plain concrete. The maximum splitting tensile and flexure strengths were recorded for triple hybrid fiber reinforced HPLWAC specimens. The percentages increase in splitting tensile strength for triple hybrid fiber reinforced specimens are 57.2%, 68.6%, 87.5% and 101.8%, while the percentages increase in flexure strength are 84%, 95.6%, 6665% and 7.67% at 7, 28, 60 and 90 days age respectively relative to the plain concrete specimens.

Traditional concrete, made from binding material, fine aggregate, coarse aggregate, and water, often suffers from low tensile strength and susceptibility to cracking. Microscopic cracks can develop before any significant load is applied, making the structure vulnerable to damage. Fiber reinforced concrete (FRC) tackles these issues by adding different types of fibers, like steel, glass, and polypropylene, to enhance strength and flexibility. This study aims to find the best mix for Steel Fiber Reinforced Concrete (SFRC) and Hybrid Fiber Reinforced Concrete (HFRC) of M25 grade. Compressive strength, split tensile strength, flexural strength, Young's modulus, and ultrasonic pulse velocity tests are conducted to see how well the fibers work to prevent cracks and boost strength. Results have showed that SFRC with 1.5% steel fiber content significantly improve compressive strength, split tensile strength, and flexural strength compared to normal concrete. Similarly, HFRC mix of steel, glass, and polypropylene fibers, performs well, showing a notable increase in split tensile and flexural strength. The percentage increase in strength highlights how effective fiber reinforcement can be, with HFRC showing better results in some aspects compared to SFRC. Furthermore, both SFRC and HFRC are stiffer than normal concrete, indicating better overall structural integrity. Our comparison suggests that incorporating a blend of fibers, as seen in HFRC, can provide even better results, particularly in enhancing split tensile and flexural strength, showing promise for future reinforced concrete applications.

This study investigates the fresh and hardened state performance of slag-based self-compacting alkali-activated concretes (SCAAC) reinforced with steel fibers (SF) and nano-silica (NS), cured at an ambient temperature. Two different hooked-end SF with two fiber volumes and NS were used to examine the combined effect of the SF volume ratio, SF aspect ratio, and NS on the fresh and hardened state performance of SCAAC. In extension, the influence of specimen thickness to steel fiber length (d/FL) ratio on the failure modes of the bending specimens was evaluated. The fresh state properties were evaluated via T50 value, slump flow, V-funnel, and L-Box tests, while the hardened state properties were studied through compressive strength, splitting tensile strength, modulus of elasticity, and flexural tensile strength tests. The relationship analyses were carried out among fresh and hardened state properties, and scanning electron microscopy (SEM) was also conducted to examine the microstructure. The results indicated that fresh state performance was favorably affected by NS inclusion but adversely influenced by SF content and aspect ratio. The hardened state performances enhanced with a higher amount of SF volume and an aspect ratio. Also, the NS improved the splitting tensile and flexural strength but decreased the compressive strength and elasticity modulus of the specimens. The d/FL ratio was found a significant parameter on failure modes, and the specimens having a d/FL ratio of 3.33 showed flexural cracks. In contrast, the specimens having a d/FL ratio of 1.25 exhibited inclined flexural-shear cracks, especially for 1% SF.

Properties of steel fibrous concrete containing mixed fibres in fresh and hardened state

Influence of M sand in self compacting concrete with addition of steel fiber

Sustainable lightweight concrete presents a promising solution for reducing environmental pollution caused by construction and demolition waste. This study focuses on developing high-strength lightweight concrete (HSLWC) using lightweight expanded clay aggregate (LECA) as coarse aggregate and fully replacing natural fine aggregate (NFA) with recycled fine aggregate (RFA). To enhance performance of the produced mixes, 15% silica fume and varying contents of micro steel fibers (0.5% and 1%) were incorporated. Seven concrete mixtures were prepared with a low water to cement (w/c) ratio of 0.25 and tested at 28 days to evaluate slump flow, compressive strength, splitting tensile strength, density, and water absorption. The results revealed that using 100% RFA reduced compressive strength from 54.5 MPa to 45.7 MPa and splitting tensile strength from 4.67 MPa to 4.03 MPa. However, the inclusion of 1% steel fibers compensated for this reduction, raising compressive strength to 55.1 MPa and splitting tensile strength to 5.89 MPa. Further enhancement was observed when silica fume was combined with steel fibers, resulting in a maximum compressive strength of 58.1 MPa and a splitting tensile strength of 6.11 MPa. These values exceeded those of the reference mix made with NFA. The combined use of silica fume and steel fibers led to the most effective improvement, producing sustainable HSLWC with superior mechanical performance, reduced water absorption, acceptable workability, and structural lightweight density

An experiment was done to study the effect of metakaolin (MK) used as mineral admixture and its impact on the mechanical properties of MK-mixed concrete (MKMC) with and without the use of hooked steel fibre (SF). The present investigation was performed on referral concrete of M30 grade mix concrete. MKMC was made using OPC alone as control cube and using MK in place of cement by 5, 10, 15 and 20%. The parameters of fresh properties of concrete such as slump of concrete and hardened properties of mixed concrete such as compressive strength (CS) at 7, 28 and 56 days, split tensile strength (STS) at 28 days and flexural strength (FS) at 28 days with partial replacement of cement by MK with and without the use of SF were studied. After optimizing, the effect of inclusion of SF was also studied for CS (7, 28 and 56 days), STS (28 days) and FS (28 days) in referral as well as the MKMC. SF is added to 0.0, 0.50, 0.75, 1.0 and 1.25% by volume. It was found that substitution of cement by MK and the inclusion of SF shows better performance than referral concrete.

Steel Fiber is found to be the most suitable for increasing strength of concrete mix. Using Steel Fiber would increase some cost but it gives return many times of its cost as a increasing of Compressive strength, Split Tensile Strength, Flexural Strength and as well as provide better stability against Earthquake as the need for greater importance as a drawn-out arrangement in the Indian concrete industry. In the present analysis, we have added steel fiber i.e. 0.5 % to 2.0 % of cement content in concrete mix for getting better test results. The focus of this research is to Increase strength of concrete mix in various manner for getting high heights in construction industry. This study examines the effect of using steel fiber with silica fume in High Strength Concrete Mix i.e. M 60. Total 270 concrete specimens were cast in this study. The specimens were prepared for the concrete mix of M 60 grade using w/c ratio 0.32. The effects on different properties of concrete with Steel Fiber added concrete mix were evaluated in this study. The specimens of concrete mixes were tested for compressive strength, flexural strength, split tensile strength and carbonation test. Test results of the samples show that the strength of concrete mix increases with the use of Steel Fiber added concrete mix as 0.5 % to 2 % of cement content in M 60 Design Concrete mix. It is also found that carbonation depth for Steel Fiber added concrete mix concrete mix is few more as compared to Normal OPC M60 Design concrete mix. The overall results of this study show that Steel Fiber added concrete performs well in various strength tests with some modification in the mix design.

There is a demand for innovative construction materials that offer enhanced mechanical characteristics while also being cost-effective and environmentally friendly. This paper examines the fresh properties and mechanical properties of geopolymerized self-compacting concrete (SCC) reinforced with steel fibers, containing 0–100% metakaolin (MK) by mass, as an eco-friendly substitute for Portland cement. SCC combinations included one or more waste cementitious materials (WCMs), such as metakaolin (MK), NaOH as an alkaline activity, and double-hook end steel fibers. For every NaOH geopolymer SCC blend, the mechanical characteristics (compressive strength, splitting tensile strength, flexural strength), as well as the new properties (lump flow, V-Funnel, L-box test), were read up. The findings indicate that combining metakaolin and steel fibers reduces the flowability of NaOH-based geopolymer SCC. On the other hand, incorporating MK and steel fibers enhances the compressive and flexural strength of NaOH-based geopolymer SCC with 25% metakaolin and 0.3% steel fiber. In contrast to the fiber-reinforced NaOH-based geopolymer SCC samples, which could transfer a sizable load even when the crack mouth opening deflection rose at flexural strength, the fiber-free SCC samples showed a brittle and abrupt fracture. The findings showed that the addition of NaOH as an alkaline activator, MK, and steel fiber had a negative impact on the fresh state properties; however, their combined use greatly enhanced the bond strength and flexural performance of the NaOH geopolymer SCC specimens. Doi: 10.28991/CEJ-2024-010-07-011 Full Text: PDF

The demand for sustainable concrete is a priority in the current era. The construction industry is actively working to mitigate the environmental impact of cement production in concrete by incorporating alternative and supplementary cementitious materials and reducing carbon emissions. Metakaolin (MK) and rice husk ash (RHA) have become popular in this context due to their pozzolanic properties. This study aims to predict the compressive strength (CS), split tensile strength (STS), and flexural strength (FS) of concrete incorporating MK and RHA with the addition of steel fibers. It examines the influence of several factors, including cement, MK, RHA, water, fine aggregate, coarse aggregate, steel fiber, superplasticizer usage, and concrete age. To achieve this, the study combined experimental work with existing data from the literature. Various machine learning (ML) models, including linear regression, support vector machines, Gaussian process regression, and artificial neural networks (ANN), were employed to analyze and assess the impact on strength characteristics including CS, STS, and FS. The dataset was divided into training and testing subsets, and statistical analyses were conducted to explain the relationships between the input parameters and CS. The ANN model demonstrated superior precision in predicting CS, STS, and FS compared to the other ML models. The findings suggest that the ANN model, utilizing the identified input parameters, can accurately estimate the CS, STS, and FS of concrete with MK, RHA, and steel fibers. The application of such technologies in the construction sector can enable the rapid and cost-effective assessment of material properties and the influence of various input parameters.

Effect of aspect ratio and volume fraction of steel fiber on the mechanical properties of SFRC