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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. [ABSTRACT FROM AUTHOR]

Solid waste recycling is an economically sound strategy for preserving the environment, safeguarding natural resources, and diminishing the reliance on raw material consumption. Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials. This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-highperformance geopolymer concrete (UHPGC). In total, 18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder, ranging from 10% to 40%. Similarly, for each of the mixtures above, steel fibre was added at a dosage of 1.5% to address the inherent brittleness of UHPGC. The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders. The specimens were subjected to drop-weight impact testing, wherein an examination was carried out to evaluate various parameters, including flowability, density at fresh and hardened state, compressive strength, impact numbers indicative of cracking and failure occurrences, ductility index, and analysis of failure modes. Additionally, the variations in the impact test outcomes were analyzed using the Weibull distribution, and the findings corresponding to survival probability were offered. Furthermore, the microstructure of UHPGC was scrutinized through scanning electron microscopy. Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume, with reductions ranging from 18.63% to 34.31%. Similarly, failure impact number values decreased from 8.26% to 28.46% across glass powder contents. The maximum compressive and impact strength was recorded in UHPGC, comprising 10% silica fume with fibres. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete (FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force (up to 18%) while PP micro-fibres slightly increased the peak (3%-4%). FRUHPC significantly reduced the maximum midheight displacement by up to 30% (under 20° impact) and substantially improved the displacement recovery by up to 100% (under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance. [ABSTRACT FROM AUTHOR]

Solid waste recycling is an economically sound strategy for preserving the environment, safeguarding natural resources, and diminishing the reliance on raw material consumption. Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials. This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-high-performance geopolymer concrete (UHPGC). In total, 18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder, ranging from 10% to 40%. Similarly, for each of the mixtures above, steel fibre was added at a dosage of 1.5% to address the inherent brittleness of UHPGC. The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders. The specimens were subjected to drop-weight impact testing, wherein an examination was carried out to evaluate various parameters, including flowability, density at fresh and hardened state, compressive strength, impact numbers indicative of cracking and failure occurrences, ductility index, and analysis of failure modes. Additionally, the variations in the impact test outcomes were analyzed using the Weibull distribution, and the findings corresponding to survival probability were offered. Furthermore, the microstructure of UHPGC was scrutinized through scanning electron microscopy. Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume, with reductions ranging from 18.63% to 34.31%. Similarly, failure impact number values decreased from 8.26% to 28.46% across glass powder contents. The maximum compressive and impact strength was recorded in UHPGC, comprising 10% silica fume with fibres.

Polypropylene (PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete (FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force (up to 18%) while PP micro-fibres slightly increased the peak (3%–4%). FRUHPC significantly reduced the maximum mid-height displacement by up to 30% (under 20° impact) and substantially improved the displacement recovery by up to 100% (under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance.

The aim of this research was to develop cost-effective and environmentally friendly ultra-high-performance concrete (UHPC) using fly ash (FA) and quartz powder (QP) as sustainable cement replacements. The performance of the various constituents was examined and their influence on fresh and hardened properties was investigated in order to determine the optimum trial mix design. A cube compressive strength of 144 MPa was achieved with 20% FA and 10% QP and other ingredients without any special heat treatment. Advanced characterisation studies, such as the heat of hydration and X-ray diffraction analysis, were performed to gain understanding of the performance of FA-blended UHPC. Various fracture properties (fracture toughness, fracture energy, brittleness etc.) were investigated considering geometrically similar notched beam specimens for UHPC mixes with steel fibre contents of 1.5% and 2.5%. The optimum UHPC mix achieved good scores in terms of the strength index and the embodied carbon dioxide emissions index, indicating that the concrete is eco-friendly and sustainable. [ABSTRACT FROM AUTHOR]

Concrete filled steel tube columns (CFSTCs) are commonly used in large-span bridges and high-rise buildings. As the shrinkage of concrete may lead to significant degradation in the mechanical performance of CFSTCs, expansive concrete or fibre reinforced concrete is usually employed to improve the mechanical performance of CFSTCs. This study presents an experimental study on the combined effects of expansive agents and steel fibres on the axial compressive behaviour of circular CFSTCs. 13 CFSTCs were designed and manufactured using concrete mixes with varying expansive agent rates and steel fibre contents. The time-dependent expansive behaviours of the specimens were monitored during the concrete curing period. Then, the 13 specimens were tested under axial compression load. The failure modes, compression load-axial strain relationship, hoop strain and axial strain relationship, and ductility were investigated. The results demonstrated that the combined addition of expansive agents and steel fibres would substantially improve the compressive strength and ductile behaviour of CFSTCs.

The effectiveness of steel fibres in improving mortar is closely related to their length and dosage To investigate the effect of different lengths and dosages of steel fibres on the performance of mortar, four lengths of steel fibres, namely 6 mm, 13 mm, 25 mm, and 30 mm, were selected, and each length of fibre was single-mixed and multi-mixed following the volumetric rates of 0.5%, 1%, 1.5%, and 2%. The frost resistance of the steel fibre mortar was also analysed by freeze-thaw cycles regarding the compressive strength and flexural strength loss rate. The results showed that the compressive strength of the specimens was significantly improved as the four lengths of fibres were mixed in equal proportions of 1%. The flexural strength was most obviously increased when the four lengths of fibres were mixed in equal proportions of 1.5%, and the compression-flexural ratio was the smallest. At this time, the mortar had the best comprehensive performance. It was also found that the mixing the different lengths of steel fibres at a dosage of 1%∼1.5% in equal proportions resulted in a more uniform distribution of fibres. It improved the mortar better than the single mixing. After the 100 freeze-thaw cycle tests, the loss rate of the steel fibre mortar specimen was significantly lower than the ordinary mortar specimen. Mixing different lengths of steel fibres can improve the mechanical properties and frost resistance of the mortar more effectively.

This article proposes an optimisation approach for improving the performance of hybrid fibre-reinforced concrete (HFRC) in compression with varying fibre content. The proposed approach uses the Atomic Orbital Search (AOS) control scheme. The major objective of the proposed method is to raise the compressive strength, tensile strength and flexural strength of sisal fibre. The AOS approach is used to predict the stress–strain issues and provides an optimal solution. The Hybrid fibres combine multiple fibre types, which significantly improves ductility and energy absorption while the capability is compared to single-type fibre additions. By then, the proposed model is implemented in MATLAB/Simulink working stage and the execution is calculated with the proposed method. The compressive strength in HFRC is 47.6, split tensile strength in HFRC is 6.12, flexural strength in HFRC is 8.81, water absorption in HFRC is 0.67 and the mass loss in HFRC is 97.3. From the result, it concludes that the performance of hybrid fibre-reinforced concrete is improved. [ABSTRACT FROM AUTHOR]

Based on the orthogonal experiments, using carbon fiber, steel fiber, and nano carbon black as admixtures, the resistivity and compressive strength of specimens at each mix ratio were measured, and the results were evaluated using the analytic hierarchy process and grey correlation method. The research results indicated that the resistivity increases with the increase of CF, SF, and NCB content. The compressive strength increases with the increase of CF and SF content, and decreases with the increase of NCB content. CF has the most significant impact on electrical resistivity and compressive strength. The percolation thresholds of conductive concrete in the experiment are at CF, SF, and NCB dosages of 0.6 v%, 0.3 v% and 0.6 w%, respectively. The comprehensive evaluation results showed that the conductive concrete has the best performance when the CF, SF, and NCB dosages are 0.9 v%, 0.7 v%, and 0.6 w%, respectively, with a compressive strength increase of 31.8% and a resistivity decrease of 98.9 % compared to the blank group. [ABSTRACT FROM AUTHOR]

Flexural strength is an important mechanical property of steel-fibre-reinforced concrete. By designing three-point bending tests of concrete with five specimen heights, three steel fibre types, and two steel fibre mixing methods, the effects of the specimen height, steel fibre mixing method, and steel fibre type on the peak load, effect of size, section characteristics, strain characteristics, and characteristics of the load–displacement curve of concrete specimens were studied. The results show that the peak load of the control group is basically linear with the height of the specimen. After adding three kinds of steel fibres, the peak load of the specimen is greater than that of the control group in the same case. The peak load of the specimen increases by adding three kinds of steel fibres, and the increase is closely related to the height of the specimen. The residual stage of the load–displacement curve of the milling steel fibre and the end hook steel fibre are relatively flat, while the residual stage of the load–displacement curve of the shear steel fibre is relatively large, and the residual load is also greater than the residual load of the shear steel fibre. The specimens in the control group show brittle failure characteristics. As the height of the specimens increases, the failed section of the specimens is smoother. The development of cracks in the steel fibre specimens is more tortuous than that of the control group, showing ductile failure characteristics. Some tensile failure zones are still present where the fibres are densely distributed, and the failure characteristics of the specimens are further explained and proven by the strain characteristics. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) is a new green building material with low pollution, low energy consumption and high strength; however, it has the disadvantage of being brittle and prone to cracking. Studies have shown that the incorporation of inorganic fibres in GPC can enhance the toughness of GPC and inhibit the development of cracks. There is no clear uniformity in the existing literature on the effect of inorganic fibres to enhance GPC. In this paper, the research reports on the effect of inorganic fibres on the mechanical properties of GPC in recent years, and the prospects of their future research are discussed.

In recent years, health monitoring consists of the periodic observation and analysis of existing systems to predict and avoid structural breakdown, thereby saving lives and significantly lowering the cost of structural maintenance and repair. Normally, non-destructive testing techniques and sensor technology are used to detect damage in concrete structures are expensive in nature. Self-diagnosing or smart concrete has emerged a new paradigm in concrete research for damage detection. Smart concrete was cast by blending functional fillers such as carbon black, and steel fibers with concrete to improve the performance. Under various load conditions, the mechanical properties of the proposed smart concrete were examined. The electrical resistance of smart concrete was measured using the Four Probe Method and the Arduino UNO software. SEM and XRD were used to investigate the microstructures of intrinsically smart concrete. Thermogravimetric analysis was employed as a Non-Destructive Testing method to observe the hydration process. Furthermore, the obtained data were linked with the electrical resistivity of the smart concrete to assess corrosion damage. The electrical resistivity method is also an economical method and effective method to monitor the rate of corrosion.

This paper discusses the experimental investigations of the design mix developed for developing ultra-high-strength mortar mixtures made with different combinations of fine aggregates, metallic and non-metallic fibres and cured at different temperatures. Copper slag, Iron ore tailings (IOT) and M-Sand (MS) were the materials used as partial replacements for river sand among them Copper slag and Iron ore tailings were used as in replacement levels of 30%, 40% and 50% whereas M-Sand was used in 30%, 40%, 50% and 100%. The use of other cementitious materials like silica fume and nano-silica were kept constant and were used in 8% and 2% respectively as partial replacement of cement. Steel fibres were incorporated in constant levels of 1%. In addition to the waste utilization use of non-metallic fibres has also been incorporated in hybrid form in present research. Basalt fibre and poly propylene (PP) were used in this regard in 1% and 0.15% respectively. A total of 22 mixes were designed with 10 mixes having a constant 1% steel fibre addition and fine aggregates altered in varying proportions. The balance 12 mixes were made with different fibres for replacement in fine aggregate made only using M-Sand. The compressive strength test on different curing regimes hot curing for 1 and 3 days and normal curing for 7, 28 and 56 days were performed. The results indicated that among the alternate materials chosen as fine aggregate, those with 30% IOT and 1% steel fibres registered a maximum compressive strength of 121.27 MPa after subjecting them to 56 days of normal curing. Mix with non-metallic fibre combination made with PP did not show much strength increase and the maximum strength noted was 93.59 MPa for 30% MS and 0.15% PP. Among the hybrid combination, mixes with 30% MS along with 1% steel and 1% basalt incorporated in exhibited the higher strength of 120.88 MPa. A predictive model was also designed to validate the experimental results developed with compressive strength as the target and Curing days, temperature, and fine aggregate proportions as inputs. The model worked well with the inputs. [ABSTRACT FROM AUTHOR]

The cracking resistance and durability of the ultra-high-performance concrete (UHPC) structure are directly affected by its tensile behaviour. A micro-analysis method was established to study the tensile behaviour of the UHPC before the appearance of visible cracks. The cooperative characteristic of the steel fibre and the cement matrix was taken as a research focus of the micro-analysis method. The random distribution of steel fibre was considered as normal distribution. Based on the micro-analysis method, the tensile behaviour of UHPC was divided into the elastic stage and micro-damage development stage. Other data sourced elsewhere were used to verify the feasibility of the micro-analysis method and the necessary data were tested using pure bending specimens to verify the theoretical model. The results show that the working mechanism of inner steel fibre can be described by the micro-analysis method. The bending test results of the UHPC at the elastic and the micro-damage development stage match the theoretical model. The tensile behaviour of the UHPC is dominated by the inner steel fibre and the contribution of the cement matrix can be ignored. A bilinear model is proposed to describe the tensile constitutive of UHPC before the appearance of visible cracks, and the limitations of each stage are 8.85 MPa and 12.36 MPa.

In this paper, a formula is proposed to calculate the nominal axial strength (Po) of fibrous reactive powder concrete (RPC) columns reinforced with steel fibres of different geometries and volume contents. The formula takes into account the effects of concrete, longitudinal reinforcement, transverse constraints, geometry of steel fibres and their volume content. A comparison is made with existing formulations that consider only for concrete and steel reinforcement. The proposed formula has been verified and validated by the experimental results of different types of steel fibre reinforced concrete (SFRC) columns in the literature. The results show that the current formulation considering only concrete and reinforcement significantly underestimatesPo of fibrous RPC columns. Furthermore, it is found that the proposed formula well predicts the nominal axial strength for fibrous RPC columns with an accuracy of 97–99%.

A new type of construction combined with fibre materials for prefabricated shear wall structures is proposed to improve the seismic performance of conventional regenerated brick concrete shear walls. Four fibre-reinforced recycled brick concrete precast shear walls (PFRBCSWs) composed of restraint boundary elements (RBE) and the corresponding monolithic specimen were constructed and tested under an in-plane reversed cyclic loading. The experimental results indicate that: (1) Compared with the monolithic specimen, the difference in the bearing capacity of PFRBCSWs is within 20%, and the energy consumption capacity at each stage is slightly higher. (2) Fibres could significantly improve the initial stiffness and energy dissipation capacity of PFRBCSWs, and effectively restrain the crack development. (3) The hybrid fibre-reinforced wall structure (S-PFPW) achieves the highest initial stiffness and energy dissipation capacity, but has poor ductility and bearing capacity. Numerical simulation of the tests were conducted, and parameter studies were carried out for the aspect ratio and axial compression ratio of PFRBCSWs, as well as the reinforcement ratio of the RBE. The shear resisting mechanisms of PFRBCSWs are analysed based on the softened strut-and-tie mode. The predicting formula for bearing capacity is proposed, and it fits well with the experimental results. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of hardening accelerator and steel fibre on concrete adhesion strength for the repair of rigid highway and airfield pavements. The concretes were mixed based on CEM II/A-S 42.5 and included MasterGlenium SKY 608 superplasticiser. Experiments with two variable concrete composition factors were carried out. The amount of steel fibre varied from 0 to 100 kg/m3 and the amount of SikaRapid hardening accelerator varied from 0 to 9.6 kg/m3. It was found that modified repair concretes have a sufficiently high adhesion strength to 'old' concrete, from 2.30 MPa when tested by the pull-off method and from 2.05 MPa when tested by the flexural strength test method. Fibre-reinforcement increases the adhesion strength of repaired concrete by 7–15% due to the reduction of shrinkage during hardening. Treating the contact surface of 'old' concrete with a primer additionally increases adhesion strength by 6–10%. The maximum adhesion strength of fibre-reinforced concrete to the base reaches 3 MPa. Due to the high early and design strength, modified steel fibre-reinforced concrete provides the possibility of quick resumption of traffic while ensuring the integrity of the road structure due to the joint work of the repair material with the old concrete repair area. [ABSTRACT FROM AUTHOR]

Concrete protective structures are mainly meant to withstand impact loads. However, fire events weaken concrete and reduce its impact resistance. This study investigated the impact behaviour of steel-fibre-reinforced alkali-activated slag (AAS) concrete before and after exposure to elevated temperatures (i.e., 200 °C, 400 °C, and 600 °C). Hydration products' stability under elevated temperatures, their effects on the fibre–matrix bond, and, consequently, AAS's static and dynamic responses were investigated. The results reveal that adopting the performance-based design concept to achieve a balance between AAS mixtures' performance under ambient and elevated temperatures is a crucial designing aspect. Advancing hydration products' formation will increase the fibre–matrix bond at ambient temperature while negatively affecting it at elevated temperatures. High amounts of formed and, eventually, decomposed hydration products at elevated temperatures reduced the residual strength due to lowering the fibre–matrix bond and developing internal micro-cracks. Steel fibre's role in reinforcing the hydrostatic core formed during impact loads and delaying crack initiation was emphasized. These findings highlight the need to integrate material and structure design to achieve optimum performance and that low-grade materials can be desired based on the targeted performance. A set of empirical equations for the correlation between steel fibre content in the AAS mixture and corresponding impact performance before and after fire exposure was provided and verified. [ABSTRACT FROM AUTHOR]

Fibre-reinforced cementitious composites are highly effective for construction due to their enhanced mechanical properties. The selection of fibre material for this reinforcement is always challenging as it is mainly dominated by the properties required at the construction site. Materials like steel and plastic fibres have been rigorously used for their good mechanical properties. Academic researchers have comprehensively discussed the impact and challenges of fibre reinforcement to obtain optimal properties of resultant concrete. However, most of this research concludes its analysis without considering the collective influence of key fibre parameters such as its shape, type, length, and percentage. There is still a need for a model that can consider these key parameters as input, provide the properties of reinforced concrete as output, and facilitate the user to analyse the optimal fibre addition per the construction requirement. Thus, the current work proposes a Khan Khalel model that can predict the desirable compressive and flexural strengths for any given values of key fibre parameters. The accuracy of the numerical model in this study, the flexural strength of SFRC, had the lowest and most significant errors, and the MSE was between 0.121% and 0.926%. Statistical tools are used to develop and validate the model with numerical results. The proposed model is easy to use but predicts compressive and flexural strengths with errors under 6% and 15%, respectively. This error primarily represents the assumption made for the input of fibre material during model development. It is based on the material's elastic modulus and hence neglects the plastic behaviour of the fibre. A possible modification in the model for considering the plastic behaviour of the fibre will be considered as future work. [ABSTRACT FROM AUTHOR]

Coal gangue is the waste created in the coal mining process and can be utilised as a coarse aggregate in construction projects to solve the environmental problems it causes. To study the mechanical properties of steel fibre reinforced coal gangue concrete (SFCGC) columns under eccentric compression, two natural aggregate concrete (NAC) columns and eight SFCGC columns were designed and fabricated for eccentric compression loading tests. The variables involved in the tests include gangue substitution rate (0%, 30%, 50%, 70%), steel fibre volume content (SFVC) (0%, 0.5%, 1%, 1.5%), and eccentricity (0.25, 0.5). The experimental work and theoretical analysis were used to investigate the failure mode, cracking, and ultimate bearing capacity of SFCGC columns. The effects of various variation parameters on the longitudinal strain, concrete strain, transverse displacement, crack width, and bearing capacity were analysed in detail. The digital image correlation (DIC) technique was used to compare with the conventional observation and to analyse the cracking trend of the specimens. The testing results revealed that the damage pattern of SFCGC columns under eccentric compression was similar to that of NAC columns. The eccentricity significantly affected the damage pattern (or bearing capacity) of SFCGC columns. The effect of the coal gangue replacement rate on the lateral displacement corresponding to the ultimate load can be neglected under the same eccentricity. The incorporation of steel fibres effectively inhibited the development of cracks in the columns, with an average increase in crack load and ultimate load of 7.36% and 17.1%. The equations were also established to determine the crack width and bearing capacity of the studied SFCGC columns, and the theoretical predictions agreed with the experimental results. [ABSTRACT FROM AUTHOR]

This study investigated the mechanical properties of alkali-activated slag cementitious material (AASCM) after exposure to 20–800 ℃ considering the effect of steel fibre content and aggregate type to promote the use of AASCM in structural engineering. The volume contents of steel fibre were 0%, 0.5%, 1.0% and 1.5%, and the aggregate types were manufactured sand and natural river sand. The residual compressive, tensile strength and mass loss were determined. Besides, the microstructure and phase composition of AASCM before and after high temperature exposure were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the tensile and compressive properties of manufactured sand AASCM were inferior to that of natural river sand after high temperature exposure. Below 600 ℃, steel fibre can improve the mechanical properties of AASCM. Steel fibre oxidation fails and effectively loses its strengthening effect on AASCM with the temperature reaching 800 ℃, resulting in a notable decrease in strength of AASCM. The models for calculating mass loss, compressive strength, and tensile strength of steel fibre reinforced AASCM after high temperature exposure were established.

This work presents the mechanical characteristics of concrete enhanced with egg shell powder (ESP) and nano-silica (NS) along with steel fibres. Steel fibre reinforced concrete (SFRC) offers several benefits, including prevention of macro cracks, improving ductility and residual strength and increasing toughness. These benefits make SFRC a valuable choice for structural applications requiring enhanced durability, crack resistance, and resilience to mechanical stresses. To develop the modified concrete mixture the Ordinary Portland Cement (OPC 53 grade) was partially replaced with varying percentage such as 0%, 5%, 10%, and 15% of ESP and NS by weight of the total binder content. Steel fibers were merged into the concrete at a volume fraction of 1.5% by weight of concrete to boost the engineering characteristics of concrete. The effect of ESP and NS were observed on compressive, flexural and split tensiles trength of the concrete. The test was conducted after 7 and 28days of curing period. The inclusion of 10% and 15% percentage of ESP and NS gives high mechanical properties. The findings validated the suitability and efficacy of employing ESP and NS as partial substitutes for OPC, leading to substantial enhancements in the engineering characteristics of SFRC.

The use of scrap tyres in construction materials has been promoted to curb the environmental exploitation caused by the open disposal of non-biodegradable waste rubber. Tyre grinds as aggregates in geopolymer concrete (GPC) would increase its sustainability value by reducing the consumption of natural aggregates. Although there is limited literature addressing the damage to GPC characteristics caused by rubber aggregates, this investigation was designed to determine the extent of possible side effects of using crumb rubber (CR) in GPC. Additionally, this investigation aims to address any resulting reduction in strength and durability using additives such as cement and fibres. Geopolymer specimens with CR replacement of fine aggregates by volume (0, 5, 10 and 15%) showed a compressive strength reduction of up to 17% when tested according to ASTM standards. Substituting the total binder by weight with Ordinary Portland cement (OPC) (0%, 5%, 10%, 15%, and 20%) improved the microstructural integrity of the rubberised geopolymer mix with the highest percentage of OPC. Despite producing new and additional binding products (CSH and CASH gels), the GPC surface readily disintegrated under acid exposure. Optimum glass fibres (GF) reinforcement (0.30%) effectively disrupted the GPC pore network, consequently reducing the acid permeability of the matrix. Further addition of steel fibres (SF) enhanced the GPC specimen's compressive and flexural strength. To analyse the cumulative effect of these additives on GPC microstructure, supporting tests such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were carried out. Although these additives enhanced the overall performance of rubberised geopolymer, it might somewhat reduce its green aspect.

Transverse shear reinforcement is usually used to resist the induced shear stresses in conventional concrete beams. Ultra-high performance concrete (UHPC) with fibres has high strength, post-peak strength, and strain softening. Such features can impact the behavior of the beam under loading. This paper presents the results of experimental tests performed on simply supported UHPC T-beams with basalt or steel fibres, with or without stirrups, subjected to four-point bending loads. The volume fraction of basalt fibres, the shear span, and the presence of stirrups are adopted as parameters. The possibility of achieving equivalent performance by using basalt or steel fibres, as shear micro-reinforcement, instead of using traditional steel stirrups is discussed from viewpoint of the beam structural behavior due to shear stress. The results show that the shear resistance increases with increasing fibre content and decreases with increasing shear span. The addition of basalt or steel fibres alters the fracture from brittle to ductile. Also, it is possible to partially replace the stirrups by using 1.0 % or more steel fibres or 0.5-1.0 % basalt fibres in the UHPC matrix. However, it is preferable to use a considerable ratio of shear rebars to avoid the dominance of shear failure. [ABSTRACT FROM AUTHOR]

The vibrations produced by earthquakes cause large horizontal forces in beam-column joints. If these forces exceed the limit values that the joints can withstand, severe irreparable damage might occur. Experimental and analytical studies were conducted to determine the energy dissipation capacity and ductility of beam-column joints by using the Self-Compacting Concrete (SCC) and Normal Concrete (NC) mixes containing various quantities of steel fibres. Test results were compared with the results obtained using the test specimen made of normal concrete. The test results reveal similar behaviour of normal concrete and self-compacting concrete with regard to energy dissipation capacity. The use of steel fibres is known to increase ductility. This study shows that this behaviour is more prominent in the case of 1 % fibre volume ratio.