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Copper slag (CS) is produced during the smelting process to separate copper from copper ore. The object of the experimental research is to find the optimum percentage of CS and PPF volume fraction when CS replaces fine aggregate, and PPF volume fraction when subjected to impact loading. Copper slag was incorporated as 20%, 40%, 60%, 80% and 100% with PPF of 0.2-0.8% with 0.2% increment. The number of blows on failure of the specimen increases as the fibre volume increases. In addition, the energy absorption of composite concrete is higher than that of ordinary concrete. Concrete with up to 40% CS and 0.6% PPF volume shows a 111.72% increase in the number of blows for failure as compared to the control specimen. The impact resistance at failure was predicted by regression analysis, and very high regression coefficients of 0.93, 0.98 and 0.98 were obtained respectively at 7-, 14- and 28-days curing. In addition to regression analysis, a two-parameter Weibull distribution analysis was used to obtain reliable data on the number of blows at first cracking and eventual failure. The energy absorption at 28-day curing period is 1485.81 Nm which is 284% higher than the control mix. Based on the findings, it can be inferred that adding CS up to 60% densifies the microstructure due to its pozzolanic activity, while polypropylene fibre acts as a micro reinforcement, increasing the number of blows.

This research examined the performance of functionally graded two-stage fibrous concrete (FTSFC) against modified repeated falling-mass impacts. This study led to the concept of creating improved multiphysics model of fibre composites with better impact resistance for potential protective constructions. FTSFC was developed based on the bio-inspiring strength of turtle shells. The excellent impact resistance of FTSFC was accomplished by including a larger quantity of steel and polypropylene fibres in the outer layers. At the same time, one- and two-layered concrete were cast and compared to evaluate the efficiency of three-layered FTSFC. To minimize the dispersed test results, a modified form of the 544 drop-mass impact test was recommended by the American Concrete Institute (ACI). The modification was a knife-edge notched specimen instead of a solid cylindrical specimen without a notch. This modification predefined a crack path and reduced the dispersion of results. Cracking and failure impact numbers, ductility index, and failure mode were the testing criteria. The suggested modification to the ACI impact test decreased the coefficient of variance, showing that the dispersion of test results was reduced significantly. This study led to the concept of creating improved, fibre composites with better impact resistance for potential protective constructions.

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

Preplaced Aggregate Fibrous Concrete (PAFC) is a newly minted composite that has recently become more popular. The production of PAFC involves two essential processes; first, the fibres and coarse aggregate were filled into the empty framework to form the first layer of a natural skeleton, followed by grout injecting. A cement grout fills the voids in the first layer skeleton with slight compaction. This process is repeated to complete the remaining layers; hence, a type of Functionally-graded Preplaced Aggregate Fibrous Concrete (FPAFC) is obtained. The most recent studies revealed that the literature regarding the high-velocity projectile impact on fibrous concrete is well documented; however, the low-velocity repeated projectile impact on PAFC is still unexplored and needs particular emphasis. This research aims to investigate the FPAFC made with a new type of steel and polypropylene fibres against low-velocity projectile impact to fill this research gap. In the current study, twelve mixes were prepared with mono and hybrid combinations of fibres for pioneering the possible utilization of fibres in FPAFC. The maximum fibre dosage in this study is limited to 2.4%. The projectile impact resistance of FPAFC was assessed in line with penetration depth, front and rear damage surface area, weight loss, damage ratio and failure pattern. Additionally, a simplified analytical model was introduced to compute the ejected composite mass from the tested specimens. The results revealed that the addition of steel fibre in a single layer FPAFC exhibited an increasing compressive strength trend compared to the two/three-layered FPAFC. Furthermore, increasing the dosage of fibre at the bottom and top layers of FPAFC with a hybrid combination alleviates the spalling with an increasing number of impacts. The results from this research offer the reference information for more detailed research and studies of FPAFC under low-velocity projectile impact.

This study investigates the fracture properties of high performance cementitious composites (HPCC) with four different types of fibres and with volume fraction content 3%. The four fibres are steel hooked end (S), polypropylene crimped (PP), basalt chopped (B), and glass (G) fibres. The tests were carried out in accordance with the RILEM recommendations. In order to examine the fresh properties of HPCC the slump flow tests were performed. Twelve fibre reinforced HPCC beam specimens with notch were cast and tested using central point loading experiments. In addition, experimental tests of the compressive strength and splitting tensile strength were carried out. The test results made it possible to obtain representative fracture parameters, such as the equivalent strengths, residual strengths, and fracture energy of fibre reinforced HPCC. The S fibre specimens showed the best performance in terms of workability, compressive strength, tensile splitting strength, and fracture energy at large deflection. On the other hand, G fibre specimens exhibited the best performance in terms of flexural strength, equivalent flexural strength at higher deflection, and residual flexural strength at lower deflection. In terms of equivalent flexural strength at lower deflection and residual flexural strength at higher deflection, basalt fibre specimens performed the best. On the contrary, polypropylene fibre reinforced beam specimens revealed the highest deflection capacity.

A comprehensive program of experiments consisting of compression, uniaxial compression, direct shear, flexural as well as splitting tensile and air permeability tests were performed to analyse the effect of the level of fibre dosage and the water-cement ratio on the physical properties of hybrid fibre-reinforced concrete (HFRC). Two types of fibres were studied in terms of their effect on the properties of HFRC. The results indicated that the mechanical properties of concrete were significantly improved by increasing the fibre content. However, increasing the percentage fibre content past a certain peak performance limit (0.9% glass fibre (GF) and 0.45% polypropylene fibre (PPF)) led to a decrease in strength compared to reference mixes. Additionally, the incorporation of hybrid fibres yielded an increase in air permeability in the tested specimens. The results showed that the strength-related properties of HFRC were superior to the properties of single fibre-reinforced concrete.

This paper aims to investigate the effect of the polypropylene fibre (PP) and basalt fibre (BF), singly or in hybridization, on the workability, mechanical, chloride resistance and pore structure characteristics of concrete. Sixteen mixtures consisting of PP and BF, both at volume content of 0.0, 0.1, 0.2 and 0.3%, were fabricated, and the slump, compressive, splitting tensile, flexural and charge passed were tested. The results show the hybridization of the PP and BF can improve three types of strength of concrete in comparison to their single fibre. Nevertheless, the hybridization is not always conducive, and the synergy of fibres is proposed and divided into positive and negative effects. The combination of the PP and BF both at content of 0.1% achieves the best mechanical performance, and is recommended for practical usage. Incorporating fibres reduces the chloride resistance of concrete, and the hybridization is helpless to this phenomenon; even the reduction is intensified at a highly hybrid fibre volume. However, increasing the curing age can mitigate this adverse effect caused by fibres. Furthermore, the microstructures were explored to elucidate the macro-properties of concrete in terms of interface and pore structure.

This study has investigated the changes that might appear in post-peak flexural response. Before the flexural test, prismatic specimens were placed in a furnace chamber and exposed to elevated temperatures of 400, 600, and 800 °C. The flexural toughness test was carried out on two types of concrete: Plain ultra-high performance concrete (UHPC) and UHPC with different types of fibres (steel fibre (SF) and polypropylene fibre (PPF)) at 0.5%, 1%, 1.5%, and 2% volume fractions. During the flexural test in the macro-crack development analysis, the non-contact ARAMIS system was used to perform three-dimensional measurements of strain and displacement. The results of scanning electron microscope (SEM) observations of micro-crack development in UHPC without and with SF/PPF were also presented. The experimental results showed that in some cases, the load-deflection curve of fibre-reinforced UHPC displayed a double-peak response. The first peak signified the UHPC properties, while the second peak represented the properties of the fibres. Under flexural load, the toughness decreased as the temperature increased. Significant decrease in the load-deflection response and toughness were observed for the polypropylene fibre-reinforced UHPC when the temperature approached 800 °C. The SEM observation results showed that the thermal damage of fibre-reinforced UHPC depends on the pore pressure effect, the thermal mismatch, the decomposition of hydration products, and the formation of micro-cracks.