The purpose of this study is to investigate the effect of steel fiber content and type on the compressive and flexural ductility capacities of lightweight aggregate concrete (LWAC). Fiber-reinforced LWAC specimens were divided into four groups according to the type of fibers, such as conventional macrosteel fibers (SFs) with hooked ends, straight copper-coated microsteel fibers (CMSFs), crimping-shaped CMSFs, and hooked-end CMSFs. The fibervolume fractions (Vf) were 0.5, 1.0, and 1.5%. This study also modifies the ASTM C1018 method by using the initial crack point calculated from the elastic theorem to save a tedious and elaborated effort in determining the reference point at the load-deflection curve, particularly for beams with a strong hardening response. The test results revealed that the hooked-end CMSFs were better than SFs and crimping-shaped CMSFs with the same shape and length at decreasing the slope of the applied loads at descending branches of the compressive stress-strain and flexural load deflection curves for the LWAC. Compressive and flexural toughness indexes were derived as functions of the fiber reinforcing index based on the regression analysis of test data to assess the ductility improvement of LWAC with steel fibers.

This paper is aimed at investigating the effects of different fiber inclusion on the mechanical properties of ultra-high-performance concrete (UHPC) by adding mineral admixtures as cement replacement materials to reduce production costs and CO2 emissions of UHPC. Throughout this research, 21 mixture designs containing four cement substitution materials (silica fume, slag cement, limestone powder, and quartz powder) and three fibers (steel, synthetic macrofibers, and polypropylene) under wet and combined (autoclave, oven, and water) curing were developed. To investigate the mechanical properties in this research, a total of 336 specimens were cast to evaluate compressive strength, the modulus of rupture (MOR), and the toughness index. The findings revealed that at the combined curing, regarded as a new procedure, all levels of cement replacement recorded a compressive strength higher than 150 MPa (21.76 ksi). Furthermore, the mechanical properties of the mixture design containing microsilica and slag (up to 15%) were found to be higher than other cement substitutes. Also, it was shown that all levels of the fiber presented the MOR significantly close together, and samples made of synthetic macrofibers and steel fibers exhibited deflection-hardening behavior after cracking. The mixture design containing microsilica, slag, limestone powder, and quartzpowder, despite the significant replacement of cement (approximately 50%) by substitution materials, experienced a slight drop in strength. Therefore, the development of this mixture is optimal both economically and environmentally.

Interlocking concrete block pavement (ICBP) is one of the pavement types adopted worldwide. The influential parameter of ICBP is comparatively more, which includes the geometric parameters of the interlocking paver blocks such as the size, shape, thickness, strength, and laying pattern of the blocks, and the gradations of the jointing and bedding sand. Other than the wearing surface, the thickness and properties of the bedding sand, base, and subgrade also play a vital role in the deflection properties of ICBP. The objective of the present study is to analyze the influence of block thickness, base thickness, and granular layer thickness on the deflection behavior and stress distribution of ICBP. The block thicknesses used for this study are 80, 100, and 120 mm; the bedding sand thicknesses are 30, 50, and 70 mm; and the base thicknesses are 150, 300, and 450 mm. The experimental work is carried out using the laboratory plate load test to determine the deflection and stress distribution of ICBP. Numerical analysis is also employed to simulate laboratory testing. The study attempts to find the most influential factor and the optimized parametric value for attaining lower deflection using Design-Expert software. The test results conclude that the thicknesses of the block and granular layer play an imperative role among the considered parameters.

This paper presents the results of an experimental study on the comparative response of polypropylene (PP) fiber-incorporated reinforced concrete (RC) beams under fire conditions. Five fullscale RC beam specimens, made with different batch mixtures comprising normal plain concrete (NPC) and fiber-reinforced concrete (FRC), were tested to assess their spalling performance and structural behavior under fire conditions. The main variables in the experiments were the amount and length of PP fibers. Deflections, temperatures, and spalling in the beams were monitored during fire exposure. FRC beams’ flexural failure occurs after 151 minutes at heating temperatures beyond 850°C, when deflections exceed span/20. When the concrete contains PP fibers (that is, FRC beams), the gamut of fire-induced spalling in RC beams gets reduced, increasing the fire resistance from 147 to 171 minutes (approximately 17%). Furthermore, test results show that adding 2 to 3 kg/m3 of PP fibers effectively releases the pore pressure through tensile cracking and reduces the amount of spalling in the FRC beams.

The main focus of the current research is the development of high-performance fiber-reinforced cementitious composites with large amounts of coarse aggregates without risking deflection-hardening response, and the evaluation of the autogenous self-healing capability of these composites at different scales. The structural performance of cementitious composites exhibiting strain hardening should be known to be used in large-scale specimens. In addition to the studies carried out in small sizes, there is a need to examine the self-healing performances of large-scale specimens. Composite mixtures included different design parameters—namely Class F fly ash-to-portland cement ratio (FA/PC = 0.20, 0.70), aggregate-cementitious materials ratio (A/CM = 1.0, 2.0), addition/type of different fibers (for example, polyvinyl alcohol [P], nylon [N], and hooked-end steel [S] fibers), addition/type of nanomaterials (for example, nanosilica [NS] and nanoalumina [NA]) and inclusion of steel reinforcing bar in tested beams. Small-scale (80 x 75 x 400 mm [3.15 x 2.96 x 15.76 in.]) and large-scale beams (100 x 150 x 1000 mm [3.94 x 5.91 x 39.4 in.]) were produced and considered for performance comparison. Four-point bending tests were performed on different-scale beams loaded by considering different shear span-effective depth ratios (a/d) ranging between 0.67 and 2.00 and 0.67 and 2.96 for small- and large-scale beams, respectively. Autogenous self-healing evaluation was made using different-scale beam specimens subjected to 30-day further cyclic wetting-and-drying curing in terms of changes in microcrack characteristics and recovery in flexural parameters of preloaded beams. Experimental results showed that it is possible to successfully produce concrete with large amounts of coarse aggregates without jeopardizing the deflection-hardening response both at small and large scale. Autogenous self-healing is valid for small- and large-scale beams in terms of crack characteristics/flexural parameters and is found to improve with the increased FA/PC, decreased A/CM, in the presence of nanomaterials, and with the increased fiber amount (regardless of the type). Outcomes of this research are thought to be important because they show the manufacturability of deflection-hardening concrete with large amounts of coarse aggregates at large scale and validate their autogenous self-healing capabilities, which are important for the real-time applicability of such mixtures in actual field conditions.