Mohamed K. Ismail

Ductility and Cracking Behavior of Reinforced Self-Consolidating Rubberized Concrete Beams

AbstractThis paper investigates the applicability of using optimized self-consolidating rubberized concrete (SCRC) and vibrated rubberized concrete (VRC) mixtures in structural applications. The curvature ductility, ultimate flexural strength, and cracking characteristics of different SCRC and VRC mixtures were tested using large-scale reinforced concrete beams. The variables were crumb rubber (CR) percentage (0–50% by volume of sand), different binder contents (500–550  kg/m3), inclusion of metakaolin (MK), use of air entrainment, and concrete type. The performance of some design codes were evaluated in predicting the cracking moment and crack widths of the tested beams. The results indicated that although the flexural capacity of the tested beams decreased with the addition of CR, adding CR improved the beams’ curvature ductility and reduced its self-weight. Adding CR into concrete also appeared to limit the flexural crack widths but with a slightly higher number of cracks compared to beams without CR. ...

Performance of Full-Scale Self-Consolidating Rubberized Concrete Beams in Flexure

This research investigated the performance of full-scale self-consolidating rubberized concrete (SCRC) and vibrated rubberized concrete (VRC) beams in flexure. The beam mixtures were developed with a maximum possible percentage of crumb rubber (CR) (0 to 50% by volume of sand) while maintaining acceptable fresh properties and minimum strength reduction. The mixture variables included different binder contents, the addition of metakaolin, and the use of air entrainment. The performance of the tested beams was evaluated based on load-deflection response, concrete strain/stiffness, cracking behavior, first crack load, ultimate load, ductility, and toughness. In general, increasing the CR content decreased the mechanical properties, first crack load, stiffness, and self-weight of all SCRC and VRC beams. However, using up to 10% CR enhanced the deformation capacity, ductility, and toughness of tested beams without affecting the flexural capacity. This improvement in the deformation capacity, ductility, and toughness appeared to continue up to 20% CR (but with a slight reduction of the flexural capacity) and then reduced with further increases in the CR content. The results also indicated that although it was possible to produce VRC beams with higher percentages of CR (50% compared to 40% in SCRC), this increased percentage only gave VRC beams an advantage in terms of self-weight reduction, while it had a limited contribution in enhancing the structural performance of the beams.

Impact Resistance and Mechanical Properties of Self-Consolidating Rubberized Concrete Reinforced with Steel Fibers

AbstractThis study evaluates the impact resistance and mechanical properties of a number of developed self-consolidating rubberized concrete (SCRC) mixtures reinforced with steel fibers (SFs). In this research, SFs were used to compensate for the reduction in tensile and flexural strength that resulted from adding high volumes of crumb rubber (CR). SFs were also used to exploit the beneficial interaction between SFs and CR to develop low-density concrete with higher impact resistance. The experimental variables were different replacement levels of fine aggregate volume by CR (0–40%), binder content (550–600  kg/m3), SF volume fractions (0, 0.35, 0.5, 0.75, and 1%), and size of SFs. Tests included fresh properties, compressive strength, splitting tensile strength (STS), flexural strength (FS), and impact loading (drop-weight on cylindrical specimens and flexural impact loading on small-scale beams). The results indicated that adding CR to concrete improved the impact energy absorption and ductility, wherea...

Steel-Fiber Self-Consolidating Rubberized Concrete Subjected to Impact Loading

This investigation was carried out to evaluate the combined effect of crumb rubber (CR) and steel fibers (SFs) on improving the impact resistance of self-consolidating concrete (SCC) mixtures. Seven SCC mixtures were developed with varied percentages of CR (0–15% by volume of sand) and SF’s volume of 0.35%. The performance of the developed mixtures was evaluated by testing the fresh properties, compressive strength, splitting tensile strength (STS), flexural strength (FS), and impact loading (drop weight on cylindrical and beam specimens). The results indicated that inclusion of CR decreased the compressive strength, STS, and FS of the tested mixtures, while the impact resistance obviously increased. Reinforcing CR mixtures with 0.35% SFs could compensate the reduction in the tensile strength resulting from adding rubber and further increase the resistance of mixtures to impact loading, achieving mixtures with promising properties for multiple structural applications.