Mechanical properties of rubberized concrete containing recycled concrete aggregate and polypropylene fiber

Abstract

Owing to the enormous consumption of natural aggregates in concrete production and its further proliferating demand due to the rapid growth of population and urbanization, a significant crisis of virgin aggregates are forecasted in the near future. Additionally, extensive amounts of car tires reach the end of their useful service life and are being dumped in landfills all over the world. Furthermore, the accelerated rate of modernization and industrialization in addition to the increased number of no longer serviceable structures has led to the generation of a tremendous amount of construction and demolition (C&D) waste worldwide. These waste tires and C&D waste can be refined and recycled though further processing for use in concrete as aggregates. Mechanical properties of concrete containing modified crumb rubber (CR) and recycled concrete aggregate (RCA) at three replacement levels of natural fine aggregates (NFA) and natural coarse aggregates (NCA), were investigated to assess their potential for use in concrete. Also, polypropylene fibers at a level of 0.5% by volume of concrete were added to the mixtures to analyze their effectiveness in improving strength properties of concrete containing CR and RCA. In total, 15 different combinations of concrete mixtures were cast with CR, RCA, and PP fiber. Rubber particles were pre-treated using a 20% concentrated solution of sodium hydroxide (NaOH) based on the experimental test results on treated rubberized mortar specimens. Mechanical properties were assessed in terms of compressive, splitting tensile, and static flexural strength of concrete. The compressive stress-strain behaviour and flexural load-deflection behaviour of the concrete mixtures were also analyzed. Results show that a combination of RCA at 50% and CR at 10% replacement level exhibited remarkable mechanical properties. The addition of PP fibers also contributed to improving the flexural behaviour of the concrete mixtures with CR at 20% replacement level.