Effects of plastic fiber straw and metakaolin on the mechanical properties and impact behavior of recycled aggregate concrete

This article presents the individual and simultaneous effects of metakaolin reactive silica and plastic fiber straw on the mechanical properties and impact behavior of concrete made from natural aggregates and those of recycled aggregates containing 50% replacement. The addition of metakaolin alone or with the plastic fibers only improved the mechanical performance of all the mixtures at a later age (90 days). However, the addition of plastic fibers slightly increased the compressive and tensile strengths of natural aggregate concretes with a decrease in those of recycled aggregate concretes. This deficiency was compensated for by the reactive effect of the silica provided by metakaolin. An optimum of 1% has been specified in plastic fibers for compressive strength for all composites. Natural concretes and those recycled without metakaolin and plastic fibers present a fragile behavior, the energy absorbed at the first crack is substantially equal to that at failure. When these components are used simultaneously, their behavior becomes ductile and the fracture energy is significantly higher than the control concrete and that of the first crack.