Improvement of Mechanical Behavior of Rubber–Cement Mortars by Catalytic Hydration

Abstract

This study examines the systematic decrease of concrete compressive strength with rubber scrap from the hydration reaction point of view. The work was focused on the determination of the hydration rate equation of normal, catalyzed, and rubberized Portland cement pastes. The basic idea was to prove the inhibiting effect of zinc compounds from rubber on the hydration kinetics of Portland cement. From the Jander rate equation, the data strongly suggested that the hydration kinetics of the rubberized cement composites could be improved if an accelerator were incorporated. Once the hydration reactions were improved by means of the catalyst, the mechanical properties of Portland cement/rubber scrap composites were improved. From the composite models for Young’s modulus, the Maxwell dispersed phase model was used to relate the compressive strength of rubberized cement in terms of rubber content. After 28 days, the control cement reaches a compressive strength of 52 MPa; meanwhile, the catalyzed composite incorporating 10% by weight rubber scrap and 2.5% by weight of silica fume withstands a compressive strength of 61 MPa. Without a catalyst, the same material tolerates just 40 MPa.