Influence of Mixture Composition and Type of Cementitious Materials on Enhancing the Fresh Properties and Stability of Self-Consolidating Rubberized Concrete

Abstract

An experimental investigation was conducted to study the development of self-consolidating rubberized concrete (SCRC) with improved flowability, passing ability, stability, and strength for multiple structural applications. The investigation particularly aimed to maximize the percentage of used crumb rubber (CR) in SCRC while minimizing the reduction in strength and stability of the developed mixtures. The experimental test parameters included CR percentage (0–50% by volume of sand), binder content (500–550 kg/m3), coarse aggregate size (10–20 mm), air entrainment, and supplementary cementing material (SCM) (fly ash, ground granulated blast-furnace slag, and metakaolin). The performance of the developed SCRC was evaluated based on the results for compressive strength, flowability, passing ability, high-range water-reducer admixture (HRWRA) demand, coarse aggregate segregation, and CR distribution. The results indicated that mixtures with 500 kg/m3 binder content had acceptable strength, fresh properties, and stability with up to 15% CR replacement. Using 550-kg/m3 binder content improved SCRC mixture stability and allowed up to 20% CR to be used safely. Compared with the other tested SCMs, metakaolin (MK) significantly improved mixture viscosity and particle suspension/distribution, which allowed the use of up to 30% CR in SCRC mixtures. The results also showed that, despite the reduction in compressive strength in mixtures with entrained air, using air entrainment in SCRC with MK further improved the fresh properties of these mixtures and allowed up to 40% CR to be used with acceptable compressive strength (25.7 MPa) and with no sign of segregation.