Experimental research on controlling the floating of rubber particles in mortar based on the layering degree index

Abstract

Crumb rubber concrete is characterized by good deformability and toughness, high damping ratio, excellent anti-cracking ability and high energy consumption. However, the apparent density of rubber is far lower than the density of cement-based materials, which results in the easy separation of rubber particles from cement-based materials in the mixture; this separation causes the rubber particles to float upward in a mixture. This study proposes an experimental method based on the layering degree and defines and calculates the uniformity of the rubber distribution. Cellulose ether is added to the mortar with a 0.45 water-cement ratio to improve the consistency and layering degree of the mixture, to prevent the rubber particles from floating upward and to increase the uniformity of the mortar. Through the experiment of quadratic orthogonal rotation combination, this paper studies the influence of the amount of the cellulose ether (0–43.2 g/m3) and the substitution rate of rubber for sand (0–0.5) on the consistency of the mix, the layering degree, the uniformity and the 28-day strength of the crumb rubber mortar; then, studies are performed on the inhibition effect of cellulose ether on the floating of rubber. The results show that cellulose ether mixed into rubber can significantly improve the consistency and layering degree of the mixture; we can control the floating of rubber in mortar by controlling the layering degree of the mortar mixture, and the index of the layering degree varies with the substitution rate of rubber for sand. Finally, this work establishes the relationship between the substitution rate of rubber and layering degree of a mixture, which is used to effectively evaluate the uniformity of rubber mortar. This paper can play a guiding role in the practical applications of crumb rubber mortar, crumb rubber concrete and other lightweight aggregate concrete.