Influence of Crumb Rubber on the Drying Shrinkage and Plastic Shrinkage Cracking of AASM

The alkali-activated slag mortar (AASM) has disadvantages of high shrinkage and therefore low crack resistance. In this paper, water quenched raw slag was used to replace sand for making AASM, and effects of crumb rubber on the drying shrinkage and plastic shrinkage cracking of AASM were investigated. The experimental results showed that the incorporation of crumb rubber into AASM reduced the drying shrinkage of AASM and improves the plastic shrinkage cracking resistance. Compared with the referenced mortar, after the 90-day drying the shrinkage of AASM containing 3% rubber decreased by 28.5% and crack index decreased by 64%. However, the addition of higher dosage of crumb rubber may bring negative effect on the flexural strength and the compressive strength of AASM. It is therefore proposed that the optimum rubber content be around 3% in order to balance both the mechanical performance and the plastic and the drying shrinkage.