Effect of crumb rubber content on setting time of self-compacti̇ng mortars

The study herein was aimed at investigating the influence of using the crumb rubber on the initial and final setting times of the self-compacting mortar. In addition, fresh properties and compressive strength of the mortars were investigated. For this reason, two self-compacting mortar series were designed at total binder contents of 540 and 500 kg/m3 and water-to-binder ratios of 0.33 and 0.40, respectively. The fly ash was incorporated to the mixtures as 25% of total binder content by weight. The natural sand was replaced with crumb rubber at the level of 0, 5, 10, 15, 20, and 25% by volume. Totally, 12 self-compacting mortar mixtures were produced and they were tested for mini-slump flow diameter and time, mini V-funnel flow time, initial and final setting times. Additionally the compressive strength of the mixtures was measured at the age of 3, 7, 28, 56, and 90 days. The results indicated that the crumb rubber utilization had negative effects on the fresh properties but the manufactured mortars was satisfied the self-compactibility criteria. Besides, increasing the water-to-binder ratio decreased the demand for superplasticizer and enhanced the fresh properties. Moreover, the compressive strength of the mortars was decreased by increasing the crumb rubber content.