Effect of Calcite on Fresh and Hardened Properties of Expanded Perlite Blended Cement Mortars

Abstract

Expanded perlite, which is mostly used for purposes such as lightweight concrete and insulation, contains a high percentage of silica and alumina. Problems in early-term strength development occur with the high-volume substitution of normal weight and lightweight pozzolanic materials in the production of cement. It was thought that it would be important to examine the early period fresh and hardened properties of expanded perlite blended cement including nano and micronized calcite minerals with high reactivity and high specific surface area/volume ratio. For this purpose, a total of nine different mortar mixtures containing 0%, 6% and 18% expanded perlite and 5% nano and micronized calcite were designed for replacing by cement. For mortar samples modified with nano and micronized calcite and containing expanded perlite at different rates; mini slump flow test, standard consistency, setting times and soundness (Le Chatelier Method) tests/analyses were performed as fresh and early period properties. In addition to this, compressive strength and ultrasound pulse velocity tests were performed for the curing ages of 7, 28 and 120 days as hardened properties. Experimental results showed that expanded perlite negatively affects the early and hardened properties of mortars, and in general, improvements are achieved with nano/micronized calcite substitution. 23.2% and 45.4% of strength development has been achieved in the mixture including both calcite and expanded perlite within the curing ages of 7-28 days and 7-120 days, respectively. Also, a maximum of 5.7% of reduction was observed in EP blended cement mortars, including 18% of EP. Since nano-sized calcite has a higher surface area compared to micronized calcite, better contributions to the fresh and hardened properties were observed in the utilisation of nano-sized calcite.