The impact of supplementary cementitious materials on the rheological and mechanical properties of mortars based on quarry waste sand

Abstract

Mineral substances used as additives in cement plants or as additives in the making of concrete contribute through their physical, hydraulic, and pozzolanic activity to improving the behavior of cements in both the fresh and hardened states. Several types of additions are well known, such as natural pozzolans, fly ash, blast furnace slag, and silica fume. These products become more active in the alkaline solutions of cement and give rise to new hydrates that impart greater mechanical strength and better durability to concretes. Through their surface activity and granular distribution, they play a fundamental role in the rheological and mechanical behavior of mortars and concretes. Quarry waste sand (QWS) is generally stockpiled to be eventually sold at very low prices. For this reason, its use in the production of concrete and mortar is increasingly becoming a necessity to protect the environment and meet the needs of the construction and public works sector.This study aims to investigate the effect of using both supplementary cementitious materials (SCM) and quarry waste sand(QWS) to improve some properties of mortar. Ordinary cement is replaced by 10%, 20% and 30% of silica fume (SF), natural pozzolan (NP) or ground blast-furnace slag (GBFS) by weight and the properties of the QWS sand -based mortar are compared to those of natural sand (NS) based mortar. In this study, the slump, superplasticizer requirement, rheological parameters, mechanical strength, and water absorption are investigated. The results obtained show that QWS sand mix has the best workability and requires less superplasticizer dosage. When SCM were used, a drop-in workability is shown and more superplasticizer is required. Also, QWS sand makes the mortar strength 2 and 1.5 times higher than that of NS and becomes 42% higher with 10% SF. Adequate relationships have been established to predict mechanical strengths as a function of test parameters with high correlation coefficient and low root mean square error.