Incidence of limestone powder, natural pozzolan and slag on concrete exposed to high temperature

Abstract

The interest in reducing the content of Portland cement used in construction, which results from the environmental need of reducing CO₂ emissions to the atmosphere, generates the necessity of knowing how materials that are used in partial or total replacement of cement affect the concrete properties. One of the properties of interest is the performance of these concretes when exposed to high temperatures. In this work, concretes made with 3 types of mineral admixtures (limestone powder, ground granulated blast-furnace slag and natural pozzolan) are studied in different proportions of cement replacement (20 and 60 % for slag and pozzolan, and 10 and 30 % for limestone powder), and contrasted with a control concrete. Strength, weight, ultrasonic pulse velocity and dynamic modulus of elasticity were evaluated both before and after exposure to 500 °C for one hour. The mineral admixtures did not substantially modify the performance of the concrete against the aforementioned exposure, but the relative benefits offered in comparison with the control concrete before the heating (increase in cement efficiency in all cases and improvements in strength, dynamic modulus of elasticity and ultrasonic pulse velocity in some cases), are preserved after deterioration by temperature.