Effect of temperature on pozzolanic reaction of Tunisian clays calcined in laboratory

Abstract

The use of natural calcined clay as supplementary cementitious materials for the replacement of a portion of cement has become increasingly interesting. It is used for reducing the cement content in mortars and concrete production and also for improving strength and durability of concrete construction. In this context, the objective of this study was to make calcined clay in laboratory using two Tunisian clays burnt at 600, 700 and 800 °C and to study the effect of temperature on Pozzolanic reaction in terms of physical, mechanical and microstructure properties. Here, we studied the thermal and chemical properties, mechanical compressive strength of mortars, electrical conductivity as well as the physical properties, namely Blaine specific surface area, average particle diameter, pycnometer density, to evaluate its pozzolanic effect by substitutions of cement (5, 10, 15 and 20%). The results show the beneficial effect of adding calcined clay at different temperatures of calcinations on these properties. Besides, the average particle diameter increased with temperatures which agglomerate the particles. The Blaine specific surface area of calcined clay exceeded that of cement. Furthermore, the substitution of cement by calcined clay enhanced the compressive strength. All samples showed the development of strength between 28 and 90 days.