Abstract
The use of natural calcined clay as supplementary cementitious materials as a replacement of a portion of cement in concrete is becoming interesting. Although calcined clay is used to improve strength and durability of structural concrete, there are few studies on the effect of calcined clay on lightweight aggregate concrete (LWC). In this context, the objective of this study was to make a calcined clay in laboratory using Tunisian clay and to evaluate its pozzolanic effect by (5% and 20%) substitutions of cement in LWC of expanded clay and normal concrete (NC), on compressive strength, water absorption and sorptivity, resistance to the chloride ions penetration, chemical attack and carbonation. Standard tests, such as accelerated migration and immersion tests, were conducted. The results show the beneficial effect of adding calcined clay on the fresh state, compressive strength, microscopic structure and durability of lightweight and ordinary concretes. Addition has a beneficial effect on the increase in compressive strength from 28 days to 90 days and the reduction of capillary water absorption for NC and LWC. The effective diffusion coefficients of chloride ions of calcined clay are low compared to concrete without addition. Significant reductions in the chloride penetration depth are observed.