Lightweight Aggregate Fines as Pozzolanic Additive for High-Performance Concrete

Synopsis: Finely ground lightweight aggregate (LWA) based on calcined and expanded clay has been proven to be quite an effective pozzolan. When replacing cement with 15% LWA fines the concrete compressive strength becomes more sensitive to temperature and time, and 28 day strength is typically 10-15% lower when cured at 5°C, equal when cured at 20°C and 15% higher when cured at 35°C. However, cement replacement by such a mineral increases the concrete resistance to chloride ingress, reduces alkali aggregate reactions and increases the sulfate resistance. Carbonation rate, on the other hand, is somewhat increased as for most pozzolana. Freezing and thawing resistant concrete can also be made with this additive. Thus, finely ground LWA can be utilized to make high performance concrete.