Effect of thermal treatment on pozzolanic activity of excavated waste clays

Abstract

Samples of excavated waste clays were characterized by X-ray fluorescence, laser granulometry, specific surface area, X-ray diffraction, and thermo-gravimetric analysis. Excavated clays were calcined at 550 ºC and 650 ºC in order to investigate their potential pozzolanic activity. The effect of thermal activation also was determined by factorial experiments with two factors in randomized complete blocks. Pozzolanic activity was evaluated by calcium hydroxide fixation, the Frattini test and the compressive strength at 7 and 28 days. The results indicate that calcined excavated clays at 650 ºC presented pozzolanic activity at 7 days and showed an increase percentage of compressive strength on average 13%.