AFt/AFm distribution & microstructure-properties of rice husk ash concretes thermal-cured

Abstract

This experimental study aims to present the behavior of cement composites containing rice husk ash over time previously undergone high thermal curing. A specific initial thermal curing up to 85°C was designed to trigger delayed ettringite formation (DEF) as well as a specific exposure environment, by water immersion at 38°C, over one year. Expansion measurements and microstructural analyses were performed to evaluate the level of attack and the integrity of mortars and concretes. To complement the study, mechanical properties of concretes were assessed to detect the level of damages by delayed ettringite formation expansion. Mortar performed differently from concrete, bringing risks of mistaken conclusions about admixture performance. Anyway, concrete tests have indicated that rice husk ash was able just to reduce the level of expansions, nonetheless, the contents were not enough to mitigate completely the generated expansions and avoid delayed ettringite formation and, consequently, damage. Highlights • The potential of rice husk-ash to mitigate DEF was explored. • A comparison between the behavior of mortar and concrete mixtures was evaluated. • The expansions, mechanical properties and microstructure analyses were studied. • Mortar and concrete performed different. • The admixture of rice husk-ash did not play enough mitigative performance for DEF at content of 8% by cement weight.