Substitution of Bentonite Aggregates for Pumice in Lightweight Concretes

Ismail, A.I.M. ; Souaya, E. R. ; Fathy, M. ; Abd El-Hakeem, A.
Substitution of Bentonite Aggregates for Pumice in Lightweight Concretes
Refractories Manual (2017) 47-52
Special Technologies

Abstract:
Bentonite aggregates were pelletized in different grain sizes and the green pellets were then dried for 48 hours and fired in a rotary kiln for one hour at 1150 °C with a heating rate of 20 K/min. During firing, the organic compounds in the clay burn off, forcing the pellets to expand and become honeycombed as the outside surface of each granule melts and is sintered. The resulting pellets were lightweight, porous and had high crush resistance. We examined the possibility of using bentonite in different grain sizes as a replacement for pumice in lightweight concretes.Both pumice and bentonitic materials were investigated for their chemical and mineralogical composition (using XRF, XRD, SEM and EDX). Their physico-mechanical properties in concrete pastes, including compressive strength, were evaluated. Phase composition was also determined by XRD, SEM and EDX. The compressive strength and particle and bulk density results showed that these lightweight concretes were affected by the type, shape and percentage of aggregates, the cement paste characteristics, and the interfacial zone between the cement and aggregates. Calcium silicate-hydrate (CSH) and calcium aluminate-hydrate (CAH) minerals were responsible for the strength of the concrete.

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