Rheology control of alkali-activated fly ash with nano clay for cellular geopolymer application

Gadkar, Anvit and Subramaniam, Kolluru V.L. (2021) Rheology control of alkali-activated fly ash with nano clay for cellular geopolymer application. Construction and Building Materials, 283 (122687). ISSN 09500618

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Abstract

An efficient method of production for cellular geopolymer from an alkali-activated fly ash (AAF) binder paste by controlling its rheological behavior is presented. The AAF binder paste exhibits a complex rheological behavior, which is influenced by the solids loading and the composition of the activating solution. The constant strain rate response of the AAF binder paste varies between a yield-type and Maxwell flow behavior. Entrained porosity created in the hardened geopolymer matrix with the use of Aluminum powder exhibits a dependence on the constant strain rate response of the AAF binder paste. A cellular structure is achieved in pastes which exhibit a yield-type behavior. The addition of nano-clay fundamentally alters the constant strain rate response of AAF binder pastes producing a yield-type response in suspensions that exhibit a Maxwell flow behavior. There is also an increase in the peak stress in the constant strain rate response with nano-clay. A stable cellular structure is produced in the AAF binder pastes which exhibit a Maxwell-flow type response with the addition of clay. Montmorillonite is more effective than Bentonite in enhancing the yield stress of the AAF binder pastes. The importance of identifying the yield stress of the AAF binder pastes for creating a stable cellular structure within the hardened geopolymer matrix is established. The cellular structure in the geopolymer matrix can be tailored with the rheology control of the AAF binder pastes using nano-clay.

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