Early-age mechanical properties and electrical resistivity of geopolymer composites

Abstract

Cement-less and/cement-like geopolymer mortars were made with pulverised fuel ash (PFA) or ground granulated blast furnace slag (GGBS) activated by alkali with different alkali moduli (AM) and alkali dosage (AD). Once synthesised the samples were cured at 20°C and 70°C up to 28 days. The flexural and compressive strengths of these samples at early ages up to 28 days were tested conforming to BS EN196-1:2005. The electrical resistivity of these materials was monitored using a set of non-contacting electrodes to the age up to 7 days to characterise the geopolymerisation process from a physical phenomenon point of view. The effects of AD and AM on the early-age mechanical strengths and electrical resistivity of geopolymer materials were examined from the experimental results. The correlation between strength development and electrical resistivity was studied. The geopolymerisation process was characterised by a 5-stage model, based on electrical resistivity, analogue to hydration process of Portland cement. This research therefore proposes an alternative method for characterisation of geopolymerisation of geopolymers different from traditional methods based on chemistry. It is expected that such a physical phenomenon model will be better accepted by structural engineers for better promotion of usage of geopolymer composites, a type of low carbon and more sustainable binder-based materials, in construction.