Investigations on the coefficient of thermal expansion of a low‐calcium fly ash‐based geopolymer concrete

Abstract

In this paper, the deformation of a sealed low‐calcium fly ash‐based geopolymer concrete during heat curing was investigated. The sealed sample underwent thermal deformation due to temperature change and possible autogenous deformation related to alkaline activation of the fly ash. For the separation of the both deformation types the coefficient of thermal expansion (CTE) is a paramount issue. The CTE evolution of the geopolymer concrete from plastic to hardened state was determined by means of a new method proposed in this paper. Based on the experimental results, the CTE is mathematically described as a function of the so‐called equivalent time. The thermal dilation during heat curing was then calculated using the CTE equation. The autogenous shrinkage of the fly ash‐based geopolymer concrete is comparatively low. The thermal dilation during the heat curing cannot completely reverse, if the concrete is cooled down to its temperature at the beginning of the heating. After the heat curing no further autogenous deformation was observed on sealed samples continuously cured at room temperature.