Investigation on engineering properties and micro-structure characteristics of low strength and high strength geopolymer composites subjected to standard temperature exposure

Fire accidents are common and one among the serious hazards faced by civil infrastructures; therefore, appropriate measures have to be taken while designing the buildings and structures to ensure the safety of the residents. Reducing the damage caused by fire and the collapse of structural elements are the primary significance in designing concrete structures. An experimental study was conducted to examine the mechanical properties of temperature exposed concrete specimens following ISO 834 standard fire curve. Present investigation examines the performance of Geopolymer concrete (GPC) after exposed to temperature exposure. Two types of concrete namely, low and high strength GPC were cured under two curing regimes viz, room temperature curing and oven curing was adopted in this study. The GPC specimens were heated to 821 °C, 925 °C, 986 °C and 1029 °C, following the rate of heating was in accordance with ISO 834. Influence of elevated temperature on GPC specimens were examined by visual inspection, weight loss, strength loss and micro-level studies including Scanning Electron Microscope (SEM). Results from the study reveals that, the strength of high strength concrete was more prone to temperature exposure. Room temperature cured GPC specimens possessed higher residual strength than oven cured specimens for all the heating durations (marginal variation less than 5%). Crushing Index (CI) of 8.1% was regarded as optimal value for coarse aggregates (CA) to sustain its strength at a temperature of 821 °C. The phase change and dehydration of geopolymeric gel were observed in SEM analysis, and strength loss of CA are considered as the influencing parameters for degradation of concrete at higher temperature exposure. High strength concrete is more prone to strength loss than low strength concretes.