Effect of temperature on stress strain behavior of high calcium fly ash and alccofine blended high strength concrete

Abstract

In present study, the effect of temperature on stress–strain response under monotonic compressive loading is studied for two blended high strength concrete (HSC, viz., high calcium fly ash blended HSC (FC-HSC) and alccofine blended HSC (AL-HSC)) mixes. The experimental studies have been carried out with a 100 mm × 100 mm × 100 mm cube specimen and tested at 28 day of curing. For each mix, four sets of specimens, including control specimen and those exposed to elevated temperatures of 80 °C, 140 °C and 160 °C for 6 h were considered for the study. The stress–strain behavior of HSC mixes at elevated temperatures exhibits a distinct effect of material composition. The increasing exposure temperature increases peak stress for AL-HSC, whereas it initially decreases and then increases for FC-HSC. The results from the study confirm that elevated temperature contributes to stiffening of the pre-peak region, but the effect on peak stress is influenced by the material composition. The effect of elevated temperature on microstructural change is evaluated through thermo gravimetric analysis and the results are compared for FC-HSC and AL-HSC. The weight loss (30–160 °C) representing calcium silicate hydrate (CSH) degradation decreases with increasing exposure temperature for FC-HSC, whereas it remains range bound for AL-HSC. On the other hand, weight loss (400–500 °C) representing degradation of calcium hydroxide (CH) remains range bound for FC-HSC while it increases with increasing exposure temperature for AL-HSC. The observed results suggest that increasing exposure temperature contributes to CSH degradation in FC-HSC, whereas it enhances CH formation for AL-HSC. The study results provide useful insight on the effect of elevated temperature on the stress–strain behavior of blended HSC with flyash and alccofine.