Abstract:
This paper presents the results of experimental testing of four types of mixes of self-compacting concrete (SCC). Fly ash which was added in three mixes in proportions of twenty percent, thirty percent and forty percent. A mix without fly ash addition was used as control mix. Samples made of these mixes were heated from 200°C (392°F) to 800°C (1472°F) in increments of 200°C (392°F). Samples were inspected visually after heating and mass loss and residual strength were determined. Scanning electron microscope (SEM) was used to understand the results. It was found that fly ash played a major role in improvement of fresh properties of a mix. Compressive strength of the mixes made with the addition of fly ash was comparable to the control mix at 56 days. Densified pore structure caused improvement in durability properties with increase in fly ash dosage. The mix with thirty percent fly ash showed fifty four percent higher residual strength compared to the control mix after heating at 800°C (1472°F). SEM micrograph also showed comparatively stable morphology for this mix. Decomposition of calcium silicate hydrate (C-S-H) and calcium hydroxide (C-H) into silicate was witnessed in SEM images, which was the cause of deterioration.