Studies on enhanced thermally stable high strength concrete incorporating silica nanoparticles

The performance of silica nanoparticles incorporated high strength concrete (SNPs-HSC) has been evaluated under elevated temperature conditions by exposing up to 800 degrees C, followed by cooling to ambient temperature before performing experiments. Time-temperature studies revealed that incorporation of silica nanoparticles (SNPs) in concrete mix delays the heat transfer by 11%, 18%, 22% and 15% at 200 degrees C, 400 degrees C, 600 degrees C and 800 degrees C respectively thereby, decreasing the rate of degradation as compared to the conventional high strength concrete (HSC). A reduction in weight loss was observed in SNPs-HSC specimens after exposure to 200 degrees C, 600 degrees C, and 800 degrees C; whereas at 400 degrees C the weight loss quantity was similar to 3.5% higher than the control HSC specimens due to the evaporation of water from calcium silicate hydrate (C-S-H) gel. On exposure up to 400 degrees C for 2 h, the compressive strength and split-tensile strength increased by 40% and 13% respectively, for SNPs-HSC specimens, whereas in control HSC specimen's strength didn't increase after 200 degrees C. A higher residual compressive (7%) and split-tensile strength (8%) was found to be in SNPs-HSC specimens exposed to 800 degrees C for 2 has compared to the control HSC specimens. The stress-strain curves revealed that SNPs-HSC specimens exhibits brittle failure up to 600 degrees C whereas in control HSC brittle failure was observed only up to 400 degrees C. Microstructural studies performed on the samples taken from the core of the 400 degrees C exposed SNPs-HSC revealed the formation of higher C-S-H content and lower amount of calcium hydroxide (CH) leading to their enhanced mechanical and thermal stability. (C) 2017 Published by Elsevier Ltd.