Effect of Elevated Temperature on Meso- and Micro-Structure and Compressive Strength of High-Strength Concrete and Mortar Containing Blast-Furnace Slag

抄録

Meso- and micro-structures and residual compressive strengths of high-strength concrete (HSC) and mortar (HSM) with blast-furnace slag (BFS) replacement ratios of 0% - 55% were experimentally obtained after 20℃ - 800℃, respectively. The results indicated that the meso-crack started to appear after 400℃ and grew into the main crack of HSC and the net-like crack of HSM with the increasing temperature. Calcium hydroxide could dehydrate above 400℃ and calcium carbonate could decarbonate above 600℃ in paste. The micro-morphology of paste became more and more loose from 400℃ to 800℃. Residual compressive strengths of HSC and HSM reduced as the temperature rose, except for the strength recovery of HSM after 400℃. The compressive strength of HSC had a reduction with the increasing BFS replacement ratio at 20℃, but HSC with 18% BFS had the highest residual compressive strength above 200℃. An increasing BFS replacement ratio could reduce the residual compressive strength of HSM after the temperatures of 20℃ - 600℃. Equations for estimating residual compressive strengths of HSC and HSM as well as the relationship between them were proposed with the temperature and the BFS replacement ratio as two primary parameters.