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

Abstract

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°C-800°C, respectively. The results indicated that the meso-crack started to appear after 400°C 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°C and calcium carbonate could decarbonate above 600°C in paste. The micro-morphology of paste became more and more loose from 400°C to 800°C. Residual compressive strengths of HSC and HSM reduced as the temperature rose, except for the strength recovery of HSM after 400°C. The compressive strength of HSC had a reduction with the increasing BFS replacement ratio at 20°C, but HSC with 18% BFS had the highest residual compressive strength above 200°C. An increasing BFS replacement ratio could reduce the residual compressive strength of HSM after the temperatures of 20°C-600°C. 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.

Reliability analysis of the residual moment capacity of high‐strength concrete beams after elevated temperatures

“…From 400 to 800°C, the SD of the residual cube and prism compressive strengths of HSC was decreased almost linearly by 90.87 and 85.45%, respectively. The previous cracks develop quickly and scatter in the entire specimen above 400°C, causing the decrease of the heterogeneity of HSC, which probably was the reason for the SD decrease 4 . After 20, 200, 400, 600, and 800°C, the SD of the residual cube compressive strengths of HSC was 93.79, 119.22, 114.25, 76.78, and 34.41% greater than those of the residual prism compressive strengths, respectively.…”

“…From 20 to 400°C, the SD of the residual cube and prism compressive strengths of HSC was increased by 209.96 and 183.35%, respectively. These obvious increases of the SD probably were due to the cracks caused by the elevated temperature enhanced the heterogeneity of HSC, which was a decisive origin of the variability of concrete properties 4,32 . From 400 to 800°C, the SD of the residual cube and prism compressive strengths of HSC was decreased almost linearly by 90.87 and 85.45%, respectively.…”

“…The result showed that the residual strength of HSC was reduced by 70–80% when the temperature ranged from 20 to 800°C. Magda 3 and Li et al 4 studied the influence of the silica fume (SF) within a replacement ratio of 0–20% and blast‐furnace slag within a replacement ratio of 0–55% on the residual cube compressive strength of HSC after elevated temperatures, respectively. The result of Magda 3 showed that as compared to HSC without SF, the residual cube compressive strength of HSC within a SF replacement ratio of 20% was respectively increased by 30.61, 52.94, 58.54, 60.87, 250, and 600% after 22, 105, 300, 400, 600, and 800°C.…”

“…The result of Magda 3 showed that as compared to HSC without SF, the residual cube compressive strength of HSC within a SF replacement ratio of 20% was respectively increased by 30.61, 52.94, 58.54, 60.87, 250, and 600% after 22, 105, 300, 400, 600, and 800°C. Li et al 4 suggested that HSC with a blast‐furnace slag replacement ratio of 18% had better elevated temperature resistance than the other HSC containing blast‐furnace slag.…”

Experimental Study on Mechanical Properties of Nano-Alumina-Modified Cement Composites Exposed to High Temperatures

“…Nazari et al [17] investigated the Processes 2024, 12, 94 2 of 16 microstructural and mechanical behaviors of ordinary Portland cement and geopolymer concrete affected by thermal shock. Li et al [18] obtained the effect of the blast furnace slag replacement ratio (0%~55%) on the meso-and microstructure and compressive strength of high-strength concrete and mortar after treatment at 20~800 • C.…”