Investigating Ultrasonic Pulse Velocity Method for Evaluating High-Temperature Properties of Non-Sintered Hwangto-Mixed Concrete as a Cement Replacement Material

Abstract

Research on alternative cement materials is active worldwide, and in terms of fire safety, research on the evaluation of high-temperature properties of alternative materials is very important. Studies on concrete mixed with hwangto have been conducted by several researchers, but studies on high-temperature properties are lacking. Therefore, in this study, we evaluated the mechanical properties of concrete by partially replacing cement with non-sintered hwangto (NSH) at high temperatures. Normal concrete without NSH mixing and non-sintered hwangto concrete (NSHC) with HNT replacement were prepared as the specimens. The W/B of the concrete was set to 41 and 33, whereas the NSH replacement ratio was 15 and 30% of the cement. The target heating temperatures were set to 20, 100, 200, 300, 500, and 700 °C, and the heating rate was maintained at 1 °C/min. The following were calculated to evaluate the mechanical properties of the specimens: mass loss, compressive strength, ultrasonic pulse velocity (UPV), and modulus of elasticity. After analyzing the correlation between residual compressive strength and UPV, we proposed a compressive strength prediction model using different values of W/B for NSHC. Experimental results suggest that mass loss (%) shows a decreasing trend as NSH increases. In terms of residual compressive strength, residual compressive strength at W/B 41 increased with NSH replacement, whereas residual compressive strength values for W/B 33 were observed regardless of NSH replacement. Residual UPV showed a similar trend, regardless of the NSH replacement ratio, and residual modulus of elasticity was low at all W/B ratios as NSH replacement increased. A linear equation with a high correlation coefficient (R2) was proposed to predict compressive strength, and the linear value of W/B 41 was slightly higher than that of W/B 33.

Evaluation on Early Strength Development of Concrete Mixed with Non-Sintered Hwangto Using Ultrasonic Pulse Velocity

“…This UPV measures the time for a signal to arrive from the transmitting converter to the receiving converter. When the signal reaches the receiving converter, the speed appears on the display and the experiment can be measured through that value [31].…”

An overview on spalling behavior, mechanism, residual strength and microstructure of fiber reinforced concrete under high temperatures

“…Consequently, this can lead to explosive spalling and a decline in the mechanical integrity of the concrete (Handoo et al, 2002;Li et al, 2004;Caetano et al, 2019;Krishna et al, 2019). Kim et al (2023) evaluated the effect of natural minerals, i.e., 'hwangto' in concrete at elevated temperatures. The mechanism of such concrete at elevated temperatures is shown in Figure 13, as presented by Kim et al (2023).…”

“…Kim et al (2023) evaluated the effect of natural minerals, i.e., 'hwangto' in concrete at elevated temperatures. The mechanism of such concrete at elevated temperatures is shown in Figure 13, as presented by Kim et al (2023). Frontiers in Materials frontiersin.org…”

Review of Residual Mechanical Properties of Concrete Mixed with Different Admixtures at High Temperatures

“…Thus, changes in the chemical and mechanical properties of concrete exposed to high temperatures have continuously drawn attention.Recently, in response to global warming, various efforts have been made to reduce emissions from the cement manufacturing process, which involves high carbon dioxide emissions. Studies have been conducted on the utilization of industrial byproducts or solid waste as replacement materials for cement [4][5][6]. As for the replacement materials, several studies have investigated fly ash (FA), ground granulated blast furnace slag (GGBFS), and metakaolin (MK) as admixtures [7][8][9].…”