Study on Mechanical Properties of Basalt Fiber-Reinforced Concrete with High Content of Stone Powder at High Temperatures

Abstract

Concrete materials are an important part of global structure, and their fire resistance directly affects the safety of buildings and tunnels. In this study, basalt fiber was used to reinforce concrete with high content of stone powder in order to enhance its high-temperature performance. The mechanical properties and ultrasonic characteristics at different temperatures were studied using the cube compressive strength test and nonlinear ultrasonic test. The results indicated that the addition of basalt fiber in specimens improved their compressive strength; however, this strength did not continuously increase with increases in the fiber length and fiber content, and the optimal values for fiber length and fiber content were determined to be 12 mm and 1 kg/m3 at 600°C, respectively. With increases in temperature, the unconfined compressive strength increased first and then decreased. When the temperature was 400°C, the unconfined compressive strength of the specimens reached their highest values and then decreased. When the temperature was 400°C and 600°C, the strength of the stone powder concrete with fiber was higher than that without fiber, which shows that fiber can improve the mechanical properties of concrete at high temperatures. Based on the Box-Behnken design (BBD) method, the unconfined compressive strength response regression model of basalt fiber-reinforced concrete with high content of stone powder, which follows parameters including fiber content, fiber length, and temperature at high-temperature environments, was established, and it was found that the interaction of fiber content, fiber length, and the temperature was significant based on multifactor interaction analysis. The analysis of ultrasonic signals based on the S transform showed that, with increases in temperature, the amplitudes of the acoustic response signals, the corresponding frequency spectrum, and the time-frequency spectrum were clearly reduced. At the same temperature, the amplitudes of the acoustic response signals of different concrete testing blocks did not change much and remained at the same level.

Thermal properties, microstructure analysis, and environmental benefits of basalt fiber reinforced concrete

“…This shows that if the fiber content is too high, good results cannot be achieved. 54 The study also found that the strength of the control concrete was about 70.7% MPa, while the strength of the concrete with 0.25% BF was 71.3% MPa. Because of this, BF reinforced concrete keeps its strength longer than control concrete.…”

“…At 400°C, the CS of concrete without fiber and with fiber samples improved by 30% and 19%, correspondingly as compared to the concrete at 25°C. 54 The explanation for this is that some of the free and capillary water in the concrete evaporates in a high-temperature condition. This creates a high-temperature steam curing atmosphere that speeds up the cement's hydration process and makes the concrete stronger.…”