Experimental study and mechanism analysis on static and dynamic mechanical properties of BFLAC at low temperatures

This paper conducted comprehensive axial compressive and splitting-tensile tests to investigate the static and dynamic mechanical properties of basalt fibre reinforced lightweight-aggregate concrete (BFLAC) with fibre volume fractions $V_f$ of 0.0∼0.3% at the temperatures ranging from 20 °C to −90 °C, with a special focus on the microscopic mechanism analysis and quantitative discussion of low-temperature enhancement effect, strain rate effect and fibre reinforcement effect. Test results show that the splitting-tensile strength, compressive strength, and elastic modulus of lightweight-aggregate concrete (LAC) perform an apparent low-temperature enhancement effect and this enhancement effect can be strengthened by the addition of basalt fibres. More basalt fibres reach the tensile failure strength and undergo rupture failure (Mode-2), resulting in the strain rate effect of BFLAC is slightly more significant than that of LAC; but the influence of low temperature on strain rate effect is mild. The incorporation of 0.3%$V_f$ basalt fibres in LAC can bring at least a 20% increase in nominal strengths, showing an significant fibre reinforcement effect which can be enhanced (with maximum increase of 45.6%) as the temperature drops. Based on test results, the relationships between compressive and splitting-tensile strengths were discussed, and the empirical prediction formulas for predicting the static and dynamic mechanical properties of BFLAC at low temperatures were proposed. Research results of this paper can provide reference for mechanical performance calculation and engineering applications of BFLAC in the low-temperature environment.