Mechanism analysis on tensile fracture properties of heterogeneous BFLAC at cryogenic temperature: Experimental investigation and mesoscale simulation

Abstract

This study aims to investigate the tensile failure behaviours and corresponding fracture mechanisms of basalt fiber reinforced lightweight-aggregate concrete (BFLAC) at various temperatures via a comprehensive cryogenic tests and mesoscale simulations, with a special focus on the quantitative effects of cryogenic temperature and fiber volume fraction. Firstly, Macro- and micro-scale split-tensile tests of BFLAC with fiber volume fractions of 0.0–0.3 % at 20∼-90 °C were conducted. Secondly, a two-steps sequentially thermo-mechanical coupled meso-scale analysis approach with explicit modelling of fibers and pore ice was developed to simulate the corresponding direct-tensile failures of BFLAC with more fiber volume fractions. The results show that as the temperature falls from 20 °C to −90 °C, the dominant action mechanism of basalt fibers changes from Mode-1 (pull-out of fibers) to Mode-2 (rupture of fibers) due to the ice formation and the interactions between meso-components. Tensile strengths of BFLAC present a significant low-temperature enhancing effect, with a maximum increase of 90 % for direct-tensile strength while 104 % for split-tensile strength. Besides, as the temperature drops, although a larger proportion of fibers are in a low bridging stress state and a smaller proportion reach yield stress for rupture, the average fiber stress increases and the utilization degree of fibers with more stresses transferred improves, which results in that the fiber reinforcement effect is strengthened. Finally, based on experimental and numerical results, the quantitative relationships between split-tensile and direct-tensile strengths at different cryogenic temperatures were given. The present research results can better understand the cryogenic mechanical properties of BFLAC, which have important reference value for its extensive promotions and applications in engineering structures exposed to extreme low-temperature environments.