Axial compression testing and constitutive model of a novel BF-reinforced ambient-cured LEGC

Abstract

Ambient-cured lightweight expanded polystyrene geopolymer concrete (LEGC) currently undergoes early shrinkage cracking, and the low density of EPS causes segregation during the mixing process, resulting in a significant decrease in the strength of LEGC. To solve the above problems to obtain higher strength LEGC and promote its wide application, uniaxial compression tests and constitutive modeling studies of LEGC with different basalt fiber (BF) lengths (3 mm, 6 mm, 9 mm, 12 mm and 15 mm) reinforced with different expanded polystyrene (EPS) volume contents (10%, 20%, 30% and 40%) were conducted in this study. First, the damage pattern of the specimen was analyzed, and the crack development morphology was analyzed based on the Digital Image Correlation-3D (DIC-3D) technique. Additionally, the mechanism of BF-reinforced of LEGC was analyzed comprehensively at three levels: micromechanical theory, microscopic (scanning electron microscopy, SEM) and mesoscale (computerized tomography, CT). Empirical formulas for peak stress, peak strain, threshold stress, threshold strain and elastic modulus were established based on the stress‒strain curves of the specimens. In addition, the specific form of the damage evolution equation considering the energy dissipation of the specimen was derived from the energy balance principle and basic laws of irreversible thermodynamics based on composite damage theory. Finally, elastic‒plastic damage constitutive models established previously and in this study were compared, and the results showed that the method proposed in this study can better reflect the damage evolution of BF- reinforced LEGC.