Comparison of microcrack formation boundaries determined by complex of physical methods with long-term strength of expanded clay concrete under different types of stress state

Abstract

This work aims to experimentally study the strength and strain of expanded clay concrete during short-term and long-term compression and tension under various loading modes. A technique for testing expanded clay concrete under short-term and long-term compression and tension, including the boundaries of microcrack formation by a complex of physical methods (tensometric, ultrasonic pulsed, and acoustic emission), is given. The results of tests of expanded clay concrete under short-term and long-term monotonic loading under compression and tension and low-cycle loading under compression, as well as the boundaries of microcrack formation by a complex of physical methods, are obtained. The boundaries of microcrack formation are compared with the long-term strength of expanded clay concrete under various types of stressed states. Strain diagrams of expanded clay concrete under axial compression and tension, and "ultrasound transmission speed - stress level" and "number of acoustic pulses - stress level" diagrams are also obtained. Empirical formulas are proposed for determining the boundaries of microcracking in expanded clay concrete and the relationship between the level of long-term strength and the time of staying specimens under load in compression and tension. The results allow the formulation of several proposals and clarifications for normative documents to calculate and design lightweight concrete elements and structures.