The paper presents the results of experimental studies on the strength and deformations of lightweight concrete, mortar matrix and hardened cement paste under triaxial compression. Tests on samples were carried out using short-term triaxial proportional σ1 > σ2 = σ3 loading (i.e. axial compression + lateral hydrostatic pressure). During the loading, the ratio of the main stresses (both axial and lateral) was kept constant up to the end of tests. The experimental studies were carried out for different low ratios of σ2/σ1. A theoretical estimation has been discussed to approximate experimental results and prediction of triaxial strength values for different types of lightweight concrete. An estimation of the confining pressure parameter K has been done for the used mode of loading.

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.

The paper analyzes the results of experimental studies of the creep of light concrete and the influence of various factors on it. A method for determining the boundary of linear creep of expanded clay concrete has been developed. Experimental studies have been carried out to determine the boundary of linear creep. Experimental creep data and the kinetics of the change in the creep measure of expanded clay concrete over time under axial compression at different levels of long–term load (0.2 - 0.7)Rb are obtained. The limiting values of the relative creep deformation and shrinkage of expanded clay concrete are determined. Empirical formulas for determining and describing the relative deformation of the nonlinear creep of expanded clay concrete, measures of the linear creep of expanded clay concrete under axial tension and compression (if there are no direct experimental data), and the nature of the change are proposed λ(t;τ1)═Cbt(t;τ1)/(t;τ1), depending on (t;τ1) according to the linear law at each site, the nature of the influence of previous loading on the strength and modulus of elasticity of concrete, the limit values of the relative creep deformation and shrinkage of expanded clay concrete.