Uniaxial Compression Tests Of Self-compacting Concrete After Freeze-thaw Cycles

The freeze-thaw cycle has certain damage to the structure and function of concrete,especially in the structure with more water content.At present,the research on self-compacting concrete after freeze-thaw is mostly from the microscopic point of view,such as adding air entraining agent,mineral admixture and so on.Most of the studies on mechanical properties of concrete after freeze-thaw are about the relationship between cubic compressive strength,flexural strength,splitting tensile strength and freeze-thaw cycles,but few studies on stress-strain curves of components after freeze-thaw,and the application of self-compacting concrete is more and more extensive,so the research on stress-strain relationship of self-compacting concrete after freeze-thaw has high scientific research value and significance.The main works of this paper is as follows:?1?Through testing the working performance of self-compacting concrete mixtures,including three test methods including slump expansion and T₅₀₀,J-ring and L-type instrument.?2?The prism specimens of C40 and C70 self-compacting concrete of 100 mm?100 mm?400 mm were poured,and the mass and dynamic elastic modulus of the specimens were measured after freezing and thawing cycles.The self-compacting concrete cube blocks of C40and C70 were poured and divided into 150 mm and 100 mm sizes.The cube compressive strength was measured under different freeze-thaw cycles.C40 and C70 self-compacting concrete 150 mm?150 mm?300 mm standard prism specimens were poured,and uniaxial compression tests were carried out on standard prism specimens under different freeze-thaw cycles.The main conclusions of this paper are as follows:?1?During 125 freeze-thaw cycles,the relative dynamic modulus of elasticity of C40self-compacting concrete decreases gradually with the increase of freeze-thaw cycles,and the mass loss rate increases in general,while the mass and relative dynamic modulus of C70self-compacting concrete increase after 400 freeze-thaw cycles.?2?In 150 freeze-thaw cycles,except that the compressive strength of C70 standard cube fluctuates up and down at 79 MPa,the compressive strength of C40 standard cube block and100 mm cube block of two strength grades decrease with the increase of freeze-thaw cycles,and the decline rate of 100 mm cube block is faster than that of standard cube block.?3?With the increase of freeze-thaw cycles,the earlier the rise slope of the stress-strain curve of the standard prism of C40 self-compacting concrete changes,the greater the dispersion of the descending section,the gentler the curve gradually,the higher the relative peak strain and the lower the elastic modulus.The curve of C70 self-compacting concrete changes obviously only after 200 freeze-thaw cycles.The peak strain fluctuates up and down at 2250??.The modulus of elasticity increases slightly at first and then decreases slightly.The peak stress of prism with two kinds of strength decreases with the increase of freeze-thaw cycles.Under the same freeze-thaw cycles,the strength of prism decreases faster than that of standard cube.?4?By fitting the stress-strain curve of the self-compacting concrete Guo Zhenhai,the fitting formulas of curve rising parameter“a”and freeze-thaw cycle number“n”of the self-compacting concrete after freeze-thaw are obtained.