Experimental Research On Strength And Fracture Properties Of Hydraulic Concrete After Three-factor Deterioration

The durability of the concrete is always the intense research for the scholars at home and abroad. The cracks are very normal for the hydraulic mess concrete when they were cast-in-place For the severe environment the hydraulic concrete stays,when they under normal service condition, expect the carbonization, the water will get into the interior of the concrete through the cracks, and lead to the chemical corrosion of the concrete. Besides, in the severe cold area they will also suffer freeze thawing cycle. It’s easily aggravate the cracks of the structure and even lead to the failure of the engineering when they under three-factor deterioration. Therefore, the research on the changing patterns of strength and fracture properties of the hydraulic concrete under the carbonization, dry-wet cycling of sulfate and the freezing-thawing cycle has big significance.Based on this, this paper mainly study the mechanical properties( include compressive strength, splitting tensile strength and fracture property)of the hydraulic concrete under three factor deterioration which are carbonization(include 7 days, 14 days and 28 days), dry-wet cycling of sulfate(include 15 times, 30 times and 60times) and freezing-thawing cycle(include 25 times, 50 times and 75 times).Through compared with the control group which are without deterioration, the rules and internal influence mechanism of the deterioration were analyzed. The main results are as follows:1.Under three-factor deterioration, the compressive strength have no significant changes.The short-term carbonization can improve the compressive strength, but long-term will lead the oppsite result. The compressive strength will reduced obviously after long-trem freezing-thawing cycle. The variation trend of the compressive strength is similar to the splitting tensile strength. But the bad effects for the splitting tensile strength is more bigger than the compressive strength.The splitting tensile strength will increased first and then decreased with the increased in dry-wet cycling.And the damage of the freezing-thawing for the splitting tensile strength is the biggest.2.The mass loss rate of the specimen is very small after freezing-thawing cycle.There is no correspondence between the mass loss rate and relative dynamic modulus of elasticity.The composite deterioration make the part of the coarse aggregate and concrete mortar stripped,weakened the cohesive force, carrying capacity and resistance ability for crack propagation of the concrete materials.3.The influence under composite deterioration to the hydraulic concrete’s fracture properties is more bigger than the compressive strength and splitting tensile strength. Half of the prism specimens appeared new crackle and even break off after freezing-thawing cycle. In the three deteriorations, the freezing-thawing’s influence for the fracture properties is the biggest, the macroscopic crack aggravated the concrete’s freezing-thawing damage, lead the vicious spiral of the specimen under deterioration process, and finally result the depress of the initiation toughness and unstable toughness. The deterioration depressed the concrete’s brittleness, and improved the specimen’s toughness, make it have a period of stable expand after achieving the unstable load.