Study On Mechanical Properties And Freez-thaw Corrosion Of Steel-basalt Hybridfiber Recycled Aggregate Concrete

With the continuous development of the urban-rural integration reform in China,the replacement of old and new houses leads to a large amount of construction waste,which pollutes the environment.The recycling of construction waste is an important way to solve the problem of environmental pollution.As a kind of construction waste,the waste concrete is applied to the concrete specimen again,which saves the natural stone on the one hand and relieves the environmental pressure on the other hand.In this paper,by preparing recycled concrete with different proportions,the mechanical properties of compressive and tensile strength as well as the coupling properties of freeze-thaw corrosion were studied by experimental methods,which provided certain technical support for the engineering application of this kind of concrete.The specimen design includes 1 group of ordinary concrete,1 group of recycled concrete,3 groups of steel fiber recycled concrete with different mixing ratios,3 groups of basalt fiber recycled concrete with different mixing ratios and 9groups of steel-basalt fiber recycled concrete with different mixing ratios.In order to study the mechanical properties of recycled concrete,MTS universal testing machine was used to measure the cube compressive strength,splitting tensile strength and flexural strength of each test block.Through data analysis,the influence of steel fiber and basalt fiber single mixing and mixed mixing on the three mechanical properties of recycled concrete was obtained.The test results show that the strength enhancement effect of single steel fiber is better than that of single basalt fiber,mixed steel fiber and basalt fiber.In the cube compression test,the strength of recycled concrete increased by 13.6%with the addition of 0.9%steel fiber.In the splitting tensile test,the strength of recycled concrete increased by25.8%compared with recycled concrete and 10.7%compared with ordinary concrete with the addition of 1.5%steel fiber.In the flexion resistance test,the strength of recycled concrete increased by 42.1%compared with that of recycled concrete and 30.6%compared with that of ordinary concrete with the addition of 1.2%steel fiber.Based on the mechanical properties test,the freezing-thawing corrosion coupling performance of recycled concrete was further studied.The strength loss rate,mass loss rate and dynamic elastic modulus of each block after 50 and 100 freezing-thawing cycles were measured by freezing-thawing cycle and sulfate coupling test.The effects of single and mixed mixing of steel fiber and basalt fiber on the freezing-resistance of recycled concrete were studied.The test results show that the enhancement effect of steel fiber and basalt fiber on the frost resistance of recycled concrete is better than that of steel fiber and basalt fiber.The quality loss and strength loss of recycled concrete test block with steel fiber 1.5%and basalt content 7.5kg/m~3 are the least.The relative dynamic elastic modulus of the recycled concrete test block with steel fiber content of 1.2%and basalt content of 3.5kg/m~3 decreased the least.