Mechanical Properties Of Recycled High-strength Concrete Under Static And Impact Loading

With the acceleration of urbanization,the pollution of production and living in cities,especially the industrial "three wastes",disturb and destroy the environment and ecology of the area.The ecological system of the city is becoming very fragile.The problem of construction waste has become more and more serious.The emergence of recycled concrete technology has solved the problem of waste concrete recycling and alleviated environmental pollution.With the expansion of the scope of recycled concrete,the demand for recycled concrete will be higher and higher.The research on recycled high-strength concrete will be more and more extensive.Many research achievements have been made for the study of recycled high strength concrete,but there are few achievements in the study of the performance of the recycled high strength concrete under the impact and explosion of the high strength concrete.In this paper,the material performance test of nickel iron slag in cement is carried out,and then the static test is carried out on the recycled high strength concrete with nickel slag,and the impact resistance performance of the regenerated high strength concrete is studied by the separation Hopki pressure rod device.The specific work is as follows:(1)A total of 69 sets of cement sand samples containing nickel iron slag(a total of 216 specimens)were tested.The influence of nickel iron slag content on cement performance,compressive strength and flexural strength was studied.The test results show that the stability of cement is qualified after adding Ni Fe slag.For cement mortar specimens,with the increase of the content of nickel iron slag,the standard consistency water consumption and setting time are increasing and the setting time increases rapidly and then rapidly.Under the condition of single nickel iron slag,the compressive strength and flexural strength of the cement mortar with nickel iron slag with age of 3 day are in a small fluctuation with the increase of the content of nickel iron slag.The compressive strength and flexural strength of cement mortar specimens of 7 day and 28 d age decreased with the increase of nickel iron slag content.With the age of 28 day,with the age of adding nickel iron slag and silica fume in cement mortar specimens,the strength of the cement mortar specimens is much greater than that of single mixing with the increase of the mixture of nickel iron slag.The degree of degree growth showed a downward trend.Compared with macroscopic view,the microstructure of cement mortar samples was studied by scanning electron microscope,and the influence of nickel iron slag on cement mortar samples was studied.The compressive strength and flexural strength of the cement mortar specimens are maximum when the strength of the specimens is 20%,and the ratio of the nickel iron slag to the silica fume is 2:1.Under the same mixture ratio,the compressive strength of cement bonded sand samples with nickel iron slag is greater than that of cement mortar with fly ash.(2)A total of 60 specimens of recycled high-strength concrete were tested.The basic physical properties of coarse aggregate were measured,and the material properties between recycled coarse aggregate and natural coarse aggregate were compared.The effects of recycled coarse aggregate replacement ratio and basalt fiber content on compressive strength,flexural strength,splitting strength' and elastic modulus of recycled high-strength concrete were studied.The test results show that the concrete slump,compressive strength and modulus of elasticity decrease with the increase of the replacement rate of recycled coarse aggregate,and with the increase of basalt fiber content,the flexural strength,splitting strength and modulus of elasticity of concrete increase first and then descend,but the compressive strength of concrete is reduced.The influence of strength is small.(3)20 groups of recycled high-strength concrete specimens were subjected to impact compression test.The effects of strain rate and recycled coarse aggregate replacement rate on dynamic compressive strength,peak strain,toughness index and relative toughness of recycled high-strength concrete were studied.The results show that with the increase of strain rate,the dynamic compressive strength,peak strain,toughness index and relative toughness of concrete specimens are improved,and with the increase of recycled coarse aggregate content,the peak strain of concrete specimen is improved but the dynamic compressive strength shows a downward trend.The relationship between dynamic magnification factor(dynamic compressive strength)and strain rate of recycled high-strength concrete under impact load is fitted by least square method.