Application Of Steel Fiber Recycled Concrete In Pavement Engineering

Under the background of continuous and in-depth development of China's transportation infrastructure,a great quantity of low-grade cement concrete highway and bridge facilities no longer meet the actual needs and need to be renovated or dismantled for reconstruction,which results in a large amount of waste concrete construction waste.Handling the recycling of construction waste is not only helpful to the protection of natural resources,but also of great significance to the construction of the whole ecological environment.Based on these aspects,this thesis selects the actual construction waste of cement concrete pavement in Anhui Province,selects recycled aggregate,prepares recycled aggregate concrete and steel fiber recycled aggregate concrete with different properties,and studies the influence of various parameters on the working and mechanical properties of recycled concrete.Specific research contents include the following:(1)The basic properties of recycled aggregate are studied by using traditional crushing method and screening technology.The test shows that compared with natural aggregate,due to a loose old mortar layer attached to the surface of recycled aggregate,the performance parameters such as water absorption rate,crushing value and micropowder content increase significantly,while the apparent density of recycled aggregate shows a downward trend.According to the existing research results,the characteristics and defects of the microstructure of the recycled aggregate under the mass production are summarized.(2)The working and mechanical properties of recycled aggregate concrete with different proportion are studied.The parameters are water cement ratio(0.45,0.50 and0.55)and replacement rate of recycled coarse aggregate(0%,20%,40%,60%,80%and100%).The test results show that the slump and compressive strength of concrete decrease with the increase of replacement rate,while the splitting tensile strength and flexural strength decrease with the increase of replacement rate.(3)The working and mechanical properties of recycled aggregate concrete with different proportion of steel fiber are studied.The research parameters include different content of steel fiber(0%,0.5%and 1.0%)and different replacement rate of recycled aggregate(0%,20%,40%,60%,80%and 100%).The test results show that with the increase of volume fraction of steel fiber,the compressive strength,splitting tensile strength and flexural strength of steel fiber recycled concrete increase,but the slump decreases.Through the comparative analysis of the economic benefits of 1 m~3 natural aggregate concrete,recycled aggregate concrete and steel fiber recycled aggregate concrete,it is found that the cost of recycled aggregate concrete is the lowest,and the cost of steel fiber recycled concrete is slightly higher than that of natural aggregate concrete.But under comprehensive consideration,steel fiber recycled concrete has a good application prospect.(4)The application of steel fiber recycled concrete in pavement engineering is studied.It is found that the mechanical properties,appearance and construction quality of the steel fiber recycled concrete meet the requirements of the actual project.In terms of economic benefits,although the direct cost of steel fiber recycled concrete has increased,the indirect environmental protection cost has been saved,and the comprehensive effect is better than the direct use of fresh concrete.The successful application of this project has guidance and reference value for similar projects.