With the rapid advancement of urban urbanization, a large number of aging buildings that do not conform to urban construction planning have been demolished, and a large number of buildings built have left a lot of construction waste. Although the city’s expansion rate is gratifying, but at the same time the massive concrete waste, the urban environment had a huge impact.[1–3]
The direct waste of construction waste is not only a large waste of sand and cement resources, but also increases the production cost of construction enterprises.[4, 5]
At present, Japan is a country with good application of recycled concrete in the world. Japan is located in an island country with a shortage of soil sand and gravel construction resources and a high degree of recycling of construction waste. Japan's waste concrete is generally unified recycling, by crushing waste into granular solids. In the high temperature environment, concrete particles collide with each other and become powdered solids, which can be used to produce cement or other building core materials.[6–8]
The processing process of concrete waste materials is through the direct high temperature treatment of waste concrete. After heating, screening and separation, the concrete waste becomes a powdered solid. Concrete waste can usually also be used low-temperature cold treatment screening separation process, into recycled powder.[9–12]
Usually, the waste concrete material is reduced to coarse aggregate during the crushing process. The finer concrete powder requires a lot of water to be perfectly integrated with the cement, which easily leads to a sharp increase in the cost of concrete recycling. Excessively fine concrete powder will also reduce the ability of the remade concrete material to withstand gravity. [13, 14]
Concrete recycled materials need to be reasonably classified according to the material properties after crushing, and re-proportioned according to the material properties to ensure that the quality and strength of recycled materials meet the standards, so as to meet the safety of buildings.[15–17]
After cleaning the classified waste concrete, the crushing operation is carried out to screen the parts suitable for concrete reconstruction, and the new concrete is obtained according to the properties of the obtained powder.[18, 19]
Remade concrete materials, due to the powder surface roughness, contains a lot of uneven parts, the surface of the powder wrapped with cement and other impurities, may lead to recycling of concrete materials absorb water quickly.[20–23]
Through life cycle assessment, Zhang [24] and Senthil [25] found that the use of concrete powder is beneficial to environmental protection and resource conservation.
Gutiérrez [26] found that concrete with waste concrete powder has good heat resistance, which may be related to secondary hydration and micro-aggregate effect.
Improving the recycling rate of concrete materials can not only reduce the raw material cost of construction enterprises, but also protect the ring.[27–29]