Experimental Study On Aggregate Recycling By Crushing Of Waste Concrete

Concrete is the most widely used cementation material in the world.Every year,a large amount of natural gravel aggregate is consumed for the preparation of concrete,which makes the natural aggregate increasingly scarce.At the same time,a large amount of construction wastes,most of which are waste concrete,are produced by the demolition of buildings,road renovation,and natural disaster damage.In order to improve the utilization rate of construction waste resources and solve the problem of gravel aggregate supply,it is one of the important measures to produce high-quality recycled aggregate,which has enormous environmental and economic benefits.Based on the theory of particle impact crushing,this paper set up the experimental platform of coarse aggregate recycling and crushing,and conducted the stripping experiments on waste cement concrete and waste asphalt concrete respectively,and studied the effects of key parameters on the recycling of aggregate.The main research results are as follows:(1)The experimental platform was used to conduct stripping experiment of waste cement concrete,and granite particles and steel grit were used as impact materials.Taking mortar stripping rate,energy consumption ratio,water absorption rate and apparent density of recycled coarse aggregate as the characterization parameters,the paper experimental studied the effects of the key parameters such as impact velocity,impact time and concrete strength on the degree of mortar stripping.The results show that the impact velocity,impact time and concrete strength,as well as the impact material,have a great effect on the degree of mortar stripping.The stripping effect of steel grit is better than that of granite.(2)The experimental platform was used to conduct stripping experiment of waste asphalt concrete,and granite particles and basalt particles were used as impact materials.Taking the stripping rate,energy consumption ratio and asphalt content of recycled coarse aggregate as the evaluation index of old asphalt stripping effect,the paper experimental studied the effecs of impact velocity and impact time on the degree of old asphalt stripping.The results show that the effect of old asphalt stripping is better with the increase of impact speed and impact time.When the impact speed is 55m/s,after 4min of impact,the old asphalt is almost stripped.The stripping effect of basalt is better than that of granite.(3)Recycled fine aggregate was prepared from waste cement concrete.The physical properties of recycled fine aggregate such as density,voidage,water absorption,crushing value,grading and powder content,as well as the ratio of minor axis to major axis,sphericity and particle shape coefficient were detected and analyzed.The research results show that the physical properties of recycled fine aggregate meet the requirements of the corresponding national standards,the particle shape coefficient conforms to the standard technical requirements,and the degree of mortar stripping does not affect the particle shape of recycled fine aggregate.The paper conducted the univariate experimental study on key parameters of two types of waste concrete by using different materials as impact material.The optimal parameters of effective stripping were obtained by comparing evaluation indexes.Furthermore,the feasibility of preparing recycled find aggregate was verified.The work of this paper is provides a new method for preparing high-quality recycled aggregate,and helps to improve the utilization rate of waste concrete,which shows good engineering practical application value.