Study On Preparation And Properties Of Green Concrete

With the development of social economy,The urban construction continues to expand.At the same time,large-scale construction has produced a large amount of construction waste such as waste concrete,which has brought heavy pressure to the environment and the shortage of natural sand and gravel resources.Therefore,the use of waste concrete to produce recycled aggregates and for the preparation of green concrete has broad prospects.In this paper,the waste concrete of the mixing station is used as raw material,and the recycled coarse aggregate with the particle size of 5-20 mm is obtained through the processes of crushing,sieving,treatment,particle shaping and grading adjustment.And we studied the related properties of recycled coarse aggregate.The mixing design method and design process of green concrete prepared by using recycled coarse aggregate were discussed.The effect of recycled aggregate on the work performance,mechanical properties and microscopic properties of green concrete was studied.The main conclusions of this paper are as follows:(1)Through the process of crushing,sieving,treatment,particle shaping and grading adjustment of the waste concrete in the mixing station,the continuous grading of the recycled coarse aggregate with the particle size of 5-20 mm is obtained,The values of the water absorption rate and crushing index are higher than natural gravel aggregates,and the apparent density is slightly lower than that of natural aggregates.(2)With the increaseing of the replacement rate of recycled coarse aggregate,the slump of green concrete mixed by it gradually decreases,and the effect of water reducer on green concrete is slightly lower than that of natural coarse aggregate concrete,but it can satisfy design work requirements;(3)With the increaseing of the replacement rate of recycled aggregates,the cubic compressive strength,splitting tensile strength and axial compressive strength of 3d and 28 d of green concrete all show a decreasing trend,but can meet the design strength requirements.(4)With the increaseing of the replacement rate of recycled aggregate,the micro-hardness value of the interfacial transition zone of green concrete prepared by recycled aggregates is reduced.There are many microcracks and pores in the interfacial transition zone,and the hydrated calcium silicate diffraction peak also weakened.In short,The green concrete prepared by recycled coarse aggregate is lower than the natural aggregate concrete in terms of workability and mechanical properties.However,if the mix design is reasonable,it can still meet the design requirements.The research results have certain engineering Guiding significance for the reuse of waste concrete.