Preparation Of Carbonated Steel Slag Aggregates And Planting Concretes

Steel slag is the waste discharged from steelmaking process,which not only has large discharge capacity,but also has poor stability.It cannot be directly used in civil engineering,and a large number of land is occupied also polluting environment.So that steel slag products can obtain strength quickly and autoclave stability is qualified.In addition,the consumption of natural aggregate resources and the ecological damage and environmental pollution caused by dust and noise in the process of quarrying are becoming more and more serious.The problems of urban ecological environment caused by the barrier of traditional concrete to the circulation of urban groundwater and low vegetation coverage also need to be solved urgently.In this paper,carbonated steel slag artificial aggregate is prepared to realize the resource utilization of steel slag,which can not only solve the problem of steel slag storage,but also replace the consumption of natural aggregate.On the other hand,carbonation treatment can make the basicity of steel slag tend to be neutral,which has great potential for the preparation of biocompatible planting concrete.In this paper,based on the domestic research status and the structural characteristics of carbonated steel slag planting concrete,the effects of carbonated steel slag artificial aggregate prepared by two different processes and carbonation on the properties of steel slag planting concrete are studied emphatically,which can provide reference for engineering application.The test results show that:(1)The bulk density of crushed carbonated steel slag aggregate is 987.6 kg/m~3,less than1000 kg/m~3 belongs to light aggregate.The water absorption rate is 15%,which meets the requirement that the water absorption rate of light aggregate should not exceed 22%.The cubic compressive strength of carbonated steel slag is 32.5 MPa,the crushing index is 7%,less than10%,which belongs to grade I aggregate quality.(2)During the preparation of spherical carbonated steel slag aggregate,attention should be paid to the compacting time of cold bonding pelleting.When the compacting time is 5minutes,the water absorption before carbonation is 14.8%,and the strength after carbonation is 6.1 MPa,which reaches 41%of the strength of natural gravel with the same particle size,water absorption decreased to 11.2%.In contrast,the carbonated spherical aggregate with 10minutes compacting time also has higher carbonation degree and strength,and water absorption has been reduced,but there are still fine lines after autoclaving.Considering comprehensively,the optimum time for preparing carbonated spherical aggregate by this process is 5-10 minutes,and the longest time is not more than 10 minutes.(3)The optimum water-binder ratios of carbonated steel slag planting concretes with 5-10mm single-particle crushing carbonated steel slag aggregate and spherical carbonated steel slag aggregate formed by step by step stirring and forming are 0.21 and 0.20 respectively,and the effective void ratios are 27.9%and 28.3%,respectively.After 2 days of carbonation treatment,the highest compressive strength is 6.4 MPa and 4.7 MPa,respectively.The highest compressive strength of carbonated steel slag planting concrete formed with natural aggregate is 11.6 MPa.And the pH value of the three kinds of planting concretes are stable at about 11.7,and the stability is qualified.(4)In the planting test,three kinds of carbonated steel slag planting concretes with different aggregates all have good biocompatibility.Plants grow well in them,and the roots can pass through concrete structures to reach the soil,also there is no plant necrosis due to unsuitable environment.