Study On Recycled Fine Aggregate Aerated Concrete

Waste concrete is one of the largest building wastes in China at present.A large number of waste concrete stacking and landfill not only occupy a large amount of land and space,but also cause serious pollution to air,soil and underground water.In this paper,waste concrete is used as raw material to prepare the recycled fine aggregate with a particle size of 4.75 mm after crushing and sieving.Then,the recycled fine aggregate is added to the aerated concrete to prepare recycled fine aggregate aerated concrete with lightweight,thermal insulation,sound insulation and high fire resistance.It is in line with the energy conservation and emission reduction policies that China is currently advocating,and it is of great significance for environmental protection and sustainable development of the construction industry.The main results of this paper are as follows:In this paper,the compression strength of aerated concrete is studied from four factors,such as water-binder ratio,foaming agent content,foam stabilizer content,and water reducer content.The results show that the compressive strength of aerated concrete is the best when the amount of foaming agent is 0.8%,the water-binder ratio is 0.5,the dosage of foam stabilizer is 0.5%,and the amount of water reducer is 0.9%.On the basis of the standard mix ratio,the effect of recycled fine aggregate on compressive strength of aerated concrete is studied by changing the amount,source and particle size of recycled fine aggregate.The results show that the compressive strength of the aerated concrete with recycled fine aggregate is reduced,and the dry density decreases firstly and then increases;The source of recycled fine aggregate has little effect on the compressive strength of the aerated concrete;The larger the particle size of the recycled fine aggregate,the greater the ratio of strength to mass of the aerated concrete.Based on the previous experimental results,the effects of fly ash,blast furnace slag,silica fume and polypropylene fiber on the compressive strength of aerated concrete are studied by orthogonal tests.The results show that silica fume has the greatest influence on the compressive strength of aerated concrete,and the addition of silica fume and fly ash can increase its strength;The strength and density of aerated concrete decrease with the addition of blast furnace slag;Polypropylene fiber has little effect on strength;The optimum ratio is silica fume 10%,blast furnace slag15%,fly ash 10%,polypropylene fiber 0.1%.Finally,the fluidity,drying shrinkage,water absorption and microstructure of aerated concrete were studied.The results show that the fluidity is reduced after adding recycled fine aggregate into the aerated concrete;The fluidity can be improved by adding water reducing agent and increasing water-binder ratio;The drying shrinkage of aerated concrete decreases obviously after adding recycled fine aggregate;With the incorporation of recycled fine aggregates,the uniformity of the pores of aerated concrete deteriorates,the number of inter-connective pores is increasing.By incorporating mineral admixtures,the pore structure of the aerated concrete and the microscopic structure of the pore wall can be improved,so as to improve its macroscopic properties.