Preparation And Properties Of Recycled Micropowder Foam Concrete

The construction waste is piled up like a mountain,the problem of random stacking and landfill of waste concrete is everywhere,which seriously affects the environmental health.However,waste concrete has the advantages of being used as recycled aggregate,therefore,many scholars at home and abroad have conducted a lot of research and development on it,Using recycled fine powder to prepare foam concrete and apply it to road engineering research,although there are many researches and applications in other provinces of China,there is no successful engineering application experience due to the special environment and climate in Qinghai Tibet Plateau.On the basis of analyzing the particle size,activity and hydration performance parameters of regenerated micropowder,the influence of water binder ratio,substitution rate of micro powder,foaming agent,additive(stabilizer,superplasticizer,early strength agent)on the basic performance index of recycled fine powder foam concrete was studied.The orthogonal experimental design for finding the best mix proportion of the recycled aggregate foam concrete is studied.The thermal analysis of the recycled micro powder foam concrete insulation system,EPS board insulation system and gravel layer(embankment packing)thermal insulation system is studied.The main conclusions are as follows:(1)the optimum dosage of hydroxypropyl methyl cellulose ether(HPMC)is 0.4% of the foaming agent solution diluted by 1:50,and the density of the foam is 59kg/m3.(2)the basic content of the foaming agent system ranges from 0.80 to 0.92 of the volume of recycled fine powder foam concrete,the basic range of the replacement rate of the recycled fine powder is 15% to 30%,the basic range of the water binder ratio is 0.39 to 0.45,the basic content of the water reducing agent is 0.2% ? 0.4% of the cementing material quality,and the basic dosage of calcium formate(early strength agent)is 0.5% ? 1% of the cementing material quality.(3)for the recycled micro powder foam concrete mixed with recycled micro powder,foaming agent,stabilizer,water reducing agent and early strength agent,the optimum experimental conditions were found by orthogonal test: the substitution rate of micro powder was 15%,the water binder ratio was 0.41,the amount of foaming agent 0.88 V,the dosage of water reducer and the calcium content of calcium formate were 0.83%.The main performance indexes of the recycled micro powder foam concrete prepared by this mixture ratio are: 28 d compressive strength 3.87 Mpa,dry density 485kg/m3,water absorption 23.4%,softening coefficient 0.857,thermal conductivity 0.116 W/(m K),15 times freezing thawing strength loss rate 1.5%.(4)ABAQUS software simulation shows that in the frozen soil roadbed insulation system,24 cm thick recycled foam concrete slab and 10 cm thick EPS plate have the same thermal insulation performance,which is equivalent to the heat preservation effect of gravel layer with 129 cm thickness.