Preparation,Property Analysis And Waterproof Treatment Of Ultra-light Foam Concrete

As a lightweight porous material,ultra-light foam concrete(ULFC)has excellent properties such as thermal insulation,sound absorption,energy dissipation and shock absorption.When used in prefabricated insulation wall as the insulation sandwich,it can not only reduce the weight of buildings and save building materials,but also effectively slow down the loss of indoor heat in winter and the infiltration of outdoor heat in summer,thus reducing energy consumption.The high-belite sulphoaluminate cement(HBSC)has the properties of fast setting,fast hardening,early strength,high strength,low shrinkage,micro-expansion and crack resistance.In this paper,HBSC was selected as the main binder to prepare HBSC-based ULFC(UHBFC).Firstly,the orthogonal experiment was used to explore the effect of different foaming schemes on the microstructure and physical properties of UHBFC,and the mix proportion of UHBFC was further optimized based on the optimized foaming scheme.Then the influences of the partial replacement of HBSC with different grades of fly ash(FA)on the microstructure,physical properties and shrinkages(?s)of UHBFC were investigated.At last,the waterproof treatment of UHBFC was carried out,and the differences of waterproof effect of different water repellents on UHBFC were compared.The main conclusions in this paper are as follows:(1)The plant protein foaming agent(PPFA)with the dilution ratio of 1:30 and the valve angles of foaming machine suction(?)of 60° is the most suitable foaming scheme to prepare UHBFC,among which the ? has the most significant influence on the physical properties of UHBFC.The pore structures of UHBFC prepared by PPFA and animal protein foaming agent are superior than that prepared by polymer compound foaming agent,especially UHBFC prepared by PPFA has the highest specific strength(fss)and the lowest volumetric water absorption(WV),and has lower thermal conductivity(kc)simultaneously.(2)The optimal mix proportion to prepare UHBFC is obtained by orthogonal range and variance analysis,namely the FA dosage,water to binder ratio,foam dosage,and superplasticizer is 10%,0.4,15%,and 0.5%,respectively.After verification,theUHBFC with the dry density(?d)of 315 kg/m3,fcu of 0.52 MPa and thermal conductivity(kc)of 0.0793 W/m·k is obtained by using the obtained optimal mix proportion,which better meets the performance requirements of prefabricated insulation wall materials.According to the economic analysis,the total cost of preparing 1 m3 UHBFC meeting the performance requirements is ?325.2,which saves about ?20compared with preparing 1 m3 Portland cement(PC)based ULFC(UPCFC)with the same performance.(3)The doped all three grades of FA can reduce ?d and kc of UHBFC to some extent,FA dosage should not exceed 15%,otherwise the specific strength(fss)and tensile bond strength(fb)of UHBFC will be significantly reduced.The fss and fb of UHBFC doped with Grade-I and Grade-II FA are higher than that doped with Grade-III FA.Moreover,the doped Grade-I and Grade-II FA effectively improve the pore structure of UHBFC,reduce the connecting pores and make UHBFC pore wall structure more compact.The ?ss of UHBFC doped with Grade-I and Grade-II FA are lower than that doped with Grade-III FA,when the dosage of Grade-II FA is 15%,the 672 h ?s of UHBFC is only 2.930 mm/m,which is still far less than the UPCFC at the same ?d degree.(4)The calcium stearate has the best waterproof effect among the four types of powdery water repellents,and the 72 h volumetric water absorption(WV)and strength loss rate after water absorption can be reduced to 23.6% and 2%,respectively.Among the two types of liquid water repellents,the waterproof effect of hydrogenated silicone oil(HSO)is superior than that of methyl polysiloxane resin.And the WV of UHBFC treated by soaked method is lower than that by surface coating method.When using HSO doped with KH550 to treat UHBFC by using surface coating method,the corresponding 72 h WV of UHBFC is 5.8%,and its curing rate is only 8.2%.Therefore,it is suitable to choose this scheme for UHBFC waterproof treatment,which can well meet the waterproof and durable effect of prefabricated insulation panels.