| The coarse and fine aggregate is obtained by crushing and screening of waste concrete.The crushing loss value is large,the firmness is damaged,and there are a large number of micro cracks in the interior,which restrict it cannot directly replace natural sand to prepare high strength concrete.Therefore,the preparation of low-strength recycled concrete with recycled aggregate is an innovative measure for its functional utilization.Foam concrete has the characteristics of light weight,good thermal performance,sound insulation and fire resistance,low elastic damping and environmental protection.In this paper,cement and recycled aggregate are used to prepare non-autoclaved foamed concrete under normal temperature and cold water conditions under the action of potassium permanganate as an activator through chemical foaming process,which can replace aerated concrete blocks for filling the inner and outer walls of high-rise frame structures.Recycled powder has low activity,complex source of composition and high water absorption.Replacing part of cement with recycled powder will lead to great loss of concrete strength.Polyaluminum chloride(PAC)waste residue,as the waste produced by the production of water treatment agent PAC,has potential pozzolanic activity,and can be used as mineral admixtures to replace part of cement-based materials.It not only reduces the pollution to the environment,but also effectively solves the problem of random stacking of construction waste.The recycled aggregate non-autoclaved foamed concrete mixed with PAC waste residue studied in this paper is used as an extension product of recycled foam concrete to further reduce the economic cost.In this paper,relevant experimental studies are carried out,and the main research results are as follows:(1)The foaming agent content has the most significant effect on the performance of recycled aggregate non-steam curing foamed concrete.When the content increased from 3%to 6%,the 28-day compressive strength decreased by 1.42MPa,and the thermal conductivity decreased by 0.014W/(m·K).The three factors in the range of dosage studied in this paper have no obvious effect on reducing the thermal conductivity,so the determination of the benchmark mix proportion is mainly based on the strength index.Through the comprehensive analysis of strength and thermal conductivity,it is concluded that the best combination of four influencing factors is 3%foaming agent content and 1%foam stabilizer content.The dosage of activator is 0.08%and the dosage of PAC residue is 10%.(2)The thermal conductivity of recycled aggregate non-autoclaved foamed concrete with PAC slag decreases with the decrease of dry density.(3)The dosage of PAC waste residue has a great influence on the compressive strength of recycled aggregate non-autoclaved foamed concrete,and has the most obvious influence on the early compressive strength.Appropriate amount of PAC waste will reduce the loss rate of splitting tensile strength at the later stage of the specimen.PAC waste residue has great influence on early flexural strength.(4)When the content of PAC waste residue is less than 20%,the dry density and thermal conductivity of recycled aggregate non-autoclaved foamed concrete decrease gradually with the increase of waste residue content.When the content is more than20%,the dry density and thermal conductivity increase rapidly.(5)When the PAC waste slag content is 20%,the performance of recycled aggregate non-autoclaved foamed concrete is the best.The 28-day compressive strength is 3.1MPa,the 28-day splitting tensile strength is 1.04MPa,the 28-day flexural strength is 0.76MPa,the thermal conductivity is 0.169W/(m·K),and the dry density is 670kg/m~3,which meets the requirements of relevant specifications.Compared with autoclaved aerated concrete blocks commonly used in high-rise building frame structure infill walls,they are close in strength and thermal insulation performance,and have good lightweight thermal insulation performance. |
PDF Full Text Request