Experimental Study On Thermal Performance Of Structure Wall With Recycled Brick Aggregate Concrete

The popularization of prefabricated building is the inevitable trend of traditional building transformation in China.Using prefabricated concrete structure as the main form of low-rise building structure in China’s villages and towns can effectively reduce labor force,save energy resources,shorten construction period and improve project quality.Among them,as the main component of prefabricated multi-stores building,structural wall should not only meet the requirements of structural bearing capacity and seismic performance,but also have good thermal insulation performance to improve the living comfort.It is of great significance for the development of prefabricated buildings to study the building materials with excellent thermal performance and strength to meet the performance requirements.In this paper,recycled brick aggregate concrete is used as the wall material of prefabricated multi-stores building structure.Combined with the requirements of building energy conservation and emission reduction in China,thermal performance test of recycled brick aggregate concrete and thermal insulation performance test of recycled brick aggregate concrete structure wall are carried out to study the thermal performance of recycled brick aggregate concrete materials and components.The main contents and conclusions of this paper are as follows,(1)The physical and mechanical properties of recycled brick aggregate,such as particle size distribution,crushing index,apparent density and water absorption,are tested.The physical properties of recycled brick aggregate and suggestions for concrete preparation are obtained.Then,the mix proportion of recycled brick aggregate concrete with strength grade of C25 is designed.According to the laboratory mix proportion of recycled brick aggregate concrete determined in this paper,the 28d cube compressive strength reaches 26.4 MPa,which meets the test requirements.(2)The orthogonal experimental design scheme of recycled brick aggregate concrete is proposed,and the experimental study on thermal performance of recycled brick aggregate concrete is carried out.By using the methods of range analysis and variance analysis,the influence law and significance of net water binder ratio,volume sand ratio,water consumption per unit volume and volume replacement rate of recycled brick aggregate on cube compressive strength,dry density and thermal conductivity of recycled brick aggregate concrete are discussed to explore the relationship between the test indicators.The test results show that:on the whole,there is no correlation between cube compressive strength and thermal conductivity and dry density in the three test indexes,the thermal conductivity of recycled brick aggregate concrete increases with the increase of dry density,and the thermal conductivity of recycled brick aggregate concrete increases by 6.62%with the increase of dry density of 50 kg/m~3.(3)The heat transfer coefficient of recycled brick aggregate concrete structure wall is measured by using the protective hot box method.The total heat flow,thermal resistance,heat transfer coefficient and other thermal parameters are calculated and obtained.The thermal parameters of recycled brick aggregate concrete structure wall are compared with those of other wall block materials,and the thermal performance of recycled brick aggregate concrete structure wall is evaluated.The heat transfer coefficient of the structural wall specimen is calculated by the recommended formula of the current code,and the one-dimensional steady heat transfer process of the wall is analyzed by using the finite element software ANSYS Workbench.The measured value,theoretical calculation value and numerical simulation value are compared and analyzed.The results show that the experimental values of heat transfer coefficient are 2.667 W/(m~2·K)and2.792 W/(m~2·K),and the thermal resistance values are 0.225 m~2·K/W and 0.208 m~2·K/W,respectively.In the thermal test,the influence of reinforcement and other factors on the heat transfer coefficient of the wall specimen is small;the simulation value is basically consistent with the theoretical calculation value,and the heat transfer coefficient obtained from the test is slightly higher than the theoretical calculation value and the simulation value;under the premise of the same thickness,when the recycled brick reinforced concrete is used as the material of the structural wall in the structural design,the calculated value of the heat transfer coefficient is higher than that of the ordinary concrete structural wall It’s down 38%.(4)The influence of different factors on the thermal insulation performance of recycled brick aggregate concrete structure wall was studied by numerical simulation,the results show that:when other factors remain unchanged,the heat transfer coefficient of structural wall decreases linearly with the increase of wall thickness;the influence of environmental temperature condition on the heat transfer coefficient of structural wall is very small,which can be ignored;XPS insulation board is added as the external insulation layer of structural wall After that,the heat transfer coefficient of the wall can be reduced to 0.705 W/(m~2·K),which is reduced by 69.2%,meeting the limit value of the heat transfer coefficient of the external walls of buildings in hot summer and cold winter areas,indicating the feasibility of using recycled brick aggregate concrete structure wall in the external walls of low buildings in rural areas.