Research On Comprehensive Performance Of Straw Concrete Composite Self Insulation Block

The self-insulation composite block is a kind of small concrete block that is mixed with lightweight aggregate or filled with lightweight insulation material in the hole of the hollow block.The masonry constructed by using self-insulation composite block has self-insulation performance and can achieve the purpose of building energy saving.The research group made use of rice straw,which was pretreated and cold-pressed,and then filled into the concrete hollow block to form a new type of straw concrete self-insulation composite block.Based on the previous research,the structural block type,production technical parameters,and various comprehensive performance parameters of the self-insulation block were studied,which provided theoretical guidance for the actual production of the straw concrete composite self-insulation block.The specific research results are as follows:(1)Based on the early research,combined with literature and production practice,the block type of self-insulation composite block is determined to be single-hole cubic concrete hollow block,the actual size is 190mm×190mm×190mm,the hole is rectangular,the size is 140mm×140mm.In order to determine the material of concrete,ordinary concrete,ceramsite concrete,and foamed concrete,which is common in actual construction,are used as raw materials,and the advantages and disadvantages of the three materials are compared through the compressive strength test,and the concrete material of self-insulation composite block is determined to be ordinary concrete.(2)The technical parameters of the mechanical equipment in the actual production process of the straw brick were preliminarily explored.Through the compressive strength test of straw brick,the maximum external pressure that straw brick can bear in the filling process is 6650N.The static friction coefficient of the contact surface between the straw brick and the mechanical equipment was measured.Through force analysis and static calculation,the minimum pressure required by the mechanical equipment in the actual production process of the straw brick was estimated to be 9.51N.Therefore,the allowable range of external force exerted by mechanical equipment in the production process of straw brick is 9.51N-6650N.(3)According to the requirements of"Self-insulation Composite Concrete Blocks"(JG/T407-2013),the comprehensive properties of self-insulation composite blocks are studied.The apparent density of the self-insulation composite block is 978.22kg/m~3,and the density level is 1000.The mass water absorption rate was 12.2%;The average compressive strength and minimum compressive strength of the self-insulated composite blocks are 5.12MPa and 5.01MPa,The intensity level is MU5.0.The softening coefficient and carbonization coefficient of the self-insulation composite block are 0.94 and 0.91respectively.After 25 freeze-thaw cycles,the appearance quality of the self-insulation composite block is well preserved,with a mass loss rate of 1.62%and a strength loss rate of 8.30%.The water surface drop height of the self-insulation composite block is less than 10mm within 2h,and the anti-seepage performance meets the specification requirements.(4)In this paper,the BBD experiment design method of response surface methodology was used to analyze the effects of straw brick forming density,water content,and the wall thickness of concrete hollow block on the thermal performance of straw-concrete composite self-insulation block,including equivalent thermal conductivity and equivalent heat storage coefficient.The theoretical model of three factors on the thermal performance of self-insulation block was obtained by Design Expert12 software.At the same time,according to the model,it can be seen that the effect of three factors on the equivalent thermal conductivity of self-insulation blocks from large to small is:moisture content>forming density>wall thickness;The influence on the equivalent heat storage coefficient from large to small is moisture content>forming density>wall thickness.(5)The process parameters of the self-insulation composite block were optimized by Design-Expert 12 software.The optimal process parameters of the three factors are obtained as follows:the forming density is 221.34kg/m~3,the moisture content is 8.12%,and the wall thickness of the concrete hollow block is 20mm.Under these conditions,the predicted value of equivalent thermal conductivity of the straw-concrete composite self-insulation block is 0.28W/(m·K),the level is EC30,and the predicted value of equivalent heat storage coefficient is 2.354W/(m~2·K),the level is ES2.It is found that the predicted value obtained by using the model is close to the test result through the comparison of the verification tests,which indicates that the model has high reliability and can guide the actual production of straw-concrete composite self-insulation block.