Research On Thermal Conductivity And Mechanical Properties Of Sandwich Straw Concrete Blocks

Straw as the main product of agriculture in China,the annual output is huge.However,due to the low comprehensive utilization rate of new crop straw production in China,a large number of crop straw are randomly piled up and discarded or burned,which will not only seriously waste resources but also pollute the ecological environment.In order to make better use of straw to save energy and reduce pollution gas emissions,some basic characteristics such as light weight and small thermal conductivity of crop straw are combined with cement,fly ash,slag and other cementing wall materials to make a new type of sandwich straw concrete block.In this paper,the compressible strength test,thermal conductivity test and computer software performance simulation analysis of concrete block are carried out.The results show that the sandwich straw concrete block has the advantages of high compressible strength and good thermal insulation effect.When it is used in building wall structure,it will effectively meet people's pursuit of comfortable life.Sandwich straw concrete block is composed of straw block and concrete.The test and comparison and the software simulation analysis of the sandwich straw concrete blocks made of different materials are carried out,so as to obtain the sandwich straw concrete blocks which can not only meet a certain compressible strength but also play a good thermal insulation effect.1.In this paper,three different cementing materials are selected to prepare concrete.(1)Concrete made of ordinary Portland cement as binder;(2)Concrete made of two kinds of mixed materials,fly ash and ordinary Portland cement,inwhich the amount of fly ash is calculated by 10% replacement rate;(3)Concrete made of slag cement as binder,in which the slag cement is made of Portland cement clinker,fly ash,slag,and stone.The paste was composed of 42%?45%?8%?5%respectively.2.The size of the sandwich straw concrete block is 150 mm × 150 mm × 150 mm in this paper,in which the surface area ratio of the sandwich straw block is 20%,25%,30%,35%,45% respectively.In this experiment,each kind of concrete material is made of three blocks according to different surface area ratios of straw blocks,and a total of 45 sandwich straw concrete blocks are produced.3.This paper carries out compression test on sandwich straw concrete blocks,which are cured for 28 days under standard conditions and conducts statistical analysis of test results.The results show that when the surface area ratio of the straw blocks is 20% and 25%,the concrete blocks of the three materials satisfy the requirements of the compression strength of the wall of C30.When the surface area ratio of the straw is 30%,the slag cement concrete blocks also satisfy the wall compression requirements.When the straw surface area ratio is 35%,40%,and 45%,the measured compression strength is all less than 30 MPa,which does not satisfy the requirements of the wall.4.The therma conductivity of ordinary Portland cement concrete test block is1.2802 W/(m·k).The thermal conductivity of the test block of cement concrete mixed with fly ash is 0.7936 w /(m·k);The thermal conductivity of slag cement concrete test block is 0.7413 w /(m·k);The thermal conductivity of straw block is 0.0813w/(m·k).Based on the thermal conductivity measured,the thermal conductivity of the sandwich straw concrete block composite flat wall is analyzed,and the total thermalconductivity of the sandwich straw concrete block is calculated.Among them,when the proportion of straw surface area is 20%,the total thermal conductivity resistance of sandwich straw slag cement concrete block is 10.012 k /W larger than that of sandwich straw fly ash cement concrete block is 9.363 k /W larger than 6.9%.The total thermal resistance of sandwich straw ordinary Portland cement concrete block is5.842K/W greater than 71%.5.This paper uses ANSYS software to perform steady-state thermal analysis and simulation on sandwich straw concrete blocks and their walls.The results show that the larger the surface area ratio of straw blocks,the better the insulation effect of sandwich straw concrete blocks and walls.When the surface area ratio of straw blocks is the same,the thermal insulation effect of slag cement concrete block walls is better than that of fly ash cement concrete.The increase of block wall is 6.9%,which is 70% higher than that of ordinary Portland cement concrete block wall.