Study On Mechanical And Thermal Properties Of Fiber Reinforced Alkali Slag Cementitious Sandwich Board

Aiming at the problems of inflammable,fragile and easy to fall off inside and outside the wall insulation layer,the sandwich type insulation wall board with straw board inside refractory fiber reinforced alkali slag cementitious material(AASCM)is taken as the entry point.Mechanical properties tests,thermal properties test and refined finite element analysis were carried out to systematically study the influence of key parameters on the mechanical and thermal properties of thermal insulation wall panels,and reveal the optimal ratio,bearing capacity formula and thermal model of thermal insulation wall panels.The specific work is as follows:(1)Study on optimization of AASCM mix ratio was carried out.In view of the shortcomings of AASCM such as easy cracking and poor toughness,this paper uses the methods of mixing fiber,magnesium oxide,expansion agent,other admixtures,changing the solution temperature and so on to improve the material properties.The influences of magnesium oxide content,expansion agent partial replacement of magnesium oxide,admixture content,solution temperature on material strength,drying shrinkage,setting time,hydration products and micromorphology were studied.The results show that compared with expansion agent and other admixtures,Magnesium oxide can bring higher strength to AASCM,and effectively inhibit the dry shrinkage of the material,and the improvement effect increases with the increase of magnesium oxide dosage.Higher solution temperature can make AASCM have higher compressive strength,but the solution cooled to room temperature can make AASCM have higher flexural strength and smaller shrinkage.It can be seen from the microscopic analysis that the high content of magnesium oxide makes the material denser,so that the refractory fiber and the material have good interfacial properties.(2)The bearing capacity of AASCM sandwich plate under axial load was studied.Aiming at the problem of how to coordinate the common force of the two sides of the sandwich plate,this paper conducts axial bearing capacity tests on four different combinations of sandwich plates from the number of connectors and whether there is steel wire mesh,and verifies the test results through ABAQUS simulation analysis.The results show that the connectors can effectively pull the two sides of the page wall together,and the bearing capacity of the sandwich plate increases with the increase of the number of connectors.Under the action of axial load,the failure of sandwich plate is split failure,and the corner part of concrete is crushed and falls off.According to the test results,the calculation formula of the bearing capacity and the coefficient related to the number of connectors are put forward.The steel wire mesh in the sandwich plate has a certain increase in the bearing capacity of 4 connectors,when the use of 6 connectors,the steel wire mesh has little effect on the bearing capacity;The stress and displacement nephogram of ABAQUS simulation results are consistent with the test results.(3)The thermal performance of AASCM sandwich plate was studied.In view of the three key problems of thermal performance of AASCM sandwich board,the influence of connectors and steel wire mesh on thermal bridge effect,and the quality of performance compared with traditional insulation materials,this paper carried out thermal tests on sandwich board and hollow ceramite block wall of 4 connectors,and analyzed the thermal bridge effect by ABAQUS.The results show that the thermal conductivity of sandwich board is 0.21W/m·K,lower than that of concrete(1.28W/m·K),building brick(0.69W/m·K),hollow ceramite block(0.41W/m·K),which can effectively play the role of heat preservation.The thermal conductivity calculated by ABAQUS is 0.25W/m·K,which is in good agreement with the experimental value with an error of 16%.Straw board plays an excellent role of heat resistance in sandwich board structure,but the thermal resistance of the connector is small,and it is easy to generate a thermal bridge in the position of the connector.Steel wire mesh amplifies the thermal bridge effect of the connectors.Considering that the influence of steel wire mesh on the bearing capacity is also small,it is suggested to replace the knot effect of steel wire mesh with connectors.