Study On Composite Roof Performance Of Foam Concrete/Vacuum Insulation Plate

With the development of society and economy,the energy problem is becoming more and more serious.As a large country consuming building resources,building energy consumption accounts for about 40%of the total energy consumption of society,and the proportion of heat transfer loss of roof is larger.In order to reduce the heat loss of building roof structure,the state has listed the technology of improving energy-saving performance of roof system as "energy-saving technology".The 13th Five-Year Plan of National Key R&D Program.At present,the heat transfer coefficient of the roof insulation layer used in our country is generally about 0.6W/m2.K.The goal is to reduce the heat transfer coefficient to less than 0.2W/m2.K by improving the roof insulation material and upgrading the roof insulation technology.In this paper,the vacuum insulation board which has not been widely used in building roof is chosen as the main roof insulation material.The outstanding insulation performance of the vacuum insulation board is fully utilized to improve the insulation performance of the roof insulation system.Vacuum insulation board(VIP board)is composed of filling core material and vacuum protection surface.It can effectively avoid heat transfer caused by air convection,and has the characteristics of environmental protection and high efficiency and energy saving.However,as a single roof insulation layer,it is vulnerable to damage by other attachments,and the pressure puncture loses the vacuum environment,which affects its heat transfer coefficient and reduces the thermal insulation performance.The purpose of this paper is to simulate the design of foam concrete and vacuum insulation board composite thermal insulation roof structure,protect the vacuum insulation plate from being damaged,and test and improve the properties of foam concrete,so as to achieve the purpose of improving the thermal insulation performance of roofing.Firstly,the thermal insulation structure of composite roof is designed,and the law between the gap and the heat transfer coefficient of the vacuum insulation board is obtained by calculating the heat transfer coefficient of the composite roof panel.Secondly,the three-dimensional thermal conduction of the composite insulation roof is simulated by the original COMSOL Multiphysics 5.0,and then the chemical and physical foaming methods are used.Foam concrete is prepared,and factors affecting the performance of foamed concrete are explored.Finally,a 1.4*1.4*0.3m composite board is made by compounding foam concrete with better performance and vacuum insulation plate,and the heat transfer coefficient of the composite plate is determined.The composite roof structure design and calculation results show that the heat transfer of composite insulation roof made of vacuum insulation board and foam concrete mainly occurs in the area of foam concrete.In the design of composite structure of foam concrete and vacuum insulation panel,the larger the gap between the vacuum insulation panels,the greater the heat transfer coefficient of the composite panels.The gap between the vacuum insulation plates is calculated to be 5 cm,which theoretically reduces the heat transfer coefficient to 0.11W/(m2.K).The results of foam concrete research show that when the amount of fiber is 2%,the ratio of compression to compression is 0.33 when the foam concrete is prepared by chemical foaming method.The toughness of foam concrete is the best.With the increase of the content of polypropylene fiber,when the content of polypropylene fiber is 2.5%,the water absorption can be significantly improved,and the shrinkage rate is small.When the dosage of rubber powder is 1%,the mechanical properties of foam concrete are better.At the same time,the change of water absorption rate of foam concrete tends to be stable.When the age is 28d,the shrinkage rate of rubber powder mixed with 0.5%and 1%is close.Considering 1%,the amount of rubber powder can make the performance of foam concrete better.When the polystyrene particle size is 3:1,the mechanical properties of the foam concrete are better,and the water absorption rate is the smallest at this time.When foamed concrete is prepared by physical foaming method,when the water cement ratio is 0.55,the strength of foam concrete is the best,and the shrinkage rate of foam concrete is the smallest.The performance of foamed concrete can be improved by selecting every 500g cement mixed with 2L polystyrene particles.With the increase of dry density,the thermal conductivity of foam concrete increases and water absorption decreases.The shrinkage rate also decreases.The test results of the trial-produced roof slab show that the heat transfer coefficient of the measured roof slab is 0.15W/(m2.K),which achieves the research target of this subject of 0.2W/(m2.K).