Study On Thermal And Fire Resistance Of Microporous Concrete Composite With Six Coated Organic Cores

With the proposal of the "dual carbon target",China’s requirements for building energy efficiency continue to increase.Measures to reduce energy consumption by enhancing the insulation and insulation performance of building envelopes have achieved remarkable results.However,the thin plastering system for external wall insulation that has been promoted for more than a decade often encounters problems such as organic insulation material catching fire and inorganic insulation material cracking and falling off.According to the "Technical Standards for External Wall Insulation Engineering"(JGJ144-2019),the system can meet the requirements with a service life of no less than 25 years,but in reality,the majority cannot reach 25 years.Obviously,the single functional wall materials involved in this system can no longer meet the requirements of China’s energy-saving and high-quality development of buildings.The composite insulation template proposed in this article,which is made of microporous concrete covered with organic core materials,is a type of thin plaster system used for the exterior walls of frame structure beams and columns and shear walls.It is used as the external template during the construction phase and does not need to be removed afterwards.It directly serves the building walls for life and undertakes various functions such as insulation,heat insulation,and fire prevention.It replaces the thin plaster system that achieves insulation through secondary construction after the original main body is completed,Realize the same lifespan and fire protection level of the external wall insulation layer as the building.This insulation template fully utilizes the fire resistance performance of inorganic insulation materials and the thermal insulation performance of organic foam materials through close material composition,achieving the multifunctional function of external insulation walls.In order to better explore the impact of composite insulation templates on the thermal and fire performance of walls,this article will conduct research on composite insulation templates from two aspects: materials and the structural form of the composite.The specific content is as follows:(1)Preparation of 600-1200 kg/m ~3 Test the compressive strength,thermal conductivity,and water absorption of microporous concrete.The results show that as the unit weight of microporous concrete increases,the compressive strength and thermal conductivity show an increasing trend,while its water absorption rate shows a decreasing trend.After research,the relationship between unit weight and performance is obtained,forming a relationship formula.On this basis,the relationship between the pore structure and performance of microporous concrete was further studied,and the results showed that the pore structure is closely related to the compressive strength and thermal conductivity of microporous concrete.The small,uniform,and dense pore structure is very beneficial for increasing the strength,reducing the thermal conductivity and water absorption of microporous concrete.(2)Through theoretical calculation,hot box test and ANSYS numerical simulation,the influence of microporous concrete unit weight and formwork structure on heat transfer resistance and heat transfer coefficient of composite insulation formwork wall was studied;The error between the finite element simulation values and the experimental values is only within 5%,indicating that the simulation results have certain reference value.Through theoretical calculation and finite element simulation results,a correction coefficient of 1.18 is obtained,which ensures the accuracy of one-dimensional calculations.(3)Simulated fire and high-temperature environment,studied 600-1200 kg/m~3 The changes in mass loss,compressive strength,and thermal conductivity of microporous concrete exposed to high-temperature environments show that as the temperature increases,the mass loss of microporous concrete increases,while the compressive strength and thermal conductivity overall decrease;The unit weight grade has a significant impact on the high-temperature resistance of microporous concrete,but at 800 ℃,the basic properties of microporous concrete of each unit weight grade tend to be consistent.(4)The single side heating test and high temperature thermal shock resistance test of the composite were independently designed to simulate the influence of the volume weight of microporous concrete and the structure form of the composite on the fire resistance of the composite insulation formwork when exposed to high fire temperature and open fire.The two groups of test results show that the protective performance of high volume weight microporous concrete is better than that of low volume weight microporous concrete;The protective layer of 15 mm and 20 mm thick microporous concrete showed varying degrees of melting of the internal core material in both sets of tests,while the protective layer of 25 mm thick microporous concrete had excellent protective performance and the internal core material was not damaged.When the fire resistance limit of the composite insulation template meets the requirements,when the unit weight of the microporous concrete is 1200 kg/m ~3、When the thickness is greater than 25 mm,the combustion performance of composite products can be evaluated as equivalent to Grade A of homogeneous materials.In addition,microporous concrete and ordinary concrete form sandwich products with polystyrene board respectively,and the fire resistance performance is compared.The protective layer thickness of microporous concrete with a thickness of 15 mm is better than that of ordinary concrete with a thickness of 50 mm.