| Building fire caused by organic insulation materials has become an important issue of city safety.The new development tendency of insulation walls requires not only good thermal insulation,but also good performance of fire-resistance and durability.Foamed concrete is an inorganic lightweight insulation materials with high-strength,good heat insulation and good fire-resistance and durability,which can be prefabricated in factory and assembled on site.It achieves the integration of enclosure and thermal insulation and complies with the concept of green energy-saving building and fabricated construction.Foamed concrete is now one of research focuses of building materials,but most researches focus on the properties of foamed concrete at normal temperature.Studies of properties of foamed concrete at elevatedtemperature are still in primary stage and researches on fire-resistance of foamed concrete members are not perfect.In this context,in onder to instruct the application of foamed concrete,this thesis studies the fire resistance of precast foamed concrete wall board from two levels which are material and element.The main work is as follow:(1)Thermal properties of foamed concrete at two density grades of A06 and A07,including specific heat,thermal conductivity and thermogravimetric,were measured in the temperature range of 20℃～800℃.Base on the test result,the thermal conductivity model of foamed concrete at elevated-temperature based on EMPT model and the equation of specific heat of foamed concrete at elevated-temperature considering moisture transfer were proposed.(2)Experiments of 42 prisms and 84 cubes of foamed concrete at two density grades of A06 and A07 were conducted to investigate the influence of density grades and temperature on the mechanical properties including appearance,axial compressive strength,elastic modulus,peak strain,stress-strain relationship,Poisson’s ratio,cubic compressive strength and splitting tensile strength after elevated temperature.Base on the results,equations of axial compressive strength,elastic modulus,peak strain,cubic compressive strength and splitting tensile strength of foamed concrete and a model of stress-strain relationship of foamed concrete after elevated temperature were suggested.(3)Three precast foamed concrete wall boards were exposed to fire on one side to investigate the fire resistance of the wall boards and the temperature field of the walls was analysed.The results show that precast foamed concrete wall boards have excellent performance in fire resistance which is far better than what the fire code requires and both two kinds of wall seams proposed in the paper can meet the requirements of the fire code.Besides due to moisture transfer in the foamed concrete,a long-period temperature plateau around90℃～100℃ occurs during the heating process of foamed concrete wall boards.(4)Based on the heat transfer analysis method of adding additional specific heat to consider the moisture transfer and the thermal property models of foamed concrete at elevated temperature proposed by this paper,the precast foamed concrete wall boards exposed to oneside fire were simulated by using ABAQUS software and the simulation results were compared with the fire test.Then parametric analyses were simulated to study the influence of parameters including density of foamed concrete and water content and the residual bearing capacity after fire was simulated.The results show that the temperature field obtained by ABAQUS has a good agreement with the experimental results.In addition,the lower density of foamed concrete provides better fire-resistance.Besides water content is the key factor to temperature distribution of foamed concrete,the more water content the foamed concrete contains,the longer period of temperature plateau due to moisture transfer it undergoes and the lower temperature it has on the unexposed side.It is also found that the precast foamed concrete wall boards have a high residual bearing capacity. |
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