Macro- And Micro-scale Experimental Study On Thermal-mechanical Properties Of Glass Fiber Foam Concret

Foam concrete has become a new type of civil engineering material widely used in all aspects of the construction field due to its excellent properties such as heat insulation,heat insulation,lightweight,and fire resistance.However,common foam concrete has such problems as low compressive strength,small modulus of elasticity,insufficient toughness,extremely brittle,excessive internal pore size,and uneven pore distribution,which limit the application prospects of foam concrete.Therefore,to improve the heat transfer,pressurebearing property,and pore structure of foam concrete,alkali-resistant glass fiber,water,cement,and foaming agent are used as raw materials to prepare alkali-resistant glass fiber foam concrete with water-cement ratio of 0.6,and the effects of the volume ratio of glass fiber and content of foaming agent on heat transfer,pressure-bearing property,pore structure and action mechanism of foam concrete are explored in this paper.Through the dry density test,water absorption test,thermal performance test,uniaxial compression mechanical property test,and electron microscope scanning test,the heat transfer and pressure-bearing properties of foam concrete are analyzed and studied.At the same time,the data of pore area,size,roundness,and aspect ratio of foam concrete material internal structure are calculated and counted by using Image-Pro Plus image analysis software,and the change rule of micro-pore structure with the content is summarized.Finally,the relationship between macroperformance and micro-structure is connected in series.Those results are as follows:(1)Adding a small amount of alkali-resistant glass fibers can improve the distribution and size of the internal pore of foam concrete,thus effectively improving the compressive strength and elastic modulus of the material,but has little effect on the heat transfer performance of foam concrete.The dosage of foaming agents is the main factor affecting the performance of foam concrete.Increasing the dosage will increase the pore size inside the concrete,which will lead to a decrease in the dry density of foam concrete,a decrease of thermal conductivity,thermal conductivity,compressive strength,and elastic modulus,and an increase in water absorption,pore area,and pore size.(2)The stress-strain curve of foam concrete can be divided into four stages: platform stage,compaction stage,yield stage,and decline stage.At the same time,its typical failure mode is longitudinal cracking.With the addition of glass fiber,the toughness of the material increases,and other failure modes such as diagonal section shear occur.(3)On the micro level,the pore area,pore size distribution,and pore aspect ratio are the important factors affecting the performance of foam concrete.Adding a small amount of alkali-resistant glass fiber can improve the size and shape of the inner pore of foam concrete,reduce the heat transfer in the framework,reduce the pore size of the inner pore,increase the specific surface area,inhibit the development of initial dry shrinkage cracks,reduce the number of connected holes and the internal defect rate of the material.Thus,the deformation resistance of foam concrete is enhanced.(4)This study verifies that adding alkali-resistant glass fiber to common foam concrete can significantly improve its compressive mechanical properties and pore structure.When the volume ratio of alkali-resistant glass fiber is less than 0.375%,the larger the volume ratio,the higher the compressive strength and elastic modulus of foam concrete,and the maximum increments are 27.9% and 15.0% respectively,Optimum fiber content is 0.375%.In addition,alkali-resistant glass fiber can effectively inhibit bubble formation with pore diameter d >1mm.On the other hand,when the amount of blowing agent is less than 1.0%,the more the amount added,the smaller the dry density of foam concrete,but at the same time,its compressive mechanical properties and Micro-properties will be greatly weakened.Through the above research,the compressive mechanical properties and pore structure influencing factors of alkali-resistant glass fiber foam concrete are analyzed in depth,which provides a more reliable theoretical basis for its application in practical engineering.At the same time,it has important reference value for the design and preparation of alkali-resistant glass fiber foam concrete and also provides direction for future related research.