Study On PVA Fiber Improving Mechanical And Frost Resistance Of Lightweight Aggregate Concrete

In recent years,due to the damage of concrete freezing and thawing,the service life of buildings has been shortened more and more seriously in the cold area of North China.In this paper,PVA fiber reinforced lightweight aggregate concrete was prepared,and its length(3 mm,6 mm,9 mm),content(0.1%,0.2%,0.4%)and water binder ratio(0.4,0.42,0.45)were taken as the research objects to study the improvement effect of PVA fiber on various properties of lightweight aggregate concrete.The early mechanical properties of the concrete were studied by measuring its compressive strength and splitting tensile strength in 3D,7d,14d and 28d.The frost resistance of the concrete was evaluated by the change of the mass loss rate and the relative elastic modulus of the concrete under the freeze-thaw test.The internal structure of PVA fiber lightweight aggregate concrete was studied by means of NMR and SEM.The range analysis and grey system analysis are used to analyze the test data.1.The internal microstructure of PVA fiber lightweight aggregate concrete was observed by SEM,and the influence of the internal microstructure on its compressive strength and frost resistance was analyzed.2.The pore structure of PVA fiber reinforced lightweight aggregate concrete was studied by NMR,and the influence of different pore characteristics such as porosity and pore size distribution on its compressive strength and frost resistance was analyzed.3.The internal relationship between the compressive strength of concrete and the characteristic parameters of NMR porosity is analyzed by means of grey correlation analysis.4.MATLAB is used to fit the early compressive strength of concrete,and the applicability formula of early compressive strength and age of PVA fiber lightweight aggregate concrete is established.5.Based on the results of freeze-thaw cycle test,the damage model of concrete is established,and the life of PVA fiber lightweight aggregate concrete is predicted according to the actual service conditions in different areas.