Experimental Study On The Properties Of Silica Fume And Its Influence On The Performance Of Porous Cement-treated Mixtures

Setting a porous cement-treated mixtures base in the pavement structure layer can quickly drain the free water that penetrates into the structure layer,thereby reducing water damage and prolonging the service life of the road.For the porous cement-treated mixtures base,improving its strength and durability is the focus of research.As an additive material,silica fume have been used in building materials to improve the mechanical properties of the structure.This topic takes the porous cement-treated mixtures base as the research object,and explores the effect and mechanism of different silica fume on the road performance of the porous cement-treated mixtures base.The main research content of this paper:(1)Analysis of microscopic properties of five kinds of silica fume,analysis of silica fume particle size distribution,composition and pore characteristics.(2)Silica fume cement mortar test: the strength and fluidity test of silica fume cement mortar,to explore the law and mechanism of the influence of different silica fume on the performance of cement mortar.(3)The design of the mix ratio of porous cement stabilized crushed stone,based on the requirements of drainage and strength,determines the aggregate gradation,the amount of cementitious material,and the molding method.(4)Porous cement stabilized crushed stone base performance test:the unconfined compressive strength,flexural tensile strength,compressive resilience modulus and water permeability test of porous cement stabilized crushed stone of different gradations,etc.,analyze the gradation,silicon The influence of ash properties on the road performance of cement stabilized macadam.The primary conclusions come out :(1)The particle fineness,void characteristics and mineral composition of different silica fume are obviously different,and their characteristics are related to the performance of cement mortar.(2)The strength of different silica fume cement mortars is significantly different.The highest compressive strength and flexural strength is 3# silica fume.The reason for the best lifting effect is related to its chemical composition,particle distribution characteristics,and smaller pore volume values..(3)Design three kinds of porous cement stabilized crushed stone gradations,single gradation two(A grade is 4.75mm～9.5mm,B grade is 9.5mm～15mm),double gradation(C grade,determined by volume method The ratio of aggregates of4.75mm～9.5mm and 9.5mm～15mm is 3:7);the water permeability coefficients of the three grades of cement stabilized crushed stone are 13.5,11.3,and 14.3 respectively,with good drainage performance;7d of grade C has no side The limit compressive strength is the highest.(4)The addition of silica fume can significantly increase the 7d unconfined compressive strength of porous cement crushed stone,and the strength of internal and external silica fume in gradation C increases by 23.5% and 45.8%,respectively.(5)The indoor compressive elastic modulus of the three grades of porous cement macadam is754.4MPa,746.1MPa,865.6MPa respectively.After adding silica fume,the compressive elastic modulus increases by about 10%-19.0%.(6)Silica fume can effectively improve the crack resistance of porous cement stabilized crushed stone.After adding silica fume,the flexural tensile strength of C-graded porous cement stabilized crushed stone will be increased from 0.7MPa to 0.8MPa,and the fracture strain energy will increase by 13.8%.