Experimental Study On Crack Resistance Of Cement Stabilized Macadam Modified By Composite Agent

Cement stabilized macadam is a typical semi-rigid material,which is widely used in road engineering in my country.It has the advantages of high strength,high rigidity,good water stability,and good frost resistance.It is especially suitable for heavy load and heavy traffic roads.However,in the course of use,the defects of semi-rigid pavement,such as high brittleness,low tensile strength,and large shrinkage,have gradually emerged.Among them,the most serious problem is reflection cracks,which will directly cause pavement diseases.Shrinkage cracks destroy the integrity and continuity of the pavement,allowing water to penetrate the pavement structure,which makes it difficult for the road to reach the designed service life.Aiming at the problem that cement stabilized crushed stone is easily affected by dry shrinkage and temperature shrinkage in the early stage to produce reflective cracks,based on the investigation of existing research results at home and abroad,this paper blends three modifiers of emulsified asphalt,SBR latex and rubber powder.Three levels of each modifier,emulsified asphalt: 2%,3%,4%,SBR: 0.5%,0.75%,1%,rubber powder: 0.2%,0.6%,1%.Ten groups of experiments were designed using the principle of orthogonal experiment.The last group was the control group.Through a large number of laboratory experiments,the relationship between the tensile and compressive strength,resilience modulus,dry shrinkage performance and temperature shrinkage performance of modified cement stabilized gravel and the emulsified asphalt content,SBR content,rubber powder content and curing time and other variables are studied.And the influence of different dosages of composite modifiers on the mechanical properties and shrinkage properties of cement stabilized macadam is analyzed.The research results show that with the increase of emulsified asphalt,SBR and rubber powder content,the unconfined compressive strength,indirect tensile strength and compressive elastic modulus of cement stabilized macadam are all decreasing,that is,cement stabilized macadam gradually transforms to flexible materials;The flexural tensile strength of the specimens continued to increase with the increase of the three modifiers.The crack resistance of cement stabilized crushed stone mixed with emulsified asphalt、SBR、rubber powder is significantly improved compared with ordinary cement stabilized crushed stone material;Corresponding to 2% of emulsified asphalt,0.5% of SBR,and 0.6% of rubber powder,the average dry shrinkage coefficient of the specimens is the smallest.The corresponding emulsified asphalt content is 2%,SBR content is 0.75%,and rubber powder content is 1%.The average temperature shrinkage coefficient of the specimens is the smallest.Comprehensive mechanical properties,dry shrinkage and temperature shrinkage properties,the recommended content is emulsified asphalt 2%,SBR0.75%,rubber powder 0.6%,the strength meets the road performance requirements while the dry shrinkage coefficient is reduced by 22%,and the temperature shrinkage coefficient is reduced by 6%.The research results of this paper provide a certain technical reference value for how to modify the shrinkage performance of cement stabilized gravel materials.