Study On Materials Of Durable Cement Stabilized Gravel Base Based On Crack Resistance Properties

Semi-rigid base asphalt pavement is widely used in China.Its advantages are high strength and strong bearing capacity.It is a pavement structure type suitable for the current situation of road traffic in China.However,when the semi-rigid base material is affected by external temperature and humidity changes,it is easy to produce dry shrinkage and temperature shrinkage stress,resulting in cracks in the base layer.The cracks gradually develop under the action of stress and eventually reflect to the pavement surface layer,resulting in damage to the pavement structure.The problem of reflective cracking has always restricted the development and application of semi-rigid base pavement structure.Adding fiber into cement stabilized macadam material is an effective measure to improve the cracking problem of semi-rigid base.In this paper,it is proposed to improve the crack resistance of cement stabilized crushed stone by adding self-developed high toughness special fiber into cement stabilized crushed stone material.On the basis of improving the dispersion process,the influence of different fiber content on the mechanical properties,crack resistance and mechanical behavior of cement stabilized macadam was investigated through systematic mechanical properties test,shrinkage fatigue test and mechanical behavior relationship.By improving the preparation process of cement stabilized crushed stone,the dispersion problem of fiber in cement stabilized crushed stone is solved.The influence of fiber content on the mechanical properties of cement stabilized crushed stone is obtained by mechanical properties test,including unconfined compressive strength test,splitting strength test,uniaxial compression modulus test and flexural strength test.The results show that the fiber is pre-mixed with cement and some fine aggregates,so that the fiber is pre-dispersed in the cement mortar,and then the cement mortar is mixed with the aggregate.This method can effectively disperse the fiber in the cement stabilized crushed stone material.After adding fiber,the mechanical indexes of cement stabilized crushed stone are improved.The unconfined compressive strength,splitting strength and uniaxial compression modulus of cement stabilized crushed stone increase first and then decrease with the increase of fiber content.The flexural strength of cement stabilized crushed stone with different fiber content is not much different.When the fiber content is 1 ‰,the unconfined compressive strength,splitting strength and flexural strength reach the maximum value.The uniaxial compression modulus reaches the maximum when the fiber content is 2 ‰,but it is not much different from 1 ‰.Based on the study of mechanical properties,temperature shrinkage test,dry shrinkage test and fatigue test were carried out.According to the test results,the influence of fiber on the shrinkage and fatigue resistance of cement stabilized macadam was studied,and the shrinkage coefficient and fatigue equation of cement stabilized macadam with different fiber content were obtained.The results show that the addition of fiber can improve the temperature shrinkage and dry shrinkage performance of cement stabilized macadam.When the fiber content is 1 ‰,the temperature shrinkage coefficient and dry shrinkage coefficient are reduced by 14.1 % and 12.8 % respectively.The improvement of fiber on the fatigue performance of cement stabilized macadam is mainly in the case of low stress ratio.Under high stress ratio,the effect of fiber on improving fatigue performance is not obvious.At the same time,the stress-strain curve is used to study the mechanical behavior of fiber cement stabilized crushed stone.The variation trend of stress-strain curve and the deformation and failure process of cement stabilized crushed stone are analyzed.The variation law of fiber content on peak strain and secant modulus is obtained,and the influence of fiber content on the failure strain energy of cement stabilized crushed stone is discussed from the perspective of energy consumption.The results show that after adding fiber,the peak strain of cement stabilized crushed stone increases,and the secant modulus decreases.At the same time,the incorporation of fiber slows down the stress attenuation rate of cement stabilized macadam after reaching the peak stress,so that the energy consumed in different failure stages increases,and the deformation of cement stabilized macadam increases.