Performance Of Different Types Of Cement Stabilized Crushed Stone Semirigid Materials For Pavement Base

The pavement base, located under the surface of pavement, bears the vehicle loadpassed from the surface of pavement and spreads it to the subgrade. Cement stabilizedcrushed stone is the most common form of semi-rigid base, which is widely used inhigh grade highway pavements in our country. At present, most of the high gradehighway pavements use the traditional floating dense cement stabilized crushed stonebase material. In recent years, in order to meet the requirements of cracking resistance,the frameworking dense cement stabilized crushed stone base material is developed.This thesis is a comparative study of the two types of cement stabilized crushed stonebase materials, which should provide a reference for the selection of base material inroad engineering.In this thesis, studied properties of cement stabilized crushed stone basematerials include: volume properties, strength properties, stiffness properties,shrinkage properties. The test results show that the skeleton distraction rate, air voids,temperature shrinkage coefficient and dry shrinkage coefficient of floating densematerial are higher than those of frameworking dense material. The maximum drydensity, unconfined compressive strength, splitting strength, fracture toughness,compressive resilient modulus, and splitting modulus of frameworking dense materialare higher than those of floating dense material.In the road engineering, the anti-cracking effect of the base material is alwaysconcerned, since it directly influences the service life of the road. It should be pointedout that the strength properties, stiffness properties, shrinkage properties of basematerial affect the anti-cracking effect of base material in a certain way, and then theyaffect the service life of pavement indirectly. This thesis introduces the ultimatetemperature drop and ultimate moisture loss as two anti-cracking indexes. Analyseswere performed of anti-cracking effect of the floating dense and frameworking densecement stabilized crushed stone base materials with the actual condition of thehighway engineering (the higher the ultimate temperature drop and ultimate moistureloss of base material are, the better the anti-cracking effect of base material is).Results of the analyses show that for the same cement content, the ultimatetemperature drop of the floating dense material is lower than that of the frameworkingdense material. In low cement content, the ultimate moisture loss of the floating dense material is higher than that of the frameworking dense material. In high cementcontent, the ultimate moisture loss of the floating dense material is lower than that ofthe frameworking dense material.Results of the analyses also show that the optimum cement content of thefloating dense material is about5.5%, and the optimum cement content of theframeworking dense material is about3.5%, which is defined as the cement contentmeeting the minimum required strength. Comparisons under the optimum cementcontents indicates that, when the base has no initial cracking, the ultimate temperaturedrop and moisture loss of the frameworking dense material are240%and88%higherthan those of the floating dense material, respectively; when the base have initialcracking, under the optimum cement content the ultimate temperature drop andmoisture loss of the frameworking dense material are254%and95%higher thanthose of the floating dense material, respectively. Results of the analyses show that,compared with the floating dense material, the frameworking dense material not onlyhas lower optimum cement content, but also has superior anti-cracking effect.