Study On Resistance To Initiation Fracture For Cement Stabilized Base Course In Arid Desert Region

Located in arid desert region, Xinjiang forms extremely arid continental climate with dry climate,winter cold and summer hot and the average annual rainfall of145mm. Large temperature differenceis obvious in much of the region. The biggest temperature difference is between20℃and25℃dayand night. The maximum annual temperature can go up to70℃. The temperature contraction anddrying shrinkage crack of the cement stabilized base course are inevitable. With the deepimplementing of western development and the construction of a big province of resources, the existingroad’s overloading is very serious. Moreover, harsh climate brings obvious deformation forload-bearing layer. The study has important meaning of solving cement stabilized base course’s crackdiseases in exceptional circumstances in arid desert region and meaning of reality for extending roadlife and reducing costs of maintaining the roads.First, the paper points out different physical and chemical properties of the most commonly usedroad-building material--cement stabilized grit base course in big temperature circumstances in ariddesert region of Xinjiang and aggregates cement stabilized base course for test analysis. Typical roadsections in southern, northern and eastern Xinjiang are selected to study the proper proportion betweencement stabilized base course of aggregate and crack resistance of cementing materials. Based onpreliminary field investigations and laboratory tests, under the condition of drought and bigtemperature, the mixing amount of dense framework type of cement stabilized base course should bebetween3~4%, and the dense-suspended type and framework-interstice type is proper between3.5~4.5%. Meanwhile, the vibrating compaction of cement stabilized gravel is analyzed and comparedin the paper. The analysis finds that for different compacting method, the maximum of dry densitydemonstrate the same law that the maximum of dry density determined by vibration moldings is1.01~1.02times than that by heavy compaction.Secondly, we make a thorough study on aggregate grading of cement stabilized base course’simpact on distortion. The test about dry-shrinkage and temperature contraction with different gradingand dosage of the mixture ratio of the cement stabilized sand and gravel as well as the test on intension,stiffness and CT scan adding coarse aggregate to the cement stabilized sand and gravel has effects oncrack resistance. It is found by CT that smaller aggregate formed by the destruction of large aggregatein mixture of cement stabilized base course still has a certain strength. Meanwhile, based on “06Design Guideline”“034Construction Criterion” and study on pavement performance of typical roads’structure type, the aggregate scope of dense framework type’s crack-resisting structure is proposed.Finally, to verify the results of laboratory tests, the test sections are paved in the typical roads inthe region of drought and big temperature. The later testing finds that cement stabilized base course’searly cracks can be effectively reduced by increasing the coarse aggregate’s content in the graded sandgravel and reducing cement content to a proper portion.