Research On Mix Design And Performances For Anti-cracking Cement Stabilized Macadam

Because of such advantages as high strength, large stiffness, finestabilization, low cost and so on, cement stabilized macadam is widely used asa semi-rigid base in high grade highway pavement. However, because it hasthe effects of dry shrinkage and temperature shrinkage, the cement stabilizedmacadam base is easy to produce a lot of shrinkage cracks and extend to theasphalt surface forming reflection cracks, which have seriously influenced thepavement performances and the service life of asphalt pavement. Therefore,according to the problem of easy production of shrinkage crack for thecement stabilized macadam base, the research on mix design and performancesof anti-cracking cement stabilized macadam has carried out by a lot of indoortests.1) The highways with representative cracks were selected to investigateon the spot, detect with the PFWD in the field and test the cores in thelaboratory. The production causes of crack disease for asphalt pavement withthe cement stabilized macadam base were comprehensively analyzed, and theresults show that the main causes of producing cracks after the shaping ofcement stabilized macadam base are the uneven cement content and themixture segregation.2) Through the analysis of the material structure and the gradation theoryfor the cement stabilized macadam, the coarse aggregates and the fineaggregates were separated to design each gradation, respectively. Thecomposite gradation was determined through the tests, and the designgradation was tested and verified with the Bailey Method. Finally the anti-cracking gradation was determined, and the cement content was determined as4% through the test analysis.3) In the condition of 4% cement content determined by the tests, thespecimens of the design anti-cracking gradation and the specificationgradation with medium value were made respectively. Their mechanicalproperties and pavement performances were tested comparatively, and the results show that, compared with the specification gradation, the designgradation is higher than 12.6%, 24.1%, 8.6% and 14.1% in compressionstrength, tensile strength, compression resilient modulus and flexural tensilestrength, and lower than 23.1%, 11.9%, 14.3%, 41.8% and 42.5% in dryshrinkage strain, dry shrinkage coefficient, average temperature shrinkagecoefficient, total scour amount and total mass loss ratio, respectively.Therefore, the design gradation has an excellent anti-cracking performance.4) According to the test results of indoor and outdoor, the constructiontechnology and the quality control technology were studied for the anti-cracking cement stabilized macadam base to put forward the guides ofconstruction technology and the standards of quality control.In summary, the researches can provide a scientific reference to improvethe anti-crack performances of the cement stabilized macadam base.