Shrinkage Performance of Cement-Treated Macadam Base Materials

Shrinkage performance is always considered as the most important characteristic of cement-treated macadam base. By using different gradation types and different levels of cement stabilized macadam mixture, the paper conducts indoor performance tests to study the mixture's shrinkage performance. Based on the tests, estimation formulas on shrinkage coefficients of the cement stabilized macadam mixtures are then elaborated. Results of the test indicated that mixes possess the lowest dry-shrinkage when 3%∼4% cement dosage are used, while temperature-shrinkage increase with cement dosages are added. Otherwise, more close-grained mixes with that have a better dry-shrinkage performance, while the temperature-shrinkage performance of these kinds of materials is worse than the sketch-grained mixes. Further analysis and test results show that shrinkage stress in base rises as cement dosage increased; a smaller cement dosage of base materials, as long as strength meets the requirement to reduce shrinkage crack in base, is feasible. Large numbers of project experience indicate that dry-shrinkage mainly occurs within 20 days when base construction complete. Moreover, compared to the continually cold winter, cracks easily form, when the temperature changes suddenly even in warm weather. Results of an indoor test show the same speciality.