Research On Anti-Cracking Performances Of The Cement Stable Macadam Adding Admixture

In highway construction, semi-rigid base as the roadbase has become the main form of China's high-class pavement structure. But as the semi-rigid base used in highway, the shortcomings appear gradually. The poorest performance is semi-rigid resistancing temperature shrinkage and drying shrinkage.It is easy to produce shrinkage crack .In the role of the vehicle load and environmental factors,the cracks can extend to pavement surface, dropping the pavement structure bearing capacity, shorting pavement life. Therefore semi-rigid base crack-resistance research has been the focus at home and abroad.The paper mainly research the anti-cracking performance of the cement stabilized macadam adding polypropylene fiber and expansive agent. Selecting cement dosage, aggregate gradation, fiber content and expansive agent content as test influencing factors, adopting the orthogonal experiment method to arrange experiments ,and analyzing the test results of the strength and stiffness adopting extremely variance and variance method, the paper obtain the optimum proportion and the rules of various factors influence strength and stiffness.Testing dry shrinkage property of selected proportion, it is concluded the rules of the dry shrinkage properties of the cement stabilized macadam with polypropylene fiber or expansive agent. Basing on several common anti-cracking evaluation indexes, the paper chooses dry shrinkage energy anti-cracking coefficient to appraise the anti-cracking performance of the three kinds of mix proportion.Adopting fiber spacing theory and complex material theory to analyze the anti-cracking mechanism of the cement stable macadam adding polypropylene fiber. It is concluded that the more the fiber per volume ,the smaller the fiber spacing ,and the anti-cracking performance is the better. Adopting expansion mechanism to analyze the anti-cracking mechanism of the cement stable macadam with expansive agent,the results show that appropriate content of expansive agent can improve the anti-cracking performance of the cement stable macadam.Finally,the paper establishe grey model and BP network model of the accumulative dry shrinkage strain. Comparing the results of the two kinds of the model, it is concluded that the BP network model is better than the grey model .