Research On The Road Performance Of Lime-fly-ash Bound Macadam Joined With Polypropylene Fibers

With the rapid development of highway transportation in our country, lime-fly- ash stabilized aggregates mixtures have been applied widely for its excellent pavement performance. But, cracks often occur in the lime-fly- ash bound macadam base due to the dry-shrinkage and the temperature-shrinkage. As a result, the applicable properties of Semi-rigidity bituminous pavement may be weakened, and also the service life of highway may be affected.At present, polypropylene fibers has been widely used in cement concrete. Although it could not enhance the intensity at a low content, it could actually prevent the crack which was caused by the dry-shrinkage and the temperature-shrinkage; when the content is high, it could not only reduce brittleness of the compound materials, but also enhance the intensity. Moreover, some research indicated that the polypropylene fiber could join and connect the crack of the cement substrate, meanwhile it could contain the separated cement blocks. Therefore we may foresee, if the polypropylene textile fiber were mixed with the lime-fly- ash stabilized aggregates at a constant ration, it should be possible to enhance the flexural strength, reduce the shrinkage and strengthen its anti-cracking performance, thus improves the road performance of Semi-rigid base and lengthens its service life. And the purpose of this article is to confirm the idea.In this research, the lime-fly- ash bound macadam was joined with polypropylene fibers with the contents of the lime, the fly ash and the macadam fixed in lab tests. The study focuses mainly on the improvement effect of road performance, such as the strength, the rigidity, the water stability, the frost resistance as well as the dry-shrinkage and its action mechanism. The findings indicated:(1) The polypropylene fiber could not enhance the early strength of the lime-fly- ash bound macadam obviously, but it could enhance the split strength, the stadium is longer, the effect is more obvious;(2) The polypropylene fiber could enhance the flexural strength of the lime-fly- ash bound macadam effectively, it also could reduce the rigidity;(3) The polypropylene fiber could enhance the water stability and frozen stability of the lime-fly- ash bound macadam in certain extent, and the effect is related to the content;(4) The polypropylene fiber could enhance the water-protecting ability of the lime-fly- ash bound macadam effectively, it also could reduce the dry-shrinkage; The research results of the paper will provide some theoretical value and direction to the study and application of the lime-fly-ash bound macadam.