Influence Factors And Technological Measures On Early-cracking In Cement Concrete Pavements

It is well known that breakage is one of the major damages in cement concrete pavements. Once it happens, the breakage will go with other type of concrete pavement distresses. Otherwise not only hard of the repair work, but also the pavement performance reduces greatly. Based on domestic and abroad researches, experiments and observations were used which combine with construction quality control in practical projects to study effecting factors on early breakages and preventing technique in cement concrete pavements.(1) Investigation and analysis were made in the cause of cement concrete pavement breaking damage during construction and maintenance. Cutting timing, temperature dropping range, mixture components design and maintaining measures are found to be the key factors that influence cement concrete pavement early breakages.(2) Dense aggregate gradation, under the satisfaction of workability, low sand percentage and high content of coarse aggregates plus early strength retarding water reducing agent are found to reduce breakages in cement concrete pavements that of dense aggregate gradation.(3) During the construction and maintenance stages, low aggregate temperature and rational maintenance measures can help effectively reduce early breakage percentage.(4) On the basis of concrete strength at different ages, it is suggested that allowable temperature reducing range should not exceed 5 to 6 centigrade and the temperature gradient should not exceed 0.45 centigrade per centimeter.(5) Joint cutting is a major method to prevent cement concrete pavement breaking. Strength growth curve shall be gained at given maintenance and component design condition. The best cutting strength and rational cutting timing have to be determined. It is found that the critical slab length of early breakages in cement concrete pavement be determined by friction factor between surface and base layer. Even the cutting schedule is confined, critical slab length shall be the first step and the design slab length be the second one.(6) It is suggested that shading and wind-break canopy should be adopted to retain the original temperature and moisture after the construction. At ascent and descent sections of road, Speed-up and brake of the car contribute to the breakages of the cement concrete pavement and skew cutting technique is proposed to apply.