Mechanical Characteristic Of Paverment Overlay The Micro-bonded Graded Aggregate

Under the condition of the road elevation allowed, the cement concrete pavement overlay asphalt surface, setting up steady or unsteady graded gravel intercalation can make full use of the old board, better to delay reflective cracks of the overlay asphalt pavement, improving the comfortable of overlay pavement. At present such materials and structures has began to use for cement concrete pavement overlay asphalt surface in Fujian province, but the research and practice are still lack.The paper bases on physical works " Add-surfacing AC Layer on the PCC" test road in Fujian Province, focusing on studying the mix proportion design, mechanical properties, shrinkage characteristics, overlay structure performance, construction technology of the low dose cement stabilized grading aggregate and emulsified asphalt cement stabilized grading aggregate these two functions interlayer material, through laboratory material test and field test methods. Specific conclusions are as follows:The 7d unconfined compressive strength、28d splitting strength and 28d compressive modulus of low dose cement stabilized grading aggregate are about 0.24～0.67、0.13～0.45、0.34～0.67 times of cement stabilized macadam, about 1.26～2.38 times of the compressive resilient modulus of graded aggregate. In the lower dose of cement (1%,2%),suspension grading has a greater compressive strength at the early stage, sooner form board body, more prone to early shrinkage cracking; continuous gradation mixture has the least splitting strength at 28d; compressive modulus of resilience of skeleton dense structure is slightly higher than suspension dense structure. The dry shrinkage coefficient of low dose cement stabilized grading aggregate is about 0.14-0.38 times of cement stabilized macadam, it has little difference temperature shrinkage coefficient with cement stabilized macadam. The cement dose and mixture gradation are important factors to shrinkage characteristic.The 28d unconfined compressive strength and 28d compressive modulus of emulsified asphalt cement stabilized grading aggregate are about 0.47～0.78、0.7～0.89 times of the same 2% dosage of low dose cement stabilized grading aggregate, but the 28d splitting-strength of both have no great difference. The more use of the dosage of emulsified asphalt, the more reduce of the early strength of mixture reduced with more extent, also rudce the 28d unconfined compressive strength and 28d compressive modulus decreases. And the asphalt content has little effect on the 28d splitting-strength.The dry shrinkage coefficient and temperature shrinkage coefficient of emulsified asphalt cement stabilized grading aggregate are about 0.68-0.81-. 1.01～1.05 times of the same 2% dosage of low dose cement stabilized grading aggregate, but the is larger. The more use of the dosage of emulsified asphalt, the mixture dry shrinkage coefficient become smaller, the temperature shrinkage coefficient become larger; when 2% cement dose and 2%～6% asphalt emulsion content, its dynamic stability was more than 10000 times/mm, higher than the specification requirements for asphalt mixture and its immersion residual stability was not less than 80%.Through the Field test we found that, the way of rolling and rolling power significant effected on base compactness; microbond graded aggregate overlay old pavement show bigger rebound modulus, setting up microbond graded aggregate is beneficial to improve the asphalt surface layer modulus uniformity and improve old pavement’s modulus and reduce the the difference of deflection; the overlay structure of setting up microbond graded aggregate has more resilience than the direct overlay structure.Comprehensive study shows that the micro-bonded graded aggregate as cement concrete overlay functional interlayer.should have the enough thickness of asphalt surface layer and control the thickness of microbinding graded gravel, construction should pay special attention to ensure the quality of material grading skeleton, to make sure have enough curing age before the opening of traffic.