Experimental Study On Properties Of Pavement Base Course Using Cement Stabilized Large-sized Recycled Concrete Aggregate

A large amount of waste cement concrete materials are produced in road rehabilitation and expansion projects in China. Recycling the waste concrete materials scientifically and efficiently has important implications for sustainable development of the highway transportation, resource conservation, emissions reduction, environment protection and cost reduction of highway construction. In this paper, the performances of recycled concrete aggregate and pavement base course using cement stabilized large-sized were studied, and the test road of national first class highway was paved based on the experimental study. The research contents and conclusions obtained in this paper are as follows.(1) Study on properties of recycled concrete aggregateTest and contrast the water absorption, crushed stone value, flat and elongated particle in coarse aggregate and apparent density of the natural and recycled aggregate. The results show that recycled aggregate basically reaches the material technical requirements of pavement base course; the performance indexes of natural aggregate change little with aggregate size, but that of recycled aggregate change significantly.(2) Study on chemically reinforcement of recycled concrete aggregateProcess recycled concrete aggregate using organic silicone resin solution, silane coupling agent and titanate coupling agent. Using water absorption and crushed stone value as key evaluation index of chemically reinforcement effects, test results show that organic silicone resin solution has the best chemically reinforcement effects, the optimal cement is 4%, the optimal mixing time is 120 s, and the optimal curing time is 6h and 12 h under 105℃ and room temperature respectively. The water absorption and crushed stone value of recycled aggregate reduce 33.8% and 58.1% respectively after processed by organic silicone resin solution, and the performance of recycled aggregate is improved by a large margin.(3) Study on properties pavement base course using cement stabilized large-sized recycled concrete aggregateTo study the effects of aggregate gradation type and the largest aggregate size on properties of cement stabilized recycled aggregate, skeleton dense and suspended dense structure cement stabilized recycled aggregate of 53 mm largest aggregate size, and skeleton dense structure cement stabilized recycled aggregate of 37.5mm largest aggregate size were designed. Given high mud content of the unwashed recycled aggregate, design skeleton dense structure cement stabilized recycled aggregate of 53 mm largest aggregate size, and 30% of the fine aggregate smaller than 0.6mm is replaced by soil to simulate the disadvantage in construction. Test the mechanical performance indexes, such as unconfined compression strength, compression modulus of resilience, indirect tension strength, flexural-tensile strength and flexural-tensile modulus, shrinkage performance indexes, such as temperature contraction coefficient and dry contraction coefficient.The test results show that the shrinkage resistance properties of cement stabilized recycled concrete aggregate can be obviously improved through appropriately increasing the largest aggregate size within limits. The aggregate gradation type has significant effects on the mechanical and shrinkage performances of cement stabilized large-sized recycled aggregate, and the skeleton dense structure is distinctly superior to the suspended dense structure. The mechanical and shrinkage performances of the cement stabilized large-sized recycled aggregate of high mud content decrease significantly.(4) Pave the national first class highway test road using cement stabilized recycled concrete aggregate. The field test compression strength, compression modulus of resilience and indirect tension strength not lower than indoor test results, because the field test compactness is slightly higher than designed compactness, and the daily mean temperature in the field is higher than the standard curing temperature in the laboratory. The core samples taken in the field of cement stabilized recycled concrete aggregate after curing 7d are complete, and don’t exist obvious fault and unconsolidated formation, shown that there is not severe mixture segregation in the construction, and the test road subbase course is in good integrality.