Study On The Engineering Application Of Coarse Aggregate Interlocking Pavement Concrete

Conventional concrete proportioning design is based on the considerations of the workability of fresh concrete mixtures and the mechanical properties of hardened concrete. In order to ensure reasonable workability and homogeneity of fresh concrete mixtures and avoid gravity segregation, the volume content of the coarse aggregate in ordinary plastic concrete must be kept at a low level, resulting in the strength framework and interlocking effect of coarse aggregate can not be fully performed because of the suspending state of aggregate in the concrete. At present, the dosage of cementations materials continuously increase, led to excessive paste could not be used effectively while the shrinkage and crack risk of concrete increase. How to insure concrete performance while decreasing cement dosage and increasing coarse aggregate content is helpful to reduce the cost of engineering projects and lessen the carbon emission of concrete.Based on the above analysis, a new concrete placement process named scattering-filling aggregate method, in which 10% to 30%(in volume for the concrete)coarse aggregate is added while the concrete is being cast, paved or placed, and then the matrix is vibrated to prepare "coarse aggregate interlocking concrete", also named scattering-filling aggregate concrete.Under the condition of optimal choice of raw materials and optimizing mix design of original concrete, the scattering-filling aggregate process applied in the reconstruction project of 305 provincial roads was studied. The results indicate that the 28d compressive strength of scattering-filling aggregate concrete with the coarse aggregate replacing volume ratio of 8% increases obviously, which is nearly 10% higher than the conventional concrete; the 7d flexural strength gets a little decrease but the 28d flexural strength improves slightly compared with the original concrete. Through the spot observation and later testing, laitance coating and bleeding almost disappeared, early age cracks of concrete plates decreased markedly, the breaking of plates were almost eliminated completely, the pavement quality was optimistic and the 28d flexural strength exceed the designed index.Backcourt scattering-filling aggregate process was invented for realizing mechanical execution. The definition of this method is the coarse aggregate are filling in the fresh mixture when mixing process is nearly finished by the machines of the batching & mixing plant, to form homogeneous concrete mixtures after extra 3-5 seconds mixing. This process were successfully utilized in the Sisha road project.Volume analysis of ingredients in scattering-filling aggregate concrete indicates the added aggregates make the sum volume of aggregate in the concrete reach 72% which is beneficial to the concrete strength and the proportion of cement mortar decreases obviously. The concrete cost can save 9-10 yuan/m3 concluded by the economy analysis.Finally, coarse aggregate interlocking pavement concrete was analyzed by life cycle assessment (LCA). The results demonstrate the CO2 emission (concluded from the dosage and transportation of raw materials) and the energy consumption decrease 7.03% and 7.87% respectively, greenhouse effect index reduces 30.5kg CO2 emission for cubic meter concrete. Due to the aggregate replacing volume ratio are generally controlled low in the pavement concrete, the effects of saving energy, lower energy consumption and reducing pollutants discharge will be more significant if the replacing ratio can be properly increased and a certain amount of mineral admixtures can be used.