| In recent years, the early constructed cement concrete pavements have damagedseriously with the increase of traffic volume and load, failing to meet the urgent need for fastdevelopment of economy and public demand for traffic capacity and comfort of expressway.Cement concrete pavement with asphalt overlay (CCPAO) is a common used measure toimprove the pavement performance and extend the pavement life. A lot of domesticresearches have been carried out on CCPAO, however, there are still lacks of deep study onthe comprehensive technology of this compound pavement. Some factors, such as halfwaytreatment of old cement concrete pavement, unreasonable anti-crack measure, imperfection ofoverlay design method, etc, lead to unsatisfied performance of CCPAO. Considering theoptimization design of material composition and performance and the mechanicalcharacteristics of the compound pavement structure, this paper, through a lot of experimentsand theoretical analysis, focused on the study of the material and structure design of CCPAOand aimed to improve the comprehensive performance of the compound pavement so as toboost the development of this technology in China.Effective treatment of the gap under the concrete slab with grouting is an importantpremise to ensure the favorable performance of CCPAO. Aiming at the problems in groutingtechnology, this paper carried out experiments to study the composition design of groutingslurry. The influences of different material components and various types of admixture on themechanical and performance properties, such as grouting slurry strength, flowability, viscosity,expansion ratio, bleeding, ect. On base of that, the control indexes and technical specificationfor the composition design of grouting slurry and the quality evaluation indicators forgrouting were also proposed, which offer good guidance for the grouting design underconcrete slab.By using finite element analysis the mechanical behavior of CCPAO was studied. Theinfluences of traffic load, depth of asphalt overlay, modulus of stress absorbing layer on thestress and strain of CCPAO were analyzed. Additionally, the mechanical characteristics of thecompound pavement with a new type of reflection crack-resisting structure were studied. Theresults showed that the new type of reflection crack-resisting structure could decrease the loadstress of the compound pavement in a certain extent and could obviously decrease thetemperature stress of the compound pavement, thus in turn effectively preventing theappearance of reflection crack due to temperature change. By analyzing the monitoring datafrom ShanMei expressway maintenance project, the actual mechanical behavior laws of the compound pavement structure were verified, which offer theoretical base for the optimizationdesign of CCPAO.Depending on the CCPAO in Meihe expressway, the impacts of different types of interlaytreatments on the interfacial bond strength between the cement concrete pavement and theasphalt overlay were verified. Considering the insufficient anti-shear strength of commonbonding layer material, a new type of water proof and bonding material i.e. PCMA, wasdeveloped and the mechanism was illustrated. Additionally, the construction techniques andindexes were also put forward. Actual engineering application and performance determinationshowed that PCMA had the advantages of high anti-shear strength, convenient constructionand no need for spread of crushed stones.Using fatigue test, the influences of three types of asphalt mixtures and fourcrack-resisting measures, e.g. glass fiber grilling, geotextile, SAMI layer, and polyester fiber,on the fatigue performance of CCPAO were studied. Verification was also carried out for thedifferent crack-resisting measures with actual projects. The results showed that SAMI layermanifested superiority in terms of crack resistance of CCPAO and polyester fiber contributedto the improvement of crack resistance for asphalt mixture.The performance properties of asphalt mixtures using various PG grades and aggregategradations were studied with experiments. The results showed that the dynamic stability ofmixture with PG82modified asphalt was nearly double than that of mixture with PG70. Andthe fatigue life of the former one was two times greater than that of the latter one. By usingthe PG82modified asphalt, developed bonding material, new type of reflection crack-resistingmeasure and optimized mix design, the performance of the compound pavement in ShanMeiexpressway was effectively improved and the corresponding measures have good engineeringperspective. |
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