Study On Design,Performance And Mechanism Of Nano Modified Concrete Pavement Materials

Cement concrete pavement has occupied a large proportion of China's high grade pavement for its irreplaceable advantages of stronger bearing ability,longer service life and cheaper cost in comparison to the asphalt concrete pavement.Having a high surface chemical energy and filling effect due to their small particle size and large specific surface area,nano-materials have great potential in concrete application.Fly ash,as a kind of industrial waste,can not only reduce the high-consumed cement dosage but also improve the workability of mixture and the strength of hardened cement paste.In this thesis,two kinds of nano-materials--nano-silica and nano-silicon carbide--and fly ash were added in ordinary concrete to prepare the nano-concrete.First of all,the influence of fly ash amount on concrete's workability and mechanical properties was investigated and the optimal dosage of fly ash in pavement cement concrete was determined,then mix proportion of nano-concrete was determined based on the mix proportion of fly ash concrete.Besides,the effects of type,amount and mutual proportion of nano-material on flexural strength and compressive strength of hardened cement paste were studied respectively through cement mortar test,and the micro morphology of paste-aggregate interfacial zone of nano-modified mortar was observed by SEM test.The improving mechanism on nano-modified cement paste's mechanical properties was analyzed compared with the micro morphology of ordinary mortar.The results show that modest adding of nano-materials can improve the compressive strength and flexural strength of concrete,the optimal dosage of nanoSiO2 is 2% while which of nanoSiC is 3%.The main reason is that the distribution of gel particles being changed and tiny pores being filled with by nano-materials makes concrete denser.Finally,the abrasion resistance,drying shrinkage,carbonation resistance of nano-concrete were studied by experiment and the influence mechanism was analyzed.The results show that firstly,adding of nano-materials can significantly improve the abrasion resistance of concrete,the wear loss of concrete containing 3% nanoSiC decreases 68.75% than that of ordinary concrete.Secondly,adding of nano-materials increases the drying shrinkage rate of concrete.Thirdly,the carbonation performance of concrete containing nano-materials can be improved.