The Study On Road Performance Of High Performance Porous Cement Concrete For Tunnel Pavement

Laying cement concrete pavement with good performance on anti-slide and noise reduction in tunnel could improve the security and comfortableness of the whole tunnel. According to the environmental characteristics of the tunnel pavement and focus on the main problem of cement concrete pavement such as fast anti-slide structure reduction and large driving noise, this paper carried out the research on porous cement concrete material which could be properly used as tunnel pavement and made the pavement meet not only the requirement of workability and mechanical strength, but also the service performance of anti-slide, noise reduction and draining in order to make driving comfort and safety.This author improved the strength and other properties of porous cement concrete through promoting the performance of cement slurry. Mixing fly ash and silica fume could significantly improve the strength of cement slurry. The best inner and extra mixture volume of fly ash and silica fume was found out by comparison of compressive and flexural strength of cement slurry specimens. The best inner mixture volume was6%, while extra mixture volume was4%. The best inner mixture volume was20%, while the best of outer was10%. Within the system of double mixing fly ash and silica fume, the optimum inner mixture volume of silica fume and fly ash was10%,6%, while outer was10%,4%. The specimens which extra mix with silica fume or both fly ash and silica fume, had the most advantage in strength. In order to further study the relationship between the microstructure and macroscopic properties of porous cement concrete, this paper analyzed the modified mechanism of fly ash and silica fume on cement paste by scanning electron microscopy (sem) test and pore structure analysis experiment on mercury intrusion measurements. From above result it was explored that the fly ash and silica fume could change the porosity and the characteristics of space and pore size distribution. The compactness of cement slurry was improved and harmful pore quantity was reduced, which indicated that fly ash and silica fume especially the double mixed system of them could significantly improve the microstructure of cement slurry.The mechanical properties of porous cement concrete were significantly improved by silica fume and fly ash mixing, especially the double mixed system which increased the90d compressive and flexural tensile strength to32.13MPa and4.54MPa, modulus of elasticity to9137.3. Through scanning electron microscopy (sem) test on the Aggregates-Cement paste interfacial transition zone, it was discovered that mixing fly ash and silica fume could inhibit the oriented growth of Ca(OH)2and ettringite, improve the compactness of interfacial transition zone, made for the advantage of mechanical properties. Furthermore, the road performance of porous cement concrete was researched through water seepage test, pendulum frictiograph test, sand patch test and freeze-thaw circulation test. According to the test result above, it was showed that the water permeability coefficient ranged from559.60ml/min to3619.5ml/min which indicated good draining ability. Comparison with that of normal cement concrete road, the friction coefficient increased50%and the texture depth was between0.9mm and1.17mm which showed better anti-slide performance. After freeze-thaw circulation, there is not any exfoliation on specimens surface and loss rate of compressive strength ranged from21.1%-24.8%, which indicated that the porous cement concrete pavement had superior frost resistance.