Research On Performances And Preparationof Self-compacting Slipform Concrete

Slip-forming technique is a kind of rapid paving method. But in the practicaloperation process, the compaction of concrete need add additional high frequencyvibration and the mechanical movement of formwork. Improper operations oftentimesresult in segregation of aggregates and a significant reduction of entrained air in theconcrete, leading to the reduction of concrete service life and engineering safety.Therefore, the research presented in this paper is focused on the modification oftraditional self-consolidating concrete and the application to the slip-form pavingwithout internal or external vibration. Such construction method can obviously improvethe homogeneous and long-term durability of concrete pavement, and it is veryimportant for both theory and practical application.By adding some functional clay materials, the improved self-consolidatingconcrete can be applied to the slip-form paving. And the min slip-forming apparatus andits operating parameters was optimized in this research. The results show that, in orderto realize the slip-form paving of concrete without internal or external vibration, theslump of concrete mixture should be controlled between210mm and250mm, and theslump flow should be between350mm and420mm. For the slip-forming apparatus,the slip-forming speed should be about0.25m/min, the concrete filling quantity is60%～80%of the height of the vertical mold and the counter weight is28.6kg more orless.The influences of clay materials and mineral admixtures on the molding qualitywas studied and the edge stability and the surface texture of the freshly cast concreteslab were advanced. The results show that the concrete performs well for theslip-forming with any vibration when the dosage of clay material is1.0%～1.5%. Onthe basis of clay addition, the concrete slab prepared by slip-forming without anyvibration has a smaller wit edge slump and a better surface evenness when adding30%fly ash. By comparing mechanical properties and durability of free vibration slip-formconcrete and traditional slip-form concrete, compressive strength of free vibrationslip-form concrete at28and56days is increased to different degrees. By adding somefunctional clay materials, the flexuous strength of the improved self-consolidatingconcrete at56days is increased5.0%～7.0%. Moreover, the concrete performs better,the flexuous strength higher. The addition of clay improves the abrasive resistance ofconcrete. The wear content per unit surface of concrete is lower than1.4kg/m2after60times of rotating rub, while the traditional slip-form concrete is above1.6kg/m2.Compared with traditional slip-form concrete, the frost resistance of free vibrationslip-form concrete behaves better, especially for the mix of1.5%clay1+30%fly ash,1.5%clay1+40%slag and1.0%clay2. The mass loss and dynamic elastic modulus loss are very low after175cycles of freeze-thaw. However, traditional slip-formconcrete and self-compacting concrete damaged seriously after150cycles offreeze-thaw.By comparing to the traditional slip-form concrete and self-consolidating concrete,the pore structure analysis of cement paste show that the improved concrete has areduced porosity by about20%, smaller size of median pore and the most probable poreget smaller. The content of micro pores gets fewer obviously, and the pore structureimproved obviously.