Research On C60 Self-compacting Concrete For Non-autoclaved Sheet Pile Production And Its Performance

At present,Chinese economy is in a high-speed developing period,urbanization speed is accelerating,and the construction of infrastructure and urbanization is vast.As a new retaining structure of prefabricated concrete pile of stopping soil,U-shaped prestressed concrete sheet pile is widely used in construction foundation pits,subway projects,municipal engineering,highway engineering and coastal engineering,because of its structural advantage and cost advantage.The self-compacting concrete can flows well to dense owing to its gravity without vibrated at the pouring process,and can easily and uniformly fill well into complicated components.U-shaped is a new structure of supporting and retaining soil pile,which holds good structural anti-bending capacity and large retaining soil area.However,the common concrete can not fill well into this structure due to smaller cross-sectional area and special structural characteristics of U-shaped sheet pile,and the problems of quality occurred.The different forms of sheet pile with good quality can be prepared by self-compacting concrete.In this paper,self-compacting concrete with the compressive strength grade of C60 was prepared by cement,sand,gravel,fly ash,slag,and polycarboxylate superplasticizer.The effect of mix parameters,workability,and self-compacting to mechanical properties of C60 self-compacting concrete were studied,and the optimum mix proportion was obtained.The curing system of U-shaped slab pile prepared with C60 self-compacting concrete was obtained by adjusting the time of static stop,heating and constant temperature.The results showed that:(1)In order to achieve good workability,compressive strength and economic reasonability,the optimum mixture ratio for C60 grade of concrete is 550 kg/m3 of cementitious materials,2.8%of water reducing agent,0.32 of water cement ratio,9%of fly ash,20%of slag and 45%of sand ratio.(2)The static stopping time of concrete has an important effect on the initial structure of concrete.When the heating rate was constant,the strength grade of concrete increased with the static stopping time.The compressive strength of concrete linear increased with the static stopping time when the static stopping time was less than 8 hours,but the range of increase of compressive strength decreased gradually with the increasing of static stopping time of concrete.The static stopping time shall not be less than 6 hours.(3)The compressive strength of concrete decreased with the increasing of heating rate,and the higher the heating rate was,the greater the decrease was.The compressive strength of steam curing concrete was close to that of the standard cured concrete when the heating rate was 20 ?/h.The concrete strength grade was greater than C60 when the heating rate was less than 40?/h.when the heating rate was 60?/h,the compressive strength of steam curing concrete dramatically decreased,and was less than 10MPa compared with the heating rate was 20 ?/h.(4)The compressive strength of concrete increased with the increasing of heating time,but the compressive strength of concrete increased slowly when the heating time was more than 8 hours.The compressive strength of concrete increased at first and then decreased with the heating temperature increasing.The compressive strength of concrete reached the highest point when the temperature of steam curing was 80 ?.(5)The steam curing concrete was endowed with high compressive strength and chloride permeability when the static stop time was 6?8 hours,the heating rate was 40?/h,the heating temperature was 80?,the constant temperature time was 8 hours,and then the temperature decreased to room temperature in 4 hours.The secondary steaming was beneficial to improve the compressive strength of concrete mixed with slag powder,especially when the dosage of slag powder was higher.