Fresh Concrete Properties Required for Vertical Slip-form Concrete

Abstract: The guidelines available in the present concrete mix design standard IS-10262-2019 [2] are silent about the special mix proportion criteria for slip-form concrete. The slip-form concrete is subjected to dynamic loads in the fresh state due to the movement of the slip-form panel over the fresh concrete. In current practice, particularly in power plant industries where RCC chimneys are required, concrete mix design is often carried out by a third party based solely on hardened concrete design strength criteria. However, such proportioning guidelines as per IS-10262-2009 [2] are suitable only for static concrete pouring operations. For slip-form concrete, special criteria for fresh concrete is needed, like adequate shear strength of the cover concrete to be self-sustaining against the lifting friction of the slip-form panel during its movement, as well as to prevent surface problems in the RCC chimney shell during construction using the slip-form technique. In this research work, addressing real execution problems of RCC chimney shell surface issues, it has been concluded that the greater the shear strength of fresh concrete, the more resistant it will be to the lifting friction of the slip-form panel, resulting in better surface quality of the chimney shell and fewer surface problems. The research also concluded that various properties of concrete ingredients directly influence the shear strength of the concrete and plays an important role in preventing surface problems of the chimney shell during construction.