A new look at the control of volume change cracking of base restrained concrete walls

Volume change cracking is a widespread problem in base restrained concrete walls. In such walls the degree of restraint is not uniform, but depends on the wall length/height ratio and on the position of the point in consideration within the wall itself. A two dimensional finite element analysis was carried out on walls with different L/H ratios to determine the variation of restraint within these walls. Also crack width was proved to be directly related to the change of restrain in the wall before and after cracking. From the restraint factors obtained, idealized diagrams of the change of restraint were prepared. These diagrams were used to determine the exact amount of steel reinforcement that is required for the control of volume change cracking in the walls. Steel reinforcement was provided in positions where it is really effective in controlling these cracks. Therefore, variable steel quantities were used in the walls. This led to the effective reinforcement concept. This concept and the proposed method for the control of cracking in walls were tested against the cracking data obtained from 37 full size walls and 8 experimental walls. The comparison showed good agreement between the theoretical and observed width of cracks.