Experimental investigation on the cracking process of primary and secondary cracks in thick concrete members

The decisive reinforcement of thick concrete members is often determined by the minimum reinforcement for crack control due to restraint stresses. In contrast to the heuristic design model in Eurocode 2, a mechanically sound methodology is only provided if the deformation compatibility is considered. However, such an approach requires a fundamental understanding of the cracking process. This study experimentally investigates the cracking process in thick reinforced concrete members. The results confirm that deformation compatibility is not only achieved by primary cracks. Secondary cracks have a significant contribution in absorbing the imposed deformation. Additionally, differences in crack width at the surface and at the reinforcement are analyzed, emphasizing the effect of crack tooth rotation. The findings provide key insights for reliable crack control based on deformation compatibility. Furthermore, a comparison with conventional crack width calculations for a reinforced concrete tie shows that neglecting crack tooth rotation can significantly underestimate secondary crack width.