Assessing the zero-stress temperature in high performance concrete at early age

Currently, there is no reliable approach to quantify the continuous evolution of the zero-stress temperature (T_z), despite its well-recognized significance in determining the risk of cracking. In this paper, a novel analytical approach is proposed to determine the temporal evolution of T_z profiles based on the temperatures corresponding to points at which the total stresses are zero. An experimental investigation is performed using an advanced Temperature Stress Testing Machine to illustrate this approach and an in-depth assessment of T_z is presented. The proposed approach allows to determine the continuous T_z profile in concrete subjected to any arbitrary temperature profile, compared to existing methods that can identify only discrete points. Such obtained T_z profiles tend to establish during the first heat-cool cycle within several days after placement and remain essentially constant or even slightly increase over time. On that basis, the practical significance and implications of such T_z profiles are highlighted.