Durability scaling of cracking in HPC structures subject to hygromechanical gradients

The cracking of concrete is one of the main causes of limited life spans of concrete structures. Besides external actions, cracking can be induced by phenomena involving hygromechanical coupling. Such phenomena involve two ty pes of scale effects-one related to local or global diffusion gradients, th e other to size effects on cracking in concrete structures. This paper pres ents results of a research program on the durability of nuclear cooling tow ers, with minimum reinforcement, constructed with normal and high-strength concrete, when subjected to hygric and thermal gradients. To this end, a co mbined experimental-numerical approach is applied involving 1:2 scale struc tural tests and finite element durability analysis using a probabilistic cr ack approach. The model is presented and then validated with experimental d ata. Finally, from 1:1 scale numerical analysis of the cracking due to dryi ng, it is shown that the structural durability performance, in terms of cra ck opening, is governed by the evaporable water in concrete; it scales both the magnitude and the time of drying, and thus the crack opening and its l ong-term propagation. At higher moisture content, this durability performan ce is only slightly influenced by a high strength concrete matrix or by an increased steel reinforcement.