Prediction of cyclic freeze-thaw damage in concrete structures based on response surface method

The initiation and growth process of cyclic ice body in porous systems are affected by thermo-physical and mass transport properties as well as by gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals reaches a significantly higher value under cyclic freeze-thaw conditions. Moreover, disintegration of concrete structures is aggravated by marine environments, higher altitudes, and northern areas. A serious concern for concrete engineers is that the property of cyclic freeze-thaw with crack growth and the deterioration, caused by accumulated damages hard to be identified by testing. In order to predict the accumulated damages by cyclic freeze-thaw, an optimized regression analysis by response surface method (RSM) is performed. Such important parameters for cyclic freeze-thaw-deterioration of concrete structures as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing are used to construct the limit state function of RSM. The regression equation fitted to the important deterioration criteria such as accumulated plastic deformation, relative dynamic modulus and equivalent plastic deformations served as the probabilistic evaluation of the performance to resist the structural degradation. The prediction of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw showed good agreements with the experimental results, showing that the RSM result can be used to predict the probability of failure for the accumulated damage by cyclic freeze-thaw using designer specified critical values. Hence, it is possible to evaluate the life cycle management of concrete structures by the proposed prediction method in consideration of the accumulated damage due to cyclic freeze-thaw. (c) 2007 Elsevier Ltd. All rights reserved.