Title: Free Shrinkage Strains in Concrete Overlays

Author(s): Luis Orta and F. Michael Bartlett

Publication: Materials Journal

Volume: 111

Issue: 3

Appears on pages(s): 263-272

Keywords: diffusivity; drying shrinkage; Fick’s Law; internal humidity; time dependence

DOI: 10.14359/51686566

Date: 5/1/2014

Abstract:
Concrete decks are commonly rehabilitated using concrete overlays. Overlay shrinkage is restrained at the interface with the substrate. An analytical method is presented to compute the distribution of internal humidity and free shrinkage strains in the overlay and substrate for bridge decks with solid rectangular cross sections and therefore overcomes the shortcomings of generic shrinkage models. Drying humidity is modeled using Fick’s Second Law and the concrete diffusivity as a function of the internal humidity. The prediction of internal humidity is validated using experimental data obtained by others. The distribution of free shrinkage strains through the overlay thickness is strongly nonlinear with localized maxima at the top of the overlay and at the interface with the substrate. Large swelling strains also occur in the upper fibers of the substrate. Thin overlays develop large free shrinkage strains rapidly, whereas thick overlays produce large swelling strains in the substrate.