Moisture Transport and Shrinkage Stress in Polymer Based Repair Materials

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Title: Moisture Transport and Shrinkage Stress in Polymer Based Repair Materials

Author(s): M.K. Rahman

Publication: Special Publication

Volume: 278

Issue:

Appears on pages(s): 1-22

Keywords: Polymer-based repair mortar, moisture diffusion, drying, shrinkage, moisture diffusivity, finite element, COMSOL, repair layer, shrinkage stress.

Date: 3/1/2011

Abstract:
Moisture transport, shrinkage and creep in repair material have a profound influence on long-term durability and serviceability of patch repair in concrete structures. In the process of drying of a newly cast repair mortar, the moisture diffuses within the domain and convects at the bounding surfaces resulting in hygral gradient across the depth and coupled drying shrinkage. This leads to the generation of tensile stresses in the repair layer, and cracks are developed at the surface of patch repair and at its interface with the parent concrete. Polymer-based repair materials also undergo significant shrinkage and tensile creep, which influences the stresses and cracking in the repair overlays. Experimental investigations including strength tests, moisture loss, shrinkage, and creep measurements were conducted on four selected repair mortar including two polymer-based repair mortars. These tests provide the parameters required for computation of stresses and prediction of cracking in repair overlays. Nonlinear finite element based diffusion analysis and experimentally obtained drying curves can be used to develop the empirical moisture diffusivity law and quantification of the surface transfer coefficient which is used for prediction of moisture loss in a repair layer. Multiphysics finite element software COMSOL provides a convenient tool for computation of moisture transport and associated evolution of stresses due to shrinkage in a composite system in which a polymer based repair mortar is used for patch repair of a concrete member.