Drying effect of polymer-modified cement for patch-repaired mortar on constraint stress

Deterioration mechanism due to drying and shrinkage of patch-repaired regions in reinforced concrete structures is analytically investigated. The moisture diffusion coefficient of the repair materials was determined by varying the drying temperature and the polymer-to-cement ratios of the polymer-modified cement mortar (PCM) in the experiment. It is found that the diffusivity of PCM increases in proportion to the polymer-to-cement ratio up to 10%. The constraint stresses due to drying at the repaired region were estimated by the couple-linear finite element analysis with respect to volumetric change, moisture diffusivity, water content and mechanical properties of the repair material. Based on the distributions of relative water contents and stresses, the effects of these parameters are discussed. The stress generated by drying and shrinkage was affected by substrate concrete, environmental condition and the properties of PCM. Of the repaired PCM tested, it is demonstrated that the CPM with 10% polymer-to-cement ratio generates the highest constraint stress.