Monitoring of early age shrinkage using image analysis and it's use in the repair of bridges

Abstract

The very early age shrinkage of concrete has significant effects on the behavior and durability of concrete in service, especially in the case of composite specimens comprising freshly cast low W/C cementitious materials on a hardened concrete substrate. Such specimens are commonly encountered in the repair of bridges in the form of cementitious overlays, replacement of spalled cover concrete and enlargement of concrete bridge members. A new method of monitoring early age shrinkage strains beginning 30 minutes after adding water to the mix is presented herein. Where applicable, shrinkage strains monitored using this technique were compared with readings obtained using the laser sensor technique. Based on the results obtained it was found that shrinkage strains monitored using image analysis compares well with and as expected, are higher than that measured using laser sensors. This new technique is capable of monitoring differential shrinkage in the composite specimens tested. © 2006 Taylor & Francis Group.