Early-age shrinkage strains versus depth of low water-cement ratio mortar prisms

Abstract

This paper presents an experimental study using an image analysis technique to monitor the variation of early-age shrinkage strains with a depth of ordinary portland cement (OPC) mortar prism specimens exposed to ambient conditions of 30 ± 0.50°C (86 ± 1°F) and 65 ± 2% RH. Starting from as early as 30 minutes after adding water to the mixture, shrinkage strains were measured at various depths from the top trowelled surfaces of OPC mortar prism specimens cast with a water-cement ratio (w/c) of 0.25, 0.30, or 0.35. The effect of the time zero value (that is, TZV) to initiate early-age shrinkage measurements and the gauge length used were also investigated. The results show that the absolute early-age shrinkage strains vary significantly with the depth from the top exposed surface of unsealed mortar prism specimens tested. In addition, the TZV and gauge length adopted significantly affect the absolute early-age shrinkage strain values monitored. Copyright © 2010, American Concrete Institute. All rights reserved.