Early Age Shrinkage Monitoring of High Performance Cementitious Mixtures using Monolithic and Composite Prism Specimens

LADO RIANNEVO CHANDRA

Publication

Early Age Shrinkage Monitoring of High Performance Cementitious Mixtures using Monolithic and Composite Prism Specimens

LADO RIANNEVO CHANDRA

Abstract

For the last three to four decades, the early age shrinkage of high performance cementitious mixtures has become a concern among engineers. Despite this fact, information about early age shrinkage is still not well documented in the literature. This thesis firstly focused on issue pertaining to the selection of the starting point or the ?time zero? value (i.e. TZV) to be used for early age shrinkage monitoring of high performance cementitious mixtures cured under sealed and unsealed curing conditions. Following the issue of TZV for early age shrinkage monitoring, an improved image analysis technique capable of monitoring early age shrinkage strains with respect to the depth from the top surface of cementitious prism specimens during the first 24 hours after adding water to the mixture was described in the present study. The improved image analysis technique can be applied for either sealed prism specimens (generally used for autogenous shrinkage monitoring) or unsealed prism specimens (typical of those used for early age drying shrinkage monitoring) with acceptable accuracy. Once the improved image analysis technique was established, the technique was used to investigate the influence of some constituent materials and mixture properties such as superplasticizers, water-to-cementitious ratio, aggregate volume, and silica fume on the development of shrinkage strains within prism specimens exposed to a dry environment from an early age. With the knowledge of early age shrinkage strains monitored on monolithic prism specimens, the study was extended to investigate the influence of substrate preparation on the early age shrinkage strains and cracking (de-lamination) during the first 24 hours after adding water to the mixture of newly cast cementitious materials in composite prism specimens. The findings provide a better understanding of early age shrinkage of high performance cementitious mixtures cast either as a monolithic or as a two layer composite prism specimen.