Autogenous deformation and chemical shrinkage of high performance cementitious systems

Graduation date: 2011In the past ten years, renewed research interest has shown the benefits of internal curing by incorporating saturated lightweight fine aggregate (LWFA) in high performance concrete (HPC). As a result, the technology of internal curing has steadily progressed from laboratory studies to field applications. To determine the optimum LWFA content, information about the propensity for shrinkage in the cement paste, specifically the\ud chemical shrinkage value, is needed. However, there is a lack of information on how to determine the ultimate chemical shrinkage value for HPC with supplementary cementitious materials (SCMs) and/or shrinkage reducing admixture (SRA). The purpose of this thesis was to identify a simple procedure to determine ultimate chemical shrinkage values for given concrete systems with SCMs and/or SRA. Modifications to the ASTM\ud C1608 (Standard Test Method for Chemical Shrinkage of Hydraulic Cement Paste) were investigated up to a 14 day age. Neat paste (cement only), as well as binary and ternary systems, were measured to investigate the influence of SCMs and SRA on chemical shrinkage. Based on the observed data, an experimental prediction model was adopted and verified to estimate ultimate chemical shrinkage values for portland cement systems\ud containing SCMs and/or SRA. The model agreed well with the obtained data and simplified the existing method of determining the ultimate chemical shrinkage value.\ud \ud Another purpose of this research was to investigate the effect of SCMs and SRA on autogenous deformation of HPC for which a buoyancy method was used. The findings provided insight into the mechanisms behind autogenous shrinkage and effective strategies to reduce autogenous shrinkage.\ud \ud Calcium aluminate cements (CACs) were also investigated as part of this research project as a rapid repair material for applications, such as high performance concrete bridge decks. Chemical shrinkage and autogenous deformation of CAC binders were tested in a similar manner to the OPC systems in this study. It was observed that GCX paste cured isothermally at 38 °C exhibited expansion with a particular shape of chemical shrinkage\ud development curve. An X-ray diffraction suggested that the expansion might be related to the conversion process indicating that chemical shrinkage may be used as a predictor of conversion processes for CAC systems in isothermal condition