Graduate Project
 

Assessing Durability of Concrete and Ettringite Accelerated Cementitious System

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  • The goal of the first part of this project was to investigate the influence of aggregate source and entrained air on the transport properties of concrete. Currently, there are several ASTM standards available that provide systematic procedures to evaluate mass transport properties of concrete. ASTM C642-13 (ASTM 2013), often referred to as the standard for measurement of pore volume, has been used in assessing durability. Another standardized test method, ASTM C1556-11a (ASTM 2016), allows determination of the apparent chloride diffusion coefficient of concrete, which is generally used to assess the resistance to chloride penetration and predict service life of concrete. To assess the durability of concrete in this project, these were the two experimental techniques used. Two aggregate sources, river gravel, and carbonate limestone, were investigated along with three water/cement ratios; with and without air entrainment. Results indicated that aggregate types influenced the porosity and chloride ingress of concrete. Limestone concrete showed a lower apparent diffusion coefficient than the river gravel counterpart. However, no significant effect was observed in the concrete mixtures due to the addition of air entrainment. The second goal of this project was to investigate the stability of ettringite accelerated cementitious systems subjected to different environmental conditions. Ettringite, the major hydrated phase of these systems, may have durability issue when subjected to environmental exposure. Ettringite accelerated systems have distinct advantages including rapid set and hardening as well as shrinkage compensation. Durability concerns have reason as these systems have moved from indoor application to interest in using these systems in outdoor applications, especially for rapid repair and construction. Until now, most of these systems were designed for indoor application (e.g., self-leveling floor screeds, tile adhesives, and grouts). Therefore, there is insufficient data on the performance of ettringite accelerated system, particularly as repair material in transportation infrastructure. Recently, the durability of portland cement rich ettringite accelerated systems was determined for different exposures. However, in this research the focus is on calcium aluminate cement rich systems. In this research, the cementitious systems consist of portland cement, calcium aluminate cement, and calcium sulfate were exposed to four environmental conditions. For completeness, both portland cement rich and calcium aluminate cement rich systems were evaluated to enable direct comparison. The dimensional stability, mechanical properties, and mineralogical compositions were examined in this study.
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file details Sarkar_Technical_Report_Final.pdf 2019-07-31 Public Télécharger