Microstructural Evolution within the Interphase between Hardening Overlay and Existing Concrete Substrates

Abstract

This article presents the microstructural evolution within the interphase between a hardening overlay made of cement mortar and an existing concrete substrate. The substrate has been treated using four methods, due to which different surfaces were obtained: a raw surface, a surface formed after contact with the formwork, a grinded surface, and a shotblasted surface. Special focus is placed on the results of the microporosity within the interphase zone (IZ) using X-ray micro computed tomography (micro-CT). The microporosity profiles obtained from the micro-CT images have been used to assess the nature of the IZ between the hardening overlay and the existing concrete substrate. It has been shown that microporosity and the number of pores in the concrete within the IZ increases during the hardening time of an overlay made of cement mortar. It also depends on the applied surface treatment method. However, no significant changes in the microporosity of the existing concrete substrate have been noted.

Keywords

• concrete
• surface treatment
• cement mortar
• overlay
• substrate
• microporosity
• microstructure
• interface
• interphase
• X-ray micro computed tomography