Speaker
Description
Calcium aluminate cement (CAC)-based coatings have demonstrated superior resistance to microbially-induced concrete deterioration (MICD) in wastewater infrastructures and are widely used to protect Portland cement-based concrete The key factor in the resistance of CAC lies in its chemical and microstructural nature. However, in the penalizing case of crack initiation within the underlying substrate, cracks might propagate into the coating and act as pathways for aggressive agents. This study investigates the behavior of a thin sprayed CAC-based coating, applied to new wastewater infrastructures, in the presence of cracks to understand the mechanisms that govern the coupled effect of cracks and biodeterioration. Representative cracks were generated in coated mortar specimens using a displacement controlled three-point bending test, producing different crack width ranges: 150-200 µm (complying the Eurocode 2 recommendations), 400-500 µm and beyond than 700 µm. These specimens were exposed to different campaigns of the BAC test, which reproduces the aggressive conditions encountered in sewer networks. During the exposure period, the leaching solutions collected from the exposed surfaces were analyzed followed by microstructural and chemical analyses of the structure using coupled SEM-EDS analysis. Coated specimens with crack widths > 400 µm showed a slight increase in Ca and Al leaching, yet leaching remained lower than in uncoated specimens. Moreover, SEM-EDS observations revealed the formation of newly precipitated phases within crack openings, composed mainly of calcium, aluminum and sulfur with molar ratios close to those of ettringite. These phases are suggested as a potential physical barriers, limiting the penetration of aggressive agents and contributing to the crack sealing of the coating in the stated conditions of exposure. This study not only provides insights into the performance of calcium aluminate-based coatings under biodeterioration in presence of cracks but also opens new perspectives on the crack healing potential of these materials in wastewater environments.
Affiliations
Imerys, 1 Rue Le Chatelier, 38090, Vaulx-Milieu, France
amr.aboulela@imerys.com
| Title | Dr. Amr Aboulela |
|---|---|
| Keywords | wastewater treatment plant, calcium aluminate cement, biodeterioration, durability, cracking |