Valorisation des sédiments portuaire comme ajout cimentaire

Abstract

In Quebec, 450000 m3 of sediments are dredged each year in various harbour. The management of these dredged sediments has become a major issue both economically and environmentally. The main objective of this study was to assess the possibility of using these sediments as cementitious additives. The sediments were subjected to a drying process, then crushed and subsequently calcined at temperatures ranging from 600 °C to 1000 °C. The physical, chemical, and mineralogical characteristics were determined. The analysis of the physical characteristics revealed that the studied sediment is a highly plastic and expandable clayey silt. To evaluate the mechanical and pozzolanic performances, 20% of the raw and treated sediments were considered. The reactivity of the sediments was evaluated using isothermal calorimetry and thermogravimetric analysis (TGA) on the R3 paste. Metakaolin and quartz are respectively reactive and inert references in the R3 (Rapid, Relevant, and reliable) paste, and general use cement (GU) represents the reference in the mortar. The compressive strength was measured at 1, 7, 28, and 112 days, and the chemical activity was quantified after 7 days of hydration of the R3 paste. Furthermore, the impact of sediment substitution rates on compressive strengths was analyzed. According to the results of the mechanical performances, mortars with raw sediments (SB) and sediments calcined (SC) at 600 °C, 700 °C, and 800 °C (except 900 °C, 1000 °C) developed similar compressive strengths to the reference mortar at 7, 28 and 112 days when 20% of the cement was substituted by the sediments. However, it decreased linearly as the sediment substitution rate increased. The TGA results showed that the reactivity degree of the sediments varied between 40 % and 50 % depending on the consumption of Portlandite. Furthermore, the non-calcined sediments produced a low amount of heat (78 J/g), unlike the calcined sediments which produced moderate heat (110 - 130 J/g). Based on all the experimental results, the pozzolanic activity of the raw and thermally treated sediments is considered moderate. The thermal treatment had only a slight effect on the pozzolanic activity. The conclusions of this study are encouraging as they suggest that harbour dredging sediments, considered as waste, could be used as a sustainable and environmentally friendly construction material. This approach could contribute to the sustainable management of harbour dredging sediments while offering an economic and ecological solution by replacing, under certain conditions, up to 20% of the untreated sediments. Additional concrete durability tests are required to confirm these promising results.

Date	24 Aug 2023
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Claudiane Ouellet-Plamondon (Supervisor)