Title: Effect of Carbonation on Mechanical Properties and Microstructure of One-Part- Geopolymer based on Thermo-Mechanical-Synthesis Sediments Fy Ash Mix

Author(s): Elie Mahfoud, Khadim Ndiaye, Walid Maherzi, Salima Aggoun, Nor-Edine Abriak, Mahfoud Benzerzour

Publication: Symposium Paper

Volume: 362

Issue:

Appears on pages(s): 616-629

Keywords: one-part-geopolymer, sediments, fly ash, durability, carbonation, mechanical properties

DOI: 10.14359/51741016

Date: 6/14/2024

Abstract:
This study aims to determine the carbonation effect on mechanical properties and microstructure of a one-part-geopolymer based on a thermo-mechanical-synthesis sediments-fly ash mixture. Four mixtures containing 0, 15, 30, and 50% sediments and optimized in terms of mechanical performance were exposed to accelerated (3% CO₂) and natural carbonation. Carbonation depth and pH of mortars (4x4x16 cm²) were measured according to CO₂ exposition time. Carbonation products were identified by XRD on pastes. The carbonation effect on geopolymer properties was studied by SEM-EDS observations and the mechanical strength investigation. Carbonation depth was between 4 and 6 mm with difficulty in detecting areas of partial carbonation using phenolphthalein. Nahcolite (sodium bicarbonate) is mainly the accelerated carbonation product leading to a pH decrease but still above the steels depassivation threshold. Secondary products are natron (sodium carbonate) and calcite which appear with sediment incorporation. Carbonation products with binding properties have closed pores and cracks, and consequently improved mechanical performance.