Physicochemical properties and durability of cementitious mortars modified with sugarcane bagasse ash

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Résumé

Cementitious mortars face durability problems in aggressive environments, which reduces the lifespan of cement buildings. The objective of this study is to investigate the physicochemical and durability properties of cementitious mortars with added sugarcane bagasse ash (CBCS). The ashes were produced by calcining sugarcane bagasse at temperature ranging from 600 to 750 °C for 2 or 3 hours. The microstructure and the pozzolanic activity of the ash were investigated. Mortars were then manufactured by partially replacing 0-25 wt % of the cement with ash. Their physicochemical properties, such as bulk density, setting time, expansion, and durability in an acidic environment, were studied. The results show that the ash has irregularly shaped grains and high porosity. They are rich in amorphous silica (58.37 to 75.91 wt.%) and have pozzolanic indices above the minimum value of 75 % required by ASTM C618 for pozzolanic materials. A decrease in density and an increase in the initial and final setting times of cement pastes modified with ash are observed. The addition of ash did not cause significant expansion of the pastes. Durability studies in aggressive environments have shown that mortars modified with bagasse ash are more resistant to acid action due to the increased presence of calcium silicate hydrates (CSH), resulting from the pozzolanic reactivity between portlandite (CH) produced during cement hydration and the amorphous silica in bagasse ash. The use of these ashes as cement additives is a solution to improving the lifespan of cement buildings.

Mots-clés

sugarcane bagasse ash, cement mortars, pozzolanic reactivity, durability, aggressive environments, hydrated calciumsilicates