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COUPLED MODELING OF CEMENT PASTE DEGRADATION BY MICROBIAL ACTIVITY

Abstract : A bioleaching test of ordinary Portland cement pastes by Aspergillus niger fungi during 15 months is modeled with the reactive transport code HYTEC assuming thermodynamic equilibrium. Modeling indicates that the biogenic organic acids strongly accelerate cement degradation by acidic hydrolysis whereas their complexation of aluminum have a potential effect on the secondary gel stability. The deepest degradation front corresponds to portlandite dissolution and decalcification of calcium silicate hydrates. A complex pattern of sulfate phases dissolution and precipitation takes place in an intermediate zone. The outermost altered zone consists of alumina and silica gels with calcite precipitation at its internal boundary and possible calcium oxalate formation at its external boundary. The coupling of (bio)chemistry, porosity and diffusion evolutions is a key step. The modeling accurateness of Ca leaching, pH evolution and degradation thickness is enhanced in a consistent manner while considering increase of diffusivity in the degraded zones. Although the calculated mineralogical fronts remains too sharp, claiming for a kinetic approach, this study demonstrates that reactive transport models can be applied to assess the durability of cementbased materials subjected to bioalteration
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https://hal-mines-paristech.archives-ouvertes.fr/hal-00568715
Contributor : Pascale Nalon <>
Submitted on : Wednesday, February 23, 2011 - 2:01:58 PM
Last modification on : Thursday, September 24, 2020 - 4:34:09 PM

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  • HAL Id : hal-00568715, version 1

Citation

Laurent de Windt, Philippe Devillers. COUPLED MODELING OF CEMENT PASTE DEGRADATION BY MICROBIAL ACTIVITY. Concrete in Aggressive Aqueous Environments, 2009, France. pp.196-203. ⟨hal-00568715⟩

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