Degradation modeling of concrete submitted to biogenic acid attack

Abstract

Biodeterioration of concrete,which is very common in sewer system, results in significant structure degradation. The process can be described by the 3 following steps: Concrete surface neutralization providing appropriate environment for sulfur oxidizing bacteria (SOB) to grow, sulfuric acid (H2SO4) production by SOB on concrete surface and chemical reaction between H2SO4 and cement hydration products. A reactive transport model is proposed to simulate the whole biodeterioration processes of concrete in contact with H2S gas and SOB. This model aims at solving simultaneously transport and biochemistry/chemistry in biofilm and concrete by a global coupled approach. To simulate the neutralization process, the absorption of H2S gas, the dissolution of portlandite (CH), the decalcification of calcium silicate hydrates (C-S-H) and the precipitation of calcium sulfide (CaS) are considered. To obtain the amount of biogenic acid, the production rate of H2SO4 by SOB is calculated via a set of simplified models governed by pH. Coupling with the modeling of H2SO4 degradation process, the biodeterioration depth and the solid composition evolution could be predicted. A laboratory experiment reported in literature is simulated and the simulation results are compared with experimental results

Construction d’outils opérationnels pour l’évaluation du comportement des matériaux cimentaires en réseau d’assainissement

“…Une autre étude propose la simulation de l'attaque par l'acide sulfurique grâce à un modèle basé sur la diffusion-réaction, dans le but de prédire le taux de corrosion des matériaux cimentaires [CHALUPECKY et al, 2012]. Un modèle de transport réactif [HYTEC, VAN DER LEE et al, 2003 ;DE WINDT et DE VILLIERS, 2010] YUAN et al, 2015 ;GRANDCLERC et al, 2018].…”

“…Ce modèle prend en compte les interactions chimiques entre ces différents acides organiques et les hydrates du matériau cimentaire considéré (basé sur des ciments Portland). Un autre modèle a été proposé[YUAN et al, 2013 ;YUAN et al, 2015] pour simuler l'attaque par l'acide sulfurique d'un matériau cimentaire à base de ciment CEM I. Ce modèle se fonde sur le modèle HYTEC [DE WINDT et De VILLIERS, 2010] et prend en compte la dissolution des principaux hydrates d'un ciment CEM I (portlandite et C-S-H) et la précipitation des produits de détérioration (gypse) formés lors de l'attaque par l'acide sulfurique. Il tient compte des équilibres chimiques associés à des constantes thermodynamiques, ainsi qu'au transport des différentes espèces lors de l'attaque acide.Le modèle de biodétérioration mis en place dans le cadre de cette étude se base principalement sur le modèle précédemment décrit[YUAN et al, 2013 ;YUAN et al, 2015].…”

Evaluating the efficacy of antimicrobial additives against biogenic acidification in simulated wastewater exposure solutions

“…The process begins with the production of hydrogen sulfide (H 2 S) under anaerobic conditions by reduction of sulfate ions (SO 4 -2 ) present in the wastewater by anaerobic sulfate reducing bacteria (SRB) residing below the waterline [4]. The formation of aqueous hydrogen sulfide (H 2 S aq ) in wastewater is followed by its release into the headspace above the waterline as a gas, H 2 S g , which then dissolves in the moist layer on the surface of the inner walls of the concrete structure as H 2 S aq [5][6][7][8]. Hydrogen sulfide on concrete could either remain as it is or could be converted chemically to elemental sulfur, sulfite, and thiosulfate depending on the environmental chemical conditions.…”

Avaliação Dos Mecanismos De Degradação Do Concreto Por Ataque De Ácido Sulfúrico

“…Pesquisas mais recentes [8,15] associam a queda do pH ao processo de dissolução por meio da ação do H2S. Porém, conforme citado por O'Connell et al [11], assume-se na maioria das pesquisas que essa redução do pH ocorre por meio do processo de carbonatação.…”

“…Alguns estudos são focados em uma etapa específica do processo, como a produção e o nível de H2S [7][8][9], investigação das espécies de bactérias envolvidas no processo [10], análise de estudos anteriores [11][12][13] ou mesmo a criação de modelos de simulação [14,15] de todo o processo.…”