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Master Thesis

Study of the durability of repair mortars submitted to acid attacks

Abstract : This study was carried out in order to acquire a better understanding of the behaviour of repair mortars when they are submitted to acid attacks. Above all, this study focuses on the case of an repair mortar that contains polymers. The main objectives of this study were to highlight the influence of the presence of polymers in the case aggressive agents attack the material, and to determine the parameters that main be responsible for the durability of the material. In order do so, three mortars were selected: two repair mortars (one containing polymers – the Monotop 412 SFG - and another one without polymer additions – the Monotop 412 S) and a conventional mortar (CEM 52.5 R) in order to make a comparison. A first step consisted in characterising all of the mortars. Indeed, since repair mortars were used, there was a lack of information about their composition. Making a characterisation of each mortar was essential in order to predict and understand their behaviour when submitted to acids. All of the mortars were characterised from a mechanical point of view, as well as from microstructure and durability points of view. The different tests that have been carried out were: flexural and compressive strength tests, mercury intrusion porosimetry, differential thermal analysis, electrical resistivity, chloride migration and capillary absorption. The different tests have pointed out outstanding properties for the Monotop 412 SFG (which contains polymers) in terms of durability, even if no significant improvement was notices in terms of mechanical properties. They have also highlighted no improvement in the capacity of the Monotop 412 SFG to resist freeze/thaw cycle than a conventional mortar. This part has allowed highlighting that the Monotop 412 SFG has a microstructure that makes it more difficult for aggressive agents to penetrate into the material. A second step consisted in submersing all of the three mortars into two different acid solutions (an acetic acid solution and a lactic acid solution). After one month of submersion, some characterisation tests were carried out in order to qualify the reaction of each mortar. From a visual point of view, it has been determined that the Monotop 412 SFG is the one that presents the best resistance to acid attacks in both cases (acetic acid and lactic acid). Indeed, for both solutions, theses samples were the least degraded after one month of attack. Moreover, the conventional mortar was the most deteriorated. It also appears that lactic acid attack is more intense for mortars than acetic acid attack is, in accordance with their pKa values. It attacked the gel, changing its stoichiometry, and leading to an increase in volume of the specimens. Three different tests were carried out in order to confirm these observations: mercury intrusion porosimetry, differential thermal analysis and a titrimetric method. However, the tests have pointed out a change in microstructure for both repair mortars while the conventional mortar was maintaining its microstructural properties. According to the tests, the properties of both repair mortars were worsened as a result of acid attacks. It can also be underlined that the results were worst in the case of lactic acid attack.
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Master Thesis
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Submitted on : Tuesday, July 17, 2018 - 3:02:59 PM
Last modification on : Friday, January 31, 2020 - 11:41:19 AM
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Sophie Travailleur. Study of the durability of repair mortars submitted to acid attacks. Engineering Sciences [physics]. 2016. ⟨dumas-01841752⟩

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