Durabilité des matériaux cimentaires soumis aux acides organiques : résistance chimique, mécanique et de corrosion
|Abstract:||In the wake of the globalization, agricultural development has focused on a single criterion, the intensification of production factors. Therfore, the paradigm of intensive agriculture at the expense of environmental considerations was founded. Effluent stored in concrete retention structures are transformed under the action of bacteria to organic acids, potentially aggressive agents to the cement matrix. This work was mainly designed to determine the adequate formulation of the resistant binder in an agricultural environment. All the realized tests aim to define parameters that control the durability of the cement matrix submitted to the aggressiveness of organic acid of manure. Cement pastes and/or mortars samples of ordinary and special binders was immersed in an acetic acid solution simulating the aggressiveness of manure. The influence of mineral additions include: slag, metakaolin, silica fume and fly ash has been implemented. Leaching and immersion tests have been achieved. Initially, we were interested on the chemical resistance of pastes by analyzing the degradation mechanisms of cement matrix. The analyses were performed by mercury intrusion porosimetry, atomic absorption and x-ray diffraction (XRD). The results show that acidic attack results in a chemical and mineralogical zonation. The durability of ordinary binders and alumina cement is limited given that the effect of the curing period is essential especially for binders having a latent hydration. We were also interested to the quantification of the anhydrous and hydrate phases for binders having the best chemical performance. The quantification of the anhydrous phases was realized by chemical dissolution, nuclear magnetic resonance (NMR) and image processing. However, the quantification of the hydrates was realized by thermogravimetry (T.G.A.). The results show that stability of phases is dependent on their chemical compositions. The evaluation of the compressive strength of sound and altered mortar cubes showed a marked improvement mainly for mortar containing metakaolin compared to the ordinary mortar. The evolution of corrosion of reinforced mortars containing slag or metakaolin was followed by non-destructive electrochemical measurements (corrosion potential and linear polarization). Metakaolin mortars present the best resistance to initiation of corrosion. However, the high porosity of samples containing slag, favoring paths of percolation of acid solution even in advanced cured time, makes the initiation of reinforcement corrosion almost immediately.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||18 April 2018|
|Collection:||Thèses et mémoires|
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