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Utilisation de la bioprécipitation de carbonates de calcium pour améliorer la qualité de granulats de béton recyclé

Abstract : Sands produced from demolition wastes (RCA) have a significant porosity due to the residual mortar resulting from the primary concrete. This is a brake on their recycling in concrete, as would be desirable to develop the circular economy of the sector. The natural carbonation byair of RCA is known to improve their performance. On the other hand, it is very slow and the associated storage constraints are not industrially acceptable. In addition,calcifying bacteria have been used for years to improve soils or monumental stones. In this context, the object of this thesis is to develop a method of accelerated calcification by deposition of bacteria on the surface of RCA This thesis is divided in 2 phases:- Selection and adaptation to pH12 of alkalophilic bacteria with the study of their growth and theirCaCO3 production yield, in vitro, in different environments (pH, urea or not, calcium concentration…) - RCA and mortar disk treatment with different processes whose efficiency is evaluated by a diminution of the material porosity. At the end of this work, a bacterial strain with a satisfying calcific production in contact with RCA was identified. However, the porosity reduction of the treated RCA porosity remains limited. The observations made show that this is linked to a heterogeneous deposit of calciumproduct on the surface of RCA. To conclude this work,several areas to be explored are proposed to improve the process.
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Marion Médevielle. Utilisation de la bioprécipitation de carbonates de calcium pour améliorer la qualité de granulats de béton recyclé. Génie civil. École centrale de Nantes, 2017. Français. ⟨NNT : 2017ECDN0031⟩. ⟨tel-02124134⟩

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