Soutenance de thèse de Doctorat de Hassan FARDOUN

30 Mars – Soutenance de thèse de Doctorat de Hassan FARDOUN

14 h campus de Talence, bâtiment A29, Amphi E

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Sujet : Mechanical behavior and durability of earth concrete: an experimental and numerical study

Résumé

Résumé :

In recent years, many efforts have been made in the field of construction to replace traditional concrete with alternative construction materials. Constructions made from raw earth are interesting considering their better thermal and acoustic properties compared to ordinary concrete. Earth materials possess advantages in terms of CO2 emissions and energy consumption. In addition, they are of low cost and available. A step beyond other earth materials, earth concrete is designed to be pourable. On the other side, efforts have been made also to replace natural sand (NS) by recycled sand (RS) to avoid resource depletion.

This thesis aims to assess the effect of clay and RS on the mechanical properties and durability of earth concrete. Compressive tests were carried out at different ages and at different curing conditions and monitored in parallel with acoustic emission (AE) and digital image correlation (DIC) techniques. Flexion tests were performed as well. The results revealed degradation in the mechanical properties and fracture energy as recycled sand replaces natural sand and with the increase of clay content. However, an improvement in the fracture toughness was reported in presence of RS and higher clay content. At drying conditions, the results showed how clay contributes to strength development after a short period of drying (14 days) and to strength loss after long period of drying (90 days) due to the formation of shrinkage induced cracking. Such loss was more significant in the recycled sand-clay mixtures. To better understand this behavior, shrinkage was measured in parallel with mass loss. In addition, ultrasonic tests were conducted. Furthermore, earth concrete mixtures were subjected to cyclic loadings and monitored also by AE and DIC. A good correlation between both investigations was revealed. The results permitted to state that Kaiser Effect is not necessarily affected crack width development. Long-term deformation tests were carried out (autogenous shrinkage, drying shrinkage, basic creep and drying creep) on NS and RS mixtures in order to evaluate the long-term residual mechanical properties. The results revealed that when RS replaces NS, autogenous shrinkage decreases while basic creep, drying shrinkage, drying creep increases. Regarding numerical modelling, numerical simulations with finite elements were performed using Fichant's isotropic damage model to reproduce the failure behavior of these materials. In addition, simulations for the mass loss and shrinkage were carried out to eventually assess the hygro-mechanical behavior of earth concrete.

30 Mars – Soutenance de thèse de Doctorat de Hassan FARDOUN

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