30 Mars – Thesis defense - Hassan Fardoun

10 h Videoconference

Mechanical behavior and durability of a new material based on clay: an experimental and numerical study.

In recent years, many efforts have been made in the field of construction to replace traditional concrete with alternative materials such as the concrete containing a high proportion of various ecological components called 'green' in acceptable properties for the desired application. For example, constructions made from the raw earth are interesting considering their better thermal and acoustic properties compared to ordinary concrete. The objective of the production of this concrete is to reduce the consumption of cement and therefore the production of CO2, to provide solutions to avoid the depletion of natural resources such as aggregates and reduce energy consumption in the production process. On the other side, efforts have been made to replace natural sand by recycled sand to avoid resource depletion as well. In the following study, first, the effect of clay and recycled sand on the mechanical behavior of earth concrete was studied. 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 as recycled sand replaces natural sand and with clay content. In addition, the results showed the contribution of clay to strength development after short period of drying and to strength loss after long period of drying. Such loss was more significant in the recycled sand-clay mixtures. To better understand this behavior, the shrinkage was measured in parallel with mass loss. In addition, capillary rise test was conducted. Second, earth concrete mixtures were subjected to cyclic loadings and monitored as well by AE and DIC. An AE damage assessment was carried out. A good correlation between both investigations was revealed. Finally with experimental part, creep tests were performed. Regarding numerical modelling, as a first step, numerical simulations with finite elements were performed using Fichant's isotropic damage model to reproduce the breaking behavior of these materials and to determine the mechanical properties. In addition, simulations were carried out for the mass loss and shrinkage.

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