Authors: Manal Bouasria
Source: SPIRE - Sciences Po Institutional REpository (preprint, 2022-09-26)
Field: Materials Science — Materials Chemistry

Development and monitoring of the mechanical and hygrothermal performance of low-carbon materials by smart technology The distribution of energy consumption and greenhouse gas emissions in buildings has been estimated at 30% during the construction phase, 70% during the use and maintenance phase, and 1% during the demolition process. During the construction phase, the materials used represent 56% of the CO2 emissions. The long term use of a building, difficult to control, depends on a large number of variables. Numerous levers are therefore studied to act during construction: low-carbon materials, waste reduction, promoting the circular economy, optimized design, intelligent material saving, construction and demolition waste, etc.Therefore, the objective of this PhD is to develop new low carbon materials. Physical, chemical, hygrothermal and mechanical characterization experiments are carried out at different scales. A prototype will be designed and a proof of concept will be created to verify the effectiveness of the eco-materials developed in this research.In this context, we started by studying the behaviour of cementitious mixtures including by-products. We substituted cement by several wastes, i. e. ferronickel slag (FNS) associated with crepidula shells (CR) and fly ash (FA) associated with crepidula shells. Mechanical and thermal properties of the mortar and concrete were studied at the material scale and also on a lab-scale prototype. The mechanical properties of the mortar with the use of FA-CR in substitution of cement were found to be superior to those of ordinary mortar and concrete. The prototype based on this new low carbon material was developed to monitor the hygrothermal behaviour with artificial neural network models. The results of the experiment on the risk of condensation and mold growth reveal that the chosen concrete mix can prevent condensation. Indeed, the high silica, aluminate, and calcium content of the smart Fly ash-Crepidula mixture reacts with water from humid ambient air to generate additional hydrates as a result of pozzolanic reaction, resulting in continual strength enhancement.In this thesis work, we were also interested by the stabilization of earthen construction using a cementitious binder and then by an organic binder. In the first part, we investigated the suitability of gravel washing sludge and seashells as an unfired earth construction material while using fly ash as a binder and cementitious stabilizer. Our results show that this mixture leads to a reduction in porosity, an increase in mechanical performance and a decrease in thermal conductivity with a higher specific heat capacity. In the second part, we used seaweed powder as a stabilizer for the cob construction. We studied the impact of substituting soil with seaweed powder (organic binder). For this new algae-based material, we observed an improvement in heat storage capacity and thermal performance without impacting mechanical properties. The development of the artificial neural network to predict the hygrothermal properties of the earth-algae-fiber prototype showed a good similarity between the experimental results and the model. Finally, the stabilization mechanism of the soil was studied using microstructural analysis techniques (XRD and Raman spectroscopy). Nat ; Mechanical engineering ; Materials science ; Physics ; Engineering Silicone and Siloxane Chemistry