Formulation and thermo-mechanical characterization of a recycled-based textile-reinforced concrete eco-composite

Laboratory: Laboratoire de Tribologie et Dynamique des Systèmes (LTDS)

Research team: Geomaterials and Sustainable Constructions

Website: http://ltds.ec-lyon.fr

The intern will conduct their work within the LTDS laboratory in the "Geomaterials and Sustainable Construction" team at the Saint-Etienne site. The team carries out research on geomaterials and civil engineering structures. It is involved in several major societal challenges, within a framework of sustainable development: the safety of property and people, the improvement of transport infrastructure systems, the optimization of the use of non-renewable resources, and the improvement and preservation of built heritage.

Context

Due to continuous operating conditions, evolving and potentially severe environmental exposure, combined with variable and sometimes random stress states, concrete structures, even when subject to maintenance measures, progressively deteriorate over time. It is now well established that extending the service life of structures is both economically more viable and environmentally more sustainable. In this context, textile reinforced concrete (TRC) represents a promising material in terms of mechanical performance, including strain-hardening behavior, multi-cracking capacity, and fire resistance.

Although TRC composite materials are recognized for their usefulness and have experienced recent growth, their environmental potential could be better exploited. It is important to note that, for structural applications, carbon textiles are sometimes used. However, the production of this material requires heat treatment above 1,000 °C, leading to the emission of approximately 20 tons of CO₂ per ton of fiber produced. In addition, the composite waste in the construction sector in France exceeded 15,000 tons in 2022. One of the main components of this waste is mortar, which often contains clinker cement - a major CO₂ emitter due to its firing at approximately 1,450 °C. Besides, clinker contributes to the depletion of natural resources by requiring the extraction of limestone and clay.

Recent studies have demonstrated the possibility of integrating recycled cement into mortars and concrete without significant adverse effects on their mechanical properties. Moreover, it has been shown that recycled matrices also allow improved crack control and better mastery of damage mechanisms in terms of strength and durability, without altering high-temperature performance, whether in terms of reaction or fire resistance. Regarding the reuse of reinforcement, to our knowledge, no significant scientific data have been published.

The main challenge of the project is to substitute TRC components with a high carbon footprint with more environmentally and economically sustainable solutions, while preserving their functional properties, particularly mechanical and physical ones. More importantly, the interaction between the textile and the matrix is considered by applying surface modification methods to improve their bonding.

Objectives

The main objective of this internship is to contribute to the formulation and characterization of the textile/mortar interphase at both room and high temperatures.

The internship will include the following tasks:

- Bibliographic study on TRC composites, textile/matrix interphases, and surface modification methods

- Surface modification of the textile reinforcement

- Thermo-mechanical characterization of textile/mortar interphases

- Physicochemical characterization of specimens before and after applying surface modification methods using microstructural analysis techniques

- Data analysis and interpretation in collaboration with the supervisor

- Final year master’s student or engineering student (Bac+5) in Civil Engineering or Materials Science

- Strong background in civil engineering, construction materials, or physic-chemistry of materials

- Strong motivation for experimental research

- Proficiency in English is required