Recycled polypropylene fibre-reinforced concrete: from recyclability and recoverability to materials and application
(English) In recent decades, fibre-reinforced concrete (FRC) has played a significant role in construction due to its enhanced residual flexural tensile strength in comparison to plain concrete. However, with the increasing use of FRC, the dismantling of FRC structures is becoming an important chall...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/440609 |
| Acceso en línea: | https://hdl.handle.net/2117/440609 https://dx.doi.org/10.5821/dissertation-2117-440609 |
| Access Level: | acceso abierto |
| Palabra clave: | polypropylene fibre reinforced concrete recycled aggregate recovered fibre mechanical properties mixture design microstructure 624 - Enginyeria civil i de la construcció en general Àrees temàtiques de la UPC::Enginyeria civil |
| Sumario: | (English) In recent decades, fibre-reinforced concrete (FRC) has played a significant role in construction due to its enhanced residual flexural tensile strength in comparison to plain concrete. However, with the increasing use of FRC, the dismantling of FRC structures is becoming an important challenge. Unlike plain and reinforced concrete, the recycling of FRC produces two primary by-products: recycled fibres and recycled aggregates with embedded fibres. Despite its significance, limited research has been conducted on the reuse of these by-products in new concrete. To address this research gap, this thesis focuses on polypropylene fibre-reinforced concrete (PPFRC) as a case study and examines its recycling process and the reuse of the resulting recycled materials. Initially, PPFRC was produced (parent concrete) and recycled by analysing the quantity and morphology of the recovered fibres and recycled aggregates. These recycled materials were used to produce new concrete (with recycled aggregates and recycled fibres) that was characterized, and the results were compared with the mechanical properties of the parent concrete. The findings revealed that the properties of concrete using recycled materials were reduced to different extends compared with the parent concrete. However, when different ratios of recycled fibres were incorporated into concrete, the mechanical properties showed significant improvement compared to using 100% recovered fibres, particularly at a fibre content of 3 kg/m³. Moreover, hybrid -virgin and recycled- fibre concretes outperformed those made entirely with virgin fibres. Thus, under certain conditions, it is feasible to replace virgin fibres with recovered fibres while maintaining or even enhancing mechanical performance. Furthermore, this thesis compares the mechanical properties and microstructure of new FRC made with recycled FRC aggregates to concretes made with natural aggregates and conventional recycled concrete aggregates. Concrete incorporating recycled FRC aggregates demonstrated advantages in fibre distribution at lower fibre contents. However, at higher fibre contents, the embedded fibres were found to have a detrimental effect. Micrographs and chemical dot plots revealed unique characteristics at the interface between the recycled aggregates and the fresh cement paste, highlighting changes in hydration and porosity compared to samples made with natural aggregates and conventional recycled aggregates. Future work on recycled FRC could include exploring the durability and long-term stability of the material, as well as investigating the potential application of recycled fine aggregates in concretes. |
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