Application of Recycled Materials & Fiber Reinforcement in Precast Concrete Slabs

Due to the increased demand for more sustainable and durable structures, more and more recycled materials are being used for structures, which poses many challenges to civil engineers. In this regard, concrete has played an important role as it is one of the main construction materials for many infrastructure projects. On the other hand, the disposal of waste tires has become a serious problem in the modern world. More than a billion tires are thrown away every year, and in the absence of proper disposal mechanisms, they are dumped in landfills. The huge amounts of waste tires have caused significant damage to the environment. These waste tires contain several raw materials that can be recycled and used in various engineering projects, such as steel fibers. Thus, recycling these tires can benefit humanity in several ways. Talking about engineering projects and specially Civil & Infrastructural Engineering projects, it is essential to increase the sustainability of concrete structures, it is also possible to increase the mechanical performance instead of replacing the components. In other words, the so-called "performance strategy" can be applied. It is obvious that the environmental impact of a cubic meter of high performance concrete is greater than that of normal concrete. This is generally due to the higher content of cement and other materials (e.g. steel fibers), which have a large carbon footprint. However, better mechanical performance can reduce the mass of the concrete structure, which in turn leads to a lower global environmental impact. In the first part of this research, the study focuses on the use of recycled tire steel fibers (RTSF) enlarge quantities in the so-called vibrating slab (50mm Slab) of predalles, in order to investigate their suitability in precast concrete slabs (predalles) as an alternative to steel and industrial fibers. For this purpose, we tested samples of vibrating slab (50mm depth) of each mix, i.e., Industrial Fiber Reinforced Concrete, Recycled Fiber Reinforced Concrete, Reinforced Concrete, and Plain Concrete. After obtaining the results of the first part based on the compressive and flexural strength tests carried out, in the second part, the effect of changing the types of aggregates was studied in 6 samples of vibrating slabs in a way to check the effects of each type of aggregate, whether recycled, normal aggregate or even rubber, on CAM and on the compressive and flexural strength, using only recycled fibers as reinforcement in all six samples except the reference sample where we used bars as a reinforcement. After analyzing the tests and comparing them with the Eurocode regulations, polystyrene blocks were placed on the 50 mm slab between the formed trusses and 150 mm thick concrete that was poured to form 200 mm of the so-called "Predalle slabs". In the final step, the predalles were tested against the most favorable test showing behavior against bending, which is essentially the only behavior a predalle can experience during its service life in a structure. The results were analyzed and interpreted to reach a conclusion that can be used as part of the service contract for Theoretical-experimental activity to support the prototyping of new sheets with recycled materials, funded by Botta SRL.