Concrete with addition of fibers for confection of segmented pre-formed rings for subway tunnel coating

Abstract

In Brazil, the use of Reinforced Concrete with Fiber (CRF) is associated with infrastructure works. This study investigates the mechanical behavior of fiber reinforced concrete (steel and polypropylene) for the construction of segmented subway flooring staves. The goal is to produce a concrete with steel fibers in a suitable content to promote an increase in the post-cracking reinforcement of the concrete, and polypropylene fibers in sufficient quantity to minimize the risk of plastic cracking, as well as to protect against physical damages in case of occurrence of fires. The experimental program consisted in evaluating the mechanical properties of steel fiber and polypropylene fiber in concrete. Reinforced concretes were studied with three different levels of steel fibers (25 kg / m3, 35 kg / m3 and 40 kg / m3) to evaluate mechanical parameters of tenacity, as well as three fiber contents of polypropylene (0.5 kg / m3, 1.0 kg / m3 and 1.5 kg / m3) to evaluate mechanical parameters of the concrete subjected to high temperatures. Statistical analysis (ANOVA) was used to analyze the results, where a gain of up to 12.89% of compressive strength was demonstrated as the steel fiber was added, while for the toughness the results showed increases of up to 108.9% of the toughness factor. As for the analysis of the behavior of the concrete against high temperatures, it was observed that the adoption of polypropylene fibers acted efficiently in combating spalling, however, it provoked a marked reduction of residual resistance.