Avaliação da viabilidade técnica do uso de cavacos metálicos em concretos para pavimentos rígidos

Abstract

Ordinary Portland cement concrete depicts limitations such as low tensile strength and flexural strength. Both resistances are essential to concretes used in rigid pavements due to the repetitive traffic loads. With this in mind, lathe steel scrap becomes an interesting modifier to be added to the reference concrete for paving applications, once it behaves essentially similar to fibers, reduces crack propagation and increases flexural and tensile strength values. This residue also shows environmental benefits, reduces concrete production costs, yields a sustainable and correct destination and does not demand previous washing and cleaning. In this manner, the main goal of the present research study is to evaluate the technical feasibility of the use of lathe steel scrap in concretes for rigid pavements. Different contents for this residue were considered and two approaches were followed here: direct addition (volumetric contents of 0.0, 1.0, 1.5 and 2.0%) and partial replacement of the fine aggregate (contents of 0%, 10%, 20% and 30% by mass). The effects of these uses of lathe steel scrap on the physical and mechanical properties of the concrete were examined, including compressive, tensile, and flexural strengths, static and dynamic modulus of elasticity, void index, specific mass, water absorption, and capillary water absorption. To determine any statistically significant differences between the incorporation mixtures, ANOVA analysis as well as the Tukey’s test were performed. The results indicate that lathe steel scrap incorporation significantly influences the mechanical and physical properties of the base concrete. Compressive strength did not considerably change for all contents, but it decreased for 30% fine aggregate replacement. On the other hand, workability diminished proportionally to the incorporation rate. Tensile strength did not show benefits after the addition of this residue, since it showed reductions for the addition contents of 1.0% and 2.0%. Other mixtures remained unchanged in terms of this mechanical property. The best flexural strength results were observed for 10% fine aggregate replacement, even though all incorporation levels improved residual strength when compared with the reference concrete. Static and dynamic moduli of elasticity depicted considerable reductions in all the studied mixtures. The void index significantly increased in the mixtures with replacement of conventional aggregates by the residue, thus directly affecting specific mass and water absorption. However, no variations were observed in the mixtures with simple addition of lathe steel scrap. Specific mass was significantly reduced only for the replacement content of 30%. Water absorption increased and capillary water absorption decreased for all mixtures. Based on technical criteria for rigid pavements, none of the studied mixtures fully met the required parameters, indicating the need for adjustments in mix design to ensure practical feasibility.