Estudo de concreto autoadensável aplicado à bases de máquinas-ferramenta.

Abstract

Machine tool bases are traditionally manufactured with cast iron and steel, with a low damping disadvantage. At first, in this research as an innovative way, an alternative material to traditional ones, and their application in the manufacture of machine tool bases are investigated. This cementitious composite is formed by a steel fibers-reinforced self-compacting concrete (SCC), containing both rubber and marble and granite residue contents. It is known that one of the biggest drawback of dynamic rigidity in the construction of these bases, is the damping rate. In view of this, in this present work the increasing levels of rubber residues in the concrete mixture, is discussed. Also, is indicated a better ability of the concrete to absorb energy, evidencing a good alternative material to be used in the manufacture of these bases. It is worth noted that, with the incorporation of rubber in the concrete, the microstructure has a greater number of voids and, consequently, a loss of mechanical strength is provided. In order to mitigate this reduction, the marble and granite residues are incorporated. These fines fill the pores, increase the packaging of the particles, is increased and concrete strengh is decreased, while the permeability is incresead. A scanning electron microscope is used in order to observe the resulting microstructural array. Six concrete mix are developed, and physical material characterization tests are carried out and fresh and hardened states are evaluated. The fresh properties of the concretes are: workability, plastic viscosity, visual stability and passing ability. The hardened properties are: compressive strength, tensile strength, damping factor, static and dynamic moduli of elasticity. The specific gravity is also checked for both the fresh and hardened states. Analyzing the data, it is noted that the damping rate is increased more than 46% in relation to the usual materials used in the manufacture of machine tool bases. Additionally all studied CAA compositions are classified as structural concrete according to ABNT NBR 8953 (ABNT, 2015a). It is worth noted the environmental benefits resulting from the reuse of these materials in the production of concrete, which will probably be disposed into landfills for class A civil construction and inert waste.