Microscopic analysis of pigmented concrete with rubber waste applied to the interlocking block

ABSTRACT

In this work the microstructure of pigmented concrete with and without rubber residue was analyzed by scanning electron microscope, aiming its application in the manufacture of interlocking block. It was verified that the reference concrete (without rubber) presented dense and compact paste and according to the increase of the rubber content in the concrete, the tendency was observed to increase the porosity and number of voids in the cement paste, appearance of cracks and zone of sharp transition between aggregates and paste, except for the trace containing 5% rubber. These analyzes allowed a better understanding of the mechanical behavior of these concretes. The binder employed was structural white Portland cement. In order to give the interlocking block another architectural and aesthetic advantage, an inorganic type pigment based on iron oxides and blue chrome was used. The rubber residue used as a partial replacement for fine aggregate (natural sand) came from the tire retreading process and was added to the concrete in the following proportions 2.5%, 5.0%, 10%, 20%, 30% while the pigment content was kept constant, being 6% in relation to the cement mass. Regarding the mechanical tests, the results indicated that, for the traces containing 2.5% and 5.0% of rubber residues, the ABNT NBR 9781:2013 standard is attended with respect to the characteristic compressive strength at 28 days (greater than or equal to 35 MPa), which did not happen for the traces with 10%, 20%, 30%. Considering the concrete compositions studied in this research, it can be stated that the use of rubber waste as a partial substitute for sand is an alternative for recycling the product which adds a lot to the environment and avoids the inappropriate disposal of this environmental liability.

Keywords
Alternative Materials; Microstructure; Interlocking Block; Rubber