Avaliação da resistência mecânica de argamassas de cimento Portland contendo serragem de couro tratada em meio ácido
Abstract
Suitable destination of industrial solid wastes that have not well
established or completely successful mitigation techniques is nowadays a
fundamental important subject, all over the world. In Brazil, one of the most
pollution-intensive industries is the tanning skin and processing leather industry.
Among its wastes, there is a hazardous chromium-containing waste, named
leather shaving, which needs technological alternatives to reintegrate its great
quantity generated to materials life cycle. Based on materials engineering
concepts, and from the experiences related in bibliography, this work proposes
the leather shaving dissolution in phosphoric acid and later incorporation of this
new product in Portland cement mortar; changes on the strength of mortar are
very important, being the focus of this work. Mortars and cement pastes were
made to serve as standards, and treated waste-containing samples were
produced to compare the results and to try explaining their causes. The analysis
of the experimental results shows that treated leather shaving addition inhibits
hydration of Portland cement compounds, due to the phosphoric acid; this
retard is disclosed by the increased paste setting time and the mortar
mechanical strength development after 91 days, this strength is close to the
standard sample one. Porosity remained almost unaltered, and the main
microstructural change found was the calcium phosphate phase formation,
detected by XRD and SEM. At last, cement matrix was effective at fixing
chemically Cr (III), an important result in view of environmental aspects.