Study of the solidification/stabilization process in a mortar with lightweight aggregate or recycled aggregate

Abstract

This study investigates the solidification/stabilization process of electroplating sludge in mortars with internal curing promoted by porous aggregates (lightweight and recycled aggregate). For that, cementitious mortars were manufactured with recycled or lightweight fine aggregates added in two conditions: saturated and dried before the mortar preparation. They were incorporated in partial replacement of the natural aggregate. As well, 8.5% and 100% of electroplating sludge (liquid) in relation to the total water content in the mortars were replaced, to assess the fixation of contaminants. For this, were determined the physical properties of aggregates (density, absorption, compliance test, and others), then the mortars were prepared and evaluated for consistency, absorption by immersion, mechanical strength, leaching and others. The results showed that the LWA and RCA presented 99.9 and 96.7% efficiency in Pb adsorption, receptively. Also, for Zn, the RCA presented 98% efficiency in adsorption in the solutions. The cement consumption was reduced, on average, from 490 kg m−3 with NA to 470 kg m−3 with RCA and to 405 kg m−3 with LWA. The leaching test of the mortars showed that 100% of the Cr and Ni from the solution was adsorbed by the mortars. In the compliance tests, the Cr metal was not leached from the crushed mortars, and in the partial-added mortars, zinc was leached in less quantity in comparison with the reference series (48% less, on average). The results show that the incorporation of electroplating sludge in mortars did not alter their properties, as well as the replacement of 25% of the natural aggregate by recycled aggregate. Finally, the recycled aggregate can be used to partially replace the natural aggregate, increasing its potential for use and without causing damage to the final material. As well as the recycled and lightweight aggregate proved to be an effective chemical sorbent for the studied electroplating residue.