Evaluation of reactivity to the chemical attack of waste from the mining of scheelite used as aggregate in cementitious mortars

ABSTRACT

The scheelite mining, located in Currais Novos, Rio Grande do Norte, has generated large volumes of solid waste that are inadequately destined for environmental systems, causing negative environmental impacts to the municipality. One of the alternatives to destination of these residues is the use in cementitious matrix mortars. However, there are no consistent studies on the technical feasibility of chemical attacks and influence on their durability. In this context, this work aimed to verify whether mortars made with scheelite mining residues in total substitution to conventional aggregate are susceptible to attack by sodium sulfate. The physical, chemical, and mineralogical characterization of the residue was carried out using the following techniques: sieve particle size analysis; determination of unit mass; obtaining the content of powdery material; X-ray fluorescence spectrometry, and X-ray diffraction. In the investigation of the occurrence of sodium sulfate attack was evaluated by the dimensional variation of the specimens when immersed in sodium sulfate solution, according to the methodology of Associação Brasileira de Normas Técnicas NBR 13583. The results of mixture 1:3 indicated that the aggregates from scheelite mining residues showed a reactive behavior to attack by sodium sulfate (expansion greater than 0.06%), as well as an increase in resistance to simple compression by 4.74%. Therefore, although it was found that specimens incorporated with scheelite residues were reactive to sulfate, it was observed that they were not able to mechanically deteriorate the specimens.

Keywords:
alternative aggregates; chemical attack by sodium sulfate; mining residues