The use of submerged-arc welding flux slag as raw material for the fabrication of multiple-use mortars and bricks

Abstract

This work has as objective to analyze the recycling possible uses of the slag of welding flux (SWF) in the civil construction. It was searched the liability of SWF as substitute of sand in the production of multiple-use mortars and clay for the production of ceramic bricks. SWF has origin in the submerged-arc welding (SAW), and have been used slags of the acid, neutral and basic types, according to its neutrality. Mortars have been made containing the three types of SWF and in addition a reference mortar made with sand. Physical and mineralogical characteristics of each SWF were studied, and the physical properties (consistency and density) and mechanical properties (compressive and tensile strengths) of the mortars were analyzed. Ceramic pieces have been made containing kaolinitic sedimentary clay up to 10 wt. % of SWF. The pieces were prepared by uniaxial pressing and fired at 950ºC. The following properties after firing were determined: linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength. The results show that for multiple-use mortars, SWF reached excellent results, being an overall substitute for sand as fine aggregate. For ceramic bricks, SWF can also be used as partial substitute for red clay. Both applications of SWF significantly contributes for the reduction of the ambient impact: on one hand, reducing the extraction of natural sand and clay, on other hand, contributing for the reduction of the risk of ground water contamination due to the inadequate disposal of the SWF.