Enhancing adhesion and microstructural properties of cementitious mortars through submerged arc welding (SAW) slag incorporation

This study investigated the effects of Submerged Arc Welding (SAW) slag incorporation and varying lime and sand concentrations on the adhesion and microstructural properties of cementitious mortars. Adhesion performance was evaluated on two substrate types: with and without spatter dash. The inclusion of SAW slag significantly enhanced tensile adhesion strength compared to reference mortars (0% SAW). On non-spatter dash surfaces, the increase in adhesion with 5% SAW varied from 16% (in strong mortar, from 0.61 MPa to 0.71 MPa) to 57% (in weak mortar, from 0.21 MPa to 0.33 MPa). On spatter dash substrates, the gains were even more pronounced, ranging from 71% (from 0.58 MPa to 0.99 MPa) to 101% (in strong mortar, from 0.72 MPa to 1.45 MPa). Mortars with a lower lime and sand content (strong mortars, such as SM5) exhibited superior adhesion (maximum of 1.45 MPa), driven by increased C-S-H gel formation, as evidenced by SEM and elemental mapping (Ca/Si ratio of 1.75 for SM5). Thermogravimetric analyses confirmed a reduction in Ca(OH)2 content (mass loss of 1.30% in SM5 vs 2.31% in WM5) in the strong mortars. These findings highlight the dual benefits of SAW slag: enhanced adhesion performance and sustainable waste management. They emphasize the importance of optimized mortar compositions for promising applications in plastering and rendering.