Ladle Furnace Slag as a Partial Cement Substitute in Mortars with Water-Retaining Admixtures

Ladle furnace slag (LFS) is a byproduct from steel refining with high calcium oxides and hydroxides contents, making it viable as a supplementary cementitious material (SCM), enhancing microstructure and mechanical properties, particularly in mortars. Therefore, this work evaluated the replacement of 30% of ordinary Portland cement (OPC) with LFS in coating mortars, combined with a water-retaining admixture as well as the pozzolanic addition of Metakaolin (MK). The mortars followed a 1:6 (binder:aggregate) ratio, and the tests evaluated their properties in the fresh and hardened state, such as the water retention and mechanical properties, along with microstructure characterization to investigate the effects of the binder blends. At 28 days, LFS incorporation ensured water retention, less compacted matrix and greater capacity of deformation absorption, which are properties particularly beneficial for masonry mortars. MK’s pozzolanic reactions resulted in pore refinement; however, the improvements in nominal strength were not statistically significant.