Feasibility Analysis of Mortar Development with Ornamental Rock Waste for Coating Application by Mechanized Projection

Abstract

The industrial production of lime generates greenhouse gases, which contributes to increase the global warming. Therefore, the present study evaluated the feasibility of replacing lime by ornamental rock waste (ORW) as a by-product of the related stone industry, and developed a cost-effective mortars. These new low-costing mortars are intended as fresh fluid paste coatings to be applied on walls by the mechanized projection technique. The ornamental rock waste was collected from a marble and granite industry as ground stone. It was finely crushed before mixing with cement, sand, water and superplasticizer in amounts of 1.0% (R01), 1.2% (R02) and 1.3% (R03), to prepare the mortars, which had the mixture, cement: ORW: sand, 1:1:4 in wt.%. These novel mortars were characterized in both fresh, for well projection, and hardened state, to evaluate the properties after curing performance. The results showed that mortar R03, achieved the best results and did not present cracks in the hardened state. Its water retention was found above 30%. Both tensile strength of 0.312 MPa and compressive strength 7.88 MPa, which are above the corresponding minimum required by the standard for external coating. Water absorption by immersion of 19.37% and void content of 20.23% were close to the corresponding values for hydrated lime mortar. Dry shrinkage showed that the new R03 mortar reached more than 90% of their total retraction at 7 days of cure without sign of cracking. These findings revealed the R03/ornamental rock waste -based mortar applied by mechanized projection as a promising sustainable substitute for common lime-based mortar.