Production of adhesive mortars with ornamental rock processing sludge and calcium carbonate sludge

The ornamental rock and paper cellulose industries generate unavoidable quantities of residue throughout the production steps, such as ornamental rock processing sludge and calcium carbonate sludge from the kraft process. The purpose of this study is to evaluate the production of adhesive mortars with partial substitution of fine aggregate with either ornamental rock processing sludge or calcium carbonate sludge. This was conducted with chemical and mineralogical characterization of the materials and the testing of mortar mixtures with 5% and 10% aggregate substitution. Mechanical tests were conducted on the mixtures in both the fresh and hardened states. Results showed that consistency index and slump decreased with increased substitution fraction, but the difference is not significant. Compared to the reference mortar, the mixtures with 10% substitution of both sludges presented higher tensile adhesiveness strength with 1.13 MPa for ORPS and 1.23 MPa for CCS, as well as lower capillary water absorption. It was concluded that there was a potential use of these sludge residues in adhesive mortars which could allow a reduction in the consumption of natural, non-renewable raw materials that would normally have been be necessary.