Sand Mining Tailings as Supplementary Cementitious Material

Sand mining tailing (ST) is a byproduct of the sand extraction of submerged pits, a process which is carried out to obtain aggregates for civil construction. This tailing consists of fine particles from the pulp washing process, usually disposed of in decantation ponds. The present study proposes ST as a supplementary cementitious material (SCM) for Portland cement concrete, thereby reintegrating this tailing into the production chain. In this sense, ST was characterized, and concretes containing 2% to 14% of cement replacement (%vol) by ST were produced and evaluated. STs showed natural fineness, particles with angular morphology, a significant amount of kaolinite, and 36% amorphous content. ST concretes exhibited a compressive strength of up to 57.9 MPa at 28 days under 7.0% of cement replacement, 38.8% higher than the reference. Consequently, only 5.6 kg/m3 of Portland cement was required to attain 1.0 MPa, representing a 33.6% reduction compared to the reference. The ultrasonic pulse velocities measured in ST concrete with 2.0%, 4.0%, 7.0%, and 14.0% cement replacement were 3.0%, 6.1%, 9.3%, and 6.6% higher than the reference, respectively. These results indicate enhanced mechanical properties, improved matrix uniformity, and superior environmental performance across all SCM levels compared to the reference, with optimal efficiency observed at 7.0% ST content.

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