Dosage of interlocking paving with ornamental rock waste: An experimental design approach, particle packing and polluting potential

Abstract

This article proposes a dosing procedure for interlocking concrete pavements that incorporate ornamental rock waste, with a view to meeting mechanical and molding criteria and ensuring the sustainability of the mineral industry, an economically important sector in Brazil despite environmental issues surrounding its waste generation. The procedure involves evaluating the packing density of the sand, coarse aggregate and waste fines via the minimum void ratio. A simplex lattice experimental design and the theoretical particle size distribution (Alfred) model were used, followed by a 22 factorial with a center point to determine the influence of the factors (proportions) and different water-cement (w/c) ratios (levels). The full cubic model obtained a 95.62 % adjustment index for optimal particle size of the aggregates and waste fines, and the lowest MVR (1.961 103kg/m³). This trend was confirmed by the theoretical Alfred model, with a coefficient of 0.29, and the factorial experiment, with an adjustment index of 97.50 %. Dosing indicated an ideal cement content of 20 %, 15.2 % for sand, 44.8 % for the coarse aggregate and waste fine incorporation of 20 % of the total mass (25 % of the aggregate mass), achieving compressive strength of 36.70 MPa for w/c and water/aggregate ratios of 0.5 and 0.123, respectively, and a carboxylate superplasticizer content of 6% of cement consumption, as well as adequate molding and demolding conditions. An ecotoxicological assessment was conducted, which found that waste fine incorporation posed no risk to the environment. Scanning electron microscopy (SEM) demonstrated that this mixture exhibited the best mechanical performance, with adequate aggregate particle size distribution and paste coverage, as well as waste fine stability in the cement matrix.