Hyperpressed Brick Based on Marbleized Limestone Processing Waste

Despite the large volumes of marbleized limestone processing waste (MLPW) generated by the stone industry, its utilization in the production of high-strength masonry materials remains limited, and systematic comparative studies of white and gray Portland cements in hyperpressed MLPW-based bricks are scarce. In this study, four mixture formulations containing MLPW (70–85 wt.%), white Portland cement (CEM I 52.5, M500) or gray Portland cement (CEM I 42.5, M450), and water were prepared at a constant water-to-cement ratio of 0.25. Specimens were manufactured by hyperpressing under compaction pressures of 28 and 41 MPa and cured for 7 days in a sealed moist environment. The formulations compacted at 28 MPa achieved compressive strengths corresponding to brick strength grades M350 and M400. Increasing the pressure to 41 MPa yielded grades M400–M550 with white cement; under identical conditions with gray cement, grades M400 and M450 were attained. Among the tested formulations, those containing 75–80 wt.% MLPW (20–16 wt.% cement) showed the most favorable combination of compressive strength and density. The mechanical performance correlated well with the microstructural features observed by scanning electron microscopy (SEM) and EDS analysis. The average density of all specimens exceeded 2100 kg/m3, classifying the materials as heavyweight concrete. The novelty of this work lies in the comparative evaluation of white and gray Portland cements in hyperpressed MLPW bricks and the establishment of relationships between compaction pressure, binder type, overall mixture composition, and resulting strength grades. The results demonstrate a promising route for converting high volumes of industrial marble waste into high-strength masonry units. However, further investigation of durability-related parameters, including water absorption, frost resistance and flexural strength, is required before the practical application of the developed materials can be fully evaluated.