Eco-Efficient Technology for Sustainable Cementitious Composites: Short-Term Response of Limestone, Chalk, and Marble to Magnesium-Induced Chemical Degradation

Improving the environmental sustainability and resource efficiency of cementitious composites requires technologies that reduce natural aggregate consumption while maintaining adequate durability in aggressive environments. This study evaluates limestone, chalk, and marble as partial replacements for natural sand at replacement levels of 10% and 20%. Prismatic specimens were cured for 28 days and then exposed for 14 days to 10% MgCl2 or MgSO4 solutions under static conditions. Dry bulk density, water absorption, mass change, flexural strength, and compressive strength were determined. Carbonate type and dosage strongly influenced composite performance. The 10% marble mixture showed the lowest water absorption (13.90%), while 10% chalk produced the highest dry bulk density (1912 kg/m3) and initial compressive strength (68.53 MPa). After exposure, its compressive strength reached 73.57 MPa in MgCl2 and 74.53 MPa in MgSO4. In contrast, 20% chalk resulted in the lowest density and highest water absorption. Salt MgSO4 caused greater mass changes and flexural-strength losses than MgCl2. The results demonstrate that moderate replacement of natural sand with carbonate materials can provide an eco-efficient technological approach that reduces natural resource consumption while maintaining or improving selected physical and mechanical properties. The selection of limestone, chalk, and marble should therefore consider both technological performance and environmental sustainability.