One-part sodium carbonate-activated slag/calcined dolomite mixes: effects of nano-silica on strength development, microstructure and shrinkage

This study explores the use of calcined dolomite (CD) as a supplementary precursor and nano-silica (NS) as an additive in one-part sodium carbonate-activated slag-based mixes. Binary mixes incorporated up to 20% CD, while ternary mixes included 3% NS to enhance microstructure, strength, and shrinkage performance. Microstructural analysis was conducted using X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. Results showed that CD increased flowability and reduced setting time, whereas NS slightly decreased flow but significantly accelerated setting. The optimal compressive strength (55 MPa at 28 days) was achieved at 10% CD replacement. While NS improved strength and reduced shrinkage in slag-based mixes, it negatively impacted ternary mixes. Binary mixes exhibited lower shrinkage due to pore structure variations. Environmental assessments indicated that these mixes produce significantly lower CO2 emissions than cement-based alternatives, highlighting their potential as a sustainable construction material.