Effect of C2S and limestone powder contents on interfacial bond characteristics of high-strength steel fibers embedded in low-carbon mortars

Abstract

This study explores influence of dicalcium silicate (C2S) and limestone powder (LP) contents on the interfacial bond characteristics of smooth and hooked steel fibers embedded in low-carbon mortars. Four mortar compositions with varying LP (0–30%) and C2S (16.4–57.2%) contents were evaluated through single-fiber pullout, compressive tests, SEM–EDS, and nanoindentation (NI) analyses. A mixture containing 10% LP substitution in belite-rich cement (BRC) exhibited optimal performance and sustainability. Although increased C2S content in BRC reduced early-age strength, it significantly enhanced the long-term mechanical and interfacial properties and improved the 90-day compressive strength, bond strength, and pullout energy by up to 65%. Higher LP levels yielded denser fiber–matrix interfacial zones (FMZs) and reduced porosity (25.0%→18.9%), while elevated C2S promoted greater C-S-H formation (34.6%→51.5%). The optimized LP–BRC system demonstrated superior durability and interfacial performance with substantially lower CO2 emissions, offering a viable and sustainable alternative to ordinary Portland cement (OPC).