In-situ active interface cementation via nano-engineered partially calcined limestone aggregates

Abstract

Traditionally, aggregates in concrete are regarded as inert fillers. This study proposes a novel interface-activating strategy that redefines aggregates in concrete from inert fillers to reactive components. By subjecting limestone aggregates to low-temperature rapid calcination, reactive nano-CaO domains are formed on the surface, enabling in-situ hydration–carbonation synergy at the aggregate–matrix interface. This interfacial activation significantly improves the density, continuity, and chemical bonding of the interfacial transition zone (ITZ), which is traditionally regarded as a structural weak point. Compared to unmodified systems, the optimized composite shows a 37 % increase in 28-day compressive strength and a 45 % reduction in total porosity. Multiscale characterizations confirm accelerated portlandite formation at early stages, increased CaCO3 precipitation at later stages, and progressive pore structure refinement. Unlike externally added CaO, the in-situ nano-CaO formed directly on the aggregate surface ensures superior interfacial reactivity and mechanical integrity. This study introduces, for the first time, an aggregate-level nanostructural engineering route that enhances concrete performance through intrinsic surface reactivity. The approach offers a scalable and cost-effective solution for reducing cement demand and carbon footprint, advancing the development of next-generation low-carbon, high-performance cementitious materials.