Preparation and microstructural mechanism of nano-CaCO ₃ -modified high-fluidity cement-based grouting materials

Abstract

To address the demand for grouting-based rehabilitation and stiffness enhancement of deep structural distresses in asphalt pavements, a high-fluidity nano-calcium carbonate modified silicate cement-based grouting material was developed. The optimal mix proportion was determined using orthogonal experimental design combined with Taguchi-grey relational analysis. The results revealed that a water-to-cement ratio of 0.39, 20 % fly ash, 0.3 % superplasticizer, 4 % bentonite, and 2.5 % nano-CaCO ₃ (NC) yielded the best performance in terms of fluidity and mechanical properties, ensuring both injectability and stability. NC was selected due to its superior nucleation and filling capabilities, which significantly improved the pore structure of the hardened matrix. The material’s microstructural evolution and hydration behavior were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results indicated that NC effectively accelerated early-stage cement hydration without generating new hydration products. During 3-d and 7-d curing periods, the content of calcium hydroxide (CH) remained nearly unchanged with increasing NC dosage, suggesting its influence lies in hydration kinetics rather than chemistry. However, excessive addition of NC negatively impacted both workability and overall material performance. The developed grouting material exhibits excellent fluidity, stability, mechanical strength, and cost-effectiveness, providing both theoretical and experimental support for practical applications in infrastructure reinforcement.