Exploring the influence of cement and cement hydration products on strength and interfacial adhesion in emulsified cold recycled mixture: A molecular dynamics and experimental investigation

Abstract

This study employed experimental methods and molecular dynamics simulations to investigate how cement and its hydration products affect the mechanical strength and interfacial properties of emulsified cold recycled mixtures (ECRM). The effects of cement hydration product characteristics, such as content, number of nucleation sites, calcium-silicon (Ca/Si) ratio, degree of hydration, and types of hydration products, on the adhesion and water resistance of the cement-emulsified asphalt mortar (CEAM)-aggregate interface, were studied. The findings revealed that increasing the cement content by up to 2% improved the ECRM's mechanical strength. However, the mechanical strength decreased beyond a cement content of 2%. Molecular dynamics simulation demonstrated that augmented cement hydration product content fostered greater adhesion at the interface between CEAM and the aggregate. The presence of an adequate number of nucleation sites was crucial for cement hydration products' effectiveness in strengthening the interface adhesion. Moreover, hydration products with higher degrees of hydration or Ca/Si ratios exhibited a more pronounced impact on enhancing interface adhesion. Furthermore, cement hydration products enhanced the interfacial water resistance of the CEAM-aggregate interface. Nonetheless, the extent of this improvement depended on the interfacial water content. When the interfacial water content was high, the water resistance decreased, and the influence of cement hydration products became negligible. These results highlight the important role of cement and its hydration products in determining the mechanical properties and interfacial characteristics of ECRM and provide insights for optimizing the design and application of such materials in engineering practice.