Molecular dynamics simulation of the interaction between aggregates and calcium silicate hydrate and influence of ethylene vinyl acetate copolymer modifier

ABSTRACT

It is known that the bonding strength of the aggregate/cement interface affects the overall durability of concrete. However, whether the modification of ethylene vinyl acetate (EVA) copolymer affects the interface interaction between aggregates and cementitious materials is unclear. This study analyzed the interface's static structure, dynamic characteristics, and binding energy. The interaction mechanisms between acid and alkali aggregates and hydrated calcium silicate and the modification effect of EVA were compared. The calculation results of relative density distribution and radial distribution function verified the difference in the structure of EVA-modified acidic or alkaline interfaces. EVA polymer chains significantly blocked the flow of Ca atoms in CaO at the CaO/C-S-H interface and weakened the van der Waals effect at the interface. The mean square displacement and time correlation function analysis indicate that all unmodified interfaces have stable interface structures. After EVA modification, the stability of CaCa-HW decreased significantly, hindered the generation of hydration products, and verified the weak Ca atom transport at the CaO/C-S-H interface. In addition, the adhesion energy of SiO2/C-S-H and CaO/C-S-H after EVA modification decreased by 6% and 14.8%, respectively, quantifying the modification effect of EVA.

KEYWORDS:

• Aggregate
• calcium silicate hydrate
• ethylene vinyl acetate
• interaction
• molecular dynamics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financially supported by the Henan Province Science and Technology Research Project [grant number: 232102320173], The Innovative Funds Plan of Henan University of Technology [grant number: 2020ZKCJ21], and Zhengzhou Collaborative Innovation Project [grant number: 21ZZXTCX09].