Molecular insight in the wetting behavior of nanoscale water droplet on CSH surface: Effects of Ca/Si ratio

Abstract

The distribution state and wettability of water molecules on the Calcium silicate hydrate (CSH) surface closely affect the transport behavior of water on CSH gel pores, thus affecting the durability of concrete. To understand the wetting behavior of water droplets on the CSH gel interface with different Ca/Si ratios, this paper focuses on the local structure, ionic pairs, hydrogen bonds, orientation characteristics and dynamic properties of water molecules on the CSH interface based on molecular dynamics simulation. At the molecular level, the water droplets have a larger contact angle at the CSH surface with a low Ca/Si ratio because the CSH with a low Ca/Si ratio has a dense structure and makes it difficult for water molecules to penetrate the silicate chain. Analysis reveals that the dense silicate chains tend to absorb and restrict water molecules in the form of static electricity. The orientation distribution of water molecules at different positions on the CSH interface reveals the driving force of wetting behavior. The results of dynamic properties analysis show that CSH with a high Ca/Si ratio has better wettability to water droplets.