Contact-hardening behavior of calcium silicate hydrate powders

Journal article, 2018

Calciumsilicate hydrate (C-S-H) synthesized by a hydrothermal process fromlime and siliceous materials was oven-dried and compressed into compacts. The microstructure and compaction properties of the resulting powderswere characterized. The results showthat the powders containing an amorphous structure become hardened compacts immediately after compression. Compacts with high strength but a relatively lower bulk density were produced. Amorphous C-S-H plays a key role in the bonding formation during powder compaction. According to the Heckel plots, particle rearrangement and plastic deformation were involved in the compaction of C-S-H powders. Point contact between C-S-H particles due to particle rearrangement dominates at a low compression pressure (i.e., < 20MPa). Van derWaals forces and hydrogen bonding are the main bonding types. Plastic deformation occurs at a higher compression pressure (i.e., > 60MPa), which results in surface contact. Consequently, a solid bridge forms, and the strength of compacts increases rapidly. These findings provide novel insight into the utilization of materials containing amorphous calcium silicate hydrate.