The Morphology of C-S-H in Low Water/Cement Ratio Paste from Nano to Micro Scale

C-S-H is the most important component of hardened cement paste accounting for 60%-70% in hydrating products of OPC and is the most complex material system in material science. Based on the AFM observation of the surface of cement paste with low water/ cement ratio around 0.29~0.35, it has been found that C-S-H has three types of fundamental structure units in nano scale namely granular, platy and cellular, and six types of patterns namely amorphous, granular, platy, agglomerated granular, layer and bulk. These six types of patterns are formed by the three types of structure units. In micro scale, the amorphous type is amorphous matrix composed of cellular nano scale structure unit; the platy structure unit forms the platy to brick like type of C-S-H; the nano particle can be found in granular, agglomerated granular, layer and bulk type of C-S-H. In the nano granular type, the nano particle packs without orientation; the agglomerated granular has obvious tendency to connect with each other; while the layer type is formed by nano granular with notable orientation; there are some granular types that remain on the surface of the bulk and some notable fiber (the diameter in nano size) bundle can be found in the crack of bulk type, thus the bulk forming also from closely packed nano granular types.