Abstract
In this study, the most suitable polymer structure was investigated with a view to obtaining excellent cement dispersing ability in a concrete. The polymethacrylic acid dispersant with methoxypolyethylene glycol (PGM-n) pendant (PC) adsorbs on cement particles by its polycarboxyl groups, and shows the cement dispersing effect by both the steric repulsion and hydrophilicity-imparting of its side chains. We found that the number of carboxyl groups should be more than 30 moles in one molar PC, in order that PC could adsorb on cement particles quantitatively. We also found that the side chains' length, n, should be more than 15 when PC displays the high cement dispersing effect even for a hot season like summertime. This is due to the fact that shorter side chains, n≦10, shrink themselves hydrophobicly and also adsorb on cement particles by salting out in cement paste at higher temperature. The relationships among n, the monomer ratio and Mw of PC to get the higher mortar flow were also studied. Still more, the best suited Mw and molecular weight distribution of PC were examined.
