Title:
Study on the Interaction of Na-montmorillonite Clay with Polycarboxylates
Author(s):
Serina Ng and Johann Plank
Publication:
Symposium Paper
Volume:
288
Issue:
Appears on pages(s):
1-15
Keywords:
cement; clay; interaction; montmorillonite; polycarboxylate.
DOI:
10.14359/51684244
Date:
9/14/2012
Abstract:
The negative impact of sodium montmorillonite clay on dispersion effective¬ness of two polycarboxylates consisting of methacrylate acid: MPEG methacrylate ester at molar ratios of 6:1 and 1.5:1 was investigated. When 1% by weight of cement (bwoc) of clay was present, cement spreads decreased by up to 60% while PCE sorption soared to ~ 400 mg/g clay (~ 100 times higher than on Portland cement). The PCEs mainly undergo chemisorption by intercalation between the alumosilicate layers via their poly(ethylene oxide) side chains. Additionally, to a minor extent (~ 15%), adsorption via electrostatic attraction to the positively charged clay surfaces takes place. Polyglycols can be effectively used as a sacrificial agent to protect PCEs possessing high grafting density from the nega¬tive effects of clay, while more anionic PCEs benefit, however to a certain extent only, from the addition of highly anionic polyelectrolytes such as poly(methacrylic acid).