Study on the Interaction of Na-montmorillonite Clay with Polycarboxylates

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Title: Study on the Interaction of Na-montmorillonite Clay with Polycarboxylates

Author(s): Serina Ng and Johann Plank

Publication: Special Publication

Volume: 288

Issue:

Appears on pages(s): 1-15

Keywords: cement; clay; interaction; montmorillonite; polycarboxylate.

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).