Title:
Overview of Defoaming Technologies for Polycarboxylate-Based Superplasticizers
Author(s):
Ara A. Jeknavorian
Publication:
Symposium Paper
Volume:
329
Issue:
Appears on pages(s):
185-200
Keywords:
polycarboxylate; defoamer; antifoam; air content; air-void quality; spacing factor
DOI:
10.14359/51711214
Date:
9/26/2018
Abstract:
Polycarboxylate-based chemical admixtures are invariably formulated with defoaming agents to mitigate unwanted air produced by adding such polymers during the manufacture and placement of concrete mixtures. Effective defoaming additives are by nature highly hydrophobic, and thus have very limited solubility in aqueous chemical admixture products, which can present challenges for both admixture formulators and concrete producers. Numerous approaches have been used to create stable polycarboxylate-defoamer formulations including continuous mechanical agitation, emulsification, co-solvents, grafting hydrolyzable defoaming agents, and ionic association between the defoamer and carboxylate functional groups in the polymer backbone. Based on a detailed discussion of the concerns that can occur with formulating admixtures with defoamers, a specification which includes criteria for product stability, air control in both air-entrained and non air-entrained concrete, and air-void quality of air-entrained concrete, is proposed.