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.
Related References:
1. A. A. Jeknavorian, “Polycarboxylate Superplasticizers: What have we learned in the past 20 years?” The Concrete Producer, April-May 2016, pp 35-38.
2. Jeknavorian, A.; Jardine, L.; Ou, C.; Koyata, H.; and Folliard, K., “Interaction of Superplasticizers with Clay-Bearing Aggregates,” Seventh CANMET/ACI International Conference Superplasticizers and Other Chemical Admixtures in Concrete, Berlin, ACI SP 173-04, 1997, 55-82. Editor: V.M. Malhotra.
3. Lange, A., and Plank, J., “Study on the foaming behavior of allyl ether-based polycarboxylate superplasticizers,” Cement and Concrete Research, V. 42, No. 2, 2012, pp. 484-489. doi: 10.1016/j.cemconres.2011.11.017
4. Wang, L.; Wang, Y.; Liu, Y.; Chu, Z.; and Li, Y., “Study on the Foaming Behavior of Polycarboxylate Superplasticizers with Hydrophobic Side Chains, Eleventh International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Ottawa, CANADA, July 2015. Editors: V. Mohan Malhotra, Pawan R. Gupta, and Terence C. Holland.
5. ASTM C185 - 15a Standard Test Method for Air Content of Hydraulic Cement Mortar, Vol. C04.01, 2015.
6. Magarotto, R.; Maroatti, F.; and Moro, S., “The Influence of Polycarboxylates on the Interaction with Defoaming System,” 13th International Conference on Recent Advances in Concrete Technology and Sustainability Issues. Ottowa, July 2015. Editors: V. Mohan Malhotra, Pawan R. Gupta, and Terence C. Holland.
7. Garret, P. R., “Defoaming: Theory and Industrial Applications,” Surfactant Science Series Volume 45, Marcel Dekker, Inc. 1993, p13.
8. C. Ozyildirim and D. S. Lane, “Evaluation of Self-consolidating concrete,” Virginia Transportation Research Council, June 2003, VTRC 03-R13.
9. Hover, K., “Analytical Investigation of the Influence of Air Bubble Size on the Determination of the Air Content of Freshly Mixed Concrete,” Cement, Concrete and Aggregates, V. 10, No. 1, 1988, pp. 29-34. doi: 10.1520/CCA10028J
10. ACI 201.2R-16 “Guide to Durable Concrete,” American Concrete Institute, 2016.
11. ASTM C457 / C457M - 16 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete,” Volume 04.02, 2016.
12. ASTM C666 / C666M - 15 “Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing,” Volume 04.02, 2016.
13. “Super Air Meter gauges void spacing, passes AASHTO muster,” Concrete Products, March 2015.