Title: Influence of Fly Ash and Slag on Deicer Salt Scaling Resistance of Concrete

Author(s): C. Talbot, M. Pigeon, and J. Marchand

Publication: Symposium Paper

Volume: 192

Issue:

Appears on pages(s): 645-658

Keywords: air entrainment; fly ash; sawing; scaling; slags; spacing factor; troweling

DOI: 10.14359/5776

Date: 4/1/2000

Abstract:
Over the past decades, numerous laboratory studies have clearly indicated that the use of supplementary cementing materials, and particularly fly ash, can significantly reduce the scaling durability of properly air-entrained concrete. Despite the great deal of research done on the topic, the reasons behind the detrimental influence of fly ash remain unclear. In order to bring more information on the subject, an investigation of the influence of fly ahs on the deicer salt scaling resistance of concrete has been recently carried out. Test variables include water/binder ratio (.40, .50 and .66), class of fly ash (two class C and a class CF), and the percentage of replacement of the cement by the fly ash (, 20 and 40%). An additional series of mixtures was prepared with 25% slag as cement replacement. All deicer salt scaling tests were performed according to a modified version of ASTM C 672 on both troweled and sawed surfaces. The air-void characteristics of all mixtures were determined according to ASTM C 457, and the microstructure of selected mixtures was studied by mans of SEM observations. All test results confirmed that the use of fly ash and slag can reduce the salt scaling durability of concrete as determined in the laboratory. The influence of fly ash and slag does not appear to be linked to their effect on the material pore structure. An explanation linked to its influence on the characteristics of the air-void network is suggested.