ABSTRACT
Abstract A series of concretes with 0, 25, 35 and 50% mass replacement of portland cement by ground granulated blastfurnace slag were tested for de-icer salt scaling resistance using a modified ASTM C672 test where scaling mass loss was measured. In one series of tests, finishing times were varied, while in another series of tests, curing periods were varied. In addition, inclined, formed surfaces, similar to those of highway barrier walls, were tested. The results indicate that scaling performance is highly sensitive to these variables. Field trials were also undertaken which show that the laboratory test is too severe. Keywords: De-icer salt scaling; slag; fly ash
1 Introduction
In the Canadian CSA A23.1 standard, pavement, sidewalk and curb concrete which is to be exposed to freezing in the presence of de-icer salts is required to have a maximum w/cm = 0.45, a minimum 28 day specified strength of 32 MPa and contain 5 to 8% air (for 20 mm aggregate). Bridge decks require 35 MPa strength and maximum w/cm = 0.40. Due to poor performance in the Ontario-modified ASTM C672 de-icer salt scaling laboratory test, the Ontario Ministry of Transport currently limits slag replacement levels to 25%, fly ash to 10%, or a combination not exceeding 25%. In spite of this, field experience shows that this laboratory tests are unnecessarily restrictive and that slag contents of at least 35%, and fly ash contents of 20% (Class F ash) are acceptable [1].
