Title: Assessing the deicer salt scaling resistance of concrete containing supplementary cementing materials

Author(s): Marc Jolin;R.D. Hooton;B.Fournier;R. Gagne;J. Marchand;R. McGrath;A. Delagrave;N.J. Popoff;J.-C. Leduc;J.C. Flynn;B. Pope;Y. Brousseau

Publication: CRC

Volume:

Issue:

Appears on pages(s):

Keywords: fly ash, blast-furance slag, slag, de-icer salt, SCM

DOI:

Date: 12/19/2019

Abstract:
Fly ash and ground granulated blast-furnace slag are now commonly used in the production of concrete mixtures for residential, commercial and industrial applications. In addition to reducing the amount of Portland cement added to concrete (which often decreases the cost of production), the addition of fly ash and slag also contributes to improve numerous physical and durability-related properties of the material and offers significant benefits from an environmental standpoint. Despite their numerous advantages, the use of SCM for the production of concrete structures likely to be exposed to cold climates is often impeded by the fact that laboratory investigations invariably indicate that partial replacement of Portland cement with fly ash or slag markedly reduces the frost resistance of concrete in presence of de-icing chemicals. The conclusions of these numerous laboratory studies are apparently, however, not corroborated by field experience. The discrepancy between the two series of observations has led numerous researchers to question the reliability of the accelerated test procedure used in the laboratory to assess the de-icer salt scaling resistance of concrete. The main objective of this research is to understand the detrimental influence of fly ash and slag on the de-icer salt scaling behavior of concrete as evaluated by laboratory procedures. Various ways to improve the scaling durability of concrete mixtures containing SCM will be explored. A great deal of effort will also be spent on the enhancement of the reliability of existing test procedures to assess the de-icer salt scaling performance of concrete.The first efforts consisted in an investigation of the influence of various test parameters. Indeed, as previously emphasized, the ASTM C 672 has been extensively criticized for the relatively high variability of its test results This first task of the project is therefore entirely devoted to the investigation of the influence of the temperature cycle characteristics on the de-icer salt scaling performance of concrete (rate of freezing, minimal freezing temperature and length of freezing period). The second task is focused on the systematic study of the effects of various curing regimes on the deicer salt scaling resistance of concrete mixtures incorporating SCM. For each of the seven mixtures selected, the influence of three different curing regimes currently used in practice will be tested. Also a fourth series of samples will be cast in molds in which a synthetic membrane is placed at the bottom. This approach is the one suggested by the "Bureau de normalisation du Québec" (standard NQ-2621- 900-1) after it was reported that this procedure significantly reduced bleeding. A sorptivity test should help to better understand the effect of bleeding, mixture design, and curing conditions on the pores network and on the transport properties of the paste located just beneath the exposed top surface (0 to 10 mm) of the sample. The influence of fly ash and ground granulated blast furnace slag on the specific microstructure of paste located near concrete surface (0-5 mm) and the ice formation will also be investigated. This part of the study will be divided into two steps. Study of the microstructure of concrete skin containing supplementary cementitious materials was performed on samples cored from concrete sidewalks in Montreal.