Deicing salt scaling resistance of concrete incorporating fly ash and (or) silica fume: laboratory and field sidewalk test data

Sidewalk sections were cast in fall 2002 with three concrete mixtures that consisted of a control concrete, a concrete mixture incorporating 25% fly ash, and a concrete mixture made with a ternary blended cement (fly ash and silica fume). The curing practices consisted of using curing compound and wet burlap. For each of the sidewalk sections, laboratory specimens were cast on site using the concrete from the same batch. Large slabs (1.2 m × 0.9 m) were also cast from which specimens could be cored and tested in the laboratory for compressive strength and deicing salt scaling resistance following the ASTM and the BNQ test procedures. The results were compared to the performance of the sidewalk sections after six winters of outdoor exposure. A similar study was completed on sidewalk sections cast in spring 2002; the objective of the present study being to confirm the results of the previous investigation, and to determine the effect of the time of casting on the scaling resistance of the concrete i.e., performance of sidewalks cast in spring versus that of sidewalks cast in fall. The field evaluation showed that all the concretes cast in fall scaled relatively more than those placed in spring. Both laboratory results and field evaluations have shown that the use of a curing compound increases the scaling resistance of all the concretes investigated. The results also confirmed the adequateness of the BNQ procedure to better evaluate the deicing salt scaling resistance of concrete made with supplementary cementing materials; however, monitoring the sidewalk sections for a longer period of time is still required to confirm the above observations.