Some characteristics of high-strength structural concrete: Part 2
The 68-storey Scotia Plaza tower in Toronto is an outstanding example of the use of concrete technology to achieve high-performance, high-strength concrete. Cementitious hydraulic slag, silica fume, and a superplasticizer were combined with CSA type-10 Portland cement and high-quality aggregates to produce very workable high-strength concrete. During the course of construction, data were published suggesting the possibility of the strength regression of test cylinders of some silica fume concretes after long exposure to low humidity. To address this concern, tests were made at ages of 1 year and 2 years on specimens drilled from columns in the structure. These data were published in Volume 18 of this journal. In this note, results of additional tests at 7 years are described and compared with the results of earlier tests. Key words: high strength, slag, silica fume, permeability, rapid chloride permeability, petrographic examination, superplasticisers.