SOME CHARACTERISTICS OF HIGH-STRENGTH STRUCTURAL CONCRETE .2.

The 68-storey Scotia Plaza tower in Toronto is an outstanding example of the use of concrete technology to achieve high-performance, high-st rength concrete. Cementitious hydraulic slag, silica fume, and a super plasticizer were combined with CSA type-10 Portland cement and high-qu ality aggregates to produce very workable high-strength concrete. Duri ng the course of construction, data were published suggesting the poss ibility of the strength regression of test cylinders of some silica fu me concretes after long exposure to low humidity. To address this conc ern, tests were made at ages of 1 year and 2 years on specimens drille d from columns in the structure. These data were published in Volume 1 8 of this journal. In this note, results of additional tests at 7 year s are described and compared with the results of earlier tests.