Cement And Concrete Studies On The Passamaquoddy Tidal Power Project
Huch J. Casey
Appears on pages(s):
Incident to the determination of the type cement and aggregates to be employed on the Passama-quoddy Tidal Power Project, extensive investigations and concrete laboratory tests were made of 45 different cements and- 54 sources of assreaate. The type cements tested were standard portland highearly- strength, alumina, Portland-pozzolan, synthetic pozzolan, natural, and blended cements. The con-crete in this structure was to be subject to exceptionally severe attack from (a) salt watter, daily alternate wetting and drying with (b) semi-in the tidal fluctuations of I8 ft mean and 27 ft maximum range, and alternation 0I c ) severe freezing, including frequent freezing and thawing cycles. Labora- tory tests, supplemented by certain field tests, covered cement characteristics, effect of salt water on mixing and curing, fineness of grinding, heat of hydration, effect of magnesium sulfate test on ef-fect of C3A content, bleeding, optimum mixture, volumetric change, and thawing, modulus of elasticity, freezing thermal flow, flexural strength, and curing procedure for mass concrete. In general the findings indicated that a portland cement of mediumhighfineness (1800-2300) and low C3A content was satisfactory, whereas similar portland cements of high C3A content were less resistant to salt water and alternate freezing; the hiqh-early-strength cements were satisfactory except for problem of heat dissipation: natural cement was weak in slow rate of setting and in low strengths alumina cement was excellent except for heat dissipation inj mass setting: the portland pozzolan and blends of a portland and natural cements showed poor resistance to alternate freezing and thawing. Detailed tabulations and findings are covered in this paper, including characteristics of the cement considered most suitable.