IN-SITU STRENGTH OF SUBAQUEOUS CONCRETE.

Cylindrical test specimens of 3-12-inch and 7-inch slump concretes underwent curing, within 1 hour after fabrication, in 1 a sealed vessel filled with 47F seawater at 269 psi to simulate a 600-foot oceanic depth, 2 in 47F seawater at atmospheric pressure to ascertain the effect of temperature, and 3 in 73F fog as the standard for compressive strength. Specimens cured as in 1 and 2 were cast in segmented molds held intact by rubber bands to permit concrete swellage while curing and deformation when loaded to failure under uniaxial compression. Compressive strengths were determined at ages 2, 4, 6, and 8 days. Maximum size of gravel aggregate was 1 inch, equivalent cement Type 111 factor was 7 bags, and watercement ratios were 0.52 for low-slump and 0.63 for high-slump concretes. The combined effect of low aqueous temperature and high hydrostatic pressure caused the 7-day strengths, attainable by curing in 73F fog, to be reduced nearly one-half for low-slump and somewhat more than one-third for high-slump concretes. Further experimentation is needed to ascertain 1 the effect of cement brand on subaqueous compressive strength during the first 24 hours, and 2 the 14- and 28-day subaqueous compressive strengths of concretes identical to those described herein. Author