TESTING OF HARDENED CONCRETE SPECIMENS

Large Prisms Installed at Treat Island
Visual Examination and Rating System
All test prisms are visually examined on an annual basis and evaluated using a rating system shown below.

Rating System RATING OF 0 Less than 15 aggregates are exposed RATING OF 1 More than 15 aggregates are exposed RATING OF 2 50% of the aggregates immediately below the surface are exposed RATING OF 3 80% of the surface aggregates are exposed RATING OF 4 Surface aggregates are exposed over 20% of their perimeter RATING OF 5 90% of the surface aggregates are exposed over one half of their perimeter RATING OF 6 95% of volume of specimen remaining RATING OF 7 80% of volume of specimen remaining RATING OF 8 50% of volume of specimen remaining RATING OF 9 20% of volume of specimen remaining RATING OF 10 Specimen disintegrated

Pulse-Velocity Measurements
Ultrasonic pulse-velocity measurements are also taken on the prisms on an annual basis using a portable digital unit. The velocities are measured between the centre of the prisms ends. The results of the pulse-velocity measurements obtained over periods up to 16 years . Laboratory Specimens The 152 x 305-mm cylinders were tested in compression at various ages in the laboratory. The Young's modulus of elasticity E of concrete was determined on the cylinders at the age of 28 days. All tests were performed in accordance with the ASTM test procedures. In terms of long-term durability of concrete, 10 to 15 years exposure is insufficient to fully evaluate the relative performance of concretes. However, given the very severe exposure conditions at Treat Island, some trends are clearly apparent even now.

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