Title: High-Performance Concrete Placed Under Water
Author(s): Kamal Gad Sharobim
Publication: Symposium Paper
Appears on pages(s): 445-464
Keywords: Admixtures; blast furnace slag; compactability methods; durability; high-performance
concretes; permeability; setting (hardening) ; strength; underwater
This paper deals with the design and testing of high performance concrete mixtures capable of being cast under water and resisting the sulphates and chlorides existing in soil and ground water. Such concrete shall have high workability, self compactibility, high strength, and high durability. Fourteen concrete mixtures were proportioned to give compressive strength of 56 Mpa after 28 days using high slag blast furnace cement and natural gravel and sand. Five types of admixtures were used to obtain a slump from 200 mm to 250 mm. These concretes were specified to cast the diaphragm walls and 600 piles comprising the foundation of the new Alexandria library, by using a tremie pipe to a depth of 34 meter under water. The properties of fresh concrete such as slump, slump loss, air content, compaction factor, unit weight, and setting time were measured for each mixture. For hardened concrete, characteristics such as compressive strength at different ages, tensile strength, flexural strength, water absorption, coefficient of permeability, drying shrinkage and wetting expansion were determined. A concrete block model and full scale trial panel were cast by tremie pipe to investigate the flowability and self compactibility of concrete mixture. Cores were drilled from both the block model and trial panel at different depths and examined to check the compactibility of concrete without vibrating. In addition, temperature development of concrete used for casting of the trial panel due to the heat of hydration was measured.