Types of Special Concrete

Special Concrete means the concrete used or made for special cases, such as:

Frequently, concrete may be used for some special purpose for which special properties are more important than those commonly considered. Sometimes, it may be of great importance to enhance one of the ordinary properties. These special applications often become apparent as new development using new materials or as improvements using the basic materials. Some utilize special aggregates (lightweight aggregate, steel fiber, plastic fiber, glass fiber, and special heavy aggregate).

Some special properties — increased compressive and tensile strength, water proofing, and improved chemical resistance are achieved with polymers, either as admixtures or surface treatment of hardened concrete. Admixtures for coloring concrete are available in all colors. The oldest and cheapest is perhaps carbon black. Admixtures causing expansion for use in sealing cracks or under machine bases, etc., include powdered aluminum and finely ground iron. Special admixtures are available for use where the natural aggregate is alkali reactive, to neutralize this reaction. Proprietary admixtures are available that increase the tensile strength or bond strength of concrete. They are useful for making repairs to concrete surfaces.

Uses and Applications of Special Concrete

1. Special concrete is used in extreme weather.

2. HPC has been used in large structures such as the Petronas Towers and the Troll Platform. Petronas Towers was the tallest concrete building in the world built in Malaysia in the mid-1990s. In 1998, the deepest offshore platform, the Troll platform, was built in Norway — a structure taller than the Eiffel Tower.

3. Good cohesiveness or sticky in mixes with very high binder content

4. Some delay in setting times depending on the compatibility of cement, fly ash and chemical admixture

5. Slightly lower but sufficient early strength for most applications

6. Comparable flexural strength and elastic modulus

7. Better drying shrinkage and significantly lower creep

8. Good protection to steel reinforcement in high chloride environment

9. Excellent durability in aggressive sulphate environments

10. Lower heat characteristics

11. Low resistance to de-icing salt scaling

12. PC pipes with good resistance to chemical attack from both acidic and caustic effluents inside the pipe, and from chemical attack on the outside of the pipe.