Special Types of Concrete
In addition to normal concrete mixes, there are a number of specialized types of concrete for specific applications. A few of these special types of concrete do not look anything like normal concrete during placement.
Some special types of concrete mixes are as follows:
• Mass concrete
• High-strength and/or High-performance concrete
• Roller-compacted concrete (RCC)
• Lightweight concrete
• Preplaced-aggregate (prepacked) concrete
• Heavyweight (high-density) concrete
a. Mass Concrete:
This concrete requires reduction of hydration heat to prevent shrinking and cracking. It is used in dams, spillways, and other large structures.
b. High-strength and/or High-performance Concrete:
High-performance concrete meets special requirements for high elasticity values, high density, watertightness, high resistance to sulfate attack, etc.
c. Roller-compacted Concrete (RCC):
It is used for concreting large areas that contain little or no reinforcement. One type is a low-cement content type used for dams or other very large structures. The other type is a high-cement content type used for pavements.
d. Lightweight Concrete:
This concrete is classified as either low-density, structural lightweight, or moderate-strength lightweight concrete and uses various density aggregates depending on its classification.
Low-density concrete is used primarily for insulation.
Structural lightweight concrete is used as a weight as well as reduced strength.
Moderate-strength lightweight concrete falls between low-density and structural lightweight concrete and has enough strength for use in roofs.
e. Preplaced-aggregate (prepacked) concrete
This concrete is widely used for repair of large concrete structures or in the placement of heavy-weight concrete. It involves placing dry, coarse aggregate in forms and then pumping a highly fluidized cement mixture from the bottom to the top of the forms to make the concrete.
Because the coarse aggregates are in contact with each other, the concrete has very low shrinkage and very good strength.
f. Heavyweight (high-density) concrete
This concrete contains very heavy aggregates such as iron ore, iron shot or punching, iron slag, and other minerals. It is used primarily for radiation shielding, or in the construction of counterweights or deadweights.