The concrete whose density varies from 3360 to 3840 kg/m3 is known as high-density concrete. However, they can be produced with densities up to 5280 kg/m3 using iron both fine and coarse aggregates.
The high-density concrete is produced using aggregates having a specific gravity of more than 3.5. The commercially used aggregates are barite, magnetite, ilmenite, limonite, etc. Steel and iron aggregates are also used to produce high-density concrete.
The grout used in this concrete should be richer than those used in normal concrete. Extra care must be taken with respect to segregation of heavy aggregates from the rest of the ingredients. The formwork should be made stronger to withstand high loads.
The high-density concrete is widely used in the construction of radiation shields in the nuclear industry.
High Strength Concrete
As per I.S.’s recommended method of mix design, concrete is said to be high-strength concrete if its strength is more than 35 M.Pa.
In modern batching plants, high-strength concrete is produced mechanical manner.
For the production of high-strength concrete due care should be taken about mix proportion shape of aggregates, use of supplementary cementitious materials, superplasticizers, etc.
The methods adopted for making high-strength concrete are as follows:
- High-speed slurry
- Use admixtures
- Inhibition of cracks
- Sulpher impregnation etc.
High-strength concrete is generally used for the construction of pre-stressed concrete bridges, flyovers, high-rise buildings, power projects and other works of greater importance.