High Early Strength Concrete
It is possible to create high-early-strength concrete with common concrete ingredients, unique admixtures, and specific concreting techniques. Compared to regular concrete, high-early-strength concrete, often known as fast track concrete, reaches its designated strength earlier in life.
It can take the concrete anywhere from a few hours to many days to reach the required strength. High-early-strength concrete is used for fast-track paving, high-speed cast-in-place construction, cold-weather construction, quick pavement repairs to minimize traffic delays, and precast concrete for quick element manufacture
How Is High-Early-Strength Concrete Developed?
One or more of the following tactics can be used to get the high early strength. Based on the time frame for the concrete to reach its intended strength, the high early strength production technique was chosen.
1. Portland Cement Type III
Portland cement that responds more quickly than conventional cement or Type I cement is known as Type III, or high-early-strength cement. In three days, the high-early-strength cement reaches around 70% of its 28-day strength. Concrete built with Type III cement takes around 45 minutes to set initially and about 6 hours to set completely.
2. High Cement Content
Adding more cement (400–600 kg/m3) is another method for making concrete with a high early strength.
3. Low Ratio of Materials for Water Cementing
High-early-strength concrete can be made by reducing the water to cementing material ratio by mass by a range of 0.20 to 0.45. High-early-strength concrete has been produced using a water to cement material ratio of 0.32 to 0.42; very-high-early-strength concrete can be produced using a water to cement material ratio of 0.20.
4. Higher Temperature of Newly Mixed Concrete
As the temperature of freshly mixed concrete rises, cement hydration increases. Thus, a rise in the temperature of freshly mixed concrete would accelerate the process of concrete’s strength growth, producing high-early strength concrete.
5. Mixtures of Chemicals
It is possible to create high-early-strength concrete with accelerating admixtures. High early strength concrete can be produced by adding accelerating admixtures, such as calcium chloride, which is standardised by ASTM D 98. The concrete hydrates more quickly and gains strength earlier thanks to the accelerating additive.
6. Additional Cement-Based Materials
Extra cementitious material can be added to concrete to provide high-early-strength concrete. Concrete develops more early strength when ground granulated blast furnace slag and a higher curing temperature are combined.
7. Curing using Steam or Autoclave
One efficient method for producing high-early-strength concrete is steam or autoclave curing. The compressive strength of concrete obtained in 24 hours under autoclave conditions is equal to the compressive strength of concrete obtained in 28 days under standard curing conditions.
Together with the absence of effloresce, concrete under autoclave curing exhibits improved sulphate resistance and decreased drying shrinkage as compared to concrete under typical curing circumstances.
8. Insulation to Preserve Hydration Heat
Another method for producing high-early strength concrete is to utilise insulation to trap heat in fresh concrete.