The Accelerated Curing Method is a technique used to achieve high compressive strength in concrete at an earlier stage. It is also utilized to determine the 28-day compressive strength of concrete in just 28 hours, in accordance with the guidelines set by IS 9013-1978. This method is particularly beneficial in the prefabrication industry as it allows for the removal of formwork within 24 hours, reducing the cycle time and resulting in cost savings.
Various techniques are commonly used for accelerated curing, including steam curing at atmospheric pressure, warm water curing, boiling water curing, and autoclaving. These methods are especially useful in achieving high early age strength, which is crucial in prefabrication applications. By using accelerated curing techniques, the concrete gains the required strength in a shorter amount of time, making it possible to remove the formwork earlier and accelerate the overall production process.
Compressive Strength Test using Accelerated Curing Method
To determine the 28 days strength of test specimens, certain steps need to be followed. Firstly, the specimens must be stored in a moist environment with at least 90% humidity for 23 hours and 15 minutes. Next, flat steel cover plates must be placed over the specimens to prevent distortion. The specimens are then carefully lowered into a curing tank, where they must remain completely immersed for 3 and a half hours with 15 minutes. The water in the curing tank must be at boiling point (100°C) when the specimens are placed in it.
After curing for 3 and a half hours, the specimens are carefully removed from the boiling water and cooled by immersing them in a cooling tank with a temperature of 27°C plus or minus 2°C for 2 hours. Once cooled, the specimens can be removed from the mould and tested for their accelerated compressive strength (Ra) in N/mm2.
To determine the 28 days compressive strength, the following formula can be used: predicted 28 days compressive strength (R28) equals 8.09 plus 1.64 Ra, where Ra is the accelerated compressive strength and R28 is the predicted compressive strength at 28 days.