The digital compression testing machine is a specialized equipment used to assess the compressive strength of hardened concrete in the form of cubes and cylinders. This machine is designed to apply a controlled load to the specimen and measure the amount of force required to cause it to fail under compression. By subjecting concrete specimens to increasing amounts of load until they fracture, the digital compression testing machine provides valuable information about the strength and durability of the concrete, which is crucial for assessing its suitability for various construction applications. The results obtained from the testing machine are used to ensure that the concrete used in construction projects meets the required standards and specifications, and to make informed decisions about the quality and safety of the hardened concrete. Overall, the digital compression testing machine plays a vital role in determining the compressive strength of concrete, which is an essential parameter in evaluating the structural performance of concrete structures.
Procedure as per IS 516 – Methods of tests for strength of concrete
To conduct a compression test on a specimen, follow these steps. First, place the specimen centrally on the clean lower platen, leaving a small clearance between the upper platen and the top of the specimen. Close the pressure release valve and adjust the zero knob to make the digital display read “Zero”. Set the display unit to “Peak Hold” mode to hold the maximum load reading.
Next, start applying the load at the specified pace rate, which can be adjusted using the slow/fast knob. The pace rate is indicated by the color on the indicator – red for a high pace rate, yellow for a low pace rate, and green for an exact match with the set rate. As soon as the sample fails, release the pressure slowly by opening the valve. The digital display will hold the maximum load reading at which the sample failed.
Note down the pattern of failure and calculate the compressive strength in N/mm2 or kg/cm2. For a 15 cm cube specimen, the pace rate is set at 5.15 kN/s. Before starting another test, clean the lower platen and reset the digital display to “Zero” by depressing the “Reset” switch.