Tests on Concrete

 TESTS ON CONCRETE

There are certain types of tests performed on concrete in order to ensure it's workability, tensile strength, etc. Different types of tests are used to determine different results.

1. Rebound Hammer Test:

Rebound Hammer Test is used to determine the compressive strength of concrete. Apparatus consists of a Rebound Hammer or Schmidt Hammer. Hammer consists of a spring controlled mass contained in a tubular house which slides on a plunger. When the rebounded hammer plunger is pressed against the surface of concrete, the spring controlled mass is released and made to hit the concrete surface and rebound. The amount of rebound is a measure of hardness of concrete surface. This rebound is measured on a graduated scale and the measured value is called the Rebound Number. Concrete with high strength will reveal a higher Rebound number and vice versa.

2. Penetration Resistance Test: 

This test is used to determine the uniformity and assess the in-situ strength of concrete. Test is conducted using Windsor Probe test machine. A steel probe is fired on the surface of concrete sample with a sudden explosion. The amount of penetration is inversely proportional to the strength of concrete. Strength of aggregates and nature of formed surfaces of concrete can influence the result of this test. 

3. Ultrasonic Pulse Velocity Test: 

Idea behind Ultrasonic Pulse Velocity test is to measure the time taken by an ultrasonic pulse to pass through a concrete sample. This test is performed in-situ to assess the quality of concrete ( homogeneity, check presence of cracks and overall imperfections ). The concrete sample is induced with a series of waves. A transducer is placed on the other side to detect the ultrasonic waves. The speed of wave is affected by the shape, size and geometry of concrete. Concrete with homogeneity and uniformity will allow the waves to pass through quickly and vice versa. 

4. Core Sampling of concrete:

Concrete core or core sampling makes use of a rotary cutting tool with diamond bits. This is used to obtain a cylindrical specimen . The cores are documented on site. ( visually observed and photographed ) Next it is soaked in water, made even over it's surface and tested for compression in a moist condition as per BS: 1881: Part 4: 1970. 

5. Water Absorption Test: 

This test is used to determine the durability of concrete. In this 3 cubes of 150mm concrete sample are taken and and placed in a curing tank for 28 days or after 24 hours the concrete is removed from the mold and sent to a third-party laboratory for curing. The testing is done in accordance with BS: 1881-122.