Wednesday, May 8, 2019

Concrete Test on Green or Fresh Concrete and Hardened Concrete

Concrete test on green or fresh concrete and hardened concrete is required to check concrete quality such as workability, impermeability, compressive strength etc. We described all concrete test on green concrete and hard concrete.

Test on Green or Fresh Concrete

  1. Workability test
  2. Initial and Final Setting time test
  3. Air content
  4. Density or Unit wei1ght

Workability test

Workability or Slump is a measure of consistency, or relative ability of the concrete to flow and pour in any shape of form work. If the concrete can’t flow because the consistency or slump is too low, there are potential problems with proper consolidation. If the concrete won’t stop flowing because the slump is too high, there are potential problems with mortar loss through the form work, excessive form work pressure, finishing delays and segregation.

Concrete Test on Green or Fresh Concrete and Hardened Concrete

Initial and Final Setting time test

The initial setting time and final setting time are the time intervals required for the mortar sieved from concrete mixture to reach the prescribed penetration resistance after the initial contact of cement and water.

Air content

Air-entrained concrete is typically specified in areas of the country where frost-related damage can occur. The measurement of air content in fresh concrete of normal density is typically performed using the pressure method.

Density or Unit weight

The density or unit weight of concrete is measured using a Type B pressure meter to verify agreement with the approved project mix design. The information obtained through this test can also be used to determine yield and relative yield, which helps you verify that you are getting the volume of concrete you ordered and paid for. You can also use this data to calculate the air content of the mix.

Test on Hardened Concrete

There are two types of test for hardened concrete.

  1. Destructive test
  2. Non-Destructive test

Destructive Tests on Concrete

  1. Compressive strength test on cubes
  2. Compressive strength test on cores
  3. Tensile strength test

Compressive Strength test on Cubes

Concrete compressive strength is determined by cube strength test of concrete.
Concrete cube specimens are tested by compression testing machine after 7 days curing or 28 days curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails.

Concrete Test on Green or Fresh Concrete and Hardened Concrete

Compressive Strength test on Cores

Concrete cylindrical cores are cut from the finished structure with a rotary cutting tool. The core is capped and tested in compression to give a measure of the concrete strength in the actual structure. The ratio of core height to diameter and the location where the core is taken affect the strength. The strength is lowest at the top surface and increases with depth through the element.

Tensile Strength test

The concrete structures are highly vulnerable to tensile cracking and hence the determination of tensile strength of concrete is very important.

Non-Destructive Test on Concrete

  1. Rebound hammer test ( hardness test )
  2. Ultrasonic pulse velocity test
  3. Pull out test

Rebound Hammer test

Rebound hammer test is required to find out the compressive test of concrete by using rebound hammer.
Rebound hammer test is a Non-destructive test (NDT test of Concrete) which is used to test the Compressive strength of concrete without any damage. Moreover, the best part of Rebound hammer test is concrete can be tested in real time at the site instead of going to the lab without any damage.

Ultrasonic Pulse Velocity test

Ultrasonic pulse velocity (UPV) test is an nondestructive test to check the quality of concrete. In this test, the strength and quality of concrete is assessed by measuring the velocity of an ultrasonic pulse passing through a concrete structure.
This test is conducted by passing a pulse of ultrasonic through concrete to be tested and measuring the time taken by pulse to get through the structure. Higher velocities indicate good quality and continuity of the material, while slower velocities may indicate concrete with many cracks or voids.

Pull Out Test

The principle behind pull out testing is that the test equipment designed to a specific geometry will produce pull-out forces result that closely correlate to the compressive strength of concrete. This correlation is achieved by measuring the force required to pull a steel disc or ring, embedded in fresh concrete, against a circular counter pressure placed on the concrete surface concentric with the disc/ring.

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