07-04-2017, 09:31 AM
Non-destructive testing is a method of testing existing concrete structures to evaluate the strength and durability of the concrete structure. In the non-destructive test method, without loading the specimen to failure (that is, without destroying the concrete) we can measure the strength of the concrete. Nowadays this method has become a part of the quality control process. This test method also helps us investigate the depth of cracks, micro cracks and deterioration of concrete.
Several non-destructive concrete test methods have been developed to analyze the properties of the hardened concrete given below.
1. TEST OF SURFACE HARDNESS
These are indentation type, include the Williams test gun and impact hammers, and are used only for estimating the strength of the concrete.
2. REBOUND HAMMER PROOF
The rebound hammer test measures the elastic rebound of the concrete and is mainly used for estimating the strength of the concrete and for comparative research.
3. PENETRATION AND PULSE TECHNIQUES
These include the use of the simbi hammer, spit pins, Windsor probe, and crawl test. These measure the penetration and the resistance to the removal of the concrete and are used for the estimation of the resistance, but also can be used for comparative studies.
4. DYNAMIC OR VIBRATION TESTS
These include resonance frequency and mechanical ultrasound and pulse rate methods. These are used to evaluate the durability and uniformity of the concrete and to estimate its strength and elastic properties.
5. COMBINED METHODS
Combined methods involving ultrasonic pulse velocity and rebound hammer have been used to estimate the strength of the concrete.
6. RADIOACTIVE AND NUCLEAR METHODS
These include X-ray and gamma-ray testing to measure the density and thickness of the concrete. In addition, neutron scattering and neutron activation methods are used for the determination of moisture and cement content.
7. MAGNETIC AND ELECTRICAL METHODS
Magnetic methods are mainly concerned with determining reinforcement coverage in concrete, while electrical methods, including microwave absorption techniques, have been used to measure the moisture content and the thickness of the concrete.
8. ACOUSTIC EMISSION TECHNIQUES
These have been used to study the initiation and growth of cracks in concrete.
Several non-destructive concrete test methods have been developed to analyze the properties of the hardened concrete given below.
1. TEST OF SURFACE HARDNESS
These are indentation type, include the Williams test gun and impact hammers, and are used only for estimating the strength of the concrete.
2. REBOUND HAMMER PROOF
The rebound hammer test measures the elastic rebound of the concrete and is mainly used for estimating the strength of the concrete and for comparative research.
3. PENETRATION AND PULSE TECHNIQUES
These include the use of the simbi hammer, spit pins, Windsor probe, and crawl test. These measure the penetration and the resistance to the removal of the concrete and are used for the estimation of the resistance, but also can be used for comparative studies.
4. DYNAMIC OR VIBRATION TESTS
These include resonance frequency and mechanical ultrasound and pulse rate methods. These are used to evaluate the durability and uniformity of the concrete and to estimate its strength and elastic properties.
5. COMBINED METHODS
Combined methods involving ultrasonic pulse velocity and rebound hammer have been used to estimate the strength of the concrete.
6. RADIOACTIVE AND NUCLEAR METHODS
These include X-ray and gamma-ray testing to measure the density and thickness of the concrete. In addition, neutron scattering and neutron activation methods are used for the determination of moisture and cement content.
7. MAGNETIC AND ELECTRICAL METHODS
Magnetic methods are mainly concerned with determining reinforcement coverage in concrete, while electrical methods, including microwave absorption techniques, have been used to measure the moisture content and the thickness of the concrete.
8. ACOUSTIC EMISSION TECHNIQUES
These have been used to study the initiation and growth of cracks in concrete.
