Describe about the Rebound Hammer test method and the ultrasonic pulse testing method for determining the strength of concrete.
Rebound Hammer Test Method:-
It consist of a spring control hammer that slides on a plunger within a tubular housing. When the plunger is pressed against the surface of the concrete, the mass rebound from the plunger. It reacts against the force of the spring. The hammer impacts against the concrete and the spring control mass rebounds, taking the rider with it along the guide scale. By pushing a button the can be held in position to allow the reading to be taken. the distance travelled by the mass, is called the rebound hammer.
Ultrasonic Pulse Testing Method:-
Ultrasonic pulse velocity method consist of measuring the time of travel of an ultrasonic pulse , passing through the concrete to be tested. The pulse generator circuit consist of electronic circuit for generating pulses and a transducer for transforming these electronic pulse into mechanical energy having vibration frequencies in the range of 15 to 50 KHz. The time of travel between initial onset and the reception of the pulse is measured electronically.
Explain Kelly Ball to measure the workability of concrete. Mention the limitation of the test.
Differentiate between creep and shrinkage of concrete.
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