SCOPE AND FIELD OF APPLICATION
This NORDTEST method is intended for the determination of the ultrasonic pulse velocity in concrete employing a s.c. dual recording equipment. Ultra sound is sound with a frequency above 20 kHz, (see Note 1).
The method may be used for investigation of test specimens or part of a concrete object concerning the uniformity of strength in the concrete, for delineate regions with deviating quality or of damaged concrete, for evaluation of time dependent characteristics of the concrete that have been caused by the hydration of the concrete prior to its setting and during its curing. The method may also be used for the detection of cracks which run across the path of sound.
The method is not intended to replace the ordinary strength tests of concrete. But the strength of concrete may be evaluated by means of this method under the condition the equipment has been calibrated against concrete with a known compression strength and of the same composition and temperature as the concrete whose compression strength one intends to evaluate.
The ultrasonic velocity can, in connection with other non-destructive methods, e.g. NT BUILD 210 or 211, provide more information about the concrete than what each test used separately can provide.
The age of the concrete is not considered in the method.
The method agrees in the main with IS0 DP 8046 Concrete, (hardened) - Determination of the ultrasonic pulse velocity, with regard to the parts of the IS0 method that describe how one determines the velocity of the ultra sound by means of a dual recording equipment transversally directed through the concrete. The IS0 method also states other, less accurate ways of determining the ultrasonic velocity.