Rebound hammer procedure https://en.wikipedia.org/wiki/Schmidt_hammer http://electicalreviews.blogspot.in/
pull off test procedure http://www.dfdinstruments.co.uk/topics/Study5-ASTM-D4541.htm
The Impact-Echo Method http://www.ndt.net/article/0298/streett/streett.htm
Windsor Probe http://theconstructor.org/concrete/penetration-resistance-testconcrete/2853/
Ultrasonic pulse velocity test https://en.wikipedia.org/wiki/Ultrasonic_pulse_velocity_test http://www.engineeringcivil.com/ultrasonic-testing-of-concrete.html
Ground-penetrating radar https://en.wikipedia.org/wiki/Ground-penetrating_radar http://www.geophysical.biz/gpr3.htm