In accordance with BS EN 12504-4:2004, the apparatus for the UPV tests
consist of an electrical pulse generator, a pair of transducers and an electronic timing
device for measuring the time interval of the generated pulse to travel from the
transmitting transducer to the receiving transducer. A variable frequency oscillator
complying with the B.S.1881-209:1990 was used for measuring the resonant frequency
of the specimens. Multipurpose grease was used as a couplant between
the concrete surfaces, the faces of the transducers and the vibrating oscillator to reduce
air pockets in between the interfaces. The static testing was undertaken using
hydraulic compression testing machines, a 3000 kN ToniPACT at the University of
Liverpool, and a 600 kN Dartec at Queen’s University Belfast, UK