A method of and apparatus for testing the safe-loading characteristics of an existing concrete floor slab (12) by drilling out or otherwise isolating a core (13) so that it is capable of free vertical movement relative to the remainder of the slab. The core (13) is drilled carefully so that the sub-base below the slab remains undisturbed, drilling being terminated as soon as the core starts to spin. A test rig consists of a framework (14) with platforms (15) to receive ballast. An upstanding frame (16) with cross beam (17) locates a hydraulic jack (18) which acts via probe (20) on the isolated concrete core. Upon extension of the jack, compaction of the sub-base immediately beneath the core is measured by a plate (19) reading off against a graduated scale (22). Alternatively transducers may measure force applied and compaction. The measurement of compaction is correlated with known properties of the concrete slab to determine the safe-loading characteristics of the floor in the test zone. The core may be removed and replaced by a steel probe for the compaction test. IMAGE
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