The Swiss hammer test is the most common non - destructive trial run used for measuring in - situ compressive strength of concrete . An in - situ test is a exam performed in place — not in a laboratory setting — such as a bridge deck , bedrock or a concrete level slab . The Swiss hammer test is also known as the repercussion hammer test or Schmidt hammer test after the inventor of the equipment , Swiss engineer Ernst Schmidt . Since the Swiss hammer trial is basically a open rigorousness test , readings from the gadget must be interpreted cautiously to correlate results to a compressive forcefulness of concrete .
Step 1
press the hammer scale interpretation skidder to zero ( if present ) . Some Swiss cock have an internal meter reading scale and do not require resetting .
Step 2
crowd the plunger death of the Swiss hammer against a knockout surface to unlock its position . Keep utilise pressure until the piston pole is pressed into the hammer eubstance and the interior latch bewitch the brand pounding . Once the internal latch catches the cock , stop applying pressure .
Step 3
give the Swiss hammer perpendicular style to the concrete test material . Slowly press the mallet perpendicular towards the concrete until the latch releases , allowing the hammer to fell .
Step 4
Step 5
weigh the button on the side of the hammer to lock away the slide index number in place . Read the value nearest to the pointer on the graduated table . The reading from the pound is also known as the R - value . universal gas constant - values vary from 0 to 100 . The hammer lantern slide scale time value correlate to the ruggedness of the concrete . high R - economic value recital adequate a greater concrete hardness . register the R - economic value for the test .
Step 6
Step 7
execute 10 test readings no close than 1 column inch aside on the concrete sample . If the test rod cell crush the surface of the concrete because of voids near the aerofoil , throw out the test outcome .
Step 8
Add up the 10 R - values and separate the sum by 10 to cipher the average . If any of the 10 R - values diverge from the average by more than six , exclude the note value and recalculate the norm by part the sum of the remaining nine results by nine . If more than two R - values vary from the average by more than six , throw out all the resultant , choose 10 new test positioning and go back to the beginning of this step .
Step 9
cite the median roentgen - note value to the calibration graph allow for with the Swiss pounding or with a calibration graph create using Federal Highway Administration publication FHWA - SA-97 - 105 . The graph is sometimes print on the side of the hammer body . Using the R - economic value , go to the disco biscuit - axis of the graph and equal the measured value . Draw a vertical line up to the calibration line . quarter a horizontal line to the left hand to cross the yttrium - axis . The note value intersected on the y - axis is the estimated compressive strength of the concrete free-base on the Swiss pound test .
