Rebound Hammer Test Worksheet (Page 2 of 4) in pdf

Rebound Hammer Test Worksheet Page 2

SD 409

Page 2

(2)

Perform the test hammer procedure on the cylinder as per 3.3B

through 3.3H.

(3)

Perform the compressive strength test on the cylinder

according to SD 420 and record the cylinder compressive

strength (A).

(4)

Compare the compressive strength of the cylinder (A) to the

orientation corrected compressive strength (F) determined by

the test hammer in 3.2B(2). Calculate the field correction factor

(G) = (A) / (F).

(5)

When possible, apply this correction factor to field tests of the

same concrete according to 3.3I.

3.3

Field tests.

Operate the test hammer in a horizontal position, whenever feasible.

If the concrete surface is rough, grind points to be tested with the

carborundum stone.

Press the test hammer plunger at exactly right angles to the surface of

the concrete being tested. Press the plunger slowly and uniformly until

released. Do not jerk or try to anticipate the plunger release.

After impact, press the lock button and read the rebound value shown

on the rider. Record the reading.

Take a minimum of 15 rebound readings. Take only one reading at a

given point. Very high readings may be caused by rock or steel near

the surface at the point of impact, and very low readings may be

caused by trapped air pockets near the surface at the point of impact.

Discard the highest reading, the lowest reading, and any that are

obviously in error. Calculate the sum of the remaining readings (B) and

the average of the remaining readings (C).

Convert the average of remaining reading (C) to compressive strength

(D) in PSI (kPa) by using the Central Lab calibration chart for that

particular test hammer. (Do not use the calibration curves on the test

hammer.)

mso.mat 9-14

Rebound Hammer Test Worksheet Page 2