Safety Info 
Safety!
 Safety glasses are required at all times while equipment is turned on. Not
only are safety glasses a good precaution, they prepare students for industry where they
are also required.
 Use containment cages around cylinders to prevent flying pieces upon failure
 Long hair must be tied back so it doesn’t get caught in moving equipment.
Avoid wearing jewelry that may also become tangled in equipment.
 The Schmidt hammer uses a large amount of force to test the hardness of a material. Do
not put the Schmidt hammer up to your head!


Equipment
Used


Procedures:
All data sheets [ xls ]


Capping Cylinders
 Remove the cylinders from the wet room.
 Place one neoprene cap on the top of the cylinder.
 Invert the cylinder and repeat the procedure for the other end.


Schmidt Hammering
a Cylinder
The nondestructive Schmidt Hammer test will be
performed on one cylinder for comparison.
 Place the cylinder in the compression machine.
 Apply a 2000 lb. holding load.
 Choose 12 relatively smooth locations at least one inch apart and evenly distributed
around the side of the cylinder.
 With the plunger of the Schmidt hammer extended, slowly press the hammer against the
side of the cylinder until the hammer is released and impacts against the cylinder. At
the moment of impact, the hammer must be held perpendicular to the surface.
 Press the locking button on the side of the hammer to hold the reading. DO NOT
PUSH THE LOCKING BUTTON BEFORE THE HAMMER HITS THE CYLINDER.
 Record the rebound number.
 After taking all 12 readings, compute a preliminary average rebound number.
 Disregard any tests with a rebound number that deviates from the preliminary mean by
more than +/ 5 and compute the final mean rebound number.
 Use the correlation table provided to obtain the compressive strength from the final
mean rebound number. Note the angle on the chart.


Testing
a cylinder with strain readings
Measure strain on one cylinder
 Measure the diameter.
 Attach the strainometer to one cylinder.
 Measure the gage length with dial calipers.
 Record the deformation from the strainometer at 5000 pound load increments. The deformation measured by the
dial gage is twice the deformation between the points where the apparatus is attached to
the cylinder. Thus, divide the dial gage reading by two to obtain the deformation between
the attachment points.


Testing
a cylinder without strain readings
 Measure the diameter.
 Use a loading rate of 30 psi/second.
 Test to failure and record the failure load.


Calculations
 For all cylinders record the failure load, age of
cylinder, and any unusual circumstances.
 For all cylinders compute the compressive strength using
f'c =
load/area.
 Compute the Schmidt Hammer results.
 Plot a stressstrain curve for the cylinder that was tested with the strainometer.
Include it in the results section of your report.
 Determine the secant modulus of elasticity from the stressstrain curve. The secant
modulus of elasticity (E) is given by:
E = (s _{2}  s
_{1})/(e _{2}
– 0.000050)Where:
E = secant modulus of elasticity in psi
s _{2} = stress at 40% of
ultimate load
s _{1} = stress at strain of
0.000050
e _{2} = strain at 40% of
ultimate load
