PROJ00077

• Contract/PO #: FS0008X
• Contractor Name: Longmont, City of
• Contract Type: Loan
• Water District: 0
• County: Boulder
• Loan Projects - Doc Type: Feasibility Study

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

The average measured unconfined compressive strength for two six-inch
diameter cores and 14 NX cores was 5,350 psi with a range of 2,080 to 7,760 psi.
This represents high strength concrete. Since six inch diameter core is the
standard test diameter, a correction factor of .93 (Blanks and McNamara, 1935)
should be applied to NX core to relate its strength to six-inch core. This
results in a corrected average unconfined compressive strength of 4,990 psi.
The average density of 16 samples was 143 pcf with an average moisture
content (after soaking 24 hours) of 3.9%.
Five indirect tensile strength tests (Brazilian Test) were made on NX
core. Tensile strengths ranged from 265 psi to 1,086 psi with an average of 693
psi.

Seven samples (two 6"-diameter and five 2"-diameter) were tested for
modulus of elasticity. Values ranged from 2.4 million psi to 5.2 million psi
with an average of 3.7 million psi.
Chemical Properties
Four core samples were submitted to Martin-Marietta laboratories in
Baltimore, Maryland for chemical analysis. Samples were selected from different
depths to attempt to obtain at least one sample from each construction season.
The samples were tested for chemical content to ascertain cement type and addi-
tives. Test results were not available at the time of this writing.
Pulse Velocities
Pulse velocities were measured in the field using a Tektronix 314 storage
oscilloscope in conjunction with a transducer and an accelerometer. A modified
Schmidt Rebound Hammer was used for a pulse source. A refraction array was used
such that the source, transducer, and accelerometer were placed in a line on the
same dam face at respective distances of two and ten feet. Thus, measured pulse
velocities values were made below the near-surface deteriorated zone.

-12-