ST0501-CS121009 (2) OCT-10-2012 05:59 P.01
Texas CMT, Inc.
Construction Materials Testing GEE Consultants, Inc.
and Environmental Consulting
10044 Monroe Drive • Dallas, Texas 75229 • (214) 352-6957 • Fax (214) 352-6972 • www .texascmt.com
Post its Fax Note 7671 Date pages*
October 9, 2012 To ciciFizYy/Dg1/ p From � '
CoiDept.�:/V G 4 T/`I S�1v,�Co./=6e c---r1SCAtTrw�'�
Phone# F}723O4-3 c%rhonee#21�
Mr. Robert Caudill Fax# 2'304_35-70 Fax#z 2 6C1
Tiseo Paving
Engineering Department
P.O. Box 270040
Dallas. Texas 75227
Via: rcaudill @tiseopaving.com
RE: Project No. 211-0125
Deforest Road Reconstruction
Allen Road Cores
ST-05-01
Coppell, Texas
Dear Mr. Caudill
Per your September 20, 2012 request as well as that of Mr. Walter Mitchell of September 25,
2012, a representative of Texas CMT, Inc. obtained and tested four (4) cores from a section of
Allen Road,just south of Deforest Road. The purpose was to determine the concrete compressive
strength of Allen Road south bound pavement cast on August 2, 2012. The compressive strength
of this concrete pavement section came into question as a result of the 28-day cylinder strength
results reported in our Concrete Report No. 52, a copy of which is enclosed.
On review of the Concrete Mix Observation Report No. 52 you will note that the average 28-day
cylinder compressive strength was 2,570 psi. This 28-day strength is more than 500 psi below the
required strength of 3,600 psi. The average 28-day cylinder strength was 71 percent of the required
3,600 psi strength. It is our understanding that since the concrete in question was hand formed,
technically the required compressive strength is supposed to be 4,000 psi. The slump test result
for the concrete in question was 6 inches which exceeded the maximum of 5 inches specified by
OCT-10-2012 05:59 P.02
City of Coppell
Deforest Road Reconstruction October 9,2012
NCT COG for hand formed pavement. The ambient air temperature at the time was 95 degrees
Fahrenheit. The concrete sample's air content was 6.0 percent.
A summary of core compressive strength test results is as follows:
Specimen Average Cross- L/D Ratio and Max. Compressive Compressive Percentage of
No. Core Sectional Correction Load Strength Strength(with 3,600 psi
Diameter Area Factor (Ibs) (Before L/D Required
(in.) (sq.in.) Correction) Correction Compressive
(psi) Applied) Strength
(psi)
C-1 3.70 10.75 1.00 0.998 32,240 2,999.1 2,990 83
C-2 3.70 10.75 1.00 0.999 32,980 3,067.9 3,060 85
C-3 3.70 10.87 1.00 1.000 37,180 3,420.4 3,420 95
C-4 3.70 10.87 1.00 1.000 31,460 2,894.2 2,890 80
The average compressive strength of the four (4) cores was 3,090 psi, which was 85.8 percent of
the required 3,600 psi. The four (4) cores were tested at either 53 or 63 days of age. The average
core strength of 3,090 psi compares relatively well to the reported 56-day cylinder strength of
3,160 psi (see Concrete Report No. 52).
The North Central Texas Council of Governments (NCT COG) Public Works Construction
Standards requires the average strength of pavement cores meet 100 % of the minimum specified
strength, with no individual core resulting in less than 90 % of design strength, to override the
results of cylinder tests. The average of the core strength results is less than 100 % and 3 of the
4 cores are less than 90 % of the specified strength. Per NCT COG concrete pavement not
meeting requirements shall be subject to money penalties per Table 303.8.3.1.(a) or removal and
replacement.
The sample location indicated in Concrete Report No. 52 was 0 to 10 feet S. of 729 Allen Rd.
Walkway. This location encompasses two (2) panels of south bound pavement west of the Allen
Road centerline. Visual observations of these two (2) panels exhibited similar spalling at the
longitudinal centerline pavement joint. It is our understanding that the south panel cracked within
about a week of concrete construction completion.
Based on our observations of similar joint spalling and the crack in one (1) of the two (2)
pavement panels in question, as well as 28-day cylinder strength 29 percent less than 3,600 psi
(about 36 percent below a requirement of 4,000 psi) we recommend these two (2) panels be
removed and replaced.
Although the 28-day strength test results in Concrete Report No. 52 did not meet requirements
Texas CMT,Inc. Project No.211-0125
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OCT-10-2012 05:59 P.03
City of Coppell
Deforest Road Reconstruction October 9,2012
this does not mean that all concrete cast on this date should be removed, and we do not
recommend such. Concrete mixes that are properly designed and randomly sampled have a I in
100 chance of not meeting strength requirements. To date the concrete results included in our
Report No. 52 are the only low results of the 78 samples thus far tested. Following this logic the
next ready mix truck delivered to the site (after the Allen Road southbound concrete in question)
would have only a one (1) percent chance of the concrete strength being low.
Our recommendations are based on the assumption that an adequately designed and constructed
Portland cement concrete wearing surface is utilized. Drainage should be maintained away from
pavement sections both during and after construction. Ponding of water should not be allowed at
any location. The quality of all phases of the construction of the proposed replacement pavement
should be checked by qualified personnel to ensure that the work is done in the field in
accordance with the accepted plans and specifications.
If you have any questions or if you require further information, please do not hesitate to contact
us.
Sincerely,
Texas CMT, Inc.
TBPE Firm No. F-4521
Md4 ' .11 an, • . . I-7;1317-- Richard W. Gee, 1':E. '°°:"7
Project Engineer President
Construction Materials Engineering Division ;;h c\RJ ,' NE GEE
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cc: Mr. Larry Davis - City of Coppell, Phone: 972-304-3684; via Fax: 972-304-3570 ;.
Mr. George Marshall - City of Coppell, Phone: 972-304-3562; via E-mail: gMarshall @coppelltx.gov
Mr. Dan DeGroot-Burgess&Niple, Inc., Phone: 972-620-1255; via E-mail: Dan.DeGroot @BurgessNiple.com
Mr. Robert Caudill -Tiseo Paving Company, Phone: 972-289-0723; via E-mail: rCaudill@TiseoPaving.com
Mr. Walter Mitchell - Tiseo Paving Company, via E-mail: barnobas @yahoo.com
Texas CMT,Inc. Project No.211-0125
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