177630 Original to City Clerk • j ( r(i n
. • CITY OF ST. PAUL FIOE NCI. NO. AAA • ll \1
OFFICE OF THE CITY CLERK ( �
COUNCIL RE,OL T •N-GENERAL FORM
PRESENTED BY .a.+>
COMMISSIONS• DATF
RESOLVED, In accordance with the recommendation of the Commissioner and
Chief Engineer of the Department of Public Works that the proposal of the Twin
City Testing and Engineering Laboratory, Inc., dated April 19, 1956, as sub-
mitted to George N. Shepard in his capacity as Chief Engineer of the City of
St. Paul, for the furnishing of the necessary personal, professional and
toohnical services and the employment of the requisite equipment, all to be
furnished by the Twia City Testing and Engineering Laboratory in accordance
with the unit costs set forth in said proposal for the taking of cores in
concrete pavement, curbing and sidewalks, and for the inspection and testing
of such concrete cores and the source of materials used in the mixing and placing
of such concrete, at locations designated by the Chief Engineer, and providing
for the compilation and submission of a report on the test results, such report
including an evaluation of factors involved in the wearing and service qualities
of concrete pavement, curb and sidewalk in certain locations together with
recommendations for future construction of such concrete work and ether pertinent
matters related thereto, hereby is accepted and approved; and the proper city
officers hereby are authorised and directed, in behalf of the City, to execute
and deliver a contract by and between the City of St. Paul and the said Twin City
Testing and Engineering Laboratory, Inc. in accordance with said proposal, the
term whereof shall not exceed a period of sixty days after the date of the counter-
signature of this contract, and the aggregate liability of the City thereunder
shall not exceed the sum of $4500.00, said amount to be charged to Engineers Fund,
Cede 10B-3-135.
t/ APR 2 6 1956
COUNCILMEN Adopted by the Council 195_
P Y
Yeas Nays
APP 269956
Approved 195_
(Ala •
er
arzitelli• In Favor
-4,15 son• (� Mayor
Peterson• v Against PUBLISHED
President, Dillon•
5M 6-55 2
Duplicate to Printer !r
CITY OF ST. PAUL COUNCIL
NCIL NO.
OFFICE OF THE CITY CLERK
COUNCIL RESOLUTION—GENERAL FORM
PRESENTED BY April 26, 1956
COMMISSIONER DATE
RESOLVED, In accordance with the recommendation of the Commissioner and
Chief Engineer of the Department of Public Works that the proposal of the Twin
City Testing and Engineering Laboratory, Inc., dated April 19, 19560 as sub-
mitted to George M. Shepard in his capacity as Chief Engineer of the City of
St. Paul, for the furnishing of the necessary personal, professional and
technical services and the employment of the requisite equipment, all to be
furnished by the Twin City Testieg and Engineering Laboratory in accordance
with the unit costs set forth in said proposal for the taking of cores in
concrete pavement, curbing and sidewalks, and for the inspection and testing
of such concrete cores and the source of materials used in the mixing and placing
of such concrete, at locations designated by the Chief Engineer, and providing
for the compilation and submission of a report on the test results, such report
including an evaluation of factors involved in the wearing and service qualities
of concrete pavement, curb and sidewalk in certain locations together with
recommendations for future construction of such concrete work and other pertinent
matters related thereto, hereby is accepted and approved; and the proper city
officers hereby are authorised and directed, in behalf of the City, to execute
and deliver a contract by and between the City of St. Paul and the said Twin City
Testing and Engineering Laboratory, Inc. in accordance with said proposal, the
term whereof shall not exceed a period of sixty days after the date of the counter-
signature of this contract, and the aggregate liability of the City thereunder
shall not exceed the •sum of $4500.00, said amount to be charged to Engineers Fund,
Code 108-3-135.
APR 2 61956
COUNCILMEN Adopted by the Council 195_
Yeas Nays
G4 s, l �^ 6 ra t..,,
Hatrargtfl -. Approved r '? 195_
Holland
Marzitelli In Favor
Mortinson Mayor
Peterson Against
Mr. President, Dillon
5M 6-55 " ,-^2
M .at 5-6446
TLJJIfl CITY TESTIflO flflD EflOiflEEftiflO L Inc.
CHEMICAL & PHYSICAL TESTS • INSPECTIONS • RESEARCH
OFFICERS
CHARLES W.BRITZIUS,P.E.-President 2440 F R A N K L I N AVENUE
JOHN F.GISLASON,P.E.—Executive Vice-President F,NDEVE
CLINTON R. EUE—Secretary-Treasurer �'O�-�'��'"'`
��� =���� St Pal 14, Minn.
ASSOCIATES o 763
o /
NORMAN E.HENNING,P.E.-Engineering � �o� ��
b\ 3
ALBERT C.HOLLER,F.A.I.C.-Chemistry �.�
HAROLD E.CARTIER,P.E.-Applied Engineering April 19, 1956
ROBERT F.WITTMAN-Foundation Soils
Mr. George M. Shepard, City Engineer
City of St. Paul
City Hall & Courthouse
St. Paul, Minnesota
Dear Sir:
In a recent discussion in your office, you requested that we
furnish you a quotation for our services to investigate the disintegration
and surface scaling of concrete curbs, sidewalks, and paving placed in St.
Paul during the past several years.
The main factors which would effect the durability of the concrete
would be as follows:
1. The general quality of the concrete
This would be dependent on the cement content and the water-cement
ratio of the concrete. It would also be dependent on the quality
and the gradations of the fine and coarse aggregate. The quality
of the aggregates in the St. Paul area is very good, much better
than in most municipalities in Minnesota. The glacial gravels
utilized in the St. Paul area are primarily from the Patrician
Drift and are free from the high amount of shale that characterize
the aggregates in western Minneapolis which are processed from the
Keewatin Drift. The gradation of the aggregates would, of course,
depend on the producer and might vary throughout the times of the
production. The quality of the concrete can be fairly well eval-
uated by the removal of cores with a rotary diamond bit and de-
termining the compressive strength of the concrete. Your City
Building Code requires a 6.0 sack per yard mix for sidewalk and
curbing and this should give strengths of around 4000 pounds per
square inch.
2. The entrained air content in the concrete
Research and service records from a wide variety of sources during
the past 1t. years has demonstrated that the purposeful entrainment
of proper quantities of air in concrete improves the resistance of
the hardened concrete to frost action by several hundred percent.
AS A MUTUAL PROTECTION TO CLIENTS, THE PUBLIC AND OURSELVES, ALL REPORTS ARE SUBMITTED AS THE CONFIDENTIAL PROPERTY OF CLIENTS, AND AUTHOR-
IZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL
Mr. George M. Shepard, City Engineer April 19, 1956
- '2
It is possible to microscopically determine the amount of entrained air
in hardened concrete and also to evaluate from the pore spaces per inch
whether or not the size and spacing of the air bubbles is effective.
3. The finishing and manipulation of the plastic concrete
When plastic concrete is placed into a form, the attraction of gravity
draws the aggregate particles downward. This subsidence replaces, the
water in the concrete and this water appears at the surface of the con-
crete. The length of time this water will remain at the surface is
dependent upon the temperature of the concrete and the outside air, the
wind velocity, and the setting time of the cement. Any manipulation of
the concrete surface during this bleeding period will inter mix the
cement paste with this bleeding water and give a layer of concrete at
the surface which has a very high water-cement ratio and a very low
strength. Very few cycles of freezing and thawing will cause this layer
to peel off. There is no test on the hardened concrete to determine
whether or not this has happened, but a visual examination of the type
of scaling as well as evaulating the other test results, one can usually
reach an opinion as to when this condition is the cause of the scaling.
!s. Adequate curing and adequate curing temperatures for the concrete
The chemical reaction of Portland cement requires the presence of water.
There is sufficient water in concrete to supply this need; however the
evaporation of water from a flat surface is very rapid, depending upon
the weather conditions and the wind velocity. It is therefore necessary
that precautions be taken to insure that this water does not evaporate.
The best method is by the application of a curing paper, although the
sufficient application of a good membrane curing compound is beneficial.
The chemical reaction of Portland cement is also practically dormant
below 45° F., thus concrete that is placed late in the fall does not
have sufficiently high temperatures to develop any strength and goes
into our severe winter season very susceptible to freezing and thawing
and salt action. Here again, tests can be made to determine the extent
of proper curing, but evaluation would have to be made on the basis of
the inspector's information as to date of pour and type of curing. The
information on the weather is obtainable from the local weather office.
The unit costs for eome of the tests you suggested would be as follows:
1. Removal of 4 cores from each location $ 25.00
2. Determine compressive strength of concrete
per core 5000
3, Microscopic determination of air content,
per core 17.50
. Freezing and thawing test, per core
per cycle 1..50
Mr. George M. Shepard, City Engineer April 19, 1956
- 3 -
•
5. Engineering report on test'results, evaluation, and
recommendations $ 150.00
It can be seen that to remove four cores in one location, two removed in
satisfactory concrete and two removed in scaled concrete, determine the com-
pressive strength on two of the cores and determine the air-content on two of
the cores would cost $ 80.00.
Very truly yours,
TWIN CITY TESTING AND
ENGINEERING LABORATORY, INC.
NEHtas Norman E. Henning