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PERFORMANCE OF HIGH-STRENGTH CONCRETE INCORPORATING MINERAL BY-PRODUCTS* By Tarun R. Naik Director, Center for By-Products Utilization
Viral M. Patel Research Associate, Center for By-Products Utilization and Larry E. Brand Former Graduate Student Department of Civil Engineering and Mechanics
College of Engineering and Applied Science The University of Wisconsin-Milwaukee P.O. Box 784 Milwaukee, WI 53201 Telephone: (414) 229-6696 Fax: (414) 229-6958
___________________________________________________________ * Paper submitted for presentation and publication for the Research in Progress Seminar at the ACI, National Convention, Washington, D.C., March 15-19, 1992.
PERFORMANCE OF HIGH-STRENGTH CONCRETE
INCORPORATING MINERAL BY-PRODUCTS
Tarun R. Naik*, Viral M. Patel** and Larry E. Brand***
ABSTRACT
This research was undertaken to investigate performance of
high-strength concrete incorporating mineral admixtures, fly ash and
silica fume. For modern construction, the use of new construction
materials is increasing to achieve economy and improved final results.
An extensive literature search was carried out to review various
engineering properties of high-strength concrete.
In this study, three different mix proportions for high-strength
concretes were developed. One mix was proportioned with fly ash
consisting of one third of total cementitious materials, and was
designed to achieve 10,000 psi (70 MPa) compressive strength at 28
days. The other two mixes included both fly ash and silica fume to
obtain 11,000 psi (77 MPa) and 12,000 psi (85 MPa) compressive strength
at 28 days. All mixes were produced at a ready mixed concrete plant.
Various tests, to determine physical properties of as delivered
*Director, Center for By-Products Utilization, College of
Engineering and Applied Science, University of Wisconsin-Milwaukee, Milwaukee, WI.
**Research Associate, Center for By-Products Utilization.
***Former Graduate Student.
3
concrete, such as slump, density, air-content, etc. were carried out.
Twenty-seven 6 x 12 in. (150 mm x 300 mm) cylinders were cast for
each mix for measuring modulus of elasticity and compressive strength
of concrete at various ages. Additional twenty-seven 6 x 12 in. (150
mm x 300 mm) cylinders were also cast for measuring splitting tensile
strength for each mix at various ages. Furthermore, forty-six 4 x
8 in. (100 mm x 200 mm) cylinders were cast and tested for compressive
strength for each mix for various ages up to one year. Testing work
is still in progress to obtain long-term strength properties.
Standard 6 x 12 in. (150 mm x 300 mm) cylinder tests data are compared
with 4 x 8 in. (100 mm x 200 mm) cylinders; and all cylinder test
results are also compared with 4 x 8 in. (100 mm x 200 mm) cores obtained
from companion concrete structural members. All tests were conducted
in accordance with appropriate ASTM standards. Core test specimens
obtained from beams made with the three mixes were also tested for
chloride permeability using the AASHTO T-227 test method. Test
results revealed that high-strength concrete can be made using high
volumes of Class C fly ash to obtain strength levels in the range
of 14,000 psi (100 MPa) at 1 year age and beyond. Reinforcement
corrosion potential data are also planned for up to five years of
this study. All of the available data is analyzed and graphs are
plotted to derive useful conclusions and recommendations for testing
and use of high-strength concrete with and without fly ash and silica
fume.
4
INTRODUCTION
Engineers are continuously faced with increasing demands for
improved efficiency and reduced construction costs from private and
public sectors. As a result, the use of high-strength concrete to
accommodate higher stress levels is increasing. Until recently
concrete with a strength in excess of 6000 psi (42 MPa) at 28 days
was rarely available from a ready mixed concrete producer. However,
in recent years high-strength concrete has gradually evolved; and,
it is being put to a wider use. This has been made possible due to
developments in concrete making materials and cost effective
utilization of high-strength concretes.
DEFINITION OF HIGH-STRENGTH CONCRETE
High-strength concrete, as defined by the ACI, is a normal weight
concrete which has an uniaxial compressive strength of 6000 psi (42
MPa) or greater at 28 days (1). However, concrete with a compressive
strength higher than that which is ordinarily available in a region
could also be regarded as high-strength concrete. More recently,
some people define concrete with a compressive strength of 8000 psi
(56 MPa) and above as high-strength concrete. Even though 6000 psi
(42 MPa) was selected as the lower limit by the ACI 318-89 Building
Code, it is not intended to imply that there is a drastic change in
material properties, its behavior, or production techniques, that
5
occur at this level of compressive strength. In reality, all changes
that take place above 6000 psi (42 MPa) represent a gradual process
which starts with the "normal-strength" concretes and continues into
high-strength concretes.
SCOPE
There are distinct advantages in using concrete with higher
compressive strengths in both reinforced, prestressed, and precast
concrete construction. Despite extensive research carried out over
the years and availability of low-cost production techniques of
high-strength concrete, the full utilization of this engineering
material has not been realized. This has been particularly so in
prestressed and precast concrete construction applications in which
there would be some distinct advantages with the use of high-strength
concrete. A possible reason why full utilization has not occurred
is that the practicality of everyday use of high-strength concrete,
particularly greater than 10,000 psi (70 MPa), has not yet been fully
determined, with or without the use of high-strength reinforcing
steel. Also, adequate changes in various building code
specifications, such as ACI 318-89 Building Code, to provide for better
performance of structures using high-strength concretes has not yet
been accomplished. Therefore, requirements for code equations and
structural design considerations must also be evaluated to determine
their applicability with higher strength concretes in the concrete
6
industry (2). For example, equations for allowable tensile strength,
shear strength, and modulus of elasticity for a given value of
compressive strength must be developed for high-strength concrete.
This research answers some of these concerns.
This paper reviews and presents results from a research project
carried out at the Center for By-Products Utilization at the
UW-Milwaukee to determine the properties of fresh and hardened
high-strength concrete. The project included 10,000, 11,000, and
12,000 psi (70, 77 and 84 MPa) concrete mixes. Tests completed on
each mix were, axial compressive strength of cast cylinders, modulus
of elasticity, and splitting tensile strength. Cores were taken from
beams cast with the same mixes and were tested for compressive strength
to be compared with the cylinder test results. All results were
compared with the available ACI 318-89 Code equations for calculating
these properties based upon the concrete compressive strength. These
three concretes were also tested to determine the rapid chloride ion
permeability at one year age.
CONCRETE MIX PROPORTIONING
This section details mix proportions tested in this project.
The research project consisted of three different mix proportions
to achieve nominal strengths of 10,000 psi (70 MPa) and higher at
the 28-day age. The production concrete was proportioned in
7
consultation with a silica fume supplier and a ready-mixed concrete
company located in Milwaukee, Wisconsin. Production of high-strength
concrete using conventional batching equipment and techniques
requires better quality of materials (i.e., low coefficient of
variation) and accuracy in the batching of the mix, particularly in
measuring moisture level in the fine aggregates. The materials used
in the mixes were locally available. Previous research has shown
that the selection of raw materials is extremely important for
high-strength concrete (3, 4, 5). The type and brand of cement also
influences the workability and the strength of concrete (6,7,8).
Type I Portland cement from a regional supplier, for which prior test
data were available (3,4,5), was used in all mixes.
Properties and type of both coarse aggregates and fine aggregates
used in the production of concrete are also important. The fine and
coarse aggregate used in the project met the requirements of ASTM
C-33. Washed natural sand and coarse aggregate at SSD condition were
used for all mixes. The maximum 1/2" size coarse aggregate was crushed
limestone with a compressive strength of 35,000 psi.
The water/cementitious ratios used in the past studies for the
production of high-strength concretes have been lower than 0.35 (3,
4, 5, 9). In this study, the w/c ratio included fly ash and/or silica
fume with the cement to provide a water/cementitious ratio of less
than 0.30.
8
One-third of the total cementitious materials was a Type C fly
ash (with CaO of about 26%) for the 10,000 psi (70 MPa) mix. The other
two mixes had both the Type C fly ash and a silica fume included as
a partial replacement of cement in the concrete. The Class C fly
ash from the Pleasant Prairie Power Plant in Wisconsin was used in
this study. Since silica fume is very fine, it was added in slurry
form, i.e. initially mixed with water. This excess water was
accounted for in calculating the water/cementitious ratio.
The concrete tested was not air entrained because the structural
elements were for indoor use. Various other admixtures, a retarder
and a superplasticizer, were also added to the concrete to lower the
water/cementitious ratio and to achieve a high workability of 6" (150
mm) slump or higher. Details of all the mixes are given in Table
1.
CASTING AND CURING OF TEST SPECIMENS
A number of tests were conducted on fresh and hardened concrete.
The temperature of the concrete and the ambient air was measured
at the time of casting of test specimens. The slump, density, and
air content of all the three concretes were also measured in accordance
with applicable ASTM standards. These values are presented in the
Table 1. Mechanical and elastic properties of hardened concrete were
9
determined, Tables 2-6. There were two different diameters of
cylinders tested for comparison, Fig. 1. Twenty seven 6 x 12 in.
(150 mm x 300 mm) cylinders were cast in reusable cast-iron molds
for measuring the compressive strength and the modulus of elasticity.
Another twenty eight 6 x 12 in. (150 mm x 300 mm) cylinders were
cast in plastic molds for measuring the splitting tensile strength
of concrete. Also, forty-six 4 x 8 in. (100 mm x 200 mm) cylinders
were cast in cast iron molds for compressive strengths of concrete
at various later test ages. All specimens were prepared in accordance
with ASTM and then sprayed with a curing compound ("confilm") to the
exposed surface which minimizes evaporation of the mix water from
the concrete surface. The cylinders were then covered with plastic
bags and immediately placed in a lime-saturated water tank at a
temperature of 73 F ± 3 F (27 C ± 1.5 C). All specimens were stripped
after 24 hours and stored in the lime-saturated water tank until the
time of test. One cylinder of each size and from each mix was used
for measuring the maturity of the concrete in order to compare it
with the maturity of in-situ concrete in structural beam elements.
The temperature probes were inserted into the cylinders and beams
soon after the top surface was finished.
10
PROPERTIES OF HARDENED CONCRETE
Compressive Strength
Two sizes of cylindrical specimens were tested in accordance
with ASTM C-39 to determine the compressive strength of concrete.
Three 4 x 8 in. (100 mm x 200 mm) cylinders were tested at each of
the following test ages: 1, 3, 7, 14, 28, 56, 91, 182, and 365 days,
to determine the compressive strength of the three concrete mixes.
Three 6 x 12-in cylinders were tested at each test age for compressive
strength up to 28-day age. Compressive strength tests are scheduled
for 2,3,4 and 5 years. All the tests were done using a Tinius-Olsen
compressive testing machine meeting C-911 ASTM requirements. The
test results are presented in Tables 2, 3 and 4. The strength of
these mixes plotted against their test ages is shown in Fig. 2, 3
and 4.
As seen from the Fig. 2, 3 and 4, the desired compressive strengths
were achieved between 28 and 35 days. It was possible to obtain such
high strengths by using a high cementitious content, addition of finer
additives like fly ash and silica fume and a lower w/c ratio in
combination with a superplasticizer. This resulted in a denser matrix
and better bond between the aggregate and the mortar matrix surrounding
it. Also the higher compressive strength of the aggregates
contributed to the higher compressive strength of these concretes.
11
The compressive strength of low cementitious factor, low-strength,
concrete may not significantly increase after 91 days while the
compressive strength of high cementitious factor, high-strength,
concrete keeps increasing significantly up to approximately 180 days
and then it starts leveling off. This is because of high-cementitious
content which continues to hydrate over a longer period of time.
Tensile Strength
The 6 x 12 in. (150 mm x 300 mm) cylinders were tested to determine
the splitting tensile strength of concrete. Splitting tensile
strength tests were conducted in accordance with the ASTM C-496, at
1, 3, 7, 14, 28 and 56 days. Three cylinders were tested at each
test age. All cylinders were tested wet. Detailed test data are
given in Tables 2, 3, and 4. Fig. 5, 6 and 7 show variation of the
tensile strength with age of concrete. As can be expected, the tensile
strength increased with increasing age. Fig. 8 compares the test
results with the ACI 318-89 Eqn. 11.2.1.1 based upon the compressive
strength: fct= 6.7 (f'c)1/2, where fct is the predicted splitting
tensile strength from the compressive strength, f'c.
Fig. 8 shows that the ACI Eqn. 11.2.1.1 underpredicts the tensile
strength of the 10,000 psi (70 MPa) and higher strength concrete.
This is believed to be due to a denser matrix, as well as improved
aggregate mortar bond resulting in better tensile strength for
12
concrete containing fly ash with or without silica fume. The tested
specimens showed that more than 95% of the aggregates failed in tension
indicating excellent aggregate mortar interface bond. Very few
aggregate bond failures were observed after 14-day age of concrete.
After 28 days of curing, the increase in tensile strength was at
a diminishing rate for all mixes. A new equation needs to be developed
to reliably estimate the tensile strength of the high strength
concrete.
It can be observed from Fig. 8 the ACI Eq. overpredicts the tensile
strength of concrete at strength lower than 6000 psi (42 MPa). The
measured splitting tensile strengths were about 10-12% of the
compressive strength up to about 6,000 psi (42 MPa) compressive
strength. On the other hand, the tensile strength, measured as a
percentage of the compressive strength, reduced to about 6% for higher
compressive strengths. Similar results have been reported earlier
(10).
Modulus of Elasticity
The standard cylinders cast in cast-iron molds were tested to
determine the static modulus of elasticity and compressive strength
of concrete. All the tests for the modulus of elasticity were carried
out in accordance with the ASTM C-469. These tests were conducted
at 1, 3, 7, 14, 28, 35, and 56 days. Three cylinders were tested
13
at each test age. For all mixes, at 1 and 3 day ages, the cylinders
were capped using a regular-strength sulfur capping compound. While
for all other tests, a high strength sulfur capping compound was used.
This capping compound was recommended by the manufacturer for
concrete with compressive strengths of 6000 psi to 16000 psi (40 to
115 MPa). Test specimens were air dried on the top and bottom surfaces
for capping. They were then capped and tested wet, after reimmersing
them for sufficient amount of time in the water tank. The strains
in the concrete were measured up to approximately 70% of the
compressive strength at that test age. The secant modulus of
elasticity was then calculated by measuring the slope of the line
joining the points with stress corresponding to 0.40 fc' and stress
at 50 millionths strain, per ASTM C-469. This value was then rounded
off to the nearest 50,000 psi. The test results are reported in
Table 5. The modulus increased, as expected, with increasing age
at a decreasing rate after 14-day age. The modulus of elasticity
determined for each stress-strain curve at each strength is plotted
against the compressive strength at each age and compared with the
ACI 318-89 Eqn. 8.5.1, Fig. 9.
Ec = 33 w1.5 (f'c)½
It is clear from the Figure 9 that the ACI equation overpredicts
the modulus of elasticity after about 5,000 psi (35 MPa) compressive
strength of concrete. Hence the prediction of the deflection of
14
structural members would be lower than actual, thereby predicting
reduced ductility for high-strength concrete members. It is apparent
that the modulus of elasticity of high-strength is lower than predicted
than that of normal strength (less than 5000 psi, 35 MPa) concrete.
This is due to the fact that there are fewer microcracks in the normal
strength concrete at a given strain thereby increasing its modulus
of elasticity. Also it is observed from Table 5 that the modulus
of elasticity increases at a decreasing rate after 14-day age.
COMPRESSIVE STRENGTH FROM CORE TESTS
Concrete cores of 4" (100 mm) nominal diameter were cored using
a diamond tipped drill bit from beams cast from these three concrete
mixes. Care was taken to avoid cutting the reinforcement. The
direction of coring was perpendicular to the direction of casting
of concrete beams. These cores were then conditioned and tested in
accordance with the ASTM Test C-42 and C-39. The length-to-diameter
(l/d) ratios for the cores were maintained at two. High-strength
sulfur capping compound was used to cap these cores. All cores were
tested in the same Tinus Olsen compression testing machine as the
cylindrical cast specimens. The details of the core specimens and
tests data are given in the Table 6. A core numbering system was
devised for ease of identification. The numbering consists of two
numbers: B-N., where "B" is the beam # cored, and "N" is the number
of core. Three cores were tested from each beam. A correction factor
15
was used to predict the equivalent cylinder compressive strength of
the beam concrete (12). The correction factor was chosen from the
Table 7 which is arrived at from the ACI 318-89 and Ref. 12. This
corrected strength test value was used to compute the nominal cylinder
compressive strength based upon the core compressive strength.
It can be observed from the tests that the core strengths are
lower than the cylinder strengths at an equivalent age, Tables 2,
3, 4, and 6. At higher design strengths, the core strengths were
much lower than the equivalent age cylinder strengths. Thus as the
concrete strengths increases, a higher correction is required to
express the core strength in terms of equivalent cylinder strength
(12).
RAPID CHLORIDE PERMEABILITY TESTING
All three series of concrete under investigation were tested
in accordance with AASHTO T 277 procedure to determine the chloride
ion permeability of concrete mixes. Values for chloride permeability
rating of concretes, as established by AASHTO (11), are listed below:
Permeability Rating Charge, Coulombs
Negligible Less than 100 Coulombs
Very Low 100 to 1,000 Coulombs
Low 1,000 to 2,000 Coulombs
16
Moderate 2,000 to 4,000 Coulombs
High Greater than 4,000 Coulombs
The rapid chloride permeability test data obtained for this
series of concrete under study is presented in Table 8. The Mix 1
tested to pass an average total charge of 259 Coulombs. The Mix 2
and 3 showed an average total charge of 263 Coulombs and 260 Coulombs,
respectively. Thus, according to AASHTO rating, all mixes had "very
low chloride ion permeability". The plot of test time versus the
total charge passed for Mix 1, 2 and 3 at the age of one year is shown
in Figure 10.
CONCLUSIONS
On the basis of the research reviewed and test results obtained,
use of high-strength concrete in the construction industry would
definitely be of a great advantage. However, before this is done
on a full scale, further research and modifications are required for
the building codes and specifications.
From this project it can be concluded that high-strength concrete
can be manufactured with a low water/cementitious ratio and use of
superplasticizer to achieve high workability. However,
finishability of the concrete was a problem due to loss of effect
of the superplasticizer.
17
18
The desired compressive strength for all mixes were achieved
at about 35 days of age. At later ages, the compressive strengths
of concretes with fly ash only and concretes with both fly ash and
silica fume were almost the same. The tensile strength increased
with increasing age. However, the tensile strength measured as a
percentage of the compressive strength for all mixes reduced to about
6% of the compressive strengths as compared to about 10-12% for
concretes below 6000 psi compressive strengths.
The modulus of elasticity is overpredicted by the ACI 318-89
equation for concretes with compressive strengths above 5000 psi.
It is also observed that the modulus of elasticity increases at a
decreasing rate after 14 days of curing.
Core tests indicated that the core compressive strengths were
lower than the cylinder strengths. This is true for all concretes.
As the concrete strength increases a larger correction was required
for the cores tests.
From the analysis of test results it is concluded that concretes
containing mineral admixtures have very low chloride ion permeability.
The test results of indicated that all the mixes had almost the
same chloride ion permeability. Thus it can be concluded that
concretes containing Class C fly ash only and concretes containing
19
both fly ash and silica fume have nearly the same chloride ion
permeability. Thus the compressive strength of concrete at higher
strength have a negligible influence on the rapid chloride ion
permeability of concrete. Concretes containing mineral admixtures
have a dense matrix and hence a lower chloride ion permeability,
especially at later ages.
LIST OF REFERENCES
(1)ACI Committee 363, "State-of-the Art Report on High-strength
Concrete, " ACI Journal, Proceedings V. 81, No. 4, July-August
1984, pp. 364-411.
(2)Anderson, A.R., "Research Answers Needed for Greater Utilization
of High-Strength Concrete," PCI Journal, V. 25, No. 4,
July-August 1980, pp. 162-164.
(3)Naik, T.R., and Ramme, B.W., "Effects of High-Lime Fly Ash Content
on Water Demand, Time of Set, and Compressive Strength of
Concrete", ACI Materials Journal, Vol. 87, No. 6,
November/December 1990, pp. 619-627.
(4)Naik, Tarun R., and Ramme, Bruce W., "Setting and Hardening of
High Fly Ash Content Concrete", 8th International Coal Ash
20
Utilization Symposium, ACAA, Washington, D.C., 1987.
(5)Naik, T.R., and Ramme, Bruce W., "High Early Strength Fly Ash
Concrete for Precast/Prestressed Products", PCI Journal, Nov.
Dec. 1990, pp.
(6)Chicago Committee on High-Rise Buildings, "High-Strength Concrete
in Chicago High-Rise Buildings", Task Force Report No. 5,
Chicago, IL, February 1977, 63 pages.
(7)Hester, W., "High-Strength Air-Entrained Concrete", Concrete
Construction, February 1977, pp. 77-82.
(8)Freedman, S., "High-Strength Concrete", Modern Concrete, Oct.,
Nov., Dec. 1970, and Jan., Feb. 1971.
(9)Perenchio, W.I., "An Evaluation of Some of the Factors Involved
in Producing very High-Strength Concrete", Bulletin No. RD014,
Portland Cement Association, Chicago, IL, 1973, 7 pages.
(10)ACI Committee 363, "Research Needs for High-Strength Concrete,"
ACI Materials Journal, V. 84, November-December 1987, pp.
559-561.
(11)AASHTO, "Specifications for Materials Testing", FHWA, 1989.
21
22
(12)Naik, T.R., "Evaluation of Factors Affecting High-Strength
Concrete Cores", Proceedings of the First Materials Engineering
Congress, ASCE, Denver, CO, August, 1991, pp. 216-222.
REP-125
23
TABLE 1: CONCRETE MIX AND TEST DATA CONCRETE SUPPLIER: Central Ready-Mix Concrete Co., Milwaukee, WI. ┌─────────────────────────────┬───────────────────────────────────────────┐ │Mix Number │ 1 │ 2 │ 3 │ ╞═════════════════════════════╪═════════════╪═══════════════╪═════════════╡ │Nominal Strength, psi │ 10,000 │ 11,000 │ 12,000 │ │ │ │ │ │ │Cement, Type I, lbs./cu.yd. │ 600 │ 700 │ 700 │ │ │ │ │ │ │Fly Ash, Type C, lbs./cu.yd. │ 350 │ 100 │ 100 │ │ │ │ │ │ │Silica Fume, lbs./cu.yd. │ - │ 70 │ 100 │
│Slurry, gallons │ - │ 12.7 │ 18.2 │ │ │ │ │ │ │Water, lbs./cu.yd. │ 303 │ 240 │ 274 │ │ │ │ │ │ │Water to cementitious ratio │ 0.3 │ 0.29 │ .30 │ │ │ │ │ │ │Sand, SSD, lbs./cu.yd │ 1,200 │ 1,280 │ 1,250 │ │ │ │ │ │ │1/2" Max. crushed limestone, │ │ │ │ │SSD, lbs./cu.yd. │ 1,650 │ 1,700 │ 1,700 │ │ │ │ │ │ │Slump, inches │ 6 │ 7-1/4 │ 10-1/2 │ │ │ │ │ │ │Air Content, % │ 0.3 │ 1.1 │ 0.3 │ │ │ │ │ │
│Air Temperature, Deg.F │ 68 │ 68 │ 69 │ │ │ │ │ │ │Concrete Temperature, Deg.F. │ 72 │ 69 │ 68 │ │ │ │ │ │ │Concrete Density, pcf │ 152 │ 152 │ 154 │ │ │ │ │ │ │ASTM Type A Retarding │ │ │ │ │Admixture, oz/cu.yd. │ 28.5 │ 20.8 │ 21 │ │ │ │ │ │ │ASTM Type F Super │ │ │ │ │Plasticizing Admixture, │ 198 │ 210 │ 240 │ │oz./cu.yd. │ │ │ │ │ │ │ │ │ │ │ │ │ │
└─────────────────────────────┴─────────────┴───────────────┴─────────────┘ S.I. Units: 1 lbs/cu yd. = 0.593 kg/cu m. 1 Liter = 29.57 x 10
3 oz.
1 inch = 25.4 mm
1 Deg. C = ( F - 32)/1.8
24
1 lbs/cu. ft. = 16.02 kg/cu. m.
TABLE 2: Concrete Strength Test Data, 10,000 psi (70 MPa) Specified Strength
Test Age Days
Compressive Strength, psi Splitting Tensile Strength, psi
4" x 8" Cyls 6" x 12" Cyls Actual
Average
Actual Average Actual Average
1
1 1
3519
3527 3343
3460
3731
3855 3183
3590
384
406 371
390
3 3 3
5095 5573 5175
5280
6667 2263 X 6596
6630
424 539 565
510
7 7 7
8280 7643 8917
8280
7463 6438 7746
7220
508 548 486
510
14 14 14
8638 7245 8280
8050
8277 7728 9249
8420
592 570 574
560
28 28
28
10191 8280
10151
9550
10350 10085
10209
10210
752 730
699
730
35 35 35
9633 9514 9514
9550
-- -- --
--
699 690 743
710
56 56 56
8837 10788 10800
10140
-- -- --
--
606 920 774
770
91 91 91
12900 13850 9160
11970
-- -- --
--
--
--
180 180 180
11940 12540 11150
11880
-- -- --
--
--
--
365 365 365
14010 13820 12420
13420
-- -- --
--
--
--
X Discarded S.I. Units:
25
1 psi = 0.0069 MPa
26
TABLE 3: Concrete Strength Test Data, 11,000 psi (77 MPa) Specified Strength
Test Age Days
Compressive Strength, psi Splitting Tensile Strength, psi
4" x 8" Cyls 6" x 12" Cyls Actual
Average
Actual Average Actual Average
1 1 1
3384 3503 3702
3530
4494 4565 4547
4590
354 358 385
370
3
3 3
6369
6449 5892
6240
5697
6016 7502
6900
367
429 376
390
7 7 7
7484 7803 8121
7800
8563 8581 8139
8430
557 584 601
580
14 14 14
9713 9475 11057
10090
10227 11058 10952
10750
690 659 760
700
28 28 28
10350 10948 9953
10420
10580 10828 10757
10720
836 849 915
870
35 35
35
11505 11226
12102
11610
-- --
__
--
924 902
937
920
56 56 56
10828 11544 11146
11170
-- -- --
--
841 1040 707
870
91 91 91
11540 10788 11186
11180
-- -- --
--
--
--
180 180 180
12938 14530 13933
13700
-- -- --
--
--
--
365 365 365
14013 13455 13535
13670
-- -- --
--
--
--
S.I. Units: 1 psi = 0.0069 MPa
27
TABLE 4: Concrete Strength Test Data, 12,000 psi (85 MPa) Specified Strength
Test Age Days
Compressive Strength, psi Splitting Tensile Strength, psi
4" x 8" Cyls 6" x 12" Cyls Actual
Average
Actual Average Actual Average
1 1 1
2707 3185 3225
3040
3397 3450 3397
3410
252 261 274
260
3 3 3
6430 6691 6487
6540
6522 6547 6729
6600
417 439 393
410
7 7 7
8957 8599 9236
8930
7785 8528 7254
7860
517 531 548
530
14 14 14
9912 10390 10549
10280
10386 10156 10315
10290
707 743 738
730
28 28 28
12579 13137 12341
12690
-- --
12452
12450
831 818 796
820
35
35 35
10987
12877 12141
12035
--
-- --
--
805
774 929
836
56 56 56
11624 13375 10828
11950
-- -- --
--
751 778 840
790
91 91 91
13176 14928 16082
14730
-- -- --
--
--
--
180 180 180
-- 14800 14980
14890
-- -- --
--
--
--
365 365
365
14700 14970
14850
14880
-- --
--
--
--
--
S.I. Units: 1 psi = 0.006895 MPa
28
TABLE 5: Modulus of Elasticity Test Data
┌──────┬──────────────────────┬────────────────────┬───────────────────┐ │Age, │ Average E, psi* │ Average E, psi* │ Average E, psi* │ │Days │ f'c = 10,000 psi │ f'c = 11,000 psi │ f'c = 12,000 psi │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │ 1 │ 3,750,000 │ 3,700,000 │ 3,650,000 │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │ 3 │ 4,050,000 │ 4,100,000 │ 3,950,000 │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │ 7 │ 4,850,000 │ 5,150,000 │ 5,000,000 │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │14 │ 5,400,000 │ 5,750,000 │ 5,650,000 │
├──────┼──────────────────────┼────────────────────┼───────────────────┤ │28 │ 5,450,000 │ 6,000,000 │ 6,150,000 │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │35 │ 5,700,000 │ 6,050,000 │ 6,100,000 │ ├──────┼──────────────────────┼────────────────────┼───────────────────┤ │56 │ 5,750,000 │ 6,000,000 │ 5,800,000 │ └──────┴──────────────────────┴────────────────────┴───────────────────┘ S.I. Units 1 psi = 0.006895 MPa 1 in. = 2.54 cms * Average of three tests
29
TABLE 6: CORE STRENGTH TEST DATA*
Test Performed in Accordance with the ASTM Test C-42 (Compressive Strength)
Center for By-Products Utilization, UWM
Core
Number
Age
Days
l/d
ratio**
Core Compressive
Strength (psi)
***
Correction
Equival. Cyl. Compressive
Strength (psi)
Average
(psi)
2-1 160 1.99 7,172 0.75 9,563
2-2 160 1.98 7,590 0.75 10,120 9,950
2-3 160 2.02 7,620 0.75 10,160
4-1 160 2.05 8,892 0.75 11,856
4-2 160 2.05 8,092 0.75 10,789 10,860
4-3 160 2.05 7,452 0.75 9,936
8-1 122 1.98 8,770 0.75 11,690
8-2 122 1.97 7,560 0.75 10,080 11,030
8-3 122 1.98 8,490 0.75 11,320
9-1 122 2.01 7,010 0.75 9,350
9-2 122 1.95 6,600 0.75 8,800 10,180
9-3 122 1.93 9,300 0.75 12,400
12-1 167 2.06 11,292 0.7 16,132
12-2 167 2.06 8,786 0.7 12,531 14,620
12-3 167 2.05 10,615 0.7 15,164
14-1 167 2.05 8,777 0.7 12,538
14-2 167 2.04 9,011 0.7 12,872 13,130
14-3 167 2.04 10,724 0.7 13,927
26-1 130 2.06 8,721 0.65 13,416
26-2 130 2.04 8,915 0.65 13,715 14,930
26-3 130 2.06 11,476 0.65 17,655
13-1 174 2.04 8,917 0.7 12,738
13-2 174 2.02 8,858 0.7 12,654 12,610
13-3 174 2.02 8,708 0.7 12,440
16-1 174 2.02 8,042 0.7 11,488
16-2 174 2.01 9,202 0.7 13,145 12,140
16-3 174 2.03 8,258 0.7 11,797
20-1 137 2.02 9,062 0.65 13,941
20-2 137 2.02 10,741 0.65 16,524 16,460
20-3 137 2.03 12,289 0.65 18,906
15-1 160 2.02 14,093 0.7 20,132
15-2 160 2.05 14,276 0.7 20,394 18,750
15-3 160 2.04 11,010 0.7 15,728
17-1 160 2.12 9,476 0.7 13,537
17-2 160 2.01 9,666 0.7 13,808 12,680
17-3 160 1.99 7,494 0.7 10,705
19-1 130 2.06 8,759 0.65 13,475
19-2 130 2.03 8,772 0.65 13,495 15,140
19-3 130 2.06 11,994 0.65 18,453
21-1 130 2,06 8,280 0.65 12,738
21-2 130 ERR ERR 0.65 - 15,270
21-3 130 2.03 11,565 0.65 17,792
22-1 130 2.04 11,672 0.65 17,957
22-2 130 2.05 8,593 0.65 13,220 15,990
22-3 130 2.05 11,154 0.65 17,160
25-1 130 2.06 10,580 0.65 16,277
25-2 130 2.06 6,900 0.65 10,615 13,680
25-3 130 2.08 9,190 0.65 14,138
30
* All cores were drilled in a direction perpendicular to the direction of casting the concrete structural beam element.
** Length measured after capping of the cores.
*** See Table 7 - Correction for determining equivalent cylinder ("design") strength. l/d correction was not required per ASTM C-42.
S.I. Units
1 psi = 0.006895 MPa
1 in. = 2.54 cms
31
TABLE 7: Equivalent Cylinder Strength Correction Factor for Core Strength (Ref. 12). ╔════════════════════╤════════════════════════╗ ║ │ ║ ║ Core │ Correction Factor ║ ║ Strength, psi │ for Core Strength* ║ ╟────────────────────┼────────────────────────╢ ║ │ ║ ║ 3,000 │ 0.95 ║
╟────────────────────┼────────────────────────╢ ║ 4,000 │ 0.90 ║ ╟────────────────────┼────────────────────────╢ ║ 6,000 │ 0.85 ║ ╟────────────────────┼────────────────────────╢ ║ 8,000 │ 0.80 ║ ╟────────────────────┼────────────────────────╢ ║ 10,000 │ 0.75 ║ ╟────────────────────┼────────────────────────╢ ║ 12,000 │ 0.70 ║ ╟────────────────────┼────────────────────────╢ ║ 15,000 │ 0.65 ║ ║ │ ║ ╚════════════════════╧════════════════════════╝
*To obtain equivalent 6" x 12" (150 mm x 300 mm) Cylinder
Strength.
32
TABLE 8: Rapid Chloride Ion Permeability Test Data
Mix
Number
Beam Core
Number
Test Slice
Location
Maximum Current
During Test
(Amperes)
Actual Total
Charge Passed
(Coulombs)
Average Total
Charge Passed
(Coulombs)
AASHTO Chloride
Permeability
Designation**
1
6
Top
Upper
Lower
Bottom
0.012
0.014
0.011
0.012
253
302
238
242
259
Very Low
2
16
Top
Upper
Lower
Bottom*
0.012
0.013
0.012
--
238
300
252
--
263
Very Low
3
23
Top
Upper
Lower
Bottom
0.009
0.014
0.015
0.014
177
294
283
284
260
Very Low
* Discarded because of a crack ** Per AASHTO T-277 (Ref. 9)
Permeability Rating Charge, Coulombs Negligible Less than 100 Coulombs Very Low 100 to 1,000 Coulombs Low 1,000 to 2,000 Coulombs Moderate 2,000 to 4,000 Coulombs High Greater than 4,000 Coulombs
REP-125
