AMEC Earth & Environmental Limited
2227 Douglas Road, Burnaby, BC
Canada V5C 5A9
Tel +1 (604) 294-3811
Fax +1 (604) 294-4664
www.amec.com
A REVIEW OF
HARD-CEM IN CONCRETE
SUBMITTED TO:
TECK COMINCO METALS LTD.
SUITE 600-200 BURRARD STREET
VANCOUVER B.C. V6C 3L9
SUBMITTED BY:
AMEC EARTH & ENVIRONMENTAL LIMITED
BURNABY, BC
3 SEPTEMBER 2004
AMEC FILE VA06222
Teck Cominco Metals Ltd.
A Review of Hard-Cem in Concrete
3 September, 2004
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY .............................................................................................................. 1
1.0
INTRODUCTION.................................................................................................................. 4
2.0
DRY-SHAKE SURFACE HARDENERS .............................................................................. 4
3.0
HARD-CEM PROPORTIONING AND BATCHING .............................................................. 5
4.0
COMPARATIVE PERFORMANCE OF HARD-CEM............................................................ 5
4.1 Density ........................................................................................................................ 6
4.2 Water Demand ............................................................................................................ 6
4.3 Bleeding ...................................................................................................................... 7
4.4 Setting Time ................................................................................................................ 7
4.5 Compressive Strength................................................................................................. 7
4.6 Drying Shrinkage......................................................................................................... 7
4.7 Freeze/Thaw Durability ............................................................................................... 8
4.8 Deicing Chemical Scaling Resistance......................................................................... 8
4.9 Colour ........................................................................................................................ 8
5.0
ABRASION RESISTANCE................................................................................................... 8
5.1 Taber Abraser Resistance........................................................................................... 8
5.2 Abrasion Resistance Using Robinson – Type Floor Tester......................................... 9
5.3 Other Abrasion Tests .................................................................................................. 9
6.0
ENVIRONMENTAL CONSIDERATIONS........................................................................... 10
7.0
FIELD PERFORMANCE .................................................................................................... 11
8.0
LIMITATIONS AND CLOSURE.......................................................................................... 11
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TABLE OF CONTENTS
Page
LIST OF APPENDICES
APPENDIX A AMEC Comparative Studies
Table 1: Concrete Mixture Designs and Plastic Properties
Table 2: Study Compressive Strength Test Data
Table 3: Deicing Chemical Scaling Resistance to ASTM C672
Table 4: Abrasion Resistance using ASTM C1353 Taber Abraser Test Method
Figure 1: Compressive Strength
Figure 2: Taber Abraser test setup
Figure 3: Hard-Cem specimen after 1000 cycles of testing in Taber Abraser
Figure 4: Robinson-Type Floor Tester general setup
Figure 5: Hard-Cem specimen after 500 revolutions in the Robinson-Type Floor
Tester
APPENDIX B Product Literature for Hard-Cem
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3 September, 2004
EXECUTIVE SUMMARY
AMEC Earth & Environmental Limited (AMEC) was retained by Teck Cominco Metals Ltd.
(TCML) to conduct a review of the use of Hard-Cem as a concrete hardener. This review is
based on:
a)
Examination of product literature and test data provided by Cementec Industries Inc
b)
Review of the results of tests conducted by AMEC on a plain control concrete and concrete
containing Hard-Cem.
c)
Field examination of an approximately one-month-old industrial floor slab in Calgary made
with concrete containing Hard-Cem.
The following is a summary of the main findings:
1. Hard-Cem is promoted for use in lieu of conventional dry-shake surface hardeners, such as
mineral shakes, which are primarily used for increasing the abrasion and wear resistance of
industrial concrete floors.
2. Hard-Cem differs from dry-shake surface hardeners in that it is added integrally to the
concrete during batching and mixing operations, compared to dry-shakes, which are
broadcast onto the top surface of the freshly screeded concrete and floated and trowelled in.
Thus Hard-Cem is integrally distributed throughout the full thickness of the concrete,
compared to dry-shakes which typically are only in the top 2 to 3 mm of surface concrete.
3. The recommended addition rate for Hard-Cem is 40 kg/m3. This equates to about 0.1 kg/m2
of Hard-Cem being contained in the top 2 to 3 mm of the concrete vs. about 3.5 kg/m2 of a
typical dry-shake. The Hard-Cem is, however, much finer than dry-shake hardeners and
with its high specific surface area appears to harden the paste matrix of the concrete, rather
than providing abrasion resistance through hard wearing coarser particles, like dry-shakes.
4. Hard-Cem has an advantage over dry-shakes in that it can be used with air-entrained
concretes in exterior exposure conditions. Most manufactures of dry-shake hardeners
recommend against their use in concretes with more than 3% air content because of
concerns about the potential for the formation of blisters and peeling in the finished concrete
surface, as discussed in this report. Hard-Cem concrete does not have this limitation.
5. The results of comparative tests conducted by AMEC on Plain Control and Hard-Cem
modified concretes indicates that Hard-Cem has no adverse effects on the properties of the
plastic (wet) and setting and hardening concrete. In fact, the Hard-Cem appears to have a
number of beneficial attributes:
a. Hard-Cem addition appears to have a modest plasticizing effect (slump
increased from 80 to 130mm).
b. Hard-Cem addition results in a significant reduction in bleeding in the plastic
concrete (1.2% bleeding vs. 2.2% bleeding for the plain control concrete).
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Hard-Cem has no adverse effect on the ability to entrain air in the concrete. Hard-Cem
slightly reduces the initial setting time and slightly extends the final setting time of the
concrete (compared to a plain control concrete) at both 23oC and 10oC ambient curing
temperatures. Overall, however, the effects are small and not likely to be noticed by
concrete placing and finishing contractors.
6. Hard-Cem addition appears to be neutral with respect to compressive strength development
up to 28 days, and result in a slight increase in strength at 56 days for concrete cured at
23oC. At 10oC curing temperature the Hard-Cem concrete gained strength more rapidly
than the plain control concrete at all ages up to 28 days. If advantage is taken of the
modest plasticizing effect of Hard-Cem to slightly reduce water demand for a given slump,
then some additional increase in compressive strength of concrete containing Hard-Cem
could be expected.
7. Deicing salt scaling testing to ASTM C672 to 50 cycles demonstrated excellent salt scaling
resistance in air-entrained concrete containing Hard-Cem.
8. Freeze-thaw durability tests to 300 cycles in the ASTM C666, Procedure A Test (freezing
and thawing in water) were conducted on a CSA Class C-1 (max 0.40 w/cm ratio) Control
Mix with 20% fly ash replacement for Portland cement and a CSA Class C-2 (max 0.45
w/cm ratio) Hard-Cem mix with no fly ash. The Control Mix with fly ash had a Durability
Factor of 84.8% after 300 cycles of freezing and thawing. The Hard-Cem mix had an
excellent durability factor of 90.8% after 300 cycles of freezing and thawing. This is well in
excess of the minimum durability factor of 80% specified by many authorities.
9. Hard-Cem is darker in colour than Portland cement and concrete made with Hard-Cem was
observed to be darker than a plain control Portland cement concrete. This darker colour
may be an issue for certain architectural concretes but is not likely to be of concern for most
industrial flooring and infrastructure projects.
10. Taber Abraser Resistance testing on concrete with and without Hard-Cem shows enhanced
abrasion resistance in the concrete with Hard-Cem.
11. Abrasion testing using the Robinson-Type floor tester and steel wheels to simulate pallet
jack traffic shows a 66% reduction in mass loss and 43% reduction in the depth of wear in
the wheel path after 5000 revolutions in concrete containing Hard-Cem, compared to a plain
control concrete.
12. A review of environmental considerations was largely based on the conclusions reached in
the Hemmings and Associates LLC (Hemmings) report to TCML regarding the Trail barren
slag and finely ground GS-Cem produced from this slag. Based on the fact that Hard-Cem
is produced from the same barren slag as GS-Cem, AMEC considers that the same
conclusions reached by Hemmings for the Trail barren slag and Cementec GS-Cem ground
slag are also applicable to Hard-Cem. In brief, no environmental issues of concern relating
to the use of Hard-Cem in concrete are apparent. . TCLP (leaching) tests conducted by
AMEC on a rubble concrete containing Hard-Cem that has been subjected to accelerated
carbonation and aging, as recommended in the Hemmings report for GS-Cem confirmed
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that there was no significant increase in leachability of regulated metals from the concrete
rubble.
13. Finally, field examination of an approximately one month old industrial warehouse floor slab
in Calgary, made with ready-mix concrete containing 40 kg/m3 of Hard-Cem, indicated
excellent performance. The floor was hard, dense and strong and readily resisted
scratching and gouging with a hand-held metal object. The contractor for the project
expressed a high level of satisfaction regarding the behaviour of the Hard-Cem during
installation and in subsequent performance.
To summarize, AMEC is not aware at this time of any technical reasons which Hard-Cem
should not be used in concrete. It significantly enhances the hardness and abrasion and wear
resistance of the concrete, as claimed by the manufacturer, and based on the testing completed
by AMEC to date does not appear to have any detrimental effects on the properties of the
plastic or hardened concrete. In fact, there is enhancement of several of the plastic and
hardened properties of concrete, as described in this report.
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1.0 INTRODUCTION
Teck Cominco Metals Ltd. (TCML) has asked AMEC Earth & Environmental Limited (AMEC) to
review and comment on the suitability of Hard-Cem for use in concrete. Hard-Cem is
manufactured by Cementec Industries Inc (Cementec) in Calgary, Alberta from the Teck
Cominco fumed smelter slag from Trail, BC.
It is understood that Hard-Cem is manufactured by grinding the fumed smelter slag to a
prescribed fineness, in conjunction with other proprietary additions, at the Cementec plant.
Hard-Cem is sold as an integral concrete hardener, for addition to ready-mix or other concretes.
It is promoted for use in lieu of conventional surface applied hardeners such as so-called
mineral shakes or emery shakes. Hard-Cem differs from such products in that it is added
integrally to the concrete during batching and mixing operations, compared to the conventional
surface shakes which are broadcast onto freshly placed and screeded concrete slabs and
floated and trowelled in while the concrete is still plastic (wet). Thus Hard-Cem is integrally
dispersed throughout the full thickness of the concrete, whereas the shakes are only in the top
surface (about 2 to 3 mm thick) of the concrete.
2.0 DRY-SHAKE SURFACE HARDENERS
Dry-shake hardeners can be grouped into three broad categories:
a)
Mineral aggregate shakes, e.g. natural silica, quartz and basalt (sometimes called
traprock).
b)
Emery shakes, e.g. natural corundum (imported mainly from Turkey) and various synthetic
(manufactured) products, such as magnesium oxide slag and nickel slag-based shakes.
c)
Metallic aggregate shakes (made from iron filings).
The mineral aggregate shakes, which have the lowest Moh’s hardness values (typically 6 to 7.5
range) are primarily intended for use in light to medium duty industrial flooring applications.
The emery shakes, which typically have Moh’s hardness values in the 8 to 9 range, are used in
both medium and heavy duty industrial flooring applications. The metallic aggregate shakes are
the most expensive of all the shakes and are typically only used in severe abrasion/wear
applications, where their high cost can be justified.
The Teck Cominco fumed smelter slag, and Hard-Cem have a Moh’s hardness of about 6.
While Hard-Cem can be compared in hardness to the mineral shakes, the mechanism of
hardening of the concrete appears to be different to dry-shake hardeners, as discussed in
Section 3.0 which follows. In brief, Hard-Cem appears to harden the paste matrix, resulting in an
abrasion and wear resistance greater than that which would be predicted based simply on
Moh’s hardness values. This is well demonstrated in the Cementec “Hard-Cem Abrasion
Resistance Test Program (ASTM C1353-98)” data shown in Appendix B.
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The addition rate for dry-shake surface hardeners varies depending on:
a)
The manufacturer (most dry-shakes contain varying amounts of cementitious or other
fillers and chemical admixtures, in addition to the hard aggregate).
b)
The floor exposure condition (light, medium, heavy or severe duty).
The range of recommended dry-shake addition rates varies from lows of about 3 kg/m2 to highs
of up to 10 kg/m2 with addition rates of around 5 kg/m2 being common. For many dry-shakes the
hard aggregate content in the dry-shake comprises about 70% of the formulation. Thus the
effective amount of hard aggregate in the dry-shake ranges from about 2.1 to 7.0 kg/m2 with
quantities around 3.5 kg/m2 being common. At a density of 3500 kg/m3 the dry-shake would be 1
mm thick. However, after the dry-shake is floated and trowelled into the concrete it is typically
contained in the upper 2 to 3 mm of the concrete, since the dry-shake is blended in with the
cement paste and mortar during the floating and trowelling finishing processes.
3.0 HARD-CEM PROPORTIONING AND BATCHING
Cementec recommends that Hard-Cem be added integrally to the concrete at an addition rate of
40 kg/m3. No adjustment to the concrete mixture proportions is required, other than to reduce
the sand content of the mix by a volume equivalent to the Hard-Cem, in order to prevent the mix
from overyielding. If you remove 30 kg/m2 of sand (bulk density = 2650 kg/m3 ) and replace it
with 40 kg/m3 of Hard-Cem (bulk density = 3550 kg/m3 ) the yield of the mix will be maintained at
about the same value.
A 150 mm thick concrete slab, 1.0 m2 would have a mass of 6 kg/m2 of Hard-Cem. This 6 kg/m2
is, however, dispersed throughout the full 150 mm thickness of the slab. Only about 0.1 kg/m2 is
contained in the upper 2 to 3 mm of the slab. Compare this with about 3.5 kg/m2 of dry-shake in
the upper 2 to 3 mm of the concrete with dry-shake applied hardeners.
It is thus apparent that to be effective as a hardener, the Hard-Cem has to alter the properties of
the concrete in a manner different to that achieved by conventional dry-shakes. It is believed
that this is primarily achieved by the substantially greater fineness and specific surface area of
the Hard-Cem relative to the conventional dry-shakes and hence it ubiquitous dispersion
throughout the paste matrix in the concrete. This results in an integral hardening of the paste
fraction of the concrete. This is highly beneficial regarding the abrasion and wear resistance of
the concrete. The dry-shake hardeners by contrast rely on the almost fine-sand gradation of the
mineral or emery shakes to provide abrasion and wear resistance.
4.0 COMPARATIVE PERFORMANCE OF HARD-CEM
AMEC has conducted a series of tests to evaluate the behaviour of Hard-Cem in both plastic
and hardened concrete. Its performance was compared against a plain control concrete without
any Hard-Cem. Details of the two mixture designs and plastic properties are given in Table 1, in
Appendix A. The base mixture was designed to satisfy a CSA A23.1-00, Table 11, Class C-2
exposure condition, i.e. be suitable for use in non-structurally reinforced concrete exposed to
chlorides and freezing and thawing. CSA cites examples of such concretes as: garage floors,
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porches, steps, pavements, sidewalks, curbs and gutters. Concrete pavements, subjected to
abrasion and wear from vehicular traffic, snow ploughs, etc., would also be examples of CSA
Class C-2 exposure concrete which could benefit from incorporation of Hard-Cem in the
concrete.
Note: Dry-shake surface hardeners are not recommended for use in such exterior exposure
concretes. The reason for this is that concrete exposed to freezing and thawing and deicing
chemicals has to be air-entrained to provide frost resistance. The application of dry-shake
hardeners to air-entrained concrete can give rise to the formation of blisters and peeling,
because of entrapment of bleedwater caused by delayed bleeding when air-entraining
admixtures are used. Thus most dry-shake surface hardener manufactures recommended that
the concrete not contain more than 3% air content in the plastic concrete.
CSA A23.1-00 Tables 10 and 14 requires concrete with a Class C-2 exposure to have 5 to 8%
air content in the plastic concrete. Thus dry-shake surface hardeners should not be applied to
such concretes. Hard-Cem, by contrast, being integrally mixed into the concrete does not suffer
from such limitations and is well suited to use in air-entrained concretes. It is thus suitable for
addition to CSA A23.1-00 Class C-1, C-2, C-3, C-4, F-1 and F-2 exposure concretes, as well as
interior, non air-entrained concretes.
CSA A23.1-00 Class C-2 exposure concrete is required to have a maximum water/cementing
materials ratio of 0.45 and minimum 28 day compressive strength (with standard moist curing at
23oC) of 32 MPa.
In proportioning the Hard-Cem mixture, 33 kg/m3 of fine aggregate (sand) was replaced with 40
kg/m3 of Hard-Cem and the coarse aggregate proportions were adjusted to produce a yield of
1.00 m3. The water/cement ratio was kept constant. The plain control and Hard-Cem mixes
were designed to have an air content of 6±1%; actual air contents were 5.7 and 5.2%
respectively. The incorporation of Hard-Cem in the mix had little effect on the air entraining
admixture dosage required as shown in Table 1 in Appendix A.
Observations of the effects of Hard-Cem on the plastic and hardened properties of the concrete
in the AMEC Study are provided in Sections 4.1 to 4.9 which follow.
4.1
Density
The plastic density of the Hard-Cem concrete (2373 kg/m3) was a bit higher than for the plain
control concrete (2349 kg/m3). This is mainly because Hard-Cem has a greater bulk relative
density (3.55) than the sand used (2.65).
4.2
Water Demand
With the water content of both mixes being kept the same (at 147 L/m3) and hence
water/cement ratio being kept the same at 0.45, the Hard-Cem mix had a higher slump (130
mm) compared to the plain control concrete (80 mm). This is a beneficial attribute for HardCem, as it indicates that Hard-Cem has a modest plasticizing effect on concrete workability.
Conversely, if slump was maintained at 80 mm, the water demand of the Hard-Cem concrete
could be reduced.
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4.3
Bleeding
A noticeable reduction in bleeding was noted in the Hard-Cem mix (1.2%) compared to the plain
control concrete (2.2%). This is beneficial to the concrete placing and finishing processes. It is
also beneficial with respect to the long-term durability of the concrete, since it reduces the
formation of continuous capillary pores and bleed channels, which are potential paths for entry
of aggressive agents such as chlorides, deicing chemicals and sulphate solutions, which could
reduce concrete durability.
4.4
Setting Time
The addition of Hard-Cem slightly reduced the initial set time of the Hard-Cem mix at 23oC
ambient temperature (260 mins) compared to the plain control concrete (300 mins). Final set
was, however, slightly delayed in the Hard-Cem mix (475 mins) compared to the plain control
mix (445 mins). At 10 oC the same trends were observed. Initial set of the Hard-Cem mix (365
mins) was more rapid than in the plain control concrete (430 mins). Final set in the Hard-Cem
mix (645 min) was slightly longer than in the plain control concrete (625 mins). These test
results demonstrate that the ambient curing temperature has a far greater influence on setting
time than Hard-Cem addition. Most finishers would likely not notice any significant difference in
finishing time in a Hard-Cem concrete compared to a plain control concrete.
4.5
Compressive Strength
Compressive strength test data is summarized in Table 2 and graphically illustrated in Figure 1
in Appendix A. The compressive strength data shows that at 23oC curing temperature the HardCem concrete developed strength at essentially the same rate as the plain control concrete up
to age 28 days. Strength at 56 days was, however, slightly greater in the Hard-Cem concrete.
At 10oC curing temperatures the Hard-Cem concrete appears to develop strength more rapidly
than the plain control concrete at all ages up to 28 days. Further, it should be noted that the
Hard-Cem concrete had a slump of 130 mm, compared to a slump of 80 mm in the plain control
concrete. If the water content in the Hard-Cem mix (and hence water/cement ratio) was
reduced to provide a slump of 80 mm, then the Hard-Cem concrete could be expected to
provide even higher compressive strengths than the plain control concrete at all ages at both
23oC and 10 oC curing temperatures.
4.6
Drying Shrinkage
Given that the addition of Hard-Cem does not increase the water demand of the concrete, for a
given slump (in fact it slightly reduces it), the expectation is that Hard-Cem addition will not
cause any increase in drying shrinkage or the potential for restrained drying shrinkage cracking.
With respect to plastic shrinkage and the potential for plastic shrinkage cracking, careful
attention to curing (preferably using moist curing methods as detailed in CSA A23.1-00, Section
21) is recommended, in view of the reduced bleeding in concrete containing Hard-Cem.
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4.7
Freeze/Thaw Durability
Freeze-thaw durability tests to 300 cycles in the ASTM C666, Procedure A Test (freezing and
thawing in water) were conducted on a CSA Class C-1 (max 0.40 w/cm ratio) Control Mix with
20% fly ash replacement for Portland cement and a CSA Class C-2 (max 0.45 w/cm ratio) HardCem mix with no fly ash. The Control Mix with fly ash had a durability factor of 84.8% after 300
cycles of freezing and thawing. The Hard-Cem mix had an excellent durability factor of 90.8%
after 300 cycles of freezing and thawing. This is well in excess of the minimum Durability Factor
value of 80% specified by many authorities. This testing demonstrates that Hard-Cem is well
suited for use in properly air entrained concretes in external exposure environments subjected
to freezing and thawing, e.g. pavements, bridge decks, curb and gutter, driveways, etc.
4.8
Deicing Chemical Scaling Resistance
Deicing chemical scaling tests to ASTM 672 to 50 cycles were conducted. Results of visual
ratings and mass loss on the plain control and Hard-Cem concretes after 50 cycles are
summarized in Table 3 in Appendix A. After 50 cycles of testing, scaling was low in the plain
control concrete and even lower in the Hard-Cem concrete. The allowable amount of scaling
specified by different authorities for concrete flatwork subjected to deicing chemicals ranges
from values in the 0.4 to 1.0 kg/m2 range after 50 cycles. With values of 0.16 and 0.14 kg/m2
mass loss after 50 cycles in the plain control and Hard-Cem concretes respectively, the values
are well below the 0.4 kg/m2 specified by some authorities. This represents excellent deicing
chemical scaling resistance.
4.9
Colour
Hard-Cem is darker in colour compared to Portland cement or fly ash. Thus concrete containing
Hard-Cem has a slightly darker grey colour than conventional concretes. This may be an issue
for some architectural concretes, but may not be of concern for most industrial flooring or
infrastructure applications. It should, however, be recognized that the colour of the exposed
concrete surface will change with time as a result of carbonation and general weathering and
wear.
5.0 ABRASION RESISTANCE
5.1
Taber Abraser Resistance
AMEC conducted Taber Abraser tests to ASTM C 1353 on the Plain Control and Hard-Cem
concretes, at ages 28 and 56 days. Test results are reported in Table 4 in Appendix A. Figure
2 shows a specimen being tested in the Taber Abraser. Figure 3 shows a Hard-Cem specimen
after 1000 cycles of testing in the Taber Abraser.
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The test results provided in Table 4 in Appendix A show that Hard-Cem increases the abrasion
resistance of the concrete at both 28 and 56 days. Mass loss at 56 days is lower than at 28
days, as expected, given the continuing strength development in the concretes. Also note the
lower mass loss in the bottom (cast) face of the concretes compared to the top finished surface.
This is also as expected, given the well-known reduction in strength of surface concrete, relative
to concrete at depth because of the effects of bleed water migration to the top concrete surface.
The enhanced abrasion resistance (reduced mass loss) in the Hard-Cem concrete compared to
the plain control concrete can likely be attributed in part to the reduced bleeding in the HardCem concrete.
5.2
Abrasion Resistance Using Robinson – Type Floor Tester
AMEC conducted tests for abrasion resistance of the plain control and the Hard-Cem concretes
using the ASTM C 627 Robinson-Type Floor Tester. While this test method was designed by
ASTM for use on Ceramic Floor Tile Installations, it has been used by AMEC and others in the
past to evaluate the abrasion and wear resistance of a variety of different types of floor and
coating systems, using different types of wheels and loads. Wheel types used have included
steel, hard urethane, and solid and pneumatic rubber tires. In this study AMEC used small steel
wheels, to simulate pallet jacks and obtain accelerated test data. Figure 4 shows the general
set-up for the Robinson-Type Floor Tester.
The test was run for 5000 revolutions on 28 day old concrete. The load on each of the three
wheels was 90.7 kg (200lb) and the mass of the metal frame (including steel wheels) was 88.2
kg (194 lb). The mass of abraded concrete and average depth of wear in the wheel path, after
5000 revolutions, was determined. Test results are summarized in Table 5 in Appendix A.
Figure 5 shows the Hard-Cem test concrete after 500 revolutions in the Robinson-Type Floor
Tester.
The benefits of Hard-Cem addition to the concrete were well demonstrated in this aggressive
test. Visually the plain control concrete suffered much deeper wear in this test, exposing coarse
aggregate and leaving a rougher surface in the wheel travel path. By contrast the Hard-Cem
concrete wear occurred mainly in the surface mortar fraction of the concrete, leaving a relatively
smooth surface in the wheel travel path, with little exposed coarse aggregate. The Hard-Cem
concrete had only 57% of the depth of wear of the Plain Control concrete and only 34% of the
mass loss.
5.3
Other Abrasion Tests
There are ASTM abrasion test methods designed for use with concrete such as the following:
a)
ASTM C779 Standard Test Method for Abrasion Resistance of Horizontal Concrete
Surfaces using either
a. Revolving discs and abrasive grit
b. Steel dressing wheels
c. Rotating ball bearings
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b)
ASTM C418 Standard Test Method for Abrasion Resistance of Concrete by Sandblasting
c)
ASTM C1138 Standard Test Method for Abrasion Resistance of Concrete (Underwater
Method).
While useful additional information could be obtained by conducting these tests, the test
apparatus is not readily available in Canada. AMEC believes that the Robinson-Type Floor
Tester provides a good indication of the enhancement in abrasion resistance achievable with
Hard-Cem in concrete subjected to rolling wheel loads, such as industrial floors, pavements and
bridge decks. For underwater applications there may be merit in running the ASTM C1138 test,
which uses steel balls and a high-speed impeller.
6.0 ENVIRONMENTAL CONSIDERATIONS
A detailed Environmental review of the Teck Cominco Trail fumed smelter slag and the finely
ground Cementec Product GS-CEM produced from this slag was provided in the Hemmings and
Associates LLC report to Teck Cominco Metals Ltd dated October 31, 2002. Hard-Cem is
produced from the same Teck Cominco Trail fumed smelter slag as GS-Cem, but is more
coarsely ground. As such, it is likely to have leachability characteristics intermediate between
those of the barren fumed smelter slag and the more finely ground GS-Cem.
The Hemmings report concluded (amongst other conclusions) that:
•
The trace metals present in the slag are contained and chemically bound (sequestered) in
either glassy silicate phases or in crystalline phases (such as wustite, iron silicates,
franklinite, magnetite), both of which have good chemical stability and very limited solubility
under normal environmental exposure conditions.
•
The TCML slag and GS-Cem are non-regulated products. In their unbound form, the
available TCLP data indicate that they have high chemical stability and low solubility and do
not pose a threat to the environment in terms of leaching of trace metals into surface and
ground water. In Alberta, zinc slag falls under Code B1220 and is not regulated as
hazardous
•
In relative terms, the leachability of the unbound granulated zinc slag is comparable with fly
ash. The elements Ba, Co, Fe and Zn have higher leachability in the slag; whereas Al, B, Cr
and Zr have higher leachability in the fly ash.
•
Given the confirmation by actual TCLP data, it is H&A’s opinion that there is a very low
probability that the slag will leach hazardous components when it is present as an SCM in
concrete in service. Therefore, there is no basis for the concern that the heavy metals
present in the slag will leach from concrete structures. Cement-based stabilization and
solidification is, in fact, commonly used as an effective strategy for hazardous waste
containment.
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3 September, 2004
•
A question was raised in the Hemmings and Associates LLC report as to what would be the
effect of aging and carbonation on a rubble concrete containing Hard-Cem. A subsequent
investigation conducted by AMEC demonstrated that accelerated aging of a concrete
containing Hard-Cem (using forced carbonation) did not result in any significant increase in
the leachability of regulated metals from the rubble concrete in TCLP tests. As such, under
normal conditions of handling and management, the disposal of concrete demolition waste
and rubble containing Hard-Cem in recycling operations (e.g. as road base or land fill),
would not be expected to cause any problems in relation to heavy metals leaching.
In summary, AMEC considers that the conclusions reached in the Hemmings report with respect
to the chemical stability and leachability of the barren slag and GS-Cem can also be applied to
Hard-Cem. There would not appear to be any environmental concerns related to the use of
Hard-Cem in Concrete.
7.0 FIELD PERFORMANCE
AMEC understands that Cementec has had favourable feedback from the field from Owners,
concrete suppliers, placers and finishers and contractors who have used Hard-Cem in industrial
floor applications. While in Calgary on 15 January 2003, Dr. D.R. Morgan had the opportunity to
examine an approximately one month old, 30,000 sq.ft. paper storage industrial warehouse in
S.E. Calgary containing 40 kg/m3 Hard-Cem. A new section of floor slab concrete containing
Hard-Cem has also just been placed the same day. In an interview with the Contractor he
indicated a high level of satisfaction by the Owner and the entire concrete supply and
construction crew regarding the behaviour of the concrete containing Hard-Cem. Placing,
finishing, setting and hardening characteristics were all considered excellent.
The entire 2,800 m2 were placed in one day, without any construction joints. The bays between
columns were saw-cut into 4 segments, with control joint spacing at about 5 m on centres. Saw
cutting was initiated as soon as the concrete was hard enough to walk on without indentation,
using the Soff-Cutt dry sawing method. The quality of the saw-cut control joints was observed
to be excellent, with no significant ravelling or edge damage. The entire floor slab was
observed to be essentially crack free (other than for a couple of short, very minor hairline cracks
at re-entrant corners). Curling at joints was observed to be minimal. The finished floor surface
was observed to be very smooth, dense and hard. It could not be gouged with a hand-held
metal object.
In short, the overall quality of this industrial warehouse floor was observed to be excellent. It is
understood that Cementec has received similar feedback from Owners, Ready-Mix Suppliers
and Contractors regarding other industrial floors in which Hard-Cem has been used.
8.0 LIMITATIONS AND CLOSURE
This report is based on review of the documents and test results noted in this report and
AMEC’s general knowledge and experience in concrete technology. It has been prepared for
the exclusive use of Teck Cominco Metals Ltd. Any use which a third party makes of this report,
or any reliance on, or decisions made based on it, are the responsibility of such third parties.
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3 September, 2004
APPENDIX A
AMEC Comparative Studies
Table 1: Concrete Mixture Designs and Plastic Properties
Table 2: Study Compressive Strength Test Data
Table 3: Deicing Chemical Scaling Resistance to ASTM C672
Table 4: Abrasion Resistance using ASTM C1353 Taber Abraser Test Method
Figure 1: Compressive Strength
Figure 2: Taber Abraser test set-up
Figure 3: Hard-Cem specimen after 1000 cycles of testing in Taber Abraser
Figure 4: Robinson-Type Floor Tester general set-up
Figure 5: Hard-Cem specimen after 500 revolutions in the Robinson-Type Floor Tester
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Table 1: Concrete Mixture Designs and Plastic Properties
Mixture Proportions kg/m3
Material
Cement Type10
Hard-Cem
Coarse Aggregate (20 mm SSD)
Coarse Aggregate (14 mm SSD)
Fine Aggregate (SSD)
Water
Air Entraining Admixture (MBVR)
Total
Slump, mm
Air Content, %
Water/Cement Ratio
Plastic Density kg/m3
Concrete Temperature oC
Setting Time, mins to ASTM C403
Initial Set at 23 oC
Final Set at 23 oC
Initial Set at 10 oC
Final Set at 10 oC
Bleeding, % to ASTM C232
Plain Control
Hard-Cem
327
0
729
397
749
147
0.13 L
2349
80
5.7
0.45
2349
19
328
40
740
402
716
147
0.10 L
2373
130
5.2
0.45
2373
21
300
445
430
625
2.16
260
475
365
645
1.24
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Table 2: Compressive Strength Test Data
Compressive Strength (MPa)
Age (days)
Curing
Temperature
23 oC
o
10 C,
Plain Control
Hard-Cem
1 day
3 days
13.5
13.3
21.7
19.9
7 days
26.6
26.6
28 days
41.9
42.7
56 days
45.4
48.4
1 day
6.0
8.5
3 days
16.2
19.8
7 days
22.8
26.4
28 days
31.2
39.6
Table 3: Deicing Chemical Scaling Resistance to ASTM C672
Mix
Designation
Plain Control
Hard-Cem
Mass Loss
No.
of Cycles
Visual Rating
(0-5)
g
kg/m2
5
10
15
25
50
5
10
15
25
50
1
1
1
2
2
1
1
1
1.5
1.5
6.3
7.2
4.2
6.5
0.14
0.16
0.09
0.14
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Table 4: Abrasion Resistance using ASTM C1353
Taber Abraser Test Method
Mass Loss After 1000 Cycles (g)
Mix Designation
Test Age (Days)
Top of Specimen
Bottom of Specimen
Plain Control
25
56
7.19
6.04
4.42
Hard-Cem
28
56
6.64
5.38
3.88
Note: Test conducted using 1000 g load on Calibrade H-22 abrasive wheels.
Table 5: Abrasion Resistance using ASTM C627
Robinson-Type Floor Tester
Mix
Designation
Abrasion Mass Loss
(g)
Average Abraded Depth
(mm)
Plain Control
260.8
2.02
Hard-Cem
89.6
1.16
Notes: Wheel type: Steel
No. of revolutions: 5000
Load on each of three wheels: 90.7 kg (200lb)
Mass of frame, including wheels: 88.2 kg (194lb)
Age of concrete at test: 28 days
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60
55
Compressive Strength (MPa)
50
45
40
35
30
25
20
15
Plain Control 23 C
Plain Control 10 C
Hard-Cem 23 C
Hard-Cem 10 C
10
5
0
0
7
14
21
28
35
42
Age (days)
FIG 1. COMPRESSIVE STRENGTH
49
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Teck Cominco Metals Ltd.
A Review of Hard-Cem in Concrete
3 September, 2004
Figure 2: Taber Abraser test set-up
Figure 3: Hard-Cem specimen after 1000 cycles of testing in Taber Abraser
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Figure 4: Robinson-Type Floor Tester general set-up
Figure 5: Hard-Cem specimen after 500 revolutions in the Robinson-Type Floor Tester
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APPENDIX B
Product Literature for Hard-Cem
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Hard-Cem
288, 200 Rivercrest Dr. SE, Calgary, AB, T2C 2X5
Ph: (403) 720-6699 Fax: (403) 720-6609
Order Desk 1-866-212-5042
www.cementec.ca
Concrete Hardener Technology
Cementec Industries Inc. is a Member of the Pildysh Group.
What is Hard-Cem?
Hard-Cem is a specialty concrete hardener which was developed for ready-mix concrete
applications.
What does Hard-Cem do for Concrete?
Tests show that Hard-Cem increases the
abrasion resistance of concrete.
Unlike traditional surface-applied hardeners,
which are quite labour-intensive to apply,
Hard-Cem is simply added to the concrete
mix during the batching operation.
Hard-Cem has the advantage of being able
to be utilized in air-entrained concretes.
Hard-Cem Applications:
Hard-Cem is a benefit in any application requiring abrasion resistance
including industrial/commercial floors, parkades, paving, precast, etc.
How is Hard-Cem Applied?
Hard-Cem is supplied in 40 kg bags
or bulk and is simply added to the concrete
mix during the batching process.
Recommended dosage is one
40 kg bag per cubic meter of
concrete.
Please contact Cementec at (403) 720-6699
for more information.
Product performance is affected by many factors including storage, method and conditions of application and use. User testing is ESSENTIAL to determine suitability of product for intended method of
application and use. Seller's SOLE WARRANTY is that the product has been manufactured to specifications. No oral or written information or advice shall increase this warranty or create new warranties.
Seller's SOLE LIABILITY is to replace product proved defective. In no event shall Seller be liable for any consequential, indirect or other damages whether arising from negligence or otherwise.
INTRODUCING: A NEW CONCRETE ADDITIVE FOR ABRASION RESISTANCE OF
CONCRETE – COMPATIBLE WITH AIR-ENTRAINED CONCRETE
Erosion of concrete surfaces through mechanical erosion (direct or water-borne) leads to
deterioration of the concrete and exposure of steel reinforcement, necessitating frequent, costly
repair works. Conventional “hardening admixtures” used to increase abrasion resistance of
concrete, such as dry-spread surface hardeners, are unsuitable for air-entrained concrete in
exterior applications. Attempts to use other admixtures or pozzolan additives to increase concrete
hardness in external applications have, in some cases, proven costly and problematic without
attaining the desired effect.
HARD-CEM is a new, engineered product that provides concrete with significantly increased
hardness and abrasion resistance, while also providing ease of application and labor savings.
HARD-CEM is not a chemical admixture, but rather a functional filler additive and, therefore,
can be used in any concrete mix / composition with no effect on other concrete qualities such as
air entrainment. HARD-CEM is a powder material and is added to the concrete during batching
or mixing (usage: 40kg/m3 or 67.4lb/yd3), providing consistent quality and through-hardening of
the concrete with significant labor savings.
HARD-CEM is excellent for applications requiring mechanical or erosion protection such as:
• industrial floors and warehouses;
• parkades, bridges and interchanges;
• dams, dykes, spillways, stilling basins, flumes, pipes, penstocks, hydro-turbine chambers,
revetments, and breakwaters; and
• precast concrete pipe and vaults.
CEMENTEC Industries Inc. (est. 1987) is an award-winning developer, manufacturer and
distributor of engineered materials based in Calgary, Alberta, and a member of the PILDYSH
Group of Companies. HARD-CEM is available now in 40kg bags or in bulk shipment
throughout North America.
For more information, please visit our website at www.cementec.ca or contact us directly at
403-720-6699 or info@cementec.ca.
Product performance is affected by many factors including storage, method and conditions of application and use. User testing is ESSENTIAL to determine suitability of product for
intended method of application and use. Seller's SOLE WARRANTY is that the product has been manufactured to specifications. No oral or written information or advice shall increase
this warranty or create new warranties. Seller's SOLE LIABILITY is to replace product proved defective. In no event shall Seller be liable for any consequential, indirect or other
damages whether arising from negligence or otherwise.
288, 200 Rivercrest Dr. SE, Calgary, AB T2C 2X5
Ph: 403-720-6699
Fax: 403-720-6609
info@cementec.ca www.cementec.ca
A Member of the PILDYSH Group