Note: Descriptions are shown in the official language in which they were submitted.
CA 02438149 2003-08-11
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ADMIXTURE TO IMPROVE CONSOLIDATION OF CEMENT
COMPOSITION WITH LOW MOISTURE CONTENT
This invention relates to a method and composition for producing
concrete articles in a very short time frame which have increased density and
strength.
By adding a powder admixture of naphthalene formaldehyde condensates to a
cement
composition, the time of vibration required for consolidation of such concrete
articles
is reduced, yet density and strength is increased.
BACKGROUND OF THE INVENTION
Concrete articles are typically prepared by pouring a cementitious
composition into a mould and agitating and pressing it. Generally, the
cementitious
composition must cure for 18 to 24 hours in the mould before it can be removed
as a
formed usable concrete article.
Conventionally, water has been added to the cementitious composition
to disperse particles of cementitious material and improve the workability of
the
composition. Unfortunately, the amount of mixing water required for
workability is
normally a great deal more than necessary for subsequent hydration and setting
of the
cementitious composition. Hollow spaces formed by evaporation of excess water
result in decreased strength of the concrete article of the finished product
and
instability of the product upon demoulding.
Additives including polycondensation products based on naphthalene
sulfonic acids have been used in cement compositions to improve workability
and
flowability with reduced water-cement ratio as low as 0.23%, but the essential
water
content comprising at Ieast 10% of material solids by weight moisture. As
observed
in U.S. Patent No. 5,798,425, the liquefying action of these additives in
cement
compositions is short Iived and can result in a decrease in workability or
slump loss.
Accordingly, there is need for a method of maleing concrete articles
from cement compositions having low water content in a short time period.
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SUMMARY OF THE INVENTION
It is an object of the invention to provide cement compositions having
a low moisture content (slump around zero) which are suitable for making
concrete
articles in a short period of time.
It is a further object of the invention to provide cement compositions
having a low moisture content (slump around zero) which can be used to prepare
concrete articles exhibiting adequate mechanical strength and stability during
manufacture and transport to point of use.
These and other objects of the invention are achieved by providing a
cement composition comprising hydraulic cement and .5 to 3% by weight of the
hydraulic cement of a naphthalene sulfonate condensate wherein the maximum
moisture content of the composition is 8% by weight. The invention also
provides a
method of making a concrete article by introducing the cement composition into
a
mould, applying pressure and vibration to the cement composition thereby
forming a
concrete article and removing the concrete article from the mould after the
short time.
DETAILED DESCRIPTION' OF THE PREFERRED EMBODIMENTS
The cement composition of the present invention is used to prepare
concrete articles which have a moisture content of 8% by weight or less,
approximately zero slump, i.e. which do not exhibit any substantial flow. The
cement
composition can be used in a dry technology process in which simultaneous
vibration
and high pressure is employed to consolidate the material in a mould. Concrete
articles made in accordance with the invention include but are not limited to
concrete
paving stones, wall blocks, tiles and the like.
The essential component of the inventive cement composition is a
powder admixture of naphthalene sulfonate formaldehyde condensates (NSFC)
which
is mixed with hydraulic cement in the amount of 0.5 to 3% by weight,
preferably 0.5
to 1.75% by weight of the hydraulic cement. Suitable NSFC materials include
Hydropalat~ D available from Cognis Coatings & Inks located in Ambler,
Pennsylvania and Lomar D available from GEO Specialty Chemicals in Harsham,
Pennsylvania.
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Any suitable hydraulic cement can be utilized in the cement
compositions of the invention. Suitable cements include Portland cement,
alumina
cement or blended cement, for example, pozzolanic cement, slag cement or other
types. A preferred cement is Portland cement of one or more of the various
types
identified as ASTM Type I to V. The hydraulic cement is present in an amount
of 6
to 15% by weight of the cement composition. The cement composition according
to
the present invention may further contain one or more additives such as
fillers, for
example, glass powder, quartz, silica and the like, color pigments and
reinforcing
fibers made of metallic, synthetic or mineral material. These additives are
present in
up to 40%~by weight of the cement composition.
The invention will be better understood with reference to the following
illustrative examples which do not limit the scope thereof.
Example 1
In a ient ei ht
Glass Aggregate 527.5
Grey Portland Cement Type I 80.0
Metamax 20.0
Recycled Glass Powder Filler 20.0
Water 41.0
Lomar D 1.4
Nylon Fibers 3.76
Pigment 2.4
The ingredients were mixed together in a mixer drum and placed into a
block machine manufactured by Zenith Corporation of Germany. Other suitable
equipment is available from Columbia Machine, Inc. and Besser Company. Metamax
is an Metakaolin admixture available from Engelhard Corporation in Iselin, New
Jersey. The glass powder filler is available from the Glass Recycling Group. A
microtrac particle size analysis of the recycled glass powder filler is shown
in Table 1.
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4
Ta Ie 1
Size (pm) 0.9 1.4 1.9 2.8 3.9 5.5 7.8 11 22 31 44 62 88 125
Percent Retained 3.5 2.4 3.3 3.7 3.7 4.3 5.8 6.3 11.7 15.5 13 13 6.8 0
The glass aggregate was obtained from a glass recycling company who
also cleaned the glass. The grading of the recycled glass is shown in Table 2.
Tab a 2
Size (gym) #4 #8 #16 #30 #50 #100 Pan
Percent Retained 0 27.6 28.3 21.1 12.1 6.7 4.2
Formed concrete blocks were produced at a rate of 1260 blocks per
minute. Concrete blocks were prepared as in Example 1 using the cement
compositions shown in Table 6 (batches 12 and 13).
The influence of the powder admixture on compressive strength was
investigated for various mixtures. The test result are shown in Table 3.
Samples
consisted of cylinders 2.8 in diameter and 2.0 in height, which were produced
in the
laboratory under conditions simulating those in commercial manufacture.
Table 3
SampleIngredients,
in
parts
by
weight
No. Glass Glass Powder Moisture Compressive
~
Cementitious
Mat.
powderAggregateAdmixt.Content, Strength,
% psi
Cement MetamaxFiller
2 0.8 0.2 0.24 5.275 0.0 7.6 2433
3 0.8 0.2 0.24 5.275 0.8 6.5 2127
4 0.8 0.2 0.24 5.275 I.0 6.9 3047
5 0.8 0.2 0.24 5.275 1.2 6.5 4056
6 0.8 0.2 0.24 5.275 1.4 6.4 3909
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The compressive strength of the concrete blocks was determined after
7 days using ASTM C6?-99a (Volume 04-OS). Sample 2 had no NSFC powder
admixture. Sample 5 exhibited the highest compressive strength.
xam I 2
Concrete specimens were prepared from cement compositions as in
Sample 5 using plasticizer additives other than NSFC. These comparative
samples
are labeled SA-50 in Table 4 herein below. The compressive strength was
measured
after 7 days using 2 inch high cylinders with a diameter of 2.8 inches.
Table 4
SampleAdmixtures, Moisture Compressive
%
by
weight
of
cementitious
mat.
No. NSFC ADVA MelmentPOZ400N Reo1000Content, Strength,
% psi
S 1.2 6.5 4056
SA 0.8 ' 6.6 3342
SB 1.0 6.6 0*
5C 1.0 6.3 4162**
SD 0.7 6.6 3643
SE 0.8 7.6 2322
SF 1.0 . 6.8 2051
SG 1.2 ' 6.S 1977
SH 1.4 6.5 1968
SI 0.8 6.6 1638
SJ 1.0 6.6 2027
SK 1.2 6.5 2296
SL 1.3 6.6 2049
SM 1.7 6.5 2717
SN 2.0 6.2 2970
50 2.6 6.2 3244
Sample
could
not
be
demoulded
Sample was sticky and difficult to demould
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6
ADVA is a plasticizes available from Grace Construction Products.
POZ 400N, refers to "Pozolith 400N", a plasticizes available from Master
Builders.
Reo 1000 refers to for "Reobuild 1000," a plasticizes available from the same
company. As can be seen from Table 4, Comparative Sample SC was sticky and
difficult to demould while Sample 5 in accordance with invention resulted in a
concrete block which was easily manufactured and had a high compressive
strength.
Exam 1e
Concrete specimens were prepared from cement compositions in
accordance with the invention as in Example 1 and are shown in Table 5 as
Samples
7-9. Concrete specimens were also prepared using Reomix 700, an admixture from
Master Builders Co., to improve the consolidation property.
Ta 1e 5
SampleAdmixtures, Moisture Compressive
% by wt.
of cement.
mat.
No. NSFC Reomix700 Content, Strength,
% psi
A 0.26 6.7 2063
B 0.5 6.5 2149
C 1.0 6.5 2129
7 0.8 6.5 2127
8 1.0 6.9 3047
9 1.2 6.5 4056
As can be seen from Table 5, Sample 7, 8 and 9 in accordance with the
invention gave comparatively superior results with respect to compressive
strength.
Example 4
Concrete paving stones were made in accordance with Example 1 from
cement compositions as shown in Table 6 using a Zenith block machine. The
compressive strength was measured after 28 days.
CA 02438149 2003-08-11
WO 02/070428 PCT/USO1/28024
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CA 02438149 2003-08-11
WO 02/070428 PCT/USO1/28024
As can be seen from Table 6 concrete paving stone prepared in accordance
with the invention, samples 11, 12 and 13, exhibited high compression
strength.
Example 5
A comparison of a paving stone commercially available and a paving stone
prepared from an admixture having NSFC in accordance with the invention is
shown in Table
7.
CA 02438149 2003-08-11
WO 02/070428 PCT/USO1/28024
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CA 02438149 2003-08-11
WO 02/070428 PCT/USO1/28024
As can be seen from Table 7, the consolidation property and compression
strength for the paving stone prepared in accordance with the invention was
superior to
commercially available paving stone.
