Note: Descriptions are shown in the official language in which they were submitted.
CA 0210722~ 1998-02-11
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Process for Producing Improved Concrete Pavement
Having Water Permeabllity
The present invention relates to a process for producing
an improved concrete pavement having water permeability.
The harmful effects of the growth of cites has recently
becomes noticeable in many fields One of the harmful effects
is that percolation of water downward through the soil is
interrupted by such constructions as asphalt pavement or
concrete pavement, so that underground water is rapidly
reduced, thereby subsidence of ground, inhibition of the
growth of plants or trees, change of the ecology of the
organisms in the soil, etc. is caused. Moreover, when rain
comes down in torrents in a short time, rainwater is
concentrated and flooding in a pavement area is caused even if
the total amount of the rainwater is not much. This has
become a big problem for society.
In order to avoid such disadvantages, previous
attempts have been made to develop asphalt pavement
with water permeability.
However, the prior art asphalt pavement having
water permeability has many problems, such as
insufficient water permeability and water holding
property, softening of the asphalt by
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CA 02107225 1998-02-11
sunshine which thereby blocks the voids which contribute to
the water permeability, and marked deterioration of asphalt
over the course time. Therefore, a concrete pavement
having a superior water permeability and water holding
property has also been developed, which is produced by
using cement instead of asphalt (Japanese Patent Laid-Open
(KOKAI) 59-206502 (206502/1984)).
The prior art concrete pavement having water
permeability has a problem in that solid particles such
as dust or rubbish enter the voids in the surface layer
of the pavement which contributes to the water
permeability, so the water permeability is gradually
lowered.
Another prior art, a cement concrete pavement having
water permeability and a superior appearance of the surface
produced by the natural color of the aggregate or the color
of the colored aggregate, has been developed, the pavement
being produced by shot blasting the surface of the hardened
cement concrete pav. -qt with a conventional polishing machine
which uses iron balls or sand.
However, if the shot blast is used in the treatment of
the surface of the cement concrete pavement having water
permeability, the used iron balls or sand enter the voids
which contribute to the water permeability, so that the water
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CA 02107225 1998-02-11
. . ,
permeability is lowered. Also if the iron balls are used, the
appearance is further markedly impaired by the rusting of
iron. Furthermore, when the shot blast is carried out in
rain, it LS difficult to withdraw the used iron balls and
reuse the wet iron balls, so that the efficiency of execution
is decreased. Moreover, it is impossible to treat the edges
of the pav- ~nt with the shot blast, so a uniform finished
surface can not be obt~ined.
An object of the present invention is to obviate or
mitigate the defects or drawback~ encountered in the
above-mentioned prior art.
This and other objects can be achievet according to the
present invention by providing a prc~eJ~ for producing an
im~.ov~d con~rete pavement having water permeability,
comprising the steps of
-preparing a concrete composition of
300 to 400 kg of ce rnt per 1 m' of the conc~ete
composition,
0 008 to 0.0~ parts by weight of binder per 1 part
by weight of cement,
0.3 to 0.45 parts by weight of water per 1 part by
weight of cement, of water, and
1,790 to 2,150 kg of aggregate comprising sand and
at least one of crushed stone and gravel in the ratio by
weight between 5:95 and 20:80, said crushed stone having a
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~ ".~
grain size of 2.5 to 5 mm and said gravel having a grain size
of 5 to 10 mm, per 1 m3 of the concrete composition,
-hardening the concrete composition to form a concrete
pavement having water permeability, and
-applying super high pressure water having a pressure of
1,000 to 2,500 kgf/cm' to the surface of the concrete
pavement to peel off the hardened cement mortar covering
agqregate in a surface layer of the concret- pavement.
Accordinq to the present invention, the water
permeability is not reduced but is markedly increased. rt
becomes difficult for solid particles such as dust or rubbish
to enter the voids of the surface, so that the high water
permeability r~ ~in~ for a long period of time. Furthermore,
the appearance i~ not impaired. It i5 pos~ible to easily
adjust the pressure of the super high pressure water in
accordance with the consistency of the cement paste and the
thickness of the cement mortar covering aggreqate, so that
the efficiency of execution is increased by about 50~.
Moreover, it is possible to treat the edges of the pavement.
Advantag-ously, the present invention provides a
process capable of being carried out easily and
without impairing the water permeability and
appearance in effect, produces an improved concrete
pavement which has a sufficient water
permeability over a long period of time and has a
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superior appearance of surface produced by the
natural color of the aggregate or the color of the
colored aggregate over a long period of time.
Cement which can be used in the process according to the
present invention includes Portland cement, such as normal or
high-early strength Portland cement, Portland blast furnace
cement or silica cement, preferably normal or high-early
strength Portland cement, in particular, normal Portland
cement.
The amount of cement to be used is 300 to 400 kg,
preferably 320 to 370 kg per 1 m~ of the concrete composition.
If the amount of cement is less than 300 kg, the strength of
the cement pavement is insufficient, and if the amount of
cement is more than 400 kg, the strength of the cement
pavement is increased but the water permeability is
reduced. Therefore, the amount of cement i5 defined as 300 to
400 kg per 1 m' of the concrete c~ position.
The binder has the function of increasing the water
permeability of the concrete pavement, in addition to its
known functions, such as the increase of binding strength
among aggregates, the decrease of the contraction proportion
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when the concrete composition is dried and the increasing
ease of workability due to the improvement of consistency.
The binder makes the surface of the layer of cement mortar
covering aggregate smooth, thereby the ph~n~~ onon of foaming
which occurs due to air bubbles in water when water passes
throught the voids of the concrete pavement, is suppressed.
Also, the binder leads to the forming of voids which connect
with one another in the interior of the concrete pavement,
thereby the ratio of continuous voids in the concrete
pavement is increased. --
The binder which can be used in the process according to
the present invention includes all types of binders which are
added to cement mortar in general, for example, natural or
synthetic rubber such as styrene-butadiene rubber (SBR) or
butadiene-acrylonitrile rubber (N8R), acrylic resin or epoxy
resin. The binder is usually added in an emulsion. The
binder in emulsion includes JSR TOMAC SUPER (produced by
Japan Synthetic Rubber Co. Ltd., the emulsion having a 45
solid content) which contains latex binder of the type of
styrene-butadiene rubber, or X-5142 (produced by ACR Co.
Ltd.) which contains acrylic binder. In the case where JSR
TOMAC SUPER is used, the bending strength of the concrete
pavement is increased by about 10 to 60 ~. In the case
where X-5142 is used, the bending strength of the concrete
pavement ( is increased by about 60 to 90 ~.
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The amount of the binder to be used is 0.008 to 0.04
parts by weight, preferably 0.015 to 0.03 parts by weight,
per 1 part by weight of cement. If the amount of the binder
is less than 0.008 parts by weight, the strength of the
concrete pavement is insufficient, and if the amount of
the binder is more than 0.04 parts by weight, the water
permeability becomes worse. Therefore, the amount of the
binder is defined as 0.008 to 0.04 parts by weight per 1 part
by weight of cement in the process according to the present
invention.
The amount of water to be used is 0.03 to 0.45 parts by
weight, preferably 0.35 to 0.40 parts by weight, per 1 part by
weight of cement. If the amount of water is less than 0.03
parts by weight, it is impossible to prepare a concrete
composition having a sufficient hf gcneity, and if the
amount of water is more than 0.45 parts by weight, the water
permeability is worse. Therefore, the amount of water is
defined as 0.03 to 0.45 parts by weight, per 1 part by weight
of cement.
Sand which can be used in the process according to the
present invention includes all sands which are generally used,
such as natural sand, artificial sand or screenings.
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The crushed stone which can be used in the process
according to the present invention has a grain size of 2.5 to
5 mm. The crushed stone having a grain size of 2.5 to 5 mm,
in general, means that 100% of it is capable of passing
through a sieve having 13 mm sieve openings (corresponding to
a standard sieve of JI5 (Japanese Industrial Standard) which
has 12.7 mm sieve openings), 85~ to 100~ of it can pass
through a sieve having 5 mm sieve openings (corresponding to
a standard sieve of JIS which has 4760~ m sieve openings), 0
to 25~ of it can pass through a sieve having 2.5 mm sieve
openings (corresponding to a standard sieve of JIS which has
2380~ m sieve openings), and 0 to 5~ of it can pass through a
sieve having 1.2 mm sieve openings (correspon~i~g to a
standard sieve of JIS which has 1190 ~ m sieve oF~nings). In
particular, the preferable crushed stone used according to
the present invention is that of S-5 (7 Size) of JIS.
The grav-l which can be used in the process according to
the pLes~..L invention has a grain size of 5 to 10 mm.
The ratio by weight of sand to the crushed stone and/or
the gravel is in the range between 5:95 and 20:80, preferably
10:90 and 15:85. rf the ratio of sand is less than the lower
limit, the strength of the concrete pavement is markedly
declined, and if the ratio of sand is more than the upper
limit, the water permeability becomes worse. Therefore, the
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ratio by weight of sand to the crushed stone and/or the gravel
is defined as 5:95 to 20:80.
It is possible to use a crushed stone which has a grain
size of 5 to 13 mm, in particular, the crushed stone of S-13
(6 Size) of JIS, instead of a part, preferably 10 to 30% by
weight, of the crushed stone having a grain size of 2.5 to 5
mm. If the crushed stone having a grain size of 5 to 13 mm
is used, the strength of the concrete pavement is
increased more.
The amount of aggregate which is used in the process
according to the present invention is the remainder recessary
to total up 1 m' of the concrete composition in which the
cement, the binder and water are included in the above
described amounts, respectively. The amount of aggregate is,
in general, 1,790 to 2,150 kg per 1 m3 of the concrete
composition. The amount of sand is, in general, 179 to 232
kg per 1 ml of the concrete composition, and the amount of
the crushed stone having a grain size of 2.5 to 5 mm and/or
the grav~l having a grain size of 5 to 10 mm, in general,
1,520 to 1,940 kg per 1 m' of the concrete ~: ,~,ition.
Conventional additives such as coloring agents, for
example, Indian red, chromium oxide (green), etc. are further
added to the concrete pavement according to the present
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invention.
The concrete pavement is prepared by mixing cement,
the binder, water and aggregate in the defined amounts,
respectively, preferably by first mixing water, cement and
the binder, and then adding aggregate to the mixture.
The concrete pavement is produced by hardening the
concrete composition.
The concrete
composition is, for example, kneaded in a concrete plant, the
kneaded mixture is transferred to a job site by using a truck
mixer or a dump truck, distributed, and, with an asphalt
finisher, leveled and tamped (by the up and down -v.- -~t of
a tamper and vibration of a screed). The voids, in particular,
continuous voids, in the concrete pavement are not crushed
by using the asphalt finisher, so that a concrete pavement
having a high water permeability and water holding property
can be produced. Moreover, the aggregate is not broken by
such tamping, so that a concrete pavement having a high water
permeability and strength can be produced. The tamped
concrete pavement is cured and hardened.
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The super high pressure water which is applied to the
surface of the hardened concrete construction having a water
permeability to peel off the hardened cement mortar covering
aggregate in the surface layer of the hardened concrete
pavement has a pressure of 1,000 to 2,500 gkf/cm2,
preferably 1,500 to 2,500 gkf/cm', most preferably 2,000 to
2,500 gkf/cm2, in the process according to the present
invention. If the super high pressure water having a high
presssure, for example, 2,500 kgf/cm', is applied, it is --
possible to round off jags of the aggregate. Rounding off
jags of the aggregate, the surface of the aggregate becomes
smooth while the hardened cement mortar covering aggregate is
peeled off, so that the foaming which occurs due to air
bubbles in water when water passes through the voids of the
concrete pavement is suppressed. As a result, the water
permeability is furthermore improved and it is more difficult
for solid particles such as dust or rubbish to enter the
voids, so that the water permeability is maintained over a
longer period of time.
The amount of water which is applied to the surface of
the concrete pavement is, in general, 10 to 21 l/min,
preferably 20 l/min, in a process according to the present
invention. The super high pressure water is preferably
applied to the surface in a spray by a special nozzle. An
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apparatus for providing the super high pressure water
includes, for example, Leitance Remover~ (produced by Flow
Co. Ltd.) or Jet Pack~ (produced by Flow Co. Ltd.).
The coefficient of water permeability of the improved
concrete pavement having water permeability produced
according to the present invention is 3 x 10-l to 8 x 10-
cm/sec., the ratio of voids thereof being 15 to 30%. The
compressive strength (after 4 weeks, cured in water at 20~C )
of the concrete construction having water permeability
according to the present invention is 100 to 200 kgf/m', and
the bending strength (after 4 weeks, cured in water at 20~C )
thereof is 20 to 30 kgf/m'.
The following example is used to explain the present
invention in detail, but does not limit the present invention.
Example
A concret pavement having the following formulation
per 1 m3 of the concrete composition:
Normal Portland Cement 330 kg
Binder (JSR TOMAC SUPER) 12 kg
(weight of solid in emulsion)
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Water 105 kg and
Aggregate comprising sand and
the crushed stone (7 Size) of JIS
in a ratio by weight of 10:901,970 kg
was distributed on a roadbed, and, with an asphalt finisher,
leveled and tamped by the up and down movement of a tamper
and vibration of a screed. The resultant concrete pavement
having water permeability (10 cm thick) had a coefficient of
water permeability of 3 x 10-l cm/sec. The ratio of voids
thereof was 22~, the compressive strength thereof was 135
kgf/m2, and the b~ strength thereof was 28 kgf/m'.
Then, the cement mortar covering the aggregate in the
surface layer was peeled off by applying a super high pressure
water having 2,500 kgf/cm2 in spray to the surface of the
pavement in an amount of 21 liters per min using Leitance
Remover~ . The super high pressure water was applied twice
to obtain a finished surface equal or superior to that
brought about by the conventional shot blast, and the
efficiency of execution was increased by 50%. The peeled
cement mortar was withdrawn by the method, for example,
described in Japanese Patent Laid-Open (KOKAI) 3-137310
(137310/1991).
The resultant concrete pavement had a coefficient of
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water permeability of 6 x 10-1 cm/sec. The ratio of voids
thereof was 26~.
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