Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SEALING-CURING AGENT FOR PROTECTING CONCRETE
AGAINST INITIAL DRYING, SHRINKING AND CRACKING
This invention relates to a sealing-curing agent
for protecting concrete against initial drying, shrinking
end cracking.
With hydraulic cement Al substances such as mortars
and concretes, it is inevitable that during the initial
stage of their hydraulic setting, they emit water possibly
to a point where they dry, shrink and consequently sustain
cracks. To prevent them from rapid drying during the initial
stage of hydraulic setting, therefore, there has been practiced
the so-called underwater curing, i.e. a treatment which
involves immersing them in water immediately after their
release from the molds. This practice 9 however, has its-
own limits as sociable with such factors as weight and volume.
Particularly structures built outdoors in huge dimensions
dry the underwater curing despite the fact that the treatment
would prove to be all the more necessary and important
for these structures, among all others. There has been
adopted instead a primitive measure of spraying them with
water at frequent intervals and covering them with sheets
between the spraying works.
Steam curing, a treatment which entails enormous
expenses for temporary construction and fuel, is adopted
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in some cases when the importance of the outcome of the
treatment for structures justifies the financial burden.
Despite the fact that the steam curing fails to manifest
its effect fully unless it is performed for a fairly long
time, this treatment is discontinued, not infrequently,
at a halfway point because of limited fuel or time allowance.
though the underwater curing is capable of
curbing both drying and shrinking, it causes free live,
a substance indispensable to the manifestation of strength,
to be dissolved out into water nearly completely while concretes
or mortars remain under water. This loss of free lime,
accordingly, constitutes itsel-f-a-serious-demerit for structures
which are expected to possess strength. In this respect,
the underwater curing cannot be called a perfectly ideal
treatment.
The inventors made a diligent study devoted to
the development of a way of curing perfect in all respects
and applicable particularly to huge outdoor structures
necessitating curing by all means. They consequently have
succeeded in developing an entirely novel method of curing
and an ideal curing agent. This invention provides the
method and the curing agent.
To be more specific, this invention comprises
coating the surface of a concrete structure immediately
after its placement with a resin solution possessed of
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specific properties thereby forming on the surface of the structure
a watertight layer proof against pressure, completely precluding
escape of free water from the structures and thoroughly eliminating
drying and shrinking and consequently occurrence of cracks.
According to one aspect of the present invention there
is provided a polymerized solute for incorporating with 60-70 per-
cent by weight of a petroleum-derived solvent to form a sealing-
curing composition for protecting concrete against initial drying,
shrinkage and consequently forming of cracks in the formed concrete
comprising, in proportion by weight of 12-18 percent of lanolin;
6-9 percent of zincnaphthenate; 2-5 percent of a high molecular
weight synthetic resin selected from the group consisting of a
styrenes resin, an acryl resin, a mailmen resin, an alkyd resin and
a urethane resin, and 10-20 percent of a petroleum solvent, said
solute being polymerized by application of heat at an acceptable
temperature prior to incorporation of said solute with the petrol
leum-derived solvent.
According to another aspect of the present invention
there is provided the method of protecting a formed concrete struck
lure against initial drying, shrinking and consequently forming of cracks in the formed structure and to provide a sealing and curing
of the formed structure comprising pouring the concrete to form the
desired structure, applying the above composition with 10~ of an
accelerating agent to the jet concrete surface of the formed struck
lure and permitting the treated concrete structure to be cured, said
polymer solute of said composition will penetrate and fill voids
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formed in said concrete structure during the curing thereof.
Generally, for curing to be carried out to perfection
and to the extent of manifesting its effect fully, the various
requirements enumerated below must be fulfilled as preconditions.
1. While the water contained in the structure is
vaporized and expelled out of the structure because of a temperature
difference between the ambient air and the structure, the vaporize-
lion is attended by generation of considerable pressure. Thus, the
structure should be capable of withstanding this pressure.
Unlike the principle of ordinary waterproofing, the
structure is required to offer strong resistance rather to the back
pressure (inner pressure) than to the pressure from the front side
(outer pressure).
2. Since the curing, when performed after the struck
lure has dried up, has neither significance nor effect, it should
be capable of being carried out while the structure is still in the
early stage of its wet state.
3. The curing should possess high workability enough
to provide required treatment quickly to the structure
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no matter how complicate the structure's contour may be
or how huge the structure may be and yet should be simple
enough to preclude the possibility of misperformance.
4. The curing should be capable of producing
lasting effect for at least about three months (90 days
'. 13 weeks) until the structure is stabilized materially
and chemically to a tolerable extent. Otherwise, the treatment
cannot be expected to provide perfect curing of the structure.
S. When a coat is formed on the surfs the structure,
the continuous construction work is suspended and the removal
of this coat on fulfillment of its function entails a work
of surface cleaning. This evidently means that the
construction cost is increased by the labor cost required
for this extra work and the scheduled period of construction
is lengthened by the suspension of work. The coat thus
applied to the structure should not be of a type which
requires a cleaning work.
6. The curing treatment should be capable of
producing a perfect curing effect and further waterproofing
the structure and preventing the structure from neutralization.
Then the curing ought to be truly ideal for structures
requiring permanent durability.
After many years's diligent study aimed at satisfying
all these requirements, it has now been found that their
collective satisfaction issues from providing a novel curing
agent to be described fully below. Thus, this is a literally
epochal invention capable of solving all the problems.
To be specific, this invention relates to a sealing-
curing agent for protecting concrete against initial drying,
shrinking and consequent occurrence of cracks, characterized
by having diluted with a solvent of 60 - 70% a solute formed
by mixing lanolin and a metal such as zinc naphthenate
in a ratio of 2 : 1 and further adding thereto 2 - 5 %,
based on the total of all the components used, of a synthetic
resin and 10 20%, based akin on the total, of xylol or
some other similar substance, all by weight proportions,
and polymerizing the resultant mixture under application
of heat.
Now, one typical embodiment of this invention
will be described in detail below.
Proportion
Component by weight
(1) Lanolin 12 to 18%
(2) Zinc naphthenate6 to 9%
(3) Xylol 10 to 20%
(~) Styrenes resin to 5%
(5) Kerosene 60 to 70%
A solute is formed by mixing the components
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(l), (2), (3) and (4) indicated above and polymerizing
the resultant mixture under application of heat, and the
polymerized solute is diluted with the solvent (5) indicated
above to produce the agent of this invention.
Optionally at the time of the polymerization,
about 10% of acetone, methyl-ethyl kitten or polypropylene
glycol may be added to the mixture for the purpose of accelerate
in the polymerization. With a view to precluding the
possibility of such an additive bringing about an adverse
effect upon the ambience during the application of the
agent to the structure under treatment, it has been found
advisable to optimize the polymerization by regulating
the reaction temperature and the reaction velocity instead
of incorporating the additive.
Lanolin as the component (1) in the foregoing
formulation, satisfies the requirement that this component
should combine the two functional groups, i.e. the hydrophilic
group and the oleophilic group, as evidenced by its molecular
formula, C12H2400H. For example, septennial (C6CL5OH) and
certain (Cl5H3lcoocllH33) may be used in the place of lanolin
However, these are small in production and therefore are
expensive. Thus, lanolin was adopted.
Although examples of the metal salt usable as
the component (2) of the formulation include barium sulfate
and many others, zinc naphthenate was adopted in consideration
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of its superiority in surface tension and penetrating property.
As the component (5) of the formulation, the
aforementioned solvent, kerosene, could be substituted
by xylol. Xylol, however, emits a highly offensive odor
and exhibits pungency and therefore, has a possibility
of impairing the ambience during the application of the
agent to the structure under treatment. Accordingly, it
has been found advisable to use kerosene which possess
mild properties. Although xylol and kerosene more or less
differ in dissolving power and volatility, their actual
effects upon the function of the produced agent are practically
even. In many experiments, kerosene has been shown to
excel xylol in some, if not all, respects. Hence, kerosene
was adopted.
Styrenes resin has been selected to serve as the
component (4) of the formulation. For the resin to serve
satisfactorily as the filler in the formulation, it does
not matter what physical strength it may exhibit. It has
only to fulfill the requirement that it should be insoluble
in water. Thus, acryl, mailmen alkyd and urethane resins
may be used in the place of styrenes resin.
As described above, the sealing-curing agent
of this invention for protecting a concrete structure against
initial drying and shrinking and consequent occurrence
of cracks is produced by diluting with a solvent of 60-70%
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a solute which is prepared by mixing lanolin and a metal salt
such as zinc naphthenate in a ratio of 2:1 and further
adding thereto 2 - 5%, based on the total of all the components
used, of a synthetic resin and 10 - 20%, based again on
the total, of xylol or some other similar substance, all
by weight proportions, and polymerizing the resultant mixture
under application of heat. Another words, the present
invention does not contemplate simply by coating the surface
of a structure with a solution. The solution of the present
invention has as its solution a polymer formed of a high
molecular synthetic resin, lanolin and a metal salt. This
solution, when applied to the surface of a structure in
which the free water contained as dispersed therein has
given rise to a reticularly distributed fine voids, penetrates
deeply into the structure by dint of a surface tension
of 30 dynes, a value about twice the surface tension (72
dynes) of water. With the subsequent evaporation of the
solvent, the solute of the solution remains and Bills up
these voids. The solute filling the voids 9 therefore,
is allowed to manifest high resistance (3 kg/cm = 30 meters
of water column as determined by an official test) to not
only the outer pressure but also the inner pressure (back
pressure).
The agent of the present invention is of an oily
type using a solvent of the petroleum origin. The concrete
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structure, though dry on the surface, has its interior
in a set state having about 60 of water content. The
curing treatment, therefore, must meet the requirement
it should be performed satisfactorily no matter whether
the concrete structure may be in a dry state or in a wet
state. With due consideration paid to this particular
requirement, the present invention has a hydrophilic group
as well as an olephilic group imparted to the solution.
The agent of this invention, accordingly, can be applied
directly to the wet surface of a concrete structure freshly
released from a mold. When the concrete structure happens
to be in a dry state, the agent may be applied to the surface
of the structure after the structure has been sprayed with
fresh water and brought into a state of forced wetness.
Because of the hydrophilic group contained therein, the
oily solution can be satisfactorily applied to the structure
without being repelled by the water adhering to the surface.
Further, since the agent of this invention is
a free-flowing liquid having a surface tension of 30 dynes,
it can be applied effectively by use of a brush, a sprayer
or a roller, for example. Thus, it is allowed to disperse
and penetrate evenly in the structure no matter how complicate
the structure's contour may be. The treatment is simple-
enough to preclude the possibility of misprision. The
persons who engage in the application of the agent to the
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concrete structures are not required to be skilled. Thus,
the agent of this invention enjoys very high workability,
saves labor and promises high economy.
The filler contained in the agent of this invention,
after being loaded in the voids of the concrete, offers
strong resistance to heat rays, ultraviolet rays, carbon
dioxide and carbon monoxide in the ambient air, with the
result that the concrete structure will exhibit high weather-
ability and stability. When the concrete structure enters
the stage of ample if not perfect stability on lapse of
three months (90 days 13 weeks) after the treatment, .
the curing effect of the treatment will be retained intact
within the structure for a long period of time.
When the surface of the concrete structure is
to additionally coated at a later day, since the substrate
has been thoroughly treated to repel moisture, water and
other defiling matter, there is no need for giving any
primer treatment thereto.. Moreover since the agent gives
the concrete structure a more thorough coat than an ordinary
primer, it protects the additionally applied overcoat such.
as mortar, decorative paint, resin tiles or textile wall
covering from the substrate. Thus, the agent of t-his invention
enables the overcoat to double its service life.
Since the agent of this invention is not intended
to form a coat on the surface of the concrete structure
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but is designed to penetrate deeply into the concrete structure
and fill up the voids distributed therein, it has an advantage
that the concrete structure treated therewith can be
additionally coated without requiring its surface to be
cleaned in advance of the additional coating.
Moreover, since the agent of this invention forms
a watertight layer below the surface of the concrete structure
and repels water of a pressure of up to-3 kg/cm2, it perfectly
precludes the possibility of water penetrating into the
concrete structure, coming into contact with lime contained
within the concrete structure and consequently forming
calcium hydroxide. This means that the agent all the more
increases the service life of the concrete structure by
perfectly curbing the phenomenon of neutralization which
proceeds chemically as described above and ends up in
noiseless destruction of the concrete structure. This
invention, accordingly, provides an epochal surface-coating
sealing-curing agent which ensures prolonged repression
of the quick drying otherwise liable to occur in the early
stage following the placement of concrete and warrants
perfect prevention of the occurrence of cracks due to dying
and shrinking.
