Surface retarder which may be removed without liquid
The present invention relates to a useful emulsion in particular as a concrete surface retarder
which may be removed without liquid.
A surface retarder gives the possibility of delaying hydration of the cement at the non-formed
surface of a concrete. After the usual setting time, the cement matrix with retarded surface
setting may be removed by washing, which gives the possibility of making the granules
apparent and of obtaining particular sought esthetical effects.
Formulating a surface retarder as an aqueous solution of a setting retarder is known.
In order to protect the surface against bad weather during the setting, suspending the setting
retarder in a resin solution with a solvent is moreover known. Surface retarders in a solvent
phase however release VOCs (Volatile Organic Compounds) which are harmful for the user
and the environment.
In order to. avoid the problems related to the presence of solvents, document EP1526120
proposes a surface retarder in the form of a suspension of a setting retarder in a vegetable
oil. These formulations with the retarded cement form fat crusts at the surface which are very
difficult to remove after 24 hrs. These formulations then impose strict observance of the
application time from 8 to 24 hrs, which in practice poses planning difficulties in the
organization of the building site.
Further, all these formulations have a common major problem insofar that they require
removal by washing with overpressurized water, typically under 100-150 bars. This method
generates significant amounts (typically >I m3 for 100 m2) of strongly alkaline water (pH >12)
and highly loaded with suspended materials (SM > 100glI). Discarding these waters pose
problems of pollution and may moreover cause clogging of waste water collection networks
because of the re-hardening over time of the removed cement matrix.
The goal of the present invention was then to propose a surface retarder formulation which
does not have the mentioned drawbacks. In particular, it was sought to propose a surface
retarder formulation which ensures rapid and efficient protection of the surface and which
avoids the problems posed by the washing waters.
2
This goal is achieved according to the invention with a formulation as an emulsion
which breaks upon contact with cement concrete in the fresh condition and which may be
removed during a period exceeding 24 hrs.
The formulation of the emulsion according to the invention is derived from that of roadwork
bitumen emulsions in which the molteh bitumen is emulsified with an acid aqueous solution
and added with a non-quaternary amine surfactant. The emulsion is stable and may be
sprayed on the roads. However, upon contact with ground including alkaline gravel or by
adding limestone or Portland cement, the non-quaternary amine surfactant, protonated in an
acid medium, precipitates in an alkaline medium by deprotonation, thus causing the
immediate breaking of the emulsion.
In bitumen emulsions, the nature of the acid is of no importance and mineral acids such as
hydrochloric acid are generally used. In the emulsion according to the invention in contrast,
the acid is a specific constituent since it further provides a second function. Indeed, in
addition to ensuring solubilization of the non-quaternary amine surfactant by lowering the pH
of the aqueous phase, it acts as a retarder for the setting of the hydraulic composition.
Also, according to a first aspect, the emulsion according to the invention consists of an oily
phase dispersed in an aqueous phase which comprises a non-quaternary amine surfactant
and an acid with a set-retarding effect.
By the term of << acid with a set-retarding effect )) is meant an acid which has the effect, when
it is added to a hydraulic composition, of delaying its hardening by hydraulic setting as
compared with the same hydraulic composition without such an agent.
In the present discussion by the term of << hydraulic composition )) are meant compositions
hardening as a result of hydration, and in particular compositions based on Portland cement
like concrete and mortar. Hydraulic compositions which may include esthetically attractive
granules such as gravels of the quartz, marble or granite type are particularly targeted.
The acid with a set-retarding effect preferably has a pKA comprised between 2 and 5.
Preferably the acid with a set-retarding effect is a carboxylic or hydroxycarboxylic acid. The
carboxylic or hydrocarboxylic acid may include a saturated or unsaturated carbon chain and
3
have one, two or three carboxylic groups as well as one, two, three hydroxyl groups or
more, if necessary.
The acid with a set-retarding effect may also be present in the emulsion as a corresponding
5 salt, notably of sodium, potassium or calcium.
The acid with a set-retarding effect may notably be selected from the group consisting in
acetic acid, gluconic acid, citric acid, tartaric acid, malic acid and salts and mixtures thereof.
Citric acid, tartaric acid and malic acid and salts and mixtures thereof are preferred.
10
The dosage of the acid with a set-retarding effect in the emulsion according to the invention
may be selected according to the contemplated application. Indeed, for a given acid, a higher
concentration will give the possibility of obtaining a more extensive deactivating effect. Most
often, the content of the acid with the retarding effect will be comprised between 1 and 20%,
15 preferably 1 to 15% by weight of the emulsion.
The emulsion according to the invention moreover contains a non-quaternary amine
surfactant as an emulsifier. A surfactant has an amphiphilic structure which gives its
particular affinity for interfaces of the oillwater type. The rather hydrophilic or hydrophobic
20 nature of a surfactant is often expressed by the hydrophilicllipophilic balance (HLB). The
non-quaternary amine surfactant preferably has an HLB index comprised in the range from 2
to 18 and more particular from 2 to 8.
Non-quaternary amines may be protonated in an acid medium, thereby forming ammonium
groups with a positive charge. However, when the pH of the medium becomes alkaline in
25 contact with the hydraulic composition, the surfactant loses its charge and precipitates,
leading to the breaking of the emulsion.
Therefore, a primary, secondary or tertiary amine and most particularly a primary amine will
be selected as an emulsifier. The amine may optionally be alkoxylated, notably ethoxylated,
or not.
30 The non-quaternary amine surfactant is preferably an amine bearing from 1 to 3 carbon
chains each including at least 8 carbon atoms. Advantageously, this is diamine, and in
particular a diamine of the following formula:
4
wherein R is a saturated or unsaturated, aliphatic or aromatic, linear or branched
carbon chain including 8 to 22 carbon atoms, and preferably 12 to 18 carbon atoms and n is
an integer comprised between 1 and 8 and preferably from 2 to 4.
5 Amines derived from fats of vegetable or animal origin are economical and easy to access
and consequently of particular interest. The non-quaternary amine surfactant may in
particular be selected from the group consisting in tallow, stearin, olein, coprah oil, palm oil,
rapeseed oil, erucic rapeseed oil or soya bean oil diamine.
10 The emulsion according to the invention preferably comprises 0.01 to 10% and in particular
0.01 to 5% by weight of a non-quaternary amine surfactant.
The emulsion according to the invention may also contain one or more sugars. The presence
of sugar in the emulsion allows an increase in the action depths of the surface retarder.
Thus, an emulsion according to the invention formulated for exposing at the surface granules
15 with a larger size, will preferably further comprise a sugar.
By the term of << sugar )) in the context of the present invention, is meant carbohydrates such
as glucose, dextrose, fructose, galactose, saccharose, maltose, lactose and mannose and
mixtures thereof. From among these sugars, dextrose is preferred.
The emulsion according to the invention preferably comprises 0 to 20% and in particular 2 to
20 10% by weight of sugar.
By the term of << oily phase >) within the scope of this document, is meant a hydrophobic
non-aqueous phase, non-miscible with water and liquid at room temperature.
25 The oily phase may include fats of vegetable, animal or mineral origins, which may be liquid
at room temperature or not. However, when they are not liquid at room temperature, the
emulsion is preferably prepared under hot conditions, as described later on. The emulsion
according to the invention is preferably a non-bituminous emulsion. Advantageously, it
therefore does not include any naphthenic or aromatic hydrocarbon. However, it may contain
30 aliphatic mineral oils. Moreover, it is advantageously without any curing product of the acrylic
polymer or wax type.
5
Among the large variety of fats which may be contemplated, mention may in particular be
made of vegetable oils selected from rapeseed oil, palm oil, coprah oil, castor oil, groundnut
oil, grape pip oil, maize oil, canola oil, flax oil, coconut oil, soya bean oil and mixtures thereof.
5 ' The animal oils may be in particular selected from tallow, wool oil, lard oil, herring oil, cod
liver oil, sardine oil, fish oil and lanoline oil and mixtures thereof.
The mineral oils in particular include fractions including on average 18 to 22 carbon atoms,
notably clear mineral oil.
10
The amount of oily phase in the emulsion according to the invention may widely vary.
Generally, the emulsion comprises 5 to 50% by weight, preferably 10 to 40% by weight of
oily phase and 50 to 95%, preferably 60 to 90% by weight of aqueous phase.
15 Advantageously, the emulsion is stable during storage. In order to facilitate the application,
for example by spraying, it preferably has a low flow viscosity for example comprised
between 10 and 50 s (flow time of an AFNOR No.4 cut).
[Method for preparing the emulsion]
20 According to a second aspect, the invention relates to a method for preparing an emulsion as
described above.
The emulsion according to the invention is easy to prepare with known methods as such and
does not require any specific piece of equipment. In particular, it is accessible through a
25 method comprising the steps of:
(i) preparing the aqueous phase comprising the set-retarding acid, the non-quaternary
amine surfactant, and if necessary the other adjuvants;
(ii) preparing the oily phase; and
(iii) mixing both phases in a suitable device until an emulsion is obtained.
30
As mentioned above, when one or several constituents of the oily phase are solid at room
temperature, it is preferable to heat them up in order to ensure a homogeneous mixture and
in particular a homogeneous distribution of the non-quaternary amine surfactant. In this case,
it is recommended to also heat up the aqueous phase to a neighboring temperature.
6
The aqueous phase will comprise one or several set-retarding acids as well as one or
several sugars if necessary. The aqueous phase may also contain other customary
adjuvants such as anti-foam agents, thickeners, coloring agents and opacifiers. It may
moreover also contain dispersants and petroleum resins, notably with view to improving the
5 curing performances.
A device suitable for carrying out step (iii) of the method described above is for example a
mixer of the emulsifier type.
10 A storagelstable homogeneous emulsion is obtained with low viscosity and consequently
easily sprayable onto the surface to be retarded.
[Method for use of the emulsion]
As mentioned above, the emulsion according to the invention is particularly useful for surface
15 retarding of hydraulic compositions, notably concrete.
Also, according to a third aspect, the invention is directed to a method for surface retarding of
a hydraulic composition, comprising the steps:
(a) shaping the hydraulic composition;
(b) applying on the surface of the hydraulic composition, the emulsion according to
the invention which by breaking releases the oily phase; and
(c) after hardening of the hydraulic composition, removing the film formed with the
non-hardened hydraulic composition surface layer.
25 Advantageously, step (a) is carried out by casting. The concrete to be retarded may also be
set into place by floating, and if necessary by vibration.
The step (b) for application onto the surface of the hydraulic composition is easily carried out
by spraying.
30
Surprisingly, the emulsion is efficient at the same dosage as a conventional formulation.
Preferably, the application of the emulsion is efficient when it is achieved in an amount from
100 to 400 gl m2 and preferably from 150 to 250 gl m2.
7
In contact with the fresh hydraulic composition, the emulsion according to the
invention instantaneously breaks in order to form a continuous water-repellent protective
layer while the active materials, notably the setting retarder, diffuses into the surface layer of
the hydraulic composition for generating the setting delay therein.
After 12 to 24 hours of hardening of the bulk of the hydraulic composition, the surface with
retarded setting has a dry aspect. It is then possible to expose the granules by removing the
formed film and the surface layer of the hydraulic composition. This step may be carried out
as customarily by washing with a water jet.
However, one of the main advantages of the emulsion according to the invention is the fact
that it may be removed under dry conditions, i.e. without using water, for up to 96 hours,
unlike traditional retarders which are very difficult to remove after 24 hours. Also, according
to a preferred embodiment of the method, step (c) is carried out under dry conditions, for
example with brushing, notably by means of a rotary brush. Advantageously, the residues
are simultaneously sucked up by means of a suction device coupled with the brush.
It is possible to easily get rid of the surface layer including the retarded cement and the
emulsion according to the invention from the surface and a surface is obtained which shows
the granules in order to lead to the sought esthetical aspect.
Without intending to be bound by a particular theory, it is assumed ihat the surprising effects
are due to the formation of an aqueous film superposed with an oily film upon breaking of the
emulsion in contact with the surface. Because of its particular affinity, the aqueous phase
forms an aqueous film on the surface of the hydraulic composition while the oily phase forms
an oily film positioned above the aqueous film.
Unlike conventional formulations, these films may be very homogeneous, or even continuous
by the particular breaking mechanism of the emulsion. The emulsion according to the
invention then gives the possibility of obtaining a combination of specific effects in that the
aqueous phase ensures homogeneous diffusion of the setting retarder in the surface layers
of the hydraulic composition and at the same time prevents penetration of the oily phase into
the hydraulic composition and the formation of fat crusts. On the other hand, the oily film
ensures by its curing effect, effjcient protection of the surface against evaporation and bad
weather and thus prevents dryirfg of the concrete.
8
Thus, the emulsion according to the invention gives the possibility of obtaining the formation
of a friable very homogeneous surface which may be removed under dry conditions for an
extended time, ranging up to 96 hours. Its application may then be carried out under very
diversg circumstances, including at the end of the week, without requiring specific follow-up.
5
[Usel
As mentioned earlier, the described emulsion is particularly useful as a surface retarder of
hydraulic compositions, notably due to the fact that it may be removed under dry conditions,
for example by brushing.
10
Also, according to a last aspect, the invention is directed to the use of an emulsion described
for surface retarding of hydraulic compositions, notably of concretes.
Use may be made in particular by application onto the surface of the freshly shaped
15 hydraulic composition, as explained earlier.
The invention will be described in more detail in the following examples, given as a pure
illustration.
20 EXAMPLES
EXAMPLE 1
In a suitable container with a capacity of 150 L and equipped with heating and stirring
means, 68.9 kg of water are introduced and heated to 50°C and then 7.5 kg of citric acid are
introduced with stirring. Once the acid has dissolved, 2.4 kg of tallow diamine heated up
25 beforehand to the same temperature are introduced, while ensuring vigorous mixing. To the
thereby obtained mixture, are added the adjuvants, i.e. 1.6 kg of an anti-foam agent, 1.6 kg
of a thickener and 3 kg of an opacifiying pigment.
To the thereby prepared aqueous phase, the oily phase is added, consisting of 8.5 kg of wool
30 fat and 6.5 kg of clear mineral oil heated beforehand to a temperature of 50°C and vigorous
mixing is continued, until a fine emulsion is obtained.
After cooling, a storage-stable emulsion with a milky white aspect, with a viscosity of 18
seconds on an AFNOR'No.4 Cut. Table 1 below recalls the composition of the prepared
35 emulsion.
9 a Table 1: Composition of the emulsion
The obtained emulsion was sprayed, as such, on a fresh concrete surface of a composition
given in Table 2 below with a dosage of 200 glm2. After a few minutes, the formation of a
5 water-repellent protective film which rapidly dries, is observed.
Constituent
Aqueous phase :
Water
Citric acid
Anti-foam agent
Thickener
Opacifying pigment
Fat tallow diamine
Oily phase:
Wool fat
Clear mineral oil
Total
After 24 hours, the concrete had set in depth and the surface was dry but friable. The film
Amount [kg]
68.90
7.50
1.60
1.60
3.00
2.40
8.50
6.50
100.00
and the surface layer of the concrete were easily removed by means of a brush equipped
with a suction device (Mayfacturer Eureka) for exposing the underlying granules.
10
The same test was conducted again after 96 hours outdoors in dry weather and at a
temperature of 25 "C during the day and 15°C during the night, with identical results.
Like conventional surface retarders, the emulsion according to the invention may be supplied
15 in several hollow depths by acting on the formulation of the setting retardant system and
adding one or several sugats if necessary.
10
a Table 2: Composition of the concrete
The curing effect obtained with the emulsion according to the example was evaluated as
compared with a conventional formulation in an aqueous phase and in a phase with a
5 solvent.
Constituant
CEM I 52.5NSPLC
Gravel 611 0 Lampourdier
Sand 014 Bernieres
CHRYSO B Air GI00
CHRYSOB Plast CER
Water
Total
For this purpose, a curing test was carried out on a hydraulic composition of the self-leveling
covering (SLC) type according to the operating conditions of the NF P 18-370 standard with
a retarder dosage of 200 glm2.
10
The results are summarized in Table 3 below. It is seen that, everything being moreover
comparable, the formulation as an emulsion according to the invention gives the possibility of
obtaining a highly satisfactory curing effect without using any solvents.
Amount [kglm?
330
1290
630
0.05%
0.35%
180
2432.8
15 Table 3: Curing effect
The emulsion according to the present invention, by means of its immediate breaking by
simple contact with the fresh hydraulic composition, does not emit any VOCs, ensures a
good curing effect on the concrete and leaves a dry and non-muddy surface. Moreover, the
20 emulsion according to the invention may be removed under dry conditions and therefore
does not generate any abundant, loaded and polluted washing waters. Finally, the emulsion
according to the invention may be removed for up to 96 hours after application, which notably
facilitates its implementation.
Retarder formulation
Example 1
Formulation in an aqueous phase
Formulation in a phase with solvent(s)
Protection coefficient [%I
After 6 hrs
60
0
91
After 24hrs
42
0
69

1. An emulsion consisting of an oily phase dispersed in an aqueous phase, comprising a
non-quaternary amine surfactant and an acid with a set-retarding effect of hydraulic
compositions, such as concrete or mortar, characterized in that the non-quaternary amine
surfactant is a diamine of the following formula:
wherein R is a saturated or unsaturated, aliphatic or aromatic, linear or branched carbon
chain including 8 to 22 carbon atoms, and preferably 12 to 18 carbon atoms and n is an
integer comprised between 1 and 8 and preferably from 2 to 4; and in that the emulsion
comprises 5 to 40% by weight of oily phase.
15
2. The emulsion according to claim 1, wherein the acid with a set-retarding effect is a
carboxylic or hydroxycarboxylic acid.
I 3. The emulsion according to claim 1 or 2, wherein the acid with a set-retarding effect is I
20 selected from the group consisting in acetic acid, gluconic acid, citric acid, tartaric acid,
malic acid, salts and mixtures thereof.
4. The emulsion according to one of claims 1 to 3, wherein the non-quaternary amine
surfactant is a compound with an amine function substituted with one 40 three carbon
25 chains each with at least 8 carbon atoms.
5. The emulsion according to one of claims 1 to 4, further comprising a sugar.
6. The emulsion according to one of claims 1 to 5, wherein the sugar is selected from the
30 group consisting in glucose, dextrose, fructose, galactose, saccharose, maltose, lactose
and mannose and mixtures thereof.
7. The emulsion according to one of claims 1 to 5, having a flow viscosity comprised
between 10 and 50 s (flow time of an AFNOR No. 4 Cut).
a 8. A method for preparing an emulsion according to one of claims 1 to 6, comprising the
steps:
(i) preparing the oily phase comprising the non-quaternary amine surfactant;
5 (ii) preparing the aqueous phase comprising the set-retarding acid; and
(iii) mixing both phases in a suitable device until an emulsion is obtained.
9. A method for surface retarding of a hydraulic composition, comprising the steps:
(a) shaping the hydraulic composition;
10 (b) applying onto the surface of the hydraulic composition, the emulsion according
to one of claims 1 to 9, which by breaking releases the oily phase; and
(c) after hardening of the hydraulic composition, removing the film formed with the
non-hardened hydraulic composition surface layer
15 10. The retarding method according to claim 9, wherein step (a) is carried out by casting.
11. The retarding method according to claim 9 or 10, wherein step (b) is carried out by
spraying.
20 12. The retarding method according to one of claims 9 to 11, wherein step (c) is carried
out under dry conditions.
13. The use of an emulsion according to one of claims 1 to 7 for surface retarding o!
hydraulic compositions.
25
Dated this 15/04/2013
ATTORNEY FOR THE APPLICANT[S]