The present invention relates to a hydraulic binder rich in calcium
oxide and/or magnesium oxide, activated by at least one compound of
phosphate type, and also to construction materials obtained from such
binders.
With the objective of decreasing the amounts of CO2 discharged into
the atmosphere, it is today increasingly sought to replace a part or all of the
Portland cement used in the manufacture of concrete and mortar with other
hydraulic binders considered to be less polluting. Hydraulic binders are thus
known in which a part or all of the Portland cement is replaced with waste
from the steel or coal industry, such as blast furnace slags or fly ash. Contrary
to Portland cement, these compounds are by nature not very hydraulic and it
is necessary to add an activator in order to dissolve them and to make them
reactive. It is known practice to use alkaline agents in large amount, or else
of which the alkalinity is high, which has the drawback of causing large
increases in pH which make such binders difficult to handle and risk causing
strong irritations. The solution proposed in application WO 2011/055063
consists of a milder alkaline activation since very small amounts of bases are
necessary to activate the system comprising finely ground slag particles.
However, this solution is not suitable if the slag is not sufficiently fine and is
not totally amorphous. Other systems propose using a combination of several
alkaline activators. Mention will be made, for example, of patent
EP 2 297 061 which uses as activator a compound of an alkali metal and a zinc
salt for a binder system containing casting sand.
The present invention provides a binder comprising at least 70% by
weight of a solid mineral compound consisting of at least one mixture of
silica, alumina and alkaline earth metal oxides, the total sum of CaO and MgO
representing at least 10% by weight of the solid mineral compound, and an
activation system comprising at least one phosphate-based compound. The
activation system used in the present invention makes it possible to render
solid mineral compounds, such as, for example, slags or fly ashes, reactive
regardless of their crystallinity. Thus, such a system makes it possible to
3
activate amorphous but also partially crystalline slags, the particle sizes of
which can range up to 5 mm.
For the purposes of the present invention, the term “activation system”
is understood to mean a system comprising one or more compounds intended
to improve and/or accelerate the setting and/or the curing of the binder, in
particular by facilitating the dissolution of its components.
The binders according to the present invention advantageously exhibit
a compressive strength which is compatible with the desired applications and
in particular which can be equivalent to that obtained with conventional
Portland cement. They also have the advantage of being compatible with the
regulations in force regarding environmental, hygiene and safety standards
since, contrary to binders based on slags or on fly ashes activated with strong
bases such as sodium hydroxide which lead to higher pH values.
Preferably, the binder according to the present invention comprises at
least 80% by weight of said mineral solid compound.
The activation system used according to the present invention
comprises at least 30% by weight of a compound which is a phosphoric acidderived
salt, the weight percentage being given relative to the total weight of
the activation system. This salt is chosen from polyphosphates of an alkali
metal such as sodium, potassium or lithium and mixtures thereof. Preferably,
the activator is an alkali metal diphosphate or triphosphate. Even more
preferentially the activator is sodium triphosphate of formula Na5P3O10. These
phosphoric acid-derived salts advantageously make it possible to improve the
mechanical strengths of the binders according to the present invention,
compared with known activation systems such as the alkaline activation
carried out with a mixture of sodium hydroxide and of silicate or such as a
mild activation as described in application WO 2011/055063.
For certain applications, it is necessary to have good strengths very
rapidly at early ages, i.e. as soon as the mortar or concrete composition
obtained using the binder has been applied. The activation system is further
improved when it comprises other constituents, in addition to the phosphoric
acid-derived salt. The activation system can therefore also comprise, in
addition to the phosphoric acid-derived salt, any constituent known to be an
4
activator for slags. Mention may be made, for example, of metal silicates,
carbonates and sulphates, of alkali metals and/or of alkaline-earth metals.
Advantageously, the activation system therefore comprises, in addition
to the phosphoric acid-derived salt, a silicate of an alkali metal chosen from
potassium, lithium and sodium and mixtures thereof. When the silicate is
present, its weight content represents between 5% and 70% by weight relative
to the total weight of the activation system.
In order to further improve the strengths at early ages, it is also
possible to add, to the activation system, a source of alkaline-earth metal and
in particular a source of calcium or of magnesium. This compound can be
chosen from lime, calcium carbonate, Portland cement, calcium aluminate
cement, calcium sulphoaluminate cement, dolomite and magnesium
hydroxide and mixtures thereof. Lime is particularly preferred. The source of
alkaline-earth metal, when it is present, represents between 5% and 70% by
weight relative to the total weight of the activation system.
Furthermore, in order to control the reactivity and the exothermicity of
the phosphoric acid-derived salts, the activation system may also comprise a
set retarder which is a salt of formula X+A- in which the cation X+ is chosen
from alkali metals, alkaline-earth metals, aluminium and the ammonium ion,
and the anion A- is chosen from acetate, citrate, formate, benzoate, tartrate,
oleate, bromide or iodide anions. Preferentially, the anion of the retarder is
an acetate and the cation is chosen from lithium, sodium, potassium,
magnesium or calcium. The amount of retarder can represent between 0.1%
and 10% by weight of the activation system. For certain applications, it is in
fact desirable to be able to increase the workability time of the systems. The
presence of a retarder chosen from the compounds mentioned above makes it
possible in particular to modify the rheology of the binder.
According to one embodiment, the binder according to the present
invention comprises an activation system which consists of a mixture of a
phosphoric acid-derived salt and of an alkali metal silicate.
According to another embodiment, the binder according to the present
invention comprises an activation system which consists of a mixture of a
phosphoric acid-derived salt and of a source of alkaline-earth metal.
5
According to another embodiment, the binder according to the present
invention comprises an activation system which consists of a mixture of a
phosphoric acid-derived salt, of an alkali metal silicate and of a source of
alkaline-earth metal. Preferentially, the activation system consists of a
phosphoric acid-derived salt, of an alkali metal silicate and of a calcium
source.
The activation system is added to the binder according to the present
invention in an amount ranging between 3% and 30% by weight, preferably
between 5% and 25% by weight, relative to the total weight of binder.
The binder according to the present invention is essentially based on a
solid mineral compound consisting of at least one mixture of silica, alumina
and alkaline-earth metal oxides, the total sum of CaO and MgO representing
at least 10% by weight of the solid mineral compound. Preferably, the total
sum of CaO and MgO represents at least 20% of the weight of the solid mineral
compound. Preferentially, said solid mineral compound is an amorphous or
crystalline slag, fly ashes and/or glass powders. The slags may be steelmaking
slags or blast furnace slags. The fly ashes are preferentially class C fly ashes.
The binder according to the invention may also comprise other types of
binders, for instance Portland cement, high-alumina cement, sulphoaluminate
cement, belite cement, cement formed of a pozzolanic mixture optionally
comprising flyash, silica fume, calcined schist, natural or calcined pozzolans,
a source of calcium sulphate, such as plaster or hemihydrate, gypsum and/or
anhydrite. When they are present, these binders represent less than 27% by
weight relative to the total weight of binder.
The binder according to the invention is advantageously used in
combination with fillers, sand such as quartz, limestone, wollastonite,
metakaolin, ground glass, rockwool, glass wool or dolomite, or else sands and
granulates derived from deconstruction concretes. It can also be used with
fillers of low density such as expanded clay, expanded perlite, aerogels,
vermiculite, expanded polystyrene, expanded glass granulates, and granulates
resulting from the recycling of worn tyres.
Other additives conferring particular properties can also be added and
be part of the composition of the binder. The content of each of the additives
6
represents less than 1% by weight of the binder. Mention will, for example, be
made of rheological agents, water-retaining agents, air-entraining agents,
thickening agents, foaming agents, agents which protect against
microorganism and/or bacterial growth, dispersing agents, pigments,
retarders, accelerators, and also other agents for improving the setting, the
curing and the stability of the products after application and in particular for
adjusting the colour, the workability, the processing or the impermeability.
The binder according to the present invention may also comprise
adjuvants such as plasticizers, for example products based on polycarboxylic
acids and preferably on polycarboxylic ethers, lignosulphonates,
polynaphthalene sulphonates, superplasticizers based on melamines,
polyacrylates and/or vinyl copolymers, typically in contents of less than or
equal to 10% by total weight of binder. It may also comprise polymers such as
cellulose ethers.
Likewise, it may comprise adjuvants such as polymers in liquid form
and/or in redispersible powder form, typically in contents of less than or
equal to 10% by total weight of binder.
Again likewise, it may comprise anti-foam or surfactant agents,
hydrophobic agents, surfactants or surface agents and/or corrosion inhibitors,
typically in contents for each of these agents of less than or equal to 1% by
total weight of binder.
A subject of the present invention is also a concrete composition or a
mortar, comprising at least one hydraulic binder as described above. Such a
composition is obtained by mixing the binder described above with
granulates, sands and/or aggregates in the presence of water. The granulates
or sands added to the binder depend in particular on the nature of the
material that it is desired to obtain. It is usually gravel, sand, dolomite and/or
limestone of various particle sizes.
Another subject of the invention relates to the construction products
obtained after hydration and curing of said mortar composition. These
construction products may be prefabricated elements, bricks, slabs, blocks or
coatings comprising at least one hydraulic binder as described above. These
materials have very satisfactory curing and very satisfactory mechanical
7
strengths. The activation system contained in the binder makes it possible in
particular to improve the short-term curing.
The binders according to the invention can be incorporated into all
types of ready-mixed mortar, for instance adhesive mortars, pointing mortars,
grouts or adhesives. They can also be used to produce mortars or concretes
for floors (floor screed or coating), or for façade mortars or internal or
external wall coatings or mineral paints such as smoothing mortars,
undercoats, single coats, mortars for rendering impermeable, and also any
type of coatings for internal or external use.
The following examples illustrate the invention without limiting the
scope thereof.
Examples
Various standardized mortar formulations were prepared. These
formulations comprise 1350 g of standard sand, 450 g of binder, and an
activation system. Various binders and activation systems were tested. The
results obtained are presented in the form of a curve, giving the compressing
strength in MPa of the samples obtained as a function of the time, expressed
in days. The amount of activator is indicated in the legends and corresponds
to the amount, as weight percentage, which is added to the blast furnace
slags and/or to the fly ashes. The amount of water introduced in order to
prepare the mortar is 225 g, which corresponds to a water/binder ratio of 0.5.
For each of the formulations, test samples of 4  4  16 cm3 are
produced according to the protocol below:
- the powders of slag and/or fly ashes and the pulverulent components
constituting the activation system are premixed with the sand for 1 min
at low speed (600 rpm);
- water is added and mixed at low speed (~600 rpm) for 30 sec, followed
by mixing at high speed (~1500 rpm) for 2 min 30 s;
- the resulting mortar is cast in a mould, and
8
- after curing, the mortar is removed from the mould and the mechanical
strength is measured (3-point bending then compression), according to
standard NF EN 196-1 (August 1995).
The compressive strength measurements are carried out for all the samples at
various times during the curing phase in order to monitor the evolution as a
function of time.
By way of comparison, identical measurements were carried out on
formulations comprising:
- 100% of Portland cement CEM I 52.5 (which comprises 95% of clinker),
- 100% of CEM III 32.5 cement which is a cement formed from a mixture
comprising 70% of blast furnace slag and 30% of clinker,
- 100% of a virtually amorphous blast furnace slag (Ecocem) or 100% of
class C fly ashes with an activation system of alkaline activation type
consisting of a mixture of sodium hydroxide NaOH (VWR) and of sodium
silicate Na2SiO3 (Metso 510 from PQ corporation), predissolved in water so as
to ensure complete dissolution of this mixture and, consequently, total
effectiveness thereof as an activator,
- 100% of an Ecocem slag activated by a mild activation system as described
in patent application WO 2011/055063 and comprising slag microparticles and
a small amount of base (composition described in Table 1 of the example).
Various slags or fly ashes were tested in the examples hereinafter. Their
respective composition and the amount of amorphous compounds contained in
each of the products are given in the table below. It will be noted that the
Carmeuse slag is a highly crystalline slag.
CARMEUSE
slag
Fos-sur-Mer
ECOCEM slag
Merit 5000 slag
(Merox)
Class C fly
ashes
SiO2 10.10 37.22 33.90 34.10
CaO 45.70 42.37 30.80 25.00
Al2O3 2.40 10.41 13.40 17.30
MgO 6.28 8.49 16.50 4.48
TiO2 0.59 0.53 2.15 1.00
Fe2O3 26.40 0.60 0.40 5.02
K2O 0.10 0.34 0.50 0.39
Na2O 0.05 <0.20 0.55 1.55
P2O5 1.61 0.02 0.01 0.51
9
MnO 4.30 0.25 0.45 0.07
SO3 0.18 - 3.70 1.36
S2- - 0.89 -
%
amorphous
content
16 99.3 96.3 ~95%
Example 1
Four formulations of binders according to the invention comprising Ecocem
slag were prepared as described above, while varying the amount of sodium
tripolyphosphate (NaTPP) used as activator. The binder 1.5 corresponds to the
comparative.
Binder 1.1: 93% by weight of Ecocem slag and 7% by weight of NaTPP.
Binder 1.2: 90% by weight of Ecocem slag and 10% by weight of NaTPP.
Binder 1.3: 88% by weight of Ecocem slag and 12% by weight of NaTPP.
Binder 1.4: 75% by weight of Ecocem slag and 25% by weight of NaTPP.
Comparative binder 1.5: 78% by weight of Ecocem slag, 11% by weight of
NaOH and 11% by weight of Na2SiO3, the sodium hydroxide and the sodium
silicate being predissolved in water before being mixed with the slag with a
water/binder ratio = 0.5.
Figure 1 represents the evolution of the compressive strength as a function of
time for these various binders.
All the binders according to the present invention have a much improved
strength after 7 to 14 days, compared with the performance levels obtained
with an alkaline activation system. It is thus possible to obtain strengths of
greater than 40 MPa after 28 days.
Example 2
Two formulations of binders according to the invention comprising Carmeuse
slag, therefore highly crystalline and known to be difficult to activate, were
prepared as described above, while varying the amount of sodium
10
tripolyphosphate (NaTPP, VWR) used as activator. The binder 2.3 corresponds
to the comparative.
Binder 2.1: 75% by weight of Carmeuse slag and 25% by weight of NaTPP.
Binder 2.2: 88% by weight of Carmeuse slag and 12% by weight of NaTPP.
Comparative binder 2.3: 78% by weight of Carmeuse slag, 11% by weight of
NaOH and 11% by weight of Na2SiO3, the sodium hydroxide and the sodium
silicate being predissolved in water before being mixed with the slag with a
water/binder ratio = 0.5.
Figure 2 represents the evolution of the compressive strength as a function of
time for these various binders.
The binder 2.3 comprising the Carmeuse slag and the conventional alkaline
activation system does not bring about short-time setting and no strength is
observed before 7 days.
The binder according to the invention makes it possible to improve the
strength right from an early age (more than 6 MPa at 3 days for a binder
comprising 25% by weight of sodium tripolyphosphate).
Example 3
A formulation of binder according to the present invention with another type
of slag was prepared.
Binder 3.1: 88% by weight of Merit slag and 12% by weight of NaTPP.
Comparative binder 3.2: 78% by weight of Merit slag, 11% by weight of NaOH
and 11% by weight of Na2SiO3, the sodium hydroxide and the sodium silicate
being predissolved in water before being mixed with the slag with a
water/binder ratio = 0.5.
Figure 3 represents the evolution of the compressive strength as a function of
time for these various binders.
The binder according to the present invention exhibits improved strengths
compared with those obtained with an alkaline activation system.
11
Example 4
Two formulations of binder based on class C fly ashes according to the present
invention were prepared.
Binder 4.1: 75% by weight of class C fly ash and 25% by weight of NaTPP.
Binder 4.2: 88% by weight of class C fly ash and 12% by weight of NaTPP.
Comparative binder 4.3: 78% by weight of Merit slag, 11% by weight of NaOH
and 11% by weight of Na2SiO3, the sodium hydroxide and the sodium silicate
being predissolved in water before being mixed with the slag with a
water/binder ratio = 0.5.
Figure 4 represents the evolution of the compressive strength as a function of
time for these various binders.
The binders according to the present invention again exhibit much improved
strengths compared with those obtained with an alkaline activation system.
Example 5
Two formulations of binders according to the present invention were
prepared, with different activation systems.
Binder 5.1: 86% by weight of Ecocem slag, 10% by weight of NaTPP and 4% by
weight of sodium silicate (Metso 510, PQ corporation).
Binder 5.2: 84% by weight of Ecocem slag, 10% by weight of NaTPP, 4% by
weight of sodium silicate and 2% by weight of lime (VWR).
These binders are compared to a binder of CEM I 52.5 type (comparative
binder 5.3) and to a binder of CEM III 32.5 type containing at least 70% of
blast furnace slag (comparative binder 5.4). Figure 5 represents the evolution
of the compressive strength as a function of time for these various binders.
The compressive strengths obtained with the binders according to the present
invention are entirely comparable to those which are obtained with a binder
of CEM I type and are higher after 7 days for the binder 5.2.
Example 6
12
Two formulations of binders according to the present invention were prepared
and are compared to a binder formulation in which the activation system is of
“mild alkaline” type as described in application WO 2011/055063.
Binder 6.1: 84% by weight of Ecocem slag, 10% by weight of NaTPP, 4% by
weight of sodium silicate and 2% by weight of lime (VWR).
Binder 6.2: 89% by weight of Ecocem slag, 4.5% of NaTPP, 4.5% by weight of
sodium silicate and 2% by weight of lime.
Comparative binder 6.3: 80% by weight of Ecocem slag and 20% by weight of a
mixture of activators which includes in particular slag microparticles, as
described in WO 2011/055063.
Figure 6 represents the evolution of the compressive strength as a function of
time for these various binders.
The compressive strengths of the binders according to the present invention
are much improved compared with a binder for which the activation is
obtained with slag microparticles, in the presence of a small amount of base.
It is also noted, when comparing the strengths of the binders 6.1, 6.2 and 6.3,
that the activation system comprising lime makes it possible to improve the
mechanical properties at an early age. By comparing the strengths of the
binders 6.2 and 6.3, it is noted that, even at a reduced amount of activator,
the mechanical properties remain higher than the mild activation system
which includes a mixture of activators, in particular slag microparticles.
Example 7
The following formulations were prepared:
Binder 6.1: 84% by weight of Ecocem slag, 10% by weight of NaTPP, 4% by
weight of sodium silicate and 2% by weight of lime (VWR).
Binder 7.1: 83% by weight of Ecocem slag, 10% by weight of NaTPP, 4% by
weight of sodium silicate, 2% by weight of lime (VWR) and 1% of potassium
acetate.
Binder 7.2: 82% by weight of Ecocem slag, 10% by weight of NaTPP, 4% by
weight of sodium silicate, 2% by weight of lime (VWR) and 2% of potassium
acetate.
13
Setting time tests were carried out on the basis of the sinking of a Vicat
needle into the mortar according to standard NF EN 196-3. The measurement
of the evolution of the degree of sinking is characteristic of the evolution of
the curing and of the setting of the material.
Figure 7 represents the degree of sinking of the Vicat needle as a function of
time. The various curves represented in this figure show that the addition of
potassium acetate delays the setting of the binder. The greater the amount of
retarder added, the greater the delay in setting.
Spreading tests consisting in causing the mortar to spread under its own
weight after raising a metal cone containing the mortar were carried out, in
accordance with standard EN1015-3 which describes the determination of
consistence of a fresh mortar paste with a flow table.
The results obtained are represented in Figure 8 which shows that the
addition of potassium acetate increases the spreading of the mortar, all the
more so the higher the amount of retarder in the formulation.

WE CLAIM :
1. Hydraulic binder characterized in that it comprises:
- at least 70% by weight of a solid mineral compound consisting of at
least one mixture of silica, alumina and alkaline-earth metal oxides, the total
sum of CaO and MgO representing at least 10% by weight of the solid mineral
compound, and
- an activation system of which at least 30% by weight is a phosphoric
acid-derived salt.
2. Binder according to the preceding claim, characterized in that the solid
mineral compound comprises at least 20% by weight of CaO and/or MgO.
3. Binder according to either of the preceding claims, characterized in
that the solid mineral compound is chosen from amorphous or crystalline
slags, fly ashes and/or glass powders.
4. Binder according to one of the preceding claims, characterized in that
the solid mineral compound is chosen from steelmaking slags, blast furnace
slags and class C fly ashes.
5. Binder according to one of the preceding claims, characterized in that
said salt is chosen from polyphosphates of an alkali metal chosen from
sodium, potassium or lithium and mixtures thereof.
6. Binder according to the claim 5, characterized in that said salt is a
triphosphate or a diphosphate of an alkali metal.
7. Binder according to one of the preceding claims, characterized in that
the activation system comprises, in addition to the phosphoric acid-derived
salt, a silicate of an alkali metal chosen from potassium, lithium and/or
sodium, in an amount ranging from 5% to 70% by weight relative to the total
weight of the activation system.
8. Binder according to one of the preceding claims, characterized in that
the activation system also comprises a source of an alkaline-earth metal,
chosen from Portland cements, calcium aluminate cements, calcium
sulphoaluminate cements, lime, calcium carbonate, dolomite and magnesium
15
hydroxide, and mixtures thereof in an amount ranging from 5% to 70% by
weight relative to the total weight of the activation system.
9. Binder according to the claim 8, characterized in that the source of
alkaline-earth metal is preferably lime.
10. Binder according to one of the preceding claims, characterized in that
the activation system consists of a mixture of a phosphoric acid-derived salt
and of an alkali metal silicate.
11. Binder according to one of Claims 1 to 9, characterized in that the
activation system consists of a mixture of a phosphoric acid-derived salt and
of a source of alkaline-earth metal.
12. Binder according to one of Claims 1 to 9, characterized in that the
activation system consists of a mixture of a phosphoric acid-derived salt, of an
alkali metal silicate and of a source of alkaline-earth metal, preferably a
calcium source.
13. Binder according to one of the preceding claims, characterized in that
the activation system comprises between 0.1% and 10% by weight, relative to
its total weight, of a retarder of formula X+A- in which the cation X+ is chosen
from alkali metals, alkaline-earth metals, aluminium and the ammonium ion,
and the anion A- is chosen from acetate, citrate, formate, benzoate, tartrate,
oleate, bromide or iodide anions.
14. Binder according to one of the preceding claims, characterized in that
the activation system represents between 3% and 30% of the total weight of
the binder, preferably between 5% and 25% of the total weight of the binder.
15. Binder according to one of the preceding claims, characterized in that
it also comprises, in an amount of less than 27% by weight relative to the total
weight of binder, Portland cement, high-alumina cement, sulphoaluminate
cement, belite cement, cement formed of a pozzolanic mixture, silica fume,
calcined schist, natural or calcined pozzolans, a source of calcium sulphate,
such as plaster or hemihydrate, gypsum and/or anhydrite.
16. Concrete or mortar composition, characterized in that it is obtained by
mixing granulates, sands and/or aggregates with at least one binder according
to one of claims 1 to 15 in the presence of water.
16
17. Construction products such as adhesive mortars, pointing mortars,
grouts, adhesives, screeds, floor coating, façade mortars, internal or external
wall coatings, mineral paints, smoothing mortars, undercoats, single coats,
and mortars for rendering impermeable, obtained after hydration and curing
of a concrete or mortar composition according to the preceding claim.