FR2652806A1 - High performance cement grout, process for its preparation and use of this grout - Google Patents

Abstract

Cement grout of the type containing a hydraulic binder of the family of the pure or compound Portland cements, or a plaster or an anhydrite, characterised in that it contains, in combination, a fluidifying organic adjuvant based on sulphonated naphthalene (naphthalenesulphonate), or on sulphonated melamine or on purified lignosulphonate, or on hydroxylated carboxylic acid salts or on a mixture of each of the four families (adjuvant a) and a dispersion in water of a polymer of styrene-butadiene type or of vinyl type (adjuvant b).

Description

 The present invention relates to a high performance cement grout, in particular high flexural strength, to its method of production, and to the use of this grout in the production of draining concrete.

 There are a multitude of varieties of concrete according to the main qualities sought: for example a concrete will be required to be very resistant to bending, or to traction, or to be deformable, ...

 A grout is a low-viscosity blend of binders that can cure after injection or casting.

 Concrete is usually made in a single operation by introducing water into a rotating kneader, or other similar means, containing aggregates, sand and the binder.

 The most delicate point in the preparation of concrete is the water dosage; we know that it is this factor that acts the most on the spasticity of concrete its increase gives the concrete a great fluidity, which promotes its implementation (pumping, ..), but reduces its resistance. We must therefore find a compromise in the search for these two fundamental qualities.

 It is known that the separation of the preparation of the concrete in two stages (preparation of a grout, coating of the minerals with the grout) improves the better resistance results) but it is rarely practiced because of the considerable increase in the treatment time.

 A solution commonly used to find a compromise between resistance and fluidity is the use of adjuvants.

 An adjuvant is a product whose incorporation into concrete, mortar or grout causes the desired modifications of one or other of their properties, in the fresh or hardened state.

It is known that the use of a fluidizer is essential to obtain a high strength concrete; the fluidifiers are most often synthetic organic compounds based on sulfonated naphthalene, or sulfonated melamine or lignosulfonates or hydroxylated carboxylic acid salt. Their main effect is to lower the surface tension of the water which causes a considerable increase in the fluidity, with equal water content, and which increases the workability of the concrete. These adjuvants also allow, for an even fluidity measured at the cone of
Marsh, to reduce the water content or the ratio E / C <water / cement) and thus to obtain a concrete of much better resistance. It is known in fact that the proportion of water necessary for the hydration of the cement is of the order of 25 <E / C = #,, 25). Or this ratio does not generally fall below 0, , 45 for a common concrete With a thinning agent it is possible to reach E / C values of between 30 and 0.35 and thus increase the strength of the concrete.

 But these fluidifiers have a short-lived effectiveness: dispersant action generally does not last much more than one hour after mixing in the mixing water and, after this time, the fresh concrete returns to a state identical to that of the concrete without adjuvant. This disadvantage is particularly noticeable in the case of concretes delivered ready for use, by truck, with an uncertainty on the transport time.

 Adjuvants are also known whose property is to improve on the one hand the adhesiveness with the mineral surfaces and in particular with the aggregates, sands and gravels which make up the concrete and the bending strength of said hardened concretes. But these additives have the disadvantage of being coalescing, the particles gathering to form larger particles, which is to the detriment of a good performance of the final cured product.

 The behavior of the plasticizers has been improved by mixing admixtures comprising at least one of the known plasticizers and a polyacrylate. This composition is described in patent FR-A 2 521549. However, if this composition makes it possible to obtain a fluidity of the concrete maintained for a much longer period without delaying the setting, it does not make it possible to increase this fluidity to a value of given E / C ratio.

 On the other hand, the technology of draining concrete is used especially in cases where the surface must quickly evacuate the water that it receives.

 This is particularly the case in the construction of pavements, drain bodies, self-supporting filters, and in the production of non-slip surfaces.

 This technology is comparable to that known as cavernous concrete, which is obtained by mixing large aggregates of substantially uniform dimensions with a cement paste without sand or containing a small proportion of sand. The paste coats the grains and binds them at their points of contact. These concretes have a high void percentage generally greater than 2%.

 In the implementation of draining concretes the resistance-fluidity compromise is of major importance, since the quantity of water must stretch just enough to obtain a cement paste of fluid consistency ensuring only a uniform coating of the chippings and leaving spaces between chippings. and the highest possible bending tensile strength.

The present invention aims at a high performance grout: low water / binder ratio
Crapport E / C), high stable fluidity over time, high adhesiveness, and high bending strength in the cured state.

 It also aims to achieve a draining concrete, high adhesion, high mechanical performance, and high porosity to ensure immediate drainage of liquid.

 The invention relates to a cement grout of the type comprising a hydraulic binder of the family of pure or composite Portland cements, or a plaster or anhydrite, characterized in that it comprises in combination a fluidifying organic adjuvant based on naphthalene sulphone, or sulphonated melamine, or purified lignosulphonate, or hydroxy carboxylic acid salt or a mixture of each of the four families (additive a), a dispersion in water of a styrene butadiene polymer or of vinyl type (adjuvant b).

 It is further characterized in that the dispersion is added with an antifoamant of known type, the polymer being dispersed in the state of microparticles.

 In this variant the fluidifying adjuvant represents between 0.5 and 3% of the weight of the binder, and the polymer represents 2 to 8% of the weight of the binder.

The subject of the invention is also the process for producing the slurry defined above, characterized in that the constituents are mixed in one of the following two orders.
water + adjuvant (a) + binder + adjuvant <b);
water + adjuvant (a) + adjuvant (b) + binder; in order to lower the water / binder ratio first, and to improve the dispersion of the product (b) in the slurry by the fluidizing action of the adjuvant (a).

 The process is still remarkable in that the slurry is added with an antifoaming agent and is kneaded in a high turbulence mixer to improve its characteristics.

 The grout according to the invention has very high performance properties in the fresh or hardened state.

It is intended to be used in particular as a grout for the production of pre-stressing sheaths, injection pipes, consolidation pipes and existing or refurbished structures; non-cohesive granular mixture injection grout; sealing grout, high performance mortar and high performance light and heavy duty concrete, waterproof mortars and concretes, as well as porous concretes and draining concretes; and the invention also relates to the use of the grout defined above in the manufacture of a draining concrete in which the ratio of the dimension of the smallest particles to those of the largest is at most equal to 2, and characterized in that that it has the following properties
open macroporosity of 16 to 25%;
flexural tensile strength of between 3 and 6 MPa at 28 days,
The following description is given by way of example in order to better understand the invention and is in no way limiting.

The grout holds its originality of the organic products and the mode of their mixture. The hydraulic binder can be a pure Portland cement, a cement
Portland compound (CPJ - CHF - CLC) or plaster, or anhydrite.

Both synthetic adjuvants are
a) a liquefier, based on sulphonated naphthalene, or sulphonated melamine, or on purified lignosulphonate, or on the hydroxylated carboxylic acid salt or any mixture of each of these four families, provided that the bases are pure and of constant composition .

This agent is known for its fluidizing action on the water + binder mixture, that is to say on minerals for low values of the water / binder ratio (E / C).

 b) a dispersion in water of a styrene-butadiene or vinyl type polymer. The dispersion is added with an antifoamant avoiding the air entrainment effect traditionally observed with these polymers.

This combination of polymer and antifoam is known per se and is currently commercially available, for example it is possible to use such an agent, sold under the trademark Rhodopas, referenced SB 112, by the
Rhone-Poulenc Company. But it is marketed for use in a completely different technical field: paint, to improve its resistance to water, pollution, etc.

 This type of polymer is known to improve the adhesiveness of the binder to aggregates and sand, and the flexural strength of grout, mortar or hardened concrete. The dispersion acts as microbeads which, by binding to the mineral surfaces, improve adhesion between these surfaces and the binder phase.

 It has been unexpectedly shown that the action of this dispersion is modified by the presence of plasticizer. In fact, when styrene butadiene is used alone, even when dispersed in water, it tends to collect: it is coalescence.

When the two adjuvants in combination according to the invention are used, this coalescence is no longer observed.

 There is therefore an action of the adjuvant (a) on the adjuvant (b) itself, which, however, is not a mineral element.

 At an equal dosage of the dispersion b) in a mixture (water + binder), this leads to a multiplication of the contacts between the binder grains and the polymer microbeads.

 Conversely, with equal resistance, that is to say with equal numbers of contacts, the necessary dosage of polymer dispersion is very greatly reduced; according to 1 invention it is of the order of 2 to 8% by weight of the binder.

 It appears from the experiment that the a + b mixture introduced into ordinary slurry has properties very different from the simple addition of the known properties of each of adjuvants a and b taken independently.

The improvement of the dispersion of the adjuvant b by the fluidizer a is improved by mixing when the grout is made by introducing the components in one of the following two sequences
1 "- water + a + b + binder
2- water + a + binder + b
In addition, this improvement is made very important when the mixture is operated in a high turbulence mixer.

 In such a mixer, the high speed rotation causes a large rolling of the product. This rolling reduces the size of the microspheres of the adjuvant <b) in much finer microparticles whose subsequent stability and non-coalescence are provided by the presence of the plasticizer.

It emerges that when a high turbulence mixing grout is produced, with the elements being introduced into one of the two preceding sequences, the qualities of this grout are much better than those of a grout made without a high turbulence mixer, and in a traditional order that is to say in the order water + binder, + a + b (introduction of adjuvants after binder gumming)
- reduction of the water content E / C, for a given fluidity;
- reduction of the flow time (fluidity) to the measurable lower threshold of the 18 mm Marsh nozzle cone, ie 6 seconds, for a given water content; for example
fluidity of the order of 6 to 15 seconds for
mixtures whose binding water ratio (is
between 3 and 0.35;
. duration of fluidity at a value less than
25 seconds at the Marsh cone, greater than I
hour
- settling rate measured 3 hours after
mixture less than 2%;
- reduction of the amount of adjuvant b) for
an improvement in adhesiveness or
bending strength on a mortar or concrete
gives, compared to a mixture, without adjuvant
at)
- increase in compressive strengths
(Rc) for a fluidity of the grout or a
maneuverability of mortar or concrete given
- significant increase in resistance
bending (Rf) of a pure paste (hardened grout),
concrete or mortar, fluidity or
given maneuverability, compared to a mixture
traditional Rf / @@> Rf / @@
according to the tradional invention
As an example, a slurry was made from CPA HP Ranville cement;
the water / cement ratio is 8.31
the fluidizer a) selected is naphthalene sulfonate, the adjuvant b) is a styrene butadiene polymer (Rhodopas SB 112>.

the dosage is:
a = 2% by weight of the binder
b = 4% by weight of the binder;
mixing is carried out in a turbomaxer rotating at 15 rpm.

the fluidity of the grout, measured at the Marsh cone with 10 mm nozzle is
at t =: 10 seconds
at t = 1h: 12 seconds;
the decantation observed is less than 2% after 3 hours of rest.

 The compressive strength [(Rc) 28 days of the hardened paste is greater than 9 MPa, measured on a 4x4x16 cm prismatic test specimen.

 This grout is advantageously used in the production of cavernous concretes, and in particular draining concrete.

 It gives good results with a concrete comprising at least aggregates of granulometry size whose ratio of the dimension of the smallest particles to those of the largest is at most equal to 2.

 The concrete may furthermore contain a small amount of sand in a proportion not exceeding 15% by weight of the aggregates.

 Preferably the particle size is composed with dimensions of about 3 to 6 mm for the finest concretes, to 8 to 14 mm for coarse.

 This concrete possesses the following remarkable properties: its open macroporosity is at least 15 to 20%, its bending tensile strength measured at constant moment on a prism of 0.10m × 0.10m ×, 48m is between 3 and 6 MPa at 28 days, and it has a very high adhesion on the support.

According to the invention, a porous concrete is produced in the following manner
At first a slurry is carried out with the adjuvants a and b in one of the two previously described sequences and it is mixed with high turbulence in the presence of an antifoaming agent; the water content of this grout is adjusted for a fluidity of between 6 and 15 seconds at the Marsh cone.

 In parallel a composition is mixed comprising a clean rolled or crushed gravel of a narrow granulometry and a small amount of sand. (In some cases no sand at all).

 The grout is then injected into the mixers the concrete mixer or the mixer truck already filled with the mixture of gravel / sand or gravel alone. The gravel and possibly the sand are then coated with this grout.

 This product is then used as a normal concrete which can be set up either by compacting or by compacting vi-brat ion or by vibration alone.

 The proportion of grout in this concrete may be adjusted depending on whether a completely and exclusively cavernous product is desired or that it is desired to form, at the base of the spreading layer, a determined thickness of solid concrete.

This compact non-porous layer ensures a very high adhesion between the draining layer and the support on which it rests, along with the continuity between the two types of materials. It also makes it possible to constitute a flow bed for the drained water and in certain cases to avoid uncontrolled flow and infiltration.

For example, the following concrete tests were carried out
Test No. 1
CPA Cement - HP Ranville
E / C =
Fluidizing admixture of the type sold under the trademark Cimfluid: amount 2% relative to the cement, a mixture made in a turbomaxer rotating at a minimum speed of 1500 revolutions / minute.

1 / order of introduction of the elements: water + plasticizer + cement
fluidity: greater than 25 seconds at the Marsh cone (nozzle i (bmm).

 2 / introduction of adjuvant b: Rhodopas SB 112 - amount 8% fluidity: greater than 7 seconds, maintained for 1 hour.

 Decantation: 1.5% to 3 hours.

3 / realization of draining concrete
150 kg of sand - particle size 0.4
1600 kg of chippings rolled 6-10
The concrete produced uses the equivalent of 250kg / m3 of cement.

Characteristic of hardened concrete
- macroporosity 19%
- resistance (R @) on standard test specimen
10x10x40 = 4.4 to 4.9 MPa at 28 days.

Test 2
1 / one carries out a grout identical to the test n 1
2 / realization of the concrete:
- 150kg of sand - granulometry (b> 0.4
- 1300 kg of crushed gravel 10-20
Resistance R @ measured on specimen
10x10x40: 3.2 to 3.9 MPa at 28 days.

Macroporosity z 25%
The test piece shows a fastening layer approximately 1 cm thick.

Claims (9)

claims  1. Cement grout of the type comprising a hydraulic binder of the family of pure or composite Portland cements, or a plaster or anhydrite, characterized in that it comprises in combination a fluidifying organic adjuvant based on sulfonated naphthalene, or sulfonated melamine, or purified lignosulfonate, or hydroxylated carboxylic acid salt or a mixture of each of the four families (adjuvant a), a dispersion in water of a styrene butadiene or vinyl type polymer ( adjuvant b).  2. Grout according to claim 1 characterized in that the polymer dispersion comprises an antifoaming agent.  3. Grout according to claim 2 characterized in that the fluidifier represents between commat; >, 5 and 3% of the weight of the binder and the polymer 2 to 8% of the weight of the binder.  4. Process for producing the grout according to claim 1, characterized in that the constituents are mixed in one of two following orders: water + plasticizer + polymer + binder or water + plasticizer + binder + polymer, the polymer being introduced in the dispersion state in water.  5. A method of producing the grout according to claim 4 characterized in that, prior to mixing, is introduced into the dispersion an antifoaming agent and the mixture is made by violent mixing in a mixer with high turbulence.  6. Use of the grout according to any one of the preceding claims in the manufacture of a draining concrete.  7. draining concrete characterized in that it comprises at least grout-coated aggregates according to any one of claims 1 to 5 the granules being of a particle size, the ratio of the size of the smallest particles to those of the most big is at most equal to 2.  8. draining concrete according to claim 7, characterized in that the synthetic plasticizer is based at least on naphthalene sulfone, or sulfonated melamine or purified lignosulfonate, or hydroxylated carboxylic acid salt, or any mixture of each of these four families, characterized in that the tackifying and resistance improving aid is a vinyl-type or styrene-butadiene-type polymer.  9. draining concrete according to claim 7, characterized in that it further comprises sand in a maximum amount of the order of 15% by weight of the granules s.  1 (b) draining concrete according to claim 7 characterized in that the particle size is between the dimensions 3rnrn / 6mm and 8mm / 14mm.