Hydraulic binder

Abstract

The invention relates to a hydraulic binder comprising 50 to 85% by weight of a calcium sulfate source, 5 to 35% by weight of ladle slag and 0 to 30% by weight of a pozzolanic material.

Description

Title of the invention: Hydraulic binder

[0001] The invention relates to the field of construction materials. It relates more particularly to hydraulic binders as well as to dry mortar compositions comprising said hydraulic binders.

[0002] Dry mortar compositions are generally powdered mixtures comprising a hydraulic binder and aggregates. After mixing ("mixing") with water, a paste (wet or fresh mortar) is obtained which can be shaped and then hardened to form a hardened mortar. Such mortars can have various applications: facade coatings, tile adhesives, flooring products such as screeds, jointing mortars, masonry mortars and many others.

[0003] Depending on the intended applications, dry mortar compositions must meet a large number of requirements, relating both to their ability to be implemented (spreadability, workability, workability, pumpability, rheology, etc.) and to the hardened mortar (in particular its mechanical strength, for example compressive strength).

[0004] For flooring products in particular, such as screeds, several properties are important. The spread of the fresh mortar must be high in order to obtain self-leveling properties. The mortar must also be able to harden quickly in order to reduce construction times. The compressive strength must also be high. The dimensional stability of the mortar is also important, during hardening, but also afterwards, for example if the hardened mortar comes into contact with water.

[0005] The aim of the invention is to propose a hydraulic binder suitable for obtaining mortars, in particular for flooring products, by having both self-leveling properties, rapid hardening and good dimensional stability, in particular after exposure to water.

[0006] For this purpose, the invention relates to a hydraulic binder comprising 50 to 85% by weight of a source of calcium sulfate, 5 to 35% by weight of ladle slag and 0 to 30% by weight of a pozzolanic material.

[0007] The hydraulic binder is preferably a hydraulic binder for mortar composition, in particular for obtaining soil products.

[0008] The source of calcium sulfate is preferably chosen from hemihydrate (in particular [3-hemihydrate], gypsum and anhydrite, alone or as a mixture.

[0009] A slag is a by-product of an industrial process involving the melting of a starting material, a melting intended to separate metals from an oxide phase, the latter being called "slag".

[0010] Ladle slags are steelmaking slags, resulting from the secondary metallurgy of steel. More precisely, conversion steel (from a cast iron conversion steelworks, in particular in an oxygen converter) or so-called electrical steel (from an electric steelworks, in particular by melting scrap in an arc furnace) is poured into a ladle and transferred to an installation called a "ladle furnace". Generally equipped with three graphite electrodes, the ladle furnace allows the desired shade to be achieved by additional additions and deoxidation and ensures the temperature is maintained. The homogenization of the liquid steel is ensured by gaseous stirring with argon or nitrogen. Ladle slag is the slag from the ladle furnace.

[0011] Ladle slags are distinguished by their chemical and mineralogical composition from other steelmaking slags, namely blast furnace slags and other steelmaking slags such as conversion steelmaking slags (often called "LD slags") and electric steelmaking slags. For example, blast furnace slags used in hydraulic binders are generally amorphous (glassy) because they have been "granulated", i.e. cooled abruptly by spraying. Ladle slags are also more basic than electric steelmaking slags. It should be noted, however, that ladle slags have different chemical and mineralogical compositions depending on their origin, in particular depending on the addition and deoxidation supplements used.

[0012] Due to the additional addition of lime or dolomite in the ladle, the ladle slag is very rich in lime. It is also rich in alumina.

[0013] The ladle slag preferably has a chemical composition comprising the following constituents, within the limits below expressed in weight percentages: - SiO2: 1-20%, especially 5-15%, particularly 7-12%, - CaO: 30-65%, especially 40-60%, particularly 45-55% - A12O3: 15-50%, especially 19-45%, even 20-42%, particularly 25-40%.

[0014] The ladle slag may also include magnesia (MgO), in particular in a content of between 2 and 10%, or even between 3 and 8%.

[0015] In order not to negatively impact the setting time, the iron oxide content in the ladle slag is preferably less than 10% by weight, in particular less than 5% by weight, and even less than 2% by weight.

[0016] The ladle slag is preferably crystallized to at least 30%, in particular to at least 50% or 60%, or even to at least 70% or 75% by weight. The crystallization rate can be evaluated by X-ray diffraction using the Rietveld method. The crystallization rate will depend in particular on the cooling rate of the slag, a more slowly cooled slag developing more crystalline phases.

[0017] In a particularly advantageous manner for the intended application, the ladle slag advantageously comprises at least one crystalline phase of aluminate type. calcium (in particular of type C3A and / or C12A7, the latter phase being called mayenite, or / and C4AF), in particular in a weight content of at least 10%, or even at least 15% and even at least 20%, in particular between 10 and 60%, or even between 30 and 55%.

[0018] Preferably, the ladle slag comprises both a C3A phase and a C12A7 phase, in a total weight content of at least 20%, in particular at least 30%, in particular between 35 and 60%.

[0019] The reactivity of the ladle slag is further improved if it further preferably comprises crystalline phases of calcium silicate type (in particular of C2S and / or C3S type). Preferably, the total content of crystalline phases of calcium aluminate type is however greater than the total content of crystalline phases of calcium silicate type.

[0020] Preferably, the ladle slag has a volume particle size distribution such that the D50 is less than 50 μm, preferably less than 20 μm, and in particular between 8 and 15 μm. The D50 is the size such that 50% by volume of the particles have a size less than this D50 value. The volume particle size distribution is preferably determined by laser particle size sizing (also called laser diffraction particle size sizing). This fineness of the particles makes it possible in particular to give the slag good reactivity allowing it to be used in a mortar composition and to obtain the expected properties in terms of setting time and mechanical strength. The D90 is preferably less than 100 μm, in particular less than 60 μm.

[0021] The pozzolanic material is preferably chosen from fly ash, calcined clays, silica fumes, calcined shales and natural or calcined pozzolans. The calcined clay is advantageously metakaolin. The pozzolanic material makes it possible to reduce dimensional variations of the mortar after exposure to water. Its presence is however optional.

[0022] Preferably, the total content of calcium sulfate source, ladle slag and pozzolanic material is at least 80% by weight, in particular at least 85% by weight, or even at least 90% by weight, and even at least 95% by weight. According to one embodiment, the hydraulic binder consists of the calcium sulfate source, ladle slag and pozzolanic material. According to another embodiment, the hydraulic binder consists of the calcium sulfate source and ladle slag.

[0023] Preferably, the binder comprises little or no cement. The cement content is advantageously less than 5% by weight, and preferably the cement content is zero. The cements include in particular Portland cements, belitic cements, aluminous cements, and sulfoaluminous cements. By "content in cements”, we mean the total content of cements possibly contained in the binder.

[0024] The content of calcium sulfate source is preferably between 55 and 80% by weight, in particular between 60 and 75% by weight, or even between 65 and 72% by weight.

[0025] The ladle slag content is preferably between 8 and 30% by weight, in particular between 10 and 25% by weight, or even between 15 and 22% by weight.

[0026] The content of pozzolanic material is preferably between 0 and 25% by weight, in particular between 0 and 20% by weight, or between 1 and 20% by weight, or even between 2 and 15% by weight, or even between 3 and 10% by weight. According to one embodiment, this content is zero.

[0027] All combinations between these preferred content ranges are of course possible, even if they are not all listed here for reasons of brevity. As a preferred example, the binder may advantageously comprise 55 to 80% by weight of a source of calcium sulfate, 8 to 30% by weight of ladle slag and 0 to 25% by weight of a pozzolanic material. According to another preferred example, the binder comprises 60 to 75% by weight of a source of calcium sulfate, 10 to 25% by weight of ladle slag and 0 to 20% by weight of a pozzolanic material. According to yet another preferred example, the binder comprises 60 to 75% by weight of a source of calcium sulfate, 10 to 25% by weight of ladle slag and 1 to 20% by weight of a pozzolanic material.

[0028] The invention also relates to a dry mortar composition comprising a hydraulic binder according to the invention and aggregates.

[0029] The composition is designated as dry since the majority, if not all, of these constituents are in powder form. The percentages of each of the constituents are given as mass percentages relative to the totality of the components of said composition.

[0030] The aggregates generally used in mortar compositions have a diameter of less than 8 mm, preferably less than 4 mm, or even less than 3 mm, which distinguishes mortar compositions from concrete compositions, which contain coarse aggregates. The aggregates may comprise fillers, which are finely ground inert mineral materials, generally of the calcareous or siliceous type. Preferably, the aggregates comprise sands, in particular siliceous sands and / or fillers, in particular calcareous or dolomitic fillers. The aggregates may also comprise lightweight aggregates chosen from perlite, vermiculite, expanded glass beads, expanded polystyrene beads, cenospheres, expanded silicates, aerogels and mixtures thereof.

[0031] The total content of aggregates is preferably between 40 and 90%, in particular between 50 and 80%, or even between 60 and 75% by weight relative to the weight of the composition. dry mortar composition. The hydraulic binder content is preferably between 10 and 55%, in particular between 20 and 50%, or even between 25 and 38% by weight relative to the weight of dry mortar composition. The hydraulic binder according to the invention is preferably the only hydraulic binder included in the dry mortar composition. The above-mentioned contents therefore apply to the hydraulic binder according to the invention.

[0032] The dry mortar composition may also comprise one or more additives, in particular chosen from rheological agents, plasticizing or superplasticizing agents, water-retaining agents, air-entraining agents, thickening agents, biocidal protective agents, dispersing agents, pigments, setting or hardening accelerators and / or retarders, polymeric resins and anti-foaming agents. The total content of additives and adjuvants preferably varies between 0.001 and 5% by weight relative to the total weight of the dry composition.

[0033] Preferably, in particular for application as a floor product, the dry composition comprises superplasticizing agents and retarders. The retarder is preferably a carboxylic acid or a carboxylic acid salt, in particular tartaric acid.

[0034] The presence of these different additives makes it possible, in particular but not exclusively, to adapt the setting time or the rheology of the wet mortar composition, that is to say after mixing with water, so as to meet expectations depending on the desired product.

[0035] The invention also relates to a method for obtaining a floor product comprising mixing with water a dry mortar composition according to the invention to obtain a wet mortar and depositing said wet mortar on a substrate.

[0036] The weight content of added water, relative to the total weight of hydraulic binder, is preferably between 0.4 and 0.7, in particular between 0.5 and 0.6.

[0037] The floor product is in particular a self-leveling screed. Floor products will traditionally be obtained by curing in air and at room temperature the mortar obtained after mixing. For example, screeds are obtained by mixing the dry mortar composition with water, then pouring the resulting liquid onto a substrate so as to obtain a layer which is then left to harden in air and at room temperature. The substrate is for example a concrete slab or floor.

[0038] The hydraulic binder is however not limited to obtaining floor products, but can also be advantageously used in all types of mortar compositions, such as facade coatings, tile adhesives, jointing mortars, repair mortars, mortars for additive manufacturing or even masonry mortars.

[0039] Examples

[0040] The following examples illustrate the invention in a non-limiting manner.

[0041] Dry mortar compositions were obtained by mixing the components indicated in Table 1 below, which specifies the contents in weight percentages.

[0042] [Tables 1] Cl C2 1 [3-hemihydrate 25 25 25 Portland cement 7 0 0 Blast furnace slag 0 7 0 Ladle slag 0 0 7 Metakaolin 5 5 5 Limestone filler 13 13 13 Silica sand 50 50 50 Superplasticizer 0.4 0.6 0.6 Retarder 0.06 0 0.02

[0043] Examples C1 and C2 are comparative examples, using Portland cement and ground granulated blast furnace slag, respectively, instead of ladle slag. In Example 1 according to the invention, the ladle slag comprised 9% silica, 49% lime, 32% alumina, 6% magnesia, and 1% iron oxide (in weight percentages). In terms of mineralogy, the ladle slag comprised 30% by weight of C12A7 phase, 16% by weight of C3A phase, and 14% by weight of C2S phase. The setting and hardening retarder was tartaric acid.

[0044] The mixing of the compositions was carried out by adding water, in an amount such that the ratio between the amount of water and the total weight of binder and fillers was 0.4.

[0045] Table 2 below indicates for each of the wet mortars, the spreading value as well as the setting time. The spreading value, expressed in mm, corresponds to an average of 3 measurements taken after 3 minutes, using a ring 68 mm in diameter and 35 mm in height.

[0046] [Tables2] Cl C2 1 Spread (mm) 219 130 212 Setting time (min) 76 294 79

[0047] These results show that the binder according to the invention behaves like the Portland cement-based binder in terms of rheology and hardening kinetics. On the other hand, the use of blast furnace slag gives significantly worse results compared to ladle slag.

[0048] The dimensional stability and mechanical strength of the hardened mortars were evaluated after immersion in water at 5°C.

[0049] Example 1 according to the invention showed no dimensional variation, even after 90 days of immersion. On the other hand, comparative example C1 showed very strong swelling, with a very strong dimensional variation, greater than 5 mm / m after 5 days of immersion, and 20 mm / m after 30 days of immersion, leading to the destruction of the sample. Comparative example C2 showed an acceptable dimensional variation, less than 5 mm / m after 3 months of immersion.

[0050] In terms of compressive strength, the example according to the invention exhibited strengths greater than 15 MPa after three months of immersion. In contrast, the compressive strength of comparative examples C1 and C2 was less than 5 MPa already after 1 month of immersion.

[0051] The binder according to the invention therefore makes it possible to obtain rapid-setting mortars, exhibiting high spreadability, and retaining very good properties after immersion in cold water.

Claims

Claims

1. A hydraulic binder comprising 50 to 85% by weight of a calcium sulfate source, 5 to 35% by weight of ladle slag and 0 to 30% by weight of a pozzolanic material.

2. Hydraulic binder according to claim 1, wherein the source of calcium sulfate is selected from hemihydrate, gypsum and anhydrite, alone or in mixture.

3. Hydraulic binder according to one of the preceding claims, in which the pozzolanic material is chosen from fly ash, calcined clays, silica fumes, calcined schists and natural or calcined pozzolans.

4. Hydraulic binder according to one of the preceding claims, wherein the total content of calcium sulfate source, ladle slag and pozzolanic material is at least 80% by weight, and even at least 95% by weight.

5. Hydraulic binder according to one of the preceding claims, in which the cement content is less than 5% by weight, and preferably in which the cement content is zero.

6. Hydraulic binder according to one of the preceding claims, in which the content of calcium sulfate source is between 55 and 80% by weight, in particular between 60 and 75% by weight.

7. Hydraulic binder according to one of the preceding claims, in which the ladle slag content is between 8 and 30% by weight, in particular between 10 and 25% by weight.

8. Hydraulic binder according to one of the preceding claims, in which the content of pozzolanic material is between 0 and 20% by weight.

9. Dry mortar composition comprising a hydraulic binder according to one of the preceding claims and aggregates.

10. Dry mortar composition according to the preceding claim, in which the total aggregate content is between 40 and 90% by weight and the hydraulic binder content is between 10 and 55% by weight relative to the weight of dry mortar composition.

11. A method of obtaining a floor product, in particular a self-leveling screed, comprising mixing with water a dry mortar composition according to one of claims 9 or 10 to obtain a wet mortar and depositing said wet mortar on a substrate.