hydraulic binder

Abstract

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

Description

[0001] This invention relates to the field of building materials. More specifically, it relates to hydraulic binders and dry mortar compositions comprising said hydraulic binders.

[0002] Dry mortar compositions are typically powdered mixtures containing hydraulic binders and aggregates. When mixed with water (“mixed”), a paste is obtained that can be molded and then hardened to form a hardened mortar (wet mortar or freshly mixed mortar). Such mortars have a wide range of applications: exterior wall plastering, tile adhesives, flooring products such as leveling layers, grouting mortar, masonry mortar, and many others.

[0003] Depending on the intended application, dry mortar compositions must meet a wide range of requirements, both in terms of their applicability (applicability, workability, plasticity, pumpability, rheology, etc.) and in terms of hardened mortar (especially its mechanical strength, such as compressive strength).

[0004] Especially for flooring products, such as leveling layers, several properties are important. Freshly mixed mortar must have high fluidity to achieve self-leveling properties. The mortar must also be able to harden quickly to reduce on-site construction time. High compressive strength is also essential. Dimensional stability of the mortar is also important, both during and after hardening, for example, if the hardened mortar comes into contact with water.

[0005] The purpose of this invention is to provide a hydraulic adhesive suitable for preparing mortars, particularly for flooring products, which exhibits self-leveling properties, rapid curing, and good dimensional stability, especially after exposure to water.

[0006] Therefore, the present invention relates to a hydraulic adhesive 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 pozzolanic material.

[0007] The hydraulic adhesive is preferably used in mortar compositions, and particularly in the production of floor products.

[0008] The calcium sulfate source is preferably selected from hemihydrate gypsum (especially β-hemihydrate gypsum), gypsum and anhydrite, alone or as a mixture.

[0009] Slag is a byproduct of an industrial process involving the melting of starting materials, which aims to separate the metal from the oxide phase, the latter being referred to as "slag".

[0010] Ladle slag is steel slag produced during the secondary metallurgical process of steelmaking. More specifically, converter steel (produced in a converter steelmaking workshop, particularly in an oxygen converter) or so-called electric arc furnace steel (produced in an electric arc furnace steelmaking workshop, particularly by melting scrap steel in an electric arc furnace) is tapped into a ladle and transferred to a device called a "ladle furnace." Ladle furnaces are typically equipped with three graphite electrodes, enabling the achievement of desired grades through additional alloying and deoxidation, and ensuring temperature maintenance. Homogenization of the molten steel is ensured by gas agitation using argon or nitrogen. Ladle slag is the slag from the ladle furnace.

[0011] Ladle slag is distinguished from other steel slags, namely blast furnace slag and other steelmaking slags, namely converter slag (often referred to as "LD slag") and electric arc furnace slag, by its chemical and mineral composition. For example, blast furnace slag used in hydraulic binders is typically amorphous (glassy) because it has been "granulated," i.e., rapidly cooled by pouring water. Ladle slag is also more basic than electric arc furnace slag. However, it should be noted that ladle slag varies in chemical and mineral composition depending on its origin, particularly depending on the additional alloying and deoxidizing agents used.

[0012] Because lime or dolomite is added to 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 components within the limits expressed in weight percentage below: SiO2: 1-20%, particularly 5-15%, particularly 7-12%; CaO: 30-65%, particularly 40-60%, particularly 45-55%; Al2O3: 15-50%, particularly 19-45%, or even 20-42%, particularly 25-40%.

[0014] Ladle slag may also contain magnesium oxide (MgO), especially in the range of 2 to 10%, or even 3 to 8%.

[0015] To avoid negatively impacting setting time, the iron oxide content in ladle slag is preferably less than 10% by weight, especially less than 5% by weight, and even less than 2% by weight.

[0016] The ladle slag is preferably crystallized to at least 30% by weight, particularly to at least 50% or 60%, or even to at least 70% or 75% by weight. Crystallinity can be evaluated by X-ray diffraction using the Rietveld method. Crystallinity will depend particularly on the slag's cooling rate; slower-cooling slag will form more crystalline phases.

[0017] Particularly advantageous for the intended application, ladle slag advantageously contains at least one crystalline phase of the calcium aluminate type (especially C3A and / or C12A7 type, the latter being referred to as calcium aluminate, and / or C4AF), particularly in a weight content of at least 10%, or even at least 15% and even at least 20%, particularly between 10 and 60%, or even between 30 and 55%.

[0018] Preferably, the ladle slag contains both C3A and C12A7 phases, with a total weight content of at least 20%, particularly at least 30%, and especially between 35% and 60%.

[0019] If the ladle slag preferably also contains calcium silicate-type crystalline phases (especially C2S and / or C3S types), the reactivity of the ladle slag is also improved. However, preferably, the total content of calcium aluminate-type crystalline phases is greater than the total content of calcium silicate-type crystalline phases.

[0020] Steel ladle slag preferably has a volumetric particle size distribution such that D50 is less than 50 µm, preferably less than 20 µm, and particularly between 8 and 15 µm. D50 is a size such that 50% by volume of particles have a size lower than this D50 value. The volumetric particle size distribution is preferably determined by laser particle size analysis (also known as laser diffraction particle size analysis). This fineness of the particles particularly enables the slag to acquire good reactivity, allowing it to be used in mortar compositions and achieve the desired properties in terms of setting time and mechanical strength. D90 is preferably less than 100 µm, particularly less than 60 µm.

[0021] The pozzolanic material is preferably selected from fly ash, calcined clay, silica fume, calcined shale, and natural or calcined volcanic ash. Calcined clay is advantageously metakaolin. Pozzolanic materials allow for reduced dimensional changes in mortar after exposure to water. However, their presence is optional.

[0022] Preferably, the total content of the calcium sulfate source, ladle slag, and pozzolanic material is at least 80% by weight, particularly 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 contains very little cement, or even no cement at all. The cement content is advantageously less than 5% by weight, and preferably zero. Cement specifically includes Portland cement, Belite cement, aluminate cement, and sulfoaluminate cement. "Cement content" refers to the total amount of cement optionally contained in the binder.

[0024] The calcium sulfate source content is preferably between 55 and 80% by weight, especially 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, especially between 10 and 25% by weight, or even between 15 and 22% by weight.

[0026] The content of volcanic ash material is preferably between 0 and 25% by weight, particularly 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, the content is zero.

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

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

[0029] This composition is referred to as dry because most or even all of its components are in powder form. The percentages of each component are given as a weight percentage relative to the total components of the composition.

[0030] The aggregates commonly 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 the mortar composition from concrete compositions containing coarse aggregates. The aggregates may contain fillers, which are finely ground inert mineral materials, typically limestone-type or siliceous-type. Preferably, the aggregates contain sand, particularly silica sand, and / or fillers, particularly limestone or dolomite fillers. The aggregates may also contain lightweight aggregates selected from perlite, vermiculite, expanded glass microspheres, expanded polystyrene beads, cenospheres, expanded silicates, aerogels, and mixtures thereof.

[0031] The total aggregate content is preferably 40 to 90%, particularly 50 to 80%, or even 60 to 75% by weight relative to the dry mortar composition. The hydraulic binder content is preferably 10 to 55%, particularly 20 to 50%, or even 25 to 38% by weight relative to the dry mortar composition. The hydraulic binder according to the invention is preferably the only hydraulic binder contained in the dry mortar composition. Therefore, the contents mentioned above apply to the hydraulic binder according to the invention.

[0032] The dry mortar composition may also contain one or more additives, particularly selected from rheology modifiers, plasticizers or superplasticizers, water-retaining agents, air-entraining agents, thickeners, biocides, dispersants, pigments, setting or hardening accelerators and / or retarders, polymer resins, and defoamers. The total content of additives and auxiliaries is preferably between 0.001 and 5% by weight relative to the total weight of the dry composition.

[0033] Preferably, especially for applications as flooring products, the dry composition contains a superplasticizer and a retarder. The retarder is preferably a carboxylic acid or a carboxylate, particularly tartaric acid.

[0034] The presence of these various additives specifically, but not exclusively, enables the adjustment of the setting time or rheology of wet mortar compositions (i.e., after mixing with water) to meet the desired product.

[0035] The present invention also relates to a method for obtaining a ground product, comprising mixing a dry mortar composition according to the invention with water to obtain a wet mortar, and applying the wet mortar to a substrate.

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

[0037] Flooring products, particularly self-leveling flooring layers. Flooring products are typically obtained by mixing a mortar and then allowing it to harden in air at ambient temperature. For example, a leveling layer is obtained by mixing a dry mortar composition with water, then pouring the resulting liquid onto a substrate to form a layer, which is subsequently left to harden in air at ambient temperature. The substrate may be, for example, a concrete slab or floor.

[0038] However, hydraulic adhesives are not limited to the production of floor products, but can also be advantageously used in all types of mortar compositions, such as exterior wall plastering, tile adhesives, grouting mortars, repair mortars, mortars for additive manufacturing, or masonry mortars. Example

[0039] The following examples illustrate the invention in a non-limiting manner.

[0040] A dry mortar composition was obtained by mixing the components shown in Table 1 below, which indicates the content in weight percentages.

[0041] [Table 1] C1 C2 1 β-hemihydrate gypsum 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 .

[0042] Examples C1 and C2 are comparative examples, using Portland cement and finely ground granulated blast furnace slag instead of ladle slag, respectively. In Example 1 according to the invention, the ladle slag comprises 9% silica, 49% lime, 32% alumina, 6% magnesia, and 1% ferric oxide (by weight percentage). Mineralogically, the ladle slag comprises 30% by weight of the C12A7 phase, 16% by weight of the C3A phase, and 14% by weight of the C2S phase. The setting and hardening retarder is tartaric acid.

[0043] The composition is mixed by adding a certain amount of water so that the ratio of water to the total weight of the adhesive and filler is 0.4.

[0044] Table 2 below shows the flowability values ​​and setting time for each type of wet mortar. The flowability values ​​are expressed in mm and correspond to the average of three measurements taken after 3 minutes using a ring with a diameter of 68 mm and a height of 35 mm.

[0045] [Table 2] C1 C2 1 Flowability (mm) 219 130 212 Condensation time (min) 76 294 79 .

[0046] These results indicate that the binder according to the invention behaves similarly to Portland cement-based binders in terms of rheology and hardening kinetics. On the other hand, the results obtained using blast furnace slag are significantly less favorable compared to ladle slag.

[0047] The dimensional stability and mechanical strength of the hardened mortar were evaluated after immersion in water at 5°C.

[0048] Example 1 of the present invention showed no dimensional change, including after immersion for 90 days. In contrast, Comparative Example C1 exhibited very strong expansion with very high dimensional change, greater than 5 mm / m after immersion for 5 days and greater than 20 mm / m after immersion for 30 days, leading to sample failure. Comparative Example C2 showed acceptable dimensional change, less than 5 mm / m after immersion for 3 months.

[0049] Regarding compressive strength, embodiments according to the present invention exhibit a strength exceeding 15 MPa after three months of immersion. In contrast, comparative embodiments C1 and C2 show compressive strength less than 5 MPa even after one month of immersion.

[0050] Therefore, the adhesive according to the invention enables the production of mortars that set rapidly, exhibit high fluidity, and retain very good performance after immersion in cold water.

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 pozzolanic material.

2. The hydraulic adhesive according to claim 1, wherein the calcium sulfate source is selected from hemihydrate gypsum, gypsum and anhydrite, alone or as a mixture.

3. The hydraulic binder according to any one of the preceding claims, wherein the pozzolanic material is selected from fly ash, calcined clay, silica fume, calcined shale, and natural or calcined pozzolanic material.

4. The hydraulic binder according to any 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. The hydraulic adhesive according to any one of the preceding claims, wherein the cement content is less than 5% by weight, and preferably wherein the cement content is zero.

6. The hydraulic adhesive according to any one of the preceding claims, wherein the calcium sulfate source content is between 55 and 80% by weight, particularly between 60 and 75% by weight.

7. The hydraulic binder according to any one of the preceding claims, wherein the ladle slag content is between 8 and 30% by weight, particularly between 10 and 25% by weight.

8. The hydraulic adhesive according to any one of the preceding claims, wherein the content of the pozzolanic material is between 0 and 20% by weight.

9. A dry mortar composition comprising a hydraulic binder and aggregate according to any one of the preceding claims.

10. The dry mortar composition according to the preceding claims, wherein the total aggregate content is 40 to 90% by weight relative to the weight of the dry mortar composition, and the hydraulic binder content is 10 to 55% by weight.

11. A method for obtaining a floor product, particularly a self-leveling layer, comprising mixing a dry mortar composition according to any one of claims 9 or 10 with water to obtain a wet mortar, and applying the wet mortar to a substrate.