Hydraulic binder composition

Abstract

The invention relates to a pulverulent hydraulic binder comprising i) 15 to 90% by weight of slag, ii) 5 to 90% by weight of a source of calcium sulfate, iii) 0 to 15% by weight of an alkaline activator, the sum of the weight percentages of slag, the source of calcium sulfate and the alkaline activator being between 70 and 95%, and iv) 0.5 to 10% by weight of alumina comprising at least 10% by weight of amorphous phase.

Description

Composition of hydraulic binder

[0001] The present invention relates to the field of construction materials. More specifically, the invention relates to hydraulic binder compositions as well as dry mortar compositions comprising said hydraulic binder.

[0002] With the aim of reducing CO2 emissions, efforts are currently underway to replace some or all of the Portland cement used in concrete and mortar production with other hydraulic binders that have a lower carbon footprint. Some hydraulic binders exist in which some or all of the Portland cement is replaced by byproducts of the steel industry, such as blast furnace slag. However, these compounds are inherently low in hydraulic properties, requiring the addition of an activator to increase their reactivity. For example, the use of highly alkaline agents is known, but this has the drawback of causing significant pH increases, making the handling of such binders difficult and potentially leading to severe irritation.

[0003] Various gentler activation solutions have been proposed, but the resulting binders often exhibit a relatively high setting time at low temperatures (10°C and below).

[0004] The invention aims to overcome this drawback by proposing a hydraulic binder with a low carbon footprint exhibiting high reactivity at early ages and low temperatures.

[0005] To this end, the invention relates to a powdery hydraulic binder comprising, and preferably made up of: i) 15 to 90% by weight of slag, ii) 5 to 90% by weight of a calcium sulfate source, iii) 0 to 15% by weight of an alkaline activator, the sum of the weight contents of slag, calcium sulfate source and alkaline activator being 70 to 95%, iv) 0.5 to 10% by weight of alumina comprising at least 10% by weight of amorphous phase.

[0006] Another object of the invention is a dry mortar composition comprising such a hydraulic binder and aggregates.

[0007] The inventors were able to demonstrate that adding a small amount of alumina particles, at least partially amorphous, strongly activated the low-temperature binding system.

[0008] The slag is preferably iron and steel slag, specifically blast furnace slag or steel mill slag. The slag is preferably predominantly, or even entirely, amorphous. Advantageously, the slag is ground granulated blast furnace slag.

[0009] The source of calcium sulfate is preferably chosen from anhydrite, hemihydrate, gypsum, phosphogypsum, and mixtures of two or more of these compounds.

[0010] An alkali activator is defined as a compound capable of increasing the pH of the paste after mixing. An alkali activator is therefore a base. An alkali activator can advantageously be a source of lime, that is, a compound capable of releasing lime (calcium oxide or hydroxide) during mixing. The alkali activator is preferably chosen from alkali metal silicates, alkali metal carbonates, alkali metal hydroxides, quicklime, hydrated lime, hydraulic lime, clinker, and mixtures of two or more of these compounds. Clinker can notably be supplied by Portland cement, also known as CEM I type cement.Clinker can also be supplied by other types of cement, for example, CEM II, CEM III, CEM IV, CEMV, or CEM VI. These cements include, in addition to clinker, blast furnace slag, fly ash, pozzolans, and / or silica fume. When the hydraulic binder according to the invention comprises a cement containing blast furnace slag and clinker, the clinker content is included in the alkali activator content, while the blast furnace slag content is included in the slag content. Quicklime is calcium oxide (CaO), hydrated (or "slaked") lime is calcium hydroxide (Ca(OH)₂), and hydraulic lime also contains clays. The alkali activator is preferably clinker, particularly supplied by CEM I type Portland cement.

[0011] The alkaline activator content is preferably between 0 and 12%, in particular between 1 and 10% by weight, or even between 2 and 8%, or between 3 and 7% by weight, relative to the amount of hydraulic binder.

[0012] Alumina is defined as aluminum oxide (Al₂O₃), in other words, a compound with the chemical formula Al₂O₃. Alumina is present as particles with the chemical formula Al₂O₃ in the powdered binder. Alumina has a large number of polymorphs. The thermodynamically stable form of alumina, and by far the most common, is corundum, also called α (alpha) alumina, which has a trigonal-rhombohedral crystal structure. However, this form has proven incapable of activating the binder system in question.

[0013] Alumina is generally produced by calcining aluminum hydroxide (Al(OH)3) at temperatures above 1000°C, but lower temperatures allow for the production of polymorphs other than corundum. It is thus possible to obtain alumina particles that are at least partially amorphous, particularly at calcination temperatures below 500°C, or even below 250°C.

[0014] It has been found that amorphous alumina provides the advantages associated with the invention. Preferably, the alumina therefore comprises at least 50%, or even at least 60% or at least 70%, and in particular at least 80% or at least 90% by weight of amorphous phase. In this text, the amorphous phase content corresponds to the mass proportion of amorphous phase relative to the weight of alumina. The amorphous phase content can be determined by the Rietveld method.

[0015] Preferably, the alumina is therefore a ρ (rho) alumina, which is the only known amorphous polymorph. However, it has been found that commercial aluminas consisting mainly of γ (gamma), δ (delta), or η (eta) crystalline phases can contain some amorphous phase and thus be advantageous within the scope of the invention.

[0016] Alumina preferably has a specific surface area of ​​at least 50 m² / g, particularly at least 150 m² / g, or even at least 200 m² / g, especially between 200 and 400 m² / g. The specific surface area can be determined by the BET method, particularly using nitrogen. Conversely, alpha alumina is very dense and has a low specific surface area, on the order of 10 m² / g.

[0017] Preferably, the alumina has a volumetric particle size distribution such that the median diameter d50 is less than or equal to 100 µm, in particular between 2 and 50 µm, or even between 5 and 20 µm. The particle size distribution can be determined by laser granulometry.

[0018] The alumina content is preferably between 1 and 5%, in particular between 2 and 4% by weight or between 3 and 4% by weight, relative to the quantity of hydraulic binder.

[0019] The sum of the weight contents of slag, source of calcium sulfate and alkaline activator is preferably 75 to 95%, in particular 80 to 90%, relative to the quantity of hydraulic binder.

[0020] According to a preferred embodiment, the slag content, in particular ground granulated blast furnace slag, is between 70 and 90%, in particular between 75 and 85% by weight, and the calcium sulfate source content is between 5 and 20%, in particular between 6 and 18% by weight, relative to the amount of hydraulic binder.

[0021] According to another preferred embodiment, the slag content is between 10 and 30%, in particular between 15 and 25% by weight, and the calcium sulfate source content is between 60 and 90%, in particular between 65 and 85% by weight, relative to the amount of hydraulic binder.

[0022] These different embodiments can advantageously be combined with the preferred embodiments described above concerning the type and quantity of alumina and alkaline activator, as well as the preferred slags and sources of calcium sulfate.

[0023] Preferably, the hydraulic binder consists of slag, a source of calcium sulfate, an alkaline activator, and alumina. The alkaline activator is preferably clinker.

[0024] The dry mortar composition according to the invention comprises a hydraulic binder as described above, as well as aggregates. The composition does not normally comprise any hydraulic binder other than the binder according to the invention.

[0025] Preferably, the hydraulic binder content is between 5 and 60%, in particular between 15 and 50%, by weight of dry mortar mix. Preferably, the aggregate content is between 30 and 90%, in particular between 40 and 80%, by weight of dry mortar mix.

[0026] Aggregates include sands and / or fillers, siliceous, calcareous, and / or dolomitic. "Fillers" refers to aggregates with a particle size less than 63 µm, and "sands" refers to aggregates with a particle size between 63 µm and 4 mm. Aggregates may include recycled aggregates, for example, from demolition, or industrial by-products, or even sands from crushed rock. Aggregates may also include lightweight aggregates, particularly those with an apparent density of less than 200 kg / m³. 3 Lightweight aggregates are selected from perlite, vermiculite, expanded glass beads, expanded polystyrene beads, cenospheres, expanded silicates, aerogels, ground thermosetting polymer powders and mixtures of two or more of these compounds.

[0027] The dry mortar composition may also include at least one additive selected from among the following: dispersing agents, wetting agents (particularly in a content of between 0.05 and 0.2%; for example, chemically modified alkylsulfonates), redispersible polymer powders (particularly in a content of between 0.5 and 10%, preferably between 0.8 and 5%, and even between 1 and 4%), setting and / or hardening accelerators or retarders (particularly in a content of between 0.1 and 1%, for example, calcium formate), thickening agents such as cellulose ethers and starch ethers (particularly in a content of between 0.2 and 0.7%), plasticizers (for example, based on polycarboxylic acid), superplasticizers (for example, based on polyacrylates), rheological agents, air-entraining agents, biocidal agents, pigments, and fibers.Redispersible polymers include vinyl and / or acrylic (co)polymers, for example styrene-acrylic copolymers.

[0028] The dry mortar composition can include, in particular, a dry mortar-adhesive composition for tile adhesive, a masonry mortar composition, a jointing mortar composition, a mortar composition for facade plaster, a bonding mortar composition for external insulation systems, a leveling mortar composition, a repair mortar composition, a base coat composition for external insulation systems, a mortar composition for screed or floor covering, or a mortar composition for additive manufacturing.

[0029] For a dry mortar mix for tile adhesive, the dry mortar composition preferably comprises 20 to 50% by weight of hydraulic binder and 45 to 80% by weight of aggregates. For a dry mortar mix for flooring, particularly for screeds, the dry mortar composition preferably comprises 20 to 40% by weight of hydraulic binder and 60 to 80% by weight of aggregates. For a dry mortar mix for facade rendering (interior or exterior), the dry mortar composition preferably comprises 10 to 40% by weight of hydraulic binder and 60 to 90% by weight of aggregates.

[0030] The composition according to the invention can also be a composition of masonry mortar, jointing mortar, bonding mortar for external insulation systems, leveling mortar, repair mortar, base coat for external insulation systems, mortar for additive manufacturing, etc. In such cases, the dry mortar composition preferably comprises 5 to 20% by weight of hydraulic binder and 60 to 90% by weight of aggregates.

[0031] The following examples illustrate the invention in a non-limiting manner.

[0032] Different aluminas were tested. For the examples according to the invention, the inventors used: - three aluminas marketed under the name "ρ alumina", called A1, A2 and A3, comprising more than 90% by weight of amorphous phase for aluminas A1 and A2, and more than 80% by weight of amorphous phase for alumina A3, and - an alumina marketed under the name "γ alumina", called A4 and containing 30% by weight of amorphous phase. For the comparative examples, the inventors used an α alumina, or corundum, called A5 and free of amorphous phase, and aluminum hydroxide (A6), also free of amorphous phase.

[0033] Table 1 below indicates for each of the aluminas the median diameter D50, determined by laser granulometry as well as the specific surface area S determined by the BET method.

[0034] D50 (µm)S (m² / g)A16300A215300A310220A44075A5100.2A6171.0

[0035] First series of tests

[0036] In a first series of tests, mortar compositions were prepared according to the recipes given in Tables 2 and 3 below, expressed as weight percentages. The slag was ground granulated blast furnace slag, the calcium sulfate source was β hemihydrate (denoted "HH"), and the Portland cement alkali activator was CEM I. The mixture of fillers and admixtures comprised 97% limestone sands and fillers and 3% admixtures, including a redispersible polymer powder and a water-retaining agent. The water content corresponds to the amount of water added to 100 parts of dry mortar.

[0037] The tables also indicate the speed of propagation of ultrasound "V" in m / s at 5°C after 7 days, a quantity which is an indicator of the degree of hydration and mechanical resistance of the wet mortar.

[0038] C1123Slag21,621,621,621,6HH4,054,054,054,05CEM I1,351,351,351,35A1-1--A2--1-A3---1Fillers and adjuvants73727272Water23232323V (m / s)831144717781840

[0039] 45C2C3Slag21,621,621,621,6HH4,054,054,054,05CEM I1,351,351,351,35A10.5---A4-0.5--A5--0.5-A6---0.5Charges and adjuvants72,572,572,572.5Water23232323V (m / s)19651560702812

[0040] Compressive strengths at 5°C were also measured for examples C1 and C2. At 2 days, 7 days, and 28 days, they are respectively 0, 0.2, and 4.7 MPa for comparative example C1 and 0.4, 2.3, and 6.3 MPa for example C2 according to the invention. At a temperature of 20°C, they are 0.7, 4.0, and 4.5 MPa for comparative example C1 and 2.1, 5.4, and 5.6 MPa for example C2 according to the invention.

[0041] These results show that amorphous alumina can activate the binder system at low temperatures.

[0042] Second series of tests

[0043] In a second series of tests, mortar compositions were prepared according to the recipes given in Table 4 below, expressed as weight percentages. The slag was ground granulated blast furnace slag, the calcium sulfate source was β hemihydrate (denoted "HH"), and the Portland cement alkali activator was CEM I. The mixture of fillers and admixtures comprised 71.2% silica sand, 28.5% limestone filler and limestone admixtures, and 0.3% admixtures, including a rheology modifier and a superplasticizer. The water content corresponds to the amount of water added to 100 parts of dry mortar.

[0044] Table 4 shows the compressive strength at 20°C, after 1, 7 and 28 days.

[0045] C46 Dairy 21.624.0HH4.054.5CEM I1.351.5A1-1.2Fillers and additives 7068.8Water 1818Compressive strength (MPa) 1 day 0.86.67 days 13.519.128 days 18.123.2

[0046] These tests show that the addition of amorphous alumina significantly increased the reactivity of the binder system.

Claims

Powdered hydraulic binder comprising: i) 15 to 90% by weight of slag, ii) 5 to 90% by weight of a calcium sulfate source, iii) 0 to 15% by weight of an alkali activator, the sum of the weight contents of slag, calcium sulfate source and alkali activator being 70 to 95%, iv) 0.5 to 10% by weight of alumina comprising at least 10% by weight of amorphous phase. Hydraulic binder according to claim 1, wherein the slag is ground granulated blast furnace slag. Hydraulic binder according to any one of the preceding claims, wherein the source of calcium sulfate is selected from anhydrite, hemihydrate, gypsum, phosphogypsum and mixtures of two or more of these compounds. Hydraulic binder according to any one of the preceding claims, wherein the alkali activator is selected from alkali metal silicates, alkali metal carbonates, alkali metal hydroxides, quicklime, hydrated lime, hydraulic lime, clinker, and mixtures of two or more of these compounds. Hydraulic binder according to the preceding claim, wherein the alkali activator is clinker. Hydraulic binder according to any one of the preceding claims, wherein the alumina comprises at least 50%, in particular at least 80% by weight of amorphous phase. Hydraulic binder according to the preceding claim, wherein the alumina is a ρ alumina. Hydraulic binder according to any one of the preceding claims, wherein the alumina has a specific surface area of ​​at least 50 m² / g, in particular of at least 150 m² / g. Hydraulic binder according to any one of the preceding claims, wherein the alumina has a volumetric particle size distribution such that the median diameter D50 is less than or equal to 100 µm, in particular is between 2 and 50 µm. Hydraulic binder according to any one of the preceding claims, wherein the alumina content is between 1 and 5% by weight, relative to the amount of hydraulic binder. Hydraulic binder according to any one of the preceding claims, wherein the slag content is between 70 and 90% by weight and the calcium sulfate source content is between 5 and 20% by weight, relative to the amount of hydraulic binder. Hydraulic binder according to any one of claims 1 to 10, wherein the slag content is between 10 and 30% by weight and the calcium sulfate source content is between 60 and 90% by weight, relative to the amount of hydraulic binder. Composition of dry mortar comprising a hydraulic binder according to one of the preceding claims and aggregates. Dry mortar composition according to the preceding claim, wherein the hydraulic binder content is between 5 and 60% and the aggregate content is between 30 and 90%, relative to the weight of dry mortar composition. Dry mortar composition according to any one of claims 13 or 14, which is a dry mortar-adhesive composition for tile adhesive, a masonry mortar composition, a jointing mortar composition, a mortar composition for facade plaster, a bonding mortar composition for external insulation systems, a leveling mortar composition, a repair mortar composition, a base coat composition for external insulation systems, a mortar composition for screed or floor covering, or a mortar composition for additive manufacturing.