A dry mortar composition

Abstract

The invention relates to a dry mortar composition comprising aggregates and a hydraulic binder, said hydraulic binder comprising 0-40wt% of a source of calcium sulfate (CS), 0-50wt% Portland Cement (PC), and 40-90wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder, wherein said source of aluminum oxide comprises treated aluminum salt slag (TASS) and optionally one or more of Calcium Aluminate Cement (CAC) and Calcium Sulfoaluminate Cement (CSA), the weight ratio (TASS:(CAC+CSA)) between the amount of said treated aluminum salt slag and the sum of the amounts of Calcium Aluminate Cement and Calcium Sulfoaluminate Cement being 10:90 to 100:0, said treated aluminum salt slag comprising 50-80wt% Al2O3, 2-15wt% SiO2, 3-12wt% MgO, 0-5wt% F+Cl, 0-5wt% CaO, 0-4wt% Fe2O3 (total iron) and less than 3wt% metallic aluminum.

Description

A dry mortar composition

[0001] The invention relates to a dry mortar composition.

[0002] A dry mortar composition is a pulverulent mixture comprising a hydraulic binder and aggregates. After mixing with water, it forms a paste, called wet mortar, that can be applied on various substrates before setting and hardening, finally forming a hardened mortar. Mortars can for example be used as renders, plasters, flooring compounds, masonry mortars, concrete repair mortar, tile adhesives, grouts etc. or to make constructions elements by additive manufacturing.

[0003] Concrete repair mortars are used to repair and restore damaged concrete surfaces. They must achieve a high level of bond with existing concrete, allowing it to seamlessly integrate with the damaged area and restore the structural integrity of the concrete element. Concrete repair mortar must meet specific requirements to ensure its effectiveness in repairing and restoring damaged concrete. These requirements include high compressive strength (to match or exceed the strength of existing concrete, so that the repaired area can withstand the same loads as the surrounding undamaged concrete), good adhesion (to prevent the repaired area from delaminating or failing under stress), workability (to ensure proper filling of cracks, voids, and imperfections), durability (to ensure long-term performance and protection of the repaired concrete) and should be compatible with the existing concrete in terms of composition, strength, and expansion characteristics.

[0004] Concrete repair mortars are especially used to fill and seal cracks, spalling, and chipped areas in concrete structures, to patch holes, voids, and imperfections in concrete surfaces, restoring a uniform and smooth surface, to level uneven concrete surfaces and resurface deteriorated concrete slabs, floors, and other horizontal elements, to repair and strengthen damaged concrete structural elements, such as beams, columns, and foundations, and to protect concrete surfaces from corrosion caused by chloride ions and chemical attack from sulfates and other aggressive substances.

[0005] Flooring compounds, also known as a self-leveling compounds or floor leveling compounds are designed to create a smooth, flat, and level surface for installing tiles, laminate flooring, vinyl flooring, and other floor coverings. They can be used over a variety of subfloors, including concrete, plywood, and backer boards. Flooring compounds must fulfill a number of requirements, including an excellent flowability, allowing it to self-level and spread evenly over the subfloor, filling any voids or imperfections, a rapid hardening, minimizing downtime and allowing for efficient installation of floor coverings, a good adhesion to the subfloor, ensuring a strong bond and preventing the floor covering from delaminating or lifting and a high compressive strength, to support the weight of the floor covering and any furniture or appliances that will be placed on it.

[0006] An aim of the invention is especially to provide a mortar that satisfies these requirements and can therefore be used as concrete repair mortars or flooring compounds. A further goal to be achieved is to lower the carbon footprint of the mortar. The hydraulic binder used in mortars is often cement, especially Portland cement (PC), Calcium Aluminate Cement (CAC) or Calcium Sulfoaluminate Cement (CSA), the production of which requires huge amounts of energy and releases large amounts of CO2in the atmosphere. There is in consequence a need to provide mortar compositions that have a much lower CO2footprint while still meeting the requirements, for example in terms of workability and mechanical resistance.

[0007] To this end, the invention relates to a dry mortar composition comprising aggregates and a hydraulic binder, said hydraulic binder comprising 0-40wt% of a source of calcium sulfate (CS), 0-50wt% Portland Cement (PC), and 40-90wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder, wherein said source of aluminum oxide comprises treated aluminum salt slag (TASS) and optionally one or more of Calcium Aluminate Cement (CAC) and Calcium Sulfoaluminate Cement (CSA), the weight ratio (TASS:(CAC+CSA)) between the amount of said treated aluminum salt slag and the sum of the amounts of Calcium Aluminate Cement and Calcium Sulfoaluminate Cement being 10:90 to 100:0. Said treated aluminum salt slag comprises 50-80wt% Al2O3, 2-15wt% SiO2, 3-12wt% MgO, 0-5wt% F+Cl, 0-5wt% CaO, 0-4wt% Fe2O3(total iron) and less than 3wt% metallic aluminum.

[0008] The inventors have found that in binary binders and ternary binders based on CAC or CSA and comprising calcium sulfate and / or Portland cement, CAC and CSA could be at least partially substituted by treated aluminum salt slag, thus reducing the carbon footprint of the mortar, without sacrificing the reactivity of the binder and the required properties and performances of the mortar, in particular for applications as concrete repair mortars and flooring compounds.

[0009] Aluminum salt slag, also known as “salt cake” or “dross” is a by-product of the secondary aluminum industry. Recycling of aluminum involves the melting of aluminum scraps under a bath of molten salts (chlorides, especially sodium chloride and potassium chloride, and optionally fluorides, such as cryolite or calcium fluoride). The salt flux protects the molten aluminum pool from oxidation and improves the metal recovery from the scrap. This generates a by-product called “aluminum salt slag” containing oxides (especially aluminum oxide), metallic aluminum and halogenides.

[0010] The raw material used in the present invention, called “treated aluminum salt slag” or TASS, is the result of a further treatment of the salt slag in order to reduce the content of metallic aluminum and halogenides. The treatment usually involves crushing, milling, screening and washing steps. Crushing, milling and screening steps make it possible to separate metallic aluminum, while washing (or leaching) steps, usually with water at ambient or around 100°C, makes it possible to recover the salt flux. The treatment may also involve drying and / or calcination steps. The obtained product, called “treated aluminum salt slag”, is a mineral powder comprising at least 50wt% of aluminum oxide (Al2O3). As explained before, this mineral powder is obtained by a treatment of aluminum salt slag involving crushing, milling, screening, and washing steps. Such mineral powders are for example sold under the tradenames Paval, Serox, Valoxy, Oxiton or Oxidur.

[0011] The treated aluminum salt slag comprises 50-80wt%, especially 60-70wt%, Al2O3, 2-15wt%, especially 5-10wt%, SiO2, 3-12wt%, especially 5-10wt%, MgO, and 0-5wt%, especially 0.5-4wt%, F+Cl. It may also comprise 0-5wt%, especially 1-4wt%, CaO and 0-4wt%, especially 1-3wt%, Fe2O3(total iron).

[0012] The amount of metallic aluminum is less than 3wt%, preferably less than 2wt% or less than 1wt%. The presence of metallic aluminum may indeed cause the mortar to swell due to chemical reactions that generate gaseous hydrogen. Metallic aluminum may be removed by grinding and sieving the treated aluminum salt slag. The generation of hydrogen may also be prevented or reduced by adding in the mortar composition a compound selected from nitrates (especially lithium nitrate, potassium nitrate, sodium nitrate, ceric ammonium nitrate), sulfates (especially lithium sulfate), carbonates (especially lithium carbonates), permanganates (especially potassium permanganate), and methylthioninium chloride. The amount of such a compound is preferably 0.1 to 5.0wt% with respect to the weight of mortar composition.

[0013] In terms of mineralogy, the treated aluminum salt slag preferably comprises corundum and spinel (MgAl2O4) phases. The spinel content is preferably 10-35wt%, especially 12-30wt%. The corundum content is preferably 5-35wt%, especially 7-20wt%. The treated aluminum salt slag may in addition comprise boehmite, gibbsite, norstrandite and / or bayerite phases, especially in a total content of 8-30wt%. The crystalline phase content is preferably at least 40wt%, even at least 50wt%, for example 60-80wt%. This chemical and mineralogical composition advantageously leads to a high reactivity in binary and ternary binder systems comprising calcium sulfate and / or PC.

[0014] To improve its reactivity and its ability to replace CAC and / or CSA, the treated aluminum salt slag preferably has a particle size distribution (based on a volume distribution) such that the D50 is 3-50 µm, especially 5-30 µm, even 8-25 µm. The D90 is preferably 200 µm or less, even 100 m or less. The particle size distribution can be determined by laser granulometry.

[0015] The source of aluminum oxide comprises a mixture of TASS and (optionally) CAC and / or CSA. It preferably consists of TASS and one or more of CAC and CSA. Alternatively, the source of aluminum oxide may comprise further sources.

[0016] CAC and CSA are optional, since in the embodiment where the weight ratio TASS:(CAC+CSA) is 100:0, the amount of CAC and CSA is zero. The source of aluminum oxide then preferably consists of TASS.

[0017] The weight ratio TASS:(CAC+CSA) is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40. In one embodiment, the binder comprises CAC but no CSA. In such a case, the weight ratio TASS:CAC is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40. In another embodiment, the binder comprises CSA but no CAC. In such a case, the weight ratio TASS:CSA is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40.

[0018] The source of calcium sulfate (CS) is preferably selected from gypsum, anhydrite, hemihydrate, phosphogypsum and mixtures thereof. Mixtures of anhydrite and hemihydrate are especially preferred. The amount of the source of calcium sulfate is preferably 15-40wt%, more preferably 20-35wt%, with respect to the weight of hydraulic binder.

[0019] Portland Cement (PC) is preferably of the CEM I or CEM II type. In the latter case it may then contain fly ashes, silica fume, pozzolans or ground granulated blast furnace slag in addition to clinker.

[0020] In a first preferred embodiment, the hydraulic binder is based on a binary binder, in which CAC and / or CSA is at least partially substituted by TASS. In this embodiment, the hydraulic binder preferably comprises (and more preferably consists of) 10-40wt%, especially 15-35wt%, or more preferably 20-30wt%, of a source of calcium sulfate (CS) and 60-90wt%, especially 65-85wt% or more preferably 70-80wt%, of a source of aluminum oxide, with respect to the weight of hydraulic binder. In this embodiment, the source of aluminum oxide preferably consists of TASS and CSA, and the weight ratio TASS:CSA is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40.

[0021] In a second preferred embodiment, the hydraulic binder is based on a ternary binder, in which CSA and / or CAC is at least partially substituted by TASS.

[0022] In a first variant of this second embodiment, the hydraulic binder comprises 15-40wt%, especially 20-35wt%, of a source of calcium sulfate (CS), 10-35wt%, especially 15-30wt%, Portland Cement (PC), and 40-65wt%, especially 45-60wt%, of a source of aluminum oxide, with respect to the weight of hydraulic binder. In that first variant, the source of aluminum oxide preferably consists of TASS and CAC, and the weight ratio TASS:CAC is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40.

[0023] In a second variant of this second embodiment, the hydraulic binder comprises 0-40wt%, especially 10-30wt%, of a source of calcium sulfate (CS), 10-50wt%, especially 20-40wt%, Portland Cement (PC), and 50-90wt%, especially 60-80wt%, of a source of aluminum oxide, with respect to the weight of hydraulic binder. In that second variant, the source of aluminum oxide preferably consists of TASS and CSA, and the weight ratio TASS:CSA is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40.

[0024] In a third variant of this second embodiment, the hydraulic binder comprises 0-10wt%, especially 0-5wt%, of a source of calcium sulfate (CS), 10-50wt%, especially 20-40wt%, Portland Cement (PC), and 40-90wt%, especially 50-80wt%, of a source of aluminum oxide, with respect to the weight of hydraulic binder. In that second variant, the source of aluminum oxide preferably consists of TASS and CSA, and the weight ratio TASS:CSA is preferably 15:85 to 85:15, especially 20:80 to 80:20, even 25:75 to 75:25, or 30:70 to 60:40.

[0025] In the hydraulic binder, the total amount of CS, PC, CAC, CSA, and TASS is preferably at least 80wt%, even at least 90wt%, with respect to the weight of hydraulic binder. The hydraulic binder may also comprise lime. Preferably, the hydraulic binder consists of CS, PC, CAC, CSA, and TASS.

[0026] The aggregate content is preferably 40-70wt%, even 45-60wt%, with respect to the weight of the dry mortar composition.

[0027] The aggregates are preferably selected from siliceous, calcareous aggregates, dolomitic aggregates, and mixtures thereof. Examples are limestone fillers, dolomite fillers, and silica sand. The aggregates preferably comprise sands (size 0-6 mm) and / or fillers (size 0-0.1 mm). Alternatively, or cumulatively, the aggregates may comprise lightweight aggregates, i.e. aggregates having an apparent density of at most 600 kg / m3, such as hydrophobic expanded perlite, thermosetting polymer powder (for example micronized rubber powder), hollow silicate particles (for example expanded glass beads and / or cenospheres) and mixtures thereof. The aggregates may also comprise fibers.

[0028] The hydraulic binder content is preferably 25-60wt%, even 30-55wt%, with respect to the weight of the dry mortar composition.

[0029] The dry mortar composition may further comprise one or more additive, especially chosen from redispersible polymer powders, pigments, defoamers, stabilizers, thickeners, water-retention agents, shrinkage-reducing agents, hydrophobic agents, retarders, accelerators, plasticizers and superplasticizers. The total amount of such additives, with respect to the weight of dry mortar composition is preferably 0.1 to 8.0wt%, especially 0.5 to 3.0wt%. Thickeners and water-retention agents are for example cellulose ethers and / or starch ethers. The redispersible polymer powder preferably comprises at least a polymer based on one or more monomers selected from the group including vinyl esters (especially vinyl esters of unbranched or branched alkylcarboxylic acids having from 1 to 15 carbon atoms), methacrylates and acrylates (especially (meth)acrylates of alcohols having from 1 to 10 carbon atoms), methacrylic acid, acrylic acid, vinyl aromatics, olefins (such as ethylene or propylene), dienes and vinyl halides. Accelerators and retarders are advantageously used in combination in order to regulate the setting and hardening of the wet mortar. The accelerator is for example a lithium salt, such as lithium carbonate, while the retarder is for example a polycarboxylic acid or a salt thereof, such as tartaric acid or citric acid.

[0030] The invention also relates to a hardened mortar made by mixing the dry mortar composition of the invention with water to make a wet mortar and letting said wet mortar harden.

[0031] The ratio of water to the dry mortar composition (“water ratio”) preferably ranges from 0.10 to 0.50 by weight, in order to get the right consistency for the paste (wet mortar). This corresponds to a water dosage of 10 to 50% (added to 100% of dry mortar).

[0032] The hardened mortar is especially a flooring compound or a concrete repair mortar.

[0033] The invention also relates to a method of repairing damaged concrete, comprising mixing the dry mortar composition with water to make a wet mortar and applying said wet mortar on damaged areas of said concrete. The wet mortar may be applied to the prepared concrete surface using a trowel or other appropriate tool. The wet mortar is carefully worked into the cracks, voids, and imperfections, ensuring complete filling and coverage. After hardening, the mortar is finished to match the surrounding concrete surface. This may involve smoothing, texturing, or applying a protective coating if necessary.

[0034] Flooring compounds are especially self-levelling floors and screeds.

[0035] The invention also relates to a method of applying a flooring compound on a subfloor, comprising mixing the dry mortar composition with water to make a wet mortar and applying said wet mortar to said subfloor. The application can be made by a trowel or, preferably, thanks to a self-levelling mechanism.

[0036] The dry mortar composition may also be used for other applications, for example as renders, plasters, tile adhesives, masonry mortars, grouts etc. or to manufacture construction elements by additive manufacturing.

[0037] The following examples illustrate the invention in a non-limitative way.

[0038] First series of examples

[0039] Dry mortar compositions to be used as concrete repair mortars have been obtained by mixing 59wt% of aggregates (silica sand and limestone fillers) with 39.5wt% of a hydraulic binder and 1.5wt% of additives (including redispersable polymers, retarders, starch ethers, cellulose ethers and defoamers). The water ratio was 19%.

[0040] In a comparative example, the hydraulic binder comprised 20wt% PC (CEM II A-L 42.5 R), 52wt% CAC (Ciment Fondu®) and 28wt% of calcium sulfate (mixture of anhydrite and hemihydrate). The initial and final setting time were 33 and 48 minutes. After 24 hours, the flexural strength was 5.6 MPa, and the compression strength was 29 MPa. After 28 days, the shrinkage (in mm / m) was 0.66 mm / m, the flexural strength was 7.8 MPa, and the compression strength was 42 MPa.

[0041] In a first inventive example, CAC was partially substituted by TASS (Paval, Befesa), such that the TASS:CAC weight ratio was 25:75.

[0042] The initial and final setting time were 23 and 25 minutes. After 24 hours, the flexural strength was 4.6 MPa, and the compression strength was 27 MPa. After 28 days, the shrinkage (in mm / m) was 0.39 mm / m, the flexural strength was 7.1 MPa, and the compression strength was 46 MPa.

[0043] In a second inventive example, the TASS:CAC weight ratio was 50:50.

[0044] The initial and final setting time were 26 and 34 minutes. After 24 hours, the flexural strength was 3.8 MPa, and the compression strength was 19 MPa. After 28 days, the shrinkage (in mm / m) was 0.19 mm / m, the flexural strength was 5.4 MPa, and the compression strength was 42 MPa.

[0045] The example show that the substitution of CAC by TASS improved the reactivity, the compression strength, and the shrinkage of the repair mortars.

[0046] Second series of examples

[0047] Dry mortar compositions for self levelling screeds have been obtained by mixing 49.7wt% of aggregates (limestone fillers) with 49.7wt% of a hydraulic binder and 0.5wt% of additives (including 0.01wt% of lithium carbonate and 0.41wt% of tartaric acid). The water ratio was 41%.

[0048] In a comparative example, the hydraulic binder comprised 25wt% of PC (CEM I), 50wt% of CAC and 25wt% of a source of calcium sulfate (anhydrite and hemihydrate). The compressive strength was 21 MPa after 2 days, 22 MPa after 7 days and 29 MPa after 28 days.

[0049] In a further comparative example, half of the CAC was substituted by a limestone filler. In that case the compressive strength was 5 MPa after 2 days, 4 MPa after 7 days and 9 MPa after 28 days.

[0050] In the inventive examples, CAC was partially substituted by TASS so that the TASS:CAC ratio was 50:50.

[0051] Several commercial TASS were tested. When the TASS was Serox, the compressive strength was 17 MPa after 2 days, 21 MPa after 7 days and 24 MPa after 28 days. When the TASS was Paval (Befesa), the compressive strength was 18 MPa after 2 days, 19 MPa after 7 days and 26 MPa after 28 days.

[0052] These results show that the replacement of CAC by TASS makes it possible to obtain flooring compounds having comparable mechanical properties. In addition, the spread of the mortars was similar.

Claims

A dry mortar composition comprising aggregates and a hydraulic binder, said hydraulic binder comprising 0-40wt% of a source of calcium sulfate (CS), 0-50wt% Portland Cement (PC), and 40-90wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder, wherein said source of aluminum oxide comprises treated aluminum salt slag (TASS) and optionally one or more of Calcium Aluminate Cement (CAC) and Calcium Sulfoaluminate Cement (CSA), the weight ratio (TASS:(CAC+CSA)) between the amount of said treated aluminum salt slag and the sum of the amounts of Calcium Aluminate Cement and Calcium Sulfoaluminate Cement being 10:90 to 100:0,said treated aluminum salt slag comprising 50-80wt% Al2O3, 2-15wt% SiO2, 3-12wt% MgO, 0-5wt% F+Cl, 0-5wt% CaO, 0-4wt% Fe2O3(total iron) and less than 3wt% metallic aluminum.The dry mortar composition according to Claim 1, wherein the treated aluminum salt slag comprises corundum and spinel (MgAl2O4) phases.The dry mortar composition according to any one of the preceding Claims, wherein the treated aluminum salt slag has a particle size distribution, based on a volume distribution, such that the D50 is 3-50 µm, especially 5-30 µm.The dry mortar composition according to any one of the preceding Claims, wherein the source of aluminum oxide consists of treated aluminum salt slag (TASS) and one or more of Calcium Aluminate Cement (CAC) and Calcium Sulfoaluminate Cement (CSA).The dry mortar composition according to any one of the preceding Claims, wherein the weight ratio TASS:(CAC+CSA) is 15:85 to 85:15, especially 20:80 to 80:20.The dry mortar composition according to any one of the preceding Claims, wherein the hydraulic binder comprises 15-40wt% of a source of calcium sulfate (CS), 10-35wt% Portland Cement (PC), and 40-65wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder.The dry mortar composition according to Claim 6, wherein the source of aluminum oxide consists of treated aluminum salt slag and Calcium Aluminate Cement.The dry mortar composition according to any one of Claims 1 to 5, wherein the hydraulic binder comprises 10-40wt% of a source of calcium sulfate (CS) and 60-90wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder.The dry mortar composition according to any one of Claims 1 to 5, wherein the hydraulic binder comprises 0-40wt% of a source of calcium sulfate (CS), 10-50wt% Portland Cement (PC), and 50-90wt% of a source of aluminum oxide, with respect to the weight of hydraulic binder.The dry mortar composition according to any one of Claims 8 or 9, wherein the source of aluminum oxide consists of treated aluminum salt slag and Calcium Sulfoaluminate Cement.The dry mortar composition according to any one of the preceding Claims, wherein the hydraulic binder also comprises lime.The dry mortar composition according to any one of the preceding Claims, wherein the aggregate content is 40-70wt%, even 45-60wt%, with respect to the weight of the dry mortar composition.A hardened mortar, especially a flooring compound or a concrete repair mortar, made by mixing the dry mortar composition of Claims 1 to 12 with water to make a wet mortar, and letting said wet mortar harden.A method of repairing damaged concrete comprising mixing the dry mortar composition according to any one of Claims 1 to 12 with water to make a wet mortar and applying said wet mortar on damaged areas of said concrete.A method of applying a flooring compound on a subfloor, comprising mixing the dry mortar composition according to any one of Claims 1 to 12 with water to make a wet mortar and applying said wet mortar to said subfloor.