A dry mortar composition comprising lightweight aggregates

Abstract

The invention relates to a dry mortar composition comprising 5-60wt% of a mineral binder and 20-90wt% of aggregates, wherein the aggregates comprise expanded aluminosilicate particles that have been expanded by irradiating raw aluminosilicate particles by means of a radiation having at least one wavelength in the range of 800 to 2000 nm, the amount of said expanded aluminosilicate particles being 1-20wt% with respect to the weight of dry mortar composition.

Description

A dry mortar composition comprising lightweight aggregates

[0001] The invention relates to a dry mortar composition. A dry mortar composition is a pulverulent mixture comprising a hydraulic binder and aggregates. After mixing with water, it forms a paste, called wet (or fresh) 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, tile adhesives, grouts etc.

[0002] Aggregates may comprise heavy aggregates, such as silica sands or calcareous fillers. Heavy aggregates have a bulk density usually above 1500 g / L. It is also known to use, in some instances, lightweight aggregates. In the present specification, lightweight aggregates are aggregates having a bulk density of 700 g / L and less, especially of 500 g / L and less. The bulk density of aggregates may be measured according to EN 1097-3 :1998 standard. Such lightweight aggregates may in some ranges of products impart thermal insulation and / or acoustical correction. More generally, lightweight aggregates improve the workability of the wet mortar and increase the yield, i.e. the amount of wet mortar for a given amount of dry mortar.

[0003] Examples of known lightweight aggregates include expanded perlite and expanded glass beads (for example Poraver®). Expanded perlite is usually obtained by heat treating perlite, which is an amorphous volcanic aluminosilicate. Heat treatment is done by passing the perlite ore into a flame.

[0004] The inventors have surprisingly found that other ways of expanding aluminosilicates make it possible to improve properties of the hardened mortar, especially its compression strength.

[0005] To this end, an object of the invention is a dry mortar composition as defined in Claim 1.

[0006] In the present text, the term “raw particles” designates the particles before expansion while the term “expanded particles” designates the particles after expansion.

[0007] Without being bound by a scientific theory, it seems that the production of expanded aluminosilicate particles using an irradiation in the near-infrared (NIR) range instead of flames makes it possible to obtain particles having a different microstructure, which explains the surprising results in terms of properties of the final mortars that will be explained in greater detail later in the text. The difference of microstructure is however difficult to define precisely and accurately. Microscope observations have shown that the surface of the particles presents less apparent pores, even though the particles are still porous.

[0008] The chemical composition of aluminosilicate particles (raw and / or expanded) preferably comprises at least 50wt%, especially at least 60wt%, of SiO2+Al2O3. The chemical composition may also contain other oxides such as MgO, Fe2O3, CaO, K2O and TiO2. The raw aluminosilicate particles preferably contain combined water, especially in an amount of 1-20wt%, preferably 2-15wt%, even 2-6wt%. The raw aluminosilicate particles preferably have an amorphous, or glassy, structure. They are preferably obtained by crushing volcanic rocks.

[0009] Preferred aluminosilicates are perlite and vermiculite. Preferably, the expanded aluminosilicate particles are therefore particles of expanded perlite or of expanded vermiculite. Before expansion, the amount of combined water in perlite is preferably 2-6wt%, and the amount of water in vermiculite is preferably 8-16wt%. Perlite is particularly preferred.

[0010] The expanded aluminosilicate particles preferably have a water uptake of less than 100%, even of less than 80%, especially from 20 to 70%. Water uptake can be measured according to EN 13055:2016. Such a low water uptake is believed to reflect the different microstructure mentioned before. Therefore, a further object of the invention is a dry mortar composition comprising 5-60wt% of a mineral binder and 20-90wt% of aggregates, wherein the aggregates comprise expanded aluminosilicate particles having a water uptake of less than 100%, even of less than 80%, especially from 20 to 70%, the amount of said expanded aluminosilicate particles being 1-20wt% with respect to the weight of dry mortar composition. The particles are preferably uncoated.

[0011] The inventors also observed that the particles used according to the invention show a better abrasion resistance than conventional perlite.

[0012] The radiation preferably has at least one wavelength in the range of 800 to 1500 nm. The irradiation is preferably made by lamps emitting (at least partially) in the NIR range, for example halogen lamps. These lamps show a broad spectrum that encompasses not only the NIR range, but also part of the UV and visible ranges.

[0013] The best results are obtained using a short and powerful irradiation, i.e. with a high power density. Preferably, the radiation has a power density of at least 50 kW / m², especially of at least 200 kW / m², even of at least 500 kW / m². The duration of irradiation for each aluminosilicate particle is preferably 0.5 to 20 seconds, even 1 to 5 seconds. The temperature of the particles during irradiation is preferably 800 to 1200°C. The irradiation is preferably a continuous process, and especially includes conveying a bed of particles (for example 2 to 20 mm thick) under and / or over a lamp or a series of lamps (especially halogen lamps). The irradiation may be followed by inductive heating.

[0014] The bulk density of the expanded aluminosilicate particles is preferably -350 g / L, especially 100-250 g / L. The bulk density may be measured according to EN 1097-3 :1998 standard. The expanded aluminosilicate particles preferably have a particle size distribution in weight such that the D50 is 0.3-0.7 mm, especially 0.4-0.6 mm and / or the Dmax is 3.0 mm or less, especially 2.5 mm or less. The particle size distribution may be determined by sieving.

[0015] The mineral binder is preferably selected from Ordinary Portland Cements (OPC), Calcium Aluminate Cements (CAC), Calcium Sulfoaluminate Cements (CSA), fly ashes, ground granulated blast furnace slags, ladle slags, air lime, hydraulic lime, a source of calcium sulfate and mixtures thereof. The source of calcium sulfate is preferably selected from gypsum, anhydrite, hemihydrate, and mixtures thereof.

[0016] Some binders are preferred depending on the specific applications: hydraulic lime and calcium sulfate for plasters, OPC and / or air lime for renders, OPC for tile adhesives, a ternary mixture of OPC, CAC and calcium sulfate (or CSA) for screeds or flooring compounds. Fly ashes and slags are preferred, to decrease the carbon footprint of the mortar.

[0017] The aggregates other than the expanded aluminosilicate particles (also called heavy aggregates) are preferably selected from siliceous, calcareous aggregates, dolomitic aggregates, and mixtures thereof. The heavy aggregates preferably comprise sands (size 0-5 mm), and possibly fillers (size 0-0.1 mm). When the mortar is used as a tile adhesive, the maximum size of the aggregates is preferably 2.0 mm, even 0.6 mm.

[0018] The amount of the expanded aluminosilicate particles is preferably 2-20wt% with respect to the weight of dry mortar composition. In a preferred embodiment, the dry mortar composition comprises 10-20wt% of mineral binder and 75-90wt% aggregates, the amount of expanded aluminosilicate particles being 1-10wt%, preferably 2-10wt%, with respect to the weight of dry mortar composition. This is especially useful for plasters and renders.

[0019] In another preferred embodiment, the dry mortar composition comprises 15-40wt% of mineral binder and 55-85wt% aggregates, the amount of expanded aluminosilicate particles being 2-10wt% with respect to the weight of dry mortar composition. This is especially useful for adhesives and basecoats for ETICS (External Thermal Insulation Composite Systems).

[0020] In another preferred embodiment, the dry mortar composition comprises 20-50wt% of mineral binder and 55-80wt% aggregates, the amount of expanded aluminosilicate particles being 2-20wt% with respect to the weight of dry mortar composition. This is especially useful for tile adhesives.

[0021] In another preferred embodiment, the dry mortar composition comprises 5-20wt% of mineral binder and 70-90wt% aggregates, the amount of expanded aluminosilicate particles being 2-20wt% with respect to the weight of dry mortar composition. This is especially useful for masonry mortars.

[0022] In another preferred embodiment, the dry mortar composition comprises 5-20wt% of mineral binder and 60-85wt% aggregates, the amount of expanded aluminosilicate particles being 2-10wt% with respect to the weight of dry mortar composition. This is especially useful for floor screeds.

[0023] The dry mortar composition preferably comprises one or more additive chosen from redispersible polymer powders, accelerators, retarders, rheological modifiers, pigments, defoamers, stabilizers, thickeners, shrinkage-reducing agents, hydrophobic agents, plasticizers, and superplasticizers. The total amount of such additives is preferably 0.1 to 15.0wt%, especially 0.5 to 5.0wt% with respect to the amount of dry mortar composition.

[0024] Accelerators are for example alkali salts, such as lithium (or potassium) sulfates or carbonates, or organic salts such as calcium formate. The total amount of accelerators with respect to the amount of dry mortar composition is preferably 0.1 to 3.0wt%, especially 0.2 to 2.0wt%. Retarders are for example carboxylic acids such as tartaric or citric acids or their salts. The total amount of retarders is preferably 0.01 to 1.0wt% with respect to the amount of dry mortar composition.

[0025] Thickeners and water-retention agents are for example cellulose ethers and / or starch ethers. Their total amount is preferably 0.1 to 0.6wt%, especially 0.2 to 0.5wt% with respect to the amount of dry mortar composition. These additives make it possible to improve the workability of the wet mortar.

[0026] 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. The amount of redispersible polymer powder is preferably 0.2 to 8.0wt%, especially 0.5 to 6.0wt%, with respect to the amount of dry mortar composition.

[0027] 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 wet mortar. This corresponds to a water dosage of 10 to 50% (added to 100% of dry mortar).

[0028] Another object of the invention is a method for obtaining a hardened mortar comprising mixing the dry mortar composition with water to obtain a wet mortar, applying said wet mortar to a substrate, and letting the wet mortar harden. The hardened mortar is preferably a tile adhesive, a masonry mortar, an adhesive, a basecoat for ETICS, a render or a plaster.

[0029] Depending on the application, the substrate is typically a wall or a partition (an exterior wall for a render or an interior wall for a plaster), a floor (for example a screed) or a masonry unit. The substrate may also be an insulation panel in the case of external thermal insulation systems (ETICS).

[0030] In case of a tile adhesive, the tiles or slabs of the tiling may be of various materials, such as ceramic, sandstone, cement, stone, marble, etc. The wet mortar (adhesive) may be applied to the substrate, and possibly also to the tiles or slabs, by means of a glue comb, a hawk, a float, a trowel or a notched trowel.

[0031] In case of a plaster or a render, the wet mortar is applied, for example by means of a trowel to the substrate, before being smoothed, for example by means of a trowel or of a plastering float. Alternatively, the wet mortar may be pumped and projected (for example by pneumatic spraying) on the substrate, for example a wall. The wall may be constructed by any known method, for example by pouring concrete between formworks, by joining masonry elements such as bricks or concrete blocks, or by 3D-printing of mortar.

[0032] In case of a masonry mortar, the wet mortar can be applied by means of a trowel to a surface, and masonry units, such as bricks or blocks, are place into the wet mortar.

[0033] The following examples illustrate the invention in a non-limiting manner.

[0034] Example 1

[0035] The same volume (500L / t) of conventional perlite (comparative example 1-A) on the one hand and perlite expanded by irradiation on the other hand (example 1-B) was added to the same dry mortar composition (weber.therm 301 sold by the Applicant), comprising about 25-30wt% OPC, 65-75wt% aggregates and 5-10wt% additives. In both cases the water dosage was 40%.

[0036] For example 1-A, the perlite particles had been expanded by a flame. The water uptake was 400% (measured according to EN 13055:2016) and the bulk density was 50 g / L. The abrasion resistance was also evaluated by putting together the particles with metallic spheres in a cylinder, rolling the cylinder 50 times back and forth, and measuring the weight percentage of abraded material, which was 40%.

[0037] For example 1-B, the perlite particles were expanded by means of tungsten halogen lamps. Tungsten halogen lamps emit a broad and continuous spectrum from 300 nm to more than 2000 nm. The water uptake was 74% and the bulk density 220 g / L. The resistance to abrasion was much better than for conventional perlite, since the amount of abraded material was only 8%.

[0038] The consistency of the wet mortar was evaluated according to EN 1015-3:1999 by means of a flow table. The flow was 14.5 cm in case of comparative example 1-A and 16.5 cm in case of example 1-B.

[0039] The experiment shows that less water could be added in the dry mortar of the invention, giving rise to higher compression strength. On the other hand, less cement could be used in the mortar composition for the same compression strength, which would reduce the carbon footprint of the mortar.

[0040] Example 2

[0041] In this example, perlite expanded by irradiation was compared to expanded glass beads (Poraver® 0.5-1 mm) in a masonry mortar. The perlite particles were the same as those used for example 1-B.

[0042] The masonry mortar comprised 18.3wt% of mineral binder (OPC), lightweight aggregates (4wt% Poraver® or 5wt% expanded perlite), 0.2wt% of additives, and other aggregates (77.5 or 76.5wt%).

[0043] Poraver® particles had a water uptake of 38%, significantly lower than the one of the perlite particles. The abrasion resistance (7% of abraded material) was comparable to the one of the perlite particles. The bulk density of Poraver® particles was 270 g / L.

[0044] The same volume of lightweight aggregates was added in comparative example 2-A (with Poraver® particles) and in example 2-B (with perlite). The same water dosage (21%) was used for both examples.

[0045] The results in terms of consistency (measured as in example 1 with a flow table), percentage of air, density of the wet mortar, yield (amount of wet mortar in liter by ton of dry mortar), compression and flexural strength (after 28 days of hardening) are expressed in Table 1.

[0046] 2-A2-BFlow (mm)180180Air content (%)1515Fresh density (kg / m3)15201500Yield (l / t)790808Compression strength (MPa)7.19.0Flexural strength (MPa)2.12.9

[0047] The results show that while the workability, consistency and yield were similar to what is obtained by using expanded glass beads (even though the water uptake was higher in case of the perlite), the use of perlite expanded by NIR irradiation makes it possible to significantly improve the mechanical properties of the hardened mortar.

[0048] Example 3

[0049] In this example, single-coat lightweight façade renderings have been sprayed on walls with a spraying machine using a mortar comprising 13.5wt% OPC, 3wt% air lime, 14wt% of a limestone filler, 44wt% of sand, 22wt% of limestone aggregates, 1wt% adjuvants and 2.5wt% of perlite. The water ratio was 18-20%. The perlite particles were the same as those used for example 1-B. Compared to the standard perlite used for the comparative example 1-A, the particles were less damaged by the passage in the screw pump of the spraying machine. The particles used according to the invention were not damaged, even at high speed.

Claims

A dry mortar composition comprising 5-60wt% of a mineral binder and 20-90wt% of aggregates, wherein the aggregates comprise expanded aluminosilicate particles that have been expanded by irradiating raw aluminosilicate particles by means of a radiation having at least one wavelength in the range of 800 to 2000 nm, the amount of said expanded aluminosilicate particles being 1-20wt% with respect to the weight of dry mortar composition.The dry mortar according to Claim 1, wherein the raw aluminosilicate particles contain combined water, especially in an amount of 1-20wt%.The dry mortar according to any one of the preceding claims, wherein the chemical composition of aluminosilicate particles comprises at least 50wt%, especially at least 60wt%, of SiO2+Al2O3.The dry mortar according to any one of the preceding claims, wherein the expanded aluminosilicate particles are particles of expanded perlite or of expanded vermiculite.The dry mortar according to any one of the preceding claims, wherein the expanded aluminosilicate particles have a water uptake of less than 100%.The dry mortar according to any one of the preceding claims, wherein the radiation has a power density of at least 50 kW / m², preferably of at least 500 kW / m².The dry mortar according to any one of the preceding claims, wherein the duration of irradiation for each aluminosilicate particle is 0.5 to 20 seconds.The dry mortar according to any one of the preceding claims, wherein the bulk density of the expanded aluminosilicate particles is 50-300 g / L, preferably 100-250 g / L.The dry mortar according to any one of the preceding claims, wherein the expanded aluminosilicate particles have a particle size distribution in weight such that the D50 is 0.3-0.7 mm and the Dmax is 3 mm or less.The dry mortar according to any one of the preceding claims, wherein the mineral binder is selected from Ordinary Portland Cements, Calcium Aluminate Cements, Calcium Sulfoaluminate Cements, fly ashes, ground granulated blast furnace slags, hydraulic lime, a source of calcium sulfate and mixtures thereof.The dry mortar according to any one of the preceding claims, wherein the aggregates other than the expanded aluminosilicate particles are selected from siliceous, calcareous aggregates, dolomitic aggregates, and mixtures thereof.The dry mortar composition as claimed in any one of the preceding claims, comprising one or more additive chosen from redispersible polymer powders, accelerators, retarders, rheological modifiers, pigments, defoamers, stabilizers, thickeners, shrinkage-reducing agents, hydrophobic agents, plasticizers, and superplasticizers.The dry mortar composition as claimed in any one of the preceding claims, wherein the dry mortar composition comprises :- 10-20wt% of mineral binder and 75-90wt% aggregates, the amount of expanded aluminosilicate particles being 2-10wt% with respect to the weight of dry mortar composition, or- 15-40wt% of mineral binder and 55-85wt% aggregates, the amount of expanded aluminosilicate particles being 2-10wt% with respect to the weight of dry mortar composition, or- 20-50wt% of mineral binder and 55-80wt% aggregates, the amount of expanded aluminosilicate particles being 2-20wt% with respect to the weight of dry mortar composition, or- 5-20wt% of mineral binder and 70-90wt% aggregates, the amount of expanded aluminosilicate particles being 2-20wt% with respect to the weight of dry mortar composition, or- 5-20wt% of mineral binder and 60-85wt% aggregates, the amount of expanded aluminosilicate particles being 2-10wt% with respect to the weight of dry mortar composition.A method for obtaining a hardened mortar comprising mixing the dry mortar composition of any one of the preceding claims with water to obtain a wet mortar, applying said wet mortar to a substrate, and letting the wet mortar harden.The method according to the preceding claim, wherein the hardened mortar is a tile adhesive, a masonry mortar, an adhesive, a basecoat for External Thermal Insulation Composite Systems, a render, or a plaster.

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