Dry mortar composition

Abstract

The invention relates to a dry mortar composition comprising a hydraulic binder and aggregates, in which aggregates having a size of greater than or equal to 63 μm are in a proportion of at least 50% based on the total weight of aggregates. The aggregates having a size of greater than or equal to 63 μm have a roundness volume distribution such that the median value of the roundness is between 0.01 and 0.40, and the dry mortar composition has a particle size distribution by volume such that the D30 / D95 ratio is between 4 and 15% and the D70 / D95 ratio is between 60 and 72%.

Description

Dry mortar composition

[0001] The invention is in the field of construction, more particularly in the field of mortars.

[0002] Dry mortar compositions are compositions comprising a hydraulic binder and aggregates. After mixing ("mixing") with water, a paste (wet or fresh mortar) is obtained that 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 resistance, for example compressive strength).

[0004] For flooring products in particular, the spread of the fresh mortar must be high in order to achieve self-leveling properties. This may require a high quantity of mixing water, as well as the use of additives such as plasticizers and superplasticizers.

[0005] It is also important to reduce the environmental footprint of mortars, by reducing the quantities of cement and admixtures as well as the use of water and natural resources.

[0006] This is particularly the case for aggregates, generally sands and fillers, for which it may be interesting to use, rather than river sands, recycled aggregates, for example from demolition, or industrial by-products, or even sands from rock crushing.

[0007] However, it appeared that this type of aggregate reduced the spreading of the fresh mortar, requiring an increase in the quantity of mixing water, to the detriment of the mechanical properties of the hardened mortar, as well as the quantity of admixtures. This deterioration in mechanical properties requires an increase in the hydraulic binder content, to the detriment of the mortar's carbon footprint. It would appear that the reduced spreading comes from the difference in morphology between river sand-type aggregates and aggregates from crushing (whether from recycled products, industrial by-products or even rocks), the latter being both more angular and less spherical than river sand.

[0008] The invention aims to overcome these drawbacks by proposing mortars with a lower environmental footprint, while still having good spreading when fresh and good mechanical performance.

[0009] For this purpose, the subject of the invention is a dry mortar composition comprising a hydraulic binder and aggregates, including aggregates having a size greater than or equal to 63 µm in a proportion of at least 50% relative to the total weight of aggregates, said aggregates having a size greater than or equal to 63 µm having a volume distribution of roundness such that the median value of the roundness is between 0.01 and 0.40, and the dry mortar composition having a distribution of particle sizes by volume such that the ratio D30 / D95 is between 4 and 15% and the ratio D70 / D95 is between 60 and 72%.

[0010] The invention also relates to a hardened mortar, in particular a floor covering, obtained by mixing with water the dry mortar composition according to the invention to obtain a wet mortar, then hardening said wet mortar.

[0011] The inventors were able to demonstrate that in the case of angular aggregates, a particular particle size distribution made it possible to optimize the spreading of the fresh mortar. It is thus possible, despite the use of such aggregates, to improve the mechanical properties of the hardened mortar by reducing the mixing water content or even reducing the content of hydraulic binder and admixtures for the same mechanical strength.

[0012] The aggregates preferably include (or even consist of) sands (with a size between 63 µm and 4 mm), or even sands and fillers (with a size less than 63 µm).

[0013] Preferably, the dry mortar composition does not comprise particles larger than 4 mm. The mass proportion of aggregates having a size greater than or less than a given value, in particular 63 µm, is preferably determined by sieving.

[0014] Roundness (also called roundness in English) characterizes the more or less angular side of the aggregate.

[0015] The median value of the volume distribution of the roundness (always for aggregates having a size greater than or equal to 63 µm) is preferably between 0.05 and 0.40, or even between 0.05 and 0.35, or between 0.10 and 0.30. The D90 of the volume distribution of the roundness is preferably at most 0.80, in particular at most 0.70, or even at most 0.60 and even at most 0.50. By "D90" is meant here the roundness value such that 90% of the volume of aggregates having a size greater than or equal to 63 µm has a roundness less than or equal to this value.

[0016] Preferably, the aggregates having a size greater than or equal to 63 µm also have a volume distribution of sphericity such that the median value of the sphericity is at most 0.90, in particular at most 0.85, or even at most 0.80 and even at most 0.75. Sphericity characterizes the fact that the particle is more or less close to a sphere.

[0017] The volume distributions of roundness and sphericity are determined in particular by dynamic image analysis, using for example the Camsizer X2 device (Retsch-Microtrac).

[0018] The total content of aggregates relative to the weight of dry mortar composition is preferably at least 50%, in particular at least 60% and even at least 70%, or even at least 80%. It is preferably at most 95%.

[0019] The proportion of aggregates having a size greater than or equal to 63 µm, relative to the total weight of aggregates, is preferably between 50 and 95%, or between 55 and 90%, in particular between 60% and 85%, or even between 70 and 80%.

[0020] In order to optimize the spreading of the fresh mortar, the particle size distribution by volume of the dry mortar composition preferably has at least one of the following characteristics, in all possible combinations, or even all of these characteristics: D20 / D95 from 1.0 to 5.0%, in particular from 1.5 to 3.0% D30 / D95 from 5 to 15%, in particular from 6 to 10% D40 / D95 from 10 to 25%, in particular from 14 to 20% D50 / D95 from 17 to 40%, in particular from 20 to 38% D60 / D95 from 34 to 60%, in particular from 40 to 58% D70 / D95 from 62 to 70%, in particular from 63 to 68%.

[0021] As is customary in the art, "DX" corresponds to the particle size such that X% of the particle volume has a size less than or equal to this value. In order to calculate the values ​​of D30, D70 and D95, or more generally any value of "DX", the volume distribution of particle sizes is preferably determined by dynamic image analysis (in particular according to the ISO 13322-2 standard). The measurement is carried out in particular using a Camsizer X2 device (Retsch-Microtrac), the quantity considered being X c Min, also called "minimum chord diameter". To measure this, the particles are suspended in the air.

[0022] Aggregates, particularly aggregates with a size greater than or equal to 63 µm, preferably include recycled aggregates, for example from the demolition of buildings or infrastructure, industrial by-products, and / or sand from rock crushing. This may, for example, be crushed demolition waste, foundry sand, and / or crushed glass. Demolition waste includes, for example, pieces of concrete, mortar, gypsum, or glass. These different materials are generally crushed to achieve the desired sizes, and therefore have a low roundness and low sphericity. In other words, they are angular and rather elongated, unlike river sand particles. The proportion of these materials is preferably at least 50%, or even at least 60%, relative to the weight of aggregates.

[0023] Fillers are preferably chosen from limestone fillers and dolomitic fillers.

[0024] The total content of hydraulic binder relative to the weight of dry mortar composition is preferably between 1 and 40%, in particular between 5 and 30%, or even between 10 and 20%.

[0025] The hydraulic binder can be a mixture of several hydraulic binders.

[0026] The hydraulic binder is preferably chosen from Portland cements, aluminous cements, sulfoaluminous cements, hydrated lime, slags (in particular ground granulated blast furnace slags), fly ash and mixtures of two or more of these compounds. Portland cements include in particular CEM I and CEM II type cements as defined by standard EN 197-1. A CEM I cement comprises at least 95% clinker while a CEM II cement comprises at least 65% clinker and at most 35% blast furnace slag, silica fume, pozzolan, fly ash, calcined shale and / or limestone.

[0027] The hydraulic binder is preferably Portland cement, or is a mixture consisting of Portland cement, aluminous cement and a source of calcium sulfate, such as gypsum, hemihydrate or anhydrite, possibly with the addition of ground granulated blast furnace slag.

[0028] In a preferred embodiment, the hydraulic binder consists of Portland cement, aluminous cement and a source of calcium sulfate. The binder then preferably comprises 5 to 40% Portland cement, 20 to 80% aluminous cement and 10 to 50% of a source of calcium sulfate, relative to the weight of hydraulic binder. Such binders are particularly suitable for the production of self-leveling floor products, for example screeds.

[0029] The dry mortar composition preferably comprises additives, in particular in a content ranging from 0.1 to 10% relative to the weight of dry mortar composition.

[0030] These additives are notably chosen from plasticizers, superplasticizers, accelerators, retarders, defoaming agents, stabilizing agents, redispersible polymer powders, shrinkage reducing agents, rheology agents and water reducing agents.

[0031] 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 is preferably 0.001 to 0.5% by weight. 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 1.0% by weight relative to the weight of the dry mortar composition. The dry mortar composition preferably comprises both accelerators and retarders in order to properly control the setting and hardening of the hydraulic binder.

[0032] The stabilizing and water-retaining agents preferably comprise cellulose ethers. Their content is preferably 0.05 to 1.0% by weight relative to the weight of dry mortar composition.

[0033] The redispersible polymer powders are preferably obtained from at least one monomer chosen from vinyl esters (in particular vinyl esters of carboxylic acids, branched or not, comprising from 1 to 15 carbon atoms), (meth)acrylates (in particular (meth)acrylates of alcohols comprising from 1 to 10 carbon atoms), (meth)acrylic acids, aromatic vinyls, alkenes such as ethylene or propylene, dienes and vinyl halides.In particular, the redispersible polymer powders suitable for the invention are chosen from polymer powders obtained from at least two of the monomers mentioned above, preferably from powders of copolymers chosen from: vinyl acetate-ethylene copolymers, vinyl ester-ethylene-vinyl chloride copolymers, vinyl acetate copolymers, vinyl acetate-acrylate copolymers, copolymers of methyl methacrylate with n-butyl acrylate and / or 2-ethylhexyl acrylate, copolymers of methyl methacrylate with 1,3-butadiene, vinyl chloride-ethylene copolymers, vinyl chloride-acrylate copolymers, styrene-butadiene copolymers, styrene-acrylate copolymers, vinyl acetate-(meth)acrylic acid-ethylene terpolymers. Their content is preferably from 0.2 to 10% by weight, in particular from 0.5 to 5% by weight relative to the weight of dry mortar composition.

[0034] The dry mortar composition according to the invention can be mixed with water in order to obtain a wet mortar, then after hardening a hardened mortar.

[0035] The mixing rate, i.e. the weight of water relative to the weight of dry mortar composition, is preferably between 8% and 28%.

[0036] Curing is preferably done in air and at room temperature, therefore without heating or cooling.

[0037] Hardened mortar is used, in particular, as a floor covering, such as a screed. This most often concerns interior floors (located inside the building), but it can also be exterior floors (part of the building but located outside it, such as balcony or terrace floors). The floor covering preferably has a thickness of between 2 and 10 cm, especially between 3 and 8 cm.

[0038] Alternatively, the hardened mortar can be a facade coating, an adhesive, for example a tile adhesive, or even a joint.

[0039] Examples

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

[0041] Different dry mortar compositions were obtained by mixing 13% CEM I 52.5 N cement, 0.1% additives (superplasticizers, thickener and viscosity regulating agent) and 87% aggregates.

[0042] The aggregates contained two types of sand (maximum size 4 mm) as well as limestone fillers.

[0043] The sands had a median roundness (D50 in volume distribution) of 0.35 and a median sphericity of 0.84. They were therefore relatively angular sands.

[0044] In order to obtain different particle size distributions, these sands and fillers were mixed in different proportions. The mixing rate was 11% based on the weight of the dry mortar composition.

[0045] Table 1 below indicates for each of the tested compositions the proportion “P” of sands in relation to the weight of aggregates, the volume distribution of particle sizes (size X c min, values ​​from D10 to D95, indicated in µm) determined by dynamic image analysis using a Camsizer X2 device (Retsch-Microtrac), and the spread value “E”, expressed in mm (average of 3 measurements, spread measured after 3 minutes, using a ring 68 mm in diameter and 35 mm in height.

[0046] C11234C2P64%75%76%78%80%87%D1071316171720D201635718577320D30841982983 08342672D402784155605746581372D504957821109122612981975D6096115571829 192020042431D70155722812489246024962710D80215427672943289728352983D90 265433333246330032503255D95281836783440351735353589E112145164169160120

[0047] It is clear from the table that Comparative Examples C1 and C2, which have particle size distributions that are not in accordance with the invention, have a significantly lower spread than Examples 1 to 4 according to the invention. In order to achieve, in the case of the Comparative Examples, spread values ​​similar to those obtained for the Examples according to the invention, the mixing ratio must be increased to values ​​of 13 to 15%, to the detriment of the mechanical strength of the hardened mortar.

[0048] Similar results were obtained by replacing the sand with cullet (crushed glass) having a median roundness of 0.09 and a median sphericity of 0.72. The spread values ​​were 90 to 100 mm for particle size distributions outside the invention, compared to 120 to 140 mm for particle size distributions in accordance with the invention.

Claims

A dry mortar composition comprising a hydraulic binder and aggregates, including aggregates having a size greater than or equal to 63 µm in a proportion of at least 50% relative to the total weight of aggregates, said aggregates having a size greater than or equal to 63 µm having a volume roundness distribution such that the median value of the roundness is between 0.01 and 0.40, and the dry mortar composition having a volume particle size distribution such that the D30 / D95 ratio is between 4 and 15% and the D70 / D95 ratio is between 60 and 72%. A composition according to claim 1, which does not comprise particles larger than 4 mm. Composition according to one of the preceding claims, such that the median value of the roundness of the aggregates having a size greater than or equal to 63 µm is between 0.05 and 0.35, in particular between 0.10 and 0.

30. Composition according to one of the preceding claims, such that the aggregates having a size greater than or equal to 63 µm also have a volume distribution of sphericity such that the median value of the sphericity is at most 0.90, in particular at most 0.

85. Composition according to one of the preceding claims, in which the total content of aggregates relative to the weight of dry mortar composition is at least 50%, in particular at least 80%. Composition according to one of the preceding claims, in which the proportion of aggregates having a size greater than or equal to 63 µm, relative to the total weight of aggregates, is between 50 and 90%, in particular between 60% and 85%. Composition according to one of the preceding claims, in which the aggregates, in particular aggregates having a size greater than or equal to 63 µm, comprise recycled aggregates, for example from the demolition of buildings or infrastructures, industrial by-products and / or sand from rock crushing. Composition according to the preceding claim, in which the recycled aggregates are chosen from crushed demolition waste, foundry sands and crushed glass. Composition according to one of the preceding claims, in which the total content of hydraulic binder relative to the weight of dry mortar composition is between 1 and 40%, in particular between 5 and 30%. Composition according to one of the preceding claims, in which the hydraulic binder is chosen from Portland cements, aluminous cements, sulfoaluminous cements, hydrated lime, slags, fly ash and mixtures of two or more of these compounds. Composition according to the preceding claim, in which the hydraulic binder consists of Portland cement, or is a mixture consisting of Portland cement, aluminous cement and a source of calcium sulfate. Composition according to one of the preceding claims, such that the particle size distribution by volume of the dry mortar composition has at least one of the following characteristics:- D20 / D95 from 1.0 to 5.0%- D40 / D95 from 10 to 25%- D50 / D95 from 17 to 40%- D60 / D95 from 34 to 60%. Composition according to one of the preceding claims, further comprising additives chosen from plasticizers, superplasticizers, accelerators, retarders, defoaming agents, stabilizing agents, redispersible polymer powders, shrinkage reducing agents, rheology agents and water reducing agents. Hardened mortar, in particular floor covering, obtained by mixing with water the dry mortar composition according to one of the preceding claims to obtain a wet mortar, then hardening said wet mortar. Hardened mortar according to the preceding claim, which is a floor covering, in particular a screed.