Dry mortar composition

Abstract

The present invention relates to a dry mortar composition comprising a hydraulic binder and an aggregate, comprising an aggregate having a size of 63 [mu] m or more in a proportion of at least 50% relative to the total weight of the aggregate, the aggregate having a size of 63 [mu] m or more having a volume distribution such that a median roundness value is 0.01 to 0.40, and the dry mortar composition has a particle size distribution by volume such that a D30 / D95 ratio is from 4% to 15% and a D70 / D95 ratio is from 60% to 72%.

Description

[0001] The present invention belongs to the field of construction, and more particularly to the field of mortars.

[0002] A dry mortar composition is a composition comprising a hydraulic binder and an aggregate. After mixing with water ("blending"), a paste (wet or fresh mortar) is obtained, which can be shaped and subsequently hardened to form a hardened mortar. Such mortars can be used for various applications: exterior wall coatings, tile adhesives, floor products (such as screeds), jointing mortars, masonry mortars (mortiers de ) and many other applications.

[0003] Depending on the application, the dry mortar composition must meet a wide range of requirements, including both its handling ability (spreading ability (étalement), workability (ouvrabilité), plasticity (maniabilité), pumpability, rheology, etc.) and the hardened mortar (especially its mechanical strength, such as compressive strength).

[0004] Especially for floor products, the fresh mortar must spread to a high degree to achieve self - leveling properties. To achieve this, a large amount of mixing water may be required, as well as the use of additives such as fluidizing agents and superplasticizers.

[0005] It is further important to reduce the environmental footprint of the mortar, by reducing the amount of cement and additives used, as well as the use of water and natural resources.

[0006] This is especially true for aggregates (usually sand and fillers), for which it may be advantageous to use recycled aggregates (such as from demolition or industrial by - products, or even sand from rock crushing) instead of river sand.

[0007] However, it has been found that this type of aggregate reduces the spreadability of the fresh mortar, such that the amount of mixing water must be increased, which has an adverse effect on the mechanical properties of the hardened mortar as well as the amount of additives. This deterioration of the mechanical properties makes it necessary to increase the content of the hydraulic binder, which has an adverse effect on the carbon footprint of the mortar. The poorer spreadability seems to be due to the morphological differences between river sand and crushed aggregates (whether from recycled products, industrial by - products or rock), with crushed aggregates having greater angularity and smaller sphericity than river sand.

[0008] The object of the present invention is to overcome these drawbacks by providing a mortar having a smaller environmental footprint but having good fresh spreadability and good mechanical properties.

[0009] To this end, the object of the present invention is to provide a dry mortar composition comprising a hydraulic binder and an aggregate, which comprises at least 50% by weight, relative to the total weight of the aggregate, of an aggregate having a size greater than 63 μm, the aggregate having a size greater than 63 μm having a volume distribution of roundness such that the median roundness value is from 0.01 to 0.40, and the dry mortar composition having a volume-based particle size distribution such that the D30 / D95 ratio is from 4% to 15% and the D70 / D95 ratio is from 60% to 72%.

[0010] The present invention also relates to a hardened mortar, in particular a floor covering (revêtement de sol), which is obtained by mixing the dry mortar composition according to the invention with water to obtain a wet mortar and then hardening the wet mortar.

[0011] The inventors have been able to demonstrate that, in the case of angular aggregates, a specific particle size distribution optimizes the spreadability of the fresh mortar. Despite the use of such aggregates, it is thus possible to improve the mechanical properties of the hardened mortar at the same mechanical strength by reducing the mixing water content, or by reducing the content of the hydraulic binder and additives.

[0012] The aggregate preferably comprises sand (or even consists of sand) (the sand having a size from 63 μm to 4 mm), or even sand and a filler (having a size less than 63 μm).

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

[0014] Roundness characterizes the more or less angular aspect of the aggregate.

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

[0016] Preferably, the aggregate having a size greater than 63 μm further has a volume distribution of sphericity such that the median sphericity value is at most 0.90, in particular at most 0.85, or even at most 0.80, even at most 0.75. Sphericity characterizes the degree of approximation of the particle to a sphere.

[0017] In particular, the volume distribution of roundness and sphericity is determined by dynamic image analysis, for example using a Camsizer X2 (Retsch-Microtrac).

[0018] Based on the weight of the dry mortar composition, the total content of the aggregate by weight is preferably at least 50%, particularly at least 60%, even at least 70% or at least 80%. Preferably, it does not exceed 95%.

[0019] Based on the total weight of the aggregate, the proportion of the aggregate with a size above 63 μm is preferably 50% to 95%, or 55% to 90%, particularly 60% to 85%, or even 70% to 80%.

[0020] To optimize the spread 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 any or all possible combinations:

[0021] D20 / D95 ranges from 1.0% to 5.0%, particularly from 1.5% to 3.0%

[0022] D30 / D95 ranges from 5% to 15%, particularly from 6% to 10%

[0023] D40 / D95 ranges from 10% to 25%, particularly from 14% to 20%

[0024] D50 / D95 ranges from 17% to 40%, particularly from 20% to 38%

[0025] D60 / D95 ranges from 34% to 60%, particularly from 40% to 58%

[0026] D70 / D95 ranges from 62% to 70%, particularly from 63% to 68%.

[0027] According to the convention 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. To calculate the values of D30, D70, and D95, or more generally any "DX" value, the particle size distribution by volume is preferably determined by dynamic image analysis (particularly according to ISO 13322-2). In particular, measurements are made using a Camsizer X2 (Retsch-Microtrac) device, and the quantity considered is X c Min, also known as the "minimum chord diameter". To make the measurement, the particles are suspended in air.

[0028] Aggregates, especially those with a size above 63 μm, preferably contain recycled aggregates, such as those from the demolition of buildings or infrastructure, industrial by-products, and / or sand from rock crushing. Examples include crushed demolition waste, foundry sand, and / or ground glass. Examples of demolition waste include fragments of concrete, mortar, gypsum, and glass. These different materials are usually crushed to the required size and thus have low roundness and sphericity. In other words, they are angular and rather elongated, different from river sand particles. The proportion of these materials, based on the weight of the aggregates, is preferably at least 50%, or even at least 60%.

[0029] The filler is preferably selected from limestone and dolomite fillers.

[0030] Based on the weight of the dry mortar composition, the total content of the hydraulic binder is preferably 1% to 40%, especially 5% to 30%, or even 10% to 20%.

[0031] The hydraulic binder can be a mixture of several hydraulic binders.

[0032] The hydraulic binder is preferably selected from Portland cement, high alumina cement, sulphoaluminate cement, slaked lime, slag (especially ground, granulated blast furnace slag), fly ash, and mixtures of two or more of these compounds. Portland cement particularly includes types CEM I and CEM II as defined by standard EN 197-1. CEM I cement contains at least 95% clinker, while CEM II cement contains at least 65% clinker and up to 35% blast furnace slag, fumed silica, pozzolan, fly ash, calcined shale, and / or limestone.

[0033] The hydraulic binder preferably consists of Portland cement, or is a mixture of Portland cement, high alumina cement, and a source of calcium sulphate (such as gypsum, hemihydrate, or anhydrite), optionally with the addition of ground, granulated blast furnace slag.

[0034] In a preferred embodiment, the hydraulic binder consists of Portland cement, high alumina cement, and a source of calcium sulphate. Based on the weight of the hydraulic binder, the binder preferably contains 5% to 40% Portland cement, 20% to 80% high alumina cement, and 10% to 50% source of calcium sulphate at this time. Such binders are particularly suitable for the preparation of self-levelling floor products, such as screeds.

[0035] The dry mortar composition preferably contains additives, especially in an amount in the range of 0.1% to 10% based on the weight of the dry mortar composition.

[0036] These additives are especially selected from plasticizers, superplasticizers, accelerators, retarders, defoamers, stabilizers, redispersible polymer powders, shrinkage reducing agents, rheology modifiers, and water reducing agents.

[0037] Examples of accelerators include alkali metal salts such as lithium (or potassium) sulfate or lithium (or potassium) carbonate, or organic salts such as calcium formate. The total amount of the accelerator is preferably from 0.001% to 0.5% by weight. Examples of retarders include carboxylic acids such as tartaric acid or citric acid, or their salts. Based on the weight of the dry mortar composition, the total amount of the retarder is preferably from 0.01% to 1.0% by weight. The dry mortar composition preferably contains both an accelerator and a retarder to control the setting and hardening of the hydraulic binder.

[0038] The stabilizer and water retention agent preferably comprise a cellulose ether. Based on the weight of the dry mortar composition, their content is preferably from 0.05% to 1.0% by weight.

[0039] The redispersible polymer powder is preferably obtained from at least one monomer selected from the group consisting of vinyl esters (in particular vinyl esters of branched or unbranched carboxylic acids containing 1 to 15 carbon atoms), (meth)acrylates (in particular (meth)acrylates of alcohols containing 1 to 10 carbon atoms), (meth)acrylic acid, aromatic vinyls, olefins such as ethylene or propylene, dienes and vinyl halides. In particular, the redispersible polymer powder suitable for the present invention is selected from polymer powders obtained from at least two of the above monomers, preferably selected from the following copolymer powders: ethylene-vinyl acetate copolymer, vinyl ester-ethylene-vinyl chloride copolymer, vinyl acetate copolymer, vinyl acetate-(meth)acrylate copolymer, copolymer of methyl methacrylate-n-butyl acrylate and / or 2-ethylhexyl acrylate, copolymer of methyl methacrylate-1,3-butadiene, vinyl chloride-ethylene copolymer, vinyl chloride-(meth)acrylate copolymer, styrene-butadiene copolymer, styrene-(meth)acrylate copolymer, vinyl acetate-(meth)acrylic acid-ethylene terpolymer. Based on the weight of the dry mortar composition, their content is preferably from 0.2% to 10% by weight, particularly from 0.5% to 5% by weight.

[0040] The dry mortar composition according to the present invention can be mixed with water to obtain a wet mortar, which is then cured to obtain a hardened mortar.

[0041] The mixing ratio, i.e., the weight of water relative to the weight of the dry mortar composition, is preferably from 8% to 28%.

[0042] Curing is preferably carried out in air at room temperature, i.e., without heating or cooling.

[0043] The hardened mortar is in particular a floor covering, such as a screed. These floor coverings are usually for indoor floors (inside a building), but they can also be for outdoor floors (belonging to a building but located outside, such as a balcony or terrace floor). The floor covering preferably has a thickness of 2 to 10 cm, particularly 3 to 8 cm.

[0044] Alternatively, the hardened mortar can be an exterior wall coating, an adhesive (such as a tile adhesive) or a joint filler. Examples

[0045] The following examples illustrate the present invention without limitation.

[0046] Different dry mortar compositions were obtained by mixing 13% CEM I 52.5 N cement, 0.1% additives (superplasticizer, thickener and viscosity modifier) and 87% aggregate.

[0047] The aggregate contains two types of sand (maximum size 4 mm) and limestone filler.

[0048] The median roundness (D50 in volume distribution) of the sand is 0.35 and the median sphericity is 0.84. Thus, these are relatively angular sands.

[0049] To obtain different particle size distributions, these sands and fillers were mixed in different proportions. The mixing ratio was 11 wt% of the dry mortar composition.

[0050] Table 1 below shows, for each tested composition, the proportion "P" of sand relative to the weight of the aggregate, the particle size volume distribution (size X c min, values from D10 to D95, in μm) determined by dynamic image analysis using a Camsizer X2 (Retsch-Microtrac), and the spread value "E", in mm (average of 3 measurements, spread measured after 3 minutes, using a ring with a diameter of 68 mm and a height of 35 mm).

[0051] [Table 1]

[0052]

[0053]

[0054] As can be seen from the table, comparative examples C1 and C2 with a particle size distribution not in accordance with the present invention have a spread significantly lower than that of Examples 1 to 4 according to the present invention. To achieve a spread value similar to that obtained in the comparative examples, the mixing ratio must be increased to a value of 13% to 15%, which impairs the mechanical strength of the hardened mortar.

[0055] Similar results were obtained by replacing the sand with ground glass having a median roundness of 0.09 and a median sphericity of 0.72. The spread values for particle size distributions outside the present invention are 90 to 100 mm, while the spread values for particle size distributions according to the present invention are 120 to 140 mm.

Claims

1. A dry mortar composition comprising a hydraulic binder and an aggregate, which comprises at least 50% by weight, based on the total weight of the aggregate, of an aggregate having a size above 63 μm, the aggregate having a size above 63 μm having a volume distribution of roundness such that the median roundness value is from 0.01 to 0.40, and the dry mortar composition having a volume-based particle size distribution such that the D30 / D95 ratio is from 4% to 15% and the D70 / D95 ratio is from 60% to 72%.

2. The composition according to claim 1, which does not contain particles larger than 4 mm.

3. The composition according to any one of the preceding claims, such that the median roundness value of the aggregate having a size above 63 μm is from 0.05 to 0.35, in particular from 0.10 to 0.

30.

4. The composition according to any one of the preceding claims, such that the aggregate having a size above 63 μm further has a volume distribution of sphericity such that the median sphericity value is at most 0.90, in particular at most 0.

85.

5. The composition according to any one of the preceding claims, wherein the total aggregate content is at least 50%, in particular at least 80% by weight, based on the weight of the dry mortar composition.

6. The composition according to any one of the preceding claims, wherein the proportion of the aggregate having a size above 63 μm is from 50% to 90% by weight, based on the total weight of the aggregate, in particular from 60% to 85%.

7. The composition according to any one of the preceding claims, wherein the aggregate, in particular the aggregate having a size above 63 μm, comprises recycled aggregate, such as from the demolition of buildings or infrastructure, industrial by-products and / or sand from rock crushing.

8. The composition according to the preceding claim, wherein the recycled aggregate is selected from crushed demolition waste, foundry sand and crushed glass.

9. The composition according to any one of the preceding claims, wherein the total hydraulic binder content is from 1% to 40%, in particular from 5% to 30% by weight, based on the weight of the dry mortar composition.

10. The composition according to any one of the preceding claims, wherein the hydraulic binder is selected from Portland cement, high alumina cement, sulphoaluminate cement, slaked lime, slag, fly ash and mixtures of two or more of these compounds.

11. The composition according to the preceding claim, wherein the hydraulic binder consists of Portland cement, or is a mixture consisting of Portland cement, high alumina cement and a source of calcium sulphate.

12. The composition according to any one of the preceding claims, such that the volume-based particle size distribution 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%.

13. The composition according to any one of the preceding claims, which further comprises an additive selected from plasticizers, superplasticizers, accelerators, retarders, defoamers, stabilizers, redispersible polymer powders, shrinkage reducing agents, rheology modifiers and water reducing agents.

14. A hardened mortar, in particular a floor covering, which is obtained by mixing the dry mortar composition according to one of the preceding claims with water to obtain a wet mortar, and then hardening the wet mortar.

15. The hardened mortar according to the preceding claim, which is a floor covering, in particular a screed.

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