Tile adhesive designed for large format tiles

Abstract

The invention relates to a cementitious paste for fixing tiles having a dimension of at least 60 cm or more on a substrate, said cementitious paste comprising a hydraulic binder, aggregates, the overall bulk density of said aggregates being 500 kg / m3 or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, a film-forming polymer, and water, wherein the cementitious paste has a yield stress of 50 to 200 Pa and a hysteresis surface of 6,000 to 12,000 Pa.s-1, wherein the hysteresis surface is the area between the rising and falling curves of a shear stress-as-shear-rate plot generated from a Brookfield viscometer loop test.

Description

Title of the invention: Tile adhesive for large format tiles

[0001] The invention relates to cement-based tile adhesives. More specifically, it relates to tile adhesives suitable for laying large-format tiles used for floor and wall coverings.

[0002] Cement-based tile adhesives must meet a number of requirements concerning both ease of use during tile laying and the properties of the hardened mortar after laying. For example, EN 12004 requires a tensile strength of at least 0.5 N / mm² (Class C1 tile adhesive), or even at least 1 N / mm² (Class C2 tile adhesive), even after immersion in water, exposure to heat, or freeze-thaw cycles. The open time, which is the maximum time between coating the substrate with the adhesive and laying the tiles while maintaining a bond strength of at least 0.5 N / mm², must be at least 20 minutes, preferably at least 30 minutes for an extended open time tile adhesive, designated "E". Transverse deformation, according to standard EN 12004, is preferably at least 2.5 mm (deformability SI), or even at least 5 mm (deformability S2).Another important property is slip resistance, determined by measuring the downward movement of a tile applied to a combed adhesive layer on a vertical surface. This movement must be less than 0.5 mm for a "T" adhesive. Setting and hardening time, ease of application, consistency of the wet mortar, and the effort required for application are also parameters to consider.

[0003] Large-format tiles are tiles with a dimension of at least 60 cm or more, often reaching 90 cm, or even 120 cm and beyond. Their increasing popularity is due to their modern, clean aesthetic and their ability to visually enlarge a space. However, their installation presents unique challenges. Because of their large size, thinness, and greater weight compared to smaller tiles, large-format tiles require specialized handling and transport techniques. Tools such as suction cups are essential to prevent breakage and ensure precise positioning.

[0004] Fixing these tiles generally requires application to the back of the tiles, that is, applying tile adhesive to the back of the tiles in addition to the substrate to be covered, which increases the amount of adhesive used. This technique first of all ensures that at least 95% of the surface under the tile is covered by the tile adhesive, thus preventing cracking. When the tile is subjected to impact, it is important to prevent skinning during application. Fluid tile adhesives can also be used, but they are only suitable for floor applications and do not offer resistance to skinning. Additionally, vibrating tools are often used to facilitate tile setting by increasing adhesive coverage and eliminating air pockets trapped within the adhesive bed.

[0005] The invention aims to provide a cement-based tile adhesive that can be used to fix large format tiles on both walls and floors, ensuring complete coverage without back application and with the help of vibrating tools, preventing skin formation for longer periods and exhibiting good slip resistance, while retaining other acceptable and relevant properties for cement-based tile adhesives.

[0006] To this end, the invention relates to a cementitious paste for fixing tiles having at least one dimension of 60 cm or more on a substrate, said cementitious paste comprising a hydraulic binder, aggregates, the overall bulk density of said aggregates being 500 kg / m3 or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, a film-forming polymer, and water, in which the cementitious paste has a yield stress of 50 to 200 Pa and a hysteresis surface of 6,000 to 12,000 Pa.s*, in which the hysteresis surface is the area between the rising and falling curves of a plot of shear stress as a function of shear rate, generated from a Brookfield viscometer loop test.

[0007] Cementitious pastes behave like Bingham fluids. The yield stress (r0) of a Bingham fluid is the minimum shear stress required to initiate flow. Below this yield stress, the fluid behaves like a solid and does not deform. Once the yield stress is exceeded, the fluid flows, and a relationship is observed between the shear stress and the shear rate.

[0008] On the other hand, the hysteresis surface is related to the thixotropy of the paste, as indicated in Green, H. and Weltmann, RN, “Thixotropy” Vol. VI of “Colloid Chemistry”, J. Alexander, editor, New York, Reinhold Publishing Corp. (1946), pages 328-347. The larger the hysteresis surface, the more pronounced the thixotropic behavior of the paste.

[0009] The yield stress and the hysteresis surface are preferably determined as follows.

[0010] First, a cement paste is prepared by adding water to 1 kg of powder in the container of a planetary mixer conforming to EN 196. A first The mixture is mixed for 30 seconds, followed by a rest period of 1 minute. A second mixing is then performed for 1 minute, followed by another rest period of 2 minutes. A final mixing is then performed for 15 seconds. The resulting paste is immediately tested to measure the yield stress and hysteresis area.

[0011] Using a Brookfield RVT viscometer with a No. 7 spindle, at 22 °C and 55% RH, the rotational speed is increased from 0.3 to 100 rpm. More specifically, the rotational speed is increased in increments and takes the following values: 0.3, 0.5, 0.6, 1.0, 1.5, 2.0, 2.5, 3, 4, 5, 6; 10, 12, 20, 30, 50, 60, and 100 rpm. For each of these values, the rotational speed is maintained for 1 minute, and the torque is measured at the end of this period.

[0012] To determine the hysteresis surface, the rotational speed is then reduced from 100 to 0.3 rpm and the torque is measured at the same values: 60, 50, 30, 20, 12, 10, 6, 5, 4, 3, 2.5, 2.0, 1.5, 1.0, 0.6, 0.5 and 0.3 rpm. For each of these values, the rotational speed is maintained for 1 minute and the torque is measured at the end of this period.

[0013] Fig. 1 shows the evolution of the rotation speed N (in rpm) as a function of time t (in minutes).

[0014] The shear rate (in s1) and the shear stress (in Pa) are then determined respectively from the rotational speed and the torque, using the method described in P. Mitschka, Rheol. Acta 21, 207-209 (1982).

[0015] To determine the yield stress, the rising curve is fitted to the Herschel and Bulkley rheological model to obtain the yield stress. This model is based on the following equation, where r is the shear stress, r0 is the yield stress, y is the shear rate, and k and n are constants.

[0016] [Math.l] t = T0 + ky 23

[0017] The threshold stress can be determined using a smaller number of measurements, for example 5 or 10 measurements (instead of 18 as in the method described above), but it has been observed that a larger number of measurements improves the accuracy of the determination. Furthermore, the method described above allows both the threshold stress and the hysteresis surface to be determined from the same experiment.

[0018] For the determination of the hysteresis surface, a curve showing the evolution of the shear stress (in Pa) as a function of the shear rate (in s') is plotted. The curve includes an ascending curve and a descending curve forming a hysteresis loop, and the thixotropic surface is calculated as the area of ​​the hysteresis loop between the ascending curve and the descending curve, in other words terms such as the area between the ascending and descending curves on the plot of shear stress as a function of shear rate.

[0019] The inventors have demonstrated that a low yield stress flow as claimed provides good coverage, in particular at least 95%, when the tile is subjected to vibrations for a short period, for example 30 seconds. The yield stress is preferably between 50 and 180 Pa, in particular between 60 and 150 Pa.

[0020] Cementitious pastes with low yield stresses tend to have poor slip resistance. However, the inventors found that a large thixotropic surface area improves slip resistance. Surprisingly, it was possible to design a tile adhesive with both a low yield stress and high thixotropy.

[0021] The hysteresis area is preferably from 7,000 to 10,000 Pa.s*.

[0022] The viscosity of the cement paste at 5 rpm is preferably from 100 to 250 Pa.s, in particular from 150 to 200 Pa·s. The viscosity can be determined using a Brookfield RVT viscometer with a No. 7 spindle, at 22 °C and 55% RH. These values ​​ensure good paste flow.

[0023] The hydraulic binder preferably comprises components selected from ordinary Portland cement (OPC), calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), belitic cements, slags, fly ash, biomass ash and mixtures thereof.

[0024] The hydraulic binder preferably comprises, or consists of, slag (in particular ground granulated blast furnace slag - GGBS) and a cement selected from OPC, CAC, and CSA (in particular OPC). Most preferably, the hydraulic binder comprises, or is composed of, OPC and GGBS. The presence of ground granulated blast furnace slag improves the texture and lubricity of the wet mortar and reduces the effort required by the applicator. It also improves pull-off adhesion after immersion in water and after freeze / thaw cycles, as well as open time and transverse deformation.

[0025] The total quantity of hydraulic binder is preferably 30 to 60% by weight, in particular 40 to 55% by weight, or even 42 to 52% by weight, relative to the weight of the cement paste. When the hydraulic binder consists of OPC and ground granulated blast furnace slag, the weight ratio between OPC and slag is preferably 1:1 to 5:1, in particular 2:1 to 4:1.

[0026] The overall bulk density of the aggregates is 500 kg / m³ or less, preferably 470 kg / m³ or less, in particular 300 to 450 kg / m³ or 350 to 400 kg / m³. The bulk density of the aggregates is determined in accordance with according to standard EN 1097-3:1998. The overall bulk density of the aggregates is the bulk density of the mixture of all the aggregates contained in the cement paste.

[0027] To achieve these values, the cement paste contains lightweight aggregates, that is, aggregates having a bulk density of 900 kg / m³ or less. Indeed, it has been observed that lightweight aggregates make it possible to reduce the yield stress of the cement paste.

[0028] The total quantity of aggregates is preferably 5 to 30% by weight, in particular 8 to 25% by weight, or even 10 to 20% by weight, relative to the weight of the cement paste.

[0029] The aggregates may include aggregates having a bulk density greater than 500 kg / m³, provided that they also include lighter aggregates, so that the overall bulk density (i.e., the bulk density of the mixture of all the aggregates) is 500 kg / m³ or less. The aggregates may, for example, include heavy aggregates (i.e., having a bulk density greater than 900 kg / m³, or even greater than 1200 kg / m³), but their quantity is preferably less than 10% by weight, or even less than 8% by weight, or less than 6% by weight, or even less than 4% by weight, for example, 1 to 4% by weight, relative to the weight of the cement paste, in order to maintain a low overall apparent density. Heavy aggregates include, for example, silica sands and limestone fillers.

[0030] The maximum aggregate size is preferably 0.400 mm, and in particular 0.315 mm. The maximum size is determined by screening. It is defined as the smallest sieve size through which all the material passes.

[0031] As explained previously, the aggregates include lightweight aggregates. The lightweight aggregates are preferably selected from expanded perlite, expanded vermiculite, thermosetting polymer particles, spent catalyst particles, hollow silicate particles, and mixtures thereof.

[0032] Expanded perlite is a silica sand of volcanic origin, expanded by heat treatment. The perlite is preferably hydrophobic, as standard perlite absorbs water. The hydrophobic nature is obtained, in a known manner, by applying a coating to the surface of the particles. The bulk density of hydrophobic expanded perlite is preferably no more than 150 kg / m³, and in particular no more than 100 kg / m³.

[0033] The spent catalyst particles are preferably spent fluid catalytic cracking catalyst particles. The particle size is preferably less than 0.3 mm, preferably less than 0.1 mm. The bulk density of these particles is preferably 900 kg / m3 or less.

[0034] The thermosetting polymer powder has a maximum particle size that is preferably no more than 0.200 mm, in particular no more than 0.150 mm. The D50 (based on a weight distribution) is preferably no more than 0.100 mm. The bulk density of the thermosetting polymer is preferably no more than 500 kg / m³. The thermosetting polymer powder is preferably a micronized rubber powder, comprising in particular a vulcanized elastomer. It is preferably obtained by grinding used tires.

[0035] Hollow silicate particles are selected, in particular, from expanded glass beads and cenospheres. Cenospheres are hollow aluminosilicate particles produced during coal combustion in thermal power plants. The bulk density of cenospheres is preferably no more than 400 kg / m³, in particular no more than 350 kg / m³. Their maximum size is preferably no more than 0.315 mm. The bulk density of expanded glass beads is preferably no more than 500 kg / m³. Their maximum size is preferably no more than 0.100 mm.

[0036] A film-forming polymer is a polymer capable of forming a film by coalescence upon drying. The film-forming polymer preferably comprises at least one polymer based on one or more monomers selected from the group including vinyl esters (in particular, vinyl esters of unbranched or branched alkylcarboxylic acids having from 1 to 15 carbon atoms), methacrylates and acrylates (in particular, (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 polymer is preferably ethylene vinyl acetate.

[0037] The quantity of film-forming polymer is preferably 3 to 12% by weight, in particular 4 to 10% by weight, or even 5 to 9% by weight, relative to the weight of the cement paste.

[0038] The quantity of water is preferably 15 to 40% by weight, in particular 20 to 35% by weight, or even 25 to 30% by weight, relative to the weight of the cement paste.

[0039] According to a preferred embodiment, the cement paste comprises 15 to 40% by weight of water, 30 to 60% by weight of hydraulic binder, 5 to 30% by weight of aggregates, and 3 to 12% by weight of film-forming polymer. More preferably, the cement paste comprises 20 to 35% by weight of water, 40 to 55% by weight of hydraulic binder, 8 to 25% by weight of aggregates, and 4 to 10% by weight of film-forming polymer. Even more preferably, the cement paste comprises 25 to 30% by weight of water, 42 to 52% by weight of hydraulic binder, 10 to 20% by weight of aggregates and 5 to 9% by weight of film-forming polymer.

[0040] The cement paste comprises at least two rheology modifiers (a first and a second rheology modifier), the second also being a water retention agent.

[0041] The first rheology modifier is preferably a polymer. A preferred polymer is polyacrylamide. The amount of the first rheology modifier is preferably 0.005 to 0.1% by weight, in particular 0.03 to 0.07% by weight relative to the weight of the cement paste.

[0042] The polyacrylamide is preferably a nonionic polyacrylamide. These polyacrylamides are more effective at reducing the yield stress while increasing the thixotropic surface area, compared to ionic polyacrylamides (cationic and anionic), which tend to increase the yield stress. Its viscosity is preferably between 20 and 30 mPa·s (in a 2.5% water solution).

[0043] The second rheology modifier is preferably a cellulose ether. The cellulose ether is preferably an unmodified cellulose ether. It is preferably hydroxyethylmethylcellulose or hydroxypropylmethylcellulose, in particular having a viscosity of 5 to 30 Pa·s, preferably 10 to 15 Pa·s (in a 2% water solution). The amount of the second rheology modifier is preferably 0.05 to 0.50% by weight, in particular 0.10 to 0.40% by weight, or even 0.15 to 0.30% by weight relative to the weight of the cement paste. The second rheology modifier also acts as a water-retaining agent.

[0044] Polyacrylamide (in particular nonionic polyacrylamide), especially in combination with cellulose ether, has proven particularly useful for reducing yield stress while increasing the thixotropic surface area. Other rheology modifiers, such as starch ethers or guar ethers, increase the thixotropic surface area, but they also tend to increase yield stress.

[0045] The ratio between the quantity of first rheology modifier and the quantity of second rheology modifier (in particular the polyacrylamide / cellulose ether ratio) is preferably from 0.10 to 0.50, in particular from 0.15 to 0.40, or even from 0.20 to 0.30.

[0046] The cement paste preferably comprises fatty alcohols, in particular C16-C18 alcohols. Fatty alcohols further reduce the yield strength and increase thixotropy. In addition, fatty alcohols prevent skin formation and increase the setting time. The amount of fatty alcohols is preferably 0.05 to 1.0% by weight, in particular 0.1 to 0.4% by weight, relative to the weight of the cement paste. Other additives intended to reduce skin formation include citric acid, sugars, starch ethers, or sodium gluconate, but they are not preferred because they have a negative impact on thixotropy.

[0047] The cement paste preferably comprises a setting or hardening accelerator, such as calcium formate or sodium chloride. These may be present in quantities of 0.3 to 1.0% by weight, or 0.4 to 0.9% by weight, relative to the weight of the cement paste.

[0048] All the preferred embodiments described above can be combined. For example, a preferred cementitious paste comprises 30 to 60% by weight, in particular 40 to 55% by weight, of hydraulic binder (in particular comprising or consisting of OPC and GGBS), 5 to 30% by weight, in particular 8 to 25% by weight, of aggregates, the overall bulk density of the aggregates being 500 kg / m³ or less, 0.005 to 0.1% by weight, in particular 0.03 to 0.07% by weight of polyacrylamide (preferably nonionic polyacrylamide) and 0.05 to 0.50% by weight, in particular 0.10 to 0.40% by weight of cellulose ether, 3 to 12% by weight, in particular 4 to 10% by weight, of a film-forming polymer, and 15 to 40% by weight, in particular 25 35% by weight, water.

[0049] Another object of the invention is a cementitious paste comprising 30 to 60% by weight, in particular 40 to 55% by weight, of hydraulic binder, 5 to 30% by weight, in particular 8 to 25% by weight, of aggregates, the overall bulk density of the aggregates being 500 kg / m3 or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, 3 to 12% by weight, in particular 4 to 10% by weight, of a film-forming polymer, and 15 to 40% by weight, in particular 25 to 35% by weight, of water. The cement paste preferably comprises 0.005 to 0.1% by weight, in particular 0.03 to 0.07% by weight of polyacrylamide (preferably non-ionic polyacrylamide) and 0.05 to 0.50% by weight, in particular 0.10 to 0.40% by weight of cellulose ether.All the details given above for the paste components, in particular their nature and quantities, also apply to this cement paste and are not repeated here for the sake of brevity. Such a cement paste makes it possible to solve the aforementioned problems, and in particular to obtain good coverage and good slip resistance for large tiles, thanks to a low yield stress and a large hysteresis surface.

[0050] The invention also relates to a dry mortar composition for obtaining a cementitious paste according to the invention after mixing with water. The proportion of water (i.e., the weight of the water, expressed as a percentage, relative to the weight of the dry mortar composition) is preferably from 20 to 65%, in particular from 25 to 55%, or even from 33 to 43%.

[0051] Such a dry mortar composition comprises a hydraulic binder, aggregates, the overall bulk density of said aggregates being 500 kg / m³ or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, and a redispersible film-forming polymer powder. The dry mortar composition preferably comprises 40 to 85% by weight, in particular 55 to 80% by weight, of hydraulic binder, 7 to 45% by weight, in particular 10 to 35% by weight, of aggregates, the aggregates having an overall bulk density of 500 kg / m³ or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, and 4 to 20% by weight, in particular 5 to 15% by weight, of a redispersible film-forming polymer powder.The dry mortar composition preferably comprises 0.007 to 0.15% by weight, in particular 0.04 to 0.1% by weight of polyacrylamide (preferably non-ionic polyacrylamide), and 0.10 to 0.70% by weight, in particular 0.20 to 0.65% by weight of cellulose ether. All the details given above for the paste components, in particular their nature, also apply to this composition and are not repeated here for the sake of brevity.

[0052] The invention also relates to a method for fixing tiles on a substrate, said tiles having at least a dimension of 60 cm or more, said method comprising the application of the cement paste as described above on the substrate only, the application of said tiles on said substrate covered with said cement paste, and the application of vibrations on said tiles using a vibrating tool positioned on the tiles.

[0053] The tiles preferably have at least one dimension of at least 60 cm, preferably at least 90 cm, or even at least 120 or 300 cm. For example, the tiles are rectangles of 60x60 cm, 45x90 cm, 60x90 cm, 60x120 cm, 90x90 cm, 90x120 cm, 120x120 cm or 100x300 cm. The thickness of the tiles is, for example, 3 to 7 mm.

[0054] Tiles can be made from various materials, such as ceramics, stoneware, cement, stone, marble, glass, etc. Cement paste can, for example, be applied to the substrate using a glue comb, a trowel, a float or a notched spatula.

[0055] Vibrating tools are preferably handheld vibrators, plate vibrators, or pneumatic vibrators. The vibration frequency is preferably from 10 to 300 Hz, with higher frequencies being preferred as they better promote the flow of the cement paste.

[0056] Examples

[0057] The following examples illustrate the invention in a non-binding manner.

[0058] Cement pastes having the compositions indicated in Table 1 were prepared by mixing dry cementitious mixtures with water. Examples C1 and C2 are comparative examples, while Examples 1 and 2 are examples according to the invention. All values ​​are weight percentages relative to the weight of the cement paste.

[0059] [Tables 1] Cl C2 1 2 Cement, OPC CEM I 52.5 30.8 37.1 37.0 36.9 GGBS 3.8 11.4 11.4 11.4 Silica sand (<0.5 mm) 33.6 2.9 2.8 2.8 LWA 1 - 7.1 7.1 7.1 LWA2 - 1.4 1.4 1.4 LWA 3 - 3.6 3.6 3.5 Film-forming polymer 7.7 7.1 7.1 7.1 Calcium formate 0.8 0.7 0.7 0.7 First rheology modifier - - 0.05 0.05 Second rheology modifier 0.3 0.2 0.2 0.2 Fatty alcohols - - - 0.4 Water 23.1 28.5 28.5 28.4

[0060] GGBS is ground blast furnace slag in pellet form. LWA1 to LWA3 are lightweight aggregates. LWA1 was a spent fluid catalytic cracking catalyst having a bulk density of 900 kg / m³. LWA2 was recycled rubber (maximum size of 200 µm), having a bulk density of 320 kg / m³. LWA3 was hydrophobic perlite having a bulk density of 150 kg / m³. The silica sand has a bulk density of 1500 kg / m³. The overall bulk density of the aggregates was 390 kg / m³. The film-forming polymer is a copolymer of ethylene and vinyl acetate. The first rheology modifier was a nonionic polyacrylamide. The second rheology modifier and water retention agent was unmodified hydroxyethylmethylcellulose (15 Pa.s).

[0061] Table 2 presents the properties of these pastes. The stress, viscosity, and hysteresis area were determined as explained in this specification. The sliding resistance, adhesion values, and open time are also shown. The measurements were taken in accordance with EN 12004. Coverage corresponds to the area covered by the cementitious paste under a 60x60 cm² tile after 30 seconds of vibration using a conventional hand vibrator. Skin formation is assessed by applying the tile adhesive to a horizontal substrate, waiting 10 to 40 minutes or more, then applying a 5x5 cm² glass tile to the substrate, pressing the tile down with a 2 kg steel bar, and removing the tile to check whether any of the tile adhesive has transferred to the tile (indicating no skin formation). The value shown represents the maximum time during which no skin formed.

[0062] Figure 2 shows the shear stress r (in Pa) as a function of the rate of shear y (in s1) for example 2.

[0063] [Tables2] Cl C2 1 2 Density 1.25 1.10 1.10 1.07 Viscosity at 5 rpm (Pa.s) 356 314 188 185 Yield stress (Pa) 520 230 150 100 Hysteresis area (Pa.s') 5320 3790 8240 9720 Coverage (%) 60 70 >95 >95 Slip resistance (mm) 2 5 0.5 0 Adhesion (N / mm2) - Initial 2.00 2.00 2.00 2.00 - Immersion in water 1.40 1.78 1.50 1.67 - Freeze / thaw 1.28 1.50 1.55 1.62 - Hot storage 2.00 2.00 2.00 2.00 Skin formation (min) 15 to 20 15 to 20 15 to 20 >45 Open time (N / mm2) - 20 min 1.10 0.98 1.05 0.98 - 30 min 0.65 0.55 0.75 1.55

[0064] The pastes according to the invention showed greater coverage and better resistance to slippage while maintaining good adhesion values.

Claims

Demands

1. Cementitious paste for fixing tiles having at least one dimension of 60 cm or more on a substrate, said cementitious paste comprising a hydraulic binder, aggregates, the overall bulk density of said aggregates being 500 kg / m3 or less, a first rheology modifier, a second rheology modifier which is also a water retention agent, a film-forming polymer, and water, wherein the cementitious paste has a yield stress of 50 to 200 Pa and a hysteresis surface of 6,000 to 12,000 Pa.s', wherein the hysteresis surface is between the rising and falling curves of a shear stress versus shear rate plot, generated from a Brookfield viscometer loop test.

2. Cementitious paste according to claim 1, wherein the hydraulic binder comprises components selected from ordinary Portland cement, calcium aluminate cement, calcium sulfoaluminate cement, belitic cements, slags, fly ash, biomass ash and mixtures thereof.

3. Cl. Cement paste according to any one of the preceding claims, wherein the aggregates comprise aggregates selected from expanded perlite, expanded vermiculite, thermosetting polymer particles, spent catalyst particles, hollow silicate particles, and mixtures thereof.

4. Cement paste according to any one of the preceding claims, wherein the first rheology modifier is a polymer, in particular a polyacrylamide.

5. Cement paste according to any one of the preceding claims, wherein the second rheology modifier is a cellulose ether.

6. Cement paste according to any one of the preceding claims, comprising 15 to 40% by weight of water, 30 to 60% by weight of hydraulic binder, 5 to 30% by weight of aggregates and 3 to 12% by weight of film-forming polymer.

7. Cement paste according to any one of the preceding claims, further comprising fatty alcohols.

8. Cement paste according to any one of the preceding claims, further comprising a setting or hardening accelerator.

9. Cement paste according to any one of the preceding claims, wherein the yield stress is from 50 to 180 Pa.

10. Cement paste according to any one of the preceding claims, wherein the hysteresis surface is from 7,000 to 10,000 Pa.s*.

11. Cement paste according to any one of the preceding claims, having a viscosity at 5 rpm of 100 to 250 Pa.s, in particular 150 to 200 Pa.s.

12. Dry mortar composition adapted to obtain a cementitious paste according to the preceding claims after mixing with water.

13. A method for fixing tiles to a substrate, said tiles having at least a dimension of 60 cm or more, said method comprising applying the cement paste according to any one of claims 1 to 11 to the substrate only, applying said tiles to said substrate covered with said cement paste, and applying vibrations to said tiles using a vibrating tool positioned on the tiles.

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