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EP-4737424-A1 - POWDER COMPOSITION AND SPRAY CEMENT MORTAR CONTAINING THIS COMPOSITION

EP4737424A1EP 4737424 A1EP4737424 A1EP 4737424A1EP-4737424-A1

Abstract

The invention relates to a powder composition and a sprayed cement mortar containing cement and an admixture in the form of said powder composition. The powder composition according to the invention contains: (a) at least one dried and powdered anionic surfactant of formula (1), (b) at least one powdered moisture-retaining agent selected from poly(ethylene glycol), methoxy poly(ethylene glycol) or mixtures thereof, and (c) at least one powdered plasticizer of formula (2): (ROSO 3 - ) x M y+ (1) wherein the substituents in formula (1) are defined in the description.

Inventors

  • BRANDYS, Rafal
  • JAKOB, Alina

Assignees

  • PCC Exol Spolka Akcyjna

Dates

Publication Date
20260506
Application Date
20251029

Claims (20)

  1. A powder composition, characterized in that it contains: (a) at least one dried and powdered anionic surfactant of formula (1): (ROSO 3 - ) x M y+ (1) wherein: R is a linear and/or branched alkyl chain with an average number of carbon atoms of 8 to 16, x means 1 or 2, M y+ represents a mono- or divalent cation, wherein y = x in an amount of 1-28% by weight of the total weight of the composition, (b) at least one powdered moisture-retaining agent selected from poly(ethylene glycol), methoxy poly(ethylene glycol) or mixtures thereof, in an amount of 62-98% by weight of the total weight of the composition, and (c) at least one powdered plasticizer of formula (2): where n is the average number of oxyethylene monomers and ranges from 21 to 135 in the amount of 1-10% by weight of the total weight of the composition wherein the sum of all components of the composition is 100% by weight.
  2. The composition according to claim 1, characterized in that the moisture-retaining agent (b) has a weight average molecular weight (Mw) of 1000 Da to 12000 Da, determined in accordance with the method as described herein based on the DIN 55672-1 standard.
  3. The composition according to claim 2, characterized in that the moisture-retaining agent (b) has the weight average molecular weight (Mw) of 2000 to 8000 Da.
  4. The composition according to claim 3, characterized in that the moisture-retaining agent (b) has the weight average molecular weight (Mw) of from 2000 to 6000 Da.
  5. The composition according to one of claims 1-4, characterized in that the moisture-retaining agent (b) has water content of up to 6.0% by weight.
  6. The composition according to one of claims 1-5, characterized in that the content of the anionic surfactant (a) is from 1.0-20.0% by weight of the total weight of the composition.
  7. The composition according to one of claims 1-6, characterized in that the average number of carbon atoms in the alkyl chain R in formula (1) is from 10 to 16.
  8. The composition according to claim 7, characterized in that the average number of carbon atoms in the alkyl chain R in formula (1) is from 12 to 16.
  9. The composition position according to one of claims 1-8, characterized in that in formula (1) M y+ represents a cation selected from an ammonium cation and a metal cation selected from Na, K, Zn, Ca and Mg, or a combination of these cations.
  10. The composition according to claim 9, characterized in that in formula (1) M y+ represents a sodium or potassium cation.
  11. The composition according to one of claims 1-10, characterized in that the anionic surfactant (a) has water content of up to 6.0% by weight.
  12. The composition according to any one of claims 1-11, characterized in that the plasticizer (c) has the weight average molecular weight (Mw) of from 1000 Da to 6000 Da.
  13. The composition according to claim 12, characterized in that the plasticizer (c) has the weight average molecular weight (Mw) of from 2200 Da to 5500 Da.
  14. The composition according to one of claims 1-13, characterized in that the plasticizer (c) has water content of up to 6.0% by weight.
  15. The composition according to one of claims 1-5, characterized in that the content of the plasticizer (c) is from 2.0 to 8.0% by weight of the total weight of the composition.
  16. A sprayed cement mortar containing cement and an admixture, characterized in that the admixture is the powder composition according to any one of claims 1-15.
  17. The sprayed cement mortar according to claim 16, characterized in that the content of the powder composition in the mortar is up to 5% by weight relative to the weight of the cement, preferably up to 1% by weight relative to the weight of the cement.
  18. The sprayed cement mortar according to claim 16 or 17, characterized in that it is shotcrete.
  19. The sprayed cement mortar according to one of claims 16-18, characterized in that the minimum cement content in the mortar is 300 kg/m 3 , wherein the cement is a cement of class CEM I 42,5R, a cement of class CEM I 52,5R or a mixture thereof.
  20. The sprayed cement mortar according to one of claims 16-19, characterized in that the water -cement ratio w/c is in the range of 0.33 - 0.53.

Description

Field of invention The invention relates to a powder composition containing at least one anionic surfactant, at least one moisture-retaining agent and at least one plasticizing agent, as well as to a sprayed cement mortar containing this composition. The powder composition according to the invention finds use in particular as an admixture for sprayed cement mortars. State of the art The cement mortar and concrete are a type of composite created by mixing binder, aggregate, water, and various additives and admixtures that significantly influence its properties. The formula is determined based on specialized laboratory analyses to achieve, among other things, appropriate strength and resistance to external factors. Importantly, the parameters of concrete and cement mortars depend not only on their ingredients but also on the method of application and use. The mortars, or sprayed concrete, are materials used primarily for structural repairs. These materials are used to renovate concrete and reinforced concrete elements. The sprayed mortar (also referred to as shotcrete) is characterized by high resistance to abrasion and external atmospheric factors, and is also extremely resistant to carbonation. The sprayed mortar is a method called shotcreting, namely a rather specific method of applying a mixture using pneumatic spraying. This process involves spraying the mortar onto the surface at a high speed, which positively impacts the strength and effective sealing. Spraying is performed using a special machine - a shotcreting machine - and the method can be performed wet or dry. The wet method is primarily used when large quantities of sprayed material are required; it is effective and relatively inexpensive. The wet shotcreting involves transporting the prepared, moistened mixture to a special device, where it is sprayed onto a surface using compressed air. This method allows to avoid dusting and applying of too thin layers of material. The dry method, on the other hand, is recommended when ready-mixed concrete cannot be delivered quickly and in areas where the aesthetics of the finished surface are important. Dry shotcreting requires the addition of water to the mix only during the spraying stage. The dry cement and aggregate mixture is introduced into the machine and then transported through pipes to a spray nozzle, where it is moistened with water. Maintaining the correct water-to-mix ratio is crucial here, allowing for the desired density. Spraying allows the material to be applied to various hard-to-reach areas, such as ceiling surfaces. The mortar should be applied to the surface in circular motions, holding the nozzle at a right angle and approximately 1.5 m from the surface. The shaping possibilities of this material are virtually limitless, making it suitable for use in a variety of structures. Shotcreting is used in hydraulic structures, bridges, retaining walls, tunnels, and slopes; it is useful not only for constructing new structures but also for reinforcing existing structures. Currently, shotcreting encounters numerous challenges during both the spraying and subsequent setting stages. The sprayed mortars require appropriate rheology-modifying admixtures to facilitate pumping. The sprayed material must also exhibit adequate adhesion to the surface. The mortar cannot set too quickly or exhibit bleeding (water escaping from the cement mass), as this can cause cracking. Therefore, the admixture ingredients must be designed to ensure the final mortar has the appropriate viscosity and does not run off the sprayed surface. This presents a significant challenge for the mortar formulator, as the operator must handle the sprayed material efficiently and, equally importantly, as conveniently as possible. Some additives to the cement mixtures are known in the art. For example, the patent application US2019/0210921 A1 discloses a modified cellulose powder additive that allows for viscosity control, reduces cracking of the set material, and improves the homogeneity of fresh cement mixes. This application also discloses a composition containing such an additive/admixture. The patent application IN201921041082A describes a formulation for a multi-component superplasticizer based on polycarboxyether (PCE) that allows for control of workability, reduces concrete cracking, and increases its final strength. This publication describes the composition of the superplasticizer admixture. The patent application WO2008150604A1 discloses a composition for modifying the rheological properties of cement mortar, containing (i) a biopolymer, (ii) an anionic surfactant, and (iii) a cationic or amphoteric surfactant. In one embodiment, the composition contains sodium dodecyl sulfate as the anionic surfactant and further contains poly(ethylene glycol) as a further additive. Furthermore, the patent application CN114685085A describes an admixture for cement mortar prepared using wet technology, containing an anionic surfactant belongi