Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/06—Aluminous cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
  • C04B38/02—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by adding chemical blowing agents
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
  • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• EP 2069257 A2 Concrete composition with reduced shrinkage, priority date the 20 th September 2006.
• the documents A1 and A2 describe the so-called Chemical Prestressed Reinforced Concrete (CPRC), but this material, despite having been obtained with expansive agent added to the mixture, does not contain fibers inside the cement mixture, and therefore the 'prestress effect' works only thanks to the effect of external constraint offered by the reinforcing metal bars (the classic rods for reinforced concrete). But such concentrated metal reinforcement does not allow to fully exploit the prestress effect, as it involves only a small portion of material, that is the thin layer of expansive concrete that is in the immediate vicinity of the steel bars. In theory, a uniformly distributed fibrous reinforcement on the entire portion of the material in tension would be much more effective.
• CPRC Chemical Prestressed Reinforced Concrete
• Toutanji in A8 showed that the presence of expansive cement and polypropylene fibers with an elastic modulus of 8 GPa did not give rise to any type of synergy. Also in A9 the use of low modulus polypropylene fibers (less than 10 GPa) did not allow any self-prestress effect (the prestress referred to in the document is given by steel cables).
• Huang et al. in the document A10 studied a cement mixture to produce shotcrete containing both expansive agent and short metallic fibers. They noted some improvement in flexural strength without reaching absolute values above 7 MPa after 28 days of wet curing.
• Cao et al. (A12) produced high strength lightweight mixture by using both short fibers and expansive agent. They observed a good behavior in terms of mechanical strength development, but without reaching absolute values above 1 1 .2 MPa after 28 days of wet curing, even if the compression resistance after 28 days was equal to 62.7 MPa (with a ratio between bending strength and compressive strength equal to 0.18).
• Document A13 in the name of the same applicant, describes the composition of a mixture comprising the following materials (proportions by weight): hydraulic binder comprising cement (1000 parts), and expanding agent (45-180 parts); granular material with dimension (D50) greater than 0.200 mm and dimension (D90) less than 5.0 mm (600-2900 parts); fibers with an elastic modulus greater than 50 GPa (25-400 parts); water (250-550 parts); water reducing admixture (10-100 parts); any kind of filler with particles smaller than 0.200 mm (0-300 parts).
• the object of the present invention is to solve the drawbacks of the prior art by providing a cementitious composition which is able to ensure high tensile strength with improved rheological properties with respect to the cement-based compositions of the prior art.
• the composition of a cementitious mixture according to the invention is expressed by claim 1 .
• the mixture proportion of the cementitious composite, according to the invention represents an innovation with respect to that described in document A13, since the mixture according to the invention contains a new ingredient consisting of colloidal silica.
• This mixture allows an excellent flowability of the mixture to be obtained at the fresh state, in the absence of bleeding and segregation phenomena. In fact it has been studied for optimizing the rheological behavior of the cementitious composite, while maintaining the self- prestress effect, and therefore the same advantages described in the mixture of document A13 in terms of mechanical performance in tension.
• the mixture proportion of the cementitious composite comprises the following materials:
• the mixture can also include:
• the cement-based hydraulic binder can be any type of cementitious hydraulic binder commonly available on the market, as for example Portland cement, aluminous cement or supplementary cementitious materials. If you use Portland cement, the hydraulic binder dosage that can vary from 215 to 950 kg per cubic meter of mixture.
• the dry granular inert material is sand or gravel, which is ground and sieved with a sieve, so as to obtain dimensions (D90) less than 5.0 mm.
• the expansive agent is commonly available on the market.
• the expansive agent known under the brand Stabilmac ® from BASF Construction Polymers GmbH can be used.
• the expansive agent may contain one or more of the following oxides:
• the expansive agent is preferably ground to a fineness comparable to that of the hydraulic binder, with particles smaller than 0.200 mm.
• Fibers have high elastic modulus, higher than 20 GPa; fibers can have any shape or geometry; fibers are coated or uncoated; fibers are treated or untreated with sizing; fibers can have either natural or artificial or recycling origin (coming from the recovery and treatment of industrial waste or byproducts).
• Fibers can be either randomly disposed or oriented; fibers can be either homogenously dispersed or concentrated in particular zone; fibers can be either single or held together with any technique; fibers can form textiles of any geometry comprising non-woven fabric; fibers can form either 2D-textiles or 3D- textiles, both kinds made with any technique, such as for example the technique described in the document A14.
• the water reducing admixture is commonly available on the market. For example, you can use the water reducing admixture known under the brand Melflux ® from BASF Construction Polymers GmbH.
• the water-reducing admixture may be a polycarboxylic compound, comprising a polycarboxylate ether-based superplasticizer (PCE).
• PCE polycarboxylate ether-based superplasticizer
• the content of material with particles smaller than 0.200 mm decreases from a maximum value of 300 parts up to a maximum value of 200 parts, and at the same time the expansive agent content (another substance with particles smaller than 0.200 mm) decreases from 45-180 parts to 5-130 parts.
• the maximum overall content of particles smaller than 0.200 mm (including the hydraulic binder, 1000 parts) has dropped from 1480 parts to 1330 parts with a decrease of 10%;
• fiber elastic modulus has been lowered from 50 GPa to 20 GPa, in order to include high modulus polymeric fibers such as, for example, PVA fibers.
• A17 in which 2.5% by weight of nanosilica has been used on cement-based mixture, but in reality A17 is more focused on the study of the influence of the addition of colloidal silica on the setting time of cement paste, and there isn't comparison with other nanosilica (or silica fume) introduced in the mixture as a powder instead of aqueous suspension.
• the mixture proportion of the cement-based composite, according to the invention, was based on a series of experimental data never published or disclosed, some of which are given below as an example.
• mixtures A, B, C and D have a composition included into intervals defined in A1 3, while mixture E contains all the ingredients reported in the claims of the present patent application, according to the claimed dosage ranges; with the exception of the fibers. Fibers, however, can not be introduced into the rheometer, and they simply constitute the carried phase, therefore they have no influence on the rheology of the carrying phase, i.e. the cement-based matrix.
• mixture A shows a negative value of the yield stress. Therefore, the cohesion of this mixture, corresponding to a rotation speed equal to zero, is negative; as a consequence: the mixture has internal segregation, as confirmed by the relative mortar.
• the mixture E is the only one able to combine the requirements of high flowability and absence of segregation.
• Mixtures shown in the example illustrate the invention without limiting it.
• Limestone filler 100 100 100 50 - -
• the values of mechanical strength obtained have been measured after 1 , 7 and 28 days of wet curing at 20°C, on three 40 by 40 by 160 mm specimes for each curing time, according to the procedure described in the EN 1015-1 1 standard.
• the 'SPC-1 ' mixture described in A13 presents an evident synergic effect between fiber and expansive agent with an increase in the bending mechanical strength after 1 day of curing equal to +135% (more than double) with respect to the corresponding mixture prepared with the only fibers without expansive agent.
• the mixture 'SPC-1 ' is borderline for being defined as Self Prestressed Concrete (SPC), in the sense that it has performances close to the minimum limits as defined in A13 to be SPC, which are:
• the mixtures 'New-A' and 'New-B' comply with the criteria defined in A13 to be called Self-Prestressed Concrete (SPC), but they present the additional requirements of both fluidity and internal cohesion, i.e. an improved rheological behavior.
• SPC Self-Prestressed Concrete
• 'New-A' and 'New-B' mixture proportions are not included within the range of the mixture claimed in A13, but they are included within the composition range claimed in the present patent.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 2018
  • 2018-10-18 EP EP18789408.4A patent/EP3707110A1/de active Pending
  • 2018-10-18 MA MA050550A patent/MA50550A/fr unknown
  • 2018-10-18 WO PCT/EP2018/078623 patent/WO2019091751A1/en unknown

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