ITMI990727A1 - SUPERFLUIDIFYING ADDITIVE FOR CEMENTITIOUS COMPOSITIONS - Google Patents

Description

Description of the Industrial Invention entitled:

Superplasticizing additive for cementitious compositions "

Field of the invention

The present invention relates to a superplasticizer additive for cementitious compositions, characterized in that it comprises an acrylic superplasticizer in combination with a cationic additive. Technical problem

To meet the specific requirements during the installation phase of cementitious products, such as low water / binder ratio, high initial fluidity, maintenance of workability over time - and to give the products the desired characteristics - such as high compressive strength, durability, accurate surface finish - the use of superfluidifying additives is indicated.

Acrylic superfluidifiers are particularly appreciated as they have a high fluidifying action even at low water / binder ratios, and maintain the workability of the mixture for periods of time sufficient for the installation of the products, where the application includes packaging, transport and casting. of the cementitious composition (eg concrete).

The use of acrylic superfluidifiers is appreciated not only on gray cements, but especially on white cements; in fact, in the case of white cements, traditional super-plasticisers such as those based on naphthalenesulphonate or lignosulfonate lead to significant variations in the typical brightness of the resulting cementitious products.

Apparently indicated for their color seem the melamine products; however, they are sometimes unsuitable from the point of view of performance, since, in combination with white cements, they have an unsatisfactory fluidifying action already at the initial processing times. The superplasticizers with an acrylic structure have a sufficiently light color to keep the degree of whiteness of the hardened cement surfaces practically unaltered, however sometimes they can prove unsatisfactory.

In fact, their fluidifying action, despite being high even at low water / cement ratios (for example w / c <0.40), may be limited to the mixing period only, with significant losses in workability occurring within a very short time ( 5-10 minutes) from the dough.

This problem is graphically illustrated in Figures 1, 2, and 3, which report the workability data over time of pulp, mortar and concrete samples, respectively, admixed with acrylic superplasticizers. Furthermore, as can be seen in figure 12, the problem of loss of workability cannot be solved by increasing the dosage of the acrylic superplasticizer: on the contrary, the sample containing the highest dose of acrylate (indicated with the symbol - ♦ -), although possessing a high workability at zero time, shows a greater loss of workability compared to the sample containing less fluidifying or the non-fluidized one.

The loss of workability can also manifest itself as a considerable stickiness of the fluid mass, which does not allow carrying out the operations of transport, unloading and skilful installation of the concrete. The remedy traditionally used in this situation consists in adding more water to the cement mixture; however, this proves to be counterproductive as it leads to a greater porosity of the consolidated mass, and therefore ultimately to cements with lower mechanical performance and more exposed phenomena of moisture infiltration, degradation, corrosion of the reinforcements, etc.

On the basis of the limitations of the prior art highlighted above, the need for new efficient superfiuidifying systems for cements is evident. In particular, the need is felt for superfiuidifiers capable of meeting the requirements of fluidity and workability of cementitious compositions that show a significant loss of workability over time with the use of acrylic fluidifiers.

Summary

Now the Applicant has unexpectedly found that the drawbacks of the known superfiuidifying additives mentioned above can be overcome by using an additive system consisting of an acrylic superplasticizer, in combination with an ammonium salt corresponding to the structural formula (I), a surfactant and possibly an antifoam additive. .

This additive system, in the form of a multicomponent superfluidifying additive, constitutes a first object of the invention. The present also includes cementitious compositions with high fluidity and workability, containing an acrylic superfluidifier, an ammonium salt described by the structural formula (I), a surfactant, and optionally an antifoam additive.

Further aspects of the present invention are represented by premixes in the dry state and cementitious articles, containing an acrylic superfluidifier, an ammonium salt of formula (I), a surfactant, possibly an antifoam additive, and the relative preparation procedures, as well as the use of the aforementioned additive system in the fluidization of cement mixtures.

Description of the Figures

Figure 1 (comparison): shows the cone yield values of white cement based pastes (Italbianco ®) containing an acrylic additive, expressed as the diameter of the cone of the paste as a function of time:

- · -: paste containing the acrylic additive Mapefluid <®> X-404

- ♦ -: paste containing the acrylic additive Glenium <®> 51.

Figure 2 (comparison) shows the consistency of a sample of white cement-based mortar (Italbianco ®), as a function of time, in comparison with the same mortar added with acrylic superplasticizers: - · -: mortar as it is; water / binder = 0.62

- ♦ -: 1.0% mortar Tupole <®> SSP 104; water / binder = 0.36

- * -: 1.0% Mapefluid * X 404 mortar; water / binder = 0.40 Figure 3 (comparison) shows the values of yield to the cone of concrete based on Italbianco ® white cement, added with two different acrylic additives, expressed as a decrease in the height of the cone as a function of time.

- ■ -: concrete containing 2% Glenium <®> 51; water / binder = 0.43;

- ▲ -: concrete containing 4% of Mapefluid <®> X-404; water / binder = 0.45.

Figures 4. 5 and 6 show the consistency values as a function of time of mortars prepared respectively with three different cements (two Italbianco ® white cements and a gray 52.5 R cement), added as follows:

- Figure 4:

- ♦ - comparison: Italbianco ® 1% white cement mortar Mapefluid <®> X-404; water / binder = 0.45

- ■ -: Italbianco ® white cement mortar premixed with 0.3% of A0 1% formulation Mapefluid <®> X-404; water / binder = 0.45

- Figure 5:

- ♦ - comparison: Italbianco ® white cement mortar 1.2% Mapefluid <®> X-404; water / binder = 0.47

- A -: Italbianco ® white cement mortar premixed with 0.3% of A0 formulation; water / binder = 0.47

- ■ -: Italbianco ® white cement mortar premixed with 0.2% of A0 1% formulation Mapefluid <®> X-404; water / binder = 0.47

- Figure 6:

- ♦ - comparison: gray cement mortar 52.5 R 1% Mapefluid <®> X-404; water / binder = 0.45

: 52.5 R gray cement mortar premixed with 0.4% formulated A0 1% Mapefluid <®> X-404; water / binder = 0.45

Figures 7. 8 and 9 show the cone yield values of concrete, expressed as a reduction in the height of the cone as a function of time: - Figure 7 shows the data of Table 5, relating to concrete samples obtained by premixing the A0 formulation with cement Italbianco ®: samples 1, 2 and 3 contain the acrylic additive and formulation A0, and sample C1 the only formulation A0:

- ♦ -: sample 1; - □ -: sample 2;

- A -: sample 3; - X -: sample C1.

- Figure 8 shows the data of Table 6, relative to samples obtained by mixing the metakaolin pre-added with formulation A0 with white cement: the samples 5-8 contain the acrylic additive and the formulation A0, and the samples C2-C3 the only formulated A0:

- ♦ -: sample 5; - □ -: sample 6;

- ■ -: sample 7; - · -: sample 8;

- A -: sample C2; - X -: sample C3;

- Figure 9 shows the yield values at the cone of Table 6, relative to the concrete samples 7 and 8 mentioned above, in comparison with a sample of concrete added only with the acrylic additive:

- ■ -: sample 7; - · -: sample 8;

- X -: sample added with only the acrylic additive (3% acrylic additive; water / binder = 0.4).

Figures 10 and 11 show the compressive strength values of concrete specimens, as a function of time:

- Figure 10 shows the data of Table 7, relating to concrete samples obtained by premixing the A0 formulation with Italbianco ® white cement: the samples 1, 2, 3 and 4 contain the acrylic additive and the A0 formulation, and the sample C1 the only formulated A0:

■: sample 1; □: sample 2;

: sample 3; B: sample 4; EB: sample C1;

- Figure 11 reports the data of Table 8, relating to concrete specimens obtained by pre-dispersing the A0 formulation in the metakaolin: E2: sample 5; □: sample 6; M: sample 7; days: sample 8; sample C3.

Figure 12 (comparison ^

Consistency of a sample of white cement based mortar (Italbianco ®) as a function of time in comparison with the same mortar added with acrylic superplasticizer:

- A - mortar t.q. a / c = 0.60;

- ■ - 1% super-plasticising acrylic mortar (Superflux 2000AC), water / cement ratio = 0.45;

- ♦ - 1.3% acrylic superplasticizer mortar (Superflux 2000AC), water / c ratio = 0.41.

Figures 13. 14. 15 and 16

Consistency as a function of time (workability curve) of white cement-based mortar samples (EXAMPLE II), packaged at the same w / c ratio = 0.45 and added with the additive system in comparison with the same mortar added only with superplasticizer acrylic.

Fig. 13

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Superflux 2000AC);

- ♦ - mortar added with 0.3% formulated A1 1% acrylic superplasticizer (Superflux 2000AC);

- ▲ - mortar added with 0.3% formulated A2 0.8% acrylic superplasticizer (Superflux 2000AC).

Fig. 14

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Mapefluid X404);

- A - mortar added with 0.3% A3 formula 1% acrylic superplasticizer (Mapefluid X404);

- ♦ - mortar added with 0.3% A4 1% acrylic superplasticizer (Mapefluid X404);

- X - mortar added with 0.3% A5 formulation 1% acrylic superplasticizer (Mapefluid X404).

Fig. 15

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Mapefluid X404);

- ♦ - mortar added with 0.3% A6 formulation 1% acrylic superplasticizer (Mapefluid X404);

- A - mortar added with 0.3% A7 formulation 1% acrylic superplasticizer (Mapefluid X404);

Fig. 16

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Mapefluid X404);

- ▲ - mortar added with 0.3% A8 formulation 1% acrylic superplasticizer (Mapefluid X404);

- ♦ - mortar added with 0.3% A9 formulation 1% acrylic superplasticizer (Mapefluid X404).

Figures 17 and 18

Consistency as a function of time of 52.5 R gray cement-based mortar samples (EXAMPLE III), packaged at the same w / c ratio = 0.45 and added with the additive system in comparison with the same mortar added only with acrylic superplasticizer.

Fig. 17

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Superflux 2000AC);

- ♦ - mortar added with 0.5% formulated A1 0.5% acrylic superplasticizer (Superflux 2000AC).

Fig. 18

- ■ - Comparison: mortar added with 1% acrylic superplasticizer (Superflux 2000AC);

- ♦ - mortar added with 0.5% formulated A10 0.5% acrylic superplasticizer (Superflux 2000AC);

- A - mortar added with 0.5% formulated A11 0.5% acrylic superplasticizer (Superflux 2000AC).

Figure 19

Slump loss of a sample of concrete based on white cement (EXAMPLE IV), packaged at the same water / c ratio 0.38 and added with the additive system in comparison with the same concrete added only with acrylic superplasticizer.

- ■ - Comparison: concrete added with 2.5% acrylic superplasticizer (Mapefluid X404);

- ▲ - Concrete with the addition of 0.65% of A5 2% acrylic superplasticizer (Mapefluid X404).

Detailed description of the invention

The object of the present invention is an additive system for cementitious compositions, comprising at least one acrylic superplasticizer, at least one ammonium salt of formula (I), at least one surfactant, and optionally at least one antifoam additive.

The first element of the present additive system consists of one or more ammonium salts corresponding to the following structural formula (I):

where is it:

R1, R2, R3, independently of each other, are chosen from:

■ hydrogen,

■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, preferably from 1 to 16.

■ a polyoxyalkylene chain containing n repetitive units of structural formula (11), and m repetitive units of structural formula (III)

where m and ri, independently of each other, are integers between 0 and 50, and {m n) is an integer between 2 and 50, and where said units can be present in random order in said chain.

■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, preferably from 12 to 18, optionally substituted with one or more polyoxyalkylene chains as defined above.

and R4 is chosen from:

■ a structure group - (CH2) p N R5 R6, where p is between 1 and 7, and in which R5 and R6 can be, independently of each other: (i) hydrogen, (ii) linear alkyl groups either branched, saturated or unsaturated, having from 1 to 22 carbon atoms, or (iii) a polyoxyalkylene chain as defined above;

■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 12 carbon atoms, preferably from 1 to 4;

and where X <-> is an anion which neutralizes, partially or totally, the charge of the ammonium ion.

Preferred X <-> ions for the purposes of the invention are the hydroxide ion and the R7-COO <-> ion, in which R7 is a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, preferably from 9 to 20, such as the oleate, stearate or linoleate ion.

The ammonium salt of structure (I) is obtained by partial or total salification of an amine by a protonic acid, used in any molar ratio.

Preferred ammonium salts according to formula (I) are those in which the cation is represented by: triethylammonium, tetramethylammonium, hexadecyltrimethylammonium, or ammonium ions derived from an ethoxylated primary amine and containing a C14-C18 alkyl chain, such as for example products marketed by D.A.C. with the name Diammin.

The aforementioned polyoxyalkylene chains are linked to the compound of formula (I) by means of the oxygen atom of the last oxyethylene (II) or oxypropylene (III) unit, while the terminal unit at the other end of the chain has structure CH3-CH2- O- (in the case of oxyethylene chains) or CH3-CH2-CH2-O- (in the case of oxypropylene chains).

Preferably, the polyoxyalkylene chain consists of n units of formula (II), where n is comprised between 2 and 15.

When R4 is a structure group - (CH2) p N R5R6, the nitrogen atom that is part of it can, depending on the environmental pH, be in neutral form, as shown above, or in the ammonium ion form - (CH2) P NH <+> R5Re. In this case the compound of formula (I) appears as a divalent di-ammonium cation.

A preferred class of ammonium salts included in the general formula (I), is that in which the ammonium ion responds to the structural formula (la)

where R5, and n have the meanings indicated above; preferably R5 is a linear or branched, saturated or unsaturated alkyl group containing from 8 to 22 carbon atoms. The ammonium ion (la) is partially or totally neutralized by the anion X <->, where X has the meanings described above. Also the derivatives of formula (la) can also be present in the above indicated form of di-ammonium salts, ie where also the nitrogen atom bound to R5 is in protonated form.

Preferred ammonium salts of formula (la) are the diamine dioleates, marketed by the company C.E.C.A. with the name Inipol.

The second element of the additive system object of the invention consists of one or more surfactants. The surfactant can be any surfactant, anionic, cationic, amphoteric or non-ionic.

Preferably, a non-ionic surfactant is used, with a hydrophilic-lipophilic balance value (HLB) between 5.5 and 15. Among the non-ionic surfactants, those having a polyoxyethylene and / or polyoxypropylene structure can be mentioned, in particular those containing from 2 to 9, for example 5 or 6 units of ethylene oxide, generally alkoxylated at at least one end of the polymeric chain, for example mono-ethers of polyoxyethylene glycol with a fatty alcohol, having for example from 8 to 22 carbon atoms, or with a phenol optionally substituted with at least one C8-C22 alkyl residue, for example nonyl. Examples of non-ionic surfactants useful for the purposes of the present invention are nonylphenol polyoxyethylene having 5 ethylene oxide units, marketed by CONDEA Chimica D.A.C. with the name Nonfix 5, and nonylphenol polyoxyethylene having 6 ethylene oxide units, marketed by WITCO Chimica D.A.C. with the name Syntopon A.

Further examples of non-ionic surfactants are alcohols, preferably linear, ethoxylated with 3-8 moles of ethylene oxide, or isodecyl alcohol ethoxylated with 4-8 moles of ethylene oxide. These products are marketed by D.A.C under the name Biodac® (e.g. Biodac 2/32).

Among the anionic surfactants we can mention Fenopon <®> 128 (GAF), having the structure R8O (CH2CH2O) n-1CH2CH2OSO3 <-> NH4 <+>; examples of cationic surfactants are the compounds of formula R8N (CH3) 2CH2C6H5 .Cl <-> (R8 is H or C1-C4 alkyl), marketed by the ECSC as Noramium <®>.

The third element of the additive system object of the invention consists of one or more acrylic superplasticizing additives. This class includes additives containing polymers, terpolymers or copolymers of acrylic or methacrylic acid, or of other carboxylic acids or relative anhydrides containing a polymerizable ethylene unsaturation (for example fumaric, oleic, itaconic, crotonic, aconitic, synapic, mesaconic, undecylenic acids , angelic, hydroxy-acrylic, maleic anhydride), or of the relative salts or esters, and their mixtures.

Examples of acrylic polymers and copolymers useful for the purpose of the present invention are mentioned below, with the bibliographic references describing them, incorporated by reference in the present patent application:

- copolymers between a) acrylic or methacrylic acid and b) a hydroxy- (C2-C3) -alkyl ester of acrylic or methacrylic acid, described in EP-A-303,747;

- mixtures comprising at least one copolymer of alkenyl ethers of formula (I), at least one polyalkenyl ether of formula (II), and maleic anhydride, the relative hydrolysis products or the salts of said hydrolysis products, described in EP-A-619.277;

- superplasticizing additives obtained by terpolymerizing the monomers of formula (IV), (V) or (VI), described in EP-A-612.702;

- copolymers of formula (I) described in JP 6048797;

- salts of polymers formed by reaction of a polycarboxylic acid with an acrylic polymer containing nitrogen, typically in aqueous solution, described in FR 2.656.297;

- polymeric compositions of a monoester of maleic acid with a compound of formula (I), and of a monomer of formula (II), defined in FR 2.668.773;

- copolymers in the form of free acids or salts, containing three types of monomers, defined in FR 2.671.090;

- dispersing agents comprising water-soluble vinyl copolymers obtained by radical copolymerization in aqueous solution between monomers of formula (1), (2), (3), (4), and (5), described in EP-A-590.983;

- water-soluble vinyl copolymers, represented by linear copolymers between vinyl acetate and N-substituted maleamic acid, having formula (A), described in EP-A1 -604.676;

- copolymers between monomers A), B), C) and D), defined in EP-A1 -610.699;

- polymers or copolymers of ethylene carboxylic acids selected from acrylic, methacrylic, fumaric, aleic, itaconic, crotonic, aconitic, synapic, mesaconic, undecylenic, angelic, hydroxy-acrylic, and maleic anhydride acids, described in FR-A1 -2.699.915 ;

- an additive for controlling the fluidity of cementitious compositions, containing at least one copolymer between a monomer a) of an ester of monomethacrylic acid of alkylene glycol having formula (I) and a monomer b) of a methacrylic acid of formula (II), or a copolymer between monomer d) based on a monomethylallyl ether of alkoxypolyalkylene glycol of formula (III) and monomer b) based on methacrylic acid of formula (IV), defined in FR -A1 -2.706.447;

- copolymers or relative salts containing i) 33-95% by moles of a carboxylic acid with polymerizable ethylene unsaturation, and ii) 67-5% by moles of a carboxylic acid ester with polymerizable ethylene unsaturation, as described in US 5,047,087 and in US 4,473,406, wherein the unsaturated carboxylic acid is preferably acrylic, methacrylic, crotonic, fumaric, itaconic, citraconic, aconitic or maleic acid.

The acrylic additive is, for example, chosen from the commercial products listed below, together with the manufacturer and, where available, the type of polymer or copolymer contained therein and the bibliographical references relating to their structure and preparation, incorporated by reference herein. application: Mapefluid <®> X-404 (Mapei, poly (ethylene oxide) and copolymer of sodium methacrylate and poly (ethylene oxide) methacrylate, E P-A-612.702); Tupole <®> SSP-104 (Takemoto Oil & Fat, terpolymer composed of sodium acrylate, sodium methacrylate and poly (ethylene oxide), EP-A-590.983); Darex Super <®> 200 (Denka Grace, copolymer between ethylene oxide and maleic anhydride, EP-A-0619277); Narlex <®> LD-36V and LD-38SF (National Starch, acrylic acid copolymers, USP 4,473,406); Glenium <®> 51 (MAC-MTB, polycarboxylic acid ethers, FR-2.656.297), Sokalan <®> HP 80 (BASF).

Other examples of commercial acrylic-based additives useful for the purposes of the present invention are Cimfluid <®> 2000 AC (AXIM, poly (ethylene oxide) and copolymer of sodium methacrylate and poly methacrylate (ethylene oxide); PPE 1179 ( National Starch & Chemical, acrylic acid copolymers, partially neutralized with triethanolamine); CAD-8000 (Kao Corporation); Tupole <®> HP-11 (Takemoto Oil & Fat, polycarboxylic acid); CM1142 (Sketch); Superflux ® 2000 AC (Italeux, poly (ethylene oxide) and copolymer of sodium methacrylate and poly methacrylate (ethylene oxide)).

The additive system object of the invention preferably contains at least one antifoam additive. The antifoam additive can be selected from various antifoam additives for cements, for example it is a copolymer between ethylene oxide and propylene oxide units, etherified at the beginning of the polymer chain with a C2-C20 aliphatic alcohol, as described in the application for international patent PCT / EP97 / 00026 in the name of the same Applicant, having in particular a molecular weight about 1050, a unit ratio of propylene oxide / ethylene oxide equal to 3, etherified with an aliphatic alcohol having from 10 to 14 carbon atoms , typically 13, such as for example the product Aìrplast <®>, marketed by Hispano Quimica.

Furthermore, the antifoam additive can be a polymer of direct condensation between stearic acid and propylene oxide, such as the product Koster ® K / 9 P, marketed by D.A.C.

Further objects of the invention consist of: highly fluidity and workability cementitious compositions containing the additive system described above, and their preparation process; dry premixes containing the additive system described above, suitable for forming the aforesaid cementitious compositions; cementitious products made from the aforementioned cementitious compositions; use of the additive system described above in the fluidization of cementitious compositions.

In the present text, cementitious compositions are understood to be cementitious mixtures comprising at least one hydraulic binder, water, and possibly: one or more inert aggregates, and / or one or more mineral additions, and / or fibers for cements, and / or one or more conventional additives. The term hydraulic binder refers to a material in the form of a powder, in the dry state, which when mixed with water, provides plastic mixtures capable of solidifying and hardening over time. For cements we mean in particular those included in the UNI ENV 197.1 standard.

The cementitious compositions are divided into pastes (compositions without inert aggregates) and conglomerates (compositions containing at least one inert aggregate). The conglomerates in turn are divided into mortars (containing fine aggregates such as sand), and concretes (containing both fine aggregates and coarse aggregates such as gravel, pebbles, crushed stone, chosen for example from those classified according to the UNI 8520 standard ). The present invention is directed in particular to mortars and concretes.

By mineral addition we mean any type of finely divided inorganic material that can be added to concrete to impart better characteristics of mechanical strength and durability.

The additions can be inert, pozzolanic or with latent hydraulic activity.

For the purposes of the present invention, preferred mineral additions are metakaolin, limestone, fly ash, slag, pozzolan (natural and artificial) and fine silica.

Cement fibers can be natural or artificial, inorganic or organic. Examples of natural inorganic fibers are: asbestos, sepiolite, wollastonite; examples of natural organic fibers are: cotton, wool, jute, linen, hemp, sisal, cellulosic fibers; inorganic artificial fibers are constituted for example by: glass, rock, slag, basalt, ceramics, calcium silicate, silicon carbide, carbon; artificial organic fibers can be constituted for example by: nylon, rayon, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene.

Further fibers for cements can be of a metallic nature, for example steels.

Conventional additives are those normally contained in cementitious compositions, such as for example: retardants, setting accelerators, water reducers, pumping aids, corrosion inhibitors. A further object of the present invention are dry premixes containing the superplasticizing additive described above. Dry premisceiati are dry state compositions which, by adding water, are directly converted into cementitious compositions ready for installation. Therefore the dry premixes comprise at least one hydraulic binder as defined above, and optionally: one or more inert aggregates, fibers for cements, and / or one or more mineral additives, and / or conventional additives, as defined above.

Further examples of conventional additives are: shrinkage compensators, aerating agents, water retention agents (eg cellulose ethers), retardants or accelerators. By cementitious products we mean articles obtained from cementitious compositions formed, placed in place and left to harden.

Particular embodiments of the present invention are represented by cementitious compositions, cementitious manufactured articles, dry premixes, containing the additive object of the invention and at least one photocatalyst capable of oxidizing in the presence of light, air and ambient humidity the polluting substances present in the environment.

In these cementitious compositions, cementitious products or dry premixes, the photocatalyst is preferably represented by titanium dioxide or a precursor thereof, mainly (for example for at least 70%) in anatase form. Preferably, the photocatalyst is uniformly distributed in the entire cement mass; in this case the resulting cementitious articles contain the photocatalyzer in their entire mass, avoiding the need to apply cementitious coatings containing it. Examples of premixes, compositions and manufactured articles containing photocatalyst particles in bulk are those described in the international patent application WO 98/06601 (PCT / EP97 / 04008), incorporated by reference in the present application.

The high fluidity and workability cementitious compositions object of the present invention contain the components of the additive system preferably in the following percentages by weight, referred to the weight of the hydraulic binder in the dry state:

ammonium salt: 0.04% to 1%, more preferably 0.12% - 0.30%; surfactant: between 0.04% and 1%, more preferably 0.12% -0.30%; antifoam agent: between 0.02% and 0.3%, more preferably 0.06 -0.15%. acrylic superplasticizer: from 0.3% to 3%, more preferably between 0.5% and 2.5%.

The additive system object of the invention is preferably made in the form of two separate formulations A) and B), which can be added separately to the cementitious compositions, where:

- Formulation A) includes the ammonium salt of formula (I), the surfactant, and possibly the antifoam additive;

- formulation B) includes the acrylic superplasticizer.

Typically the formulation A) contains the following relative weight quantities of ammonium salt a), surfactant b) and antifoam c): from 2 to 6 parts by weight, for example 4 parts by weight of a); from 2 to 6 parts by weight, for example 4 parts by weight of b); 1 to 4 parts by weight, for example 2 parts by weight of c). In order to obtain a volume of additive such as to facilitate the operations of incorporation into the cements, formulation A) can be added to suitable quantities of the filling material ("mineral addition", for example metakaolin) required to prepare the cementitious compositions or premixes .

The preparation of the cementitious compositions takes place according to conventional methods and equipment, mixing the hydraulic binder and the remaining ingredients with water, typically in ambient conditions, for example at a temperature between about 10 ° C and 40 ° C, for example at 157 + 25 ° C.

The elements of the additive system are incorporated into the cement mixtures at any stage of their preparation, preferably in the form of two separate fractions (formulations A and B).

The temperature at which the formulation A) is added depends on the viscosity of the formulation itself. In case of high viscosity, formulation A) can be previously heated to a temperature generally between 30 ° C and 40 ° C.

Formulate A) is preferably premixed with the hydraulic binder in the dry state, or with a mineral filling material in the dry state, before mixing with water, and adding the remaining ingredients.

Preferably, the formulation A) is dry pre-dispersed in a mineral filling material ("filler"), such as metakaolin, and the resulting material is then uniformly dispersed in the hydraulic binder.

In particular, the formulation A), can be premixed with the total amount of filling material required for the packaging of the cementitious mixture, which varies for example from 5% to 15% by weight, typically it is about 10% by weight on the basis of weight of the hydraulic binder in the dry state.

Preferably, the formulation A) is added to an aliquot of the total filling material required for the mixture, called "mother", variable for example from 1% to about 5%, for example equal to about 2.5% by weight based on the weight of the hydraulic binder in the dry state.

The pre-dispersion of formulation A), in an aliquot of filling material, allows to considerably reduce the volumes of materials to be premixed, while also facilitating the subsequent homogenization phase with the cement.

The homogenization of the "mother" with the cement, and the possible addition of mineral fillers (aggregates and mineral additions) can also be done directly in the concrete mixer, by pre-mixing all the solid components of the cement composition dry for about 2-3 minutes. , and subsequently adding the quantity of water and formulation B) (acrylic superplasticizer) necessary for the packaging of the composition.

This system is even more advantageous because it allows the handling of small volumes of mineral charge and is suitable for the production of concrete in both fixed and mobile mixers (truck mixer).

Formulation B) (acrylic additive) is preferably incorporated into the cement mixture at the end, as the last ingredient, being typically added to the mixing water, which is preferably added in portions to the cement mixture containing the remaining ingredients.

The superfiuidifying compositions according to the present invention have the following unexpected advantages:

- allow to obtain cement mixtures, for example concrete, with satisfactory workability and fluidity characteristics both at the initial processing times, which subsequently, for at least 30-45 minutes, corresponding in particular to a workability according to class S4 of the UNI 9858 standard for at least 30-45 minutes;

- they allow to use low water / binder weight ratios, in particular not higher than 0.4, for example of about 0.35-0.4 parts by weight of water per part by weight of cement (hydraulic binder) in the dry state;

- allow to obtain cementitious compositions, in particular concretes, endowed with high mechanical resistance, having for example compressive strength values at 1, 2, 7 and 28 days equal respectively to at least 35, 50, 65, 70 Mpa, typically comprised between 35 and 40 Mpa at 1 day, between 45 and 55 Mpa at 2 days, between 50 and 60 Mpa at 3 days, between 60 and 70 Mpa at 7 days and between 70 and 85 Mpa at 28 days.

- in particular, they allow to obtain unexpectedly higher mechanical strengths after 28 days compared to samples containing only formulation A, for example compressive strengths at 28 days equal to at least 70 Mpa;

- allow to obtain cementitious compositions, in particular concretes, with density values equal to at least 2400 Kg / m <3>, corresponding to air contents lower than 1% volume / volume.

The percentage of air was calculated on the basis of the density values determined according to UNI 6394 part 1 <a>.

Some examples are reported below for illustrative but not limitative purposes of the present invention.

EXPERIMENTAL PART EXAMPLE I: Tests in concrete

Materials

1. Cement: Italbianco ® CEM 52.5 R (Italcementi), having the chemical analysis reported in Table 1 350 kg / m <3> TABLE 1 Cement CEM 52.5R ITALBIANCO ® (ITC)

p / p = weight / weight

1A. Water / binder ratio: This text refers to the weight ratio between the mixing water and the sum of the cement and any metakaolin or other filling material.

2. Aggregates:

light white Apuan marble from the Carrara area, divided into 10 distinct sizes; continuous grain size curve, with maximum grain size = 20 mm 1900 kg / m <3> 3. Mineral fillers:

metakaolin Metastar <®> 501 ECC: 10% by weight on the cement = 35 kg / m <3> 4. Photocatalyst:

titanium dioxide A-HR <®> micron Tioxide 7 Kg / m <3> 5. Superplasticizer composition:

A) Formulation A0, liquid;

% weight / weight with respect to dry cement: 0.5% -1, 3% B) Formulate B: commercial acrylic additive Mapefluid <®> X-404;

% weight / weight compared to dry cement: 1, 5% -2.0% C) small quantities of antifoam Airplast <®> 251

Equipment:

1.For the preparation of premixes:

- "blendor" mixer with 1 liter glass (Waring)

- 5 liter intensive mixer (Eirich).

2, For concrete packing:

- 50 liter concrete mixer, with vertical axis with rotary movement.

Method of adding additives to the dough:

a) Dry premixing of formula A with cement:

in a laboratory "blendor" sufficient quantities of cement were prepared for the preparation of the concrete. All the cement necessary for the mixture was added with formula A.

b) Predispersion of formulation A in the metakaolin:

Two distinct methodologies were adopted, using a laboratory "blendor";

i) in the first case, formulation A was dispersed in the entire volume of metakaolin necessary for the packaging of the concrete (10% by weight on the cement);

ii) in the second case, formulation A was dispersed in lower quantities of metakaolin, equal to 5% and 2.5% by weight on the cement in the dry state. The metakaolin thus added was then mixed with the cement necessary for the preparation of the concrete using an Eirich intensive mixer.

- Formulated B (acrylic superplasticizer:

Additive B was added directly to the concrete mixer as the last component, together with the antifoam agent.

Comparative cementitious compositions containing only the acrylic additive (formulate B).

Various samples of cementitious compositions based on Italbianco ® (Italcementi) white cement (pastes, mortars and concretes) were prepared, containing only the acrylic additive, and comparative compositions without this additive, having the characteristics specified above in the relative legends. in Figures 1, 2 and 3.

Concrete containing the multicomponent additive system of the present invention (formulation A formulation B) and comparative compositions containing only formulation A.

Various concrete samples were prepared by mixing the hydraulic binder and the remaining ingredients with water, in the quantities indicated above, under ambient conditions (about 20 ° C / + 30 ° C).

The dosage of additives, referred to commercial products as such, and the water / hydraulic binder ratio are shown in Tables 2 and 3 relating to the two procedures for adding formulate A described above. Samples 1 to 8 are concrete samples according to the present invention; samples C1, C2, and C3 are comparative concrete samples, containing only the additive A, without acrylic superplasticizer.

TABLE 2 - Dry premixed cement with formula A

TABLE 3 Dry premixed cement with metakaolin previously added with formula A

Analysis of the characteristics of the doughs

Fresh state tests: Determinations of density, cone yielding over time, and vibration behavior were carried out, determined on concrete mixes prepared as described above, in the fresh state (i.e. within about 60 minutes from mixing with water of the relative ingredients).

The density was determined according to UNI 6394 part 1 <a>.

The vibration behavior was determined by visually assessing the degree of segregation of the doughs.

The loss of workability was assessed by measuring the yield to the cone ("slump test") according to UNI 9418, at the times indicated in the Table.

Table 4 reports the density values, in Kg / m <3>, and vibration behavior, expressed as excellent, good, sufficient, or poor.

TABLE 4

Legend: ++ very good + good enough> poor

Results

- The density value was generally higher than 2400 kg / m <3>, corresponding to an air content of less than 1% volume / volume.

The vibration behavior was on average good, only for a few mixtures sufficient.

The comparison samples C1-C3 exhibit an unsatisfactory vibration behavior, or in any case lower than that of the concrete samples containing the superplasticizing composition according to the present invention.

Cone settlement: The cone settlement values, expressed as a reduction in the height of the concrete cone in centimeters, are shown in Tables 5 and 6 and presented in the graph in Figures 7, 8 and 9.

TABLE 5 - Premixed dry cement with formulation A

TABLE 6 - Dry premixed cement with metakaolin added with formulation A

Results

- The use of formulation A in combination with the acrylic additive B has significantly reduced the loss of workability over time, which can be found with the use of acrylic B only, as illustrated in Figure 9.

- The use of 0.65% A 1.8% B, with A dry premixed with cement or metakaolin, allowed the concrete to be kept in consistency class S4 for up to about 45 minutes.

- It was possible to operate with a water / binder ratio <0.4

Tests in the hardened state

Compressive strength - Various concrete samples were prepared according to UNI 6127. The compressive strength was determined according to UNI 6132-72.

The results obtained are reported in Tables 7 and 8, and in Figures 10 and 11.

TABLE 7

Dry premixed cement with formula A

TABLE 8

Dry premixed cement with metakaolin added with formula A

<**> not deformable at expiry 24 h

Comment on the results

The concretes prepared with the super-plasticising composition comprising 0.65% A 1.8% B, in which A was premixed with metakaolin, showed compressive strengths at 1, 2, 3 and 7 days respectively equal to 36 ÷ 40, 52 ÷ 57, 56 ÷ 61 and 66 ÷ 73 Mpa, with compressive strength at 28 days equal to or greater than 75 Mpa.

After 1 day, the strength is 10-15% lower than that of a concrete of the same composition and the same water / binder ratio (at 20 ° C). However, already at 30 hours the values are similar, of the order of 45 Mpa (at 20 ° C).

It is important to note that the comparison samples containing only formulation A show compressive strength values at 28 days significantly lower than those of the samples according to the present invention, containing both formulation A and B.

Retarding effect: formulation A alone in a quantity of 1.3% (sample C3) gives setting / hardening delays such as not to allow the demoulding of the samples after 24 hours. At 40 hours the resistances are lower than those of specimens containing 0.65% of A 1.8% of B (samples 6,7,8) packaged with water / cement ratios equal to or even higher.

Sample C3 at 2 days exhibits a compressive strength Re lower than that of samples 6,7,8 at 24 hours.

The use of formulation A has made it possible to use acrylic superplasticizers in white cement based mixtures, eliminating the drastic loss of workability observed in the first 10 minutes of processing with the use of only acrylic additive B.

Under the experimental conditions adopted, the optimal dosage of the two products was: 0.65% A 1.8% B, which made it possible to maintain the concrete in consistency class S4 for up to about 45 minutes.

The positive results obtained by dry premixing formulation A with an aliquot of metakaolin, equal to 2.5% by weight of the cement, are of considerable importance for the industrial application of the superplasticizing compositions studied: with this method of addition, the volumes of metakaolin to be added in fact, with A they undergo a significant reduction, and at the same time the homogenization in the plant of the "mother" thus obtained with the cement is made more effective.

The properties of the additive system according to the invention can be further highlighted in the following examples I and III, which refer to consistency measurements over time carried out according to the UNI 7044 standard. These measures constitute an index of the workability of the cement mixtures. Example IV refers to cone settlement measures according to UNI 9418, in concrete.

EXAMPLE II

It consists of a series of mortar tests.

Each mortar was packaged with the following ingredients:

■ 450 g. white cement OEM 52.5R (Italbianco ®);

■ 1350 g. aggregate: light white marble from the Carrara area, divided into two sizes, 0-1 mm and 1-3 mm.

The mortars were prepared according to EN 196/1, using a Hobart mixer.

The results, expressed as workability curves, are shown in the graph in figures 4,5, and 13-16.

Each mortar was added with the additive system with a fluidifying effect consisting of:

■ formulated A0, dry premixed with cement in a laboratory “Blendor”;

■ an acrylic superfìuidifìcante, always added to the mixing water. The dosages of additives are expressed as a percentage by weight with respect to the weight of the cement.

Formulation A was prepared at the time of use, mixing the components in the relative percentage ratios indicated in tab. 9.

The components used in the formulations are commercial products.

The ammonium salts of formula (I) object of the invention are made by mixing the components 1 and 2 indicated in the table. The AO formulation contains an ammonium salt of formula (la) consisting of a diamine dioleate (commercial product with the name INIPOL 002).

Tab. 1 - Composition of the formulations

EXAMPLE III

It consists of a series of tests in mortar.

Each mortar was packaged with the following ingredients:

■ 450 g. gray cement OEM I 52.5R (Ultracem);

■ 1350 g. of aggregate: standardized German type silica sand, compliant with ENI 196/1.

The methods of preparing the mortars and adding additives are the same as those used in example I.

The results are shown in the graph in figures 6 and 17-18.

EXAMPLE IV

It consists of a concrete test.

The concrete was packaged with the following ingredients:

■ 350 Kg / m <3> of white cement CEM 52.5R (Italbianco ®);

■ 1900 Kg / m <3> of aggregate: light white marble from the Carrara area, divided into ten distinct sizes; continuous grain size curve, with maximum grain size equal to 20mm;

■ 35 Kg / m <3> Mineral fillers: metakaolin Metastar 501 ECC;

■ 7 Kg / m <3> Photocatalyst: titanium dioxide A-HR micron Tioxide. The A5 formulation was premixed with metakaolin. The acrylic superplasticizer was added to the mixing water.

The result is shown in the graph in fig. 19.

Claims (22)

CLAIMS 1. Superplasticizing additive for cementitious compositions comprising: (i) at least one ammonium salt of formula (I), in which R1, R2, R3, independently of each other are chosen from: ■ hydrogen, ■ a branched linear O alkyl group, saturated or unsaturated, having from 1 to 22 carbon atoms, ■ a polyoxyalkylene chain containing n repetitive units of structural formula (II), and m repetitive units of structural formula (III) where m and n, independently of each other, are integers between 0 and 50, and (m n) is an integer between 2 and 50, and where said units can be present in random order in said chain. ■ an alkyl group, linear or branched, saturated or unsaturated, having from 1 to 22 carbon atoms, optionally substituted with an O plus a polyoxyalkylene chains as defined above. R4 is chosen from: ■ a group of structure - (CH2) P N R5 R6 where p is between 1 and 7, and in which R5 and R6 can be, independently of each other: (a) hydrogen, (b) linear alkyl groups or branched, saturated or unsaturated, having from 1 to 22 carbon atoms, or (c) a polyoxyalkylene chain as defined above. ■ a linear or branched alkyl group, saturated or unsaturated, having from 1 to 12 carbon atoms; X <-> is an anion which neutralizes, partially or totally, the charge of the ammonium ion; (ii) at least one on acrylic peri uidifier, (iti) at least one surfactant, e (iv) optionally one or more antifoam additives. 2. Additive according to claim 1, where the substituents R1, R2, R3, in formula (I), independently of each other, are selected from: ■ hydrogen, ■ a linear or branched alkyl group, saturated or unsaturated, having from 1 to 16 carbon atoms, ■ a polyoxyalkylene chain as defined above, where m is equal to 0, and n is between 2 and 15. ■ an alkyl group, linear or branched, saturated or unsaturated, having from 12 to 18 carbon atoms, possibly substituted with one or more polyoxyalkylene chains as defined above, where m is equal to 0, and n is between 2 and 15. 3. Additive according to claim 1, where the ammonium ion represented in formula (I) is selected from: triethylammonium, tetramethylammonium, hexadecyltrimethylammonium, or an ion of formula (la), where R5 and n have the meanings indicated above 4. Additive according to any one of claims 1-3 where X-represents at least one anion selected from OH <-> and R7-COO, wherein R7 is an alkyl group, linear or branched, saturated or unsaturated, having from 1 to 22 carbon atoms. 5. Additive according to claim 4, where X <-> represents at least one anion selected from oleate, stearate or linoleate. 6. Additive according to any one of claims 1-5, wherein the surfactant (iii) is a non-ionic surfactant having a hydrophilic / lipophilic balance (HLB) between 5.5 and 15. 7. Additive according to any one of claims 1-6, formulated in two separate compositions A) and B), having the following composition: Formulate A): containing the ammonium salt (i), the surfactant (iii), and optionally the antifoam additive (iv); Formulation B): containing the acrylic superplasticizer (ii). 8. Additive according to claim 7, wherein the formulation A) is diluted with inert filling material. 9. High fluidity and workability cementitious composition comprising a hydraulic binder, water, and a superplasticizing additive containing: (i) at least one ammonium salt of formula (I), in which R2, R3, independently of each other, are chosen from: ■ hydrogen, ■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, ■ a polyoxyalkylene chain containing n repetitive units of structural formula (II), and m repetitive units of structural formula (III) where m and n, independently of each other, are integers between 0 and 50, and {m n) is an integer between 2 and 50, and where said units can be present in random order in said chain ■ a group alkyl, linear or branched, saturated or unsaturated, having from 1 to 22 carbon atoms, optionally substituted with one or more polyoxyalkylene chains as defined above; R4 is chosen from: ■ a structure group - (CH2) P N R5R6, where p is between 1 and 7, and in which R5 and R6 can be, independently of each other: (a) hydrogen, (b) linear or branched alkyl groups , saturated or unsaturated, having from 1 to 22 carbon atoms, or (c) a polyoxyalkylene chain as defined above, ■ a linear or branched alkyl group, saturated or unsaturated, having from 1 to 12 carbon atoms; X <-> is an anion which neutralizes, partially or totally, the charge of the ammonium ion; (ii) at least one acrylic superplasticizer, (iii) at least one surfactant, e (iv) optionally one or more antifoam additives. 10. Cementitious composition according to claim 9, containing the following percentages by weight of components, referred to the weight of the hydraulic binder in the dry state: from 0.04% to 1% of ammonium salt (I); 0.04% to 1% surfactant (iii); from 0.02% to 0.3%, of antifoam additive (iv); from 0.3% to 3% of acrylic superplasticizer (ii). Cementitious composition according to any one of claims 9-10, wherein the hydraulic binder is a white cement. Cementitious composition according to any one of claims 9-11, further containing particles of compounds having photocatalytic action. 13. A cementitious composition according to claim 12, wherein the photocatalytic compound is titanium dioxide or a precursor thereof, mainly in anatase form. 14. Cementitious composition according to any one of claims 9-13, represented by a concrete or a mortar. 15. Cementitious composition according to any one of claims 9-14, with a water / hydraulic binder weight ratio not higher than 0.4. 16. Process for the preparation of a cementitious composition with high fluidity and workability, characterized by mixing together a hydraulic binder, the additive described in claim 1, and water in a suitable quantity to make a fluid mixture. 17. Process according to claim 16, wherein the additive is used in the form of two separate formulations A) and B) having the following composition: A): containing the ammonium salt (i), the surfactant (iii), and any antifoam additive (iv), possibly mixed with inert filling material; B): containing the acrylic superplasticizer (ii). 18. Process according to claim 17, comprising the following steps: a- mix the formulation A) with the hydraulic binder in the dry state; b- disperse the formulation B) in the mixing water; c- add the mixture obtained in b- to the mixture obtained in a-, mixing until homogeneous. 19. Process according to any one of claims 16-18, in which a water / hydraulic binder weight ratio lower than or equal to 0.4 is used. 20. Premixed in the dry state for cementitious compositions, comprising at least one hydraulic binder, and a superplasticizing additive containing: (i) at least one ammonium salt of formula (I), in which R1 (R2, R3, independently of each other, are chosen from: ■ hydrogen, ■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, ■ a polyoxyalkylene chain containing n repetitive units of structural formula (II), and m repetitive units of structural formula (III) where m and n, independently of each other, are integers between 0 and 50, and (m n) is an integer between 2 and 50, and where said units can be present in random order in said chain. ■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, optionally substituted with one or more polyoxyalkylene chains as defined above; R4 is chosen from: ■ a structure group - (CH2) p N R5R6, where p is between 1 and 7, and in which R5 and R6 can be, independently of each other: (a) hydrogen, (b) linear alkyl groups 0 branched, saturated or unsaturated, having 1 to 22 carbon atoms, or (c) a polyoxyalkylene chain as defined above, ■ a linear or branched alkyl group, saturated or unsaturated, having from 1 to 12 carbon atoms; X <-> is an anion which neutralizes, partially or totally, the charge of the ammonium ion; (ii) at least one acrylic superplasticizer, (iii) at least one surfactant, e (iv) optionally one or more antifoam additives and / or particles of compounds having a photocatalytic action. 21. Cement product, placed and hardened, containing the additive for cements described in claim 1, and possibly particles of compounds having a photocatalytic action. 22. Use of an additive comprising: (i) at least one ammonium salt of formula (I), in which R1 R2, R3, independently of each other, are chosen from: ■ hydrogen, ■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, ■ a polyoxyalkylene chain containing n repetitive units of structural formula (11), and m repetitive units of structural formula (III) where m and n, independently of each other, are integers between 0 and 50, and (m n) is an integer between 2 and 50, and where said units can be present in random order in said chain. ■ a linear or branched, saturated or unsaturated alkyl group, having from 1 to 22 carbon atoms, optionally substituted with one or more polyoxyalkylene chains as defined above; R4 is chosen from: ■ a structure group - (CH2) p N R5R6, where p is between 1 and 7, and in which R5 and R6 can be, independently of each other: (a) hydrogen, (b) linear alkyl groups or branched, saturated or unsaturated, having from 1 to 22 carbon atoms, or (c) a polyoxyalkylene chain as defined above, ■ a linear or branched alkyl group, saturated or unsaturated, having from 1 to 12 carbon atoms; X <'> is an anion that neutralizes, partially or totally, the charge of the ammonium ion; (ii) at least one acrylic superfluidifier, (iii) at least one surfactant, e (iv) optionally one or more antifoam additives as a superfluidifìcant for cements.