Admixtures to improve the workability of cementitious compositions comprising supplementary cementitious materials

Abstract

The present invention relates to admixture comprising a first polycarboxylate ether, a second polycarboxylate ether which is chemically different from said first polycarboxylate ether, and at least one alkanolamine. The use of said admixtures to improve the workability of cementitious compositions comprising supplementary cementitious materials, and to cementitious compositions, especially concrete, comprising the same.

Description

[0001] ADMIXTURES TO IMPROVE THE WORKABILITY OF CEMENTITIOUS COMPOSITIONS COMPRISING SUPPLEMENTARY CEMENTITIOUS MATERIALS

[0002] Technical Field

[0003] The present invention relates to admixture to improve the workability of cementitious compositions comprising supplementary cementitious materials and to cementitious compositions, especially concrete, comprising the same.

[0004] Background of the invention

[0005] The reduction of cement clinker usage is a major contributor to a more sustainable concrete. During the manufacture of Ordinary Portland cement clinker, a high amount of carbon dioxide is released to the environment. The reduction of Ordinary Portland cement clinker used in concrete, for example by replacement of Ordinary Portland clinker by supplementary cementitious materials (SCM) is therefore desirable.

[0006] Various SCM are known and include granulated blast furnace slag, fly ash, metakaolin, and other pozzolanic and / or latent hydraulic materials. High replacement levels of Ordinary Portland cement in concrete by suitable SCM are desirable.

[0007] However, the use of high levels of SCM, such as 30 w%, 50 w%, 70 w%, 80 w%, 90 w% or even higher, based on the total hydraulic binder content in concrete, often leads to poor workability of the wet concrete mix. The use of superplasticizers is known to counter this effect, but known superplasticizers are not always very efficient, especially at maintaining concrete workability for a desired period, particularly with respect to slump retention. The use of known superplasticizers can also lead to a retarded development of mechanical strength.

[0008] It is therefore desirable to find novel admixtures that can improve the workability of cementitious compositions comprising SCM and in particular solve the problem of reduced workability of cementitious compositions having high levels of supplementary cementitious materials. At the same time, the novel admixtures should not retard the development of mechanical strength too much.Summary of the invention

[0009] It is an object of the present invention to provide novel admixtures that can improve the workability of cementitious compositions comprising supplementary cementitious materials.

[0010] It has now been found that an aqueous admixture comprising a mix of two chemically different polycarboxylate ether and at least one alkanolamine is suitable to improve the workability of cementitious compositions comprising supplementary cementitious materials.

[0011] The admixture of the present invention can in particular be used to improve the workability of reduced carbon footprint concrete, post-tensioned concrete with significant cement replacement, suspended slab concrete, super workable and selfcompacting concrete, long haul sites, and concrete with manufactured sands.

[0012] The admixture of the present invention delivers soft, workable and pumpable cementitious compositions at low water / binder ratios. The admixture of the present invention delivers enhanced slump retention of cementitious compositions which, for example, protects the concrete quality in case of long transport time. The admixture of the present invention may additionally deliver cementitious compositions having early strength without activators, improved finish, and / or fast wetting time. The admixture of the present invention meets the requirements of standard AS 1478.1-2000, type MWR. The objective of the present invention is therefore solved by an admixture as claimed in claim 1. Further aspects of the present invention are the subject matter of independent claims. Preferred embodiments are the subject matter of dependent claims.

[0013] Detailed Ways

[0014] Features and embodiments described for one aspect of the present invention shall also apply to other aspects.

[0015] In a first aspect the present invention relates to an admixture comprising

[0016] (i) a first polycarboxylate ether,

[0017] (ii) a second polycarboxylate ether which is chemically different from said firstpolycarboxylate ether, and

[0018] (iii) at least one alkanolamine.

[0019] A polycarboxylate ether is a polymer comprising or consisting of the following partial structural units:

[0020] a) a mole fractions of a partial structural unit S1 of formula (I)

[0021]

[0022] (I),

[0023] b) b mole fractions of a partial structural unit S2 of formula (II)

[0024]

[0025] (II),

[0026] optionally

[0027] c) c mole fractions of a partial structural unit S3 of formula (III)

[0028]

[0029] optionallyd) d mole fractions of a partial structural unit S4 of formula (IV)

[0030]

[0031] where in formulae (I) - (IV)

[0032] M independently of one another represents H+, an alkali metal ion, an alkaline earth metal ion, a bivalent or trivalent metal ion, an ammonium ion or an organic ammonium group,

[0033] each Ruindependently of the others stands for hydrogen or a methyl group, each Rvindependently one another stands for hydrogen or COOM,

[0034] m = 0, 1 or 2,

[0035] p = 0 or 1,

[0036] each A independently of one another is an alkylene group with 1 - 4 C atoms, preferably A are ethylene groups, and n = 2 - 250,

[0037] R1and R2independently of one another stand for a Ci to C20 alkyl group, cycloalkyl group, alkylaryl group, aryl group, hydroxyalkyl group, acetoxyethyl (CH3-CO-O-CH2-CH2-), hydroxy-isopropyl (HO-CH(CH3)-CH2-), or acetoxyisopropyl group (CH3-CO-O-CH(CH3)-CH2-),

[0038] and where a, b, c and d represent mole fractions of the respective partial structural units S1, S2, S3 and S4, with a / b / c / d = (0.1 - 0.9) / (0.1 - 0.9) / (0 - 0.8) / (0 - 0.8), preferably a / b / c / d = (0.3 - 0.9) / (0.1 - 0.7) / (0 - 0.6) / (0 - 0.4), more preferably a / b / c / d = (0.4 - 0.8) / (0.15 - 0.4) / 0 / (0 - 0.4), in particular a / b / c / d = (0.5 - 0.8) / (0.2 - 0.4) / 0 / 0. Preferably under the condition that a + b + c + d = 1.

[0039] According to embodiments, the first polycarboxylate ether is a polymer comprising or consisting of the following partial structural units:

[0040] a) a mole fractions of a partial structural unit S1 of formula (la)

[0041]

[0042] b) b mole fractions of a partial structural unit S2 of formula (Ila)

[0043]

[0044] where in formulae (la) and (Ila)

[0045] M independently of one another represents H+, an alkali metal ion, an alkaline earth metal ion, a bivalent or trivalent metal ion, an ammonium ion or an organic ammonium group,

[0046] each Ruindependently of the others stands for hydrogen or a methyl group, each Rvindependently one another stands for hydrogen or COOM, preferably hydrogen,

[0047] m = 0, p = 1,

[0048] each A independently of one another is an alkylene group with 1 - 4 C atoms, preferably A are ethylene groups, and n = 2 - 250, preferably 8 - 15,

[0049] and where a and b represent mole fractions of the respective partial structural units S1 and S2 with a / b = (0.1 - 0.9) / (0.1 - 0.9), preferably a / b = (0.3 - 0.9) / (0.1 - 0.7), more preferably a / b = (0.5 - 0.8) I (0.2 - 0.4), especially a / b = 0.510.5.

[0050] According to embodiments, the second polycarboxylate ether is a polymer comprising or consisting of the following partial structural units:

[0051] a) a mole fractions of a partial structural unit S1 of formula (lb)

[0052]

[0053] b) b mole fractions of a partial structural unit S2 of formula (lib)

[0054]

[0055] where in formulae (lb) and (lib)

[0056] M independently of one another represents H+, an alkali metal ion, an alkaline earth metal ion, a bivalent or trivalent metal ion, an ammonium ion or an organic ammonium group,

[0057] each Ruindependently of the others stands for hydrogen or a methyl group, preferably a methyl group,

[0058] each Rvindependently one another stands for hydrogen, COOM, or a methyl group, preferably hydrogen,

[0059] m = 1, p = 0,

[0060] each A independently of one another is an alkylene group with 1 - 4 C atoms, preferably A are ethylene groups, and n = 2 - 250, preferably 50 - 60,

[0061] and where a and b represent mole fractions of the respective partial structural units S1 and S2 with a / b = (0.1 - 0.9) / (0.1 - 0.9), preferably a / b = (0.3 - 0.9) / (0.1 - 0.7), more preferably a / b = (0.5 - 0.8) / (0.2 - 0.4), especially a / b = 0.75 / 0.25.The sequence of the partial structural units S1 , S2, S3 and S4 can be alternatingly, block-like or random. In principle, it is also possible for additional structural units to be present in addition to the partial structural units S1, S2, S3 and S4.

[0062] It is preferable for the partial structural units S1 , S2, S3 and S4 together to constitute a content by weight of at least 50 wt.%, more preferably at least 90 wt.%, and most preferred at least 99 wt.%, with respect to the total weight of the polycarboxylate ether.

[0063] The manufacture of polycarboxylate ether itself is known to the person skilled in the art and it can be carried out, for example, by radical polymerization of the corresponding monomers. Such radical polymerisation as well as resulting polycarboxylate ethers are described, for example, in WO2012 / 084954. It is preferred that the second polycarboxylate ether of the present invention is prepared by free radical polymerization.

[0064] It is also possible to prepare polycarboxylate ether by polymer-analogue esterification of a polycarboxylic acid. In the polymer-analogue reaction, the polycarboxylic acid is esterified and / or amidated with the corresponding alcohols or amines and then, if necessary, neutralized or partially neutralized (depending on the type of the residue M, for example, with metal hydroxides or ammonia). Details regarding the polymer-analogue reaction are disclosed, for example, in EP 1 138697 B1 on page 7, line 20 to page 8, line 50, as well as in its examples, or in EP 1 061 089 B1 on page 4, line 54 to page 5, line 38 as well as in its examples. The first polycarboxylate ether of the present invention can be prepared by free radical polymerization or by polymer-analogue esterification.

[0065] According to embodiments, the at least one alkanolamine is selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, diethanolisopropanolamine, ethanoldiisopropanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methyldiisopropanolamine, N-methyldiethanolamine, tetrahydroxyethylethylenediamine, and tetrahydroxyisopropylethylenediamine, and mixtures thereof, preferably the alkanolamine is selected from triisopropanolamine.

[0066] Preferably, the admixture of the present invention additionally comprises water.Preferably, the admixture of the present invention additionally comprises at least one of a defoamer, a biocide, a retarder, in particular sugar or sugar acid, and / or additional accelerators, in particular calcium nitrate and / or sodium thiocyanate. According to embodiments, an admixture of the present invention comprises or consists of, in each case relative to the total weight of the admixture,

[0067] a) 5 - 30 w%, preferably 15 -25 w%, of the first polycarboxylate ether polymer, b) 10 -40 w%, preferably 20 - 30 w%, of the second polycarboxylate ether polymer which is chemically different from said first polycarboxylate ether,

[0068] c) 0.1 - 1.0 w% of the at least one alkanolamine, preferably triisopropanolamine, d) optionally 0.1 - 1.0 w% of a defoamer,

[0069] e) optionally 0.1 - 0.5 w% of a biocide,

[0070] f) optionally 0.1 - 1.0 w% of a sugar or sugar acid,

[0071] and the rest to 100 w% of water.

[0072] An admixture of the present invention may be provided as a mono-component admixture or as a multi-component, especially a two-component admixture.

[0073] A mono-component admixture contains all constituents of the admixture in one container. This has the advantage that a lower number of containers has to be foreseen at the site of use and that no mistakes with relative dosages of constituents can occur.

[0074] A multi-component admixture contains the constituents of the admixture in multiple, preferably in two, spatially separated containers. A multi-component, especially two-component, admixture has the advantage that a ratio of individual components, and thereby constituents, may be easily adjusted according to specific requirements.

[0075] It has been found that an admixture of the present invention is particularly suited to improve the workability, in particular to increase the slump and / or the slump retention over time, of a cementitious composition comprising at least one supplementary cementitious material. Slump and slump retention overtime can be measured according to standard AS 1012.3.1 :2014. Within the present context an increase in workability, in particular an increase of slump and / or slump retention, always relates to a comparative cementitious composition not comprising an admixture of the present invention. Slump retention overtime is identical to slump life.It has been found that by the use of an admixture of the present invention it is possible to reduce the amount of water needed during mixing to achieve a desired workability. Thereby, it is possible to increase the early strength of a cementitious composition because a lower water / binder ratio is achieved. Strength can be measured as compressive strength according to standard AS 1012.9. Within the present context an increase of strength always relates to a comparative cementitious composition not comprising an admixture of the present invention.

[0076] In another aspect, the present invention therefore relates to the use of an admixture as described above to improve the workability and / or to increase the early strength of a cementitious composition comprising at least one supplementary cementitious material.

[0077] A cementitious composition within the present context is a composition comprising at least one cementitious binder, in particular Ordinary Portland cement, and additionally comprising at least one supplementary cementitious material. A cementitious composition may additionally comprise one or more of fillers, aggregates, water, and additives of admixtures different from the admixture of the present invention.

[0078] A supplementary cementitious material in particular is a pozzolan ora latent hydraulic material, especially ironmaking slag, steelmaking slag, fly ash, clays including calcined clays, and pozzolans of volcanic origin. According to embodiments, the at least one supplementary cementitious material is selected from the group consisting of ground granulated blast furnace slag, fly ash, calcined clay, and mixtures thereof.

[0079] The use of an admixture of the present invention has the advantage of high water reduction or increased slump at the same water to binder ratio, long slump life, and additionally enhanced concrete softness. At the same time, an admixture of the present invention does not lead to strong retardation of compressive strength development.

[0080] An admixture of the present invention can be used to cover a wide range of workability classes of cementitious compositions, from 120 mm slump to 700 mm spread. The ideal is 180-240 mm slump.

[0081] An admixture of the present invention can be used to achieve concrete strength classes from N25 to N80.In another aspect, the present invention relates to a cementitious composition comprising

[0082] (a) a cementitious binder, said cementitious binder comprising

[0083] (ai) Ordinary Portland cement, and

[0084] (aii) at least one supplementary cementitious material, and

[0085] (b) an admixture as described above.

[0086] Preferably, the cementitious composition is concrete.

[0087] Especially, an admixture of the present invention is suitable for cementitious binders comprising blends of Ordinary Portland cement with two or more supplementary cementitious material. According to embodiments, the at least one supplementary cementitious material in a cementitious composition of the present invention is selected from the group consisting of ground granulated blast furnace slag, fly ash, calcined clay, and mixtures thereof.

[0088] An admixture of the present invention can in particular be used in all concrete containing high volume of ground granulated blastfurnace slag, fly ash, and / or calcined clay. Ordinary Portland cement can be replaced therein to a large extent, for example a replacement level of 30 w%, 50 w%, 70 w%, 80 w%, 90 w% or higher can be achieved.

[0089] According to embodiments, a cementitious binder in a cementitious composition of the present invention comprises, in each case relative to the total dry weight of the cementitious binder,

[0090] (ai) not more than 70 w%, preferably not more than 50 w%, more preferably not more than 30 w%, in particular not more than 10 w%, of Ordinary Portland cement, and (aii) not less than 30 w%, preferably not less than 50 w%, more preferably not less than 70 w%, in particular not less than 90 w% of the at least one supplementary cementitious material.

[0091] In particular Ordinary Portland cement is contained in a cementitious binder of the present invention in 1 - 70 w%, preferably 2 - 50 w%, more preferably 3 - 30 w%, still more preferably 5 - 10 w%.

[0092] In particular the at least one supplementary cementitious material is contained in a cementitious binder of the present invention in 30 - 99 w%, preferably 50 - 98 w%, more preferably 70 - 97 w%, still more preferably 90 - 95 w%.According to embodiments, the admixture is present in a cementitious composition of the present invention at a ratio of between 400 ml to 1500 ml, preferably between 600 ml to 1200 ml, in each case relative to 100 kg of dry cementitious binder.

[0093] Dosage rates of an admixture of the present invention will vary according to materials used, ambient conditions and the requirements of a specific project. For general concrete, the admixture of the present invention preferably is dosed at a ratio of between 400 to 1500 ml, such as for example 600 ml, per 100 kg of total binder. Such dosage in particular allows the slump keeping components to efficiently hold the slump. For SCC concrete mixes the admixture of the present invention is preferably dosed at a ratio of 1200 ml / 100 kg of total binder. Dosage rates outside the recommended range may be used where specialized materials such as micro silica are specified, extreme ambient conditions are encountered, or unusual project conditions require special consideration.

[0094] Fresh concrete comprising an admixture of the present invention does not crawl, and it looks like a very ordinary concrete. Fresh concrete comprising an admixture of the present invention shows enhanced pumpability.

[0095] Examples

[0096] In a first set of experiments concrete compositions were prepared from shrinkage limited (SL) cement according to standard AS 3972 and ground granulated blast furnace slag (GGBFS) according to standard AS 3582.2. Thereby the cementitious binder consisted of 42 w% SL cement and 58 w% GGBFS. The mix design was 340 kg / m3total binder content, 580 kg / m320-mm nominal size aggregate, 370 kg / m310-mm nominal size aggregate, 520 kg / m3manufactured sand of 0.15-4.75 mm, 380 kg / m3natural sand of 0.15-4.75 mm. Batching water and admixtures S1 or S2 were added in the respective amounts indicated in below table 1.

[0097] Admixture S1 : 59 w% water, 39 w% polycarboxylate ether (obtained by free radical polymerization), 1 w% triisopropanolamine, 1 w% additive (mix of defoamer, sugar retarder, and biocide).

[0098] Admixture S2: 52 w% water, 20 w% first polycarboxylate ether (poly-co(methacrylic acid-acrylic acid) esterified with methanol-started polyethylene oxide of Mw = 500 g / mol), 26 w% second polycarboxylate ether (copolymer of acrylic acid and methallylalcohol-started polyethylene oxide of Mw = 2400 g / mol in a molar ratio of 0.75 : 0.25), 1 w% triisopropanolamine, 1 w% additive (mix of defoamer, sugar retarder, and biocide).

[0099] Slump was measured according to standard AS 1012.3.1:2014 after the time indicated in table 1 below, wherein initial is a measurement directly after mixing with batch water.

[0100] Compressive strength (C.S.) was measured according to standard AS 1012.9 after the time indicated in below table 1.

[0101] Table 1: Examples C-1 (comparative) and 1-1, 1-2 (inventive)

[0102]

[0103] It can be seen from the results in Table 1 that the use of the inventive admixture in examples 1-1 and 1-2 leads to significantly improved slump retention where the slumps at 30 and 60 minutes are significantly higher than those of the reference in example C-1. The early strength at 1-day is improved in inventive examples compared to the reference while the ultimate strength after 28 days is either comparable (in example 1-1) or slightly higher with high dosage (in example 1-2).In a second set of experiments, a concrete composition was prepared from a cementitious binder consisting of 30 w% Portland cement and 70 w% ground granulated blastfurnace slag. The concrete mix was designed fora targeted 28-day compressive strength of 40 MPa. Admixture S2 as described in the first set of experiments above was added together with the mixing water at a dosage of 1000 ml per 100 kg of total dry binder. The resulting concrete mixture was workable with reasonable softness. The compressive strength development is presented in Table 2, demonstrating compliance with the requirements.

[0104] Table 2: Example 2-1 (inventive)

[0105]

Claims

1. Claims1. An admixture comprising(i) a first polycarboxylate ether,(ii) a second polycarboxylate ether which is chemically different from said first polycarboxylate ether, and(iii) at least one alkanolamine.

2. The admixture as claimed in claim 1 , characterized in that the first polycarboxylate ether is a polymer comprising or consisting of the following partial structural units:a) a mole fractions of a partial structural unit S1 of formula (la)b) b mole fractions of a partial structural unit S2 of formula (Ila)where in formulae (la) and (Ila)M independently of one another represents H+, an alkali metal ion, an alkaline earth metal ion, a bivalent ortrivalent metal ion, an ammonium ion or an organic ammonium group,each Ruindependently of the others stands for hydrogen or a methyl group,each Rvindependently one another stands for hydrogen or COOM, preferably hydrogen,m = 0, p = 1,each A independently of one another is an alkylene group with 1 - 4 C atoms, preferably A are ethylene groups, and n = 2 - 250, preferably 8 - 15, and where a and b represent mole fractions of the respective partial structural units S1 and S2 with a / b = (0.1 - 0.9) / (0.1 - 0.9), preferably a / b = (0.3 - 0.9) I (0.1 - 0.7), more preferably a / b = (0.5 - 0.8) I (0.2 - 0.4), especially a / b = 0.51 0.5.

3. The admixture as claimed in at least one of the previous claims, characterized in that the second polycarboxylate ether is a polymer comprising or consisting of the following partial structural units:a) a mole fractions of a partial structural unit S1 of formula (lb)b) b mole fractions of a partial structural unit S2 of formula (lib)where in formulae (lb) and (lib)M independently of one another represents H+, an alkali metal ion, an alkaline earth metal ion, a bivalent ortrivalent metal ion, an ammonium ion or an organic ammonium group,each Ruindependently of the others stands for hydrogen or a methyl group, preferably a methyl group,each Rvindependently one another stands for hydrogen, COOM, or a methyl group, preferably hydrogen,m = 1, p = 0,each A independently of one another is an alkylene group with 1 - 4 C atoms, preferably A are ethylene groups, and n = 2 - 250, preferably 50 - 60, and where a and b represent mole fractions of the respective partial structural units S1 and S2 with a / b = (0.1 - 0.9) / (0.1 - 0.9), preferably a / b = (0.3 - 0.9) I (0.1 - 0.7), more preferably a / b = (0.5 - 0.8) I (0.2 - 0.4), especially a / b = 0.75 / 0.25.

4. The admixture as claimed in at least one of the previous claims, characterized in that the at least one alkanolamine is selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, diethanolisopropanolamine, ethanoldiisopropanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methyldiisopropanolamine, N- methyldiethanolamine, tetrahydroxyethylethylenediamine, and tetrahydroxyisopropylethylenediamine, and mixtures thereof, preferably the alkanolamine is selected from triisopropanolamine.

5. The admixture as claimed in at least one of the previous claims, characterized in that it comprises or consists of, in each case relative to the total weight of the admixture,a) 5 - 30 w%, preferably 15 -25 w%, of the first polycarboxylate ether polymer,b) 10 -40 w%, preferably 20 - 30 w%, of the second polycarboxylate ether polymer which is chemically different from said first polycarboxylate ether, c) 0.1 - 1.0 w% of the at least one alkanolamine, preferablytriisopropanolamine,d) optionally 0.1 - 1.0 w% of a defoamer,e) optionally 0.1 - 0.5 w% of a biocide,f) optionally 0.1 - 1.0 w% of a sugar or sugar acid,and the rest to 100 w% of water.

6. The use of an admixture as claimed in at least one of the claims 1 - 5 to improve the workability and / or to increase the early strength of a cementitious composition comprising at least one supplementary cementitious material.

7. The use as claimed in claim 6, characterized in that the at least one supplementary cementitious material is selected from the group consisting of ground granulated blastfurnace slag, fly ash, calcined clay, and mixtures thereof.

8. A cementitious composition comprising(a) a cementitious binder, said cementitious binder comprising(ai) Ordinary Portland cement, and(aii) at least one supplementary cementitious material, and(b) an admixture as claimed in at least one of claims 1 - 5.

9. The cementitious composition as claimed in claim 8, characterized in that the at least one supplementary cementitious material is selected from the group consisting of ground granulated blastfurnace slag, fly ash, calcined clay, and mixtures thereof.

10. The cementitious composition as claimed in at least one of claims 8 - 9, characterized in that the cementitious binder comprises, in each case relative to the total dry weight of the cementitious binder,(ai) not more than 70 w%, preferably not more than 50 w%, more preferably not more than 30 w%, in particular not more than 10 w%, of Ordinary Portland cement, and(aii) not less than 30 w%, preferably not less than 50 w%, more preferably not less than 70 w%, in particular not less than 90 w% of the at least one supplementary cementitious material.

11. The cementitious composition as claimed in at least one of claims 8 - 10, characterized in that the admixture is present at a ratio of between 400 ml to 1500 ml, preferably between 600 ml to 1200 ml, in each case relative to 100 kg of dry cementitious binder.

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