Aqueous admixture for cementitious construction compositions

Abstract

An aqueous admixture for cementitious construction compositions comprises i) a dissolved inorganic sulfate source providing a sulfate ion concentration of 0.3 to 1.0 mol / L, and ii) at least one superplasticizer in an amount in the range of 0.1 to 34 g / L. 5 The aqueous admixture has a solids content of less than 20 wt.-%. The aqueous admixture allows for modifying a property of a cementitious construction composition, the property being at least one of accelerating set and / or hardening after 8 to 24 h, retaining slump flow and reducing water demand.

Description

[0001] Construction Research & Technology GmbH

[0002] 1

[0003] Aqueous Admixture for Cementitious Construction Compositions

[0004] The present invention relates to an aqueous admixture for cementitious construction compositions, a kit of at least two parts comprising a first part comprising the admixture and a second part comprising a seed component, and a process comprising adding the admixture to a cementitious construction composition.

[0005] Concrete is the most widely used engineering material in the world. Concrete is a term that refers to a composite material of a binding medium having particles or fragments of aggregate embedded therein. In most construction concretes currently employed, the binding medium is formed from a mixture of a hydraulic cement and water.

[0006] Most hydraulic cements employed today are based upon Portland cement. Portland cement is made primarily from certain clay minerals, limestone and gypsum, in a high temperature process that drives off carbon dioxide and chemically combines the primary ingredients into new compounds. Because carbon dioxide is generated by both the cement production process itself, as well as by energy plants that generate power to run the production process, cement production is currently a leading source of current carbon dioxide atmospheric emissions.

[0007] As global warming and ocean acidification become an increasing problem and the desire to reduce carbon dioxide gas emissions (a principal cause of global warming) continues, the cement production industry will fall under increased scrutiny. Moreover, cement plants produce other pollutants like NOX, SOX, VOCs, particulates and mercury. Cement plants also produce cement kiln dust, which must sometimes be land filled, often in hazardous materials landfill sites.

[0008] It is known that dispersants are added to aqueous slurries of hydraulic binders for improving their workability, i.e. kneadability, spreadability, sprayability, pumpability or flowability. Such admixtures are capable of preventing the formation of solid agglomerates, and of dispersing the particles already present as well as those newly formed by hydration, and in this way improving the workability. In order to convert the pulverulent binders into a freshly mixed processible form, substantially more mixing water is required than would be necessary for the subsequent hydration and hardening process. The voids formed in the concrete body by the excess of water, which subsequently evaporates, lead to poor mechanical strength and resistance.Construction Research & Technology GmbH

[0009] 2

[0010] It is generally desirable to provide construction compositions with as low an amount of water as possible without compromising critical properties such as open time, high early strength and high final strength.

[0011] For the above-mentioned reasons, the market is changing towards clinker-reduced construction compositions. Generally, this can be achieved by reducing the amount of cement in the construction composition or using clinker-reduced cements. By reducing the amount of cement and / or using clinker-reduced cements, typically, supplementary cementitious materials (SCMs) are implemented in the cements and in the construction composition. This often causes a higher superplasticizer demand and a loss of workability retention as SCMs often exhibit a high surface area onto which superplasticizers can adsorb. Furthermore, such clinker-reduced construction compositions often have the drawback of reduced early strength which disadvantageously results in delayed demolding or processing of the construction composition. As a result, such climate friendly clinker-reduced construction compositions are limited for certain applications.

[0012] It is therefore furthermore desirable to provide construction compositions with reduced carbon footprint without compromising critical properties such as open time, high early strength and high final strength, compared to ordinary Portland cement based mixes.

[0013] B. Ding et al., Construction and Building Materials 2023, 405, 133256 investigate the change of the ion concentration of sulfate on the aggregation form of PCE. To a mixture of water and PCE were added Na2SO4crystals. The solution was stirred until Na2SO4crystals were completely dissolved, and then stood still to observe whether salt precipitation of PCE occurs.

[0014] WO 2024 / 036369 A1 describes a composition comprising an activator comprising anhydrous sodium sulfate and / or an alkali biopolymer; a dispersant; a humectant; at least one additive chosen from a rheology modifier, a de-foamer, a biocide agent, a surface tension agent, or a combination thereof; and water. The composition comprises about 20% by weight to about 80% by weight solids, based on the total weight of the composition.Construction Research & Technology GmbH

[0015] 3

[0016] WO 2023 / 025585 A1 describes a binder composition comprising A) a Portland cement clinker, B) calcium sulfatex H2O, C) an inorganic sulfate source having a solubility higher than 100 g / l at 20°C, D) a polyalcohol and / or metal salts thereof, E) a carbonate, F) a retarder component, and G) a dispersant having a charge density of more than 0.80 peq / g.

[0017] M. Zhang et al., Journal of Cleaner Production 2023, 408, 137022 describe the influence of C-S-H seed and sodium sulfate on the hydration and strength of limestone calcined clay cement. F. Zou et al., Journal of Cleaner Production 2020, 244, 118566 describe enhancement of early-age strength of the high content fly ash blended cement paste by sodium sulfate and C-S-H seeds towards a greener binder. The documents do not relate to superplasticizers.

[0018] It is known that flash setting of cement can occur if a cement system is not properly sulfated, i.e. does not or only in insufficient amounts comprise a retarder. Flash setting means very fast reaction of C3A to form ettringite phases, thereby spoiling workability and delaying the silicate reaction. Therefore, cement systems typically comprise a retarder. The retarders, however, suppress the silicate reaction which can therefore not contribute to early strength development.

[0019] It is an object of the invention to provide an aqueous admixture for cementitious construction composition which overcomes the above-mentioned drawbacks.

[0020] This object is solved by an aqueous admixture for cementitious construction compositions, comprising

[0021] i) a dissolved inorganic sulfate source providing a sulfate ion concentration of 0.3 to 1.0 mol / L, preferably 0.5 to 1.0 mol / L, more preferably 0.5 to 0.7 mol / L, and ii) at least one superplasticizer in an amount in the range of 0.1 to 34 g / L, preferably 0.5 to 30 g / L, more preferably 0.5 to 18 g / L,

[0022] the aqueous admixture having a solids content of less than 20 wt.-%, preferably less than 16 wt.-%.

[0023] The invention further relates to a kit of at least two parts comprising

[0024] 1. a first part comprising the admixture as described above, and

[0025] 2. a second part comprising a seed component selected from a C-S-H seed component, a C-A-S-H seed component and a Ca(OH)2seed component.Construction Research & Technology GmbH

[0026] 4

[0027] The invention further relates to a process comprising adding the admixture as described above to a cementitious construction composition.

[0028] It has surprisingly been found that the inventive aqueous admixture for cementitious construction compositions allows for modifying a property of a cementitious construction composition. The property modification may be at least one of accelerating set and / or hardening after 8 to 24 h, retaining slump flow and reducing water demand.

[0029] The hydration of Portland cements basically consists of two different reaction regimes that interact with each other, namely (1) the silicate reaction and (2) the aluminate reaction.

[0030] The silicate reaction involves dissolution of C3S, and precipitation of C-S-H phases and portlandite. The nano-sized, colloidal C-S-H phases are mainly responsible for developing the strength of the cement paste.

[0031] The aluminate reaction is responsible for the setting of the cement, thereby regulating the workability and the rheological properties of the cement. The dissolution of the clinker phase C3A is controlled by sulfate present in the cement.

[0032] It has been suggested that the delayed and less steep acceleration of the silicate reaction is caused by Al ions left from the early aluminate reaction. It is known that Al in solution leads to the precipitation of C-A-S-H phases instead of C-S-H. C-A-S-H is supposed not to be able to act as a substrate for C-S-H. This would therefore slow down the silicate reaction. Also, the alite hydration itself can be slowed down by Al inhibition.

[0033] Once aluminate is dissolved from C3A and C4AF, the presence of a sufficient amount of soluble sulfate is believed crucial in order to bind aluminate via the formation of ettringite. Thereby it is possible to push the aluminate reaction ahead of the silicate reaction, thereby enhancing the degree of hydration of C3A.

[0034] The improved slump flow retention that is observed by the present invention may be explained by competitive adsorption of the sulfate with the superplasticizer on the cement and SCM particles. Conventional retarders, such as hydroxycarboxylic acids, a-carbonyl-carboxylic acids, di- or tri-carboxyl ic acids, glyoxylic acid polycondensates and glyoxylicConstruction Research & Technology GmbH

[0035] 5

[0036] acid sulfite addition products, phosphonate retarders and phosphate retarders, and salts thereof, can be dispended without compromising workability.

[0037] Aqueous admixture

[0038] According to the invention, the aqueous admixture for cementitious construction compositions comprises

[0039] i) a dissolved inorganic sulfate source providing a sulfate ion concentration of 0.3 to 1.0 mol / L, preferably 0.5 to 1.0 mol / L, more preferably 0.5 to 0.7 mol / L, and ii) at least one superplasticizer in an amount in the range of 0.1 to 34 g / L, preferably 0.5 to 30 g / L, more preferably 0.5 to 18 g / L.

[0040] The aqueous admixture has a solids content of less than 20 wt.-%, preferably less than 16 wt.-%.

[0041] Dissolved inorganic sulfate source i)

[0042] The inventive admixture comprises a dissolved inorganic sulfate source providing a sulfate ion concentration as described above. Suitably, the inorganic sulfate source has an aqueous solubility at 20 °C of 100 g / L or more. An inorganic sulfate source which suffices said solubility requirement may be referred to as “readily soluble” sulfate source herein. The nature of the inorganic sulfate source i) is not particularly limited as long as it can be dissolved with providing a sulfate ion concentration as described above.

[0043] Depending on the pH value, there may be an equilibrium between sulfate and hydrogen sulfate in the aqueous admixture. The pH value of the admixture can be in the range of 0.5 to 7, preferably 1 to 6. In case focus is on slump retention, the pH value of the admixture is preferably in the range of 0.5 to 3. Therefore, hydrogen sulfate or a mixture of hydrogen sulfate and sulfate can also be used for preparing the aqueous admixture according to the invention.

[0044] Herein, pH values are determined at a temperature of 21 °C with an Ahlborn Almemo 2890-9 device, using an Ag / AgCI reference electrode, with KCI as electrolyte (model Almemo FY96PH-Ex). Calibration was carried out using a 2-point calibration with pH buffer solutions of 1.679 and 4.01. The measurement was carried out as follows: the solution was placed in a beaker with a magnetic stirrer, the pH electrode immersed and the value taken once the pH meter showed a value stable for more than 5 s. Two valuesConstruction Research & Technology GmbH

[0045] 6

[0046] were taken for each measurement, and the average value of both measurements was taken as the pH value.

[0047] In an embodiment, the inorganic sulfate source i) is selected from lithium sulfate, lithium hydrogensulfate, sodium sulfate, sodium hydrogensulfate, potassium sulfate, potassium hydrogensulfate, aphthitalite (K3Na(SO4)2), iron (II) sulfate, copper sulfate, zinc sulfate, and mixtures thereof. Preferably, the inorganic sulfate source i) is selected from sodium sulfate, sodium hydrogensulfate, potassium sulfate, potassium hydrogensulfate, and mixtures thereof. In particular, the inorganic sulfate source i) is sodium sulfate.

[0048] Superplasticizer(s) ii)

[0049] The inventive admixture comprises at least one superplasticizer ii). The nature of the superplasticizer ii) is not particularly limited as long as it fulfils its purpose which is adjusting or increasing the fluidity of a construction composition without adding substantially more water to the mix.

[0050] In an embodiment, the at least one superplasticizer (also referred to as “dispersant” herein) is selected from

[0051] c-1) polycarboxylate ethers (PCEs),

[0052] c-2) phosphorylated polycondensates obtainable by condensation reaction of

[0053] c-2-1) an aromatic compound having a phosphate moiety,

[0054] c-2-2) an alkoxylated hydroxyaryl compound, and

[0055] c-2-3) formaldehyde,

[0056] and

[0057] c-3) mixtures thereof.

[0058] The polycarboxylate ether c-1) having a carbon-containing backbone to which are attached pendant cement-anchoring groups and polyether side chains are particularly preferred. The cement-anchoring groups are anionic and / or anionogenic groups such as carboxylic groups, phosphonic or phosphoric acid groups or their anions. Anionogenic groups are the acid groups present in a polymeric dispersant, which can be transformed to the respective anionic group under alkaline conditions.

[0059] Preferably, the structural unit comprising anionic and / or anionogenic groups is one of the general formulae (la), (lb), (Ic) and / or (Id):Construction Research & Technology GmbH

[0060] 7

[0061] H R1

[0062] / I I \

[0063] -4— c-c4- ' i i '

[0064] H C=O

[0065] I

[0066] X

[0067] l2

[0068] rx

[0069]

[0070] (la)

[0071] wherein

[0072] R1is H, C1-C4 alkyl, CH2COOH or CH2CO-X-R3A, preferably H or methyl;

[0073] X is NH-(CniH2ni) or O-(CniH2ni) with n1 = 1, 2, 3 or 4, or a chemical bond, the nitrogen atom or the oxygen atom being bonded to the CO group;

[0074] R2is OM, PO3M2, or O-PO3M2; with the proviso that X is a chemical bond if R2is OM; R3Ais PO3M2, or O-PO3M2;

[0075] H R3

[0076] / I I V

[0077] — (-0-0 —

[0078] H (CnH2n)-R4

[0079]

[0080] (lb)

[0081] wherein

[0082] R3is H or C1-C4 alkyl, preferably H or methyl;

[0083] n is 0, 1, 2, 3 or 4;

[0084] R4is PO3M2, or O-PO3M2;

[0085] H R5

[0086] — (-c-c-)—

[0087] z

[0088] (lc)

[0089] wherein

[0090] R5is H or C1-C4 alkyl, preferably H;

[0091] Z is O or NR7;

[0092] R7is H, (Cn1H2n1)-OH, (Cn1H2n1)-PO3M2, (Cn1H2n1)-OPO3M2, (C6H4)-PO3M2, or (C6H4)-OPO3M2, and

[0093] n1 is 1, 2, 3 or 4;Construction Research & Technology GmbH

[0094] 8

[0095]

[0096] (Id)

[0097] wherein

[0098] R6is H or C1-C4 alkyl, preferably H;

[0099] Q is NR7or O;

[0100] R7is H, (Cn1H2ni)-OH, (Cn1H2ni)-PO3M2, (Cn1H2n1)-OPO3M2, (C6H4)-PO3M2, or (C6H4)-OPO3M2,

[0101] n1 is 1, 2, 3 or 4; and

[0102] where each M independently is H or a cation equivalent.

[0103] Preferably, the structural unit comprising a polyether side chain is one of the general formulae (Ila), (lib), (lie) and / or (lid):

[0104] j-^101p11

[0105] R12Cn2H2n2-Z2-E-G-(AO^-R13

[0106]

[0107] wherein

[0108] R10, R11and R12independently of one another are H or Ci-C4alkyl, preferably H or methyl;

[0109] Z2is O or S;

[0110] E is C2-C6alkylene, cyclohexylene, CH2-C6H10, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene;

[0111] G is O, NH or CO-NH; or

[0112] E and G together are a chemical bond;

[0113] A is C2-Cs alkylene or CH2CH(C6H5), preferably C2-C3alkylene;

[0114] n2 is 0, 1, 2, 3, 4 or 5;Construction Research & Technology GmbH

[0115] a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100;

[0116] R13is H, an unbranched or branched C1-C4 alkyl group, CO-NH2or COCH3;

[0117]

[0118] (Hb)

[0119] wherein

[0120] R16, R17and R18independently of one another are H or C1-C4 alkyl, preferably H;

[0121] E2is C2-C6 alkylene, cyclohexylene, CH2-C6H10, 1,2-phenylene, 1,3-phenylene, or 1,4-phenylene, or is a chemical bond;

[0122] A is C2-C5 alkylene or CH2CH(C6H5), preferably C2-C3alkylene;

[0123] n2 is 0, 1, 2, 3, 4 or 5;

[0124] L is C2-C5 alkylene or CH2CH(C6H5), preferably C2-C3alkylene;

[0125] a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; d is an integer from 1 to 350, preferably 10 to 150, more preferably 20 to 100;

[0126] R19is H or C1-C4 alkyl; and

[0127] R20is H or C1-C4 alkyl;

[0128] c — c

[0129] R23r* _ (AO)a

[0130]

[0131] wherein

[0132] R21, R22and R23independently are H or C1-C4 alkyl, preferably H;

[0133] W is O, NR25, or is N;

[0134] V is 1 if W= O or NR25, and is 2 if W= N;

[0135] A is C2-C5 alkylene or CH2CH(C6H5), preferably C2-C3 alkylene;

[0136] a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100;

[0137] R24is H or CrC4alkyl;

[0138] R25is H or C1-C4 alkyl;Construction Research & Technology GmbH

[0139] 10

[0140] ” R6H "

[0141] - Q - c - IVIO - c c - Q - (AO)a- R

[0142] I l l i L -I v

[0143] o o

[0144]

[0145] (lid)

[0146] wherein

[0147] R6is H or C1-C4 alkyl, preferably H;

[0148] Q is NR10, N or O;

[0149] V is 1 if Q = O or NR10and is 2 if Q = N;

[0150] R10is H or C1-C4 alkyl;

[0151] A is C2-C5 alkylene or CH2CH(C6H5), preferably C2-C3 alkylene; and

[0152] a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100;

[0153] where each M independently is H or a cation equivalent.

[0154] The molar ratio of structural units (I) to structural units (II) varies from 1:3 to about 10:1, preferably 1:1 to 10:1, more preferably 3:1 to 6:1. The polymeric dispersants comprising structural units (I) and (II) can be prepared by conventional methods, for example by free radical polymerization or controlled radical polymerization. The preparation of the dispersants is, for example, described in EP 0894811, EP 1 851 256, EP 2463314, and EP 0753488.

[0155] A number of useful dispersants contain carboxyl groups, salts thereof or hydrolysable groups releasing carboxyl groups upon hydrolysis. Preferably, the milliequivalent number of carboxyl groups contained in these dispersants (or of carboxyl groups releasable upon hydrolysis of hydrolysable groups contained in the dispersant) is in the range of 0.5 to 5.0 meq / g, preferably 0.5 to 4.0 meq / g, more preferably 0.5 to 3.0 meq / g, assuming all the carboxyl groups to be in unneutralized form.

[0156] In an embodiment, the PCE is a non-ionic comb polymer having a carbon-containing backbone to which are attached pendant hydrolysable groups and polyether side chains, the hydrolysable groups upon hydrolysis releasing cement-anchoring groups. Conveniently, the structural unit comprising a polyether side chain is one of the generalConstruction Research & Technology GmbH

[0157] 11

[0158] formulae (Ila), (lib), (lie) and / or (lid) discussed above. The structural unit having pendant hydrolysable groups is preferably derived from acrylic acid ester monomers, more preferably hydroxyalkyl acrylic monoesters and / or hydroxyalkyl diesters, most preferably hydroxypropyl acrylate and / or hydroxyethyl acrylate. The ester functionality will hydrolyze to (deprotonated) acid groups upon exposure to water at preferably alkaline pH, which is provided by mixing the cementitious binder with water, and the resulting acid functional groups will then form complexes with the cement component.

[0159] In one embodiment, the dispersant is selected from colloidally disperse preparations of polyvalent metal cations, such as Al3+, Fe3+or Fe2+, and a polymeric dispersant which comprises anionic and / or anionogenic groups and polyether side chains. The polyvalent metal cation is present in a superstoichiometric quantity, calculated as cation equivalents, based on the sum of the anionic and anionogenic groups of the polymeric dispersant. Such dispersants are described in further detail in WO 2014 / 013077 A1.

[0160] The phosphorylated polycondensate c-2) is obtainable by a condensation reaction of c-2-1) an aromatic compound having a phosphate moiety,

[0161] c-2-2) an alkoxylated hydroxyaryl compound, and

[0162] c-2-3) formaldehyde.

[0163] The phosphorylated polycondensate c-2) may comprise structural units (III) and (IV):

[0164]

[0165] (HI)

[0166] wherein

[0167] T is phenyl, naphthyl or heteroaryl having 5 to 10 ring atoms, of which 1 or 2 atoms are heteroatoms selected from N, O and S;

[0168] n3 is 1 or 2;

[0169] B is N, NH or O, with the proviso that n3 is 2 if B is N and n3 is 1 if B is NH orO; A is C2-C5alkylene or CH2CH(C6H5), preferably C2-C3alkylene;

[0170] a2 is an integer from 1 to 300;

[0171] R26is H, C1-C10 alkyl, Cs-Ca cycloalkyl, aryl, or heteroaryl having 5 to 10 ring atoms, of which 1 or 2 atoms are heteroatoms selected from N, O and S;Construction Research & Technology GmbH

[0172] 12

[0173] where the structural unit (IV) is selected from the structural units (IVa) and (IVb):

[0174]

[0175] (IVa)

[0176] wherein

[0177] D is phenyl, naphthyl or heteroaryl having 5 to 10 ring atoms, of which 1 or 2 atoms are heteroatoms selected from N, O and S;

[0178] E3is N, NH or O, with the proviso that m is 2 if E3is N and m is 1 if E3is NH or O; A is C2-C5 alkylene or CH2CH(C6H5), preferably C2-C3 alkylene;

[0179] b is an integer from 0 to 300;

[0180] M independently is H or a cation equivalent;

[0181] R7A

[0182]

[0183] (IVb)

[0184] wherein

[0185] V2is phenyl or naphthyl and is optionally substituted by 1 or two radicals selected from R8, OH, OR8, (CO)R8, COOM, COOR8, SO3R8and NO2;

[0186] R7Ais COOM, OCH2COOM, SO3M or OPO3M2;

[0187] M is H or a cation equivalent; and

[0188] R8is C1-C4 alkyl, phenyl, naphthyl, phenyl-Ci-C4 alkyl orCi-C4 alkylphenyl.

[0189] Polymers comprising structural units (III) and (IV) are obtainable by polycondensation of an aromatic or heteroaromatic compound having a polyoxyalkylene group attached to the aromatic or heteroaromatic core, an aromatic compound having a carboxylic, sulfonic or phosphate moiety, and an aldehyde compound such as formaldehyde.

[0190] The charge density can be determined analytically by charge titration with poly diallyl dimethylammonium chloride (Poly-DADMAC) as described in J. Plank, B. Sachsenhauser, “Experimental determination of the effective anionic charge density of polycarboxylate superplasticizers in cement pore solution”, Cement and Concrete Research 2009, 39, 1-5. In this process, a base (aqueous NaOH) is added to the sampleConstruction Research & Technology GmbH

[0191] 13

[0192] to ensure full deprotonation first. A cationic polyelectrolyte solution of poly-DADMAC is then added until full charge neutralization.

[0193] Solids content

[0194] According to the invention, the aqueous admixture has a solids content of less than 20 wt.-%, preferably less than 16 wt.-%. Generally, the solids content is 5 wt.-% or more, preferably 10 wt.-% or more. Solids contents of less than 20 wt.-% result in the admixtures being in liquid form which is favorable for handling, especially at low temperatures.

[0195] The solids content may be determined by drying 3 g + / - 0.1 g of the aqueous admixture in a crucible in porcelain in an oven at a temperature of 60 °C for 24 h.

[0196] In an embodiment, the admixture additionally comprises at least one of an alkanolamine, and a polyol, such as alkanediols, alkanetriols, sugar polyols, and mixtures thereof.

[0197] “Polyol” is intended to denote a compound having at least two alcoholic hydroxyl groups in its molecule, for example 3, 4, 5 or 6 alcoholic hydroxyl groups. Polyols having vicinal hydroxyl groups are preferred. Polyols having at least three hydroxyl groups bound to three carbon atoms in sequence are most preferred.

[0198] The ability of the polyol to chelate calcium ions and thereby stabilize calcium in solution can be assessed by a calcium aluminate precipitation test. In an embodiment, the polyol, in a calcium aluminate precipitation test in which a test solution, obtained by supplementing 400 mL of a 1 wt.-% aqueous solution of the polyol with 20 mL of a 1 mol / L NaOH aqueous solution and 50 mL of a 25 mmol / L NaAIO2 aqueous solution, is titrated with a 0.5 mol / L CaCI2aqueous solution at 20 °C, inhibits precipitation of calcium aluminate up to a calcium concentration of 75 ppm, preferably 90 ppm.

[0199] The test detects the precipitation of calcium aluminate by turbidity. Initially, the test solution is a clear solution. The clear test solution is titrated with a CaCI2aqueous solution at a constant dosage rate of, e.g., 2 mL / min, as described above. With ongoing addition of CaCI2, precipitation of calcium aluminate results in a change of the optical properties of the test solution by turbidity. The titration endpoint, expressed as theConstruction Research & Technology GmbH

[0200] 14

[0201] maximum calcium concentration (as Ca2+), before the onset of turbidity can be calculated from the elapsed time to the onset point.

[0202] In a preferred embodiment, the polyol is selected from compounds consisting of carbon, hydrogen, and oxygen only and which do not contain a carbonyl group (C=O) in its molecule. It is understood that the term “carbonyl group” encompasses the tautomeric form of the C=O group, i.e. a pair of doubly bonded carbon atoms adjacent to a hydroxyl group (-C=C(OH)-).

[0203] In an embodiment, the polyol is selected from monosaccharides, oligosaccharides, water-soluble polysaccharides, compounds of general formula (P-l) or dimers or trimers of compounds of general formula (P-l):

[0204]

[0205] wherein

[0206] X is

[0207]

[0208] (P-la) (P-lc) wherein

[0209] R is -CH2OH, -NH2,

[0210] n is an integer from 1 to 4,

[0211] m is an integer from 1 to 8.

[0212] In one embodiment, the polyol is selected from saccharides. Useful saccharides include monosaccharides, such as glucose and fructose; disaccharides, such as lactose and sucrose; trisaccharides, such as raffinose; and water-soluble polysaccharides, such as amylose and maltodextrins.Construction Research & Technology GmbH

[0213] 15

[0214] Compounds of formula (P-l) wherein X is (P-la) are generally referred to as sugar alcohols. Sugar alcohols are organic compounds, typically derived from sugars, containing one hydroxyl group (-OH) attached to each carbon atom. Useful sugar alcohols are mannitol, sorbitol, xylitol, arabitol, erythritol and glycerol. Among these, glycerol is particularly preferred. It is envisaged that carbonates of polyhydric alcohols such as glycerol carbonate can act as a polyol source.

[0215] Compounds of formula (P-l) wherein X is (P-lb) include pentaerythritol, and tris(hydroxymethyl)aminomethane.

[0216] Compounds of formula (P-l) wherein X is (P-lc) include triethanolamine.

[0217] Dimers or trimers denote compounds wherein two or three molecules of general formula (P-l) are linked via an ether bridge and which are formally derived from a condensation reaction with elimination of one or two molecules of water. Examples of dimers and trimers of compounds of formula (P-l) include dipentaerythritol and tripentaerythritol.

[0218] The amount of the polyol, preferably glycerol, may be in the range of 0.1 to 5 wt.-%, based on the total amount of the aqueous admixture.

[0219] In an embodiment, the alkanolamine is selected from diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (THEED), methyl diethanolamine (MDEA), and mixtures thereof.

[0220] Preferably, the alkanolamine is selected from triisopropanolamine (TIPA), diethanolamine (DEA) N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (THEED), methyl diethanolamine (MDEA), and mixtures thereof.

[0221] The amount of the alkanolamine may be in the range of 0.1 to 5 wt.-%, based on the total amount of the aqueous admixture.

[0222] Kit of at least two parts

[0223] The invention further relates to a kit of at least two parts comprising

[0224] 1. a first part comprising the admixture as described above, andConstruction Research & Technology GmbH

[0225] 16

[0226] 2. a second part comprising a seed component selected from a calcium silicate hydrate (C-S-H) seed component, a calcium alumino silicate hydrate (C-A-S-H) seed component and a Ca(OH)2seed component, preferably a C-S-H seed component.

[0227] It has been found that the kit is suitable for modifying a property of cementitious construction compositions, the property modification being at least one of accelerating set and / or hardening after 8 to 24 h, retaining slump flow, reducing water demand, as outlined in detail above.

[0228] Seed components such as C-S-H seed components, C-A-S-H seed components and Ca(OH)2seed components are known as such. Their addition into a cementitious binder exhibits a seeding effect providing new nucleation sites within the pore space away from the particle surfaces. The seed components exhibit an accelerating effect without deteriorating final strength development.

[0229] Generally, C-A-S-H seeds (also referred to as “C-A-S-H nano-seeds”) can be synthesized by co-preci pitation using polycarboxylate superplasticizer (PCE) as dispersant. For example, the C-A-S-H seed component is obtained by dropwise adding an aqueous solution of a calcium source, an aqueous solution of a silicon source and an aqueous solution of an aluminum source to the solution of polycarboxylate superplasticizer (PCE), and adjusting the pH value to 10.0 to 13.5, and continuously stirring to obtain the C-A-S-H seeds suspension. Preferably, the calcium source is one or more of calcium formate, calcium acetate, calcium nitrate, calcium bicarbonate, and calcium gluconate. Preferably, the silicon source is one or more of sodium fluorosilicate, magnesium fluorosilicate, sodium silicate, sodium metasilicate, and potassium silicate. Preferably, the aluminum source is one or more of aluminum nitrate, sodium aluminate, and aluminum hydroxide.

[0230] The Ca(OH)2seed component may be in the form of an aqueous suspension comprising a) 5 to 65 wt.-%, relative to the total weight of the aqueous suspension, of calcium hydroxide in the form of suspended nano-particles,

[0231] b) optionally at least one organic compound for stabilizing the aqueous suspension against sedimentation, and

[0232] c) at least one salt of alkali metal or alkaline earth metal, preferably at least one of hydroxide, nitrate, nitrite, phosphate, phosphite, sulfate, thiocyanate, carbonate, bicarbonate, silicate, aluminate, formate, acetate, lactate, citrate, tartrate, and / orConstruction Research & Technology GmbH

[0233] 17

[0234] gluconate of alkali metal or alkaline earth metal, especially selected from sodium nitrate, sodium nitrite, sodium thiocyanate, lithium carbonate, sodium carbonate, sodium bicarbonate, sodium silicate, potassium silicate, sodium formate, sodium acetate, sodium lactate, sodium citrate, sodium tartrate, sodium gluconate, and / or calcium silicate hydrate.

[0235] In an embodiment, the C-S-H seed component contains calcium and silicon in a molar ratio Ca / Si of 0.1 to 2.2, preferably 0.5 to 1.7.

[0236] The C-S-H seed component may additionally include one or more transition metal ions, such as copper, or zinc.

[0237] It is believed that the seeding power of amorphous or semi-ordered calcium silicate hydrates is more pronounced than that of highly ordered or crystalline calcium silicate hydrates. Herein, “semi-ordered” means that the calcium silicate hydrate has a degree of order that lies intermediate between those of a macroscopic crystalline calcium silicate hydrate and amorphous calcium silicate hydrate. Semi-ordered calcium silicate hydrate has physical properties which differ both from the pure crystalline form and from the pure amorphous form.

[0238] In order to stabilize the amorphous or semi-ordered state of the calcium silicate hydrate, the C-S-H seed component may comprise a polymeric water-soluble dispersant.

[0239] In an embodiment, the C-S-H seed component comprises a finely dispersed mineral constituent stabilized by a polymeric water-soluble dispersant, the mineral constituent comprising an amorphous calcium silicate hydrate.

[0240] The C-S-H seed component comprises a calcium-silicate-hydrate, which is obtainable in the form of a suspension by reacting a water-soluble calcium compound with a water-soluble silicate compound in the presence of an aqueous solution which contains at least one polymeric dispersant.

[0241] Suitably, the water-soluble calcium compound is selected from calcium chloride, calcium nitrate, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium hypochloride, calcium iodate, calcium iodide, calcium lactate, calciumConstruction Research & Technology GmbH

[0242] 18

[0243] nitrite, calcium oxalate, calcium phosphate, calcium propionate, calcium silicate, calcium stearate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate calcium aluminate, tricalcium silicate and / or di calcium silicate.

[0244] The water-soluble calcium compound is preferably selected from calcium chloride and / or calcium nitrate. Advantage of these calcium compounds is their good solubility in water, low price and good availability.

[0245] Suitably, the water-soluble silicate compound is selected from sodium silicate, potassium silicate, waterglass, aluminum silicate, tricalcium silicate, dicalcium silicate, calcium silicate, silicic acid, sodium metasilicate and / or potassium metasilicate.

[0246] The water-soluble silicate compound is preferably selected from sodium metasilicate, potassium metasilicate and / or waterglass. Advantage of these silicate compounds is their extremely good solubility in water.

[0247] Alternatively, the C-S-H seed component comprises a calcium-silicate-hydrate, which is obtainable in the form of a suspension by reacting a calcium compound, preferably a calcium salt, most preferably a water-soluble calcium salt, with a silicon dioxide containing component under alkaline conditions, wherein the reaction is carried out in the presence of an aqueous solution of at least one polymeric dispersant.

[0248] The calcium salt can be for example calcium chloride, calcium nitrate, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium oxide, calcium hypochloride, calcium iodate, calcium iodide, calcium lactate, calcium nitrite, calcium oxalate, calcium phosphate, calcium propionate, calcium silicate, calcium stearate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate, calcium aluminate, tricalcium silicate and / or dicalcium silicate. Preferable are calcium hydroxide and / or calcium oxide because of their strong alkaline properties. In the case of neutral or acid calcium salts (e.g. calcium chloride or calcium nitrate) it is preferable to use a suitable base to adjust the pH-value to alkaline conditions (e.g. lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, magnesium hydroxide or any other earth alkali hydroxide).Construction Research & Technology GmbH

[0249] 19

[0250] Preferable is a pH-value higher than 8, more preferable higher than 9 and most preferable higher than 11. The pH-value is measured preferably at 25 °C and with a solid content of the suspension of 1 wt.-%.

[0251] As the silicon dioxide containing component, it is possible to use any material which contains silicon dioxide, for example microsilica, pyrogenic silica, precipitated silica, blast furnace slag, and / or quartz sand. Small particle sizes of the silicon dioxide containing material are preferable, especially particle sizes below 1 pm.

[0252] In a preferred embodiment, the silicon dioxide containing compound is selected from the group of microsilica, pyrogenic silica, precipitated silica, blast furnace slag and / or quartz sand. Preferable are microsilica, pyrogenic silica and / or precipitated silica, especially precipitated and / or pyrogenic silica.

[0253] It is preferable to apply mechanical energy, preferably by milling, to the reaction mixture in order to activate and / or accelerate the reaction of the calcium salt with the usually low water-soluble silicon dioxide containing component. The mechanical energy is also advantageous in order to reach the desired small particle sizes of the calcium silicate hydrates. The wording “milling” means any process in which high shear forces are exerted on the reaction mixture in order to accelerate the reaction and to obtain a suitable particle size. For example, milling can be carried out in a planet ball mill in a continuous or batch operation mode. Alternatively, an ultradisperser, preferably with a number of revolutions higher than 5.000 r.p.m. can be used. Also, it is possible to apply a so-called shaker equipment in which small grinding bodies, preferably smaller than 1 mm in diameter are put together with the reaction mixture into a receptacle and are shaken.

[0254] WO 2010 / 026155 describes a process for the preparation of a hardening accelerator composition by reaction of a water-soluble calcium compound with a water-soluble silicate compound. Said reaction is carried out in the presence of an aqueous solution which contains a water-soluble comb polymer suitable as a plasticizer for hydraulic binders.

[0255] In an embodiment, the C-S-H seed component comprises a finely dispersed mineral constituent stabilized by a polymeric water-soluble dispersant, the mineral constituent comprising a semi-ordered calcium silicate hydrate having an apparent crystallite size of 25 nm or less. The semi-ordered calcium silicate hydrate has an apparent crystallite sizeConstruction Research & Technology GmbH

[0256] 20

[0257] of 25 nm or less, preferably 15 nm or less, more preferably 5 nm or less, determined by means of X-ray diffraction analysis and subsequent Rietveld analysis. The apparent crystallite size is generally at least 1 nm, e.g. from 1 to 15 nm, or from 1 to 10 nm and particularly preferably from 1 to 5 nm.

[0258] The unit cells of the ordered regions of the semi-ordered calcium silicate hydrate, the size of which is described with the aid of their apparent crystallite size in the present patent application, are derived from crystalline calcium silicate hydrate phases (C-S-H). The unit cells of the ordered regions are preferably derived from 9 A-tobermorite (riversiderite), 10 A-tobermorite, 11 A-tobermorite (C / S 0.75 and 0.66), 14 A-tobermorite (plombierite), scawtite and / or xonotlite, and mixtures thereof. For the present purposes, it has been found to be a sufficient approximation for the determination of the apparent crystallite size to be based exclusively on the unit cell of 14 A-tobermorite (plombierite).

[0259] The C-S-H seed component comprises a product obtainable by wet milling of calcium-silicate-hydrate produced under hydrothermal conditions and where the milling was performed in presence of a water-soluble dispersant.

[0260] Examples for a composition containing semi-ordered C-S-H and a polymeric dispersant are given in WO 2018 / 154012 A1.

[0261] The mineral constituent can be obtained by reaction of a calcium hydroxide source, e.g. calcium oxide or calcium hydroxide, with a silicon dioxide source, e.g. silicon dioxide, under hydrothermal conditions, i.e., in the presence of water and at an elevated temperature of at least 100 °C and elevated pressure, advantageously in an autoclave. The mineral constituent produced in this way comprises semi-ordered calcium silicate hydrate, crystalline foreign phases including the unreacted crystalline foreign phases or the crystalline foreign phases formed in the reaction, e.g. quartz, portlandite, calcite, etc., and also X-ray-amorphous phases.

[0262] The production of the mineral constituent is advantageously carried out in a closed vessel, for example an autoclave, preferably at a temperature in the range from 100 to 400 °C, in particular from 110 to 300 °C or from 110 to 230 °C or from 130 to 200 °C or from 130 to 180 °C or from 155 to 180 °C or from 160 to 180 °C, and a pressure resulting therefrom. As calcium oxide or calcium hydroxide, it is possible to use, for example, quicklime, slacked lime, etc. Examples of suitable types of silicon dioxide are silica sandConstruction Research & Technology GmbH

[0263] 21

[0264] or quartz flour, microsilica, etc. In order to assist the reaction and shorten the reaction time, the starting materials are generally used with an average particle size of < 1 mm. The silicon dioxide source generally has a particle size d(99) in the range from 1 to 100 pm, in particular from 1 to 90 pm. The amount of calcium oxide or calcium hydroxide and silicon dioxide is generally selected so that the molar ratio of Ca / Si in the mineral constituent is in the range from 0.5 to 2.5, preferably from 0.8 to 2.2, more preferably from 1.0 to 2.0.

[0265] It has been found to be advantageous to use a foaming agent, in particular aluminum powder or a paste comprising metallic aluminum, in the hydrothermal production of the mineral constituent.

[0266] The mineral constituent is comminuted after the hydrothermal synthesis. Conventional apparatuses such as crushers and ball mills are suitable for this purpose. Comminution is carried out until a particle size (d(97)) of < 5 mm, preferably < 2 mm and in particular a particle size (d(97)) in the range of 0.05 to 5 mm, preferably 0.1 to 2 mm, in particular 0.3 to 1 mm, is attained. Comminution is carried out at a temperature of < 80 °C, preferably < 60 °C, more preferably < 50 °C.

[0267] The polymeric water-soluble dispersant used to stabilize the fine dispersion of the mineral constituent in the C-S-H seed component may be any dispersant, mostly an ionic or non-ionic polymer, also known as fluidity modifier or slump flow modifier, which is introduced into freshly mixed concrete to improve the workability of the concrete while reducing the amount of water needed for purposes of transportation, pouring and placing the concrete.

[0268] For the present purposes, a “water-soluble dispersant” is an organic water-soluble polymeric dispersant, i.e. it is an organic polymer which at 20 °C and atmospheric pressure has a solubility in water of at least 1 g / L, preferably at least 10 g / L, more preferably at least 100 g / L.

[0269] In an embodiment, the polymeric water-soluble dispersant is selected from

[0270] - polycarboxylate ethers,

[0271] - phosphorylated polycondensates being obtainable by a condensation reaction of an aromatic compound having a phosphate moiety, an alkoxylated hydroxyaryl compound having a polyoxyalkylene chain, and formaldehyde,Construction Research & Technology GmbH

[0272] 22

[0273] - non-ionic polymers having a carbon-containing backbone to which are attached pendant hydrolysable groups and polyether side chains, the hydrolysable groups upon hydrolysis releasing ionic anchoring groups,

[0274] - sulfonated melamine-formaldehyde condensates,

[0275] - lignosulfonates,

[0276] - sulfonated ketone-formaldehyde condensates,

[0277] - sulfonated naphthalene-formaldehyde condensates,

[0278] - phosphonate containing dispersants, and

[0279] - mixtures thereof.

[0280] These polymeric water-soluble dispersants are described in detail above.

[0281] In a preferred embodiment, the dispersant is selected from polycarboxylate ethers and phosphorylated polycondensates being obtainable by a condensation reaction of an aromatic compound having a phosphate moiety, an alkoxylated hydroxyaryl compound having a polyoxyalkylene chain, and formaldehyde.

[0282] Suitably, the pH value of the admixture is in the range of 5 to 8.

[0283] Process

[0284] The invention further relates to a process comprising adding the admixture as described above to a cementitious construction composition (hereinafter also referred to as “construction composition” for brevity). The process is suitable for modifying a property of a cementitious construction composition, wherein the property modification may be at least one of accelerating set and / or hardening after 8 to 24 h, retaining slump flow, reducing water demand.

[0285] Cementitious binder a)

[0286] The inventive construction composition comprises a cementitious binder a). The nature of the cementitious binder is not particularly limited. Generally, cementitious binders comprise one or more calcium silicate mineral phases and one or more crystalline calcium aluminate mineral phases.Construction Research & Technology GmbH

[0287] 23

[0288] Conveniently, the mineralogical phases are herein indicated by their cement notation. The primary compounds are represented in the cement notation by the oxide varieties: C for CaO, M for MgO, S for SiO2, A for AI2O3, $ for SO3, F for Fe2O3, and H for H2O.

[0289] The calcium silicate mineral phases may be selected from C3S (alite) and C2S (belite). The calcium silicate mineral phases provide primarily final strength properties.

[0290] The calcium aluminate mineral phases may be selected from C3A, C4AF and C12A7, in particular C3A and C4AF.

[0291] In an embodiment, the cementitious binder a) is Portland cement, in particular ordinary Portland cement (OPC). The term “Portland cement” denotes any cement compound containing Portland clinker, especially CEM I within the meaning of standard EN 197-1, paragraph 5.2. A preferred cement is ordinary Portland cement (OPC) according to DIN EN 197-1. The phases constituting Portland cement mainly are alite (C3S), belite (C2S), calcium aluminate (C3A), calcium ferroaluminate (C4AF) and other minor phases. Commercially available OPC may either contain calcium sulfate (< 7 wt.-%) or is essentially free of calcium sulfate (< 1 wt.-%). Generally, therefore, the commercially available cements lack sulfate for attaining an ideal ratio of aluminate to sulfate for formation of ettringite.

[0292] In an embodiment, the construction composition comprises a cementitious binder a) having less than 90 wt.-%, preferably less than 70 wt.-%, such as 10 to 90 wt.-%, preferably 30 to 70 wt.-%, of cement clinker, based on the total weight of the cementitious binder a).

[0293] The construction composition may comprise less than 200 kg of cementitious clinker, per cubic meter of the cementitious construction composition.

[0294] In an embodiment, the cementitious binder a) comprises a supplementary cementitious material. The supplementary cementitious material may be selected from a latent hydraulic binder and a pozzolanic binder.

[0295] The construction composition may comprise the supplementary cementitious material in an amount, relative to the weight of the cementitious binder, of 5 to 80 wt.-%, for example 15 to 70 wt.-%.Construction Research & Technology GmbH

[0296] 24

[0297] Generally, the latent hydraulic binder can be selected from industrial and / or synthetic slag, in particular from blast furnace slag, electrothermal phosphorous slag, steel slag and mixtures thereof.

[0298] The slag can be either industrial slag, i.e. waste products from industrial processes, or else synthetic slag. The latter can be advantageous because industrial slag is not always available in consistent quantity and quality.

[0299] Blast furnace slag (BFS) is a waste product of the glass furnace process. Other materials are granulated blast furnace slag (GBFS) and ground granulated blast furnace slag (GGBFS), which is granulated blast furnace slag that has been finely pulverized. Ground granulated blast furnace slag varies in terms of grinding fineness and grain size distribution, which depend on origin and treatment method, and grinding fineness influences reactivity here. The Blaine value is used as parameter for grinding fineness, and typically has an order of magnitude of 200 to 1000 m2kg1, preferably from 300 to 500 m2kg-1. Finer milling gives higher reactivity.

[0300] Herein, the expression “blast furnace slag” is intended to comprise materials resulting from all of the levels of treatment, milling, and quality mentioned (i.e. BFS, GBFS and GGBFS). Blast furnace slag generally comprises from 30 to 45 wt.-% of CaO, about 4 to 17 wt.-% of MgO, about 30 to 45 wt.-% of SiO2 and about 5 to 15 wt.-% of AI2O3, typically about 40 wt.-% of CaO, about 10 wt.-% of MgO, about 35 wt.-% of SiO2 and about 12 wt.-% Of AI2O3.

[0301] Electrothermal phosphorous slag is a waste product of electrothermal phosphorous production. It is less reactive than blast furnace slag and comprises about 45 to 50 wt-% of CaO, about 0.5 to 3 wt.-% of MgO, about 38 to 43 wt.-% of SiO2, about 2 to 5 wt-% of AI2O3 and about 0.2 to 3 wt.-% of Fe2O3, and also fluoride and phosphate.

[0302] Steel slag is a waste product of various steel production processes with greatly varying composition.

[0303] Generally, the pozzolanic binder can be selected from amorphous silica, preferably precipitated silica, fumed silica and microsilica, ground glass, metakaolin, aluminosilicates, fly ash, preferably brown-coal fly ash and hard-coal fly ash, naturalConstruction Research & Technology GmbH

[0304] 25

[0305] pozzolans such as tuff, trass and volcanic ash, calcined clays, burnt shale, rice husk ash, natural and synthetic zeolites and mixtures thereof.

[0306] Amorphous silica is preferably an X ray-amorphous silica, i.e. a silica for which the powder diffraction method reveals no crystallinity. The content of SiO2in the amorphous silica is advantageously at least 80 wt.-%, preferably at least 90 wt.-%.

[0307] Precipitated silica is obtained on an industrial scale by way of precipitating processes starting from water glass. Precipitated silica from some production processes is also called silica gel.

[0308] Fumed silica is produced via reaction of chlorosilanes, for example silicon tetrachloride, in a hydrogen / oxygen flame. Fumed silica is an amorphous SiO2powder of particle diameter from 5 to 50 nm with specific surface area of 50 to 600 m2g-1.

[0309] Microsilica is a by-product of silicon production or ferrosilicon production, and likewise consists mostly of amorphous SiO2powder. The particles have diameters of the order of magnitude of 0.1 pm. Specific surface area is of the order of magnitude of 15 to 30 m2g1-

[0310] Metakaolin is produced when kaolin is dehydrated. Whereas at from 100 to 200 °C kaolin releases physically bound water, at from 500 to 800 °C a dehydroxylation takes place, with collapse of the lattice structure and formation of metakaolin (AI2Si2O?). Accordingly pure metakaolin comprises about 54 wt.-% of SiO2and about 46 wt.-% of AI2O3.

[0311] Fly ash is produced inter alia during the combustion of coal in power stations. Class C fly ash (brown-coal fly ash) comprises according to WO 08 / 012438 about 10 wt.-% of CaO, whereas class F fly ash (hard-coal fly ash) comprises less than 8 wt.-%, preferably less than 4 wt.-%, and typically about 2 wt.-% of CaO.

[0312] Addition of the admixture to the cementitious binder adds 0.001 to 0.05 mol, preferably 0.002 to 0.04 mol, more preferably 0.003 to 0.03 mol, most preferably 0.004 to 0.02 mol, in particular 0.005 to 0.015 mol of dissolved sulfate ions, per 100 g of the cementitious binder. In instances where the cementitious binder already contains an inorganic readily soluble sulfate source, addition of the admixture results in an increase of the sulfate ionConstruction Research & Technology GmbH

[0313] 26

[0314] concentration originating from an inorganic readily soluble sulfate source beyond the concentration already contained.

[0315] Commercially available cementitious binders such as OPC may either contain calcium sulfate (< 7 wt.-%) or be essentially free of calcium sulfate (< 1 wt.-%). Calcium sulfate is an inorganic sulfate source which is not readily soluble as it has an aqueous solubility at 20 °C of less than 100 g / L. Besides inorganic not readily soluble sulfate sources such as calcium sulfate, commercially available cementitious binders may also contain inorganic readily soluble sulfate sources, i.e. inorganic sulfate sources having an aqueous solubility at 20 °C of 100 g / L or more. Typically, the amount of inorganic readily soluble sulfate sources contained in the cementitious binder is too low to achieve desired properties, like early strength, of construction compositions obtained therefrom.

[0316] The nature of the sulfate contained in a dry sample of the cementitious binder can be determined by methods capable of discriminating between the mineral phases constituting the cementitious binder. A useful method for this purpose is Rietveld refinement of an X-ray diffraction (XRD) powder pattern. This software technique is used to refine a variety of parameters, including lattice parameters, peak position, intensities and shape. This allows theoretical diffraction patterns to be calculated. As soon as the calculated diffraction pattern is almost identical to the data of an examined sample, precise quantitative information on the contained mineral phases can be determined. This allows for determining the amount of inorganic readily soluble sulfate in the cementitious binder.

[0317] Preferably, in the process of the invention, a compound of formula (VI), a polycondensate of the compound of formula (VI), and mixtures thereof are not added to the cementitious construction composition. Formula (VI) is:

[0318] R3

[0319]

[0320] (VI)

[0321] wherein

[0322] R1 is OH;Construction Research & Technology GmbH

[0323] 27

[0324] R2 is H, OH, C-i-C6alkoxy, -SO2X, -SO3X, -OSO3X, -PO, -PO3X2, -OPO3X2, -Z-COOX or -CH(OH)-SO3X;

[0325] R3 is H, COOX, C3-C6alkyl which may be substituted by 1 to 6 OH or Ci-C6alkoxy; m is 0 or 1; or

[0326] R1 and R2 taken together with the carbon atom to which they are attached form a carbonyl group provided m is 0;

[0327] R4 is COOY or SO3X;

[0328] X is selected from H or a cation equivalent Kawherein K is selected from an alkali metal, alkaline earth metal, zinc, iron, ammonium or phosphonium cation and a is 1 / n, wherein n is the valency of the cation;

[0329] Y is selected from X, Ci-Ce alkyl or phenyl; and

[0330] Z is CH2or CH(OH), in an amount of 0.101 to 3.5 wt.-%.

[0331] According to a preferred aspect, in the process of the invention,

[0332] (1) hydroxycarboxylic acids, a-carbonyl-carboxylic acids,

[0333] (2) di- or tri-carboxyl ic acids,

[0334] (3) phosphonoalkyl carboxylic acids,

[0335] (4) amino carboxylic acids,

[0336] (5) polymeric carboxylic acids,

[0337] (6) glyoxylic acid polycondensates and glyoxylic acid sulfite addition products, (7) phosphonate retarders and phosphate retarders, and

[0338] (8) mixtures and salts thereof

[0339] are not added to the cementitious construction composition.

[0340] In other words, the cementitious construction composition obtained from the inventive process is essentially free of (1) to (8) described above. Herein, the term ..essentially free of“ a compound means that the compound is not intentionally added to the composition and is present, if at all, in an amount that is non-functional in the composition.

[0341] Generally, the term ..essentially free of“ a compound denotes that the construction composition contains said compound in a total amount of less than 0.1 wt.-%, based on the total weight of the construction composition. Hence, the composition contains retarders (1) to (8) in an amount of less than 0.1 wt.-%, based on the total weight of the construction composition.Construction Research & Technology GmbH

[0342] 28

[0343] More stringent limitations may apply for highly active retarders, such as (1) hydroxycarboxylic acids, a-carbonyl-carboxylic acids, (2) di- or tri-carboxyl ic acids, (3) phosphonoalkyl carboxylic acids and (7) phosphonate retarders and phosphate retarders. Preferably, the construction composition contains the (1) hydroxycarboxylic acids, a-carbonyl-carboxylic acids, (2) di- or tri-carboxyl ic acids, (3) phosphonoalkyl carboxylic acids and (7) phosphonate retarders and phosphate retarders in an amount of less than 0.05 wt.-%, more preferably less than 0.025 wt.-%, based on the total weight of the construction composition, especially preferably does not contain said compound at all.

[0344] Conventional construction compositions typically require the addition of a retarder in order to prevent premature setting. It has surprisingly been found to be favorable that the construction compositions obtained by the inventive process are essentially free of such retarders, i.e. of the compounds (1) to (8) as listed above. This allows for obtaining construction compositions with improved early strength, without influencing late strength development. For example, the construction compositions are especially suitable as ready-mix (RMX) concrete.

[0345] (1) Hydroxycarboxylic acids, a-carbonyl-carboxylic acids,

[0346] The hydroxycarboxylic acids may be a-hydroxy monocarboxylic acids or salts thereof including glycolic acid, gluconic acid, and their salts and mixtures thereof.

[0347] The a-carbonyl-carboxylic acids may be a-carbonyl-carboxylic acids or salts thereof including glyoxylic acid, pyruvic acid, and their salts and mixtures thereof, such as sodium gluconate.

[0348] (2) Di- or tri-carboxyl ic acids

[0349] The di- or tri-carboxylic acids may be oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, malic acid, tartaric acid, citric acid, and their salts and mixtures thereof.Construction Research & Technology GmbH

[0350] 29

[0351] (3) Phosphonoalkyl carboxylic acids

[0352] Suitable phosphonoalkylcarboxylic acids include 1-phosphonobutane-1,2,4-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 3-phosphonobutane-1,2,4-tricarboxylic acid, 4-phosphonobutane-1,2,4-tricarboxylic acid, 2,4-diphosphonobutane-1,2,4-tricarboxylic acid, 2-phosphonobutane-1,2,3,4-tetracarboxylic acid, 1-methyl-2-phosphonopentane-1,2,4-tricarboxylic acid, or 1,2-phosphonoethane-2-dicarboxylic acid.

[0353] (4) Amino carboxylic acids

[0354] Suitable amino carboxylic acids include ethylenediamine tetra acetic acid, or nitrilotri acetic acid.

[0355] (5) Polymeric carboxylic acids

[0356] Suitable polymeric carboxylic acids include homopolymers of acrylic acid, homopolymers of methacrylic acid, polymaleic acid, copolymers such as ethylene / acrylic acid copolymer and ethylene / methacrylic acid copolymer; copolymers of acrylic acid and / or methacrylic acid with sulfo or sulfonate group containing monomers. In an embodiment, the sulfo or sulfonate group containing monomers are selected from the group of vinylsulfonic acid, (meth)allylsulfonic acid, 4-vinylphenylsulfonic acid or 2-acrylamido-2-methylpropylsulfonic acid (ATBS), with ATBS being particularly preferred. It is possible that one more of the before mentioned sulfo or sulfonate group containing monomers are contained in the copolymers.

[0357] In general, the molecular weight of the polymeric carboxylic acids is in the range of from 1000 to 30000 g / mol, preferably 1000 to 10 OOOg / mol. The molecular weight is measured by the gel permeation chromatography method (GPC) as indicated in detail in the experimental part.

[0358] (6) Glyoxylic acid polycondensates and glyoxylic acid sulfite addition products

[0359] The glyoxylic acid polycondensate may be an amine-glyoxylic acid condensate. The term “amine-glyoxylic acid condensate” is intended to mean a condensate of glyoxylic acid with a compound containing amino or amido groups reactive with aldehydes. ExamplesConstruction Research & Technology GmbH

[0360] 30

[0361] of compounds containing aldehyde-reactive amino or amido groups include urea, thiourea, melamine, guanidine, acetoguanamine, benzoguanamine and other acylguanamines and polyacrylamide.

[0362] The amine-glyoxylic acid condensate may be a melamine-glyoxylic acid condensate, a urea-glyoxylic acid condensate, a melamine-urea-glyoxylic acid condensate and / or a polyacrylamide-glyoxylic acid condensate. Urea-glyoxylic acid condensates are particularly preferred. Useful amine-glyoxylic acid condensates and their manufacture are described in WO 2019 / 077050.

[0363] In general, the amine-glyoxylic acid condensates have molecular weights in the range of 500 to 25000 g / mol, preferably 1000 to 10000 g / mol, particularly preferred 1000 to 5000 g / mol.

[0364] The glyoxylic acid sulfite addition product may be of the formula

[0365] OH XOOC— CH

[0366] U^A

[0367] wherein

[0368] X is, independently of one another, selected from H or a cation equivalent Catawherein Cat is a cation not especially limited, but preferably selected from an alkali metal, alkaline earth metal, zinc, iron, ammonium, or phosphonium cation, or mixtures thereof and a is 1 / n wherein n is the valence of the cation. The glyoxylic acid bisulfite adduct can be prepared as described in WO 2017 / 212045.

[0369] (7) Phosphonate retarders and phosphate retarders

[0370] Phosphonate retarders may be selected from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), amino-tris(methylenephosphonic acid) (ATMP) or [[(2-hydroxyethyl)imino]bis(methylene)]-bisphosphonic acid and mixtures thereof. The respective chemical formulae are given in the following:Construction Research & Technology GmbH

[0371] 31

[0372] O OH O II I II HO — P — C — P — OH

[0373] I I I OH CH3OH

[0374] (HEDP)

[0375] OH

[0376] (ATMP)

[0377]

[0378] [[(2-hydroxyethyl)imino]bis(methylene)]bisphosphonic acid

[0379] As outlined above, it has surprisingly been found that it is favorable to not add (1) to (8) to the cementitious construction composition such that the construction composition is essentially free of retarders. In an embodiment, the process further comprises not adding a carbonate source, preferably not adding both a carbonate source and a borate source. Construction compositions such obtained are essentially free of a carbonate source, preferably essentially free of both a carbonate source and a borate source. The advantages outlined above apply analogously for the absence of the carbonate source, and for the absence of both the carbonate source and the borate source.

[0380] The carbonate source may be selected from organic carbonates, alkali carbonate, and mixtures thereof.Construction Research & Technology GmbH

[0381] 32

[0382] The carbonate source may be an inorganic carbonate having an aqueous solubility of 0.1 g L-1or more at 25 °C. The aqueous solubility of the inorganic carbonate is suitably determined in water with a starting pH value of 7. It is understood that the pH value at the solubility limit is higher than the starting pH value.

[0383] The "inorganic carbonate" is intended to mean a salt of carbonic acid, i.e. , a salt which is characterized by the presence of a carbonate ion (CO32) and / or hydrogen carbonate ion (HCO3 ). The inorganic carbonate may be selected from alkali metal carbonates such as sodium carbonate, sodium bicarbonate, potassium carbonate or lithium carbonate. The inorganic carbonates may also include carbonates of nitrogenous bases such as guanidinium carbonate und ammonium carbonate.

[0384] Alternatively, the carbonate source may be selected from organic carbonates. "Organic carbonate" denotes an ester of carbonic acid. The organic carbonate is hydrolyzed in the presence of the cementitious system to release carbonate ions. The organic carbonate may be selected from ethylene carbonate, propylene carbonate, glycerol carbonate, dimethyl carbonate, di(hydroxyethyl)carbonate or a mixture thereof.

[0385] The borate source may include borax, boric acid, colemanite, and hexahydroborate.

[0386] The construction composition may additionally comprise dispersants other than the polycarboxylate ethers c-1) and the phosphorylated polycondensate c-2) as mentioned above (herein referred to as “further dispersant(s)”), especially a dispersant for cementitious mixtures like concrete or mortar, in order to accommodate different purposes such as to achieve still lower water to cement ratios. If such mixtures with other dispersants are used, c-1) and c-2) may be present in an amount of 1 to 99 wt.-%, preferably 5 to 95 wt.-%, more preferably at least about 30 wt.-%, relative to the total amount of dispersants.

[0387] Suitably, the further dispersant may be selected from

[0388] - sulfonated melamine-formaldehyde condensates,

[0389] - lignosulfonates,

[0390] - sulfonated ketone-formaldehyde condensates,

[0391] - sulfonated naphthalene-formaldehyde condensates,

[0392] - phosphonate containing dispersants,Construction Research & Technology GmbH

[0393] 33

[0394] - mixtures thereof.

[0395] Suitable sulfonated melamine-formaldehyde condensates are of the kind frequently used as plasticizers for hydraulic binders (also referred to as MFS resins). Sulfonated melamine-formaldehyde condensates and their preparation are described in, for example, CA 2 172 004 A1, DE 44 1 1 797 A1, US 4,430,469, US 6,555,683 and CH 686 186 and also in Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., vol. A2, page 131, and Concrete Admixtures Handbook - Properties, Science and Technology, 2. Ed., pages 411, 412. Preferred sulfonated melamine-formaldehyde condensates encompass (greatly simplified and idealized) units of the formula (VII):

[0396]

[0397] (VII)

[0398] wherein

[0399] n4 generally stands for 10 to 300. The molecular weight is situated preferably in the range from 2500 to 80000 g / mol. Additionally, to the sulfonated melamine units it is possible for other monomers to be incorporated by condensation. Particularly suitable is urea. Moreover, further aromatic units as well may be incorporated by condensation, such as gallic acid, aminobenzenesulfonic acid, sulfanilic acid, phenolsulfonic acid, aniline, ammoniobenzoic acid, dialkoxybenzenesulfonic acid, dialkoxybenzoic acid, pyridine, pyridinemonosulfonic acid, pyridinedisulfonic acid, pyridinecarboxylic acid and pyridinedicarboxylic acid. An example of melaminesulfonate-formaldehyde condensates are the Melment® products distributed by Master Builders Solutions Deutschland GmbH.

[0400] Suitable lignosulfonates are products which are obtained as by-products in the paper industry. They are described in Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed.,Construction Research & Technology GmbH

[0401] 34

[0402] vol. A8, pages 586, 587. They include units of the highly simplified and idealizing formula (VIII):

[0403] Un Un, Un oULn I2I3SO, oH OH

[0404]

[0405] Lignosulfonates have molecular weights of between 2000 and 100000 g / mol. In general, they are present in the form of their sodium, calcium and / or magnesium salts. Examples of suitable lignosulfonates are the Borresperse products distributed by Borregaard LignoTech, Norway.

[0406] Suitable sulfonated ketone-formaldehyde condensates are products incorporating a monoketone or diketone as ketone component, preferably acetone, butanone, pentanone, hexanone or cyclohexanone. Condensates of this kind are known and are described in WO 2009 / 103579, for example. Sulfonated acetone-formaldehyde condensates are preferred. They generally comprise units of the formula (IX) (according to J. Plank et al., J. Appl. Poly. Sci. 2009, 2018-2024):

[0407]

[0408] wherein

[0409] m2 and n5 are generally each 10 to 250, M2is an alkali metal ion, such as Na+, and the ratio m2:n5 is in general in the range from about 3:1 to about 1:3, more particularly aboutConstruction Research & Technology GmbH

[0410] 35

[0411] 1.2:1 to 1:1.2. Furthermore, it is also possible for other aromatic units to be incorporated by condensation, such as gallic acid, aminobenzenesulfonic acid, sulfanilic acid, phenolsulfonic acid, aniline, ammoniobenzoic acid, dialkoxybenzenesulfonic acid, dialkoxybenzoic acid, pyridine, pyridinemonosulfonic acid, pyridinedisulfonic acid, pyridinecarboxylic acid and pyridinedicarboxylic acid. Examples of suitable sulfonated acetone-formaldehyde condensates are the Melcret K1L products distributed by Master Builders Solutions Deutschland GmbH.

[0412] Suitable sulfonated naphthalene-formaldehyde condensates are products obtained by sulfonation of naphthalene and subsequent polycondensation with formaldehyde. They are described in references including Concrete Admixtures Handbook - Properties, Science and Technology, 2. Ed., pages 411 -413 and in Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed., vol. A8, pages 587, 588. They comprise units of the formula (X):

[0413]

[0414] Typically, molecular weights (MW) of between 1000 and 50000 g / mol are obtained. Furthermore, it is also possible for other aromatic units to be incorporated by condensation, such as gallic acid, aminobenzenesulfonic acid, sulfanilic acid, phenolsulfonic acid, aniline, ammoniobenzoic acid, dialkoxybenzenesulfonic acid, dialkoxybenzoic acid, pyridine, pyridinemonosulfonic acid, pyridinedisulfonic acid, pyridinecarboxylic acid and pyridinedicarboxylic acid. Examples of suitable sulfonated -naphthalene-formaldehyde condensates are the Melcret 500 L products distributed by Master Builders Solutions Deutschland GmbH.Construction Research & Technology GmbH

[0415] 36

[0416] Generally, phosphonate containing dispersants incorporate phosphonate groups and polyether side groups. Suitable phosphonate containing dispersants are those according to the following formula (XI):

[0417] R-(OA2)n6-eN-[CH2-PO(OM32)2]2

[0418] (XI)

[0419] wherein

[0420] R is H or a hydrocarbon residue, preferably a C1-C15 alkyl radical,

[0421] A2is independently C2-C18 alkylene, preferably ethylene and / or propylene, most preferably ethylene,

[0422] n6 is an integer from 5 to 500, preferably 10 to 200, most preferably 10 to 100, and M3is H, an alkali metal, 1 / 2 alkaline earth metal and / or an amine.

[0423] In an embodiment, the process comprises adding to the construction composition a filler, preferably selected from sand and aggregate. Generally, the fillers do not work as a binder.

[0424] Herein, the term “sand”, also termed “fine aggregates”, denotes aggregates, wherein most of the particles (e.g., at least 95% of the particles) have a particle size of 0 to 5 mm. In other words, “sand” denotes aggregates which pass a sieve having a nominal opening size of 5 mm.

[0425] The term “aggregate” denotes aggregates, wherein most of the particles (e.g., at least 95% of the particles) have a particle size of more than 5 to 40 mm, e.g. more than 5 to 30 mm or 10 to 20 mm. Generally, such aggregates may either be natural aggregates or crushed aggregates.

[0426] Usually, natural aggregates are dug or dredged from a pit, river, lake, seabed, or desert.

[0427] Usually, crushed aggregates are produced by crushing quarry rock, boulders, cobbles, or large-size gravel. Crushed air-cooled blast-furnace slag and recycled concrete both are also used as aggregates.

[0428] Generally, sand consists of natural sand or crushed stone having the particle size as described above; and aggregate consists of one or more gravels or crushed stone having the particle size as described above.Construction Research & Technology GmbH

[0429] 37

[0430] The composition of aggregates including sand varies, depending on the local sources and conditions. Naturally occurring aggregates are minerals, rocks, or mixtures thereof. A mineral is a naturally occurring solid substance with an orderly internal structure and a chemical composition that ranges within narrow limits. Rocks, which are classified as igneous, sedimentary, or metamorphic, depending on origin, are generally composed of several minerals. Weathering and erosion of rocks produce particles of stone, gravel, sand, silt, and clay.

[0431] Igneous rocks include granite, syenite, diorite, gabbro, peridotite, pegmatite, volcanic glass, felsite, and basalt.

[0432] Metamorphic rocks include marble, feldspar, metaquartzite, slate, phyllite, schist, amphibolite, hornfels, gneiss, and serpentinite.

[0433] Sedimentary rocks include calcite, travertine, dolomite, conglomerate, sandstone, claystone, siltstone, argillite, shale, and chert.

[0434] The most common constituent of sand in continental settings and non-tropical coastal settings is silica, usually in the form of quartz. Hence, the sand is preferably a silica-based sand, such as quartz sand.

[0435] In an embodiment, the process comprises adding to the cementitious construction composition a seed component selected from a C-S-H seed component, a C-A-S-H seed component and a Ca(OH)2seed component.

[0436] Regarding the C-S-H seed component, the C-A-S-H seed component and the Ca(OH)2seed component, the above-mentioned embodiments apply analogously.

[0437] The construction composition obtained by the inventive process may comprise 0.1 to 1.2 wt.-% of the C-S-H seed component, calculated as sum of CaO and SiO2, relative to the weight of the cementitious binder.

[0438] In an embodiment, the process comprises adding to the construction composition water in an amount, relative to the total amount of the construction composition, of 12 to 30 vol.-%, preferably 14 to 20 vol.-%.Construction Research & Technology GmbH

[0439] 38

[0440] In the admixture, the at least one superplasticizer may be at a concentration above the solubility limit of the superplasticizer in the aqueous phase. This can result in “salting out” of the superplasticizer, or, put otherwise, in the formation of a precipitate of the superplasticizer in the admixture. Without wishing to be bound by theory, it is believed that the inorganic sulfate source lowers the solubility of superplasticizer which in turn results in the “salting out” effect. Typically, “salting out” occurs in admixtures comprising a dissolved inorganic sulfate source providing a sulfate ion concentration above 0.5 mol / L.

[0441] The solubility limit at which “salting out" occurs can be determined by observing turbidity caused by the formed precipitate. The solubility limit can be determined by metering superplasticizer into an aqueous solution of the inorganic sulfate source and observing the over time for occurrence of turbidity. Occurrence of turbidity can be observed, e.g. using a Turbiscan device using static multiple light scattering. The salting out effect of the PEG side chains results in breaking hydrogen bridging bonds between the oxygen atoms of the PEG and the surrounding water molecules turning the hydrophilic side chains into hydrophobic PEGs. A microemulsion is thus formed.

[0442] It has surprisingly been found that the fresh concrete properties are improved in presence of a salted-out admixture (i.e. in the presence of an admixture comprising the dissolved inorganic sulfate source providing a sulfate ion concentration of above 0.5 mol / L)and that the admixture, even if salting-out of the superplasticizer occurred, can still be used for the intended purpose, e.g. for modifying a property of a cementitious construction composition, wherein the property modification may be at least one of accelerating set and / or hardening after 8 to 24 h, retaining slump flow, reducing water demand. Thus, the admixture can be used directly after preparation, or after storage.

[0443] Fig. 1 depicts sulfate-depletion peaks of aqueous construction compositions 1*, 2*, 3 and 4.

[0444] The invention is further illustrated by the accompanied figure and the examples that follow.Construction Research & Technology GmbH

[0445] 39

[0446] Examples

[0447] All wt.-% are understood as %bwoc, i.e., as relative to the mass of cementitious binder.

[0448] Materials

[0449] A C-S-H seed preparation comprising an amorphous C-S-H preparation was prepared according to example “Acc. 5” of table 2 of WO 2010 / 026155 A1. This C-S-H seed preparation is referred to as “CSH1” in the following.

[0450] “Superplaticizer-1” is a polycarboxylate ether based on a copolymer of acrylic acid and vinyl oxybutyl polyethylene glycol (VOBPEG) 3000. Superplaticizer-1 has an anionic charge density of 0.845 meq / g.

[0451] The basic recipe for aqueous construction compositions is as follows (ratio of water to cementitious binder = 0.55), to which further ingredients were added as described in detail below.

[0452] Material Amount [kg / m3]

[0453] Cementitious binder 378

[0454] Limestone powder 135

[0455] Water 208

[0456] Quartz sand (0.1-0.3 mm) 213

[0457] Quartz sand (0.3-1 mm) 88

[0458] Natural sand (0-4 mm) 1056

[0459] Crushed stones (2-5 mm) 260

[0460]

[0461] The crushed stones were dried in an oven at 70 °C for 50 h. Sands were dried in an oven at 140 °C for 68 h. Afterwards, the crushed stones and sands were stored at 20 °C for at least 2 d at 65% relative humidity. Cementitious binder, limestone powder, sand(s) and crushed stones were homogenized by stirring for 30 s at level 1 before adding the water.Construction Research & Technology GmbH

[0462] 40

[0463] Mixing procedure 1 (for Example 1 and 3, and experiments # 22, 25, 28, 31 of Ex. 2)

[0464] Where present, superplasticizer, glycerol, Na2SO4and C-S-H seed component were presolved in the mixing water (resulting in a higher dilution, i.e. lower concentration, of the components in the mixing water, compared to the admixture as described in mixing procedure 2 below) and then added to the homogenized mixture of cementitious binder, limestone powder, sand(s) and crushed stones. The resulting mixture was stirred for 1 min at level 1 and for 3 min at level 2 to obtain an aqueous construction composition.

[0465] Mixing procedure 2 (for experiments # 23, 26, 29, 32 of Example 2)

[0466] An admixture of superplasticizer, glycerol and Na2SO4was prepared. The formulation was added to the mixing water within 30 s. The resulting liquid was added to the homogenized mixture of cementitious binder, limestone powder, sand(s) and crushed stones. The resulting mixture was stirred for 1 min at level 1 and for 3 min at level 2 to obtain an aqueous construction composition.

[0467] Methods

[0468] Testing procedure - Mini-slump flow

[0469] The used procedure is analogous to DIN EN 12350-2, with the modification that a minislump cone (height: 15 cm, bottom width: 10 cm, top width: 5 cm) was used instead of a conventional Abrams cone. 2 L of the aqueous construction composition were filled into the mini-slump cone. The cone was filled completely immediately after mixing. Afterwards, the cone was placed on a flat surface, and lifted, and the slump flow of the aqueous construction composition was measured (diameter). The slump flow values shown in the Tables below are average values of two measurements of diameters (90° angle of the spread without vibration). The slump flow of all mixes was adjusted to 25 cm by adjusting the dosage of the superplasticizer (dosage calculated as active substance) to allow for comparability.

[0470] Testing procedure - Early strength development

[0471] The aqueous construction compositions were each filled into steel prisms (16 / 4 / 4 cm), and after 16 h or 24 h at a temperature of 20 °C and relative humidity of 65%, a hardenedConstruction Research & Technology GmbH

[0472] 41

[0473] prism was obtained. The hardened prism was demolded and compressive strength was measured according to DIN EN 196-1.

[0474] Testing procedure - Late strength development

[0475] The aqueous construction compositions were each filled into steel prisms (16 / 4 / 4 cm), and after 28 d or 71 d at a temperature of 20 °C and relative humidity of 65%, a hardened prism was obtained. The hardened prism was demolded, and compressive strength was measured according to DIN EN 196-1.

[0476] Example 1

[0477] Aqueous construction compositions according to the basic recipe as described above were prepared as shown in Table 1. The aqueous construction compositions were investigated for their compressive strength after 16 h and 24 h, and regarding their initial slump flow.Table 1.

[0478] Mini slump CSH1 Na2SO4 Glycerol c (SO42-)[1]c (SO42-)[2]m (SP-1)[3]CS 16 h M CS 24 h W Cementitious binder # flow (initial)

[0479] [wt.-%] [wt.-%] [wt.-%] [mol] [mol] [g] [MPa] [MPa]

[0480] [cm] 1* 0 0 0 0 0.006 0.21 8.31 13.54 24.7 2* 2 0 0 0 0.006 0.29 12.25 19.85 25.1 Ozarow

[0481] 3** 0 1 0 0.007 0.013 0.21 11.96 19.94 16.5 CEM I 42, 5N I5’

[0482] 4** 0 1 0.5 0.007 0.013 0.21 12.32 19.21 16.3 5** 2 1 0.5 0.007 0.013 0.29 17.71 25.85 15.8 6* 0 0 0 0 0.004 0.165 6.62 13.91 23.9 7* 2 0 0 0 0.004 0.245 11.38 18.94 25.4 Ozarow

[0483] 8** 0 1 0 0.007 0.011 0.165 8.90 17.38 21.4 CEM ll / B-V 42,5R[6]

[0484] 9** 0 1 0.5 0.007 0.011 0.165 12.89 18.39 17.7 10** 2 1 0.5 0.007 0.011 0.245 17.54 23.86 22.4 11* 0 0 0 0 0.003 0.15 4.49 6.54 25.1 12* 2 0 0 0 0.003 0.23 6.54 9.6 24.3 Ozarow

[0485] 13** 0 1 0 0.007 0.010 0.15 5.79 8.4 16.7 CEM lll / A 42, 5N

[0486] -j 4** 0 1 0.5 0.007 0.010 0.15 5.33 7.89 18.4 15** 2 1 0.5 0.007 0.010 0.23 7.51 11.89 19.5

[0487]

[0488] Mini slump CSH1 Na2SO4 Glycerol c (SO42-)[1]c (SO42-)[2]m (SP-1) P] CS 16 h M CS 24 h W Cementitious binder # flow (initial)

[0489] [wt.-%] [wt.-%] [wt.-%] [mol] [mol] [g] [MPa] [MPa]

[0490] [cm] 16* 0 0 0 0 0.004 0.18 5.21 11.46 22.5 17* 2 0 0 0 0.004 0.26 9.52 14.92 23.2 Ozarow

[0491] 18** 0 1 0 0.007 0.011 0.18 7.72 14.6 17.3 CEM IV / A(V) 32, 5R

[0492] 19** 0 1 0.5 0.007 0.011 0.18 10.15 14.70 17.9 20** 2 1 0.5 0.007 0.011 0.26 13.73 18.42 22.4

[0493]

[0494] 0] Amorphous C-S-H preparation

[0495] [1] Increase of sulfate ion concentration, per 100 g of cementitious binder

[0496] [2] Total sulfate ion concentration, per 100 g of cementitious binder

[0497] [3] Amount of Superplasticizer-1 , per 100 g of cementitious binder, total amount of superplasticizer from CSH1 and SP-1 added to the mixing water 5 [4] Compressive strength after 16 / 24 h, determined at 20 °C

[0498] [5] Portland cement

[0499] [6] Fly ash blended cement

[0500] [7] Slag blended cement

[0501] [8] Fly ash blended cement

[0502] 0 * comparative example

[0503] ** reference exampleConstruction Research & Technology GmbH

[0504] 44

[0505] It can be seen from the results shown in Table 1 that addition of sulfate (see examples 3, 8, 13, 18) improves early strength, compared to examples 1, 6, 11, 16 containing no sulfate. Addition of sulfate and glycerol (see examples 4, 9, 14, 19) further improves early strength. Addition of sulfate, glycerol and a C-S-H seed component (see examples 5, 10, 15, 20) still further improves early strength.

[0506] Generally, typical cements lack sulfate for early calcium silicate hydrate (C-S-H) reaction resulting in poisoning of C-S-H nucleation once aluminate is dissolved from C3A and C4AF. Additional amounts of soluble sulfate can bind aluminate via the formation of ettringite. A measure for determining poisoning of C-S-H nucleation is to determine the sulfate-depletion peak of a construction composition. An early sulfate-depletion peak corresponds to a faster precipitation of ettringite and a higher dissolution of C3A.

[0507] Sulfate-depletion peaks of aqueous construction compositions 1*, 2*, 3 and 4 were determined. The results are shown in Fig. 1. It can be seen in Fig. 1 that higher sulfate-depletion peaks were obtained earlier for reference examples 4 and 5, compared to comparative examples 1* and 2*.

[0508] Example 2

[0509] Admixture 1 was prepared according to the following recipe:

[0510] - Na2SO4 10 wt.-%

[0511] - Glycerol 5 wt.-%

[0512] Superplasticizer-1 1 wt.-% (calculated as active substance)

[0513] - Water: 84 wt.-%

[0514] The solids content of admixture 1 was determined to be 15.8 wt.-% using the method described above.

[0515] Aqueous construction compositions comprising cementitious binders having the properties shown in Table 2 were prepared according to the basic recipe as described above. See Table 3. The aqueous construction compositions were adjusted to the same initial slump flow of 25 cm by the amount of Superplasticizer-1 added, and their slump flow after 15 min, 30 min, 60 min, 90 min and 120 min was determined, as well as their early strength development was determined. The results are shown in Table 4.Table 2.

[0516] Ozarow CEM I 42, 5N Ozarow CEM II B V42,5R Ozarow CEM III A 42,5 N Ozarow CEM IVA V32,5R Cement Composition M [g / mol] wt.-% mol / 100g wt.-% mol / 100g wt.-% mol / 100g wt.-% mol / 100g C3A 270 5.4 0.020 3.3 0.012 3 0.011 3.3 0.012 C4AF 486 7.9 0.016 5.8 0.012 4.2 0.009 6 0.012 Gypsum 172 0.1 0.001 0.5 0.003 1.4 0.008 0.4 0.002 Anhydride 136 0.5 0.004 0.4 0.003 0.1 0.001 0.6 0.004 Hemihydrate 154 2.0 0.013 1.9 0.012 0.2 0.001 2.3 0.015 K2SO4[1]176 0.8 0.005 0.6 0.003 0.5 0.003 0.6 0.003 K3Na(SO4)2[1]336 0.4 0.001 0.3 0.001 0.1 0.000 0.3 0.001

[0517]

[0518] 1] Considered a readily soluble sulfate sourceTable 3.

[0519] SP-1[0]Na2SO4 Glycerol Admixture 1 c (SO?-)[1]c (SO?)[2]m (SP-1) P] Cementitious binder #

[0520] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [mol] [mol] [g] 21* 0.23 0 0 0 0 0.006 0.23 Ozarow

[0521] 22** 0.29 1 0.5 0 0.007 0.013 0.29 CEM I 42, 5N M

[0522] 23 0.15 via Adm. 1[5]via Adm. 1[5]1 .6 I6! 0.007 0.013 0.25 24* 0.19 0 0 0 0 0.004 0.19 Ozarow

[0523] 25** 0.23 1 0.5 0 0.007 0.011 0.23 CEM ll / B-V 42,5R[7]

[0524] 26 0.06 via Adm. 1[5]via Adm. 1[5]1 .6 [61 0.007 0.011 0.16 27* 0.13 0 0 0 0 0.003 0.13 Ozarow

[0525] 28** 0.17 1 0.5 0 0.007 0.010 0.17 CEM lll / A 42, 5N

[0526] 29 0 via Adm. 1[5]via Adm. 1[5]1 .6 [61 0.007 0.010 0.10 30* 0.20 0 0 0 0 0.004 0.20 Ozarow

[0527] 31** 0.24 1 0.5 0 0.007 0.011 0.24 CEM IV / A(V) 32, 5R

[0528] 32 0.06 via Adm. 1[5]via Adm. 1[5]1 .6 [61 0.007 0.011 0.16

[0529]

[0530] ] Superplasticizer-1 [5] Adm. 1 = Admixture 1

[0531] [1] Increase of sulfate ion concentration, per 100 g of cementitious binder [6] As active substance

[0532] [2] Total sulfate ion concentration, per 100 g of cementitious binder [7] Fly ash blended cement

[0533] 5 [3] Total amount of Superplasticizer-1 , per 100 g of cementitious binder [8] Slag blended cement

[0534] [4] Portland cement [9] Fly ash blended cement

[0535] * comparative example ** reference exampleTable 4.

[0536] Slump flow Slump flow Slump flow Slump flow Slump flow Slump flow CS 24 h I1’ #

[0537] initial [cm] 15 min [cm] 30 min [cm] 60 min [cm] 90 min [cm] 120 min [cm] [MPa] 21* 24.9 28.9 27.4 25.7 20.1 15.1 15.96 22** 22.7 22.9 21.5 20.7 17.3 13.3 24.05 23 24.8 26.1 26.0 22.9 20.7 18.1 24.49 24* 24.5 24.4 24.2 19.5 14.9 10.5 15.84 25** 23.9 21.7 19.9 15.9 13.4 10.4 21.53 26 25.3 23.1 22.2 21.8 202 15.5 21.78 27* 24.1 16.1 14.1 10.2 n.d. ra n.d. ra 6.13 28** 23.8 17.9 14.6 10.3 n.d. P] n.d. ra 9.21 29 29.4 24.7 20.3 11.2 10.3 n.d. ra 9.04 30* 23.7 29.4 27.6 23.8 22.7 15.1 12.12 31** 23.9 24.2 22.7 19.7 16.8 14.3 16.57 32 24.9 23.9 22.1 18.9 15.7 13.9 16.35

[0538]

[0539] 1] Compressive strength after 24 h, determined at 20 °C

[0540] [2] n.d. = not determined

[0541] * comparative example

[0542] 5 ** reference exampleConstruction Research & Technology GmbH

[0543] 48

[0544] It can be seen from the results shown in Table 4 that addition of admixture 1 results in improved early strength (see inventive examples 23, 26, 29, 32), compared to comparative examples 21, 24, 27, 30 in which the components were added directly to the mixing water (instead of adding the admixture to the mixing water). Additionally, dosage efficiency and slump flow retention increased in inventive examples 23, 26, 29, 32 in which admixture 1 was added.

[0545] Example 3

[0546] Aqueous construction compositions according to the basic recipe as described above were prepared for various cementitious binders as shown in Table 5. The early strength development was determined for all aqueous construction compositions. The results are shown in Table 5.Table 5.

[0547] Na2SO4 SP-1 in Glycerol CSH1 CS 16 h [2] CS 24 h P] Slump f.[3]# Cementitious binder

[0548] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [MPa] [MPa] [cm] 33* Karlstadt CEM II C-M S-LL 42,5 N 0 0.22 0 0 3.67 9.49 24.7 34* Holcim Altkirch CEM II A-LL 52,5 R 0 0.22 0 0 16.74 26.08 22.7 35* Lafarge Le Teil CEM II A-LL 52,5 R 0 0.18 0 0 15.64 24.99 22.9 36* Schelcklingen CEM II A-LL 42,5 N 0 0.21 0 0 11.09 19.59 24.5 37* Burglengenfeld CEM II A-LL 52,5 R 0 0.27 0 0 18.24 28.04 21.3 38* Karlstadt CEM III A 52,5 N-SR 0 0.19 0 0 4.23 10.54 20.6 39* Rohrdorf CEM II A-S 42,5 R I10’ 0 0.21 0 0 11.9 18.96 23.1 40* Ozarow CEM I 42,5 N I11’ 0 0.21 0 0 8.31 13.54 24.7 41* Ozarow CEM I l / B-V 42,5 R I12’ 0 0.17 0 0 6.62 13.91 23.9 42* Ozarow CEM lll / A 42,5 N I13’ 0 0.15 0 0 4.49 6.54 25.1 43* Ozarow CEM IV / A(V) 32,5 R I14’ 0 0.18 0 0 5.21 11.46 22.5 44* Karlstadt CEM II C-M S-LL 42,5 N 0 0.00 0 2 7.21 13.39 27.9 45* Holcim Altkirch CEM II A-LL 52,5 R 0 0.22 0 2 25.96 37.72 25.1 46* Lafarge Le Teil CEM II A-LL 52,5 R 0 0.18 0 2 26.46 30.72 24.1 47* Schelcklingen CEM II A-LL 42,5 N 0 0.21 0 2 19.24 25.84 27.8 48* Burglengenfeld CEM II A-LL 52,5 R 0 0.27 0 2 26.68 34.78 24.1 49* Karlstadt CEM III A 52,5 N-SR 0 0.19 0 2 11.82 16.96 25.1 50* Rohrdorf CEM II A-S 42,5 R I10’ 0 0.21 0 2 17.75 26.38 21.3

[0549]

[0550] Na2SO4 SP-1 [1] Glycerol CSH1 CS 16 h [2] CS 24 h P] Slump f.[3]# Cementitious binder

[0551] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [MPa] [MPa] [cm] 51* Ozarow CEM I 42,5 N t1 1’ 0 0.21 0 2 12.25 19.85 25.1 52* Ozarow CEM I l / B-V 42,5 R t12’ 0 0.17 0 2 11.38 18.94 25.4 53* OzarowCEM lll / A 42,5 N t13’ 0 0.15 0 2 6.54 9.6 24.3 54* Ozarow CEM IV / A(V) 32,5 R t14’ 0 0.18 0 2 9.52 14.92 23.2 55** Karlstadt CEM II C-M S-LL 42,5 N 1

[0015] 0.22 0 0 3.76 11.37 19.8 56** Holcim Altkirch CEM II A-LL 52,5 R t5’ 1

[0015] 0.22 0 0 24.48 33.71 16.3 57** Lafarge Le Teil CEM II A-LL 52,5 R 1

[0015] 0.18 0 0 25.69 30.56 20.7 58** Schelcklingen CEM II A-LL 42,5 N 1

[0015] 0.21 0 0 15.60 22.73 20.8 59** Burglengenfeld CEM II A-LL 52,5 R 1

[0015] 0.27 0 0 28.86 38.39 18.3 60** Karlstadt CEM III A 52,5 N-SR 1

[0015] 0.19 0 0 6.40 15.79 13.5 61** Rohrdorf CEM II A-S 42,5 R t10’ 1

[0015] 0.21 0 0 16.69 25.70 18.4 62** Ozarow CEM I 42,5 N t1 1’ 1

[0015] 0.21 0 0 11.96 19.94 16.5 63** Ozarow CEM I l / B-V 42,5 R t12’ 1

[0015] 0.17 0 0 8.90 17.38 21.4 64** OzarowCEM lll / A 42,5 N t13’ 1

[0015] 0.15 0 0 5.79 8.39 16.7 65** Ozarow CEM IV / A(V) 32,5 R t14’ 1

[0015] 0.18 0 0 7.72 14.63 17.3 66** Karlstadt CEM II C-M S-LL 42,5 N 1

[0015] 0.22 0.5 0 4.74 13.84 17.9 67** Holcim Altkirch CEM II A-LL 52,5 R 1

[0015] 0.22 0.5 0 25.29 33.02 14.2 68** Lafarge Le Teil CEM II A-LL 52,5 R 1

[0015] 0.18 0.5 0 24.94 31.84 12.7

[0552]

[0553] Na2SO4 SP-1 [1] Glycerol CSH1 CS 16 h I2’ CS 24 h P] Slump f.[3]# Cementitious binder

[0554] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [MPa] [MPa] [cm] 69** Schelcklingen CEM II A-LL 42,5 N 1

[0015] 0.21 0.5 0 16.18 22.75 15.2 70** Burglengenfeld CEM II A-LL 52,5 R 1

[0015] 0.27 0.5 0 27.11 36.73 16.5 71 ** Karlstadt CEM III A 52,5 N-SR 1

[0015] 0.19 0.5 0 8.44 15.79 13.1 72** Rohrdorf CEM II A-S 42,5 R I10’ 1

[0015] 0.21 0.5 0 17.42 26.26 14.1 73** Ozarow CEM I 42,5 N I11’ 1

[0015] 0.21 0.5 0 12.32 19.21 16.3 74** Ozarow CEM I l / B-V 42,5 R I12’ 1

[0015] 0.17 0.5 0 12.89 18.39 17.7 75** OzarowCEM lll / A 42,5 N I13’ 1

[0015] 0.15 0.5 0 5.33 7.89 18.4 76** Ozarow CEM IV / A(V) 32,5 R I14’ 1

[0015] 0.18 0.5 0 10.15 14.7 17.9 77** Karlstadt CEM II C-M S-LL 42,5 N 1

[0015] 0.22 0.5 2 11.01 17.15 20.4 78** Holcim Altkirch CEM II A-LL 52,5 R 1

[0015] 0.22 0.5 2 31.13 38.49 16.3 79** Lafarge Le Teil CEM II A-LL 52,5 R 1

[0015] 0.18 0.5 2 34.02 38.09 14.7 80** Schelcklingen CEM II A-LL 42,5 N 1

[0015] 0.21 0.5 2 22.19 30.72 17.2 81** Burglengenfeld CEM II A-LL 52,5 R 1

[0015] 0.27 0.5 2 35.68 43.67 17.1 82** Karlstadt CEM III A 52,5 N-SR 1

[0015] 0.19 0.5 2 14.93 21.06 17.6 83** Rohrdorf CEM II A-S 42,5 R I10’ 1

[0015] 0.21 0.5 2 33.52 33.52 17.7 84** Ozarow CEM I 42,5 N I11’ 1

[0015] 0.21 0.5 2 17.71 25.85 15.8 85** Ozarow CEM I l / B-V 42,5 R I12’ 1

[0015] 0.17 0.5 2 17.54 23.86 22.4 86** OzarowCEM lll / A 42,5 N I13’ 1

[0015] 0.15 0.5 2 7.51 11.89 19.5

[0555]

[0556] Na2SO4 SP-1 [1] Glycerol CSH1 CS 16 h I2’ CS 24 h P] Slump f.[3]# Cementitious binder

[0557] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [MPa] [MPa] [cm] 87** Ozarow CEM IV / A(V) 32,5 R I14’ 1

[0015] 0.18 0.5 2 13.73 18.42 22.4

[0558]

[0559] 1] Superplasticizer-1

[0560] [2] Compressive strength after 16 / 24 h, determined at 20 °C

[0561] [3] Mini slump flow (initial)

[0562] [4] 0.0071 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0563] 5 [5] 0.0057 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0564] [6] 0.0043 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0565] [7] 0.0088 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0566] [8] 0.0054 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0567] [9] 0.0023 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0568] 0

[0010] 0.0014 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0569]

[0011] 0.0060 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0570]

[0012] 0.0040 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0571]

[0013] 0.0030 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0572]

[0014] 0.0040 mol of readily soluble sulfate sources have an aqueous solubility at 20 °C of 100 g / L or more, per 100 g of cementitious binder

[0573] 5

[0015] Corresponding to an increase of sulfate ion concentration of 0.007 mol, per 100 g of cementitious binder

[0574] ‘comparative example

[0575] ** reference exampleConstruction Research & Technology GmbH

[0576] 53

[0577] Compatibility with various cementitious binders has been shown.

[0578] Example 4

[0579] Admixtures with compositions as given in Table 6 below were prepared according to mixing procedure 2 (see above). The solids contents and pH values of the obtained admixtures are shown in Table 6 below. The obtained admixtures were tested in construction compositions obtained according to the “basic recipe for aqueous construction compositions” as described above. Within Example 4, the cementitious binder was Mergelstetten CEM I 52, 5R, and the liquid dosage of the admixture in the construction composition was 4 wt.-%.

[0580] The obtained construction compositions were investigated for their slump flow after 0 min, 15 min, 30 min, 45 min, 60 min, 75 min and 90 min, as well for as their early strength development. The results are shown in Table 7.Table 6.

[0581] Na2SO4 NaHSO4I1’ Superplasticizer[2]Glycerol H2O Solids content pH at 21 °C #

[0582] [PPW] [PPW] [PPW] [PPW] [PPW] [%] [-] 88 50 0 49 12.5 388.5 17.5 5.15 89 25 25 49 12.5 388.5 17.5 1.40 90 0 50 49 12.5 388.5 17.5 0.80 91 45 5 49 12.5 388.5 17.5 2.19 92* 0 0 49 0 451.0 5.0 5.60

[0583]

[0584] [1] Purity 92%

[0585] [2] Polycarboxylate ether having a charge density of 1 .49 meq / g; solids content: 51%

[0586] ppw = parts per weight

[0587] 5 ‘comparative exampleTable 7.

[0588] Slump flow Slump flow Slump flow Slump flow Slump flow Slump flow Slump flow CS 16 h I1’ CS 24 h I1’ #

[0589] initial [cm] 15 min [cm] 30 min [cm] 45 min [cm] 60 min [cm] 75 min [cm] 90 min [cm] [MPa] [MPa] 88 272 232 211 188 172 163 149 23.4 35.8 89 268 228 218 183 175 162 149 21.8 33.2 90 260 267 251 242 224 217 197 20.5 31.8 91 273 238 221 200 193 174 162 23.4 34.6 92* 298 327 291 274 238 221 202 19.1 29.1

[0590]

[0591] 1] Compressive strength after 24 h, determined at 20 °C

[0592] ‘comparative exampleConstruction Research & Technology GmbH

[0593] 56

[0594] The sulfate-containing admixures (see examples 88 to 91) show higher early strength and improved slump retention compared to sulfate-free comparative admixture 92*. Excellent slump retention was observed at low pH values (see example 90).

Claims

Construction Research & Technology GmbH57Claims1. An aqueous admixture for cementitious construction compositions, comprising i) a dissolved inorganic sulfate source providing a sulfate ion concentration of 0.3 to 1.0 mol / L, preferably 0.5 to 1.0 mol / L, more preferably 0.5 to 0.7 mol / L, andii) at least one superplasticizer in an amount in the range of 0.1 to 34 g / L, preferably 0.5 to 30 g / L, more preferably 0.5 to 18 g / L,the aqueous admixture having a solids content of less than 20 wt.-%, preferably less than 16 wt.-%.

2. The admixture of claim 1 , wherein the inorganic sulfate source is selected from lithium sulfate, lithium hydrogensulfate, sodium sulfate, sodium hydrogensulfate, potassium sulfate, potassium hydrogensulfate, aphthitalite (K3Na(SC>4)2), iron (II) sulfate, copper sulfate, zinc sulfate, and mixtures thereof.

3. The admixture of claim 1 or 2, having a pH value in the range of 0.5 to 7.

4. The admixture of any one of the preceding claims, wherein the at least one superplasticizer has a charge density in the range of from 0.5 to 5.0 meq / g, preferably 0.5 to 4.0 meq / g, more preferably 0.5 to 3.0 meq / g.

5. The admixture of any one of the preceding claims, wherein the at least one superplasticizer is selected fromc-1) polycarboxylate ethers,c-2) phosphorylated polycondensates obtainable by condensation reaction of c-2-1) an aromatic compound having a phosphate moiety,c-2-2) an alkoxylated hydroxyaryl compound, andc-2-3) formaldehyde,andc-3) mixtures thereof.

6. The admixture of any one of the preceding claims, additionally comprising at least one of a polyol and an alkanolamine.Construction Research & Technology GmbH587. The admixture of claim 6, wherein the polyol is selected from alkanediols, alkanetriols, sugar polyols, and mixtures thereof.

8. The admixture of claim 6 or 7, wherein the alkanolamine is selected from diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), triisopropanolamine (TIPA), N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (THEED), methyl diethanolamine (MDEA), and mixtures thereof, preferably triisopropanolamine (TIPA), diethanolamine (DEA) N,N,N',N'-tetrakis(2- hydroxyethyl)ethylenediamine (THEED), methyl diethanolamine (MDEA), and mixtures thereof.

9. A kit of at least two parts comprising1. a first part comprising the admixture of any one of claims 1 to 8, and 2. a second part comprising a seed component selected from a C-S-H seed component, a C-A-S-H seed component and a Ca(OH)2seed component.

10. A process comprising adding the admixture of any one of claims 1 to 8 to a cementitious construction composition.

11. The process of claim 10, wherein the cementitious construction composition comprises a cementitious binder having less than 90 wt.-%, preferably less than 70 wt.-%, of cement clinker, based on the total weight of the cementitious binder.

12. The process of claim 10 or 11 , wherein the cementitious binder comprises a supplementary cementitious material selected from a latent hydraulic binder and a pozzolanic binder.

13. The process of any one of claims 10 to 12, comprising adding to the cementitious construction composition a filler, preferably selected from sand and aggregate.

14. The process of any one of claims 10 to 13, comprising adding to the cementitious construction composition a seed component selected from a C-S-H seed component, a C-A-S-H seed component and a Ca(OH)2seed component.

15. The process of claim 14, wherein the C-S-H seed component contains calcium and silicon in a molar ratio Ca / Si of 0.1 to 2.2, preferably 0.5 to 1.7.Construction Research & Technology GmbH5916. The process of claim 14 or 15, wherein the C-S-H seed component comprises a finely dispersed mineral constituent stabilized by a polymeric water-soluble dispersant, the mineral constituent comprising a semi-ordered calcium silicate hydrate having an apparent crystallite size of 25 nm or less, preferably 15 nm or less.

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