EP4673414A1 - Improved shotcrete compositions - Google Patents

Abstract

A process comprises providing a cementitious composition; admixing an alkali-free, aluminum-based shotcrete accelerator to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden. The cementitious composition comprises a colloidal suspension of a low-solubility salt of at least one polyvalent metal cation selected from Fe³⁺, Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Al³⁺ and mixtures thereof, and at least one anion which is able to form a low-solubility salt with the polyvalent metal cation, wherein the anion is selected from carbonate, oxalate, phosphate, polyphosphate, phosphite, borate, aluminate, sulfate, fluoride and mixtures thereof, with the proviso that where the cation comprises Ca²⁺ and the anion comprises aluminate, the molar ratio of sulfate : (Ca²⁺ + aluminate) in the colloidal suspension is lower than 0.30, wherein the colloidal suspension of the low-solubility salt is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups. A kit-of-parts for use with a shotcrete composition comprises (i) an alkali- free, aluminum-based shotcrete accelerator and (ii) a colloidal suspension of the low-solubility salt which is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups. I ncorporation of the colloidal suspension results in good slump retention as well as an improved compressive strength development up to 6 hours of the shotcrete composition.

Description

Construction Research & Technology GmbH PAT-0048-WO-PCT 1 Improved Shotcrete Compositions The present invention relates to a process comprising providing a cementitious composition; admixing an alkali-free, aluminum-based shotcrete accelerator to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden. Shotcrete (or sprayed concrete) is a mortar or concrete product, which is conveyed from delivery equipment through, e.g., a hose, and projected pneumatically at high velocity onto a surface. It has been used to protect exposed rocks from degradation due to weathering and dedication, in addition to providing support to loosened rock blocks in broken or overstressed ground. Commonly, admixtures are introduced to the cement/aggregate mix to improve its physical properties. In mining applications, there is a desire to reduce the time spent preparing excavations, shafts or tunnels to increase the productivity in such a structure without jeopardizing the workers' safety. In open excavations, when a lift is removed and as the newly exposed ground has limited stand up time, shotcrete is sprayed on first for stabilization and then rock bolts or some other means of support are installed for permanent support. In tunneling and mining, the exposed face is often sprayed with shotcrete until the next round is prepared for blasting. In addition, the tunnel surface is often sprayed with shotcrete until rock bolts or steel rings or concrete segmental linings can be installed. Conventional shotcrete can set in only a few minutes, but it is relatively slow to harden, taking several days to attain most of its strength. This means there is a significant delay after the shotcrete has been sprayed whilst it hardens until it is safe to resume mining activities in the vicinity of the shotcrete. This delay depends on what is considered to be an acceptable strength the concrete needs to attain. This time delay slows down mining operations and limits the applications in which shotcrete may be used. The time delay could be minimized by using a shotcrete composition, which hardens quickly and develops high early strengths. Especially under difficult working conditions like unstable ground, where fast rates of advance are required, or if thick layers have to be sprayed overhead, high early strength of shotcrete is crucial. Another problem in making shotcrete is the trade-off between setting time and early strength development, and the shotcrete's pumpability and sprayability. Improving shotcrete pumpability and sprayability will minimize power consumption and blockages risk. Construction Research & Technology GmbH PAT-0048-WO-PCT 2 Hence, shotcrete is under permanent improvement, not only in the concrete mix design, but also in the use of admixtures. The use of plasticizers as admixtures can lead to water reduction and/or slump retention. WO 2014/013077 discloses an additive for hydraulically setting compositions, comprising an aqueous, colloidally disperse preparation of at least one salt of a polyvalent metal cation and of at least one polymeric dispersant which comprises anionic and/or anionogenic groups and polyether side chains. The additive is suitable particularly as a slump retainer. WO 2015/028402 concerns a process for the preparation of a calcium silicate hydrate and ettringite containing hardening accelerator composition by reacting a water-soluble calcium compound, a silicate compound, an aluminum compound and a sulfate compound. The reaction of the four compounds is carried out in the presence of an aqueous solution which contains a comb polymer suitable as a plasticizer for hydraulic binders. The hardening accelerator composition is useful in sprayable binder compositions. There is a need for shotcrete compositions with good slump retention as well as an improved compressive strength development up to 6 hours. The above problems are solved by a process comprising providing a cementitious composition; admixing an alkali-free, aluminum-based shotcrete accelerator to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden, wherein the cementitious composition comprises a colloidal suspension of a low- solubility salt of at least one polyvalent metal cation selected from Fe³⁺, Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Al³⁺ and mixtures thereof, and at least one anion which is able to form a low-solubility salt with the polyvalent metal cation, wherein the anion is selected from carbonate, oxalate phosphate, polyphosphate, phosphite, borate, aluminate, sulfate, fluoride and mixtures thereof, wherein the colloidal suspension of the low-solubility salt is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups. Construction Research & Technology GmbH PAT-0048-WO-PCT 3 In an aspect, where the cation comprises Ca²⁺ and the anion comprises aluminate, the molar ratio of sulfate : (Ca²⁺ + aluminate) in the colloidal suspension is lower than 0.30, preferably lower than 0.25, more preferably lower than 0.10. Colloidal Suspension It has now been found that incorporation of a colloidal suspension of a low-solubility salt largely improves early strength development of the shotcrete. Although the mechanism is not fully elucidated it is believed that the colloidal suspension of the low-solubility salt promotes calcium silicate hydrates (C-S-H) formation in addition to formation of hydration products like ettringite. To be effective, the colloidal suspension of the low-solubility salt is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups. It is also contemplated that the colloidal suspension gradually releases polymeric dispersant which has been adsorbed to the minute particles of the low-solubility salt. The released polymeric dispersant has the ability to act as a concrete superplasticizer. The gradual release of polymeric dispersant serves to maintain pumpability and sprayability while avoiding high initial superplasticizer concentrations that can delay the setting of the cementitious composition. The experiments recounted in the examples below indicate that the effectiveness of the colloidal suspension is largely independent of the chemical nature of the low-solubility salt. The divalent or trivalent cations, such as calcium ions, contained in the low- solubility salt seem to function as a bridging ion between the colloidal low-solubility salt and negatively charged polymeric dispersant. The stabilized colloidal suspension of the low-solubility salt is obtained by precipitation of the low-solubility salt in the presence of the at least one polymeric dispersant, or by peptization of a low-solubility salt in a nascent state with the at least one polymeric dispersant. The nascent state in regard of this invention is to be understood as a freshly precipitated state or a freshly precipitated state aged no longer than 72 hours, preferably no longer than 24 hours. Peptization is understood to be a process of converting precipitate into a colloidal suspension by treating it with a polymeric dispersant acting as a peptizing agent. Where the cation comprises Ca²⁺ and the anion comprises aluminate, ettringite (Ca₆Al₂[(OH)₁₂(SO₄)₃]) may form in the presence of sulfates. Ettringite is a less preferred Construction Research & Technology GmbH PAT-0048-WO-PCT 4 low-solubility salt because it tends to form needle-like crystals rather than colloidal suspensions. Also, the hydrate phases formed from ettringite can bind and permanently fix the polymeric dispersant, which then is no longer gradually released. Ettringite formation can be inhibited or minimized by controlling the amount of sulfate. Hence, where the cation comprises Ca²⁺ and the anion comprises aluminate, the molar ratio of sulfate : (Ca²⁺ + aluminate) in the colloidal suspension is generally lower than 0.30, preferably lower than 0.25, more preferably lower than 0.10. In still more preferred embodiments, the colloidal suspension is essentially free of sulfate. Preferably, the colloidal suspension is essentially free of silicate. Precipitates of multivalent cations and silicate can likewise bind and permanently fix the polymeric dispersant, which then is no longer gradually released. In a preferred embodiment, the amount(s) of (all) polyvalent metal cation(s) are selected to satisfy the following formula (1): Additionally or alternatively, the amount(s) of (all) anion(s) are selected to satisfy the following formula (2): 0.01 (2). In formulae (1) and (2), φ is the charge density of the polymeric dispersant in eq/g of solid content, m_D is the amount of polymeric dispersant in g of solid content, z_K,i is the valency of the polyvalent metal cation, n_K,i is the molar amount of the polyvalent metal cation, z_A,l is the valency of the anion, n_A,l is the molar amount of the anion, the indices i, and l are independent of one another and are an integer greater than 0, i is the number of different kinds of polyvalent metal cations and l is the number of different kinds of anions which are able to form a low-solubility salt with the metal cation. In preferred embodiments, the amount(s) of (all) polyvalent metal cation(s) are selected to satisfy the following formula (1): and the amount(s) of (all) anion(s) are selected to satisfy the following formula (2): Construction Research & Technology GmbH PAT-0048-WO-PCT 5 0.01 (2). The numerator of the mathematical term in formula (1) is the valency of the polyvalent metal cation times the molar amount of the polyvalent metal cation, totalled over all polyvalent metal cations. Since the product of molar amount and valency is known as equivalents, the numerator has the unit equivalent (or milliequivalent, if the molar amounts are also provided in mmol). The denominator is the charge density of the polymeric dispersant in eq/g times the amount of polymeric dispersant in g. Hence, the denominator has the unit eq. Thus, the mathematical term in formula (1) is dimensionless. For analogous reasons, the mathematical term in formula (2) is dimensionless. Anionic groups are the deprotonated acid groups present in the polymeric dispersant. Anionogenic groups are the acid groups present in the polymeric dispersant. Groups which are both anionic and anionogenic, such as partially deprotonated polybasic acid residues, are asigned exclusively to the anionic groups when forming the sum of the molar amounts of the anionic and anionogenic groups present in the polymeric dispersant. The term “different kinds of polyvalent metal cations” refers to polyvalent metal cations of different elements. Furthermore, the term “different kinds of polyvalent metal cations” also refers to metal cations of the same element with different charge numbers. In one embodiment, the stabilized colloidal suspension of the low solubility salt the amount(s) of (all) polyvalent metal cation(s) and the amount(s) of (all) anion(s) are selected to satisfy the following formula (3): . The mathematical term in formula (3) is dimensionless. The ratio according to formula (1) is preferably in the range from 0.1 to 15, more preferably 0.15 to 10, most preferably 0.2 to 7, such as 0.2 to 4. The ratio according to formula (2) is preferably in the range from 0.01 to 1, more preferably 0.02 to 0.5, even more preferably 0.02 to 0.4, most perferably 0.02 to 0.3. The ratio according to formula (3) is preferably in the range from 0.25 to 70, more preferably 5 to 50, most preferably 7 to 50, such as 8 to 50. Construction Research & Technology GmbH PAT-0048-WO-PCT 6 Each range for formula (1) may be combined with each range for formula (2) and formula (3). Preferably, the ranges converge simultaneously. It is understood that certain polyvalent metal cations are existent under certain pH regimes only. For example, aluminum is amphoteric. Depending on the pH, it can either be present as Al³⁺ or Al(OH)₄-. Hence, if polyvalent metal cation is set to be Al³⁺, precipitation suitably proceeds under acidic conditions. Preferably, the at least one polyvalent metal cation is selected from Fe³⁺, Fe²⁺, Zn²⁺, Mg²⁺, Ca²⁺, Al³⁺ and mixtures thereof and preferably from Fe³⁺, Fe²⁺, Ca²⁺, Mg²⁺ and mixtures thereof. Preferably, the polyvalent metal cation is Ca²⁺. The counter-anion of the polyvalent metal cation salt (not the anion which is able to form a low-solubility salt with the polyvalent metal cation) is preferably selected such that the salts are readily water-soluble, the solubility under standard conditions of 20°C and atmospheric pressure being preferably greater than 10 g/l, more preferably greater than 100 g/l and very particularly greater than 200 g/l. The numerical value of the solubility here relates to the solution equilibrium (MX = Mn⁺ + Xn-, where Mn⁺: metal cation of the invention; Xn-: anion) of the pure substance of the salt in deionised water at 20°C under atmospheric pressure, and takes no account of the effects of protonation equilibriums (pH) and complexation equilibriums. The anions are preferably sulfate (in the case of calcium cation and aluminate as anion, sulfate should be avoided or minimized), or a singly charged counter-anion, preferably a nitrate, acetate, formate, hydrogen sulfate, halide, pseudohalide, methane sulfonate and/or amido sulfonate. The pseudohalides include cyanide, azide, cyanate, thiocyanate and fulminate. Double salts as well can be used as metal salt. Double salts are salts which have two or more different cations. An example is alum (KAl(SO₄)₂·12H₂O) which is suitable as an aluminum salt. Alum is rich in sulfate, therefore in the case of a combination with calcium cations the use of at least a second, preferably sulfate free, or poor in sulfate, aluminum source becomes necessary in order to minimize the sulfate content. The metal cation salts with the aforementioned counter- anions are readily water-soluble and hence especially suitable, since relatively high concentrations of the aqueous metal salt solutions (as reactant) can be established. In a further embodiment, the at least one anion which is able to form a low-solubility salt with the polyvalent metal cation is selected from carbonate, oxalate, phosphate, polyphosphate, phosphite, borate, aluminate, and sulfate, preferably phosphate, polyphosphate aluminate, and mixtures thereof and in particular from aluminate and mixtures thereof with at least one of phosphate, or polyphosphate. Construction Research & Technology GmbH PAT-0048-WO-PCT 7 The expression “low-solubility salt” means a salt whose solubility in water under standard conditions of 20 °C and atmospheric pressure is less than 5 g/L, preferably less than 1 g/L. The stated anions also include the polymeric borate and oxalate anions, and also the polyphosphates. The term “polymeric anions” refers to anions which as well as oxygen atoms comprise at least two atoms from the group consisting of boron, carbon, silicon and phosphorus. With particular preference they are oligomers having a number of atoms of between 2 and 20, more particularly preferably 2 to 14 atoms, most preferably 2 to 5 atoms. The number of atoms in the case of the polyphosphates it is more preferably in the range from 2 to 5 phosphorus atoms. The counter-cation of the anion salt which is able to form a low-solubility salt with the polyvalent metal cation is preferably a singly charged cation or a proton, preferably an alkali metal cation and/or ammonium ion. The ammonium ion may also comprise an organic ammonium ion, examples being alkyl ammonium ions having one to four alkyl radicals. The organic radical may also be of aromatic type or comprise aromatic radicals. The ammonium ion may also be an alkanol ammonium ion. In the polymeric dispersant, anionic groups are the deprotonated acid groups present in the polymeric dispersant. Anionogenic groups are the acid groups present in the polymeric dispersant. Groups which are both anionic and anionogenic, such as partially deprotonated polybasic acid residues, are assigned exclusively to the anionic groups when forming the sum of the molar amounts of the anionic and anionogenic groups present in the polymeric dispersant. The anionic and anionogenic groups are preferably carboxyl, carboxylate or phosphate groups, hydrogenphosphate or dihydrogenphosphate groups. In general, binary salts are preferred over ternary or higher order salts as the low- solubility salt. A binary salt is meant to be a salt of a single species cation and a single species anion. Preferred combinations of polyvalent metal cation and anion which is able to form a low- solubility salt with the polyvalent metal cation are the following: Construction Research & Technology GmbH PAT-0048-WO-PCT 8 Still particularly preferred are Al³⁺ phosphate, Al³⁺ fluoride, Ca²⁺ phosphate, Ca²⁺ aluminate, Ca²⁺ fluoride and Fe²⁺/Fe³⁺ phosphate. In one embodiment, the polymeric dispersant is a polymer which comprises structural units of the general formulae (Ia), (Ib), (Ic) and/or (Id): wherein R¹ is H, C₁-C₄ alkyl, CH₂COOH or CH₂CO-X-R^3A, preferably H or methyl; X is NH-(C_n1H_2n1) or O-(C_n1H_2n1) with n1 = 1, 2, 3 or 4, the nitrogen atom or the oxygen atom being bonded to the CO group; R² is OM, PO₃M₂, or O-PO₃M₂; or X is a chemical bond and R² is OM; R^3A is PO₃M₂, or O-PO₃M₂; (Ib) wherein R³ is H or C₁-C₄ alkyl, preferably H or methyl; Construction Research & Technology GmbH PAT-0048-WO-PCT 9 n is 0, 1, 2, 3 or 4; R⁴ is PO₃M₂, or O-PO₃M₂; wherein R⁵ is H or C₁-C₄ alkyl, preferably H; Z is O or NR⁷; R⁷ is H, (C_n1H_2n1)-OH, (C_n1H_2n1)-PO₃M₂, (C_n1H_2n1)-OPO₃M₂, (C₆H₄)-PO₃M₂, or (C₆H₄)-OPO₃M₂, and n1 is 1, 2, 3 or 4; wherein R⁶ is H or C₁-C₄ alkyl, preferably H; Q is NR⁷ or O; R⁷ is H, (C_n1H_2n1)-OH, (C_n1H_2n1)-PO₃M₂, (C_n1H_2n1)-OPO₃M₂, (C₆H₄)-PO₃M₂, or (C₆H₄)-OPO₃M₂, n1 is 1, 2, 3 or 4; where each M independently is H or a cation equivalent; A preferred embodiment of the polymeric dispersant comprises as anionic or anionogenic group at least one structural unit of the formula (Ia) in which R¹ is H or CH₃, X is a chemical bond and R² is OM; and/or at least one structural unit of the formula (Ib) in which R³ is H or CH₃; and/or at least one structural unit of the formula (Ic) in which R⁵ is H or CH₃ and Z is O; and/or at least one structural unit of the formula (Id) in which R⁶ is H and Q is O. Construction Research & Technology GmbH PAT-0048-WO-PCT 10 Another preferred embodiment of the polymeric dispersant comprises as anionic or anionogenic group at least one structural unit of the formula (Ia) in which R¹ is H or CH₃ and XR² is OM or X is O(C_nH_2n) with n = 1, 2, 3 or 4, more particularly 2, and R² is O-PO₃M₂. With particular preference, the structural unit of formula Ia is a methacrylic acid or acrylic acid unit, i.e. R¹ is H or methyl, X is a chemical bond and R² is OM and M is H or a cation equivalent; the structural unit of formula Ic is a maleic anhydride unit, i.e. R⁵ is H and Z is O; and the structural unit of formula Id is a maleic acid or maleic monoester unit, i.e. R⁶ is H, Q is O and R⁷ is H. A more preferred polymeric dispersant comprises structural units of the general formulae (Ia) and/or (Id). Where the monomers (I) are phosphoric esters or phosphonic esters, they may also include the corresponding diesters and triesters and also the monoester of diphosphoric acid. These esters come about in general during the esterification of organic alcohols with phosphoric acid, polyphosphoric acid, phosphorus oxides, phosphorus halides or phosphorus oxyhalides, and/or the corresponding phosphonic acid compounds, alongside the monoester, in different proportions, as for example 5-30 mol% of diester and 1-15 mol% of triester and also 2-20 mol% of the monoester of diphosphoric acid. The general formulae (Ia), (Ib), (Ic) and (Id) may be identical or different not only within individual polymer molecules but also between different polymer molecules. The polymeric dispersant optionally comprises structural units of the general formulae (IIa), (IIb), (IIc) and/or (IId): wherein R¹⁰, R¹¹ and R¹² independently of one another are H or C₁-C₄ alkyl, preferably H or methyl; Z² is O or S; Construction Research & Technology GmbH PAT-0048-WO-PCT 11 E is C₂-C₆ alkylene, cyclohexylene, CH₂-C₆H₁₀, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene; G is O, NH or CO-NH; or E and G together are a chemical bond; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; n2 is 0, 1, 2, 3, 4 or 5; a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; R¹³ is H, an unbranched or branched C₁-C₄ alkyl group, CO-NH₂ or COCH₃; wherein R¹⁶, R¹⁷ and R¹⁸ independently of one another are H alkyl, preferably H; E² is C₂-C₆ alkylene, cyclohexylene, CH₂-C₆H₁₀, 1,2-phenylene, 1,3-phenylene, or 1,4-phenylene, or is a chemical bond; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; n2 is 0, 1, 2, 3, 4 or 5; L is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; 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; R¹⁹ is H or C₁-C₄ alkyl; and R²⁰ is H or C₁-C₄ alkyl; Construction Research & Technology GmbH PAT-0048-WO-PCT 12 wherein R²¹, R²² and R²³ independently are H or C₁-C₄ alkyl, preferably H; W is O, NR²⁵, or is N; V is 1 if W = O or NR²⁵, and is 2 if W = N; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; R²⁴ is H or C₁-C₄ alkyl; R²⁵ is H or C₁-C₄ alkyl; wherein R⁶ is H or C₁-C₄ alkyl, preferably H; Q is NR¹⁰, N or O; V is 1 if Q = O or NR¹⁰ and is 2 if Q = N; R¹⁰ is H or C₁-C₄ alkyl; R²⁴ is H or C₁-C₄ alkyl; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; and a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; where each M independently is H or a cation equivalent. With particular preference, the structural unit of formula (IIa) is an alkoxylated isoprenyl unit, alkoxylated hydroxybutyl vinyl ether unit, alkoxylated (meth)allyl alcohol unit or a vinylated methylpolyalkylene glycol unit, in each case preferably with an arithmetic average of 4 to 340 oxyalkylene groups. A polymeric dispersant with structural unit (IIa) is preferred. More preferred is a polymeric dispersant with structural unit (IIa), wherein R¹⁰ and R¹² are H, R¹¹ is H or methyl, n2 is 0, Construction Research & Technology GmbH PAT-0048-WO-PCT 13 1 or 2, E is C₂-C₆ alkylene, G is O, or E and G together are a chemical bond, A is CH₂-CH₂ and R¹³ is H. The general formulae (IIa), (IIb), (IIc) and (IId) may be identical or different not only within individual polymer molecules but also between different polymer molecules. All structural units comprising group A may be identical or different both within individual polyether side chains and between different polyether side chains. Besides the structural units of the formulae (I) and (II), the polymeric dispersant may also comprise further structural units, derived from radically polymerisable monomers, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, (meth)acrylamide, (C₁-C₄) alkyl (meth)acrylates, styrene, styrenesulphonic acid, 2-acrylamido-2- methylpropanesulphonic acid, (meth)allylsulphonic acid, vinylsulphonic acid, vinyl acetate, acrolein, N-vinylformamide, vinylpyrrolidone, (meth)allyl alcohol, isoprenol, 1-butyl vinyl ether, isobutyl vinyl ether, aminopropyl vinyl ether, ethylene glycol monovinyl ether, 4- hydroxybutyl monovinyl ether, (meth)acrolein, crotonaldehyde, dibutyl maleate, dimethyl maleate, diethyl maleate, dipropyl maleate, etc. The polymeric dispersants comprising the structural units (I) and (II) are prepared in a conventional way, by means of radical polymerisation, for example. This is described for example in EP0894811, EP1851256, EP2463314, EP0753488. The polymeric dispersant is a polycondensation product, which comprises the structural units (IV) and (V) and, optionally, the structural unit (III): wherein 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; n3 is 1 or 2; 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 or O; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene, and in particular C₂ alkylene; a2 is an integer from 1 to 300; Construction Research & Technology GmbH PAT-0048-WO-PCT 14 R²⁶ is H, C₁-C₁₀ alkyl, C₅-C₈ cycloalkyl, aryl, or heteroaryl having 5 to 10 ring atoms, of which 1 or 2 atoms are heteroatoms selected from N, O and S; where the structural unit (IV) is selected from the structural units (IVa) and (IVb) wherein 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; E³ is N, NH or O, with the proviso that m is 2 if E³ is N and m is 1 if E³ is NH or O; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene, and in particular C₂ alkylene; b is an integer from 0 to 300, preferably 1; and M independently is H or a cation equivalent; wherein V² is phenyl or naphthyl and is optionally substituted by 1 or two radicals selected from R⁸, OH, OR⁸, (CO)R⁸, COOM, COOR⁸, and NO₂; R^7A is COOM, OCH₂COOM, or OPO₃M₂; M is H or a cation equivalent; and R⁸ is C₁-C₄ alkyl, phenyl, naphthyl, phenyl-C₁-C₄ alkyl or C₁-C₄ alkylphenyl. The structural units T and D in the general formulae (III) and (IV) in the polycondensation product are preferably derived from phenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4- hydroxyphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, naphthyl, 2- hydroxynaphthyl, 4-hydroxynaphthyl, 2-methoxynaphthyl, 4-methoxynaphthyl, phenoxyacetic acid, salicylic acid, preferably from phenyl, where T and D may be selected independently of one another and may also each be derived from a mixture of the stated radicals. The groups B and E independently of one another are preferably O. All structural units A may be identical or different not only within individual polyether side chains but Construction Research & Technology GmbH PAT-0048-WO-PCT 15 also between different polyether side chains. In one particularly preferred embodiment, A is C₂H₄. In the general formula (III), a is preferably an integer from 3 to 200 and more particularly 5 to 150, and in the general formula (IV) b is preferably an integer from 1 to 300, more particularly 1 to 50 and more preferably 1 to 10. Furthermore, the radicals of the general formulae (III) or (IV) may independently of one another in each case possess the same chain length, in which case a and b are each represented by a number. In general it will be useful for mixtures with different chain lengths to be present, so that the radicals of the structural units in the polycondensation product have different numerical values for a and, independently, for b. The polycondensation product of the invention frequently has a weight-average molecular weight (determined by SEC as described in the experimental part) of 5000 g/mol to 200000 g/mol, preferably 10000 to 100000 g/mol und more preferably 15000 to 55000 g/mol. The molar ratio of the structural units (III):(IV) is typically 4:1 to 1:15 and preferably 2:1 to 1:10. It is advantageous to have a relatively high fraction of structural units (IV) in the polycondensation product, since a relatively high negative charge of the polymers has a good influence on the stability of the aqueous colloidally disperse preparation. The molar ratio of the structural units (IVa):(IVb), when both are present, is typically 1:10 to 10:1 and preferably 1:3 to 3:1. The polycondensation product comprises a further structural unit (V), which is represented by the formula below: wherein R⁵ is H, CH₃, COOH or substituted or unsubstituted phenyl or naphthyl; R⁶ is H, CH₃, COOH or substituted or unsubstituted phenyl or naphthyl. Preferably R₅ and R₆ are H or one of the radicals R₅ and R₆ is H and the other is CH₃. R⁵ and R⁶ in structural unit (V) are typically identical or different and are H, COOH and/or methyl. Very particular preference is given to H. Construction Research & Technology GmbH PAT-0048-WO-PCT 16 Preferably, the weight ratio of (III):(IV) is in the range of 2:98 to 40:60, preferably 5:95 to 30:70, more preferably 10:90 to 20:80. In general, the molar ratio of the structural units [(III)+(IV)]:(V) in the polycondensate is 1.0:0.7 to 1.0:1.3, preferably 1.0:0.8 to 1.0:1.2, more preferably 1.0:0.9 to 1.0:1.1. The monomer with a keto group is preferably an aldehyde or ketone. Examples of monomers of the formula (V) are formaldehyde, acetaldehyde, acetone, glyoxylic acid and/or benzaldehyde. Formaldehyde is preferred. The polycondensates are typically prepared by a process which comprises reacting with one another the compounds forming the basis for the structural units (III), (IV) and (V). The preparation of the polycondensate is for example described in WO 2006/042709 and WO 2010/026155. The polymeric dispersant of the invention may also be present in the form of its salts, such as, for example, the sodium, potassium, organic ammonium, ammonium and/or calcium salt, preferably as the sodium and/or calcium salt. The average molecular weight M_w of the polymeric dispersant, as determined by Size Exclusion Chromatography (SEC; details are given below) is preferably 500 to 200000 g/mol, more preferably 10000 to 80000 g/mol, and very preferably 15000 to 55000 g/mol. The average molecular weight M_w of the polyether side chain of the polymeric dispersant, as determined by Size Exclusion Chromatography (SEC; details are given below) is preferably 500 to 8000 g/mol, more preferably 1000 to 5000 g/mol. The charge density φ of the polymeric dispersant is preferably at least 0.5 meq/g of solid content, more preferably in the range of 0.5 to 16.0 meq/g of solid content, most preferably in the range of 0.7 to 14.0 meq/g of solid content, in particular in the range of 0.7 to 3.0 meq/g of solid content. The charge density can be determined by titration with a polycation as described for example in J. Plank and B. Sachsenhauser, Cem. Concr. Res. 2009, 39, 1- 5. Moreover, the skilled person is capable of determining this value in a simple calculation from the initial weighings of monomers for the synthesis of the polymeric dispersant. The colloidal suspension preferably contains 3% to 50% by weight solids, more preferably 15% to 45% solid. The solids here comprise the polymer and also the polyvalent metal cation salt, and also the anion salt whose anion forms a low-solubility salt with the polyvalent metal cation. The colloidal suspension is prepared generally by mixing the components, which are preferably in the form on an aqueous solution. Construction Research & Technology GmbH PAT-0048-WO-PCT 17 For the preparation of the stabilized colloidal suspension of the low-solubility salt, the polymeric dispersant is preferably first mixed with the polyvalent metal cation and then the anion which is capable of forming a low-solubility salt with the polyvalent metal cation is added. According to another embodiment, the polymeric dispersant and the anion which is capable of forming a low-solubility salt with the polyvalent metal cation are mixed first, and then the polyvalent metal cation is added. To adjust the pH it is then possible to add a base. Preferably, the pH is in the basic range, preferably in the range from 9 to 12, more preferably 9.5 to 11.5 and in particular 10.5 to 11.5. The components are mixed generally at a temperature in the range from 5 to 80°C, usefully 10 to 40°C, and more particularly at room temperature (about 20 to 30°C). The preparation of the colloidal suspension may take place continuously or batchwise. The mixing of the components is accomplished in general in a reactor with a mechanical stirring mechanism. The stirring speed of the stirring mechanism may be between 10 rpm and 2000 rpm. An alternative option is to mix the solutions using a rotor-stator mixer, which may have stirring speeds in the range from 1000 to 30 000 rpm. Furthermore, it is also possible to use different mixing geometries, such as a continuous process in which the solutions are mixed using a Y-mixer, for example. If desired, a further step in the method may follow, for the drying of the colloidal suspension. Drying may be accomplished by roll drying, spray drying, drying in a fluidised bed process, by bulk drying at elevated temperature, or by other customary drying methods. The preferred range of the drying temperature lies between 50 and 230°C. The preparation of the colloidal suspension is disclosed in detail in WO2014013077, WO2014131778, WO2015110393 and WO2016207429 which are incorporated herein by reference. Thus, the colloidal suspension may take the form of an aqueous product in the form of a solution, emulsion or dispersion or in solid form, for example as a powder, after a drying step. The water content of the colloidal suspension in solid form is in that case preferably less than 10% by weight, more preferably less than 5% by weight. It is also possible for some of the water, preferably up to 10% by weight, to be replaced by organic solvents. Advantageous are alcohols such as ethanol, (iso)propanol and 1-butanol, including its isomers. Acetone can be used as well. By the use of the organic solvents it is possible to influence the solubility and hence the crystallization behaviour of the salts of the invention. Construction Research & Technology GmbH PAT-0048-WO-PCT 18 Cementitious Composition The cementitious composition comprises a cementitious binder. The cementitious binder is suitably selected from Portland cement, calcium aluminate cement and/or sulfoaluminate cement. The mineralogical phases are indicated by their usual name followed by their cement notation. The primary compounds are represented in the cement notation by the oxide varieties: C for CaO, S for SiO₂, A for Al₂O₃, $ for SO₃, F for Fe₂O₃, H for H₂O; this notation is used throughout. The term "Portland cement" denotes any cement compound containing Portland clinker, especially CEM I, II, III, IV and V 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 which may either contain calcium sulfate (<7% by weight) or is essentially free of calcium sulfate (<1% by weight). The phases constituting Portland cement mainly are alite (C₃S), belite (C₂S), calcium aluminate (C₃A), calcium ferroaluminate (C₄AF) and other minor phases. The alite (C₃S) provides primarily strength properties. Calcium aluminate cement (also referred to as high aluminate cement) means a cement containing calcium aluminate phases. The term "aluminate phase" denotes any mineralogical phase resulting from the combination of aluminate (of chemical formula Al₂O₃, or "A" in cement notation), with other mineral species. The amount of alumina (in form of Al₂O₃) is ≥ 30 % by weight of the total mass of the aluminate-containing cement as determined by means of X-ray fluorescence (XRF). More precisely, said mineralogical phase of aluminate type comprises tricalcium aluminate (C₃A), monocalcium aluminate (CA), mayenite (C₁₂A₇), tetracalcium aluminoferrite (C₄AF), or a combination of several of these phases. Sulfoaluminate cement has a content of ye’elimite (of chemical formula 4CaO.3Al₂O₃.SO₃ or C₄A₃$ in cement notation) of greater than 15% by weight. In an embodiment, the cementitious binder comprises a mixture of Portland cement and aluminate cement, or a mixture of Portland cement and sulfoaluminate cement or a mixture of Portland cement, aluminate cement and sulfoaluminate cement. In an embodiment, where the cementitious binder contains an aluminate-containing cement, the cementitious composition may additionally contain at least one calcium sulfate source. The calcium sulfate source may be selected from calcium sulfate dihydrate, anhydrite, ^- and ^-hemihydrate, i.e. ^-bassanite and ^-bassanite, or mixtures thereof. Preferably the calcium sulfate source is ^-bassanite and/or ^-bassanite. In Construction Research & Technology GmbH PAT-0048-WO-PCT 19 general, the calcium sulfate source is comprised in an amount of about 1 to about 20 wt.- %, based on the weight of the aluminate-containing cement. In an embodiment, the construction chemical composition additionally contains at least one alkali metal sulfate like potassium sulfate or sodium sulfate, or aluminum sulfate. The cementitious composition can be for example concrete, mortar or grouts. The term "mortar" or "grout" denotes a cement paste which contains fine aggregates, i.e. aggregates whose diameter is between 150 µm and 4 mm (for example sand), and optionally very fine granulates. A grout is a mixture of sufficiently low viscosity for filling in voids or gaps. Mortar viscosity is high enough to support not only the mortar's own weight but also that of masonry placed above it. The term "concrete" denotes a cement paste which contains coarse aggregates, i.e. aggregates with a diameter of greater than 4 mm. The aggregate in this invention can be for example silica, quartz, sand, crushed marble, glass spheres, granite, basalt, limestone, sandstone, calcite, marble, serpentine, travertine, dolomite, feldspar, gneiss, alluvial sands, any other durable aggregate, and mixtures thereof. The aggregates are often also called fillers and in particular do not work as a binder. Supplementary Cementitious Materials The shotcrete compositions may also contain latent hydraulic binders and/or pozzolanic binders. Typically, these latent hydraulic binders and/or pozzolanic binders are included in the cementitious composition prior to admixture of the alkali-free, aluminum-based shotcrete accelerator. For the purposes of the present invention, a "latent hydraulic binder" is preferably a binder in which the molar ratio (CaO + MgO):SiO₂ is from 0.8 to 2.5 and particularly from 1.0 to 2.0. In general terms, the above-mentioned latent hydraulic binders can be selected from industrial and/or synthetic slag, in particular from blast furnace slag, electrothermal phosphorous slag, steel slag and mixtures thereof. The "pozzolanic binders" can generally 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, rice husk ash, natural pozzolans such as tuff, trass and volcanic ash, natural and synthetic zeolites and mixtures thereof. 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. Construction Research & Technology GmbH PAT-0048-WO-PCT 20 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 from 200 to 1000 m² kg^-1, preferably from 300 to 500 m² kg^-1. Finer milling gives higher reactivity. For the purposes of the present invention, the expression "blast furnace slag" is however 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% by weight of CaO, about 4 to 17% by weight of MgO, about 30 to 45% by weight of SiO₂ and about 5 to 15% by weight of Al₂O₃, typically about 40% by weight of CaO, about 10% by weight of MgO, about 35% by weight of SiO₂ and about 12% by weight of Al₂O₃. 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% by weight of CaO, about 0.5 to 3% by weight of MgO, about 38 to 43% by weight of SiO₂, about 2 to 5% by weight of Al₂O₃ and about 0.2 to 3% by weight of Fe₂O₃, and also fluoride and phosphate. Steel slag is a waste product of various steel production processes with greatly varying composition. 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 SiO₂ in the amorphous silica of the invention is advantageously at least 80% by weight, preferably at least 90% by weight. 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. Fumed silica is produced via reaction of chlorosilanes, for example silicon tetrachloride, in a hydrogen/oxygen flame. Fumed silica is an amorphous SiO₂ powder of particle diameter from 5 to 50 nm with specific surface area of from 50 to 600 m² g^-1. Microsilica is a by-product of silicon production or ferrosilicon production, and likewise consists mostly of amorphous SiO₂ powder. The particles have diameters of the order of magnitude of 0.1 µm. Specific surface area is of the order of magnitude of from 15 to 30 m² g^-1. Construction Research & Technology GmbH PAT-0048-WO-PCT 21 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% by weight of CaO, whereas class F fly ash (hard-coal fly ash) comprises less than 8% by weight, preferably less than 4% by weight, and typically about 2% by weight of CaO. 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 (Al₂Si₂O₇). Accordingly, pure metakaolin comprises about 54% by weight of SiO₂ and about 46% by weight of Al₂O₃. For the purposes of the present invention, aluminosilicates are the above-mentioned reactive compounds based on SiO₂ in conjunction with Al₂O₃, which harden in an aqueous alkali environment. It is of course not essential here that silicon and aluminum are present in oxidic form, as is the case by way of example in Al₂Si₂O₇. However, for the purposes of quantitative chemical analysis of aluminosilicates it is usual to state the proportions of silicon and aluminum in oxidic form (i.e. as "SiO₂" and "Al₂O₃"). The shotcrete composition may further comprise additives such as: - grinding aids, like amines, amino alcohols, glycols, glycol derivatives, glycerol, glycerol derivatives, molasses, corn syrup; - nucleating agents, like calcium silicate hydrate compounds in finely grained form; - strength enhancers, like alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal oxides, alkaline earth metal oxides, alkali metal nitrates, alkaline earth metal nitrates, alkali metal nitrites, alkaline earth metal nitrites, alkali metal thiocyanates, alkaline earth metal thiocyanates, alkali metal halides alkaline earth metal halides and alkaline earth metal formates; - set retarders like sucrose, glucose, polymeric sugars and phosphonic acids; - mechanical reinforcement, like synthetic polymeric fibers (for example polypropylene), natural fibers, steel fibers, or meshes of these materials; - stabilizers or thickeners like cellulose ethers and cellulose derivatives, starch, starch ethers and other starch derivatives, xanthan gums, welan gums, diutan gums, high molecular weight polyacrylamides and copolymers thereof comprising acrylic acid and/or ATBS; - polymer dispersions in liquid form or in solid form, such as powder form, like polyacrylates, styrene-butadiene copolymers and ethylene-vinyl acetate copolymers; and - mixtures thereof. Construction Research & Technology GmbH PAT-0048-WO-PCT 22 Typically, these additives are included in the cementitious composition prior to admixing the alkali-free, aluminum-based shotcrete accelerator. Shotcrete Accelerator An alkali-free, aluminum-based shotcrete accelerator is admixed to the cementitious composition to obtain the shotcrete composition. According to European regulations (PREN 934-5 "Admixtures for Sprayed Concrete - Definitions, Requirements, Conformity, Marking and Labelling"), an accelerator is classified as “alkali-free” when the concentration of sodium and potassium, expressed as equivalents of Na₂O, is lower than 1%. Lithium is also an alkali metal, however the scientific literature shows that it does not negatively affect the concrete and therefore it is not considered in the calculation of equivalents of Na₂O. “Alkali-free" accelerators may comprise alkaline earth metal compounds, such as calcium salts, magnesium salts, and mixtures thereof. Typically, the alkali-free, aluminum-based shotcrete accelerator is comprised in a shotcrete accelerator formulation for ease of handling. Beside the alkali-free, aluminum- based shotcrete accelerator, the shotcrete accelerator formulation contains additives to provide shelf stability and other desirable properties to the shotcrete accelerator formulation. The shotcrete accelerator formulation can be in liquid form or solid form, such as powder form. The alkali-free accelerators of the inventive compositions are based on aluminum compounds, e.g., aluminum salts such as sulfates, nitrates, fluorides and/or their hydrates; aluminum oxides; and aluminum hydroxides. The alkali-free accelerators may be selected from aluminum salts, aluminum complexes, aluminum oxides, aluminum hydroxides, and mixtures thereof. Preferably, the alkali-free accelerator is selected from aluminum salts, especially aluminum sulfates. The weight ratio of alkali-free, aluminum-based shotcrete accelerator (c) to cementitious binder (a) in the shotcrete composition is typically in the range of 1-12 wt.-%, preferable in the range of 4-8 wt.-% relative to the weight of the shotcrete composition. Formulations of alkali-free shotcrete accelerators may be stabilized by various chemicals. Examples of such stabilizers include organic acids such as carboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids, phosphoric acid, phosphorous acid, phosphonic acids, sulfamic acid; inorganic acids such as sulfuric acid, nitrous acid, phosphoric acid, phosphorous acid, hydrofluoric acid, hexafluorosilicic acid, and mixtures thereof; urea; polymeric stabilizers, such as polyacrylamides, polycarboxylates, polysulfonates, and copolymers and mixtures thereof; aluminosilicates such as attapulgite, sepiolite and bentonite; and colloidal silica. Furthermore, shotcrete Construction Research & Technology GmbH PAT-0048-WO-PCT 23 accelerators may additionally comprise calcium and magnesium compounds such as for example sulfates, as well as amines, for example alkanolamines such as diethanolamine, triethanolamine, diisopropanolamine and triisopropanolamine and mixtures thereof. Suitable alkali-free accelerators and their manufacture are described, e.g., in WO 2008/006410 A1, WO 2010/063777 A1, WO 98/18740 A1, WO 03/029163 A2 and EP 1167 317 A1. The alkali-free, aluminum-based shotcrete accelerator or shotcrete accelerator formulation can be admixed to the cementitious composition using a static mixing device, such as an extruder or a standard sprayed concrete nozzle, or a dynamic mixing device, such as a standard mechanical mixer like a concrete mixer. The shotcrete accelerator formulation may be admixed to the cementitious composition in the form of an aqueous solution, in the form of an aqueous suspension, in the form of a solid, or a mixture of these forms. There are two basic shotcreting technologies, for both of which the present process is applicable: the "dry" process, in which a mixture of cement, fine and/or coarse aggregates and a powder accelerator is pneumatically conveyed through a nozzle to a delivery hose where water is added through a water ring to the essentially dry materials; and the "wet" process, in which the cement, aggregates and water are mixed to a plastic consistency before being conveyed hydraulically to the nozzle where compressed air is added to pneumatically project the wet material onto the surface. However, further “mixed” shotcreting technologies exist. Preferably, the shotcrete composition is pneumatically projected onto the surface. The invention will be described in more detail by the subsequent examples and the appended drawings. Fig. 1 shows the development of penetration force over time of various mortar mixes after addition of shotcrete accelerator. Fig. 2 shows the development of penetration force over time of various mortar mixes containing prior art calcium silicate hydrate and ettringite containing hardening accelerator compositions. Examples All the mortar tests were carried out at conditions of 20-22°C, 50-65%R.H. Construction Research & Technology GmbH PAT-0048-WO-PCT 24 All dosage percentages of superplasticizers or polymer-stabilized colloidal solutions (PSCS) are based on cement weight and relate to the solution or suspension as such. The dosage percentages were selected such that the polymer dosage in the performance tests was maintained at 0.159 wt.-% to ensure comparability. Materials P1: Polycarboxylate ether with polyethylene glycol side chains; charge density: 0.7 meq/g P2: Polycarboxylate ether with polyethylene glycol side chains; charge density: 1.0 meq/g SP1: Polycarboxylate ether with polyethylene glycol side chains; charge density: 0.9 meq/g SP2: Polycarboxylate ether with polyethylene glycol side chains; charge density: 1.7 meq/g SP3: Polycarboxylate ether with polyethylene glycol side chains; charge density: 1.5 meq/g SP4: Polycarboxylate ether with polyethylene glycol side chains; charge density: 2.7 meq/g SP5: Polyacrylic acid; charge density: 13.9 meq/g PSCS1: Polymer Stabilized Colloidal Solution of Ca²⁺/aluminate, incorporating P1 (formula (1) = 2.3; formula (2) = 0.1; formula (3) = 23) PSCS2: Polymer Stabilized Colloidal Solution of Ca²⁺/aluminate, incorporating P1 (formula (1) = 2.3; formula (2) = 0.2; formula (3) = 11.5) PSCS3: Polymer Stabilized Colloidal Solution of Ca²⁺/aluminate, incorporating P2 (formula (1) = 0.8; formula (2) = 0.3; formula (3) = 2.7) PSCS4: Polymer Stabilized Colloidal Solution of Ca²⁺/aluminate, incorporating P2 (formula (1) = 1.0; formula (2) = 0.3; formula (3) = 3.3) PSCS5: Polymer Stabilized Colloidal Solution of Ca²⁺/aluminate, incorporating P1 (formula (1) = 6.9; formula (2) = 0.1; formula (3) = 69) Polymer Stabilized Colloidal Solutions (PSCS) were prepared as described in WO 2014/013077 and WO 2014/131778. Construction Research & Technology GmbH PAT-0048-WO-PCT 25 Example 1: Sprayed Concrete Tests To evaluate the effect of PSCS addition to sprayed concrete, two test series have been conducted. Concrete was prepared containing cement as described in table 1.1, retarder and a plasticizer. PSCS was added to the concrete and homogeneously mixed. Spraying was conducted with standard full-scale spraying equipment through an air pressurized nozzle and accelerator injector into wooden boxes. Several commercial accelerators in different dosages and composition have been tested. MRoc SA 170 and 178 are colloidal solutions with a clear to opaque appearance. They are rich in aluminum but contain less sulfate. MRoc SA 167 is a suspension type accelerator. It contains less aluminum than the colloidal accelerators, but more sulfate. For the shotcrete tests fresh concrete mixes were prepared using Soroto mixer (examples 1.1.-1.4) and UEZ® ZM 400 high performance compulsory mixer (examples 2.1.-2.6). Freshly batched concrete was filled into the MEYCO® Suprema pump and sprayed with AFAs using MEYCO® Oruga sprayed concrete equipment. 2 shotcrete specimens were sprayed into wooden molds of dimensions 60x60x10 cm width x length x depth for each specific mix concrete + AFA. Strength measurements of shotcrete specimens were done dependently on age and strength of the specimens by using 1) electronic shotcrete penetrometer Mecmesin® AFG 1000 and/or mechanical MEYCO® shotcrete penetrometer equipped with a standard needle of 3mm diameter (the needle is tipped with an angle of 60°) (10 measurements for each age were done to give an average value) up to 3-6h shotcrete age (or up to ca. 1 MPa strength); followed by stud driving method of strength measurement using a Hilti® gun DX 450 (L-125) with a green cartridge, studs with appropriate length and a Hilti® Tester 4 pull out strength measurement device up to 24h shotcrete age, and finally by core drilling and compressive strength measurement of the shotcrete cores using a standard Zwick press 1485. The shotcrete specimens were stored for 0-24h at 20°C/65% RH, for 1-7d at 20°C/95% RH, for 7-28d: 20°C/95% RH. Results are shown in table 1.2. A comparison of 1.1 with 1.2 reveals a clear improvement in strength increase by adding PSCS1 into the mix. Similarly, a comparison 1.3 with 1.4 reveals that addition of PSCS3 also improves early strength formation. Construction Research & Technology GmbH PAT-0048-WO-PCT 26 Comparison of 2.1 with 2.2 and 2.3 and accelerator MRoc SA 167 reveals that both PSCS´s improve early strength formation, but performance of PSCS1 is measurable better than PSCS3. Comparison of 2.4 with 2.5 and 2.6 and accelerator MRoc SA 178 reveals that only PSCS1 improves early strength sligthly. PSCS3 is at early times comparable to the reference mix. Only after 3 hours a better strength is obtained. The colloidal accelerator MRoc SA 178 provides a quicker strength build up than the suspension type accelerator MRoc SA 167 see reference samples 2.1 and 2.4. Probably, that the better performing colloidal accelerator MRoc SA 178 cannot be boosted so much more in comparison to the suspension accelerator MRoc SA 167.

oonnsstrturcutciotnio Rnes Reearsceha &rc Thec &hn Toelocghyn GomlobHgy GmbH PAT-0048-WO-PCT 2277 . x_i %^c _o ⁵ 4 ^{5 5 5 5 5 5} ._s o_d ^c _o ._t w 4^. 4 4 4 e ^b ₀ ^. ₀ ^. ₀ ^. _{0 R} % 0 0 0 0 ^e _n ^e _n ^{e e e e 1 1 1 1} _{n n n n} r_e d_r ^A _C ^{A A o} _n ^o _n ^o _n ^o _n ^o _n ^o _n H _{C C} ^A _C a_{t c} ^H _c ^H _c ^{H e o o} _{c R R R} ^o _R ^o _R M M M M c_/ ⁶ ₃ ⁶ ₃ ⁶ ₃ ⁶ 0 ₃ ⁵ 0 ₄ ⁵ 0 ₄ ^{5 5 5 5} w ^. ₀ ^. ₀ ^{. . . .} _{0 4} ^. _{0 4} ^. _{0 4} ^. _{0 4} ^. ₀ t_n e_{t ,} n ^e _{t o} c ^e _r 3 t ^c _n ^m _/ 0 5 0 0 0 0 0 0 0 0 0 5 ⁵ ₅ ⁵ ₅ ^{5 4 4 4 4 4 4 n} _e ^o _c ^g _{k 5 4 4 4 4 4 4} m e _c ⁿ _i R 5 R R R R R ._{2 5} ^. _{2 5} ^. _{2 5} ^. _{2 5} ^. ₅ ^{. 4} - ⁴ _{2 2} S ^S- ^{4 S}- ^{4 S 4 S 4 S A A A} - A - A - I I ^I I ^I I ^I I ^I I ^AI I a ^{MMMM d} a d a d a d _{E E E E} ^M _E ^M _{E o o} ^{C C C C C C R} _{o o r r r r r r} t n ^{a R R R} e _g ^{i a} T _g ^{i a} _g ^{i a} _g ^ef i _r ^ef ^ef ^ef ^ef ^ef o _{r d} ^o _{r d} ^o _{r r r d} ^o _d ^o _d ^o _d m e _{C T C T C T C} ^r _h ^r _h ^r _h ^r _h ^r _h ^r _{h C} ^C _P ^C _P ^C _P ^C _P ^o _R ^o _R ^o _R ^o _R ^o _R ^o _{R 1} ^. ₁ .^x 1^. 2^. 3^. 4^. 1^. 2^. 3^. 4^. 5^. 6 e^l _{E 1 1 1 1 2 2 2 2 2} ^. _{2 b} a _T oonnsstrturcutciotnio Rnes Reearsceha &rc Thec &hn Toelocghyn GomlobHgy GmbH PAT-0048-WO-PCT 2288 n _i m ⁰ ₈ ⁹ ₇ 1 ^{. 7} 1 ₄ ^{. 1} 2 ₈ ^. 9 0 ^. ₀ ⁶ ₈ ^{. 7} 0 ₄ ^{. 5} 2 ₉ ^{. 9} 0 ₉ ^{. 9} 0 ₉ ^{. 0} 0 ₉ ^. ₁ t _a ] a_P M [ ⁿ _i h_t m ⁴ ₉ ⁶ ₀ ¹ ₂ ⁷ ₆ ² ₄ ⁹ ₇ ⁷ ₈ ² ₆ ¹ ₈ ^{4 g} _{n 0} 6 ^. ₀ ^. ₂ ^. ₀ ^. ₀ ^. ₀ ^. ₀ ^. ₀ ^. ₀ ^. _{0 5} ^. ₀ e_r ^{t t} _{a S} n_i m 5 ⁸ ₆ ^. 1^{. 4} ₁ ^{. 3} ₂ ^{. 5} ₁ ^{. 3} ₂ ^{. 7} ₁ ^{. 2} ₂ ⁷ ₂ ³ ₂ 1^t _{0 1 0 0 0 0 0} ^. ₀ ^. ₀ ^. _{0 a} n _i m ^{9 8 9 6} ₄ ^. _{0 7} ^. ₀ ^{. 1} ₂ ^{. 8} ₀ ^{. 4} ₁ ^{. 3} ₁ ^{. 4} ₁ ^{. 5} ₂ ^{. 6} ₁ ^{. t} _{0 0 0 0 0 0 0 0 0 a 2} ^. ₁ .^x 1^. 2^. 3^. 4^. 1^. 2 3 4 5 6 e^l _{E 1 1 1 1 2} ^. ₂ ^. ₂ ^. ₂ ^. ₂ ^. _{2 b} a _T Construction Research & Technology GmbH PAT-0048-WO-PCT 29 Example 2: Mortar tests Mix is described in the table 2.1. Standard sand 0/2mm and cement were placed into a 5L plastic bucket and shortly manually premixed with a spatula until homogeneity. Then mixing water, in which plasticizer OR polymer stabilized colloidal solution (PSCS) were predissolved shortly prior to use, was added to the cement-sand mix upon vigorous mixing the mortar with a Vollrath mixer equipped with a dissolver disc spindle at a speed increasing from 0 to 1300 rpm during 30s, followed by further 30s mixing at constant speed of 1300 rpm. Afterwards a 30s mixing break followed, during which the rests of mortar were scratched from the walls and bottom of the bucket to ensure the mix homogeneity, followed by another 60s of mixing at 1300 rpm. Thereafter alkali free accelerator was immediately injected via a syringe, in which AFA was preweighed prior to mortar mixing, into the mortar during its further mixing at 1300 rpm, followed by additional 40s of mortar mixing at 1300 rpm. Afterwards the mortar was densified manually with standard frequency (20 shocks at a stiff even surface) to ensure even upper surface of a mortar specimen Then the strength measurements of the mortar were started using a shotcrete penetrometer of a company Mecmesin AFG 1000 N equipped with a sharpened needle with 1,6 mm diameter. For each mortar age (6, 9, 15, 30, 60, 180, 300 Min calculated starting from the time when AFA was injected into the mortar) 10 measurements of penetration resistance force were done one immediately after another (at possibly all areas of the mortar surface to have statistically relevant distribution) and average value of those 10 single values were recorded (if needed, the outlier values were removed afterwards). Between the measurements the mortar was kept in a bucket covered with plastic lid. All samples with PSCS´s show a slight to medium improvement of penetration force compared to reference mix.

Construction Research & Technology GmbH PAT-0048-WO-PCT 30 ._s o ^c D_o w 7 7 7 7 7 7 7 7 r_e ^{1 d} _r ^ht a _{i t} w e _{R e} ^l _d ⁿ _i e m e ^{4 7 3 8 4 4 2 n} _{0 .} 6 ³ _{. 3} ⁷ _{. 4} ⁸ _{. 4} ⁹ _{. . . 3} ⁵ ₆ ² ₇ ⁵ ₇ ⁵ ₈ c_/ ⁵ ₄ ⁵ ₄ ⁵ ₄ ⁵ ₄ ⁵ _i ^{n t} _{a 0 4} ⁵ 0 ₄ ^{5 5} w ^. ₀ ^. ₀ ^. ₀ ^{. . .} _{0 4} ^. _{0 4} ^. ₀ ^s _e m^c _e n i ₃ ^ht ^m _r ^{M t} _nm _i ^{o e} _t ^{/ w} _N ^a t ₁ ^f _o n _{g e} ⁿ _{i o} ^k _, ⁿ _e -₆ 9 ^{d c} _r m 5 3^. 2^. 8^. 6 ⁹ _. ⁶ _. ⁸ _. ¹ _. c_t ^e _t m_{1 n} ^o _{f 6 8 5} ^{2 n} _e ^e ₁ ⁴ ₁ ⁴ ₁ ⁶ _{1 r} ^{e c} _{c N} ^a _{s e} ¹ n _g ^{E c t} _a g _n m e _c ^o _{c 6} 3₈ ⁰ ₅ ^a _t ^{s 3} i 1 _s e_{r n i} ^o t ^{t n n} t e ⁿ t e ⁿ t e ⁿ t e ⁿ t e ⁿ t e ⁿ t e ⁿ _{a e} ^r _{i t} ^m 4^. ₂ 3^. ₂ 3^. ₂ 1^. 4^. 4^. 9^. 5^{. mm mm mm m m e} _n ⁶ _{2 2 4 3 3 e e e e e e e} ^{t C C C C} _e ^e _{P a} t n_e ^{o i o o C C C C} y _{e y} ⁱ _y ^{i o} _y ^{i o} _y ^{i o} _y ^{i o} _y ^{i o} _y ⁱ m _i ^h _{e i} ^h _{e i} ^h _{e i} ^h _{e e e e} e ^{a a a a} _i ^{h a} _i ^{h a} _i ^{h a} _i ^h 1^. _{C T T T T T T T} ^a _{T 2 2} ^. ₂ .^x 1^. 2^. 3^. 4^. 5^. 6^. 7 8 e^l . b ^x 1^. 2^. 3^. 4^. 5^. 6^. 7^. 8 _e ^l _{E 3 3 3 3 3 3} ^. ₃ ^. ₃ a _{E 3 3 3 3 3 3 3} ^. _{3 b T} ^a _T Construction Research & Technology GmbH PAT-0048-WO-PCT 31 Example 3 In this example, the effect of polymer-stabilized colloidal suspension of low-solubility salts obtained by peptization of freshly precipitated salts is investigated. Besides, a PSCS (sample 2) was tested. Sample 1 is a control without addition of colloidal suspension of low-solubility salt and was tested twice. The peptizited low solubility salts were obtained by preparing aqueous solutions of reagent salts, and then consecutive mixing of those solutions (i.e., calcium nitrate, sodium aluminate and sodium hydroxide). Polymer and defoamer were added immediately afterwards upon mixing to the suspension of the low solubility salt. Defoamer was added separately if no ready-to-use defoamed plasticizer was used, to avoid air entrainment. Remaining water was added to this mix and the mortar was mixed as described above. Water to dissolve the soluble ingredients was compensated in the total mixing water in mortar, keeping it at a constant water/cement value in the mortar mix. As SP3 is a ready-to-use superplasticizer product for concrete it contains a defoamer. In other cases, a defoamer was added separately. Aggregates and cement were weighed and placed into a 5L metal bowl of a Hobart mixer N 50 (planetary and shaft mixing action) and premixed in dry state at lowest speed 1 for 1 min, followed by addition of mixing water, in which plasticizer AND (if applicable) a suspension of low solubility salt OR polymer stabilised colloidal solution (PSCS) were predissolved shortly prior to use, as indicated in table 3.1. Afterwards the mortar was mixed for additional 30s, followed by a mixing break of 1 Min duration, during which the mortar was scratched from the bottom and walls of the bowl manually using a scraper to improve mortar homogenization. After a break the mortar was mixed at a Speed 2 for further 2 min. Alkali free accelerator (AFA) was injected via a syringe, in which AFA was preweighed prior to mortar mixing, into the mortar during its mixing at Speed 2, followed by additional 15s of mortar mixing at Speed 2. Afterwards the accelerated mortar was immediately placed into a plastic bucket with standard dimensions, densified with standard frequency at the concrete vibration table (15 shocks) to ensure even upper surface of a mortar specimen, and then the strength measurements of the mortar were started using a shotcrete penetrometer of a company Mecmesin AFG 1000 N equipped with a standard shotcrete penetrometer needle with 3mm diameter (the needle is tipped with an angle of 60°). For each mortar age (6, 9, 15, 30, 60, 180, 360 Min, calculated starting from the time when AFA was injected into the mortar) 9 measurements of penetration resistance force were done one immediately after another (at possibly all areas of the mortar Construction Research & Technology GmbH PAT-0048-WO-PCT 32 surface to have statistically relevant distribution) and average value of those 9 single values were recorded (if needed, the outlier values were removed afterwards). Between the measurements the mortar was kept in a bucket covered with plastic lid. The results are shown in table 3.2. Repetition of reference sample (sample 1) shows minor deviations which are considered to fall within measurement error. When comparing example 1 and 2, in which a PSCS is used, a relevant increase in penetration force is observed. Examples 2 to 6 display tests of one PSCS in original status, specifically prepared (example 2) and variations thereof: Same composition but not prepared as PSCS (example 3), not prepared as PSCS and richer in aluminum (example 4), not prepared as PSCS and richer in calcium (example 5) and not prepared as PSCS, but richer in aluminum and calcium (example 6). By these changes, ratio 1 and 2 change from 2.3 to 9.2 and from 0.1 to 0.3. Consecutively ratio 3 changes from 23 down to 7.7 or up to 92. It seems that this performance improvement is valid in a broad range. Interestingly examples 2 and 3 are basically equal in performance, although one time a PSCS precipitated in the presence of dispersant is used (example 2) and example 3 has same composition as example 2, but the constituents are mixed in reverse mode, first, low-solubility salt precipitated, then dispersant is added. Similar increases in penetration force by time can be observed in examples 3 and 5, where either more aluminum or more calcium and aluminum, in same ratio as in example 2 is added. Interestingly, an increased amount of calcium as used in example 4 does not deliver same performance as examples 3 and 5. But, in comparison to example 1, this "calcium-rich" mix shows higher penetration values from approx. 1 hour onwards.

Construction Research & Technology GmbH PAT-0048-WO-PCT 33 P ² 6 .₁ ² 1 9 6 5 ¹ _{9 0} ^{. 7 6} 0 0 0 ¹ 0 ₀ ^. _{1 0} ^. _{0 0} ^. ₀ 4 8 4 ¹ _P ² ₉ ^. ₁ ⁰ ₁ ^{. 6} 9 0 ₂ ^{. 6} 6 0 ₀ ^. 0 0 0 ¹ 0 ₀ ^. ₀ 0 3 ₀ 0 .₆ ⁷ _. ⁰ ₉ ^{. 5} 6 9_. ² ₉ 6 2 8 6 9 6 6 1 ^{1 6} 6 _{4 4 4} 0₁ ⁹ ₆ ^. ₀ ^{6 1} 3 _P ^. _{1 0} ^. _{0 2} ^. _{0 0} ^. 0 0 0 0 ₀ ^. ₀ 1 2 ^S _C ^{6 S} ₂ ^. ₃ 0 0 0 0 0 0 0 P 0 0 0 0 0 0 0 1 ₃ 2 P _S ³ _. 2₁ 0 0 0 0 0 0 0 ]^g _{[ R 5} ] .₂ ^g _[ ] 4 ₇ ^{g S}- ⁶ ₁ ] _{[ e A} ^g [ ^t _a ] A_/ ^I I ^S ] g _[ ] g ^% ₅ ^r _d ] g [ ^g _[ M] ] ^c _o [ ] ^{7 y} _h ^e _t 2 E ^g [ ^g [ ^R _r ^{%g %} _i ^{d - 0} _i ^{o C} _f ^e _{6 t} ⁹ ₁ [ ⁰ ₃ ^c _a ¹- ^a _{r 5} 2_l ^t _a ^{r r} m m ^] o ^{m m s} _{a g} . [ _l %. o _{0 l} o c_i ^{r e} _t ^d _y h- ^o _{n t} n ^{d 1 1} M _{r s} ⁵ _{. s o} ^a _r ⁷- ^y _{f e r} h _{1 o} ^{< s - ]}- ^e _{zi e} ^{t o} _e ^{h d} _y ^r _u m^. _e ^{> s} _{e r} o ^[ _r ^ci _{t a} n _{s i e} ^di _{x p} ^s _o ^{h e} _t a_f ^{S e} c₃ e ^R _t ^t _a ^t _{a t} a_r ^e _zi ^s _a m^t _a ^o _r ^h _P ^e _t a ^l _u ^r _e ^o t_e ^{l l} _p ⁿ _e ^g _e ^g _e ^e _l ^c _{i b} mm^r _g ^r _g *^{c e} _{c t} ^l _{P l} ^{u r} _ti ^d _y - ^s _{o f} ^{l S}-₎ ^m _a ^r _{e a} ._s ^A- ^N- ^H- ^h _{t u} S- ^II₍ ^o _f ^t _a ^a _T ^a _S ^e _C ^g _A ^g _{A /} w^c _A ^l _P ^o _D ^a _N ^a _C ^a _N ^r _o ^l _A ^e _F ^e _D w * Construction Research & Technology GmbH PAT-0048-WO-PCT 34 0₁ ^{1 2} ₉ ^{2 0} ₀ ⁶ ₂ ⁶ ₀ 0 0 0 ¹ _{0 0} 0 .₆ ⁷ _. ⁰ 6 _P ^. ₁ ^. ₀ ^. ₀ ^. ₀ ^. ₀ 6 ₉ ^. ₄ ⁵ ₄ ⁹ _. 1_{6 4} 0 ^. 1 ⁹ _{6 0} ⁶ ₃ 9 4 0 P _S ² 6 8^{. 2} 8 6 9 6 6 1 2 ₀ ^. _{0 2} ^. _{0 0} ^. 0 0 0 0 ₀ ^. ₀ 0 P ² 9 9^. 0 ⁶ 1 7 7 6 8 ¹ 0 ^{2 1} 1 ₀ ^. _{0 0} ^. 0 0 ₂ ^. _{0 0} ^. _{0 P} ² 9 .₁ ⁶ 1 ¹ 0 ₁ 6 7 ¹ ₉ 0 0 ^{. 7} 0 ₀ ^. ₀ ⁵ ₄ 0 ^{1 .} _{0 0} ^. _{0 7} ] g ⁶ ] _{[ 1} ^g [ _e / _A ] ] ^t _a ^r ] ] g⁾ _d ^I I ^S ] ] ^c _o ^g _[ ^g [ ^% _{5 d} y ^g [ _[ 2^e _u ^M _E ^g [ ^g [ ^R _r ^%] 9 ^g [ ^{% 7} i^d _h-₆ ^e _t a_r ⁰ _{5 i} ^{ot n}i_t ^C _f m m ^e _t ^{s ]} _{1 g} ._l %⁰ ₃._l ^c _a ¹ c - e ^d _y ² _{l a} o ^r _t ^{n r} _{o o} ^{m d 1 m} _a ^{[ 1} M _r ^o _{s 0} 5_. ^o _{s i} ^r _{t o} ^a _r ^h _{- n} ^{n 7 c} _r ] - ^y _{f e (} ^{h g} [ ^{< > -} _r ^]- ^e _{zi e} ^t _{e a} ^o _s ^{d h} _p ^d _y ^e _t ^r _u m e_{1 o} ^. ₃ e ^R _t ^{R s} _e ^s _e ^{o 5} _t ^[ _r ^ci _t ⁿ _{i e} ⁱ . ^t _a ^t _a ^a _r ^e _zi ^s _a ^t _x o ^s _o ^{h e a} _f ^S c l ^r _{e e} ^{l l} _p ⁿ _e ² _b mm₄ ^g _e ^{g l} m_a ^r _{r S} ^r _{e g} ^r _g * ^e _l ^c _i c _{t P /} ^e _c . _l ^u _ti ^d _y ^h _{P t} -_o ^a _{f u} ^{o l} _u ^S-₎ ^m t a ^r _e ] ^s _{a s} ^A- ^{t a N}- ^H- ^II ^{o a h} _t ^S _{- ( f a} ^a _T ^a _S ^e _C- _A ^g _A ^g _A w^c _A ^g _[ ^l _P ^o _{D N} ^a _{C N} ^r _o ^l _A ^e _F ^e _D w * Construction Research & Technology GmbH PAT-0048-WO-PCT 35 2_{1 0} ^. _{3 0} ^. ₅ ⁶ _. 8 ⁸ _. 4 4 6^. ₅ 6^. ₉ ⁷ _. 0 ^. 5 ₆ 6 ⁴ _. ⁸ _{. 1} ⁰ _{1 0} ^. _{4 5} ^. ₇ ⁷ ₂ ⁹ ₈ 3 4^. ₅ ⁴ _. 0 ² _. 1 1 ⁵ ₄ ⁰ ₂ 9 ₂ ^{. 4} _. ⁰ _{. 6} ^. ₅ 6_. ⁸ _. 4^. ₆ ³ ₁ ⁶ ₅ ² ₂ 2 5 ⁰ ₁ ⁵ _{5 8} 0₂ 2^. ₃ 8^. ₅ ⁸ _. 8 ₅ ^. ₀ ^{. 9} _{. 0} ^. ₂ 1₂ ⁴ _{5 5 8} ⁵ ₃ ⁶ ₁ 1 4^. ₃ 7^. ₅ ¹ _. 4 ⁴ _{. 0 6} ¹ _{. 3} ^. 2 ⁰ ₈ 7 ^. ₄ ^. ₈ ⁶ _{2 5} 4_{1 i} ^ns _{i e} ^ns _e m^c m e ^c _e M ^{a M f} _o] ^af e _{e o}] l_p ^c _r ^N _{[ e} c ^N _[ o ^r _e e^l _{p r} ^r _e m_{F e} ^t _e ^{o )} _F ^t d m_{e e} a _S ^c _nm a _{i t} ^{a a} _S ^c _nm i si ^{d e} _{u s} m ⁿi ^a _t ^a t ^si ^d m e_Rm ⁿ _{s o} ^e m n ³ ₂ ^h _t ^. _i ^ot _i ^c _{R ( n} ^{3 h} _{t i a} ^{w n} _i ⁿ _{i i} ⁿ ₂ ^. _i ^ot _a ^{w n} _i ⁿ _{i i} ⁿ _{3 e} ^{r l} _{t l} ^{e n} _{i b} ^e _n ^{d m}m 5 m ^m ₃ ⁿ _{i 0} ⁰ _e ^r _{t l} ^e mm ^{m 0 a} _T ^e _{e P} ^e _n ^6t _a ^1t _a ⁶ ₈ t _a ^{1 l t} _b ^e _n ^d _e ^m a ^{a 6} ₅ 1 ₀ 6 ₈ 1 T ^e _P ^e _n ^t _a ^t _a ^t _a ^t _a Construction Research & Technology GmbH PAT-0048-WO-PCT 36 Example 4 In this example, additional polymer-stabilized colloidal suspensions of low-solubility salts as indicated in Table 4 were prepared and tested alongside PSCS1. Polymer Stabilized Colloidal Solutions (PSCS) were prepared as described in WO 2014/013077 and WO 2014/131778. In particular, an aqueous solution of polymer was provided. Thereafter, an aqueous solution of the anionic component (H₃PO₄) was added. After 5 min, an aqueous solution of the cationic component (Fe(III) nitrate or Ca(II) nitrate) was added. Subsequently, the pH value was adjusted to 11 using aqueous sodium hydroxide (20%). PSCS6: Polymer Stabilized Colloidal Solution of Ca²⁺/phosphate, incorporating P1 (formula (1) = 2.3; formula (2) = 0.1; formula (3) = 23) PSCS7: Polymer Stabilized Colloidal Solution of Fe³⁺/phosphate, incorporating P1 (formula (1) = 2.3; formula (2) = 0.1; formula (3) = 23) PSCS8: Polymer Stabilized Colloidal Solution of Ca²⁺/phosphate, incorporating P1 (formula (1) = 1; formula (2) = 1; formula (3) = 1) PSCS9: Polymer Stabilized Colloidal Solution of Fe³⁺/phosphate, incorporating P1 (formula (1) = 1; formula (2) = 1; formula (3) = 1) Concrete mixing and tests were carried out as described in Example 3. The results of the penetration tests are shown in Fig. 1. All polymer-stabilized colloidal suspensions show a relevant increase in penetration force versus the control. Example 5 In this example, prior art calcium silicate hydrate and ettringite containing hardening accelerator compositions as indicated in Table 5 were prepared and tested alongside PSCS1. Susp-1, Susp-3 and Susp-9 were prepared as described in WO 2015/028402, except that Poly-1 was used also for the preparation of Susp-3 and Susp-9. The tests with Susp-1, Susp-3 and Susp-9 were performed in pairs of different dosages. The higher dosage reflects the dosages disclosed in WO 2015/028402, whereas the lower dosage is adjusted to the same polymer dosage as in the inventive examples. Concrete mixing and tests were carried out as described in Example 3. The results of the penetration tests are shown in Fig. 2. PSCS1 exhibits a higher penetration force than the prior art compositions. Construction Research & Technology GmbH PAT-0048-WO-PCT 37 _P ^u _S %₃ ^% ₃ 0 ^% ₃ ^% 3 ⁰ ₀ ⁶ _. ⁵ _{0 8} 3_{. 4 6} ⁵ _. ⁶ _{6 3} ⁰ ₀ ⁶ _. ⁵ _{8 6} - ^{. 1 1} ₄ ⁰ ₂ ⁹ _. ^{- . 1} ₄ ² _, ⁷ _. ⁹ _{. 6 4} 7 ^. 1 ₀ ^, ₆ ^{. S} _{3 C} ⁶ _{3 5 6} 1_{6 4} 7 ^. ₀ ¹ - ⁰ ₁ ⁶ ₃ S ₁ ^p _{s P} ^u _{S 0} ^% ₀ ^% _{5 2} ^{0 -} _{0 4} ^. ₆ ⁶ _. ⁵ ₀ 3_. ¹ ₆ 9 ₂ ⁰ ₀ ⁸ _. . ⁶ _. ^{5 4} ₈ 7 ₆ 9 ^{1 1} 6 _{4 4} 7 ^. 1 ₀ ^1, _{0 3} ^. _{. 8} ^{6 P} ₃ - _{5 6} 1 ¹ 6 _{4 4} ^. _{0 ,} 1 _{. . -} ⁰ ₁ ⁶ _{3 S} ⁷ ₁ ^p _s u _S %₃ % 3 1 ⁰ _{0 0} 6_. ^{5 5} _{. 6} ⁰ _{0 0} 6_{. 5} ^. ₆ -₄ ^. ₆ 1 ¹ 6 _{4 4} 7 ^{. 0,} ₁ ⁶ ₂ ^{. 9} _{. 1 1 0} ^S _{3 C} ⁶ ₃ - ₅ ^. ₆ 1 ¹ 6 ₄ ⁵ ₄ 7 ^. _{0 1} ⁶ ₂ ^{. 9} _. 6 ^S _{1 0} ^S _{C 3 3 P} ^S _P M_E ^M _i ^o e ^C _E ^{t l} _f ^r m ^] _g 7 ^{C 6} _e ^l _f ^r m ^] _{a g} 7 ^{r 6} _{t p o}]^g m ^[ _{r 1 p o}]^g m ^[ _{r 1} ⁿ _e m^{d a} _r [ ^{4 h <} ]- ^e _zi -_{r A} S m^{d a} _r [ ^{4 h <} ]- ^e _zi -_{r A} S m S _o ^{R s [ ci c} _{S o} ^{R s [ ci e} c R⁵ _{. e r t} ^o _{t o} ⁵ _{. e r t} ^o _t ^c _{o 4 t} ² ₄ ^t _a ^e _zi ^s _a ^{l a} _r ^R _{r 5} ^R _t ² ₄ ^t _a ^e _zi ^s _a ^{l a} _r ^R _r ^o t_e ^{n l} _{e S} ^g _{e b} ^* m-_A ^r _{g c} ^c _{i / t P} s_a ._s ^e _l e ^e _{t e} ⁿ _{e S} ^g _e ^* _c ^ci_{t P} ^e _l ^e _t ^r _e o _c ^s _a ^l _b m-_A ^r _{g /} ^s _a ._s ^{e o} _c ^s _a ^t _a ^a _T ^e _C ^/I _I ^g _A w ^l _{P D} ^c _A M ^a _T ^e _C ^/I _I ^g _A w ^l _{P D} ^c _A M w * ₅

Claims

Construction Research & Technology GmbH PAT-0048-WO-PCT 38 Claims 1. A process comprising providing a cementitious composition; admixing an alkali-free, aluminum-based shotcrete accelerator to the cementitious composition to obtain a shotcrete composition; and applying the shotcrete composition onto a surface to obtain a shotcrete structure and allowing the shotcrete structure to harden, wherein prior to admixing the shotcrete accelerator, a colloidal suspension of a low-solubility salt of at least one polyvalent metal cation selected from Fe³⁺, Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Al³⁺ and mixtures thereof, and at least one anion which is able to form a low-solubility salt with the polyvalent metal cation, wherein the anion is selected from carbonate, oxalate, phosphate, polyphosphate, phosphite, borate, aluminate, sulfate, fluoride and mixtures thereof, is added to the cementitious composition, with the proviso that where the cation comprises Ca²⁺ and the anion comprises aluminate, the molar ratio of sulfate : (Ca²⁺ + aluminate) in the colloidal suspension is lower than 0.30, preferably lower than 0.25, more preferably lower than 0.10, wherein the colloidal suspension of the low-solubility salt is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups. 2. The process according to claim 1, wherein the stabilized colloidal suspension of the low-solubility salt is obtained by precipitation of the low-solubility salt in the presence of the at least one polymeric dispersant, or by peptization of a low-solubility salt in a nascent state with the at least one polymeric dispersant. 3. The process according to claim 1 or 2, wherein in the stabilized colloidal suspension of the low-solubility salt the amount(s) of (all) polyvalent metal cation(s) are selected to satisfy the following formula (1): and the amount(s) of (all) anion(s) are selected to satisfy the following formula (2): 0.01 Construction Research & Technology GmbH PAT-0048-WO-PCT 39 wherein φ is the charge density of the polymeric dispersant in eq/g of solid content, m_D is the amount of polymeric dispersant in g of solid content, z_K,i is the valency of the polyvalent metal cation, n_K,i is the molar amount of the polyvalent metal cation, z_A,l is the valency of the anion, n_A,l is the molar amount of the anion, the indices i, and l are independent of one another and are an integer greater than 0, i is the number of different kinds of polyvalent metal cations and l is the number of different kinds of anions which are able to form a low-solubility salt with the metal cation. 4. The process according to claim 3, wherein in the stabilized colloidal suspension of the low solubility salt the amount(s) of (all) polyvalent metal cation(s) and the amount(s) of (all) anion(s) are selected to satisfy the following formula (3): 0.25 ^. 5. The process according to any one of the preceding claims, wherein the polymeric dispersant comprises polyether side chains. 6. The process according to any one of the preceding claims, wherein the polyvalent metal cation is selected from Fe³⁺, Fe²⁺, Zn²⁺, Mg²⁺, Al³⁺, Ca²⁺, and mixtures thereof and in particular from Fe³⁺, Fe²⁺, Ca²⁺, Mg²⁺ and mixtures thereof. 7. The process according to any one of the preceding claims, wherein the anion which is able to form a low-solubility salt with the polyvalent metal cation is selected from phosphate, polyphosphate, aluminate, and mixtures thereof. 8. The process according to any one of the preceding claims, wherein the charge density φ of the polymeric dispersant is at least 0.5 meq/g of solid content, preferably 0.5 to 16.0 meq/g of solid content, more preferably in the range of 0.7 to 14.0 meq/g of solid content, most preferably in the range of 0.7 to 3.0 meq/g of solid content. Construction Research & Technology GmbH PAT-0048-WO-PCT 40 9. The process according to any one of the preceding claims, wherein the polymeric dispersant comprises structural units of the general formulae (Ia), (Ib), (Ic) and/or (Id): wherein R¹ is H, C₁-C₄ alkyl, CH₂COOH or CH₂CO-X-R^3A, preferably H or methyl; X is NH-(C_n1H_2n1) or O-(C_n1H_2n1) with n1 = 1, 2, 3 or 4, the nitrogen atom or the oxygen atom being bonded to the CO group; R² is OM, PO₃M₂, or O-PO₃M₂; or X is a chemical bond and R² is OM; R^3A is PO₃M₂, or O-PO₃M₂; wherein R³ is H or C₁-C₄ alkyl, preferably H or methyl; n is 0, 1, 2, 3 or 4; R⁴ is PO₃M₂, or O-PO₃M₂; wherein R⁵ is H or C₁-C₄ alkyl, preferably H; Construction Research & Technology GmbH PAT-0048-WO-PCT 41 Z is O or NR⁷; R⁷ is H, (C_n1H_2n1)-OH, (C_n1H_2n1)-PO₃M₂, (C_n1H_2n1)-OPO₃M₂, (C₆H₄)-PO₃M₂, or (C₆H₄)-OPO₃M₂, and n1 is 1, 2, 3 or 4; wherein R⁶ is H or C₁-C₄ alkyl, preferably H; Q is NR⁷ or O; R⁷ is H, (C_n1H_2n1)-OH, (C_n1H_2n1)-PO₃M₂, (C_n1H_2n1)-OPO₃M₂, (C₆H₄)-PO₃M₂, or (C₆H₄)-OPO₃M₂, n1 is 1, 2, 3 or 4; where each M independently is H or a cation equivalent; and, optionally, structural units of the general formulae (IIa), (IIb), (IIc) and/or (IId): wherein R¹⁰, R¹¹ and R¹² independently of one another are H or C₁-C₄ alkyl, preferably H or methyl; Z² is O or S; E is C₂-C₆ alkylene, cyclohexylene, CH₂-C₆H₁₀, 1,2-phenylene, 1,3- phenylene or 1,4-phenylene; Construction Research & Technology GmbH PAT-0048-WO-PCT 42 G is O, NH or CO-NH; or E and G together are a chemical bond; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; n2 is 0, 1, 2, 3, 4 or 5; a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; R¹³ is H, an unbranched or branched C₁-C₄ alkyl group, CO-NH₂ or COCH₃; wherein R¹⁶, R¹⁷ and R¹⁸ independently of one another are alkyl, preferably H; E² is C₂-C₆ alkylene, cyclohexylene, CH₂-C₆H₁₀, 1,2-phenylene, 1,3- phenylene, or 1,4-phenylene, or is a chemical bond; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; n2 is 0, 1, 2, 3, 4 or 5; L is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; 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; R¹⁹ is H or C₁-C₄ alkyl; and R²⁰ is H or C₁-C₄ alkyl; Construction Research & Technology GmbH PAT-0048-WO-PCT 43 wherein R²¹, R²² and R²³ independently are H or C₁-C₄ alkyl, preferably H; W is O, NR²⁵, or is N; V is 1 if W = O or NR²⁵, and is 2 if W = N; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; R²⁴ is H or C₁-C₄ alkyl; R²⁵ is H or C₁-C₄ alkyl; wherein R⁶ is H or C₁-C₄ alkyl, preferably H; Q is NR¹⁰, N or O; V is 1 if Q = O or NR¹⁰ and is 2 if Q = N; R¹⁰ is H or C₁-C₄ alkyl; R²⁴ is H or C₁-C₄ alkyl; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; and a is an integer from 2 to 350, preferably 10 to 150, more preferably 20 to 100; where each M independently is H or a cation equivalent. 10. The process according to any one of the preceding claims, wherein the polymeric dispersant comprises structural units of formulae (Ia) wherein R¹ is H or methyl, X is a chemical bond and R² is OM; (Id) wherein R⁶ is H or methyl, Q is O and R⁷ is H; and Construction Research & Technology GmbH PAT-0048-WO-PCT 44 (IIa) wherein R¹⁰ and R¹² are H, R¹¹ is H or methyl, n2 is 0, 1 or 2, E is C₂-C₆ alkylene, G is O, or E and G together are a chemical bond, A is CH₂- CH₂ and R¹³ is H. 11. The process according to any one of the preceding claims, wherein the molar mass of the polymeric dispersant is in the range of 500 g/mol to 200,000 g/mol. 12. The process according to any one of the preceding claims, wherein the molar mass of the polyether side chains is in the range of 500 g/mol to 8,000 g/mol. 13. The process according to any one of claims 1 to 5, wherein the polymeric dispersant is a polycondensation product which h comprises the structural units (IV) and (V) and, optionally, the structural unit (III): (III) wherein 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; n3 is 1 or 2; 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 or O; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; a2 is an integer from 1 to 300; R²⁶ is H, C₁-C₁₀ alkyl, C₅-C₈ cycloalkyl, aryl, or heteroaryl having 5 to 10 ring atoms, of which 1 or 2 atoms are heteroatoms selected from N, O and S; where the structural unit (IV) is selected from the structural units (IVa) and (IVb) wherein 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; Construction Research & Technology GmbH PAT-0048-WO-PCT 45 E³ is N, NH or O, with the proviso that m is 2 if E³ is N and m is 1 if E³ is NH or O; A is C₂-C₅ alkylene or CH₂CH(C₆H₅), preferably C₂-C₃ alkylene; b is an integer from 0 to 300; M independently is H or a cation equivalent; wherein V² is phenyl or naphthyl and is optionally substituted by 1 or two radicals selected from R⁸, OH, OR⁸, (CO)R⁸, COOM, COOR⁸, SO₃R⁸ and NO₂; R^7A is COOM, OCH₂COOM or OPO₃M₂; M is H or a cation equivalent; and R⁸ is C₁-C₄ alkyl, phenyl, naphthyl, phenyl-C₁-C₄ alkyl or C₁-C₄ alkylphenyl wherein R⁵ is H, CH₃, COOH or substituted or unsubstituted phenyl or naphthyl; R⁶ is H, CH₃, COOH or substituted or unsubstituted phenyl or naphthyl. 14. The process according to any one of the preceding claims, wherein the alkali- free, aluminum-based shotcrete accelerator comprises at least on agent selected from aluminum salts, aluminum complexes, aluminum hydroxides, and mixtures thereof. 15. The process according to any one of the preceding claims, wherein the cementitious composition comprises a cementitious binder selected from Portland cement, calcium aluminate cement and/or sulfoaluminate cement, preferably Ordinary Portland Cement. 16. Kit-of-parts for use with a shotcrete composition comprising (i) an alkali-free, aluminum-based shotcrete accelerator and (ii) a colloidal suspension of a low-solubility salt of at least one polyvalent metal cation selected from Fe³⁺, Construction Research & Technology GmbH PAT-0048-WO-PCT 46 Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Al³⁺ and mixtures thereof, and at least one anion which is able to form a low-solubility salt with the polyvalent metal cation, wherein the anion is selected from carbonate, oxalate, silicate, phosphate, polyphosphate, phosphite, borate, aluminate, sulfate, fluoride and mixtures thereof, with the proviso that where the cation comprises Ca²⁺ and the anion comprises aluminate, the molar ratio of sulfate : (Ca²⁺ + aluminate) in the colloidal suspension is lower than 0.30, preferably lower than 0.25, more preferably lower than 0.10, wherein the colloidal suspension of the low-solubility salt is stabilized against crystal growth by at least one polymeric dispersant which comprises anionic and/or anionogenic groups.