Mineral binder for use as cement-replacement in building materials

Abstract

A mineral binder comprising a mixture of a binder material and an activator, whereby - the binder material is selected from hardened mineral binder material, latent hydraulic and / or pozzolanic materials; - the activator is selected from magnesium oxide, calcium oxide, magnesium hydroxide and / or calcium hydroxide; and - with respect to the weight of the mixture, a proportion of binder material is from 50 – 95 wt.%, especially 70 – 85 wt.%, and a proportion of activator is from 5 – 50 wt.%, especially 15 – 30 wt.%.

Description

[0001] MINERAL BINDER FOR USE AS CEMENT-REPLACEMENT IN BUILDING MATERIALS

[0002] Technical field

[0003] The invention relates to a mineral binder based on a binder material and an activator as well as a mineral binder composition comprising the mineral binder and aggregates. Furthermore, the invention is related to a workable mineral binder composition, a composition for producing a brick or a block, and a hardened building material. Additional aspects of the invention are a method for processing mineral binder compositions and producing building materials as well as the use of the mineral binder or the mineral binder composition.

[0004] Background art

[0005] In the field of construction, one of the most widely used inorganic building material is concrete. Concrete typically is made of cement, which is the hydraulic binder, of aggregates and of water.

[0006] However, the production of cement requires large amounts of energy and generates a considerable amount of climate relevant CO2. In order to reduce energy consumption and CO2emissions, cement in mineral binder compositions can be partially replaced by latent hydraulic and / or pozzolanic materials, such as fly ash, slag or silica fume. Such cement replacements are by-products in various industrial processes and are therefore beneficial, for example in terms of CO2balance. However, setting of mixes comprising considerable proportions of such cement replacements usually takes much longer and workability might be also affected negatively.

[0007] In order to overcome these drawbacks, it is known to use special additives, which can partly compensate the negative effects of such replacements. However, some of these additives, such as corrosive or alkaline setting accelerators, viscosity modifiers or plasticizers, are hazardous and dangerous to handle.

[0008] Another approach towards more eco-friendly and cement-free building materials is disclosed in WO 2021 / 180318 A 1 (ETH Zurich) describing an additive for the production of clay-based hardenable building materials, which consists of: a) a dispersing agent, selected from aluminates, aluminate precursors, phosphates, silicates and / or polyacrylates, which is capable of dispersing clay particles in an aqueous slurry, and b) a coagulating agent, selected from salts of divalent metal cations, preferably salts of alkaline earth metals and / or iron, especially magnesium, calcium and / or iron salts, capable of causing clay particles to agglomerate in a aqueous slurry. This allows for processing and casting mortar- or concretelike building materials essentially without need for cementitious binders.

[0009] Nevertheless, there is still a need to provide cement replacements that allows for producing cement-free construction materials in an even more flexible manner.

[0010] Disclosure of the invention

[0011] It is an object of the present invention to provide an improved cement replacement, which in particular allows for providing mortar- or concrete-like building materials with as little cement, auxiliary products and environmental impact as possible. Preferably, a cement replacement shall be provided which is suitable for producing different types of low-cement or cement-free building materials, such as e.g. mortars, concretes, screeds, grout, blocks and bricks and the like in a flexible manner.

[0012] Surprisingly it was found that these objects can be achieved with a mineral binder according to claim 1. With the inventive mineral binder, it is possible to produce low-cement or even cement-free building materials in a highly flexible manner. The inventive mineral binder does not require any cement but can be used as a 1 : 1 cement replacement in very different low- cement or cement-free building materials, such as e.g. mortars, concretes, screeds, grouts, renders, blocks and / or clay bricks. For producing the low-cement or cement-free building materials, the mineral binder can be combined for example with suitable aggregates, e.g. fillers, sand, gravel, demolition waste as a mixture of exclusively mineral construction waste from solid components (such as concrete, brick, sand-lime brick and / or natural stone masonry), and / or excavation material.

[0013] In this way, processing and workability are very similar to common cement-based building materials and it is not necessary to adapt already known and used construction processes and / or tools for common building materials.

[0014] Without being bound by theory, it is believed that the activator, especially the magnesium oxide, enhances the reactivity of the latent hydraulic and / or pozzolanic material in the innovative mineral binder. Consequently, the new mineral binder can harden at room temperature within about 48 hours, especially within 15 hours, upon contact with water. This comes with surprise. So far, conventional activation of latent hydraulic and / or pozzolanic materials as for example slag usually was done with cement, lime and / or sodium silicate.

[0015] Since the mixture of the mineral binder mainly is based on latent hydraulic and / or pozzolanic materials, the environmental impact of the mineral binder is much lower than for ordinary cement that requires calcination at high temperatures. This is in particular true for slag, which is a by-product from steel-industry.

[0016] Noteworthy, the densities of the inventive mineral binders usually are lower than cementbased binders. Thus, building materials such as e.g. mortar or concrete produced with the inventive mineral binder can be formulated to have a rather low density too.

[0017] Further aspects of the present invention are subject of other independent claims. Preferred embodiments of the invention are subject of dependent claims.

[0018] Detailed Description of the Invention

[0019] A first aspect of the present invention relates to a mineral binder comprising a mixture of a binder material and an activator, whereby: the binder material is selected from hardened mineral binder materials, latent hydraulic materials and / or pozzolanic materials; the activator is selected from magnesium oxide, calcium oxide, magnesium hydroxide and / or calcium hydroxide; and with respect to the weight of the mixture, a proportion of binder material is from 50 - 95 wt.%, especially 70 - 85 wt.%, and a proportion of activator is from 5 - 50 wt.%, especially 15 - 30 wt.%.

[0020] Most preferably, with respect to the weight of the mixture, a proportion of binder material is from 73- 77 wt.%, especially 75 wt.%, and a proportion of activator is from 23 - 37 wt.%, especially 25 wt.%.

[0021] Especially, the binder material is selected from hardened mineral binder material, fly ash, slag or silica fume, especially from slag.

[0022] Slag is a by-product of steel industry. Slag usually is a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals. The major components of slag include oxides of calcium, magnesium, silicon, iron, and / or aluminum, optionally with lesser amounts of manganese, phosphorus, and others depending on the specifics of the raw materials used.

[0023] In particular, the particle size of the binder material, especially slag, ranges from 0.1 - 500 pm, preferably 1 - 100 pm, especially 5 - 63 pm.

[0024] In particular, the activator is selected from magnesium oxide. Especially the activator is selected from magnesium oxide and the binder material is selected from slag. This turned out to be a highly suitable combination for a mineral binder.

[0025] A particle size of the activator, especially magnesium oxide, preferably ranges from 5 - 800 pm, especially 14 - 200 pm. By choosing particle sizes of binder materials and / or activators, especially slag and / or magnesium oxide, within these ranges, it is possible to obtain highly reactive mineral binders.

[0026] In the present context, the particle size can e.g. be determined by laser diffraction as described in ISO 13320:2009. Preferably, a particle size of non-spherical or irregular particles is represented by the equivalent spherical diameter of a sphere of equivalent volume. Especially, the lower values of the ranges given for the particle size represent Dvivalues whereas the upper values of the ranges given for the particle size represent Dv99values. Put differently, in this case, 1% of the particles have size smaller than the lower value of a range, whereas 1% of the particles have size larger than the upper value of a range.

[0027] In particular, the mineral binder further comprises a clay component selected from crushed fines of clay brick (CFCB) and / or calcined clay, whereby a weight ratio of the clay component to the mixture of binder material and activator is from 5:95 - 70:30, especially 10:90 - 25:75, in particular 10:90 - 15:85.

[0028] CFCB can for example be obtained by crushing and optionally sieving waste of fired clay bricks and / or tiles. Fired clay bricks are burned in a kiln and usually comprise sand and alumina as main components. Additionally, lime and other substances, especially iron oxide and / or magnesia, may be present as minor components. "Main component(s)" are meant to be the component(s) with the highest weight proportion(s). For example, a fired clay brick may comprise 50 - 60 wt.% sand, 20 - 30 wt.% alumina and 2 - 5 wt.% lime. The balance in particular is made up with iron oxide and / or magnesia.

[0029] Wasted fired clay bricks and / or tiles can be obtained from brick manufacturers, ceramic producers and / or recycling companies.

[0030] CFCB can be used to accelerate the hardening reaction, dilute the mineral binder and reduce the density of the mineral binder after hardening. Specifically, by increasing the proportion of CFCB in the mineral binder, the density of the hardened material decreases as well as the late compressive strength. A particle size of the clay component, especially the CFCB, is for example > 0 - 4 mm. If the mineral binder is used to prepare a mortar, the grain size can be for example > 500 m - 4 mm.

[0031] In a preferred embodiment, a particle size of the clay component, especially the CFCB, is below 500 pm, especially between 50 - 200 pm. The particle size of the clay component allows for controlling the hardening rate of the mineral binder.

[0032] Especially, the binder material comprises or consists of hardened mineral binder material, especially particulate hardened mineral binder material. In particular, hardened mineral binder material is selected from hydrated mineral binder material and / or calcined brick materials.

[0033] Especially, the hardened mineral binder material comprises or consists of hardened cement, hardened gypsum, hardened lime and / or calcined clay. Optionally, the hardened mineral binder material may additionally comprise aggregates, e.g. filler, sand, gravel and / or rock.

[0034] According to a special embodiment, the hardened mineral binder material is particulate demolition waste.

[0035] In particular, the hardened mineral binder material comprises crushed bricks, crushed tiles, crushed hardened gypsum, crushed mortar and / or crushed concrete. Thereby, bricks and / or tiles in particular comprise or consist of calcined clay.

[0036] A density of the hardened mineral binder material preferably is in the range of 2.3 - 3.1 g / cm3, in particular 2.5 - 2.9 g / cm3, e.g. 2.6 - 2.8 g / cm3. Especially, the density is meant to be the true density or particle density of the particulates of the hardened mineral binder material. The true density or particle density can e.g. be measured with helium pycnometry.

[0037] In a highly preferred embodiment, the hardened mineral binder material, especially particulate demolition waste, comprises, with respect to the total weight of the hardened mineral binder material, 40 - 80 wt.%, in particular 50 - 70 wt.%, e.g. 55 - 65 wt.%, of crushed bricks, crushed tiles, and / or crushed hardened gypsum, and 20 - 60 wt.%, especially 30 - 50 wt.%, e.g. 35 - 45 wt.%, of crushed mortar and / or crushed concrete.

[0038] In this case, preferably, a proportion of the hardened mineral binder material, with respect to the weight of the mixture, is from 50 - 85 wt.%, in particular 50 - 75 wt.%, especially 52 - 65 wt.%, e.g. 54 - 62 wt.%.

[0039] Thereby, preferably, a proportion of the activator, with respect to the weight of the mixture, is chosen in the range of 15 - 50 wt.%, in particular 25 - 50 wt.%, especially 35 - 48 wt.%, e.g. 38 - 46 wt.%.

[0040] Further preferred, a mean particle size of the hardened mineral binder material, especially demolition waste, is in the range of 5 - 60 pm, in particular 15 - 45 pm, for example 25 - 35 pm. Especially, the mean particle size is meant to be the D50 value (50% of particles are larger than the value indicated and 50% of the particles are smaller than the value indicated).

[0041] Furthermore, preferably the mineral binder comprises a phosphate whereby a weight ratio of the phosphate to the mixture of the binder material and the activator is from 0.5:99.5 - 50:50, especially 1 :99 - 30:70, especially 5:95 -25:75. The phosphate improves activation and hardening of the mineral binder. Thus, in particular, the phosphate can be used as a co-activator together with the other activator. In particular, the phosphate increases and delays the maximum in heat release during the hardening process. Additionally, the phosphate helps dispersing particles, e.g. clay particles, after mixing the mineral binder with water and optionally further components.

[0042] Especially, the phosphate is a solid substance, especially a particulate substance. A particle size of the particulate phosphate preferably is from 30 - 800 m.

[0043] In particular, the phosphate is a polyphosphate, e.g. with 3 to 20 phosphate groups.

[0044] Especially, the phosphate is a pyrophosphate, an orthophosphate and / or a metaphosphate. Pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P-O-P linkage. Orthophosphates are anions or salts of orthophosphoric acid (H3PO4). Especially the phosphate is a polymetaphosphate, in particular an alkali metal polymetaphosphate, especially with formula (M'P03)nwhereby M' = monovalent cation, in particular an alkali metal cation, and 3 < n < 20. Polymetaphosphates have a cyclic structure.

[0045] The phosphate in particular is an alkali and / or ammonium phosphate. An alkali phosphate preferably is selected from sodium phosphate and / or potassium phosphate.

[0046] Especially, the phosphate is a trimetaphosphate and / or a hexametaphosphate, more preferably an alkali metal trimetaphosphate and / or an alkali metal hexametaphosphate, in particular sodium trimetaphosphate (NaTMP) and / or sodium hexametaphosphate (NaHMP).

[0047] If the phosphate for example is sodium hexametaphosphate (NaPO3)6, each hexametaphosphate preferably comprises six phosphorous groups comprising a central phosphor atom, which is bound on average to three oxygen atoms, i.e. six NaPO3monomers. Likewise, if the phosphate is sodium trimetaphosphate (NaPO3)3, each trimetaphosphate preferably comprises three phosphorous groups comprising a central phosphor atom, which is bound on average to three oxygen atoms, i.e. three NaPO3monomers.

[0048] In a further preferred embodiment, the mineral binder comprises an additional binder compound which is different form the binder material in the mixture and whereby the additional binder compound is selected from a hydraulic binder, a pozzolanic compound or a mixture thereof, whereby, preferably, a weight ratio of the additional binder compound to the mixture is from 1 :99- 60:40, especially 2:98 - 50:50, in particular 5:95 - 15:85. In particular, the additional binder compound is selected from gypsum and / or fly ash.

[0049] The additional binder compound can be used to reduce the proportion of the activator, especially the magnesium oxide, while maintaining the activation of the binder material, e.g. slag, and / or to further improve the activation of the binder material.

[0050] The mineral binder might comprise cement, lime and / or silicates, especially an alkali metal silicate, in particular sodium silicate and / or potassium silicate. For example, the silicate is a sodium silicate with a ratio of SiO2:Na2O in the range of 1 - 2.8 and / or a potassium silicate with a ratio of SiO2: l<20 in the range of 1 - 2.8

[0051] However, in particular, a proportion of cement, lime and / or silicates, especially alkali metal silicates, in the mineral binder is below 10 wt.%, especially below 5 wt.%, in particular below 1 wt.% or 0 % by weight, with respect to the total weight of the mineral binder.

[0052] Especially the mineral binder is cement-free, lime-free and / or silicate-free.

[0053] In particular, the mineral binder does not comprise a silicate, especially an alkali metal silicate, in particular sodium silicate and / or potassium silicate. Particularly, the mineral binder does not comprise a sodium silicate with a ratio of SiO2:Na2O in the range of 1 - 2.8 and / or a potassium silicate with a ratio of SiO2:K2O in the range of 1 - 2.8.

[0054] In a first advantageous example, the mineral binder comprises or consist of:

[0055] 60 - 65 wt.% of binder material, especially slag

[0056] 15 - 25 wt.% of activator, especially magnesium oxide

[0057] 12 - 20 wt.% of phosphate, especially hexametaphosphate

[0058] In a second advantageous example, the mineral binder comprises or consist of:

[0059] 25 - 35 wt.% of binder material, especially slag

[0060] 5 - 15 wt.% of activator, especially magnesium oxide

[0061] 0.5 - 5 wt.% of phosphate, especially hexametaphosphate

[0062] - 45 - 65 wt.% of CFCB

[0063] In another preferred embodiment, the mineral binder comprises or consist of:

[0064] 50 - 75 wt.%, especially 52 - 65 wt.%, e.g. 54 - 62 wt.%, binder material in the form of hardened mineral binder material, whereby the hardened mineral binder material, with respect to the total weight of the hardened mineral binder material, comprises 40 - 80 wt.%, in particular 50 - 70 wt.%, e.g. 55 - 65 wt.%, of crushed bricks, crushed tiles, and / or crushed hardened gypsum, and 20 - 60 wt.%, especially 30 - 50 wt.%, e.g. 35 - 45 wt.%, of crushed mortar and / or crushed concrete;

[0065] 15 - 50 wt.%, in particular 25 - 50 wt.%, especially 35 - 48 wt.%, e.g. 38 - 46 wt.%, of the activator; thereby, preferably, a mean particle size of the hardened mineral binder material, especially demolition waste, is in the range of 5 - 60 pm, in particular 15 - 45 pm, for example 25 - 35 pm, and / or a density of the hardened mineral binder material is in the range of 2.3 - 3.1 g / cm3, in particular 2.5 - 2.9 g / cm3, e.g. 2.6 - 2.8 g / cm3.

[0066] In particular, the mineral binder can be provided as a one-component mixture comprising the mixture of binder material and activator, especially slag and magnesium oxide. Optionally one or more of the above-mentioned optional components can be comprised in the one-component mixture as well. As it turned out, such kind of one-component mixtures are storage stable up to six months, especially if all of the components are added in dry form.

[0067] However, the mineral binder can be provided in the form of a two- or multicomponent mixture if desired. This allows for flexibly adjusting the mineral binder to specific needs.

[0068] A further aspect of the present invention is directed to a mineral binder composition comprising: a) a mineral binder as described above, and b) aggregates, especially filler, sand, gravel, fines, silt, clay, excavation material, a mineral fraction of soil and / or sludge.

[0069] Especially the mineral binder composition is a mortar, a concrete, a screed, a grout, a render or a composition for producing a brick. Sludge in particular is selected from aggregate sludge, concrete sludge and / or sewage sludge. Especially sludge is in the form of a slurry, a semi-solid material or in the form of a dry powder. In particular, a particle size of solid particles in the sludge is < 63 pm.

[0070] Aggregate sludge is a slurry comprising water and solid particulate aggregate, e.g. obtained as a waste during the process of washing aggregates, such as e.g. sand and / or gravel. Concrete sludge is a construction waste in the form of a slurry comprising water and solid concrete particles. Sewage sludge is the residual that is produced as a by-product during sewage treatment of industrial or municipal wastewater.

[0071] Sludge in the form of a semi-solid material or a dry powder can be obtained by reducing or removing the proportion of liquids, especially water, by drying.

[0072] Especially, the clay used as aggregates is uncalcined clay, e.g. hydrated aluminosilicate particles.

[0073] If the mineral binder composition is a composition for producing a brick, especially a clay brick, the aggregates preferably comprise clay, sand and / or sludge.

[0074] In particular, clays consist of particles with a particle size smaller than 4 pm, more preferably smaller than 2 pm. The particle sizes are d90-values, which are determined by laser diffraction, especially according to standard ISO 13320:2009. Thus, 90% of the particles are smaller than the given particle sizes. Clay particles are preferably hydrated aluminosilicate particles.

[0075] Preferably, clays comprise phyllosilicate minerals. Especially, clays are described by presence of two-dimensional sheets, tetrahedral (SiO4) and octahedral (AI2O3). They are classified 2: 1 clays when an octahedral sheet is sandwiched between two tetrahedral sheets, whereas if there is only one tetrahedral and one octahedral group in each layer the clay is classified as a 1 : 1 clay. Especially, the clays comprise or consist of kaolinite, smectite, montmorillonite, illite, bentonite, and / or hectorite. In a further preferred embodiment, a mineral fraction of soil, excavation material and / or sludge can be used as aggregates. In this case, no neat sands and / or gravel is required.

[0076] Especially, clay-containing materials in the form of a clay-containing mineral fraction of soil can be used as the aggregates. This is of special interest for obtaining compositions for producing clay bricks. Such clay containing materials can for example be obtained from clay quarries or clay pits. In this case, there is in principle no need to add further aggregates such as e.g. sands. Nevertheless, this is of course possible if desired.

[0077] In particular, if clay and / or clay containing materials is used as aggregate and the mineral binder comprises a clay component, the clay and / or clay containing material(s) used as aggregate is / are different from the clay component of the mineral binder.

[0078] According to another preferred embodiment, aggregates may comprise a filler, especially with a particle size of 5 - 50 m, in particular of 10 - 30 pm. In particular, the filler is an inorganic material, especially comprising or consisting of calcium carbonate.

[0079] Especially, a weight ratio of the aggregates to the mineral binder in the mineral binder composition is from 500: 1 - 1 :20, especially 300: 1 - 1 : 1.

[0080] In a first example of a mineral binder composition, a weight ratio of the aggregates to the mineral binder in the mineral binder composition from 200: 1 - 50: 1 and the aggregates are selected from excavation material.

[0081] Thereby, the mineral binder composition in particular comprises: the binder material and the activator, especially slag and magnesium oxide, whereby, with respect to the weight of the mixture of the binder material and the activator, a proportion of binder material, especially slag, is from 70 - 85 wt.%, and a proportion of activator, especially magnesium oxide, is from 15 - 30 wt.%; phosphate, especially hexametaphosphate, whereby a weight ratio of the phosphate to the mixture of binder material and activator is from 10:90 - 20:80. In a second example of a mineral binder composition, a weight ratio of the aggregates to the mineral binder in the mineral binder composition from 200: 1 - 100: 1 and the aggregates are selected from sand, gravel, silt and / or clay excavation material.

[0082] In a third example of a mineral binder composition, a weight ratio of the aggregates to the mineral binder in the mineral binder composition from 40: 1 - 10: 1 and the aggregates are selected from sand, gravel, and / or sludge, especially with particle sizes of > 0 - 8 mm.

[0083] Thereby, the mineral binder composition in particular comprises: the binder material and the activator, especially slag and magnesium oxide, whereby, with respect to the weight of the mixture of binder material and activator, a proportion of binder material, especially slag, is from 70 - 85 wt.%, and a proportion of activator, especially magnesium oxide, is from 15 - 30 wt.%; phosphate, especially hexametaphosphate, whereby a weight ratio of the phosphate to the mixture of binder material and activator is from 10:90 - 20:80;

[0084] CFCB, whereby a weight ratio of the CFCB to the mixture of binder material and activator is from 5:95 - 15:85.

[0085] Such a mineral binder composition is for example suitable as cement-free concrete.

[0086] In a fourth example of a mineral binder composition, a weight ratio of the aggregates to the mineral binder in the mineral binder composition from 10: 1 - 1 : 1 , especially from 3: 1 - 1 : 1 , and the aggregates are selected from sand, gravel, and / or sludge, especially with particle sizes of > 0 - 16 mm.

[0087] Thereby, the mineral binder composition in particular comprises: the binder material and the activator, especially slag and magnesium oxide, whereby, with respect to the weight of the mixture of binder material and activator, a proportion of binder material, especially slag, is from 70 - 85 wt.%, and a proportion of activator, especially magnesium oxide, is from 15 - 30 wt.%; phosphate, especially hexametaphosphate, whereby a weight ratio of the phosphate to the mixture of binder material and activator is from 1 :99 - 10:90;

[0088] CFCB, whereby a weight ratio of the CFCB to the mixture of slag and magnesium oxide is from 50:50 - 65:35.

[0089] Such a mineral binder composition is for example suitable as cement-free structural concrete.

[0090] In a fifth example of a mineral binder composition, a weight ratio of the aggregates to the mineral binder in the mineral binder composition from 1 :2 - 1 : 10 and the aggregates are selected from sand and / or sludge, especially sludge.

[0091] Thereby, the mineral binder composition in particular comprises: the binder material and the activator, especially slag and magnesium oxide, whereby, with respect to the weight of the mixture of binder material and activator, a proportion of binder material, especially slag, is from 70 - 85 wt.%, and a proportion of activator, especially magnesium oxide, is from 15 - 30 wt.%; phosphate, especially hexametaphosphate, whereby a weight ratio of the phosphate to the mixture of binder material and activator is from 10:90 - 30:70;

[0092] CFCB, whereby a weight ratio of the CFCB to the mixture of binder material and activator is from 5:95 - 15:85. Such a mineral binder composition is for example suitable as cement-free mortar. If desired, in the these mineral binder compositions an additional binder compound can be used as described above, such as e.g. gypsum and / or fly ash.

[0093] The mineral binder composition might comprise cement, lime and / or silicates, especially an alkali metal silicate, in particular sodium silicate and / or potassium silicate. For example, the silicate is a sodium silicate with a ratio of SiO2:Na2O in the range of 1 - 2.8 and / or a potassium silicate with a ratio of SiO2: l<20 in the range of 1 - 2.8

[0094] However, in particular, a proportion of cement, lime and / or silicates, especially alkali metal silicates, in the mineral binder composition is below 10 wt.%, especially below 5 wt.%, in particular below 1 wt.% or 0 % by weight, with respect to the total weight of the mineral binder composition.

[0095] In particular, the mineral binder composition does not comprise a silicate, especially an alkali metal silicate, in particular sodium silicate and / or potassium silicate. Particularly, the mineral binder composition does not comprise a sodium silicate with a ratio of SiO2:Na2O in the range of 1 - 2.8 and / or a potassium silicate with a ratio of SiO2: l<20 in the range of 1 - 2.8.

[0096] Especially the mineral binder composition is cement-free, lime-free and / or silicate-free.

[0097] In particular, the mineral binder composition can be provided as a one-component mixture, especially in the form of a ready-mix product. A ready-mix product can be simply mixed with water in order to produce the mineral binder composition in workable state. However, mineral binder compositions in the form of two- or multi-component compositions are possible as well. In this case, for example, the mineral binder can be provided in a first component and the aggregates in a second component. In another example, the mineral binder is provided as a two-component composition as described above and the aggregates are provided as a further component. Another aspect of the present invention is related to a workable building material, comprising a mineral binder as described above or a mineral binder composition as described above, and water. Especially, the workable building material is a screed, mortar, concrete, grout, render or a composition for producing a brick. Preferably, a ratio of water to the mineral binder in the workable building material is from 0.25 - 0.8, especially 0.3 - 0.6, in particular 0.3 - 0.5. The proportion of water can in particular be adjusted based on the intended application.

[0098] As it turned out, with a workable building material according to the invention, which is subjected to a temperature of at least 50 °C, in particular of 60 - 100 °C, for hardening, it is possible to produce bricks with a compressive strength and a bending strength usually obtainable with ordinary bricks calcined at about 500 °C. Thus, the inventive mineral binder improves the mechanical properties, especially the compressive strength, significantly without need of high temperatures. Thus, the process can be performed with much less energy.

[0099] A further aspect of the invention is related to a hardened building material obtainable by hardening a workable building material as described above. Especially, the hardened building material is a formed body, e.g. a wall, a floor, a ceiling, a roof, a brick, a panel, a slab and / or a pillar.

[0100] Especially, the hardened building material is a brick, especially a clay brick.

[0101] The hardened building material can have a compressive strength of at least 1.4 MPa, and more particularly of at least 3 MPa or of 3 to 25 MPa. Thereby, no hydraulic binder, especially cement, is required.

[0102] A compressive strength in this range makes it possible to manufacture building blocks or vertical walls suitable for the construction of houses or buildings with up to four storeys without the use of materials such as hydraulic binders. It is important to mention that a compressive strength of at least 1 .4 MPa can be obtained after 24 hours of hardening, which allows construction progress with approximately the same speed as if the building material used is mortar or concrete.

[0103] In the present context, tests for the determination of the compressive strength (in N / mm2or MPa) are carried out following standard EN 12390-1 :2012, EN 12390-2:2019, EN 12390- 3:2019 and 12390-4:2000 with prisms (40x40x 160 mm).

[0104] A still further aspect of the invention is concerned with the use of a mineral binder as defined above or a mineral binder composition as described above for producing a hardenable building material. Thereby, the hardenable building material is in particular a mortar, concrete, screed, grout, render, backfilling material, soil stabilization composition and / or a composition for producing a brick.

[0105] Especially, the hardenable building material is a screed for flooring, a plaster for non- structural wall applications, a mortar, or a concrete composition.

[0106] For example, the mineral binder or the mineral binder composition is used for producing a formed body, e.g. a wall, a floor, a ceiling, a roof, a brick, a panel, a slab and / or a pillar.

[0107] Especially, the mineral binder as defined above or a mineral binder composition as described above can be used as a backfilling material, e.g. for civil engineering applications, as a mortar for brick layering, and / or for stabilization of soil and / or earth-based materials.

[0108] Another aspect of the invention is related to a method comprising the steps of: a) Providing or producing a mineral binder or a mineral binder composition as described above; b) Mixing the mineral binder or the mineral binder composition with water in order to produce a workable building material, whereby, preferably, a ratio of water to the mineral binder preferably is from 0.25 - 0.8, especially 0.3 - 0.6, in particular 0.3 -0.5;

[0109] Especially, the method further comprises the step of: c) Processing the workable building material by:

[0110] - applying it on a substrate, especially on a wall of a building, as a render;

[0111] - casting it as a screed on a substrate, especially on a floor of a building;

[0112] - casting it in a mold and / or extruding it to produce a formed body, especially a wall, a floor, a ceiling, a roof, a panel, a slab and / or a pillar;

[0113] - casting it in a mold and / or extruding it to produce a brick or a block, especially a clay brick; and / or

[0114] - using it as a grout, especially a tiling grout and / or a repair grout, whereby the grout in particular is used to fill a cavity, especially a crack and / or a joint.

[0115] Furthermore, the invention is concerned with a method for producing a brick and / or a block, especially a clay brick and / or clay block, comprising the steps of: a) Providing aggregates, especially clay containing mineral fraction of soil, clay, sand and / or sludge; b) Mixing the aggregates with a phosphate as described above, especially with an alkali and / or ammonium phosphate, in particular a trimetaphosphate and / or a hexametaphosphate; c) Optionally storing the mix of aggregates and phosphate for 0.5 - 30 days, especially 1 - 3 days. Thereby, preferably, humidity is controlled such that it does not change by more than 1.5%, especially 0.5% with respect to the initial humidity; d) Blending the mix of aggregates and phosphate with a mineral binder comprising the binder material and the activator, especially slag and magnesium oxide, as described above; e) Forming the brick or the block from the blend obtained in step d), especially by moulding and / or extrusion, in particular by additionally compacting the blend, e.g. by vibrocompacting, compressing and / or vibration; f) Curing the formed brick or block, especially at a temperature in the range of room temperature to 150 °C. More preferably, the formed brick or block in a first period, e.g. 0.5 - 30 days, is cured at room temperature, and in a subsequent second period, the formed brick or block is cured at a temperature of 50 - 150°C, especially 60 - 120°C.

[0116] Further advantageous embodiments and combinations of features of the invention result from the following detailed description and the patent claims.

[0117] Brief description of the drawings

[0118] The drawings used to explain the examples show:

[0119] Fig. 1 time resolved isothermal calorimetry measurements of mineral binders based on slag and MgO recorded during the hardening process;

[0120] Fig. 2 time resolved isothermal calorimetry measurements of mineral binders based on slag, MgO and sodium hexametaphosphate recorded during the hardening process;

[0121] Fig. 3 a comparison of the evolution of hardness of a sample with phosphate and a sample without phosphate;

[0122] Fig. 4 time resolved isothermal calorimetry measurements (23 °C) of mineral binders based on slag, MgO and gypsum recorded during the hardening process.

[0123] Examples

[0124] Mineral binders Table 1 shows several compositions of different mineral binders based on slag and magnesium oxide, which were mixed with water in order to produce workable mineral binders. All substances used are commercially available.

[0125] Specifically, for producing the workable mineral binders, slag was agitated for 10 seconds for homogenization followed by adding MgO and mixing for another 30 seconds.

[0126] Subsequently, water was added and mixing continued for another 3 - 5 minutes.

[0127] Table 1: Mineral binders based on slag and MgO

[0128] Fig. 1 shows time-resolved isothermal calorimetry measurements of the mineral binders R1 and M2 - M5 recorded during the hardening process. As evident, MgO is capable of activating the slag within a few hours when compared to the reference R1 . Most effective is mixture M4 with 75 g of slag and 25 g of MgO.

[0129] In table 2, further compositions of different mineral binders based are shown. Thereby, CFBC were used in addition to slag and magnesium oxide to dilute the mineral binder and obtain hardened mineral binders with reduced densities.

[0130] Tests for the determination of the compressive strength (in N / mm2or MPa) are carried out following standard EN 12390-1 :2012, EN 12390-2:2019, EN 12390-3:2019 and 12390- 4:2000 with prisms (40x40x 160 mm).

[0131] Table 2: Mineral binders based on slag, MgO and CFCB

[0132] Time-resolved isothermal calorimetry measurements (not presented here) showed that with increasing content of CFBC, the main peak of the heat flow slightly shifts to later times and decreases in intensity. Nevertheless, there is still a significant activation of the slag. Table 3 shows further mineral binders which are based on a mixture of 75 wt.% of slag and 25 wt.% of MgO (similar to mineral binder M4) and additionally comprise sodium hexmetaphosphate (NaHMP). Mineral binders M4 (no NaHMP) and M 12 (only NaHMP) are listed for reasons of comparison.

[0133] Table 3: Mineral binders based on slag, MgO and NaHMP

[0134] Fig. 2 shows time-resolved isothermal calorimetry measurements of these binders. As evident, addition of further mineral binders NaHMP increases the heat release and give rise to a delay, which depends on the proportion of NaHMP. The high heat release is representative of a higher compressive strength.

[0135] Table 4 shows two examples of mineral binders comprising slag, MgO, and CFCB with and without NaHMP.

[0136] Table 4: Mineral binders based on slag, MgO, CFCB and NaHMP

[0137] Fig. 3 shows the evolution of compressive strength of the two samples M 12 and M 13. All measurements were carried out following standard EN 12390-1 :2012, EN 12390-2:2019, EN 12390-3:2019 and 12390-4:2000 with prisms (40x40x 160 mm). As evident, the addition of phosphate drastically increases the compressive strength by about a factor of 2. Table 5 shows further mineral binders which are based on a mixture of slag 75 wt.% of slag and 25 wt.% of MgO (similar to mineral binder M4) and additionally comprise gypsum. The mineral binder M4 (no gypsum) is listed for reasons of compfarison. Table 5: Mineral binders based on slag, MgO and Gypsum

[0138] The time-resolved isothermal calorimetry measurements obtained with these samples are shown in Fig. 4. As evident, the addition of gypsum results in an early and intense peak after a few hours and a second peak around 35 hours. When using fly ash instead of gypsum, a similar behavior was found (not shown).

[0139] Thus, depending on the properties required, the proportions of slag, MgO, CFCB, gypsum and / or fly ash can be optimized.

[0140] Mineral binder compositions Table 6 shows a formulation of workable mineral binder compositions MB1 und MB2 comprising an inventive binder and aggregates in the form of excavation soil.

[0141] Table 6: Workable mineral binder composition for use as mortar Table 7 shows a formulation of workable mineral binder compositions MB3 and MB4 comprising an inventive binder and aggregates in the form of sludge, sand and gravel. Such compositions can be used as concrete replacement.

[0142] Table 7: Workable mineral binder composition for use as concrete

[0143] Table 8 shows further formulations of mineral binder compositions MB5, MB6 and MB7 comprising an inventive binder and various aggregates. Such compositions can be used as concrete replacement.

[0144] Table 8: Mineral binder composition for use as concrete Another mineral binder composition MB8 was produced from:

[0145] 58 wt.% mixed particulate demolition waste consisting of, with respect to the total weight of the mixed demolition waste, 60 wt.% of crushed bricks, crushed tiles, crushed hardened gypsum and 40 wt.% recycled concrete, having a mean particle size (D50) of 29.5 pm and a density of 2.66 g / cm3(measured with helium pycnometry); and

[0146] 42 wt.% of an activator, e.g. magnesium oxide.

[0147] A workable composition was produced by mixing 350 kg / m3of mineral binder MB8 with 1670 kg / m3aggregates (sand, gravel) and 160 kg / m3water. Thereby, the mineral binder MB8 and aggregates were mixed under dry conditions for 1 min. Subsequently the mixing water was added while continuing mixing. The wet mixing time was 6 min.

[0148] Thereby, a workable composition with a fresh density of 2280 kg / m3, a flow table spread of 65 cm and an open time of 30 min. was obtained (flow table spread can e.g. be assessed according standard EN 12350-5).

[0149] The compressive strength after 7 days was 16 MPa whereas the compressive strength after 14 days was 23 MPa. After 28 days, the compressive strength was 30 MPa.

[0150] Production of bricks

[0151] Clay bricks were produced as follows: a) Sodium phosphate was added to a mixture comprising clay containing earth, sand (0-4 mm) and sludge. The mixture was agitated for 3 min. b) The blended material of step a) (initial water content about 9.4 - 17 wt.% with respect to overall weight of the material) was left for rest for 2 days with control of humidity and temperature. Specifically, humidity was controlled such that it did not change by more than 1.5%, with respect to the initial humidity. c) The material of step b) was mixed with a blend of magnesium oxide and slag. d) A brick was formed by compression in a mold. e) Curing the brick of step d) for 2 days at room temperature and high relative humidity. f) After 2 days, the brick was cured at 105°C in oven until stabilization of material weight.

[0152] After storing the brick for several days, mechanical strength tests were performed (water content of test specimen: 0.025 wt.%). The tests revealed compressive strength in the range of 9.2 - 13.8 MPa.

[0153] For reasons of comparison, a brick was produced in a similar manner but without addition of phosphate, MgO and slag. In this case the compressive strength was as low as 3.8 MPa.

[0154] The method for producing bricks can be performed in a similar manner to produce blocks.

Claims

Claims1 . Mineral binder comprising a mixture of a binder material and an activator, whereby- the binder material is selected from hardened mineral binder material, latent hydraulic and / or pozzolanic materials;- the activator is selected from magnesium oxide, calcium oxide, magnesium hydroxide and / or calcium hydroxide; and- with respect to the weight of the mixture, a proportion of binder material is from 50 - 95 wt.%, especially 70 - 85 wt.%, and a proportion of activator is from 5 - 50 wt.%, especially 15 - 30 wt.%.

2. Mineral binder according to claim 1, whereby the binder material is selected from fly ash, slag or silica fume, especially from slag.

3. Mineral binder according to any of preceding claims, whereby the activator is selected from magnesium oxide.

4. Mineral binder according to any of preceding claims, whereby the binder material is selected from slag and the activator is selected from magnesium oxide.

5. Mineral binder according to any of preceding claims, further comprising a clay component selected form crushed fines of clay brick (CFCB) and / or calcined clay, whereby a weight ratio of the clay component to the mixture is from 5:95 - 70:30, especially 10:90 - 25:75, in particular 10:90 - 15:85.

6. Mineral binder according to any of preceding claims, further comprising a phosphate, especially sodium hexametaphosphate (NaHMP), whereby a weight ratio of the phosphate to the mixture is from 0.5:99.5 - 50:50, especially 1 :99 - 30:70, especially 5:95 -25:75.Mineral binder according to any of preceding claims, further comprising an additional binder compound which is different form the binder material in the mixture and whereby the additional binder compound is selected from a hydraulic binder, a pozzolanic compound or a mixture thereof, in particular gypsum and / or fly ash, whereby a weight ratio of the additional binder compound to the mixture of the binder material and the activator is from 1 :99- 60:40, especially 2:98 -50:50, in particular 5:95 - 15:

85. Mineral binder according to any of preceding claims, whereby a proportion of cement, lime and / or silicates, especially alkali metal silicates, in the mineral binder is below 10 wt.%, especially below 5 wt.%, in particular below 1 wt.% or 0 % by weight, with respect to the total weight of the mineral binder. Mineral binder according to any of preceding claims whereby the mineral binder is cement-free, lime-free and silicate-free. . Mineral binder according to any of preceding claims whereby a particle size of the activator, especially the magnesium oxide, is from 5 - 800 pm, especially 1 - 200 pm.

1. Mineral binder according to any of preceding claims whereby a particle size of the binder material, especially slag, is from 2 - 100 pm, especially 5 - 63 pm.

2. Mineral binder according to any of preceding claims, whereby the binder material comprises hardened mineral binder material, especially the hardened mineral binder material comprises hardened cement, hardened gypsum, hardened lime and / or calcined clay. . Mineral binder according to claim 12, whereby the hardened mineral binder material comprises, with respect to the total weight of the hardened mineral binder material, 40 - 80 wt.%, in particular 50 - 70 wt.%, e.g. 55 - 65 wt.%, of crushed bricks, crushed tiles, and / or crushed hardened gypsum, and 20 - 60 wt.%, especially 30 - 50 wt.%, e.g. 35 - 45 wt.%, of crushed mortar and / or crushed concrete.Mineral binder according to any of claims 12 - 13, whereby a proportion of the hardened mineral binder material, with respect to the weight of the mixture, is from 50 - 85 wt.%, in particular 50 - 75 wt.%, especially 52 - 65 wt.%, e.g. 54 - 62 wt.%, and / or a proportion of the activator, with respect to the weight of the mixture, is chosen in the range of 15 - 50 wt.%, in particular 25 - 50 wt.%, especially 35 - 48 wt.%, e.g. 38 - 46 wt.%. Mineral binder according to any of claims 12 - 14, whereby a mean particle size of the hardened mineral binder material is in the range of 5 - 60 pm, in particular 15 - 45 pm, for example 25 - 35 pm, and / or a density of the hardened mineral binder material is in the range of 2.3 - 3.1 g / cm3, in particular 2.5 - 2.9 g / cm3, e.g. 2.6 - 2.8 g / cm3. Mineral binder composition, especially a mortar or a concrete composition, comprising a) a mineral binder as defined in any of preceding claims, and b) aggregates, especially filler, sand, gravel, fines, clay, excavation material and / or sludge. Mineral binder composition according to claim 16, whereby a proportion of cement, lime and / or silicates, especially alkali metal silicates, in the mineral binder composition is below 10 wt.%, especially below 5 wt.%, in particular below 1 wt.% or 0 % by weight, with respect to the total weight of the mineral binder composition. Mineral binder composition according to any of claims 16 - 17, whereby the mineral binder composition is cement-free, lime-free and silicate-free. Workable building material, especially a cement-free screed for flooring, a plaster for non-structural wall applications, a mortar, and / or a concrete composition, comprising a mineral binder according to any of claims 1 - 15, or a mineral binder composition according to any of claims 16 - 18, and water, whereby a ratio of water to the mineral binder is from 0.25 - 0.8, especially 0.3 - 0.6, in particular 0.3 - 0.5.

20. Composition for producing a brick or a block, comprising a mineral binder according to any of claims 1 - 15 and a mineral fraction comprising clay particles.

21. Hardened building material obtainable by hardening a workable building material according to any of claims 16 - 19 or a composition for producing a brick according to claim 20.

22. A method comprising the steps of: a) Providing or producing a mineral binder according to any of claims 1 - 15, a mineral binder composition according to any of claims 16 - 19, or a composition for producing a brick according to claim 20; b) Mixing the mineral binder, the mineral binder composition or the composition for producing a brick with water in order to produce a workable building material, whereby a ratio of water to the mineral binder preferably is from 0.25 - 0.8, especially 0.3 - 0.6, in particular 0.3 - 0.5;23. Method according to claim 22 further comprising the step of: c) Processing the workable building material by:- applying it on a substrate, especially on a wall of a building, as a render;- casting it as a screed on a substrate, especially on a floor of a building;- casting it in a mold and / or extruding it to produce a formed body, especially a wall, a floor, a ceiling, a roof, a panel, a slab and / or a pillar;- casting it in a mold and / or extruding it to produce a brick or block, especially a clay brick; and / or- using it as a grout, especially a tiling grout and / or a repair grout, whereby the grout in particular is used to fill a cavity, especially a crack and / or a joint.

24. Method according to any of claims 22 - 23, whereby a brick or a block is produced, especially a clay brick or clay block, by:a) Providing aggregates, especially clay containing mineral fraction of soil, clay, sand and / or sludge; b) Mixing the aggregates with a phosphate as described above, especially with an alkali and / or ammonium phosphate, in particular a trimetaphosphate and / or a hexametaphosphate; c) Optionally storing the mix of aggregates and phosphate for 0.5 - 30 days, especially 1 - 3 days. Thereby, preferably, humidity is controlled such that it does not change by more than 1.5%, especially 0.5% with respect to the initial humidity; d) Blending the mix of aggregates and phosphate with a mineral binder comprising the binder material and the activator, especially slag and magnesium oxide, as described above; e) Forming the brick or block from the blend obtained in step d), especially by moulding and / or extrusion, in particular by additionally compacting the blend, e.g. by pressing and / or vibration; f) Curing the formed brick or block, especially at a temperature in the range of room temperature to 150 °C. More preferably, the formed brick in a first period, e.g. 0.5 - 30 days is cured at room temperature, and in a subsequent second period, the formed brick is cured at a temperature of 50 - 150 °C, especially 100 - 120 °C. Use of a mineral binder or a mineral binder composition as defined in any of preceding claims for producing a hardenable building material, especially a mortar, concrete, screed, grout, render, and / or a composition for producing a brick. Use of a mineral binder or a mineral binder composition as defined in any of preceding claims whereby the mineral binder or the mineral binder composition is used forproducing a wall, a floor, a floor screed, a ceiling, a roof, a brick, a panel, a slab and / or a pillar.

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