Test method for the effect of sand quality on plasticizing additives in mineral binder compositions

Abstract

A method of characterizing sand in terms of plasticizing additive adsorption, comprising the steps of: a) providing a plasticizing additive aqueous mixture having a defined concentration of plasticizing additive; b) determining a characteristic of the aqueous mixture, wherein the characteristic is related to the proportion of the plasticizing additive in the aqueous mixture; c) contacting a sand sample to be analyzed with the aqueous mixture or a sample thereof, such that the sand sample is completely immersed in the aqueous mixture or the sample thereof; d) taking an upper clear liquid sample from the mixture of step c); e) determining the same characteristic of the upper clear liquid sample as in step b); f) comparing the characteristic of the aqueous mixture or the sample thereof obtained in step b) with the characteristic of the upper clear liquid sample of step e) to determine whether the characteristics differ from each other by more than a predetermined threshold.

Description

Technical Field

[0001] This invention relates to a method for characterizing sand in terms of plasticizer adsorption. Furthermore, this invention relates to a method for preparing mineral binder compositions. Background Technology

[0002] The quality of sand has a significant impact on the performance of mortar or concrete and can cause a variety of problems, such as increased water demand, high demand for plasticizers, leaching, and pumpability issues. Some types of sand can even generate multiple interfering problems.

[0003] Several key causes of problematic sand can be identified, which negatively impact the workability of concrete: low fineness, high fineness, poor particle shape, water absorption, and the adsorption of plasticizers.

[0004] In particular, the presence of adsorbent materials (e.g., clay) leads to undesirable effects in sand, manifested as, for example, a higher demand for water and a higher demand for the adsorption of plasticizers (especially superplasticizers, such as polycarboxylate ethers (PCE)). Because these plasticizers are intercalated into the structure of the adsorbent clay, they can be effectively removed from mortar or concrete compositions produced using sand containing such clay. Consequently, the workability of mortar or concrete compositions with a given dosage of plasticizer is significantly reduced.

[0005] To identify adsorption problems in sand, the so-called "methylene blue (MB) test" is commonly used and described in standards (EN 933-9, ASTM 837-09). Methylene blue is a cationic dye with a strong affinity for negatively charged surfaces, particularly clay. This affinity is directly dependent on the clay content and properties of the clay in the sand. However, in practice, this indirect test has proven not always sufficiently specific to predict the adsorption of plasticizers such as PCE. Specifically, a high MB value may indicate the presence of expanded clay, but it can also be a false positive due to the presence of Fe-rich minerals. Furthermore, the absolute MB value that needs to be determined to determine whether sand is critical depends strongly on the sand's mineralogical composition. If the sand composition is unknown (very often), the MB value can be misleading. Typically, it is impossible to distinguish between PCE-adsorbed sand and water-adsorbed sand.

[0006] In this regard, WO 2020 / 109231 A1 (Chryso) describes a different method based on a special compound containing an MPEG-5,000 chain linked to a dye, whereby the PEG chain can be adsorbed by clay present in sand. Photometric measurements can then be performed to determine how much of the compound is adsorbed by the clay. Therefore, the proportion of adsorbed compound can be considered a measure of the clay concentration in the sand of interest. However, this is not a practical method, as it is not always sufficiently specific to predict the adsorption of plasticizers.

[0007] Furthermore, all known sand characterization methods to date share the commonality that they can only indicate whether sand may have high or low adsorption behavior. However, these methods typically only indicate adsorption behavior without distinguishing the type of adsorption. Specifically, most known methods generally cannot indicate, with sufficient precision, whether sand adsorbs plasticizers, mixed water, or both.

[0008] Therefore, new and improved solutions are needed to reduce or overcome the above-mentioned shortcomings. Summary of the Invention

[0009] One object of the present invention is to provide an improved method that allows characterization of sand in terms of the adsorption of plasticizers, particularly polycarboxylate-based additives. In particular, the method should allow differentiation between the adsorption of plasticizers and the adsorption of water. Preferably, the method should be as fast and simple as possible, and preferably allow direct measurement of the adsorption characteristics of the sand of interest to plasticizers and, more preferably, to water. Ideally, the method should also be applicable to predicting effective modifiers and / or mitigation strategies, which allow for the reliable and targeted mitigation of the negative effects of sand under real-world conditions, particularly in mineral binder compositions.

[0010] Surprisingly, it has been found that the problem of the present invention can be solved by the features of claim 1. Therefore, the core of the present invention is a method for characterizing sand in terms of the adsorption of plasticizers, preferably in terms of both the adsorption of plasticizers and water adsorption, the method comprising the following steps:

[0011] a) Provide an aqueous mixture of plasticizers having a defined concentration of plasticizers;

[0012] b) Determine the characteristics of the aqueous mixture, wherein the characteristics are related to the proportion of the plasticizer in the aqueous mixture;

[0013] c) Contact the sand sample to be analyzed with the aqueous mixture or a sample thereof, such that the sand sample is completely immersed in the aqueous mixture or a sample thereof;

[0014] d) Obtain a supernatant sample from the mixture in step c);

[0015] e) Determine that the supernatant sample has the same characteristics as in step b);

[0016] f) Compare the characteristics of the aqueous mixture or its sample obtained in step b) with the characteristics of the supernatant sample obtained in step e) to determine whether the characteristics differ from each other by more than a predetermined threshold.

[0017] In summary, in the method of this invention, a sand sample is mixed with a defined aqueous mixture of the plasticizer, and any potential adsorption of the plasticizer is identified by comparing the properties of the same or identical aqueous mixture of the plasticizer after interaction with the sand. In some implementations of this method, the method of this invention provides users with an inexpensive and rapid way to identify the adsorption potential of a given sand for a plasticizer, even without requiring large and expensive equipment. The method of this invention is more reliable than MB measurements because it is based on the direct interaction between the sand and the plasticizer under consideration. In particular, unlike MB tests or other known tests, the method of this invention is not based on indirect measurements but on a direct measurement of the adsorption properties of a given sand for an actual plasticizer.

[0018] The method of this invention allows for the direct identification of whether sand adsorbs plasticizers, particularly PCE. Furthermore, it can be used to effectively adjust the concentration of plasticizers and / or to select effective modifiers and / or moderating strategies, such as specific water-reducing PCEs and / or clay sealants, to optimize mortar or concrete properties with a given type of sand.

[0019] The solution of this invention proves to be far more robust than known approaches (e.g., the method proposed in WO 2020 / 109231 A1 (Chryso)). Without wishing to be bound by theory, this could be explained as follows: characterizing the adsorption behavior of a given sand using a PEG-terminated dye simulates, to some extent, the insertion of PCE with PEG side chains into expanded clay via these side chains. However, this approach overlooks the fact that PCE can adsorb onto positively charged surfaces via their anionic backbone, such as onto negatively charged clay or cement hydrates with a positive zeta potential due to a calcium adsorption layer. Therefore, the proportion of nonionic PEG chains adsorbed onto such surfaces may be smaller when compared to PCE.

[0020] Contrary to the approach described in WO 2020 / 109231 A1 (Chryso), the method of the present invention uses real plasticizers as test substances. Therefore, the adsorption behavior of a given sand is tested under conditions closer to real-world conditions, such as those present in a mineral binder composition.

[0021] Furthermore, the method of the present invention allows for the differentiation between the adsorption of plasticizers and the adsorption of mixed water. This is crucial because, for example, the adsorption of sand by pure water typically requires a different mitigation strategy than that for sand adsorbing the plasticizer itself. In particular, the method of the present invention allows for the provision of the correct mitigating agent and / or strategy for certain technical reasons of sand problems. Thus, it avoids the problem associated with non-expanding clays (which primarily cause adsorption of pure water), for example, sacrificial additives designed to inertize expanded clays to reduce PCE adsorption.

[0022] For example, if a mineral binder composition exhibits a high water demand, the present invention test using sand for the mineral binder composition directly indicates whether the high water demand is attributable to the adsorption of plasticizers. If the test is positive (i.e., the test indicates adsorption of plasticizers), the high water demand must be at least partially due to the adsorption of plasticizers. If the test is negative (i.e., the test indicates no adsorption of plasticizers), the adsorption of plasticizers can be ruled out, and the high water demand must be due to water adsorption. Therefore, depending on the test results, appropriate moderating agents and / or strategies can be selected in a targeted manner.

[0023] More specifically, using the method of the present invention, the negative impact of sand on mineral binder compositions, such as its negative impact on concrete performance, can be mitigated in a targeted manner by selecting appropriate types and amounts of mitigating agents and / or by selecting specific modified mitigation strategies, such as specifically modified additives for inertizing expansive or non-expansive clays. This contrasts sharply with known approaches, which typically do not allow for the identification of the causes of sand problems, making it impossible to select the most suitable mitigation measures.

[0024] Furthermore, the method of the present invention allows for the characterization of sand under conditions very close to or substantially the same as actual conditions, such as those in actual mineral binder compositions. Therefore, the effects of altering sand properties, such as high pH and / or a particular salt concentration, can be directly considered. This is highly advantageous because the adsorption behavior of a given sand can change significantly when conditions change. For example, stratification of clay contained in sand may lead to an increase in the exposed clay surface under cemented conditions. This, in turn, will affect the adsorption properties for plasticizers and / or water.

[0025] In addition, the test can be used to check whether a given sand exceeds the critical amount of fine particles (i.e., a grain size <125 μm, especially <63 μm, and especially <2 μm fine particles).

[0026] Other aspects of the invention are the subject of the other claims.

[0027] Method for implementing the present invention

[0028] A first aspect of the present invention relates to a method for characterizing sand in terms of the adsorption of plasticizers, preferably in terms of the adsorption of plasticizers and water adsorption, the method comprising the following steps:

[0029] a) Provide an aqueous mixture of plasticizers having a defined concentration of plasticizers;

[0030] b) Determine the characteristics of the aqueous mixture, wherein the characteristics are related to the proportion of the plasticizer in the aqueous mixture;

[0031] c) Contact the sand sample to be analyzed with the aqueous mixture or a sample thereof, such that the sand sample is completely immersed in the aqueous mixture or a sample thereof;

[0032] d) Obtain a supernatant sample from the mixture in step c);

[0033] e) Determine that the supernatant sample has the same characteristics as in step b);

[0034] f) Compare the characteristics of the aqueous mixture or its sample obtained in step b) with the characteristics of the supernatant sample obtained in step e) to determine whether the characteristics differ from each other by more than a predetermined threshold.

[0035] Specifically, a "plasticizer aqueous mixture" is a mixture comprising water, a plasticizer, and optionally one or more other components. Specifically, water is the dominant liquid component of the aqueous mixture or the component having the highest weight proportion among all liquid components in the mixture. Specifically, the aqueous mixture provided in step a) is an aqueous mixture consisting of water and a plasticizer. However, an aqueous mixture consisting, for example, of water, a plasticizer, and one or more salts can be provided.

[0036] "Characteristic" means the physical and / or chemical properties or characteristics of an aqueous mixture. The characteristic depends on the proportion of the plasticizer in the aqueous mixture. For example, a characteristic may be the concentration of the plasticizer itself, the effect of the aqueous mixture and / or the plasticizer on its interaction with other substances, and / or a characteristic may be a measurable chemical and / or physical parameter of the aqueous mixture that depends on the proportion of the plasticizer.

[0037] Specifically, the characteristic is the rheological parameters of the aqueous slurry of a sample containing an aqueous mixture of plasticizers and mineral binders (particularly cement), and / or the characteristic is the total organic matter content of the aqueous mixture of plasticizers. Thus, for example, the rheological parameter is slump flow. Other examples of rheological parameters are described below.

[0038] The term "adsorption of plasticizers" includes the adsorption of any kind of plasticizer by sand. In particular, adsorption refers to the adsorption of plasticizers, especially PCE, by clay, particularly expanded clay.

[0039] According to the present invention, a "plasticizing additive" is an additive used in mineral binder compositions that improves the processability of the mineral binder compositions. In particular, the plasticizing additive is a plasticizer, fluidizing agent, and / or dispersant, especially a superplasticizer.

[0040] Specifically, the plasticizer is a superplasticizer, particularly a copolymer comprising a polymer backbone and side chains bonded thereto. Specifically, the copolymer is a polycarboxylate ether (PCE) having a polycarboxylate backbone and polyether side chains, wherein the polyether side chains are preferably bonded to the polycarboxylate backbone via ester, ether, and / or amide groups.

[0041] Specifically, the copolymer comprises a monomer unit M1 with an acid group and a monomer unit M2 with a side chain. Preferably, the monomer unit M1 with an acid group includes a carboxylic acid group, a sulfonic acid group, a phosphate group, and / or a phosphonic acid group.

[0042] In particular, the monomer unit M2 with side chains includes polyoxyalkylene side chains, especially polyoxyethylene and / or polyoxypropylene side chains.

[0043] More specifically, the monomer unit M1 with the acid group has the structure of formula I:

[0044]

[0045] The monomer unit M2 with side chains preferably has the structure of Formula II:

[0046]

[0047] in:

[0048] R 1 Independently in each case are -COOM, -SO2-OM, -O-PO(OM)2, and / or -PO(OM)2.

[0049] R 2 R 3 R 5 and R 6 In each case, it is independently H or an alkyl group containing 1-5 carbon atoms.

[0050] R 4 and R 7 In each case, it is independently H, -COOM, or an alkyl group containing 1-5 carbon atoms, or wherein R 1 With R 4Together they form a ring to obtain -CO-O-CO-,

[0051] M represents H independently of each other. + Alkali metal ions, alkaline earth metal ions, divalent or trivalent metal ions, ammonium ions or organic ammonium groups;

[0052] m = 0, 1, or 2

[0053] p = 0 or 1

[0054] X is independently -O- or -NH- in each case.

[0055] R 8 It is a formula - [AO] n -R a The group, wherein A = C2- to C4-alkylene, R a H, Cl- to C 20 -alkyl, -cycloalkyl or -alkylaryl, and n = 2-250, especially 10-200.

[0056] Other monomers may also be present in copolymers.

[0057] Specifically, in step a), the concentration of the plasticizer is 0.0001-10% by weight, particularly 0.001-7% by weight, for example 0.01-5% by weight, particularly 0.1-2% by weight, relative to the total weight of water and plasticizer.

[0058] Specifically, in step a), an aqueous mixture with a pH of 11-14, particularly 12-13.5, and especially 12.5-13.5, is prepared. An aqueous mixture having this pH best reflects the conditions present in mortar or concrete compositions in which plasticizing additives are typically used.

[0059] In step b), the determination of features is specifically performed in order to obtain reference values.

[0060] Specifically, in step c), the weight ratio of the aqueous mixture or its sample to the sand sample is 1-10, especially 1-5, particularly 1.5-4.

[0061] Preferably, the sand is dried before contacting the sand to be analyzed with the aqueous mixture or a sample thereof. Drying the sand eliminates the possibility of altering the water concentration in the aqueous mixture due to changes in moisture content. Drying can be carried out, for example, in an oven at temperatures of 30-90°C, particularly 50-70°C. These temperatures are particularly helpful in preventing the formation of fine sand particle agglomerations, which can occur at temperatures above 100°C.

[0062] Preferably, in step c), the sand sample is mixed with the aqueous mixture or a sample thereof for a predetermined time period, for example, 30 seconds to 2 hours. Preferably, mixing is performed by stirring, shaking, and / or vibration. This ensures uniform mixing. Stirring can be performed at 800-1,000 rpm, while vibration or shaking can be performed at 50-400 rpm.

[0063] The aqueous mixture or its sample used in step c) may be the aqueous mixture or its sample used in step a) and / or may be an aqueous mixture or its sample with the same composition.

[0064] Specifically, in step c), the aqueous mixture or a sample thereof is gradually brought into contact with the sand sample to be analyzed. Specifically, a first portion of water or the aqueous mixture or a sample thereof is brought into contact with the sand sample, particularly mixed, followed by the addition of a second portion of water or the aqueous mixture or a sample thereof. This helps to obtain a highly homogeneous mixture in step c). Specifically, the plasticizer is added separately from the first and second portions, or the plasticizer is added as a component of the second portion.

[0065] For example, a first portion consisting of water is added, followed by the addition of plasticizers, and then a second portion of water. Therefore, the total ratio of water to plasticizers corresponds to the aqueous mixture in step a).

[0066] In another example, a first portion consisting of water is added, followed by a second portion of water containing plasticizers. Therefore, the total ratio of water to plasticizers corresponds to the aqueous mixture in step a).

[0067] Specifically, during and / or after step d), any unwanted components may be removed from the mixture of step c) and / or from the supernatant sample. Unwanted components may be appropriately identified substances that affect the characteristics described in step e).

[0068] Specifically, during and / or after step d), fine particles, particularly those <125 μm, <63 μm, and <2 μm in size, are removed from the supernatant sample. This removal is particularly achieved by filtration and / or centrifugation, especially by filtration. Centrifugation can be performed at 3,000–5,000 rpm, particularly for 5–10 minutes.

[0069] As the results show, in some applications, fine particles can affect the determination of characteristics. Therefore, obtaining a supernatant sample free of fine particles may be helpful in properly determining the adsorption properties of sand. However, for other applications, fine particles may not be a problem, and in such cases, particle removal is not necessary.

[0070] In step e), the determination of characteristics is specifically performed in order to obtain the measured values.

[0071] Specifically, when comparing features in step f), the reference value obtained in step b) is compared with the measured value obtained in step e), for example by subtracting the measured value from the reference value.

[0072] For example, the predetermined threshold in step f) corresponds to a predetermined proportion of the feature or reference value obtained in step b). In particular, the threshold in step f) is equal to 20%, especially 10%, especially 5%, and very especially 4% of the feature or reference value obtained in step b).

[0073] If the characteristics differ from each other by more than a predetermined threshold in step f), then the sand sample has already adsorbed a certain proportion of plasticizer in step c). Therefore, the concentration of plasticizer in the supernatant sample is lower than the concentration of plasticizer in the original aqueous mixture provided in step a). Thus, it can be concluded that the given sand is problematic in terms of plasticizer adsorption. If this sand is used in mortar or concrete compositions, appropriate mitigation strategies are needed, such as by adding a moderating agent.

[0074] "Moderators" are substances that can reduce the undesirable effects of sand (such as the adsorption effects of sand). In particular, moderators are different from plasticizers.

[0075] Specifically, the moderating agent is a clay blocker, such as polycarboxylate ethers, nonionic comb polymers, lignin sulfonates, sulfonated naphthalene condensates, sulfonated melamine condensates, polycationic, cationic amines, polyethylene oxide (PEG, mPEG), vinyl copolymers, homopolymers or copolymers of polycarboxylic acids (e.g., acrylic acid, methacrylic acid, maleic acid and / or picolinic acid), carbohydrates (e.g., gluconates, glucose, corn syrup, sugar, molasses, caramel coloring, oligosaccharide or cellulose derivatives, cyclodextrin).

[0076] Specifically, the nonionic comb is a comb polymer as described in WO 2020 / 070095 A1, page 32, line 15 to page 33, line 4.

[0077] Furthermore, if the characteristics differ from each other by less than a predetermined threshold in step f), then no significant adsorption of the plasticizer occurs in step c). Therefore, it can be concluded that the given sand has no problem with the adsorption of the plasticizer.

[0078] This information can be used directly to determine whether a mortar or concrete composition with a given sand requires special treatment, such as the use of a moderating agent.

[0079] Preferably, if the comparison in step f) shows that the characteristics of the aqueous mixture or its sample differ from the characteristics of the supernatant sample by more than a given threshold, then steps c) to f) are repeated, thereby using different aqueous mixtures containing plasticizers of varying concentrations and / or tempering agents of defined concentrations in step c).

[0080] Preferably, the process is repeated until the comparison in step f) shows that the characteristics of the aqueous mixture or its sample and the characteristics of the supernatant sample differ from each other by less than a given threshold.

[0081] In other words, it is preferable to repeat steps c) to f) until the comparison in step f) shows that the characteristics of the aqueous mixture or its sample and the characteristics of the supernatant sample differ from each other by less than a given threshold, thereby changing the concentration of the plasticizer and / or the type and / or concentration of the modifier in each repetition.

[0082] According to another preferred embodiment, the method of the present invention further includes an additional step a'). The additional step a') includes the following sub-steps:

[0083] (i) Determine the water requirement of the mineral binder composition containing the sand to be analyzed and the plasticizer additive;

[0084] (ii) The water requirement determined in sub-step (i) is compared with the standard water requirement of the given mineral binder composition.

[0085] Water requirement refers to the proportion of water required to obtain a given mineral binder composition with predetermined rheological parameters, particularly predetermined viscosity and / or flow rate.

[0086] Standard water requirement is the water requirement of a given mineral binder composition produced using standardized sand, rather than the sand to be analyzed. The standardized sand is preferably pure sand, which in particular has low water absorption.

[0087] Therefore, the mineral binder composition used to determine the standard water requirement in step (ii) comprises the same type and proportion of mineral binder and plasticizer additive as the mineral binder composition used in step (i), and the same proportion of sand. Specifically, except for the different sand, the mineral binder composition used to determine the standard water requirement is the same as the mineral binder composition used in step (i).

[0088] In principle, the additional step a') can be performed at any time before, during, or after the other steps of the method of the present invention. Preferably, step a') is performed before step a).

[0089] If the comparison in step (ii) shows that the water requirement determined in sub-step (i) is higher than the standard water requirement, especially higher than 105% of the standard water requirement, and especially higher than 120%, then the sand-adsorbed water and / or plasticizer to be analyzed is known.

[0090] If step a') shows a high water demand and step f) shows that the characteristics differ from each other by more than a predetermined threshold on the first execution, it can be concluded that the plasticizer is adsorbed by the given sand.

[0091] If step a') shows a high water demand and step f) shows that the features do not differ from each other by a predetermined threshold on the first execution, it can be concluded that the plasticizer is not adsorbed, but water adsorbs sand.

[0092] Therefore, step a') allows for the determination of whether a sand-related problem fundamentally exists. If so, the result of step a') can be directly used to distinguish the type of adsorption problem for a given sand. This is particularly helpful if there is a high water demand but no adsorption of plasticizers, because it can then be concluded that the sand must be adsorbing water. Therefore, appropriate modifiers and / or strategies can be selected in a targeted manner.

[0093] According to another aspect of the invention, the method of the invention includes the step of providing an admixture for preparing a mineral binder composition, wherein the admixture comprises plasticizing additives and / or modifiers in proportions obtained by the method of the invention, particularly as in the last repetition of steps c) to f) as described above and / or as in step a').

[0094] According to the preferred execution method, the method of the present invention is carried out as follows:

[0095] - In step b), a sample comprising the aqueous mixture of step a) and an aqueous slurry of a defined proportion of a mineral binder, particularly cement, is prepared, wherein water and mineral binder have a given ratio (w / c); and the rheological parameters of the aqueous slurry, particularly slump flow, are determined as characteristics of the sample of the aqueous mixture; and

[0096] - In step e), another aqueous slurry is prepared using the same mineral binder as in step b) and an upper clear liquid as water, wherein the ratio of water or upper clear liquid to mineral binder is the same as in step b), and the same rheological parameters as in step b), particularly slump flow, are determined to be characteristic of the upper clear liquid sample.

[0097] Specifically, the rheological parameters are selected from viscosity, pour point, yield point, slump flow, flow table test, slump, slump flow spread, flow time, flow velocity, V-funnel test, and / or downward flow time. Preferably, slump flow is used as the rheological parameter. Slump flow can be evaluated according to EN 12350-8:2019 or similar methods.

[0098] Therefore, in this implementation, the method of the present invention is a phenomenological test based on a comparison of rheological parameters (particularly slump flow) between cement using only a specific dosage of plasticizer and an aqueous mixture containing the plasticizer after interaction with a given sand. In other words, any potential adsorption of the plasticizer is identified by mixing a sand sample with a defined aqueous mixture containing the plasticizer and using the same mixture after interaction with the sand in a cement slurry test.

[0099] The significant changes in rheological parameters between the two cement slurry tests, particularly the reduction in slump flow, indicate the presence of materials adsorbing plasticizers within the sand.

[0100] Therefore, preferably, the concentration of the plasticizer in step a) is selected to achieve the predetermined rheological parameters, particularly the predetermined slump flow, of the slurry produced in step b) with a predetermined ratio of mineral binder and a predetermined ratio (w / c) of water and hydraulic binder.

[0101] Specifically, rheological parameters, particularly slump flow, are defined as 12-18 cm, particularly 13-16 cm, particularly 14 cm, and the water-to-cement ratio (w / c) is selected from 0.28-0.5, particularly 0.3-0.4, particularly 0.35. Therefore, slump flow is specifically determined according to EN 12350-8:2019 using a miniature cone having a height of 58 mm, a lower inner diameter of 38 mm, and an upper inner diameter of 19 mm.

[0102] The term "mineral binder" means, for example, a binder that reacts in the presence of water during a hydration reaction to form a solid hydrate or hydrate phase. This can be, for example, a hydraulic binder (e.g., cement or hydraulic lime), a latent hydraulic binder (e.g., slag), a pozzolanic binder (e.g., fly ash), or a non-hydraulic binder (gypsum or calcium lime). The term "cement binder" or "cement binder composition" herein means, for example, a binder or binder composition having, for example, a proportion of at least 5% by weight, for example, at least 20% by weight, for example, at least 35% by weight, for example, at least 65% by weight of cement clinker. Cement clinker can be a Portland cementclinke. In the context of this invention, cement clinker can mean milled cement clinker.

[0103] For example, mineral binders contain hydraulic binders, such as cement. Cement with a clinker ratio of ≥35% by weight can be used.

[0104] For example, the cement is CEM I, CEM II, CEM III, CEM IV or CEM V Portland cement (according to standard EN197-1), calcium aluminate cement (according to standard EN 14647:2006-01) and / or calcium sulfoaluminate (CSA) cement.

[0105] Portland cement described in alternative standards (e.g., ASTM standards or Chinese standards) is equally suitable. According to a preferred embodiment, the Portland cement has a CEM I type. According to an embodiment, the Portland clinker content in the Portland cement of the present invention is at least 35% by weight, preferably at least 65% by weight, particularly at least 95% by weight, each based on the total dry weight of the cement. According to an embodiment, the aluminum content (expressed as Al2O3) of the Portland cement clinker is less than 10% by weight, preferably less than 8% by weight, more preferably less than 6% by weight, in each case relative to the total dry weight of the clinker. According to a particularly preferred embodiment, the Blaine surface of the Portland cement, measured according to standard EN 196-6:2010, is 1,500-10,000 cm². 2 / g, preferably 2'000-9'000cm 2 / g, especially 3'000-7'000cm 2 / g. Preferably, the sulfate content of the Portland cement of the present invention is optimized to an SO3 content of no more than 4.0% by weight relative to the total dry weight of the cement.

[0106] Preferably, in the context of this invention, CSA cement is cement having a composition of C4(A) 3-x F xCement with a main phase composed of 3(4CaO·3-xAl2O3·xFe2O3·CaSO4), where x is an integer from 0 to 3.

[0107] The proportion of the hydraulic binder in the entire mineral binder can be at least 5% by weight, for example at least 20% by weight, for example at least 35% by weight, for example at least 65% by weight. According to an exemplary embodiment, the mineral binder consists of at least 95% by weight of hydraulic binder (e.g., cement clinker).

[0108] The binder or binder composition may contain or consist of other binders. These are, for example, latent hydraulic binders and / or setting binders. Suitable latent hydraulic and / or setting binders are, for example, slag, fly ash, and / or silica dust. Similarly, the binder composition may contain inert substances such as limestone, quartz powder, and / or pigments. In one exemplary embodiment, the mineral binder contains 5-95% by weight, for example 5-65% by weight, for example 15-35% by weight of latent hydraulic and / or setting binders. Advantageous latent hydraulic and / or setting binders are slag and / or fly ash.

[0109] In one exemplary embodiment, the mineral binder contains a hydraulic binder, particularly cement or cement clinker, and a potential hydraulic and / or setting binder, preferably slag and / or fly ash. Here, the proportion of the potential hydraulic and / or setting binder can be 5-65% by weight, for example 15-35% by weight, with at least 35% by weight, for example at least 65% by weight, of the hydraulic binder.

[0110] In particular, the mineral binder used in the method of the present invention is a cement binder, especially cement, preferably Portland cement. However, other binders may be suitable depending on the specific circumstances.

[0111] Specifically, the mineral binder is a mineral binder composition B comprising calcined clay, limestone, and Portland cement. Throughout this invention, the term "clay" refers to a solid material, each comprising at least 30% by weight, preferably at least 35% by weight, and especially at least 75% by weight, clay minerals relative to its dry weight. Calcined clay (CC) is a clay material that has undergone heat treatment, preferably at a temperature of 500-900°C, or a rapid calcination process at a temperature of 800-1100°C. Suitable rapid calcination processes are described, for example, in WO 2014 / 085538. Calcined clay is an anhydrous material. According to embodiments, calcined clay is produced by heat treatment separately from the other components of binder composition B, particularly separately from present Portland cement and / or other hardening and / or potential hydraulic materials. In the context of this invention, it is preferred that during clay calcination, the clay material is dehydroxylated into an amorphous material while preventing the formation of crystalline high-temperature aluminosilicate phases such as mullite. Calcinated clay, particularly calcined kaolin, is typically amorphous, has a significantly higher specific surface area compared to virgin clay, and exhibits hardening activity. According to a particularly preferred embodiment of the invention, the calcined clay is metakaolin. Metakaolin is a material produced by calcining kaolinite or kaolinite-rich minerals, for example, having a kaolinite content of at least 30% by weight, preferably at least 35% by weight, relative to its dry weight. The calcination temperature used to produce metakaolin is typically in the range of 500-900°C.

[0112] According to the implementation plan, the calcined clay is ground into a powder having at least 0.5% by weight, preferably at least 2% by weight, even more preferably at least 10% by weight, and especially at least 20% by weight of a 45μm residue as measured according to ASTM C 430-96 (2003).

[0113] In a preferred embodiment of the invention, the chemical composition of limestone (L) and Portland cement (P) is as defined in standard EN197-1:2011. Alternatively, limestone (L) may also represent magnesium carbonate, dolomite, and / or mixtures of magnesium carbonate, dolomite, and / or calcium carbonate. Particularly preferred is that the limestone (L) in the context of this invention is naturally occurring limestone, primarily composed of calcium carbonate (typically calcite and / or aragonite), but typically also containing some magnesium carbonate and / or dolomite. Limestone (L) may also be naturally occurring marl.

[0114] In the context of this invention, limestone (L) is an untreated abrasive material. Specifically, the limestone is not decarburized. According to embodiments, the Brønsted surface area of ​​the limestone is 3,000-15,000 cm². 2 / g.

[0115] Blaine surface is measured as described in standard EN 196-6:20 10.

[0116] According to an embodiment, the binder composition B of the present invention comprises calcined clay (CC), limestone (L), and Portland cement (P) in the following weight ratios:

[0117] The P:CC ratio is 33:1 to 1:1, preferably 8:1 to 1:1.

[0118] The CC:L ratio is 10:1 to 1:33, preferably 5:1 to 1:10.

[0119] The P:L ratio is 20:1 to 1:4, preferably 5:1 to 1:1.

[0120] According to the embodiments, in each case, the binder composition B of the present invention consists of at least 65% by weight, preferably at least 80% by weight, and more preferably at least 92% by weight of calcined clay, limestone and Portland cement relative to the total dry weight of the composition.

[0121] According to an embodiment of the present invention, adhesive composition B comprises a mixture of the following substances:

[0122] a) 25–100 parts by weight of Portland cement (P),

[0123] b) 3–50 parts by weight of calcined clay (CC), especially metakaolin.

[0124] c) 5–100 parts by weight of limestone (L).

[0125] Specifically, in this binder composition B, the mass ratios of calcined clay (CC), limestone (L), and Portland cement (P) are as follows:

[0126] The P:CC ratio is 33:1 to 1:1, preferably 8:1 to 1:1.

[0127] The CC:L ratio is 10:1 to 1:33, preferably 5:1 to 1:10.

[0128] The P:L ratio is 20:1 to 1:4, preferably 5:1 to 1:1.

[0129] According to a specific embodiment of the present invention, the adhesive composition B consists of a mixture of the following substances:

[0130] a) 50 parts by weight of Portland cement (P),

[0131] b) 20–50 parts by weight of calcined clay (CC), especially metakaolin,

[0132] c) 10–50 parts by weight of limestone (L).

[0133] Specifically, relative to the total dry weight of the binder composition B, the binder composition B of the present invention does indeed contain no more than 5% by weight, preferably no more than 2% by weight, of calcium aluminate cement and / or calcium sulfoaluminate cement according to EN 14647. In particular, the content of Portland cement in the binder composition B of the present invention is higher than the content of calcium aluminate cement and / or calcium sulfoaluminate cement.

[0134] According to the embodiments, the binder composition B of the present invention further comprises 1-8% by weight of calcium sulfate relative to the total dry weight of the composition. The binder composition B of the present invention does not contain calcium sulfate as a primary binder. Calcium sulfate may be in the form of gypsum, calcium sulfate dihydrate, calcium sulfate hemihydrate (α or β form), and / or anhydrous gypsum.

[0135] According to embodiments, the binder composition B of the present invention further comprises other potential hydraulic and / or hardening materials. Suitable other potential hydraulic and / or hardening materials are, for example, volcanic rock, pumice, glass powder, diatomaceous earth, calcined silica, precipitated silica, slag, fly ash, silica fume, and / or calcined slate. According to some embodiments, the binder composition B comprises up to 20% by weight, preferably up to 5% by weight, of other potential hydraulic and / or hardening materials, in each case relative to the total dry weight of the composition.

[0136] Therefore, a suitable binder composition B of the present invention may consist of at least 65% by weight, preferably at least 80% by weight, more preferably at least 92% by weight, calcined clay (CC), limestone (L) and Portland cement (P) and 1-8% by weight, relative to the total dry weight of the composition in each case, wherein the weight ratio of P:CC is 33:1 to 1:1, preferably 8:1 to 1:1, CC:L is 10:1 to 1:33, preferably 5:1 to 1:10, and P:L is 20:1 to 1:4, preferably 5:1 to 1:1.

[0137] According to an embodiment of the present invention, the adhesive composition B is a mixture of 92-99% by weight of the following substances:

[0138] a) 25–100 parts by weight of Portland cement (P),

[0139] b) 3–50 parts by weight of calcined clay (CC), especially metakaolin.

[0140] c) Composed of 5–100 parts by weight of limestone (L) and 1–8% by weight of calcium sulfate, relative to the total dry weight of binder composition B.

[0141] According to one specific embodiment of the invention, the adhesive composition B is a mixture of 92-99% by weight of the following substances:

[0142] a) 50 parts by weight of Portland cement (P),

[0143] b) 20–50 parts by weight of calcined clay (CC), especially metakaolin,

[0144] c) Composed of 10–50 parts by weight of limestone (L) and 1–8% by weight of calcium sulfate, relative to the total dry weight of binder composition B.

[0145] Specifically, in this binder composition B, the mass ratios of calcined clay (CC), limestone (L), and Portland cement (P) are as follows:

[0146] The P:CC ratio is 33:1 to 1:1, preferably 8:1 to 1:1.

[0147] The CC:L ratio is 10:1 to 1:33, preferably 5:1 to 1:10.

[0148] The P:L ratio is 20:1 to 1:4, preferably 5:1 to 1:1.

[0149] According to a preferred embodiment, the adhesive composition B is a mixture of 92-99% by weight of the following substances:

[0150] a) 25–100 parts by weight of Portland cement (P),

[0151] b) 3–50 parts by weight of calcined clay (CC), especially metakaolin.

[0152] c) Composed of 5–100 parts by weight of limestone (L) and 1–8% by weight of calcium sulfate, relative to the total dry weight of binder composition B.

[0153] In particular, this binder composition B contains no other potential hydraulic and / or hardening materials, especially no volcanic rock, pumice, glass powder, diatomaceous earth, calcined silica, precipitated silica, slag, fly ash, silica powder and / or sintered slate.

[0154] The binder composition B of the present invention can be obtained by blending the components in dry form. Suitable blending methods are known to those skilled in the art. In particular, the binder composition B of the present invention can be obtained by blending calcined clay, limestone, and optionally calcium sulfate, and then blending the mixture with Portland cement. However, other blending sequences are also possible. Two or more components of the binder composition B can also be ground together. However, in the context of the present invention, it is preferred to grind the calcined clay separately from the other components. According to a particularly preferred embodiment, the binder composition B of the present invention is obtained by blending the components in dry form. In the context of the present invention, it is particularly impossible to prepare the binder composition B by mixing the components and then subjecting it to a heat treatment or curing process. Therefore, for example, it is impossible to prepare the binder composition B of the present invention by mixing calcined clay, limestone, optionally calcium sulfate, and Portland cement, and then heating the resulting mixture, particularly in a kiln, to a temperature greater than 150°C.

[0155] It is worth noting that this invention also allows for the identification of binders that are best compatible with a given sand. Therefore, the method of this invention can be carried out with different types of mineral binders.

[0156] Preferably, in this first mode of execution, in step c), the weight ratio of the aqueous mixture or its sample to the sand sample is 1-10, especially 1-2, particularly 1.5.

[0157] In general, the first-highest preferred execution method is beneficial because it is very simple and easy to implement.

[0158] Specifically, no special equipment and / or indicators (methylene blue dye, PEG-terminated dye) are required. In particular, no burette / stirrer (required for MB testing) and photometer (required or frequently used for MB testing in the pathway described in WO 2020 / 109231 A1) are required.

[0159] Furthermore, the method allows for the direct differentiation between the adsorption of plasticizers and water adsorption. Specifically, all types of PCE adsorption are considered, such as adsorption via side chains or via the main chain, adsorption to the inner and outer surfaces of minerals, and complexation. Additionally, the results are unaffected by either oxidizing or reducing conditions when compared to MB testing.

[0160] In addition, the test allows for the acquisition of additional information regarding the fine particle content (see below).

[0161] Therefore, the achievable results are highly deterministic, similar to TOC measurements (see the second highly preferred implementation below), and allow for the appropriate selection of moderating agents and / or strategies.

[0162] In a second highly preferred embodiment of the method according to the invention, in steps b) and e), the total organic matter content of the aqueous mixture and / or the supernatant sample is determined as a characteristic.

[0163] The determination of total organic matter (TOC) is a known technique. Therefore, the sample is first oxidized, selectively converting all carbon atoms in the sample into carbon dioxide (CO2). The resulting CO2 is then transferred via a carrier gas flow (usually synthetic air or oxygen) to a detector, particularly an NDIR (non-dispersive infrared) detector, where it is quantitatively measured. Various commercially available measuring devices are available for determining TOC.

[0164] Specifically, in step b), the total organic matter content is determined by measuring the total organic matter content of the aqueous mixture provided in step a), and in step e), the total organic matter content is determined by measuring the total organic matter content of the supernatant sample obtained in step d). Therefore, preferably, the measurement method in step b) is the same as that in step e). This allows for highly accurate characterization because any known and unknown side effects are automatically considered. This is not the case if, for example, in step b), the concentration is relied upon by pure calculation. Specifically, in step f), the characteristics of the aqueous mixture or sample obtained in step b) are compared with the characteristics of the supernatant sample in step e), including the step of calculating the difference between the total organic matter content measured in step b) and the total organic matter content measured in step e).

[0165] For example, the difference obtained therefrom is then compared with a predetermined threshold, which, in particular, corresponds to a predetermined proportion of the total organic matter content measured in step b). Specifically, the threshold is equal to 20%, especially 10%, especially 5%, and very especially 4% of the total organic matter content measured in step b).

[0166] Specifically, measuring the total organic matter content in step b) includes the following steps: (i) oxidizing the aqueous mixture provided in step a) such that all carbon atoms contained in the sample are converted into carbon dioxide (CO2), (ii) transferring the formed CO2 to a detector, particularly an NDIR (non-dispersive infrared) detector, via a carrier gas flow (especially synthetic air or oxygen), and (iii) quantitatively measuring the CO2.

[0167] Similarly, in particular, measuring the total organic matter content in step e) includes the following steps: (i) oxidizing the supernatant sample taken in step d) such that all carbon atoms contained in the sample are converted into carbon dioxide (CO2), (ii) transferring the formed CO2 to a detector, particularly an NDIR (non-dispersive infrared) detector, by means of a carrier gas flow (especially synthetic air or oxygen), and (iii) quantitatively measuring the CO2.

[0168] Synthetic air refers to a mixture of nitrogen and oxygen, particularly 75-85% by volume, e.g., 80% by volume nitrogen, and 15-25% by volume, e.g., 20% by volume oxygen. Synthetic air has proven to be highly advantageous for this application. This is likely because conventional ambient air contains numerous impurities that can affect the accurate determination of CO2 content.

[0169] Preferably, in this embodiment, the aqueous mixture in step a) is prepared with sulfate and / or hydroxide salts, particularly calcium sulfate, sodium sulfate, potassium sulfate, potassium hydroxide, calcium hydroxide, and / or sodium hydroxide, and has a pH as described above. This aqueous mixture reflects the conditions present in the mortar or concrete composition in which plasticizing additives are typically used.

[0170] Preferably, in this manner of execution, in step c), the weight ratio of the aqueous mixture or its sample to the sand sample is 1-10, especially 2-5, particularly 3-4.

[0171] In the second highly preferred implementation, the significant reduction in total organic matter content between step b) and step e) indicates the presence of material adsorbing plasticizers in the sand.

[0172] In another preferred embodiment of the method of the present invention, in addition to the given adsorption properties of the sand, it can also be checked whether the fine particle content of the sand may also cause problems.

[0173] This is possible because the potential presence of fine particles can be observed during steps c) and d), as they are suspended in the supernatant. Although the determination of fine particles using the method of the present invention cannot replace dry sieving, additional and important information about the fine particles can be obtained. In particular, fine particles adhering to larger aggregates and not detected during dry sieving will separate from the larger aggregates in step d), and thus can be qualitatively measured.

[0174] Therefore, in step d), a crude sample from the supernatant of the aqueous mixture and a purified sample are obtained, which are free of suspended fine particles with a particle size <125 μm, particularly <63 μm, and particularly <2 μm, from the supernatant. Specifically, the purified sample is obtained by filtration and / or centrifugation, particularly by filtration.

[0175] Then, in step e), the characteristics of the crude sample and the purified sample are determined separately and compared separately with the characteristics of the aqueous mixture sample from step b). From this comparison, the following information can be obtained:

[0176] If the characteristics of both the crude and purified samples determined in step e) differ from those of the aqueous mixture sample from step b) by more than a given threshold, it can be concluded that the given sand is problematic in terms of plasticizer adsorption. If such sand is used in mortar or concrete compositions, appropriate mitigation strategies are needed, such as by adding a mitigator to compensate for plasticizer adsorption. In this case, preferably, an additive that compensates for plasticizer adsorption is selected as a mitigator and / or the dosage of the plasticizer is adjusted.

[0177] If the characteristics of the coarse sample differ from those of the aqueous mixture sample from step b) by more than a given threshold, and the characteristics of the purified sample differ from those of the aqueous mixture sample from step b) by less than a given threshold, it can be concluded that the given sand is problematic in terms of fine particle content. If this sand is used in mortar or concrete compositions, appropriate mitigation strategies are needed, such as by adding a moderator to compensate for the high fine particle content and / or by taking other measures to address the high fine particle content, such as optimizing the mixing design. In particular, in this case, an additive to compensate for the high fine particle content is selected as the moderator.

[0178] - If the characteristics of the crude sample and the purified sample are all less than a given threshold different from the characteristics of the aqueous mixture sample of step b), it can be concluded that the sand has no problem with plasticizer adsorption and fine particle content in terms of plasticizer additives.

[0179] Generally, "high fine particle content" or "fine particle problem" specifically refers to the situation where the sand to be analyzed contains fine particles, which affects the rheology of the mineral binder composition containing said sand. In particular, high fine particle content means the following: the characteristics of the coarse sample determined in step e) differ from the characteristics of the aqueous mixture sample in step b) by more than a predetermined threshold, and the characteristics of the purified sample determined in step e) differ from the characteristics of the aqueous mixture sample in step b) by less than a predetermined threshold.

[0180] Preferably, if the comparison in step f) shows that the characteristics of the crude sample and / or purified sample differ from the characteristics of the aqueous mixture or its sample by more than a given threshold, then steps c) to f) are repeated, thereby using different aqueous mixtures containing plasticizers of varying concentrations and / or modifiers of defined concentrations in step c).

[0181] Specifically, repeat steps c) to f) until the comparison in step f) shows that the characteristics of the crude sample and the purified sample, as well as the characteristics of the aqueous mixture or a sample thereof, differ from each other by less than a given threshold.

[0182] If the given sand is used in a mortar or concrete composition, this allows for finding the optimal concentration of plasticizer and / or suitable modifier. Furthermore, the present invention relates to a method for preparing a mineral binder composition, wherein an admixture is provided as described above and mixed with water, a mineral binder, sand used in the method of the invention, and, unnecessarily, other aggregates. Therefore, the admixture preferably comprises plasticizer and / or modifier in proportions obtained by the method of the invention, particularly as in the last repetition of steps c) to f) as described above.

[0183] In another embodiment, the method of the present invention relates to a method for preparing a mineral binder, comprising the steps of: (i) characterizing sand in terms of adsorption of plasticizers using the method of the present invention described above, and (ii) mixing the sand used in step (i) with the additives used in step (i), the mineral binder, water, optional other aggregates, and optional modifiers. Therefore, preferably, the plasticizers and / or modifiers are present in proportions obtained by the method of the present invention, particularly as in the last repetition of steps c) to f) as described above.

[0184] Specifically, the features identified in step (i) are rheological parameters, particularly collapse flow, and / or the total organic matter content.

[0185] Specifically, the method of the present invention includes the step of providing a mineral binder composition comprising sand of the type used in the method of the present invention, and optionally, other aggregates, and:

[0186] - A moderating agent for compensating for the adsorption of plasticizers, if step f) during the first execution shows that the characteristics of steps b) and e) differ from each other by more than a predetermined threshold, then preferably, the plasticizers and / or moderating agents are used in proportions obtained by the above method, especially in proportions obtained in the last repetition of steps c) to f) above.

[0187] - If step a') shows a high water demand and step f) shows that the characteristics of steps b) and e) do not differ from each other by more than a predetermined threshold on the first execution, then add a moderating agent to compensate for water adsorption.

[0188] -Optionally, if the first execution of step f) shows that, when the crude sample and purified sample are obtained as described above in step d), the characteristics of the crude sample differ from the characteristics of the aqueous mixture sample of step b) by more than a predetermined threshold, and the characteristics of the purified sample differ from the characteristics of the aqueous mixture sample of step b) by less than a predetermined threshold, then a moderating agent for compensating for high fineness and / or measures to address high fineness, such as adjusting the mixing design of the mineral binder composition, are used:

[0189] -Unnecessarily, a moderating agent for compensating for the adsorption of plasticizer additives, particularly as described above, and a moderating agent for compensating for high particle size and / or for measures to deal with high particle size, particularly as described above; if step f) during the first execution shows that, when the crude sample and the purified sample are obtained as described above in step d), the difference between the characteristics of both the crude sample and the purified sample and the characteristics of the aqueous mixture sample of step b) exceeds a predetermined threshold, and if the difference between the characteristics of the crude sample and the characteristics of the aqueous mixture sample of step b) is much greater than the characteristics of the purified sample.

[0190] Therefore, preferably, the characteristic difference between the crude sample and the purified sample is at least 10%, particularly at least 20%, and particularly at least 30%, relative to the characteristics of the purified sample.

[0191] Other advantageous embodiments and combinations of features of the invention will become apparent from the following exemplary embodiments and all patent claims. Brief description of the attached diagram

[0193] Figure 1 The relationship between the smectite content in the cement composition and the difference (solid line) in flow spread (FS) between filtered (purified) and unfiltered (coarse) samples is shown. FS is obtained by the method of the present invention.

[0194] Exemplary Implementation

[0195] 1. Cement slurry-based method

[0196] Step 1: Determine the PCE concentration of the reference flow:

[0197] The goal of this step is to determine the PCE concentration required to achieve a flow spread of 14 cm using a fixed w / c of ​​0.35. Therefore, 35 g of water and 0.45 g of PCE (e.g., ...) are mixed. A solution of -125P (adjusted to a solids content of 30% in water) is mixed with 100g of Portland cement in a cup using a wooden scraper for 30 seconds to ensure uniform mixing of the slurry. The resulting cement slurry is then filled into a miniature cone (height: 58mm; lower inner diameter: 38mm; upper inner diameter: 19mm) placed on a flat, dry glass plate. The slump flow of the slurry is then determined by slowly lifting the miniature cone and measuring the maximum elongation of the slurry after spreading. If necessary, the process is repeated with different PCE dosages until a flow rate of 14 ± 0.5 cm is achieved.

[0198] Step 2: Mix with sand

[0199] In this step, the sand sample is brought into contact with the aqueous solution determined in step 1. Specifically, if 0.45 g of PCE is required to obtain a flow rate of 14 cm, 100 g of sand (dried in an oven at 60°C) is gradually mixed with 1.93 g of PCE used in step 1 and 150 g of water, and stirred with a wooden spatula for a total of 60 seconds. Thus, the total amount of water is added in portions of 50 g and 100 g, respectively. Specifically, the first portion of water is added to pre-wet the sand sample, then the PCE is added to the pre-wetted mixture, followed by the addition of the remaining water.

[0200] After mixing, immediately use a pipette to remove 35g of the supernatant without filtering, as the coarse sample in the first cup.

[0201] Extract an additional amount of suspension from the covering sand using a syringe, then drain it through a 0.2 μm filter into a separate second cup. Repeat the procedure until the total volume of liquid in the second cup is 35 g. This sample is called the purified sample.

[0202] Step 3: Comparison of flow characteristics

[0203] The goal of this step is to identify whether the sand sample adsorbed PCE in step 2 by comparing the flow spread with the initial reference flow.

[0204] First, mix 100g of cement (the same cement used in step 1) with the coarse (unfiltered) sample obtained in step 2 and stir manually for 30 seconds with a wooden scraper. Then, determine the slump flow similar to step 1.

[0205] Next, 100g of cement (the same cement used in step 1) was mixed with the purified (filtered) sample obtained in step 2 and stirred with a wooden scraper for 30 seconds. Then, the collapse flow was determined similarly to step 1.

[0206] If the slump flow of the coarse and purified samples is comparable to the reference flow (i.e., 14 cm), the results can be interpreted as the absence of PCE adsorption and an additional low fine particle content. In this case, the analyzed sand can be used in mortar or concrete compositions without additional additives, provided that the water requirement, which can be determined individually, is equal to the standard water requirement of the given mineral binder composition. Additionally, the addition of a modifier is recommended to compensate for water adsorption.

[0207] If the slump flow of the test using a purified sample is comparable to the reference flow (i.e., 14 cm), and the flow extension of the test using a coarse sample is less than 13.5 cm, there is a potential "high fineness" problem. In this case, if the sand analyzed is used in mortar or concrete compositions, moderators for "high fineness" situations or other solutions for high fineness, such as optimizing the mixing design of the mineral binder composition, should be considered.

[0208] If the flow spread of both the crude and purified samples is less than 13.5 cm, it can be concluded that PCE adsorption is present. In this case, if the sand analyzed is intended for use in mortar or concrete compositions, a moderating agent to compensate for PCE adsorption should be considered. To determine the specific source of PCE adsorption and propose a suitable moderating agent, the method according to step 4 is required.

[0209] Step 4: Identify the source of PCE adsorption

[0210] The goal of this step is to identify the source of PCE adsorption. Therefore, step 4 is only performed if the flow spread measured with the purified sample in step 3 is below, for example, 13.5 cm (=threshold).

[0211] Possible sources of PCE adsorption include, for example, expanded clay.

[0212] For example, to examine whether the source of PCE adsorption in sand is related to expanded clay, a clay-blocking additive can be added to the PCE solution in step 2, for example, by adding the clay-blocking additive to the first portion of water used for pre-wetting. Steps 2 and 3 are then repeated with a modified PCE solution containing the clay-blocking additive. If the flow spread obtained with the purified sample is improved in the repetition of step 3, it can be concluded that expanded clay is at least partially responsible for PCE adsorption.

[0213] The content of montmorillonite and the quantitative amount of mildening additives

[0214] With the help of the method of the present invention, the relationship between flow expansion and the concentration of adsorbed substance can be derived by interpolation.

[0215] For example, if montmorillonite (expanded clay) is identified as an impurity in sand (which can be checked in step 4 or by X-ray diffraction), the following formula describes the relationship between the montmorillonite content S (in weight %) and the flow spread FS (in cm) obtained with the purified sample: S = 1.039 – 0.001 × e 0.484×FS .

[0216] Similarly, the amount of montmorillonite S (in weight %) can be related to a certain dose E (in weight %) of the moderating agent (in this case, the nonionic comb polymer P1 described in WO 2020 / 070095 A1, page 32, line 15 to page 33, line 4) required to restore the performance of the PCE at a given dose: E = 4.2006 × S – 0.0372 (depending on the formula for the moderating agent).

[0217] Alternatively, the performance of PCE can be improved by adding an extra amount of P to PCE (e.g. -125P, adjusted to a solids content of 30% in water) to increase its dosage to restore: P = -1.6874 × FS + 22.157 (depending on the specific PCE formula).

[0218] Therefore, the cement slurry-based method allows for the direct identification of the source of PCE adsorption, the type of moderating agent, and the concentration required to compensate for PCE adsorption from a simple measurement of the flow spread of different samples.

[0219] Based on this information, suitable additives can be provided by mixing plasticizers and modifiers in appropriate proportions.

[0220] Identification of Combinatorial Problems

[0221] Compositional problems can be identified by plotting the relationship between the amount of a specific impurity in the cement composition and the difference in flow spread (FS) between filtered (purified) and unfiltered (coarse) samples, thereby obtaining the FS using the method of the present invention.

[0222] Figure 1 An example of this plot of montmorillonite is shown. The solid line was obtained through a calibration procedure. Therefore, for different sand samples containing an increased proportion of montmorillonite, the FS of the filtered sample and the FS of the unfiltered sample were determined using the method of the present invention. Therefore, montmorillonite is used as the sole source of PCE adsorption. Therefore, Figure 1 The solid line in the figure reflects the calibration relationship between the difference in FS and the proportion of montmorillonite. In principle, a separate calibration curve is required for each PCE adsorption source.

[0223] If it is known that montmorillonite exists in sand at a given concentration (which can be determined, for example, by X-ray diffraction), then Figure 1 The calibration curve can be used to identify the problem type of a given sand. If sand sample A1 with a given montmorillonite concentration (0.8 wt% of cement) shows an FS difference, it is located at... Figure 1Below the solid line (<1.21 cm), the sand exhibits a pure adsorption problem with plasticizers. On the other hand, if another sand sample A2 with the same montmorillonite concentration shows a FS difference higher than the solid line (>1.21 cm), there is a combined problem of plasticizer adsorption and high fine particle content. Therefore, depending on the FS difference at a specific montmorillonite concentration (above / below the solid line) in a specific sand sample, appropriate mitigation measures can be taken in a targeted manner.

[0224] 2. TOC-based approach

[0225] In the first step, an alkaline aqueous solution with a pH of 13 containing the following salt components is prepared:

[0226]

[0227] As a second step, a solution consisting of 90 ml of the alkaline solution from the first step and 10 ml of PCE solution (1% solid content of PCE) is prepared.

[0228] In the third step, for example, the total organic matter content of a 20 ml sample of the solution from the second step is measured using a device from Shimadzu called TOC-V CPN.

[0229] In the third step, a solution consisting of 90 ml of the alkaline solution from the first step, 10 ml of PCE solution (1% solid content of PCE) and 30 g of the sand to be analyzed was prepared, and the solution was shaken on a shaking table (250 rpm) for 90 minutes, and then centrifuged for 10 minutes (4,000 rpm).

[0230] In the fourth step, 20 ml of the solution covering the sand was taken out with a syringe and filtered through a filter, and the total organic matter content of the solution was determined.

[0231] The difference in total organic matter content between the solutions from the second and fourth steps is directly related to the adsorption of PCE by adsorbing impurities present in the sand.

[0232] For example, when three different specific sands were tested, all of which produced high superplasticizer requirements (the amount of superplasticizer required to achieve the defined consistency) in the hydraulic binder composition, yielding PCE adsorption of 10.6 wt%, 12.6 wt%, and 16.1 wt% (=100% - TOC content), respectively. These results indicate that the TOC-based approach is well-suited for quantifying undesirable adsorption of plasticizer additives.

[0233] To determine the specific source of PCE adsorption and propose a suitable moderating agent, the moderating agent can be added to the solution in the third step, and the third and fourth steps can be repeated until the difference in total organic matter content is below a threshold, such as 2% of the total organic matter content of the solution in the second step.

[0234] Those skilled in the art will understand that the invention may be practiced in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments disclosed herein are to be regarded in all respects as illustrative rather than restrictive.

Claims

1. A method for characterizing sand in terms of plasticizer adsorption, comprising the following steps: a) Provide an aqueous mixture of plasticizers having a defined concentration of plasticizers; b) Determine the characteristics of the aqueous mixture, wherein the characteristics are related to the proportion of the plasticizer in the aqueous mixture; c) Contact the sand sample to be analyzed with the aqueous mixture or a sample thereof, such that the sand sample is completely immersed in the aqueous mixture or a sample thereof; d) Obtain a supernatant sample from the mixture in step c); e) Determine that the supernatant sample has the same characteristics as in step b); f) Compare the characteristics of the aqueous mixture or its sample obtained in step b) with the characteristics of the supernatant sample obtained in step e) to determine whether the characteristics differ from each other by more than a predetermined threshold. In step d), a coarse supernatant sample and a purified sample of the supernatant are obtained from the aqueous mixture, wherein the purified sample does not contain suspended fine particles with a particle size <125 μm. In step e), the characteristics of the crude supernatant sample and the purified sample are determined separately and compared with the characteristics of the aqueous mixture sample in step b). in: -If the characteristics of the crude supernatant sample and the purified sample determined in step e) differ from the characteristics of the aqueous mixture sample in step b) by more than a given threshold, then an additive that compensates for the adsorption of plasticizers is selected as a moderating agent. If the characteristics of the coarse supernatant sample differ from those of the aqueous mixture sample from step b) by more than a given threshold, and the characteristics of the purified sample differ from those of the aqueous mixture sample from step b) by less than a given threshold, then an additive to compensate for high fine particle content is selected as a moderating agent. in: - In step b), an aqueous slurry comprising a sample of the aqueous mixture of step a) and a defined proportion of a mineral binder is prepared, wherein water and mineral binder have a given w / c ratio; and the rheological parameters of the aqueous slurry are determined to characterize the sample of the aqueous mixture; and - In step e), another aqueous slurry is prepared using the same mineral binder as in step b) and a supernatant as water, wherein the ratio of supernatant to mineral binder is the same as the w / c ratio in step b), and the same rheological parameters as in step b) are used to characterize the supernatant sample. or In steps b) and e), the total organic matter content of the aqueous mixture or the supernatant sample is determined as the characteristic.

2. The method according to claim 1, wherein, If the comparison in step f) shows that the characteristics of the aqueous mixture or its sample differ from the characteristics of the supernatant sample by more than a given threshold, then steps c) to f) are repeated, thereby using different aqueous mixtures containing plasticizers of varying concentrations and / or modifiers of defined concentrations in step c).

3. The method of claim 2, wherein the repetition continues until the comparison in step f) shows that the characteristics of the aqueous mixture or its sample and the characteristics of the supernatant sample differ from each other by less than a given threshold.

4. The method of claim 3, wherein the concentration of the plasticizer and / or the type and / or concentration of the modifier are varied in each repetition.

5. The method according to any one of claims 2-4, wherein an additive for preparing a mineral binder composition is provided, wherein the additive comprises a plasticizing additive and / or a modifier in proportions obtained by the method according to any one of claims 2-4.

6. The method of claim 5, wherein the additive comprises a plasticizer and / or modifier in the proportion obtained in the last repetition of the method of claim 3.

7. The method according to any one of claims 1-4, wherein the method includes an additional step a'), which comprises the following sub-steps: (i) Determine the water requirement of the mineral binder composition containing the sand to be analyzed and the plasticizer additive; (ii) The water requirement determined in sub-step (i) is compared with the standard water requirement of the given mineral binder composition.

8. The method of claim 1, wherein in step b), the mineral binder is cement.

9. The method of claim 1, wherein in step b), the rheological parameters are collapse flow.

10. The method of claim 1, wherein in step e), the rheological parameters are collapse flow.

11. The method of claim 1, wherein the concentration of the plasticizer in step a) is selected to achieve predetermined rheological parameters of the slurry produced in step b) at a predetermined ratio of mineral binder and a predetermined ratio of water to mineral binder w / c.

12. The method of claim 11, wherein the predetermined rheological parameter is a predetermined collapse flow.

13. The method according to any one of claims 1-4, wherein in step a), an aqueous mixture with a pH of 11-14 is prepared and / or in step a), an aqueous mixture is prepared using sulfate and / or hydroxide salts.

14. The method of claim 13, wherein the pH is 12-13.

5.

15. The method of claim 13, wherein the pH is 12.5-13.

5.

16. The method of claim 13, wherein in step a), an aqueous mixture is prepared using calcium sulfate, sodium sulfate, potassium sulfate, potassium hydroxide, calcium hydroxide and / or sodium hydroxide.

17. The method according to any one of claims 1-4, wherein the plasticizer is polycarboxylate ether (PCE).

18. The method of claim 1, wherein the purified sample is free of suspended fine particles with a particle size <63 μm.

19. The method of claim 1, wherein the purified sample is free of suspended fine particles with a particle size <2 μm.

20. The method of claim 1, wherein the purified sample is obtained by filtration and / or centrifugation.

21. The method of claim 20, wherein the purified sample is obtained by filtration.

22. The method of claim 7, further comprising the step of providing a mineral binder composition comprising sand of the type used in any one of claims 1-4, and: - If step f) during the first execution shows that the characteristics of steps b) and e) differ from each other by more than a predetermined threshold, then a moderating agent is used to compensate for the adsorption of plasticizer additives.

23. The method of claim 22, further comprising the step of providing a mineral binder composition comprising sand and other aggregates of the type used in any one of claims 1-4.

24. The method according to claim 22 or 23, wherein, If step a') shows a high water demand and step f) shows that the characteristics of steps b) and e) differ from each other by no more than a predetermined threshold on the first execution, then a moderating agent is used to compensate for water adsorption.

25. The method according to claim 22 or 23, wherein, If the first execution of step f) shows that, when the crude supernatant sample and the purified sample are obtained as described above in step d), the characteristics of the crude supernatant sample differ from the characteristics of the aqueous mixture sample of step b) by more than a given threshold, and the characteristics of the purified sample differ from the characteristics of the aqueous mixture sample of step b) by less than a given threshold, then a moderating agent for compensating for high fine particles and / or measures to deal with high fine particles are used.

26. The method according to claim 22 or 23, wherein, If the first execution of step f) shows that when the crude supernatant sample and the purified sample are obtained in step d), the characteristics of both the crude supernatant sample and the purified sample differ from the characteristics of the aqueous mixture sample of step b) by more than a predetermined threshold, and if the difference between the characteristics of the crude supernatant sample and the characteristics of the aqueous mixture sample of step b) is greater than the difference between the characteristics of the purified sample, then a moderating agent for compensating for the adsorption of plasticizer additives and a moderating agent for compensating for high fineness and / or measures to deal with high fineness are used.

27. The method of claim 22, wherein if step f) during the first execution shows that the characteristics of steps b) and e) differ from each other by more than a predetermined threshold, a moderating agent is used to compensate for the adsorption of the plasticizer additive, wherein, Plasticizers and / or modifiers are used in proportions obtained by the method according to any one of claims 2-6.

28. The method of claim 27, wherein, Plasticizers and / or modifiers are used in proportions obtained in the last repetition of steps c) to f) according to claims 5.

29. The method of claim 26, wherein measures to address high particle size include adjusting the mixing design of the mineral binder composition.

30. A method for preparing a mineral binder composition, wherein an admixture is provided according to any one of claims 5-6, and the composition is mixed with water, a mineral binder, and sand of the type analyzed in any one of claims 5-6.

31. A method for preparing the mineral binder composition according to claim 30, wherein an admixture is provided according to any one of claims 5-6, and the admixture is mixed with water, a mineral binder, sand of the type analyzed in any one of claims 5-6, and other aggregates.

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