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    • 专利摘要:
    The invention also relates to an additive for improving the fluidity and the early and delayed mechanical development of concrete or cement pastes, in particular those based on cements in which a significant part of the clinker has been substituted for supplementary cementing materials (SCMs) such as fly ash, blast furnace slag, silica fume, dehydroxylated clays or other aluminosilicate materials.
    公开号:ES2807673A2
    申请号:ES202090059
    申请日:2018-06-07
    公开日:2021-02-23
    发明作者:Olga Maltseva；Lodeiro Inés García；Jiménez Ana María Fernández；Sánchez Angel Palomo
    申请人:S A Sulquisa；
    IPC主号:
    专利说明:

    [0002] Additive to improve fluidity and mechanical development in cement pastes, mortars or concrete
    [0004] FIELD OF THE INVENTION
    [0005] The present invention belongs to the field of additives for mortars or concrete. In particular, the present invention refers to an additive to improve the fluidity and early and late mechanical development of cement or concrete pastes, especially those based on Portland cements in which a significant part of the cement has been replaced (cement clinker ) by mineral additions, commonly called "supplemental cementing materials" (SCMs) such as fly ash, blast furnace slag, silica fume, heat-treated (dehydroxylated) clays, or other silicoaluminous materials.
    [0007] The present invention also relates to a method for producing said additive, as well as to a binder composition comprising it and to the use of the additive to improve the mechanical and flow characteristics of cement or concrete pastes.
    [0009] BACKGROUND OF THE INVENTION
    [0010] One of the main challenges of the cement sector is to reduce CO 2 emissions into the atmosphere. For the period 2013-2020, according to the revision of the Emissions Trading Directive, the maximum limit of emission rights corresponding to each of the 27 Member States will be replaced by a single maximum limit at EU level: decrease of 20 % of Greenhouse Gas (GHG) emissions in 2020 compared to 2005 levels, reducing emissions from sectors included in the emissions trading regime by 21% and by 10%, in the case of non-regulated ones .
    [0012] The objective of 21% reduction in CO 2 emissions, still not specified by sector, will require a great additional effort on the part of the cement sector. Currently the cement sector contributes between 8 and 9% to total CO 2 emissions, which means that it will have to reduce its emissions between 2% and 3%, if the level of production is maintained at the current rate. However, the forecasts are that the level of production will increase globally in the coming years; therefore it is foreseeable that the decrease in emissions should be greater than the 2% or 3% indicated above.
    [0013] In the Portland cement (OPC) manufacturing process, 60% of CO2 emissions come from the processing of the materials, that is, from the decarbonization of the limestones necessary to manufacture OPC clinker, which makes their reduction extremely difficult. The other 40% is due to the ignition of the fuels used to heat the furnace and of course to the transport of raw materials and the finished product. In this sense, it should be noted that in recent years European cement companies in general have already undertaken important investment plans, with the aim of implementing available technological improvements to increase energy efficiency, reduce CO2 emissions and optimize the process. of production.
    [0015] One of the most interesting bets to reduce CO2 emissions is to replace part of this Portland cement clinker with supplementary cementitious materials (SCMs) or even part of the Portland cement with the same SCMs in the production of concretes. SCMs are commonly by-products from other industries, such as fly ash, blast furnace slag, and silica fume. This type of by-product is normally associated with low CO2 emissions (minimum energy required for drying, grinding and transport).
    [0017] In fact, this is a practice included in the regulations. Most of the current commercial cements usually incorporate between 10 and 25% of these SCMs. These cements in the presence of additives, sand and / or gravel are capable of generating mortars and concretes with excellent mechanical-resistant and durable behavior. The amount of SCMs that is generally incorporated into cements, mortars and concretes is limited, depending on the type of SCMs and the application of the final product; This is due to the fact that very high levels of substitution of OPC by SCMs can lead to less development of mechanical resistance, especially at early ages.
    [0019] In the preparation of OPC-based mortars and concretes, superplasticizing concrete additives are used to improve the properties of fresh concrete, in terms of fluidity and workability, but a significant improvement is also sought in the development of strengths and the final durability of the concrete. concrete.
    [0021] The present invention is directed to a new type of additive capable of improving the fluidity and the early (2 days) and late (28 days) mechanical development of pastes, mortars and concretes in OPC bases and especially in those with a high level of replacement of OPC by SCMs. The results obtained indicate that the effect of the additive of the invention is more significant in pastes, mortars and concretes with a level of substitution of OPC by SCMs greater than 25%. Considering as SCMs. ashes flywheels, blast furnace slag, silica fume, heat-treated (dehydroxylated) clays, or other silicoaluminous materials.
    [0023] In this way, the additive of the present invention not only has the advantage of improving the fluidity and mechanical development of cement pastes, concrete or mortars, but also allows the percentage of Clinker and / or cement to be lowered and that of SCMs without affect the mechanical characteristics of the resulting concrete and at the same time favoring the objective of reducing CO2 emissions and the objective of producing more durable materials.
    [0025] OBJECT OF THE INVENTION
    [0026] Therefore, the main object of the present invention is an additive for cementitious compositions that comprises a mixture of:
    [0027] a) a saturated aqueous solution of an alkaline salt at a pH equal to or greater than 13.5 and b) a dispersing agent for solid particles in solution
    [0029] that is added to the cement, concrete or mortar paste in a percentage by weight with respect to the total cementing material of between 3 and 6%. In the context of the present application, this additive will be referred to as the additive of the invention.
    [0031] Another additional object is a process for preparing said additive of the invention.
    [0033] It is also an object of the invention, a binder composition comprising, among other elements, the additive of the invention.
    [0035] Finally, the object of the invention is the use of the additive of the invention to improve the fluidity and mechanical development of the cement paste, concrete or mortars and to improve the mechanical characteristics and durability in the final mortars and / or concretes.
    [0037] BRIEF DESCRIPTION OF THE FIGURES
    [0039] Figure 1: diagram of the process to follow according to the mini-slump test.
    [0040] Figure 2: Flowability of cement pastes measured by the mini-slump test in the absence of additive (a) and presence of additive (b).
    [0042] Figure 3: setting times of the cements (a) without additives and (b) with the additive of the invention
    [0044] Figure 4: Increase in percentage of the resistance to (a) flexion and (b) compression for the different cement mortars tested due to the use of the additive of the invention
    [0046] DETAILED DESCRIPTION OF THE INVENTION
    [0047] In order to facilitate understanding and clarify the meaning of certain terms in the context of the present invention, the following definitions are provided:
    [0049] "Clinker", "Cement Clinker" or "Portland Cement Clinker": Product resulting from the calcination of clays and limestones at high temperatures (1450-1550 o C) during the cement manufacturing process. The mineralogical phases that make up Clinker are mainly tricalcium silicate or alite (C 3 S), dicalcium silicate or belite (C 2 S), tricalcium aluminate (C 3 A) and the ferritic phase (C 4 AF).
    [0051] " Portland Cement (OPC) " It is the product resulting from the joint grinding of Clinker with a small amount of gypsum (calcium sulfate), which has the property of regulating the setting. The addition of other products is allowed as long as their inclusion does not affect the properties of the resulting cement. Cement is a hydraulic, powdery binder, composed predominantly of calcium silicates and aluminates that, in reaction with water and after a setting process, lead to the formation of a hardened, stable and durable matrix, with binding properties, with adequate strength and rigidity.
    [0053] "Cementitious compositions" : in the context of the present invention refers to formulations that comprise and / or are based on clinker or Portland cement or on mixtures of clinker or portland cement and SCMs as essential binder component.
    [0055] "Aggregates": Inorganic granulated material such as gravel or broken stone, used in the manufacture of concrete.
    [0056] "Cement paste": is the mixture of cement and water.
    [0058] "Mortar ": is the mixture of cement, sand and water.
    [0060] "Concrete "; Binder resulting from the mixture of cement, water and aggregates (which are classified into gravel, gravel and sand) in the appropriate proportions.
    [0062] "Mineral additions or supplementary cementing materials (SCMs)": Mineral additions are materials of natural or artificial origin, the mixture of which with portland clinker in the manufacture of cement, or with cement to produce mortars and concretes, enables technological improvements to be achieved in their performance, both in its behavior in a fresh state and in its resistant and durable properties. Additions react through their hydraulic or pozzolanic activity or both. Examples of SCMs are coal combustion fly ash (FA), blast furnace slag (BFS), silica fume and heat-treated (dehydroxylated) clays.
    [0064] "Cementing material or binder material " : in the context of the invention refers to the set of materials that, in the presence of water or other substances, form a soft paste with binder properties that sets and hardens to give rise to a rigid material. In the present invention this term is applied to both portland cement and OPC + SCMs mixtures.
    [0066] "Chemical Additives" They are chemical compounds that in small proportions are incorporated into pastes, mortars and concrete. The purpose of its dosage is to modify one or several properties of cementitious mixtures, improving their performance, whether in their fresh or hardened state. Their impact on the performance and properties of concretes with specific functions makes them a necessary component.
    [0068] "Dispersing agent or dispersing agent for solid particles": refers to agents with the ability to disperse the solid particles that make up cements, enhancing their reactivity. It includes among others the additives known as plasticizers and superplasticizers. In the context of the present invention the dispersing agent is preferably selected from among lignosulfonates, melamines, naphthalene sulfonates, polycarboxylates or mixtures thereof.
    [0069] "Saturated aqueous solution": refers to a solution that contains as much solute as possible. In the context of the present invention, it is applied to the solution of the alkaline salt, which is therefore in a state of saturation.
    [0071] "Alkaline salt": Refers to a chemical compound formed by alkaline cations (for example Na + or K + type ) linked to anions (for example Cl-, CO 42- , SO 42 - , NO 32 -...) by means of an ionic bond. Preferably, the alkaline salt can be selected from Na 2 SO 4 , NaCl, NaNO 3 , Na 2 CO 3 , Na 2 SiO 3 and sodium oxalate.
    [0073] "Alkaline hydroxide": refers to a hydroxide of an alkaline element, preferably sodium or potassium.
    [0075] "Inert atmosphere": in the context of the invention refers to an atmosphere that prevents any type of reaction in the solution from occurring during the dissolution and stabilization process of the solution of an alkaline salt, such as carbonation due to the presence of CO 2 . The inert atmosphere can be achieved by using any type of inert gas such as N 2 .
    [0077] "Flowability": A measure of the consistency of the cement paste expressed in terms of the increase in diameter of a specimen molded into a frusto-conical part, after shaking a specified number of times.
    [0079] "Mechanical development": Development over time of the bending and / or compression strengths (normally measured in MPa) of pastes, mortars and concrete.
    [0081] "Early mechanical development": in the context of the invention, it is the development over time of the bending and / or compressive strengths (normally measured in MPa) of pastes, mortars and concrete in the first moments of setting, as a reference they are taken 48 hours (two days).
    [0083] "Late mechanical development": in the context of the invention it is the development in time of the bending and / or compressive strengths (normally measured in MPa) of pastes, mortars and concretes late in the setting, as reference the 28 days.
    [0084] "Mechanical resistance to bending": Resistance of a material to deformation that presents an elongated structural element in a direction perpendicular to its longitudinal axis.
    [0086] "Mechanical resistance to compression": Maximum stress that a material can withstand under a crushing load.
    [0088] Additive
    [0089] The main aspect of the present invention refers to an additive for cementitious compositions comprising a mixture of:
    [0091] a) a saturated aqueous solution of an alkaline salt at a pH equal to or greater than 13.5 and b) a dispersing agent for solid particles in solution
    [0093] that is added to the cement, concrete or mortar paste in a percentage by weight with respect to the total cementing material of between 3 and 6%.
    [0095] The additive is added to the fresh paste of cement, mortar or concrete in a percentage by weight with respect to the total cementing material that can range between 3% and 6%. The additive has a synergistic effect on fluidity and the development of mechanical strengths.
    [0097] In particular, the additive of the invention has the effect of improving the fluidity of the cement, mortar or concrete paste and of improving the early (at 2 days) and late (at 28 days) mechanical development of these. This effect is especially notable in cementitious or binder compositions with a high content of SCMs, that is, with a content greater than 25% by weight with respect to the cementing material.
    [0099] In a particular and preferred embodiment, the saturated aqueous solution of the alkaline salt represents 80-85% by weight of the mixture and the dispersing agent in solution represents 15 to 20% by weight of the mixture.
    [0101] Preferably, the saturated aqueous solution comprises an alkaline salt selected from Na2SO4, NaCl, NaNO3, Na2CO3, Na2SiO3, sodium citrate, sodium oxalate or mixtures thereof. The preferred embodiment of the invention contemplates the use of Na2SO4 as the alkaline salt.
    [0102] For the dissolution of the alkaline salt, the aqueous medium must have a strongly alkaline pH, since the alkaline medium allows the solubilization of the alkaline salt in water to be increased. For example, a concentrated solution of 1 M KOH makes it possible to increase the solubility of Na2SO4 with respect to its solubility in water up to 272 SO42-g / l.
    [0104] For this reason, the dissolution of the alkaline salt must be done at a pH equal to or greater than 13.5, which is obtained by prior dissolution of an alkaline hydroxide, preferably NaOH or KOH.
    [0106] On the other hand, as will be explained later, the conditions for preparing the aqueous solution of the alkaline salt are of vital importance since, for its application, the dissolution must be stabilized and that implies, among other things, that the dissolution of the salt Alkaline is carried out in a controlled atmosphere free of CO2, to avoid carbonation. This is normally achieved using working in an atmosphere with a continuous stream of N2.
    [0108] The other fundamental element of the additive of the invention is the dispersing agent that represents between 15 and 20% of the additive. These types of agents are organic compounds with dispersing properties of solid particles. These agents are used primarily to improve the fluidity and workability of cements, mortars or concrete in a fresh state.
    [0110] Preferably, the dispersing agent is selected from lignosulfonates, melamines, naphthalene sulfonates, polycarboxylates, or mixtures thereof, although the preferred embodiment of the invention contemplates that the dispersing agent is a polycarboxylate.
    [0112] Procedure for the preparation of the additive
    [0114] Another relevant aspect of the invention is represented by the process for the preparation of the additive of the invention, which comprises:
    [0116] a) prepare a solution in deionized water of an alkaline hydroxide, preferably KOH or NaOH, at a concentration of approximately 1M,
    [0117] b) dissolving an alkaline salt until obtaining a saturated aqueous solution thereof, c) subjecting the saturated aqueous solution obtained in b) to a stabilization period that comprises a continuous stirring process in an inert atmosphere for a minimum period of 9 days and at a temperature between 15 to 30 ° C; Y
    [0118] d) combining the solution of c) with the dispersing agent of solid particles in solution in a percentage by weight on the mixture of 80 to 85% and 15 to 20% respectively.
    [0120] Step a) has the purpose of providing a medium that facilitates the dissolution of the alkaline salt. A strongly alkaline aqueous medium based on a highly concentrated alkaline hydroxide provides a pH equal to or greater than 13.5 which favors and facilitates the solubility of the alkaline salt in step b).
    [0122] The alkaline salt is dissolved by stirring, for example with a magnetic stirrer, and is preferably selected from Na2SO4, NaCl, NaNO3 Na2CO3, Na2SiO3, sodium citrate or sodium oxalate, although the preferred embodiment comprises the use of Na2SO.
    [0124] After the solubilization stage, the saturated solution of the alkaline salt is subjected to a stabilization process that involves keeping it under continuous stirring in an inert atmosphere for a minimum period of 9 days. The inert atmosphere implies a controlled and CO2-free atmosphere, for example by means of a continuous stream of an inert gas such as N2.
    [0126] The last stage of the process involves combining the stabilized alkaline salt solution with the solid particle dispersing agent.
    [0128] In a particular embodiment, the solid particle dispersing agent used in the preparation of the additive of the invention is selected from among lignosulfonates, melamines, naphthalene sulfonates, polycarboxylates or mixtures thereof, although the preferred embodiment of the invention contemplates that the dispersing agent is a polycarboxylate.
    [0130] Binder composition
    [0131] Another aspect of the invention is a cementitious binder composition comprising:
    [0133] a) a cement comprising at least a fraction of clinker or Portland cement and supplementary cementing materials (SCMs);
    [0134] b) water;
    [0135] c) an additive according to any one of claims 1 to 6; Y
    [0136] d) optionally aggregates.
    [0137] The cement used in the composition of the invention preferably comprises a Portland cement that is partially replaced by supplemental cementitious materials (SCMs). In a preferred embodiment, the Portland cement used in the binder composition of the invention is replaced by a percentage by weight of SCMs equal to or greater than 25% by weight with respect to clinker, preferably equal to or greater than 25%, even more preferably equal or greater than 50% and even more preferably equal to greater than 65%.
    [0139] In a particular and preferred embodiment of the invention, the SCMs are selected from fly ash, blast furnace slag, silica fume, dehydroxylated clays or their mixtures.
    [0141] In a more particular embodiment, the cement comprises a percentage equal to or greater than 20% by weight of clinker or Portland cement and the supplementary cementing materials (SCMs) are found in a percentage equal to or greater than 25% by weight, even more preferably equal to or greater than 50% and even more preferably equal to greater than 65%.
    [0143] The binder composition of the invention, thanks to the presence of the additive of the invention, allows the use of a much higher proportion of SCMs than that incorporated in normal cements, mortars and concretes without affecting the mechanical characteristics of the paste. resulting cement, concrete or mortar. Furthermore, the composition of the invention makes it possible to solve one of the problems pursued by the present invention, which is to limit or reduce CO2 emissions thanks to the reduction in the consumption of clinker or Portland cement.
    [0145] A preferred embodiment of the invention contemplates that in the binder composition of the invention, the concrete paste formed by the cement and the water and optionally the aggregates represents between 94 and 97% by weight and the additive represents between 3 and 6% by weight of the total composition.
    [0147] As mentioned above the composition of the invention may optionally comprise aggregates. The nature and granulometry of these aggregates can be anything normally used in construction, although preferably the aggregates are gravels and / or siliceous or calcareous sands.
    [0148] Use of the additive of the invention
    [0150] Another general aspect of the invention refers to the use of the additive of the invention to improve the fluidity and mechanical development of the cement paste and to improve the mechanical characteristics and durability in the final mortars and / or concretes.
    [0152] In particular, the effect of improving the fluidity and mechanical development of the cement paste as well as the improvement of the mechanical characteristics and durability in the final mortars and / or concretes, is especially suitable in cement pastes based on cements where a high percentage of Clinker has been replaced by SCMs.
    [0154] Thus, the use of the additive of the invention is particularly preferred in cement pastes, concrete or mortars based on a binder fraction comprising a percentage equal to or greater than 20% by weight of cement clinker and supplementary cementitious materials (SCMs) they are in a percentage equal to or greater than 25% by weight, even more preferably equal to or greater than 50% and even more preferably equal to greater than 65%. SCMs can be selected from fly ash, blast furnace slag, silica fume, dehydroxylated clays or their mixtures.
    [0156] As will be demonstrated in the examples section, the improvement of the fluidity and the mechanical development of the pastes through the use of the additive of the invention is substantiated both in an improvement of the early mechanical development and of the late mechanical development of the cement paste, mortar or concrete.
    [0158] This improvement of the mechanical characteristics through the use of the additive of the invention is observed by measuring the parameters such as the mechanical resistance to bending and the mechanical resistance to compression. The use of the additive of the invention in cement paste, mortar or concrete produces a substantial improvement in both flexural and compressive strength compared to compositions without additives. On the other hand, the effect on these parameters becomes more significant as the percentage of SCMs in the composition of the cement used increases.
    [0160] The inventors have observed that the use of between 3% and 6% of the additive of the invention produces the following improvements:
    [0161] • An increase in the mechanical resistance of the pastes (with fly ash content of 25%) compared to the same paste without additives both in flexion and compression (in the order of 26% after 28 days).
    [0162] • An increase in the mechanical resistance of mortars (with fly ash content of 25%) with respect to the same without additives, both in bending (of the order of 23% at 2 days and 38% at 28 days) and compression (of the order of 32% at 2 days and 13% at 28 days).
    [0163] • Increase in flexural strength of the order of 62% after two days and 80% after 28 days in pastes with 65-75% fly ash content.
    [0164] • Increase in compressive strength of the order of 104% at 2 days and of the order of 68% at 28 days in pastes with fly ash content of 65-75%.
    [0166] EXAMPLES
    [0168] Example 1: preparation of an additive based on a saturated solution of NA SOa and Polycarbioxylate (PC)
    [0170] a) The first of the components of the additive of the invention is the saturated solution of an alkaline salt. In this example, the particular embodiment is described where a saturated and stabilized solution of NA2SO4 is prepared as the first element of the additive of the invention.
    [0172] The synthesis process of the saturated solution of NA2SO4 used the following raw materials:
    [0173] • Anhydrous Na2SO4 (Purity> 99.0%) provided by SULQUISA.SA
    [0174] • KOH (Purity> 85%) provided by PANREAC
    [0175] • Deionized water
    [0177] The preparation of the first component of the additive of the invention involves carrying out the initial dissolution of the inorganic salt, Na2SO4 in a solution of an alkaline base (1M KOH).
    [0179] For this, the 1M KOH solution was prepared by dissolving 56 grams of solid KOH in deionized water in a final volume of 1 liter.
    [0180] From here 30 grams of solid Na 2 SO 4 were dissolved in 100 grams of 1 M KOH solution.
    [0182] The sodium sulfate was dissolved in the alkaline solution with the help of a magnetic stirrer. After the initial dissolution process, the solution was subjected to a subsequent stabilization period, for a time of 9 days. The stabilization process consisted of the continuous stirring of the final solution in a mechanical rotor where the samples rotated continuously at a speed of 30 rpm. The dissolution process of the inorganic salt in the alkaline base and the subsequent stabilization time was carried out at a temperature of 22 ± 2 o C
    [0184] The sulfate dissolution process in the alkaline base was carried out in a controlled atmosphere of N 2 (free of CO 2 ), by means of a continuous stream of N 2 , thus avoiding carbonation.
    [0186] b) The second component of the additive of the invention is an organic compound with dispersant properties. In this case, a commercial Polycarboxylate (PC) product was used.
    [0188] c) The additive of the invention is made up of 80% -85% of the inorganic component and 20% -15% of the organic component.
    [0190] d) The dosage of the additive for the next examples is established in a proportion of 5.5% by weight with respect to the weight of the cement or cementitious materials (this weight includes SCMs, whether they are coal combustion fly ash, slag natural pozzolana etc.)
    [0192] Example 2: Effect of the additive of the invention on the properties of different cements with increasing amounts of SCMs
    [0194] Materials
    [0195] • Cements: A commercial cement of the resistant category 52.5 R (hereinafter OPC), with a Blaine of 4600 cm2 / g.
    [0196] • SCMs: A type F Flying Ash from the combustion of coal collected in a Spanish power plant (CV hereinafter), with 85% of particles with a size less than 45 ^ m
    [0197] • Sand: CEN EN 196-1 standardized sand
    [0198] • Additive of the invention: both in dosage and in nature it corresponds to that described in example 1
    [0199] For the evaluation of the effect of the additive, four types of cements were prepared with the previous raw materials. Each of these cements differs in its content in mineral additions (SCMs), in particular in its CV content.
    [0201] • CEM I: 100% OPC (Commercial Cement Type I 52.5R);
    [0202] • CEM II: 75% OPC 25 % Fly Ash (% by weight);
    [0203] • CEM III: 50% OPC 50% Fly Ash (% by weight);
    [0204] • CEM IV: 35% OPC 65% Fly Ash (% by weight).
    [0206] The chemical composition (% by weight of oxide) of each of these cements is shown in Table 1.
    [0207] Table 1 . Chemical composition of the cements produced (% by weight of oxide)
    [0209]
    [0211] As described in the following sections, the impact of the new additive on the hydration mechanisms of the cement was analyzed through:
    [0212] ■ Studies of fluidity, consistency and setting times with pastes
    [0213] ■ Studies of mechanical resistance with pastes, on prismatic test pieces of 1x1x6 cm3. ■ Studies of mechanical resistance in mortars on test pieces of 4x4x16 cm3.
    [0215] Example 2.1: Flow and consistency tests in cement pastes with and without the additive of the invention.
    [0217] To determine the fluidity of the pastes, the "mini-siump" test was carried out (see Figure 1). The mini-siump test is based on the UNE 80-116 standard but with minor modifications taking into account that it works with paste, and not with mortars as indicated in the standard. For its realization, a truncated-conical mold of material not attachable by pastes (methacrylate) was used. The mold has the following dimensions: internal diameter of the base = 38 mm; internal diameter of the mouth = 20 mm; height = 58 mm. The mold is placed on top of the shaking table (see Figure 1) formed by a frame placed on a rigid horizontal base that supports the table itself, in such a way form that can be lifted by a cam to a certain height before dropping it under its own weight. On the upper surface of the table in the center of it a circumference is drawn that serves to center the mold.
    [0219] The mold is placed in the center of the table supported by its larger base (38 mm), it is filled with paste, the occluded bubbles are eliminated and the surface is leveled. The mold is then carefully separated vertically and the tabletop is dropped 10 times. At the end of the ten strokes, the four diameters of the extended mass are measured and the arithmetic mean is calculated.
    [0221] These measurements are made at different times after manual kneading of the dough. It is important to bear in mind that the average time for kneading a dough is three minutes.
    [0223] Figure 2 shows the results of the mini-slump test of all types of cements made (CEMI, CEMII, CEMIII, CEMIV) without additives (reference system) and with the additive of the invention in a dosage of 5.5% . The results of the mini-slump test show that the mixture with the additive of the invention maintains adequate fluidity and improves the workability of cement pastes with various proportions of fly ash and a "liquid / solid" ratio 0.3.
    [0225] Example 2.2: Setting time tests on cement pastes with and without the additive of the invention.
    [0227] The setting time was determined with the Vicat needle as indicated in the EN 196-3 standard. The results obtained both at the beginning and at the end of setting are shown in Figure 3. Said results, in all cases (both in the absence and presence of the additive of the invention) are within the ranges of the values stipulated by the UNE- standard. EN 197-1. The most relevant data are: the increase in SCMs (fly ash in this case) delays and lengthens the setting times; the use of the additive of the invention also delays and lengthens the setting times.
    [0229] Example 2.3: Studies of mechanical resistance in cement pastes with and without the additive of the invention.
    [0231] To carry out the mechanical-resistant characterization, the reaction products were prepared prismatic samples of cement paste, which were cured at room temperature in the curing chamber (99% RH, 250C). At the ages of 2 and 28 days, the specimens were broken, determining the development of the mechanical resistance to bending and compression. The cements selected for said test were: CEM II, CEM III and CEM IV, described at the beginning of example 2. In all cases, 100 grams of cement were mixed with 30 grams of water so that the water-cement ratio is of 0.3. Table 2 shows the mechanical resistance values at 2 and 28 days for the different cements tested.
    [0233] Table 2. Mechanical resistance of additive pastes
    [0235]
    [0238] Table 3. shows, in percentage, the increases in resistance produced in the cement pastes associated with the use of the additive of the invention as a function of the type of cement (percentage of SCMs substituting portland cement).
    [0240] • For the pastes made with CEM II (75% OPC 25% CV), the incorporation of the additive of the invention significantly increases the flexural strengths with respect to the paste without additives, although it only slightly improves the compressive strength both at 2 as at 28 days;
    [0241] • For the pastes made with CEM III (50% OPC + 50% CV) the additive of the invention increases flexural strengths in the order of 28% at 2 days and 26% at 28 days; under compression this increase is 4% and 7% at 2 and 28 days respectively.
    [0242] • For pasta made with CEM IV (35% OPC + 65% CV), flexural strengths increase by around 23% at 2 days and 8% at 28 days; compression at around 13% at 2 days and 30% at 28 days with respect to the paste without additive.
    [0244] Table 3. Increase in mechanical resistance (in percentage) in cement pastes, hydrated with "inventive additive"
    [0245]
    [0248] Example 2.4: Studies of mechanical resistance in cement mortars with and without the additive of the invention.
    [0249] The mechanical strengths (both to bending and compression) of the cement mortar specimens in the presence of the additive of the invention were analyzed at the ages of 2 and 28 days. For them, prismatic mortar specimens 40 x 40 x 160 mm3 with a sand / cement ratio of 3: 1 were made as indicated in the EN 196-1 standard. The cements tested were CEM II (with 25% CV), CEM III (with 50 % CV) and CEM IV (with 65% CV). The liquid / solid ratio was determined through the drainage test, so that the values obtained were within the range 100-110 mm. Table 4 presents the details of the different compositions tested as well as the values of the mechanical strengths.
    [0251] The water / cement ratio was varied to obtain similar drainage results (105 ± 5 mm), since one of the properties of the additive of the invention is to reduce the amount of mixing water without significantly modifying the workability or fluidity. Both the water / cement ratio used and the runoff obtained in the mortars are given in Table 4.
    [0253] Table 4. Detail of the compositions and mechanical resistance values of the mortars made with CEM II
    [0255]
    [0256] In Table 5. The resistance increases produced in the cement mortars associated with the use of the additive of the invention are shown in percentage, depending on the type of cement tested (percentage of SCMs, substituting portland cement).
    [0258] • Mortars made with CEM II (75% OPC 25% CV), the additive of the invention increases the mechanical resistance of mortars both in flexion (of the order of 20% at 2 days and 39% at 28 days) and compression (of the order of 32% at 2 days and 13% at 28 days) with respect to the same mortars without additives.
    [0260] • Mortars made with CEM III (50% OPC 50% CV) the additive of the invention increases the mechanical resistance of mortars to bending by 13% at 2 days and 62% at 28 days, and the compressive strengths of the order of 45% at 2 days and 17% at 28 days.
    [0262] • Mortars made with CEM IV (35% OPC 65% CV) the additive of the invention increases the mechanical resistance of mortars to bending by 62% after 2 days and 80% at 28 days, and the compressive strengths of the order of 104% at 2 days and 68% at 28 days.
    [0264] Table 5. Increase in mechanical resistance (in percentage) in cement mortars, hydrated with "additive of invention"
    [0266]
    [0269] These results appear graphically in Figure 4. The effect of the additive of the invention is especially effective in systems with a higher content of fly ash (> 65%). In flexion, the effect of the additive is more relevant at 28 days, however, in compression, this effect is more relevant at initial ages (2 days). In any case, the use of the additive of the invention makes it possible to significantly increase the mechanical strength of cement mortars with high SCM content, replacing OPC Clinker or OPC cement.
    权利要求:
    Claims (18)
    [1]
    1. An additive for cementitious compositions comprising a mixture of:
    a) a saturated aqueous solution of an alkaline salt at a pH equal to or greater than 13.5 and b) a dispersing agent for solid particles in solution
    that is added to the cement, concrete or mortar paste in a percentage by weight with respect to the total cementing material of between 3 and 6%.
    [2]
    2. An additive according to claim 1 wherein the saturated aqueous solution of the alkaline salt represents 80-85% by weight of the mixture and the dispersing agent in solution represents 15 to 20% by weight of the mixture.
    [3]
    3. An additive according to any of the preceding claims wherein the saturated aqueous solution comprises an alkaline salt selected from among Na2SO4, NaCl, NaNO3, Na2CO3, Na2SiO3, sodium citrate and sodium oxalate or mixtures thereof, preferably it is Na2SO4.
    [4]
    4. An additive according to any of the preceding claims wherein the pH equal to or greater than 13.5 is obtained by prior dissolution of an alkaline hydroxide, preferably NaOH or KOH.
    [5]
    5. An additive according to any of the preceding claims wherein the dispersing agent is selected from lignosulfonates, melamines, naphthalene sulfonates, polycarboxylates or mixtures thereof, preferably it is a polycarboxylate.
    [6]
    6. A process for the preparation of the additive according to claim 1 comprising:
    a) prepare a solution in deionized water of an alkaline hydroxide, preferably KOH or NaOH, at a concentration of approximately 1M,
    b) dissolving an alkaline salt until obtaining a saturated aqueous solution thereof, c) subjecting the saturated aqueous solution obtained in b) to a stabilization period that comprises a continuous stirring process in an inert atmosphere for a minimum period of 9 days and at a temperature between 15 to 30 ° C; Y
    d) combining the solution of c) with the dispersing agent of solid particles in solution in a percentage by weight on the mixture of 80 to 85% and 15 to 20% respectively.
    [7]
    7. A process according to claim 6 wherein the alkaline salt is selected from Na2SO4, NaCl, NaNO3 Na2CO3, Na2SiO3, sodium citrate or sodium oxalate, preferably Na2SO4.
    [8]
    8. A process according to any of claims 6 or 7 wherein the solid particle dispersing agent is selected from among lignosulfonates, melamines, naphthalene sulfonates, polycarboxylates or mixtures thereof, preferably the plasticizer is a polycarboxylate.
    [9]
    9. A cementitious binder composition comprising:
    a) a cement comprising at least a fraction of clinker or Portland cement and supplementary cementing materials (SCMs);
    b) water;
    c) an additive according to any one of claims 1 to 6; Y
    d) optionally aggregates.
    [10]
    10. A composition according to claim 9 where the Clinker or Portland cement is in a percentage equal to or greater than 20% by weight and the supplementary cementing materials (SCMs) are in a percentage equal to or greater than 25% by weight. , even more preferably equal to or greater than 50% and even more preferably equal to greater than 65%.
    [11]
    11. A composition according to claim 10 wherein the supplementary cementing materials (SCMs) are selected from fly ash, blast furnace slag, silica fume, dehydroxylated clays or their mixtures.
    [12]
    12. A composition according to any of claims 9 to 11 where the concrete paste formed by the cement and the water and optionally the aggregates represents between 94 and 97% by weight and the additive represents between 3 and 6 % in weigh.
    [13]
    13. A composition according to any of claims 9 to 12 wherein the aggregates are gravels and / or siliceous or calcareous sands.
    [14]
    14. Use of an additive according to any of claims 1 to 5 to improve the fluidity and mechanical development of the cement paste and to improve the mechanical and durable characteristics in the final mortars and / or concretes.
    [15]
    15. Use according to claim 14 where the cement paste comprises Clinker or Portland cement in a percentage equal to or greater than 20% by weight and the supplementary cementing materials (SCMs) are in a percentage equal to or greater than 25% by weight, even more preferably equal to or greater than 50% and even more preferably equal to greater than 65%.
    [16]
    16. Use according to claim 15 where the SCMs are selected from fly ash, blast furnace slag, silica fume, dehydroxylated clays or their mixtures.
    [17]
    17. Use according to any of claims 14 to 16 where both early and late mechanical development is improved.
    [18]
    18. Use according to any one of claims 14 to 17 where the main improved mechanical characteristics are the mechanical resistance to bending and compression.
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    同族专利:
    公开号 | 公开日
    ES2807673B2|2022-02-28|
    WO2019234262A1|2019-12-12|
    ES2807673R2|2021-09-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP1052232A4|1998-11-30|2003-03-19|Taiheiyo Cement Corp|Process for producing dispersant for powdery hydraulic composition|
    JP6386281B2|2014-07-17|2018-09-05|株式会社日本触媒|Cement dispersant and cement composition|
    CN104628961B|2015-02-15|2017-03-22|北京工业大学|Method for preparing polycarboxylate superplasticizer by carrying out graft copolymerization on acrylic ester polymer and fatty acid vinyl ester|
    CN107721234A|2017-10-31|2018-02-23|遵义登禄建材有限公司|A kind of preparation method of cement additire|
    CN108101408A|2017-12-18|2018-06-01|常州达奥新材料科技有限公司|A kind of preparation method of cement retarder|
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