A retarder for alleviating cement false setting and its preparation method and application

Abstract

The application discloses an inhibitor for relieving cement false setting and a preparation method and application thereof. The inhibitor comprises the following components in parts by weight: a retarding component 5-10 parts, a surface active component 0.5-3 parts and a metal impurity component 87-94 parts. The retarding component is selected from one or more than one of sodium tripolyphosphate, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, aminotri (methyl) phosphonic acid, ethylenediamine tetramethylene phosphonic acid, diethylene triamine penta (methyl) phosphonic acid penta sodium and 2-phosphonic acid butane-1, 2, 4-tricarboxylic acid. The metal impurity component is a monovalent or divalent metal sulfate. The inhibitor can effectively relieve or solve the problem of poor flow performance and sharp viscosity increase of freshly mixed concrete caused by cement false setting, keep the smoothness of concrete working performance and ensure the easy construction of concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an inhibitor for alleviating false setting in cement, its preparation method, and its application. Background Technology

[0002] Cement is an important component of concrete, a building material, and its proper setting is crucial for its practical application. False setting of cement refers to the phenomenon where cement, after being mixed with water, hardens rapidly without releasing a large amount of heat. While the cement paste can regain its plasticity without needing to be remixed with additional water, its fluidity is significantly reduced.

[0003] Several reasons for the occurrence of false setting in cement: (1) The temperature will rise during the cement grinding process. Usually, when it is above 110℃, dihydrate gypsum (CaSO4·2H2O) dehydrates to form hemihydrate gypsum (CaSO4·0.5H2O) and soluble anhydrous gypsum (CaSO4). The dissolution rate of hemihydrate gypsum is higher than that of dihydrate gypsum. Theoretically, it can better control the hydration of C3A. However, hemihydrate gypsum can dissolve faster than C3A, combine with water and revert to dihydrate gypsum, forming a supersaturated solution and crystals of dihydrate gypsum, causing false setting in cement; (2) The phenomenon of false setting is related to the alkali present in cement. For some cements with high alkali content, the potassium sulfate contained therein will react according to the following formula: K2SO4+CaSO4·2H2O=K2SO4·CaSO4·H2O+H2O. The resulting false gypsum crystals grow rapidly, which will also cause false setting.

[0004] With the widespread use of ready-mixed concrete today, the issue of false setting in cement is receiving increasing attention in the industry. JC / T602-2009, "Test Method for Early Setting of Cement," specifies that cement with a penetration percentage <50% is considered to have set early; if the cement recovers its plasticity after stirring without adding water, it is considered to have set falsely. The standard stipulates that the penetration at 5 minutes is the final penetration value. However, in reality, much cement false setting occurs after 5 minutes. For example, hemihydrate gypsum only begins to hydrate and crystallize at 5-6 minutes, and is basically completely hydrated into dihydrate gypsum at 30 minutes. The exact time of false setting is uncertain, but most cases occur before 30 minutes. Furthermore, cement false setting is directly related to ambient temperature. Even if a cement passes factory testing, differences in ambient temperature during application can cause false setting. Therefore, the phenomenon of cement false setting is frequently observed.

[0005] False setting of cement does not involve a true hydration reaction and has no effect on setting time or strength, but it will lead to a deterioration in the workability of fresh concrete, especially high-grade concrete. When high-grade concrete false sets, it will regain some fluidity after mixing, but the viscosity will increase significantly, which will seriously affect the judgment of the state of fresh concrete leaving the mixer and the performance of concrete pumping.

[0006] When encountering the problem of false setting in cement in practical applications, the current solutions are only to mitigate / solve the issue through process modifications or changes in the mixing equipment. CN114474363A discloses a method for eliminating false setting in prestressed cement slurry, a cement slurry, and a method for testing false setting. This method primarily involves the secondary addition of mixing water and admixtures, supplemented by secondary mixing, to eliminate false setting in prestressed cement slurry. Specifically, water and admixtures are added in batches during mixing. CN112608095A discloses an expanding slurry for prestressed pipe grouting and its preparation method. This method employs a secondary mixing process to reduce the adverse effects of early false setting on the slurry's fluidity. Specifically, after the initial mixing, a few minutes are allowed between mixing and the occurrence of false setting before secondary mixing is performed. However, the aforementioned existing technologies do not address the material-related solution to the problem of false setting in cement. Furthermore, adjusting the process or changing the mixing equipment during production can reduce production efficiency or increase production costs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an inhibitor for mitigating false setting of cement, its preparation method, and its application. This inhibitor can effectively alleviate / solve the problems of poor flowability and sharp increase in viscosity of freshly mixed concrete caused by false setting of cement, maintain stable concrete workability, and ensure that the concrete is easy to construct.

[0008] This invention is achieved through the following technical solution:

[0009] An inhibitor to alleviate false setting of cement comprises the following components by weight: 5-10 parts of retarding component, 0.5-3 parts of surfactant component, and 87-94 parts of metallic impurity component;

[0010] The retarding component is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid pentasodium, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0011] The metallic impurity components are monovalent or divalent metal sulfates.

[0012] Preferably, the surfactant component is selected from one or more of hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, and hexadecylpentyldimethylammonium bromide.

[0013] Preferably, the metallic impurity component is selected from one or more of lithium sulfate, copper sulfate, zinc sulfate, cadmium sulfate, and magnesium sulfate.

[0014] Preferably, the retarding component is any one or a mixture of two of sodium tripolyphosphate and hydroxyethylidene diphosphonic acid.

[0015] Preferably, the surfactant component is any one or a mixture of two of sodium dodecyl sulfate and sodium dodecyl sulfonate.

[0016] Preferably, the metallic impurity component is any one or a mixture of two of lithium sulfate and zinc sulfate.

[0017] Furthermore, the preparation method of the above-mentioned inhibitor for alleviating false setting in cement includes the following steps:

[0018] The retarding component, surface-active component, and metal impurity component are mixed evenly according to the solid mass ratio to form a powder.

[0019] The above-mentioned inhibitor for mitigating false setting of cement is applied by incorporating the inhibitor into cement at a dosage of 0.5% to 2.0% of the total mass of cement. By controlling the incorporation ratio, the degree of false setting of cement can be mitigated.

[0020] The beneficial effects of this invention are as follows:

[0021] The inhibitor of the present invention for mitigating false setting of cement has a good synergistic effect among its components, and also affects the solubility and dissolution rate of hemihydrate gypsum, the crystal structure of dihydrate gypsum, and the solubility of potassium sulfate. It inhibits different types of false setting of cement and can effectively alleviate / solve the problem of false setting of cement, especially significantly improving the false setting of high-grade concrete. Moreover, it does not require any adjustment to the process or changes to the mixing device during production, making it suitable for widespread application. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0023] An inhibitor for mitigating false setting in cement comprises the following components by weight: 5-10 parts of retarding component, 0.5-3 parts of surfactant component, and 87-94 parts of metallic impurity component.

[0024] The retarding component is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonate pentasodium, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0025] The surface-active component is selected from one or more of hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, and hexadecylpentyldimethylammonium bromide.

[0026] The metallic impurity component is selected from one or more of lithium sulfate, copper sulfate, zinc sulfate, cadmium sulfate, and magnesium sulfate.

[0027] Determination of False Setting in Cement: Referring to the requirements of JC / T 602-2009 "Test Method for Early Setting of Cement", the penetration percentage of the cement paste after adding the false setting inhibitor described in the following examples was measured. The initial penetration was tested according to the standard. The final penetration was measured at six time points: 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min. The minimum penetration value was taken as the final penetration, and the penetration percentage was calculated. False setting was determined according to the standard: if the penetration percentage was <50%, the cement was considered to have set early; if the cement regained its plasticity after stirring without adding water, it was considered to have set falsely.

[0028] Three types of cement were selected for testing: cement-1 was ordinary cement, and cement-2 and cement-3 were both pseudo-cement. The mineral composition of the cement is shown in Table 1 below, where each component is a mass percentage.

[0029] Table 1 Mineral composition of three types of cement

[0030]

[0031] Example 1

[0032] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0033] (1) Weigh the following raw materials according to their mass percentages:

[0034] (Sodium tripolyphosphate + hydroxyethylidene diphosphonic acid): Sodium dodecyl sulfate: Lithium sulfate = 5:1:94.

[0035] The mass ratio of sodium tripolyphosphate to hydroxyethylidene diphosphonic acid is 1:1.

[0036] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0037] In this embodiment, cement-2 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 1% of the total cement mass.

[0038] Example 2

[0039] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0040] (1) Weigh the following raw materials according to their mass percentages:

[0041] (Sodium tripolyphosphate + hydroxyethylidene diphosphonic acid): Sodium dodecyl sulfate: Lithium sulfate = 5:1:94.

[0042] The mass ratio of sodium tripolyphosphate to hydroxyethylidene diphosphonic acid is 1:1.

[0043] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0044] In this embodiment, cement-2 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 2% of the total cement mass.

[0045] Example 3

[0046] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0047] (1) Weigh the following raw materials according to their mass percentages:

[0048] (Sodium hexametaphosphate + ethylenediaminetetramethylenephosphonic acid): Sodium dodecyl sulfonate: Cadmium sulfate = 5:3:92.

[0049] The mass ratio of sodium hexametaphosphate to ethylenediaminetetramethylenephosphonic acid is 1:1.

[0050] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0051] In this embodiment, cement-2 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 1% of the total cement mass.

[0052] Example 4

[0053] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0054] (1) Weigh the following raw materials according to their mass percentages:

[0055] (Sodium tripolyphosphate + hydroxyethylidene diphosphonic acid): Sodium dodecyl sulfate: Lithium sulfate = 5:3:92.

[0056] The mass ratio of sodium tripolyphosphate to hydroxyethylidene diphosphonic acid is 1:1.

[0057] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0058] In this embodiment, cement-3 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 1% of the total cement mass.

[0059] Example 5

[0060] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0061] (1) Weigh the following raw materials according to their mass percentages:

[0062] (Sodium hexametaphosphate + aminotrimethylphosphonic acid): (hexadecyltrimethylammonium bromide + sodium dodecyl sulfonate): (lithium sulfate + zinc sulfate) = 5:1:94.

[0063] The mass ratios of sodium hexametaphosphate and aminotrimethylphosphonic acid, hexadecyltrimethylammonium bromide and sodium dodecyl sulfonate, and lithium sulfate and zinc sulfate are all 1:1.

[0064] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0065] In this embodiment, cement-2 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 1% of the total cement mass.

[0066] Example 6

[0067] A method for preparing an inhibitor to alleviate false setting in cement, comprising the following specific steps:

[0068] (1) Weigh the following raw materials according to their mass percentages:

[0069] (Sodium hexametaphosphate + aminotrimethylphosphonic acid): (hexadecyltrimethylammonium bromide + sodium dodecyl sulfonate): (lithium sulfate + zinc sulfate) = 10:1:89.

[0070] The mass ratios of sodium hexametaphosphate and aminotrimethylphosphonic acid, hexadecyltrimethylammonium bromide and sodium dodecyl sulfonate, and lithium sulfate and zinc sulfate are all 1:1.

[0071] (2) Mix evenly to form a powder, which is the cement false setting inhibitor.

[0072] In this embodiment, cement-2 was selected for testing. The prepared cement false setting inhibitor was added to the cement paste at a dosage of 1% of the total cement mass.

[0073] Comparative Example 1

[0074] Sodium dodecyl sulfate and lithium sulfate were weighed at a mass ratio of 1:99, mixed evenly, and made into a powder.

[0075] In this embodiment, cement-2 was selected for testing. The prepared powder was added to the cement paste at a rate of 1% of the total cement mass.

[0076] Comparative Example 2

[0077] Sodium tripolyphosphate and hydroxyethylidene diphosphonic acid are mixed evenly at a mass ratio of 1:1 to form a powder.

[0078] In this embodiment, cement-2 was selected for testing. The prepared powder was added to the cement paste at a rate of 0.05% of the total cement mass.

[0079] Comparative Example 3

[0080] In this embodiment, cement-2 was selected for testing, and no inhibitors were added to the cement paste.

[0081] Comparative Example 4

[0082] In this embodiment, cement-3 was selected for testing, and no inhibitors were added to the cement paste.

[0083] Comparative Example 5

[0084] In this embodiment, cement-1 was selected for testing, and no inhibitors were added to the cement paste.

[0085] Test Example 1

[0086] Referring to the requirements of JC / T 602-2009 "Test Method for Early Setting of Cement", the percentage of cement paste penetration after adding the cement false setting inhibitor of the present invention (Examples 1-5) was compared with the control group (Comparative Examples 1-5). The test results are shown in Table 2.

[0087] The rheological properties of cement paste were tested for 5–30 min using a rotational rheometer (R / S) at a controlled shear rate and 20 °C, with a water-cement ratio of 0.29. The rheological parameters after adding the cement false setting inhibitor of the present invention (Examples 1-5) were compared with those of the control group (Comparative Examples 1-5). The test results are shown in Table 2.

[0088] Table 2. Test results of cement paste performance

[0089]

[0090] As shown in Table 2, Cement-1, as ordinary cement, does not exhibit false setting when the false setting inhibitor of this invention is not added. However, Cement-2 and Cement-3 (false setting cement, i.e., containing components that cause false setting) exhibit obvious false setting when the false setting inhibitor of this invention is not added, but the false setting phenomenon is significantly weakened or even disappears after adding the inhibitor of this invention.

[0091] Yield stress and viscosity reflect the rheological properties of the slurry. When false setting occurs, the rheological properties of the slurry will change significantly, with both yield stress and viscosity increasing. When the false setting phenomenon weakens, both yield stress and viscosity decrease. As shown in Table 2, the yield stress and viscosity values ​​of Examples 1-6 are generally lower than those of Comparative Examples 1-4. When there is no false setting at all, both yield stress and viscosity are at their minimum. As shown in Table 2, Comparative Example 5 has the minimum yield stress and viscosity.

[0092] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. An inhibitor to alleviate false setting in cement, characterized in that, The components include, by weight, 5-10 parts of a retarding component, 0.5-3 parts of a surface active component, and 87-94 parts of a metal impurity component; The retarding component is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, aminotri(methyl)phosphonic acid, ethylenediamine tetra(methylene)phosphonic acid, diethylenetriamine penta(methylene)phosphonic acid pentasodium, and 2-phosphonobutane-1,2,4-tricarboxylic acid. The metal impurity component is a monovalent or divalent metal sulfate.

2. The inhibitor to mitigate false set of cement according to claim 1, wherein, The surface active component is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, and cetyl pentyl dimethyl ammonium bromide.

3. The inhibitor to mitigate false set of cement according to claim 1, wherein The metal impurity component is selected from one or more of lithium sulfate, copper sulfate, zinc sulfate, cadmium sulfate, and magnesium sulfate.

4. The inhibitor to mitigate the false set of cement according to claim 1, wherein, The retarding component is any one or a mixture of both of sodium tripolyphosphate and hydroxyethylidene diphosphonic acid.

5. The inhibitor to mitigate the false set of cement according to claim 2, wherein, The surface active component is any one or a mixture of both of sodium dodecyl sulfate and sodium dodecylsulfonate.

6. The inhibitor to mitigate the false set of cement according to claim 3, wherein, The metal impurity component is any one or a mixture of both of lithium sulfate and zinc sulfate.

7. A process for the preparation of the inhibitor for the mitigation of false set of cement according to any one of claims 1 to 6, characterized in that, The components include: The retarding component, the surface active component, and the metal impurity component are mixed uniformly according to the solid mass ratio to form a powder, and the powder is obtained.

8. A method of using the inhibitor for alleviating the false setting of cement according to any one of claims 1 to 6, characterized by, The inhibitor for relieving the false setting of cement is mixed into cement, and the amount is 0.5-2.0% of the total mass of the mixed cement.

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