Anti-mud agent based on in-situ surface modification of artificial sand mud powder as well as preparation method and application of anti-mud agent

Abstract

The invention belongs to the technical field of concrete admixtures, and discloses an anti-mud agent based on artificial sand mud powder surface in-situ modification as well as a preparation method and application of the anti-mud agent. The anti-mud agent is prepared from the following raw materials in parts by mass: 1 to 10 parts of fluosilicate, 0.1 to 10 parts of silane coupling agent, 0.1 to 1 part of cationic surface active agent, 0.1 to 0.5 part of sodium lignin sulfonate and 0.5 to 1 part of polyethylene glycol. According to the invention, fluosilicate reacts with active Al < 3 + >, Ca < 2 + > and the like in the mud powder in the artificial sand to generate an insoluble fluoroaluminate inorganic membrane, and the insoluble fluoroaluminate inorganic membrane tightly wraps the surfaces of mud powder particles, so that the adsorption characteristic of the mud powder is essentially changed. The water reducing agent further comprises the silane coupling agent, the silane coupling agent is hydrolyzed and then condensed with hydroxyl on the surface of the mud powder to form a hydrophobic organic silicon film, water absorption and expansion are inhibited, adsorbed water is released, adsorption of the mud to the water reducing agent is reduced, and meanwhile the mechanical property of an interface transition area can be improved.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, and in particular to an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, its preparation method and application. Background Technology

[0002] Aggregates, as the skeleton of concrete, typically constitute 65% to 75% of the concrete volume and are a key component determining the volume stability, thermal properties, and economy of concrete. Their quality directly influences the strength development, durability, and construction adaptability of the concrete. Currently, with the depletion of natural sand resources, manufactured sand, as a substitute for natural sand, is playing a significantly larger role as a concrete aggregate.

[0003] Mud content refers to the total mass percentage of fine particles such as clay, shale fragments, and stone powder with a particle size smaller than 0.075 mm in aggregates, and is a core control indicator for measuring aggregate cleanliness. Clay minerals (such as montmorillonite, illite, and kaolinite) have strong adsorption properties due to their layered structure, while stone powder is mostly a byproduct of mechanical crushing. Although their forms differ, their mechanisms of interference with concrete performance are highly similar. When the mud content of aggregates exceeds 3%, the layered structure of the clay minerals adsorbs a large amount of free water, thus disrupting the water-cement ratio balance. Simultaneously, excessive mud content adsorbs water-reducing agent molecules, hindering the normal function of the water-reducing agent and significantly reducing the workability of the concrete mix. More seriously, the cation exchange capacity of clay particles neutralizes the negative charge in the cement paste, thereby disrupting the zeta potential stability and triggering cement paste flocculation. This phenomenon is particularly prominent in the application of manufactured sand. Most existing slump retainers use hydroxycarboxylate retarder components. These products lack anti-mud properties, and the slump loss rate can reach more than 70% when the mud content is 5%. When faced with aggregates with high mud content, the defects of this technology are significantly exposed.

[0004] Therefore, developing anti-mud agents that combine anti-mud properties, slow-release properties, and enhanced performance of mixtures for artificial sand with high mud content has become a common technical challenge in the industry. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-mud agent based on in-situ surface modification of artificial sand powder, its preparation method and application, to solve the above-mentioned problems of artificial sand with high mud content.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following raw materials in parts by weight: 1-10 parts of fluorosilicate, 0.1-10 parts of silane coupling agent, 0.1-1 parts of cationic surfactant, 0.1-0.5 parts of sodium lignosulfonate, and 0.5-1 parts of polyethylene glycol.

[0007] Preferably, the fluorosilicate is one or more of sodium fluorosilicate, magnesium fluorosilicate, and zinc fluorosilicate.

[0008] Preferably, the silane coupling agent is one or more of vinyltrimethoxysilane, n-dodecyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and ethyltriethoxysilane.

[0009] Preferably, the cationic surfactant is one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, tetramethylammonium bromide, and tetraethylammonium bromide.

[0010] Preferably, the polyethylene glycol is one or more of PEG-200, PEG-400, PEG-600, PEG-800, and PEG-1000.

[0011] This invention also provides a method for preparing an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following steps: Fluorosilicate, cationic surfactant, sodium lignosulfonate, and polyethylene glycol are mixed, and then a silane coupling agent is added to obtain an anti-mud agent based on in-situ surface modification of artificial sand and mud powder.

[0012] The present invention also provides an anti-mud agent based on in-situ surface modification of artificial sand powder, or an anti-mud agent based on in-situ surface modification of artificial sand powder prepared by the above preparation method, for use in building materials.

[0013] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) The main raw material composition of the anti-mud agent of the present invention includes fluorosilicate, which utilizes the active Al of fluorosilicate and mud powder in artificial sand. 3+ Ca 2+ The reaction generates an insoluble fluoroaluminate inorganic film that tightly coats the surface of the mud powder particles, fundamentally altering the adsorption characteristics of the mud powder. The use of fluorosilicates in this invention has the following effects: Fundamental transformation: Unlike the “surface coating” of silanes, fluorosilicates chemically transform mud powder from the inside out, turning it from a harmful, unstable mineral into a stable, inert substance with a certain strength.

[0014] Suppressing expansion: The use of fluorosilicates fundamentally alters the clay powder, completely destroying the crystal structure of expansive clays such as montmorillonite, thus permanently eliminating their ability to absorb water and expand.

[0015] Increased strength: The generated fluorides and silica gel also act as cementing materials, improving the cohesion between artificial sand particles and the overall strength.

[0016] Reduced adsorption: After the mud powder is decomposed and solidified, its huge specific surface area and active adsorption sites are destroyed and covered, thereby reducing the adsorption of water-reducing agents and water by the mud.

[0017] (2) The main raw material composition of the anti-mud agent of the present invention also includes a silane coupling agent. The silane coupling agent, after hydrolysis, condenses with the hydroxyl groups on the surface of the mud powder to form a hydrophobic organosilicon film. The use of the silane coupling agent of the present invention has the following effects: Inhibits water absorption and expansion: The formed hydrophobic film prevents water molecules from entering the mud powder, fundamentally solving the problems of water absorption and expansion.

[0018] Release the adsorbed water: The "ineffective water" that was originally bound by the mud powder is released, which improves the effective utilization rate of the mixing water.

[0019] Reduced adsorption of water-reducing agent: The surface of the mud powder is covered by an organic film, which reduces the number of adsorption sites, allowing the water-reducing agent to act more effectively on the cement particles.

[0020] Improved mechanical properties of the interface transition zone: Improved interfacial bonding between mud powder and cement paste, which is beneficial to the improvement of concrete mechanical properties and durability.

[0021] (3) The anti-mud agent of the present invention also includes a small amount of cationic surfactant, sodium lignosulfonate and polyethylene glycol. The cationic surfactant inhibits the expansion of clay and reduces the adsorption of water-reducing agent by introducing cationic groups (such as quaternary ammonium salts) to combine with anionic groups in clay. Sodium lignosulfonate and polyethylene glycol can disperse cement particles and reduce water consumption, thereby indirectly reducing the impact of mud powder on concrete performance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 The initial slump and 1-hour slump are the reference set of this invention; where A is the initial slump and B is the 1-hour slump. Figure 2 The initial slump and 1-hour slump are given in Embodiment 1 of the present invention; where A is the initial slump and B is the 1-hour slump. Detailed Implementation

[0024] This invention provides an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following raw materials in parts by weight: 1-10 parts of fluorosilicate, 0.1-10 parts of silane coupling agent, 0.1-1 parts of cationic surfactant, 0.1-0.5 parts of sodium lignosulfonate, and 0.5-1 parts of polyethylene glycol.

[0025] In this invention, the fluorosilicate is preferably one or more of sodium fluorosilicate, magnesium fluorosilicate, and zinc fluorosilicate.

[0026] In this invention, the mechanism of fluorosilicate treatment of mud powder in artificial sand involves using hydrofluoric acid (HF) as a medium to acid-etch and decompose the crystal structure of the mud powder, followed by precipitation and solidification using the subsequently generated dense fluoride and silica gel. This process fundamentally solves the problems caused by mud powder by transforming harmful mud powder into a stable new phase, representing a more intense and thorough "chemical passivation" method. The specific reaction principle is as follows: (1) Hydrolysis of fluorosilicates (taking sodium fluorosilicate as an example) Fluorosilicates hydrolyze in water to produce hydrofluoric acid (HF) and silicic acid (H4SiO4).

[0027]

[0028] (2) Erosion of clay mineral surfaces by hydrofluoric acid (HF)

[0029] The generated HF is a weak acid, but the F in it... - Fluoride ions have extremely strong coordination ability (hydrofluoric acid is one of the few acids that can react with silicon dioxide and silicates), and can react with Al in clay minerals. 3+ Ca 2+ Forming stable complexes.

[0030]

[0031] The generated insoluble fluoroaluminate / calcium salt precipitate covers and encapsulates the surface of clay particles and the pores between particles, playing a strong role in cementing and pore blockage.

[0032] (3) The cementing effect of silicic acid

[0033] Silicic acid (H4SiO4) is unstable and undergoes a condensation reaction in solution, forming dimers and oligomers, ultimately generating silica gel (SiO2·nH2O), which encapsulates clay particles to form a robust thin film. It also fills pores, plugging the tiny spaces between clay particles. Furthermore, it exhibits physicochemical adsorption, binding tightly to the clay surface through hydrogen bonds and van der Waals forces. Simultaneously, the silica gel acts as a "binder" for the entire cementing system, firmly binding the previously formed fluoride precipitates and clay particles together, further coating the clay particles.

[0034] In this invention, the silane coupling agent is preferably one or more of vinyltrimethoxysilane, n-dodecyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and ethyltriethoxysilane.

[0035] In this invention, the reaction principle of the silane coupling agent is as follows: (1) Hydrolysis Taking vinyltrimethoxysilane as an example, when it is added to a sand and gravel mixture containing trace amounts of moisture or directly contacted with an aqueous solution, the methoxy group (-OCH3) undergoes a hydrolysis reaction.

[0036]

[0037] The three methoxy groups (-OCH3) are replaced by the three hydroxyl groups (-OH) to generate the active silanetriol CH2=CH-Si(OH)3, and methanol is released.

[0038] (2) Physical adsorption and orientation on the surface of mud powder

[0039] The main component of clay powder is clay minerals, whose surface is rich in hydroxyl groups (-OH). The Si-OH groups on the silane triol form hydrogen bonds with the Si-OH or Al-OH groups on the clay powder surface. At the same time, the organic functional group (vinyl-CH=CH2) at the other end of the silane is hydrophobic and tends to face outwards towards the particle. This process allows the silane molecules to achieve a preliminary, directional alignment on the clay powder surface.

[0040] (3) Condensation reaction and covalent bonding

[0041] Physically adsorbed silane molecules undergo a condensation reaction with the surface of the mud powder, forming strong covalent bonds.

[0042]

[0043] Intermolecular condensation of silane molecules

[0044] The Si-OH groups of glycerol undergo a dehydration condensation reaction with the hydroxyl groups (-OH) on the surface of the clay powder, generating stable Si-O-Si (siloxane) bonds. These bonds are very strong, allowing the organosilane layer to be covalently anchored to the inorganic surface of the clay powder particles. Simultaneously, condensation occurs between adjacent silane molecules, forming a cross-linked polysiloxane network coating. Ultimately, the surface of the clay powder particles is encapsulated by a polysiloxane film with a three-dimensional network structure terminated in vinyl groups. The organic portion (vinyl) of this film faces outwards, imparting strong hydrophobicity to the originally hydrophilic clay powder particles. Water molecules find it difficult to wet and penetrate the interior of the clay powder particles, thus significantly inhibiting the clay powder's tendency to absorb water and swell.

[0045] In this invention, the mud powder is preferably kaolinite (Al4Si4O). 108 Or Al2Si2O5(OH)4), montmorillonite ((Na,Ca) 0.33 (Al, Mg)2Si4O 102 ·nH2O), illite (K 0.65 Al2Al 0.65 Si 3.35 O 102 ), vermiculite ((Mg, Ca) 0.7 (Mg,Fe,Al)6(Al,Si)8O 24 One or more of the following.

[0046] In this invention, the cationic surfactant is preferably one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, tetramethylammonium bromide, and tetraethylammonium bromide.

[0047] In this invention, the polyethylene glycol is preferably one or more of PEG-200, PEG-400, PEG-600, PEG-800, and PEG-1000.

[0048] This invention also provides a method for preparing an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following steps: Fluorosilicate, cationic surfactant, sodium lignosulfonate, and polyethylene glycol are mixed, and then a silane coupling agent is added to obtain an anti-mud agent based on in-situ surface modification of artificial sand and mud powder.

[0049] The present invention also provides an anti-mud agent based on in-situ surface modification of artificial sand powder, or an anti-mud agent based on in-situ surface modification of artificial sand powder prepared by the above preparation method, for use in building materials.

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] This embodiment provides an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following raw materials in parts by weight: 5 parts sodium fluorosilicate, 1 part vinyltrimethoxysilane, 0.5 parts hexadecyltrimethylammonium bromide, 0.2 parts sodium lignosulfonate, and 0.6 parts PEG-400.

[0053] Example 2

[0054] This embodiment provides an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following raw materials in parts by weight: Sodium fluorosilicate 1 part, vinyltrimethoxysilane 1 part, tetraethylammonium bromide 0.8 parts, sodium lignosulfonate 0.1 parts, PEG-200 1 part.

[0055] Example 3

[0056] This embodiment provides an anti-mud agent based on in-situ surface modification of artificial sand and mud powder, comprising the following raw materials in parts by weight: 10 parts magnesium fluorosilicate, 1 part methyltrimethoxysilane, 2 parts vinyltrimethoxysilane, 0.6 parts dodecyltrimethylammonium chloride, 0.4 parts sodium lignosulfonate, and 0.8 parts PEG-800.

[0057] Comparative Example 1

[0058] This embodiment provides an anti-mud agent, specifically as described in Example 1, except that it does not contain sodium fluorosilicate.

[0059] Comparative Example 2

[0060] This embodiment provides an anti-mud agent, specifically as described in Example 1, except that it does not contain vinyltrimethoxysilane.

[0061] Applications of the anti-mud agents prepared in Examples 1-3 and Comparative Examples 1-2: First, the anti-mud agent, manufactured sand (mud content 5%), and water were pre-mixed and reacted. Then, crushed stone and polycarboxylate superplasticizer were added and mixed. Finally, cementitious materials (P·O 42.5 cement and fly ash) were added and stirred until uniform. The concrete mix proportions and properties of the mixture are shown in Table 1. The compressive strength, frost resistance, and impermeability of the concrete were tested according to DL / T 5150 "Test Methods for Hydraulic Concrete", and the results are shown in Table 2. The slump of the reference group and Example 1 are as follows: Figure 1 and Figure 2 As shown.

[0062] Table 1 Concrete mix proportions and mixture properties

[0063] Note: The dosages of anti-mud agent and water-reducing agent are 1.0% and 0.8% of the mass percentage of cementitious materials, respectively.

[0064] Table 2 Test Indicators for Mechanical and Durability Properties of Concrete

[0065] Table 2 shows that by incorporating the anti-mud agent of this invention, the unit water consumption and cementitious material consumption of concrete are significantly reduced while maintaining the initial slump, mechanical properties, and durability without degradation. The slump loss over 1 hour is also significantly reduced. A comparison of Examples 1 and 2 reveals a synergistic effect between the combined use of fluorosilicate and silane coupling agent. Compared to using fluorosilicate or silane coupling agent alone, the combined use significantly reduces slump loss, providing a new solution to the current situation of high mud content in manufactured sand.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An anti-mud agent based on in-situ surface modification of artificial sand and mud powder, characterized in that, Raw materials comprising the following parts by weight: 1-10 parts of fluorosilicate, 0.1-10 parts of silane coupling agent, 0.1-1 parts of cationic surfactant, 0.1-0.5 parts of sodium lignosulfonate, and 0.5-1 parts of polyethylene glycol.

2. The anti-mud agent based on in-situ surface modification of artificial sand and mud powder according to claim 1, characterized in that, The fluorosilicate is one or more of sodium fluorosilicate, magnesium fluorosilicate, and zinc fluorosilicate.

3. The anti-mud agent based on in-situ surface modification of artificial sand and mud powder according to claim 2, characterized in that, The silane coupling agent is one or more of vinyltrimethoxysilane, n-dodecyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and ethyltriethoxysilane.

4. The anti-mud agent based on in-situ surface modification of artificial sand and mud powder according to claim 3, characterized in that, The cationic surfactant is one or more of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, tetramethylammonium bromide, and tetraethylammonium bromide.

5. The anti-mud agent based on in-situ surface modification of artificial sand and mud powder according to claim 4, characterized in that, The polyethylene glycol is one or more of PEG-200, PEG-400, PEG-600, PEG-800, and PEG-1000.

6. A method for preparing an anti-mud agent based on in-situ surface modification of artificial sand and mud powder according to any one of claims 1 to 5, characterized in that, Includes the following steps: Fluorosilicate, cationic surfactant, sodium lignosulfonate, and polyethylene glycol are mixed, and then a silane coupling agent is added to obtain an anti-mud agent based on in-situ surface modification of artificial sand and mud powder.

7. The application of the anti-mud agent based on in-situ surface modification of artificial sand powder as described in any one of claims 1 to 5, or the anti-mud agent based on in-situ surface modification of artificial sand powder prepared by the preparation method described in claim 6, in building materials.

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