A kind of anticorrosion and rust resistance and permeation and crack resistance composite admixture suitable for steel fiber reinforced concrete

Abstract

The application relates to the technical field of building materials, and discloses a corrosion-resistant, rust-resistant, anti-permeation and anti-cracking composite admixture suitable for steel fiber reinforced concrete, which is composed of an ether type water-reducing polycarboxylic acid water-reducing agent mother liquor, an ester type slump-retaining polycarboxylic acid water-reducing agent mother liquor, a water-based isooctyl triethoxysilane emulsion, a non-pre-neutralized acid-base swelling acrylic acid ester copolymer emulsion, a Welan gum pre-hydration solution, triisopropanolamine, sodium gluconate, sodium phytate, a defoaming agent, a corrosion inhibitor and deionized water. When the corrosion-resistant, rust-resistant, anti-permeation and anti-cracking composite admixture is prepared, a pre-dilution adjusting solution and the Welan gum pre-hydration solution are prepared first, and then the water-reducing agent mother liquor, the Welan gum pre-hydration solution, the non-pre-neutralized acid-base swelling acrylic acid ester copolymer emulsion, the pre-dilution adjusting solution and the silane emulsion are sequentially compounded. The corrosion-resistant, rust-resistant, anti-permeation and anti-cracking composite admixture is favorable for improving the working performance, anti-segregation performance, steel fiber distribution uniformity, water resistance and chlorine ion resistance of the steel fiber reinforced concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a composite admixture adapted to steel fiber reinforced concrete for corrosion prevention, rust inhibition, seepage prevention, and crack prevention. Background Technology

[0002] Steel fiber reinforced concrete is a composite material formed by adding steel fibers to ordinary concrete matrix. It can improve the tensile, bending and crack resistance properties of concrete and has been applied in engineering scenarios such as tunnel support, bridge engineering, underground engineering and industrial flooring.

[0003] In steel fiber reinforced concrete mixtures, the density of steel fibers is greater than that of cement paste and aggregate paste systems. During mixing, transportation, pouring, or vibration, if the rheological properties of the paste are insufficient, the steel fibers are prone to settling or localized enrichment, leading to a decrease in the uniformity of the mixture and affecting the distribution of steel fibers in the matrix after hardening. Furthermore, steel fiber reinforced concrete is also susceptible to the intrusion of external media such as moisture and chloride ions during service, thus placing higher demands on the corrosion-resistant and rust-inhibiting properties of the steel fibers and the durability of the concrete.

[0004] In existing engineering projects, the performance of steel fiber reinforced concrete is typically improved by individually adding water-reducing agents, thickeners, corrosion inhibitors, or impermeable components. However, adding multiple admixtures separately presents challenges in terms of measurement and construction procedures; different components may also adversely affect the workability, rheological properties, or storage stability of the concrete. Especially when multiple polymeric components and emulsion components are pre-blended into a single product, improper control of pH environment, addition sequence, or dispersion method can easily lead to problems such as localized thickening, gel particles, emulsion separation, or significant changes in apparent viscosity, thereby affecting the storage stability and performance of the composite admixture.

[0005] Therefore, this invention proposes a composite admixture adapted to steel fiber reinforced concrete for corrosion prevention, rust inhibition, seepage prevention, and crack prevention, in order to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a composite admixture adapted to steel fiber reinforced concrete for corrosion prevention, rust inhibition, impermeability, and crack prevention. This solves the problems in practical engineering applications of steel fiber reinforced concrete, such as uneven distribution due to easy settling of steel fibers, the easy penetration of corrosive media such as chloride ions through capillary pores affecting the corrosion prevention and rust inhibition properties of steel fibers, and insufficient impermeability and crack prevention properties of concrete.

[0007] To address the above problems, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a composite admixture suitable for steel fiber reinforced concrete that is corrosion-resistant, rust-inhibiting, impermeable, and crack-resistant, employing the following technical solution:

[0009] A composite admixture suitable for steel fiber reinforced concrete, comprising the following components by weight percentage:

[0010] Ether-based water-reducing polycarboxylate superplasticizer mother liquor: 48.0 wt%–52.0 wt%;

[0011] Ester-based slump-retaining polycarboxylate superplasticizer mother liquor: 18.0 wt%–21.0 wt%;

[0012] Aqueous isooctyltriethoxysilane emulsion, 9.5 wt%–11.5 wt%;

[0013] Non-pre-neutralized acid-base swellable acrylate copolymer emulsion, 0.50 wt%–0.70 wt%;

[0014] Prehydrated solution of vegan gum: 3.5 wt%–4.5 wt%;

[0015] Triisopropanolamine 1.2wt%~1.6wt%;

[0016] Sodium gluconate 0.35wt%~0.55wt%;

[0017] Sodium phytate 0.05wt%~0.10wt%;

[0018] Polyether-modified silicone defoamer 0.06wt%~0.10wt%;

[0019] Water-based preservatives: 0.03wt%~0.06wt%;

[0020] Deionized water replenished to 100 wt%;

[0021] The solid content of the ether-based water-reducing polycarboxylate superplasticizer mother liquor, the ester-based slump-retaining polycarboxylate superplasticizer mother liquor, and the aqueous isooctyltriethoxysilane emulsion is 40 wt%. The solid content of the non-pre-neutralized acid-base swellable acrylate copolymer emulsion is 25 wt% to 30 wt%. The mass fraction of the vegan gum in the vegan gum prehydration solution is 1.0 wt%.

[0022] By employing the above technical solutions, the combined use of ether-based water-reducing polycarboxylate superplasticizer mother liquor and ester-based slump-retaining polycarboxylate superplasticizer mother liquor enables steel fiber reinforced concrete mixtures to achieve both initial dispersion performance and good slump expansion retention. The non-pre-neutralized acid-alkali swellable acrylate copolymer emulsion maintains a low viscosity in the low pH environment of the composite admixture product, exhibiting a rheological response upon entering the high pH environment of the cement paste, thereby increasing the yield stress and plastic viscosity of the cement paste system. The combination of Vilan gum pre-hydrated liquid and the non-pre-neutralized acid-alkali swellable acrylate copolymer emulsion helps reduce the bleeding rate and segregation tendency of the mixture, improving the uniformity of steel fiber distribution in the height direction of the mixture. These rheological modulation effects correspond to the segregation resistance and crack prevention properties of steel fiber reinforced concrete.

[0023] The introduction of aqueous isooctyltriethoxysilane emulsion helps reduce the capillary water absorption coefficient and chloride ion migration coefficient of hardened steel fiber reinforced concrete, thereby improving the hardened matrix's resistance to moisture intrusion, chloride ion intrusion, and corrosion and rust prevention properties. Sodium phytate contains multiple phosphate groups, which can form complexes with metal ions, thus enhancing the system's auxiliary effect on improving the corrosion and rust prevention properties of steel fibers. The combination of triisopropanolamine, sodium gluconate, and polycarboxylate superplasticizer mother liquor helps regulate the development of cement paste workability and mechanical properties, enabling the composite admixture to achieve better overall performance in terms of workability, impermeability, corrosion and rust prevention, and crack prevention.

[0024] Preferably, the mass ratio of solids in the mother liquor of the ether-based water-reducing polycarboxylate superplasticizer to solids in the mother liquor of the ester-based slump-retaining polycarboxylate superplasticizer is not less than 2.4:1.

[0025] By adopting the above technical solution, the solid mass ratio of ether-based water-reducing polycarboxylate superplasticizer mother liquor to ester-based slump-retaining polycarboxylate superplasticizer mother liquor is controlled to be no less than 2.4:1, which is beneficial to balance the initial slump expansion and the slump expansion retention performance of the mixture, and reduce the workability loss of steel fiber reinforced concrete mixture during the static process.

[0026] Preferably, the finished product of the composite additive has a pH value of 4.0 to 5.0.

[0027] By adopting the above technical solution, the pH value of the finished composite admixture is controlled within the acidic range, which helps the non-pre-neutralized acid-base swellable acrylate copolymer emulsion maintain a low viscosity during storage. This reduces the risk of premature thickening, local gelation, or decreased fluidity of the finished product during storage, thereby improving the storage stability and dosing operability of the finished composite admixture.

[0028] Preferably, the water-based preservative is Kathon preservative.

[0029] By adopting the above technical solutions, Kathon preservative can inhibit the growth of microorganisms during the storage of composite admixtures, reduce the risk of deterioration of organic components such as vegan gum and sodium gluconate during storage, and improve the storage stability of the finished composite admixture. Water-based preservatives are mainly used to inhibit the growth of microorganisms during the storage of finished composite admixtures, reducing the risk of deterioration during storage. The storage-based preservative effect of water-based preservatives differs from the durability-improving effect of composite admixtures on the corrosion and rust-inhibiting properties of steel fiber reinforced concrete in terms of their target organisms.

[0030] Secondly, the present invention provides a method for preparing a composite admixture adapted to steel fiber reinforced concrete for corrosion prevention, rust inhibition, seepage prevention, and crack prevention, using the following technical solution:

[0031] A method for preparing a composite admixture adapted to steel fiber reinforced concrete for corrosion prevention, rust inhibition, seepage prevention, and crack prevention includes the following steps:

[0032] Step 1: Dissolve all sodium gluconate and all sodium phytate in the first portion of deionized water to obtain a salt solution; then add all triisopropanolamine to the salt solution to prepare a pre-diluted conditioning solution.

[0033] Step 2: Add the vegan gum to the second part of deionized water and hydrate the vegan gum by stirring to obtain a vegan gum prehydrated solution with a vegan gum mass fraction of 1.0 wt%.

[0034] Step 3: Add the third portion of deionized water to the mixing tank equipped with a mechanical stirrer, then add the ether-based water-reducing polycarboxylate superplasticizer mother liquor and the ester-based slump-retaining polycarboxylate superplasticizer mother liquor in sequence, and stir at a speed of 60 r / min to 100 r / min for 10 min; then add the vegan gum pre-hydrated liquid obtained in Step 2, and stir at a speed of 60 r / min to 100 r / min for 10 min; finally add the non-pre-neutralized acid-base swellable acrylate copolymer emulsion and the polyether-modified silicone defoamer, and stir at a speed of 40 r / min to 60 r / min for 10 min to obtain an acidic mixture;

[0035] Step 4: While maintaining a stirring speed of 40 r / min to 60 r / min, add the pre-diluted conditioning solution obtained in step 1 to the acidic mixture. After the addition is completed, continue stirring until the mixture is homogeneous.

[0036] Step 5: Insert the feed pipe into the mixing tank below the liquid surface and add the aqueous isooctyltriethoxysilane emulsion while stirring at a speed of 30 r / min to 50 r / min.

[0037] Step 6: After the aqueous isooctyltriethoxysilane emulsion is added, maintain the stirring speed at 30 r / min to 50 r / min, add the aqueous preservative and replenish the remaining deionized water, continue stirring until the mixture is uniform, then stop stirring and let it stand for 30 min to 60 min. The composite additive is then discharged.

[0038] The second part of deionized water and vegan gum together form a vegan gum pre-hydration solution, and the second part of deionized water is included in the mass of the vegan gum pre-hydration solution; the first part of deionized water, the third part of deionized water and the remaining part of deionized water together constitute the deionized water used to make up to 100 wt% in the composite admixture.

[0039] By employing the above technical solutions, pre-dispersing and hydrating vilanin helps reduce the risk of agglomerated particles when vilanin is directly added to the compounding system, thus improving its dispersion uniformity in the compound additives. Pre-preparing sodium gluconate, sodium phytate, and triisopropanolamine into a pre-diluted conditioning solution helps reduce localized high pH and high salt concentration disturbances caused by their direct addition to the main system, resulting in a more stable subsequent compounding process.

[0040] When compounding the main system, first add the ether-based water-reducing polycarboxylate superplasticizer mother liquor and the ester-based slump-retaining polycarboxylate superplasticizer mother liquor, then add the vegan gum pre-hydrated liquid and the non-pre-neutralized acid-base swellable acrylate copolymer emulsion. This allows the vegan gum pre-hydrated liquid and the non-pre-neutralized acid-base swellable acrylate copolymer emulsion to be dispersed in a low-pH continuous aqueous phase, which helps reduce the risk of local thickening or gel particle formation. Subsequently, the pre-diluted conditioning liquid is added to the acidic mixture to keep the finished compound additive in an acidic state, thereby improving the fluidity and storage stability of the finished product.

[0041] When adding aqueous isooctyltriethoxysilane emulsion, the feed nozzle should be inserted below the liquid surface in the mixing tank, and dispersion should be carried out at a low stirring speed. This helps to reduce air entrainment and local enrichment on the liquid surface, thereby reducing the risk of emulsification or stratification of the silane emulsion during the compounding process and improving the dispersion uniformity of the silane emulsion in the composite admixture system.

[0042] Preferably, in step one, the mass percentage concentration of triisopropanolamine in the pre-diluted conditioning solution is 10wt% to 23wt%.

[0043] By adopting the above technical solution, the mass percentage concentration of triisopropanolamine in the pre-diluted conditioning solution is controlled within the above range, which helps to reduce local pH disturbance when it is added to the acidic mixture and reduces the risk of local thickening or gel particle formation in non-pre-neutralized acid-base swellable acrylate copolymer emulsion.

[0044] Preferably, in step three, before adding the non-pre-neutralized acid-base swellable acrylate copolymer emulsion, the pH value of the liquid in the mixing tank is 3.5 to 5.2; during the addition of the non-pre-neutralized acid-base swellable acrylate copolymer emulsion, the pH value of the liquid in the mixing tank is less than or equal to 5.5.

[0045] By adopting the above technical solution, the system is kept in an acidic range before and after adding the non-pre-neutralized acid-base swellable acrylate copolymer emulsion. This helps the emulsion maintain a low viscosity dispersion state during the compounding process and reduces the risk of local thickening, gel particles, or decreased fluidity during the compounding process.

[0046] Preferably, in step four, the pH value of the liquid in the mixing tank is controlled to be 4.0 to 5.5 during and after the addition of the pre-diluted conditioning solution.

[0047] By adopting the above technical solution, when adding the pre-diluted conditioning solution containing triisopropanolamine, the pH value of the mixture is controlled at 4.0-5.5, which is beneficial to maintain the acidic state of the finished compound admixture. This allows the non-pre-neutralized acid-base swellable acrylate copolymer emulsion to maintain a low viscosity during the finished product storage stage, thereby improving the storage stability and feeding operability of the finished compound admixture.

[0048] Preferably, in step five, the feeding rate of the aqueous isooctyltriethoxysilane emulsion is less than or equal to 0.8 wt% / min of the total mass of the composite admixture.

[0049] By adopting the above technical solution, controlling the feeding rate of the aqueous isooctyltriethoxysilane emulsion is beneficial to reducing the risk of emulsion separation, surface oil floating or stratification caused by excessively high local silane emulsion concentration, and improving the dispersion uniformity of the aqueous isooctyltriethoxysilane emulsion in the composite admixture system.

[0050] Preferably, in steps three to six, the temperature of the liquid in the mixing tank is controlled at 23℃~27℃; the stirring temperature in step two is 20℃~30℃; when the temperature of the liquid in the mixing tank rises abnormally to more than 30℃ in steps three to six, external cooling water is used to cool the mixing tank until the temperature of the liquid in the mixing tank returns to 23℃~27℃.

[0051] By adopting the above technical solution to control the temperature during the compounding process, it is beneficial to reduce the impact of temperature rise on the dispersion stability of polycarboxylate superplasticizer mother liquor, non-pre-neutralized acid-base swellable acrylate copolymer emulsion, Weylan gum prehydrated liquid, and water-based isooctyltriethoxysilane emulsion, thereby reducing the risk of emulsion separation, local thickening, or decreased fluidity during the compounding process.

[0052] This invention provides a composite admixture suitable for steel fiber reinforced concrete, which is corrosion-resistant, rust-inhibiting, impermeable, and crack-resistant. It has the following beneficial effects:

[0053] 1. This invention combines ether-based water-reducing polycarboxylate superplasticizer mother liquor, ester-based slump-retaining polycarboxylate superplasticizer mother liquor, non-pre-neutralized acid-base swellable acrylate copolymer emulsion, and Weilan gum pre-hydration liquid to maintain the flowability of the composite admixture in a low-pH finished product state and exhibits rheological regulation in the cement paste system. This is beneficial for reducing the bleeding rate and segregation tendency of steel fiber reinforced concrete mixtures and improving the uniformity of steel fiber distribution.

[0054] 2. This invention combines ether-based water-reducing polycarboxylate superplasticizer mother liquor with ester-based slump-retaining polycarboxylate superplasticizer mother liquor, enabling steel fiber reinforced concrete mixtures to achieve good slump expansion retention performance while obtaining initial workability, which is beneficial to improving workability over time.

[0055] 3. The present invention introduces an aqueous isooctyltriethoxysilane emulsion, which is beneficial to reducing the capillary water absorption coefficient and chloride ion migration coefficient of hardened steel fiber concrete, thereby improving its resistance to water intrusion, chloride ion intrusion and corrosion and rust prevention properties; at the same time, the addition of sodium phytate and triisopropanolamine is beneficial to further improve the durability-related properties of the composite admixture system.

[0056] 4. By setting a pre-diluted conditioning solution, limiting the order of rheological component addition, and using an aqueous isooctyltriethoxysilane emulsion for submerged addition, this invention reduces the impact of local high pH, ​​local high salt concentration, and emulsion instability on the system uniformity during the compounding process, which is beneficial to improving the storage stability and use stability of the finished compound admixture. Attached Figure Description

[0057] Figure 1 This is a graph showing the change in slump expansion retention rate of steel fiber reinforced concrete mixture with static time in Test Example 2 of the present invention.

[0058] Figure 2 This is a schematic diagram of the layered sampling test of steel fiber reinforced concrete in Test Example 4 of the present invention. Detailed Implementation

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0060] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Raw materials not specifically mentioned are all commercially available industrial-grade products, and reagents not specifically mentioned are all commercially available analytical grade or higher-grade products.

[0061] The mother liquor of the ether-based water-reducing polycarboxylate superplasticizer has a solid content of 40 wt% and is obtained by copolymerization of isopentenyl polyoxyethylene ether macromonomer and unsaturated carboxylic acid monomer. The pH is 3.5 to 6.0.

[0062] The mother liquor of ester-based slump-retaining polycarboxylate superplasticizer has a solid content of 40 wt% and is obtained by copolymerization of polyethylene glycol monomethyl ether acrylate macromonomers and unsaturated carboxylic acid monomers. The pH is 3.5–6.0.

[0063] The non-pre-neutralized acid-base swellable acrylate copolymer emulsion (hereinafter referred to as "base swellable acrylate copolymer emulsion") has a solid content of 30 wt%. It is an anionic acrylate copolymer aqueous dispersion containing free carboxyl groups. The initial pH is 2.5 to 4.0. It is in an unneutralized acidic state and can undergo alkali swelling and viscosity response under alkaline conditions.

[0064] Vegan gum, CAS No. 96949-22-3, also known as Vegan gum, is a high molecular weight polysaccharide produced by microbial fermentation, with an average molecular weight greater than 1,000,000.

[0065] Triisopropanolamine, CAS No. 122-20-5.

[0066] Sodium gluconate, CAS No. 527-07-1.

[0067] Sodium phytate, CAS No. 14306-25-3.

[0068] Aqueous isooctyltriethoxysilane emulsion, oil-in-water emulsion, solid content 40wt%, active ingredient is isooctyltriethoxysilane, CAS No. 35435-21-3.

[0069] Polyether-modified silicone defoamer, commercially available defoamer for admixture use, 100% solids content.

[0070] Kathon preservative, the active ingredients are a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, wherein 5-chloro-2-methyl-4-isothiazolin-3-one CAS number 26172-55-4 and 2-methyl-4-isothiazolin-3-one CAS number 2682-20-4, and the content of active ingredients in the mixture is 1.5 wt%.

[0071] Deionized water with a conductivity not exceeding 10 μS / cm.

[0072] Unless otherwise stated, all pH values ​​mentioned in this instruction manual were measured using a calibrated pH meter; the same set of comparative data was measured under the same temperature conditions.

[0073] Preparation example:

[0074] This preparation example provides a method for preparing a prehydrated solution of vegan gum, including the following steps:

[0075] (1) At 25°C, add 990.0g of deionized water to a preparation tank equipped with a dispersion plate, turn on the stirring and set the speed to 400r / min.

[0076] (2) While maintaining a stirring speed of 400 r / min, add 10.0 g of Weylan gum to water at a feeding rate of 2.0 g / min.

[0077] (3) After adding the vegan gum, continue stirring at 400 r / min for 45 min to fully disperse and hydrate the vegan gum.

[0078] (4) Then turn off the stirring and let the liquid stand at 25°C for 30 minutes to obtain a prehydrated solution of 1.0 wt% vegan gum.

[0079] Example 1:

[0080] This embodiment provides a method for preparing a composite admixture suitable for steel fiber reinforced concrete that is corrosion-resistant, rust-inhibiting, impermeable, and crack-resistant. The method, based on a total preparation weight of 1000.0g, includes the following steps:

[0081] (1) At 25°C, 4.5g sodium gluconate and 0.8g sodium phytate were added to 100.0g deionized water and stirred at 150r / min until dissolved; then 14.0g triisopropanolamine was added and stirring continued. The stirring time for the entire preparation process was 15min, and a pre-diluted conditioning solution was obtained.

[0082] (2) Add 28.5g of deionized water to a mixing tank equipped with a mechanical stirrer, and add 500.0g of ether-based water-reducing polycarboxylate superplasticizer mother liquor and 200.0g of ester-based slump-retaining polycarboxylate superplasticizer mother liquor in sequence at a feeding rate of 150.0g / min. Set the stirring speed to 80r / min and stir for 10min. Use a pH meter to measure and record the pH of the mixture.

[0083] (3) Add 40.0g of the prehydrated solution of the preparation example to the mixing tank at a feeding rate of 5.0g / min, and continue stirring at a speed of 80r / min for 10min.

[0084] (4) Adjust the stirring speed to 50 r / min and add 6.0 g of alkali-swellable acrylate copolymer emulsion to the mixing tank at a feeding rate of 1.0 g / min; then add 0.8 g of polyether modified silicone defoamer at once and maintain stirring at 50 r / min for 10 min.

[0085] (5) At a stirring speed of 50 r / min, the pre-diluted conditioning solution prepared above is added to the mixing tank at a feeding rate of 10.0 g / min. After the feeding is completed, continue stirring for 5 min.

[0086] (6) Insert the feed pipe into the mixing tank below the liquid surface and add 105.0 g of aqueous isooctyltriethoxysilane emulsion at a feeding rate of 8.0 g / min. After the feeding is completed, add 0.4 g of Kathon preservative at once and continue stirring at a speed of 50 r / min for 10 min.

[0087] (7) Turn off the stirring, let the liquid stand at 25°C for 45 minutes, and then discharge the material to obtain the finished compound additive.

[0088] (8) The temperature of the liquid material in the above preparation process is controlled at 25±2℃. When the temperature of the liquid material exceeds 30℃, the feeding is suspended and the mixing tank is cooled by external cooling water until the temperature of the liquid material recovers to 23℃~27℃ before continuing the operation.

[0089] Example 2:

[0090] This embodiment provides a method for preparing a composite admixture suitable for steel fiber reinforced concrete that is corrosion-resistant, rust-inhibiting, impermeable, and crack-resistant. The method, based on a total preparation weight of 1000.0g, includes the following steps:

[0091] (1) At 25°C, 3.5g sodium gluconate and 0.5g sodium phytate were added to 100.0g deionized water and stirred at 150r / min until dissolved; then 12.0g triisopropanolamine was added and stirring continued. The stirring time for the entire preparation process was 15min, and a pre-diluted conditioning solution was obtained.

[0092] (2) Add 88.1g of deionized water to a mixing tank equipped with a mechanical stirrer, and add 480.0g of ether-based water-reducing polycarboxylate superplasticizer mother liquor and 180.0g of ester-based slump-retaining polycarboxylate superplasticizer mother liquor in sequence at a feeding rate of 150.0g / min. Set the stirring speed to 80r / min and stir for 10min. Use a pH meter to measure and record the pH of the mixture.

[0093] (3) Add 35.0 g of the prehydrated solution of the preparation example to the mixing tank at a feeding rate of 5.0 g / min, and continue stirring at a speed of 80 r / min for 10 min.

[0094] (4) Adjust the stirring speed to 50 r / min and add 5.0 g of alkali-swellable acrylate copolymer emulsion to the mixing tank at a feeding rate of 1.0 g / min; then add 0.6 g of polyether modified silicone defoamer at once and maintain stirring at 50 r / min for 10 min.

[0095] (5) At a stirring speed of 50 r / min, the pre-diluted conditioning solution prepared above is added to the mixing tank at a feeding rate of 10.0 g / min. After the feeding is completed, continue stirring for 5 min.

[0096] (6) Insert the feed pipe into the mixing tank below the liquid surface and add 95.0 g of aqueous isooctyltriethoxysilane emulsion at a feeding rate of 8.0 g / min. After the feeding is completed, add 0.3 g of Kathon preservative at once and continue stirring at a speed of 50 r / min for 10 min.

[0097] (7) Turn off the stirring, let the liquid stand at 25°C for 45 minutes, and then discharge the material to obtain the finished compound additive.

[0098] (8) The temperature of the liquid material in the above preparation process is controlled at 25±2℃. When the temperature of the liquid material exceeds 30℃, the feeding is suspended and the mixing tank is cooled by external cooling water until the temperature of the liquid material recovers to 23℃~27℃ before continuing the operation.

[0099] Example 3:

[0100] This embodiment provides a method for preparing a composite admixture suitable for steel fiber reinforced concrete that is corrosion-resistant, rust-inhibiting, impermeable, and crack-resistant. The method, based on a total preparation weight of 1000.0g, includes the following steps:

[0101] (1) At 25°C, 5.5g sodium gluconate and 1.0g sodium phytate were added to 50.0g deionized water and stirred at 150r / min until dissolved; then 16.0g triisopropanolamine was added and stirring continued. The stirring time for the entire preparation process was 15min, and a pre-diluted conditioning solution was obtained.

[0102] (2) Add 28.9g of deionized water to a mixing tank equipped with a mechanical stirrer, and add 520.0g of ether-based water-reducing polycarboxylate superplasticizer mother liquor and 210.0g of ester-based slump-retaining polycarboxylate superplasticizer mother liquor in sequence at a feeding rate of 150.0g / min. Set the stirring speed to 80r / min and stir for 10min. Use a pH meter to measure and record the pH of the mixture.

[0103] (3) Add 45.0 g of the prehydrated solution of the preparation example to the mixing tank at a feeding rate of 5.0 g / min, and continue stirring at a speed of 80 r / min for 10 min.

[0104] (4) Adjust the stirring speed to 50 r / min and add 7.0 g of alkali-swellable acrylate copolymer emulsion to the mixing tank at a feeding rate of 1.0 g / min; then add 1.0 g of polyether modified silicone defoamer at once and maintain stirring at 50 r / min for 10 min.

[0105] (5) At a stirring speed of 50 r / min, the pre-diluted conditioning solution prepared above is added to the mixing tank at a feeding rate of 10.0 g / min. After the feeding is completed, continue stirring for 5 min.

[0106] (6) Insert the feed pipe into the mixing tank below the liquid surface and add 115.0 g of aqueous isooctyltriethoxysilane emulsion at a feeding rate of 8.0 g / min. After the feeding is completed, add 0.6 g of Kathon preservative at once and continue stirring at a speed of 50 r / min for 10 min.

[0107] (7) Turn off the stirring, let the liquid stand at 25°C for 45 minutes, and then discharge the material to obtain the finished compound additive.

[0108] (8) The temperature of the liquid material in the above preparation process is controlled at 25±2℃. When the temperature of the liquid material exceeds 30℃, the feeding is suspended and the mixing tank is cooled by external cooling water until the temperature of the liquid material recovers to 23℃~27℃ before continuing the operation.

[0109] Comparative Example 1:

[0110] The difference compared to Example 1 is that no pre-diluted conditioning solution was prepared.

[0111] The 100.0g of deionized water used in Example 1 for preparing the pre-diluted conditioning solution was directly added to the initial water volume of the mixing tank.

[0112] After adding the alkali-swellable acrylate copolymer emulsion and polyether-modified silicone defoamer and stirring for 10 minutes, the stirring speed was maintained at 50 rpm. First, 14.0 g of triisopropanolamine was added to the mixing tank in one go over 20 seconds, followed by 4.5 g of sodium gluconate solid and 0.8 g of sodium phytate solid, each added to the mixing tank over 30 seconds. Stirring continued for 10 minutes after the additions were complete. The amounts of other components and process conditions were the same as in Example 1.

[0113] Comparative Example 2:

[0114] Compared with Example 1, the difference lies in the order of addition of the pre-diluted conditioning solution, the vegan gum pre-hydration solution, and the alkali-swellable acrylate copolymer emulsion.

[0115] Add deionized water, ether-based water-reducing polycarboxylate superplasticizer mother liquor, and ester-based slump-retaining polycarboxylate superplasticizer mother liquor to a mixing tank and stir for 10 min. Then, add the pre-diluted conditioning solution at a feeding rate of 10.0 g / min. After the feeding is complete, maintain stirring at 50 r / min for 5 min.

[0116] The prepared venetian gum prehydrate solution was then added at a feeding rate of 5.0 g / min and stirred for 10 min. Next, the alkali-swellable acrylate copolymer emulsion was added at a feeding rate of 1.0 g / min, followed by the addition of a single-use polyether-modified silicone defoamer, and stirring continued for another 10 min. The amounts of other components and process conditions were the same as in Example 1.

[0117] Comparative Example 3:

[0118] Compared to Example 1, the difference is that the alkali-swellable acrylate copolymer emulsion was not added; instead, it was replaced with 6.0 g of deionized water. The amounts of all other components and the process conditions were the same as in Example 1.

[0119] Comparative Example 4:

[0120] Compared with Example 1, the difference is that the prehydrated solution of vellini prepared in the preparation example was not added, but replaced with 40.0 g of deionized water. The amounts of other components and process conditions are the same as in Example 1.

[0121] Comparative Example 5:

[0122] Compared to Example 1, the difference is that ester-based slump-retaining polycarboxylate superplasticizer mother liquor was not added; instead, it was replaced with an equal mass of ether-based superplasticizer mother liquor, meaning the total amount of ether-based superplasticizer mother liquor added was changed to 700.0 g. The amounts of other components and process conditions remained the same as in Example 1.

[0123] Comparative Example 6:

[0124] Compared to Example 1, the difference is that the aqueous isooctyltriethoxysilane emulsion was not added; instead, it was replaced with 105.0 g of deionized water. The amounts of all other components and the process conditions were the same as in Example 1.

[0125] Comparative Example 7:

[0126] The difference compared to Example 1 is that the feeding method of the aqueous isooctyltriethoxysilane emulsion was changed.

[0127] The submerged addition method in Example 1 was changed to dropwise addition above the liquid surface. Specifically, the feed inlet was placed 5-10 cm above the surface of the composite admixture solution, and the aqueous isooctyltriethoxysilane emulsion was added dropwise at a feeding rate of 8.0 g / min. The dosage of other components and process conditions were the same as in Example 1.

[0128] Test Example 1:

[0129] Test objective: To verify the flow state of the composite admixture of the present invention under low pH conditions, and to examine its rheological response under high pH conditions and in cement slurry systems.

[0130] The experimental steps are as follows:

[0131] (1) The composite admixture samples prepared in Examples 1 to 3 and Comparative Example 3 were measured respectively, and the pH value of the finished product of each sample was tested using a pH meter. The initial apparent viscosity of each sample was tested using a rotational rheometer at 25±1℃, and the shear rate was read at 50s. -1 Test values ​​under the given conditions.

[0132] (2) Auxiliary pH response test of the admixture dilution solution. The samples obtained in Examples 1 to 3 and Comparative Example 3 were diluted and mixed with deionized water at a mass ratio of 1:4. Equal masses of the dilution solution were taken, and their pH values ​​were adjusted to 5.0, 7.0, 10.0, and 12.0 using 0.1 mol / L NaOH solution. After adjustment, each group of samples was replenished with deionized water to the same mass. After each group of samples was allowed to stand at 25±1℃ for 30 min, a rotational rheometer was used to measure the pH from 0.1 to 100 s. -1 The scan was performed within the range of shear rates, and the shear rate was recorded for 50 seconds. -1 The apparent viscosity value at that time.

[0133] (3) Weigh the same batch of standard cement and water at a water-cement ratio of 0.35, and add the composite admixtures of Examples 1 to 3 and Comparative Example 3 to prepare standard cement slurry. The dosage of each group of admixtures is uniformly calculated as 1.2% of the mass of cementitious materials. The total water consumption of each group of cement slurry is kept consistent during the preparation process, and the water introduced by the admixtures is included in the total water consumption.

[0134] (4) After the cement slurry is mixed, its rheological properties are tested using a rotational rheometer at time points of 5 min, 30 min, and 60 min after standing. Before each test, the rotor is set to rotate at 100 s... -1 Pre-shear at a shear rate of 30s, let stand for 30s, and then perform a shearing at a rate of 0.1–100s. -1 Shear rate scans were performed within the specified range. The acquired shear stress and shear rate data were linearly fitted using the Bingham plastic model to calculate the yield stress and plastic viscosity of the system at the corresponding time points.

[0135] The experimental results are shown in Table 1 and Table 2.

[0136] Table 1. Apparent viscosity of the composite admixture dilution at different pH values:

[0137] Test object apparent viscosity at pH 5.0 / mPa·s apparent viscosity at pH 7.0 / mPa·s Apparent viscosity at pH 10.0 / mPa·s apparent viscosity at pH 12.0 / mPa·s Example 1 Diluent 23.4 41.7 114.2 258.9 Example 2 Diluent 21.6 38.3 108.5 243.6 Example 3 Diluent 25.1 44.2 123.8 275.4 Comparative Example 3 Diluent 12.8 13.5 14.1 14.7

[0138] Note: The apparent viscosity in Table 1 is based on a shear rate of 50 s. -1 Test values ​​under the given conditions.

[0139] Table 2. Physicochemical parameters of the composite admixture and rheological test results of the cement paste system:

[0140] Test object Finished pH Initial apparent viscosity / mPa·s 5min yield stress / Pa 30min yield stress / Pa 60min yield stress / Pa 5-minute plastic viscosity / Pa·s 30-minute plastic viscosity / Pa·s 60-minute plastic viscosity / Pa·s Example 1 4.35 167.4 24.6 28.1 35.8 0.86 0.94 1.12 Example 2 4.42 158.9 22.3 26.5 31.4 0.79 0.88 1.05 Example 3 4.56 172.1 27.8 31.2 38.6 0.95 1.08 1.26 Comparative Example 3 4.31 64.5 4.2 4.8 6.1 0.22 0.27 0.35

[0141] Based on the results shown in Tables 1 and 2, the pH of the composite admixtures prepared in Examples 1 to 3 was 4.35–4.56, and the pH was within the range of 50 s⁻¹. -1 The initial apparent viscosity under the given conditions was 158.9–172.1 mPa·s. These results indicate that the composite additive obtained in the examples remained flowable in the low pH finished product state, and no irreversible gelation or significant over-thickening was observed.

[0142] As shown in Table 1, the apparent viscosity of the composite admixture diluents in Examples 1 to 3 increased with increasing pH. For example, the apparent viscosity of the diluent in Example 1 was 23.4 mPa·s at pH 5.0, increasing to 258.9 mPa·s at pH 12.0. In contrast, the apparent viscosity of the diluent in Comparative Example 3 ranged from 12.8 to 14.7 mPa·s within the pH range of 5.0 to 12.0, showing a smaller variation. This result indicates that the introduction of the alkali-swellable acrylate copolymer emulsion resulted in a more pronounced viscosity response in the composite admixture diluent system under high pH conditions.

[0143] Table 2 shows that after incorporating the composite admixtures obtained in Examples 1 to 3 into the standard cement slurry, the cement slurry system exhibited higher yield stress and plastic viscosity. The yield stress of Examples 1 to 3 was 22.3–27.8 Pa at 5 min, increasing to 31.4–38.6 Pa at 60 min; the corresponding plastic viscosity was 0.79–1.26 Pa·s. The yield stress of Comparative Example 3, without the addition of alkali-swellable acrylate copolymer emulsion, was 4.2–6.1 Pa from 5 min to 60 min, and the plastic viscosity was 0.22–0.35 Pa·s.

[0144] The above results indicate that the introduction of alkali-swellable acrylate copolymer emulsions enables the composite admixture to exhibit a more significant rheological moderating effect under high pH conditions and in cement slurry systems.

[0145] In subsequent test examples 2 through 5, the steel fiber reinforced concrete used the same standard mix proportion. The cement content was 315 kg / m³. 3 The fly ash usage is 85 kg / m³ 3 The dosage of slag powder is 105 kg / m³. 3 The amount of manufactured sand used is 824 kg / m³. 3 The amount of crushed stone used is 886 kg / m³. 3 The mixing water dosage is 168 kg / m³ 3The steel fiber volume fraction was 0.6%, and the composite admixture was 1.6% of the total mass of the cementitious material. The steel fibers were hook-shaped with a length of 35 mm, an equivalent diameter of 0.55 mm, an aspect ratio of 64, and a tensile strength of 1150 MPa. All test groups used the same baseline mix proportions, and the moisture introduced by the composite admixture was included in the total water consumption.

[0146] In the above-mentioned standard mix proportion, the total amount of cementitious material is 505 kg / m³. 3 The water-to-binder ratio is 0.33, and the sand content is 48.2%.

[0147] Test Example 2:

[0148] Test objective: To investigate the effect of ester-based slump-retaining polycarboxylate superplasticizer mother liquor on the slump spread retention performance of steel fiber reinforced concrete mixtures.

[0149] The experimental steps are as follows:

[0150] (1) Weigh cement, fly ash, slag powder, manufactured sand, crushed stone, and mixing water according to a unified standard mix proportion, and prepare steel fibers with the same volume. Measure the composite admixtures prepared in Examples 1 to 3 and Comparative Example 5 respectively, and calculate the admixture dosage of each group according to a fixed proportion of the total mass of cementitious materials. The total water consumption of each group of concrete is kept consistent, and the water introduced by the composite admixture is included in the total water consumption.

[0151] (2) The weighed powder materials and aggregates are put into a forced single-shaft concrete mixer and dry-mixed for 30s; then the mixture of mixing water and composite admixture is added and wet-mixed for 60s; while continuing to mix, steel fibers are added evenly within 60s; after the steel fibers are added, continue mixing for 90s, and then discharge the material.

[0152] (3) According to the relevant provisions of GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the initial slump flow of fresh steel fiber reinforced concrete was tested. The diameters of the spread surface in two mutually perpendicular directions were measured, and the average value was taken as the slump flow.

[0153] (4) Each batch of concrete was divided into three portions after one mixing, and used for initial, 60-minute, and 120-minute slump flow tests, respectively. The samples used for the 60-minute and 120-minute tests were placed in non-absorbent containers and covered with a damp cloth to reduce moisture evaporation. After reaching the corresponding time point, the samples were manually stirred for 30 seconds, and the slump flow was measured again.

[0154] (5) Calculate the collapse spread retention rate using the following formula:

[0155] Collapse expansion retention rate = (Collapse expansion at corresponding time / Initial collapse expansion) × 100%.

[0156] The experimental results are shown in Table 3.

[0157] Table 3. Test results of slump flow and slump flow retention rate of steel fiber reinforced concrete mixture:

[0158] Test object Initial collapse spread / mm 60-minute slump spread / mm 120min slump spread / mm 60-minute collapse spread retention rate / % 120-minute collapse spread retention rate / % Example 1 543 521 490 96 90.2 Example 2 537 519 495 96.6 92.2 Example 3 549 533 502 97.1 91.4 Comparative Example 5 532 393 274 73.9 51.5

[0159] According to Table 3 and Figure 1 The results show that the initial slump expansion of the steel fiber reinforced concrete prepared in Examples 1 to 3 was 537–549 mm. After standing for 120 min, the slump expansion retention rate of Examples 1 to 3 was 90.2%–92.2%, indicating that the composite admixtures obtained in each example have good slump expansion retention performance under the reference mix proportion conditions.

[0160] Comparative Example 5 did not include ester-based slump-retaining polycarboxylate superplasticizer stock solution; instead, it was replaced with an equal mass of ether-based superplasticizer stock solution. The initial slump flow of this concrete group was 532 mm, similar to that of the Example group. After standing for 60 minutes, its slump flow decreased to 393 mm, and after standing for 120 minutes, it decreased to 274 mm, corresponding to a slump flow retention rate of 51.5% after 120 minutes.

[0161] The above results indicate that, under the same reference mix proportion and the same admixture dosage, the introduction of ester-based slump-retaining polycarboxylate superplasticizer mother liquor contributes to the slump expansion retention performance of steel fiber reinforced concrete mixtures, which is beneficial to improving the workability retention capacity of steel fiber reinforced concrete mixtures over time.

[0162] Test Example 3:

[0163] Test objective: To investigate the effects of the order of addition of pre-diluted conditioning solution, rheology components, and the submerged addition method of aqueous isooctyltriethoxysilane emulsion on the appearance uniformity, storage stability, and flowability of the finished composite admixture.

[0164] The experimental steps are as follows:

[0165] (1) After the composite additives of Examples 1 to 3 and Comparative Examples 1, 2 and 7 were prepared, samples of each group were immediately extracted and transferred to transparent glass containers. The appearance of the samples was observed under natural light, and it was recorded whether there were gel particles, flocculated suspended matter, surface oil, emulsion separation or obvious air entrapment in the liquid.

[0166] (2) Referring to the relevant provisions of GB / T 8077-2023 "Test Method for Homogeneity of Concrete Admixtures", the pH value of each group of samples before storage was tested. Additionally, at 25±1℃, a rotational rheometer was used to test the pH value of each sample before storage for 50 seconds. -1The initial apparent viscosity of each sample was tested at a fixed shear rate. Three parallel samples were set up for each group, and the average value of the test results was taken.

[0167] (3) Divide each group of samples into two portions and place them in sealed polyethylene storage bottles. Store them at 25±2℃ and 40±2℃ respectively. Observe the appearance of the samples at 7 days, 28 days and 90 days and record whether stratification, emulsification, gel particles or obvious flocculation occur. Table 4 shows the representative test results after 90 days of accelerated storage at 40℃.

[0168] (4) After 90 days of storage, the samples stored at 40℃ were removed and placed at 25±1℃ to return to room temperature. The sealed bottle was then opened, and the appearance of the samples was observed and recorded. The pH value after storage was tested using a pH meter, and the pH was measured in 50-second intervals. -1 The apparent viscosity after storage was determined by a fixed shear rate.

[0169] (5) Calculate the viscosity change rate of each group of samples using the following formula:

[0170] Viscosity change rate = |Apparent viscosity after storage - Initial apparent viscosity| / Initial apparent viscosity × 100%.

[0171] The experimental results are shown in Table 4.

[0172] Table 4. Physical properties and stability test results of the composite admixture after 90 days of storage at 40℃:

[0173] Test object pH before storage Initial appearance status Initial apparent viscosity / mPa·s pH after 90 days of storage at 40℃ Appearance after 90 days of storage at 40℃ Apparent viscosity after 90 days of storage at 40℃ / mPa·s viscosity change rate / % Example 1 4.35 A homogeneous emulsion with a slight bluish tint and no visible particles. 167.4 4.32 Homogeneous emulsion, with no obvious stratification 173.2 3.46 Example 2 4.42 A homogeneous emulsion with a slight bluish tint and no visible particles. 158.9 4.38 A homogeneous emulsion, free of gel. 165.6 4.22 Example 3 4.56 A homogeneous emulsion with a slight bluish tint and no visible particles. 172.1 4.51 A homogeneous emulsion with no surface oil. 176.5 2.56 Comparative Example 1 4.47 Localized weak flocculation, with a small amount of microbubbles 194.2 4.39 Sedimentation appeared at the bottom, with slight emulsification. 221.7 14.16 Comparative Example 2 4.58 Scattered transparent gel clumps exist 246.8 4.46 Gel agglomerates expand, and fluidity decreases. 323.5 31.08 Comparative Example 7 4.36 A thin layer of milky white floating oil is present on the surface. 181.3 4.28 Obvious oil-water separation, with emulsion in the upper layer. 247.9 36.73

[0174] According to the results shown in Table 4, the composite additives of Examples 1 to 3 were all in a homogeneous emulsion state after preparation, with a slight bluish tint, and no visible gel clumps or flocculated suspensions were observed; their initial apparent viscosity was 158.9–172.1 mPa·s. After being stored at 40°C for 90 days, the samples of Examples 1 to 3 still maintained a homogeneous state, and no obvious stratification, surface oil floating, or gel precipitation was observed; their pH value changed little, and the viscosity change rate was 2.56%–4.22%.

[0175] The above results indicate that the dilution and dispersion effect of the pre-diluted conditioning solution, the order of addition of rheological components, and the submerged addition method of the aqueous isooctyltriethoxysilane emulsion all affect the appearance and viscosity stability of the composite additive product under accelerated storage conditions. This process combination is beneficial in reducing the disturbance of local high pH and local high salt concentration on the dispersion state of polymer emulsions and silane emulsions.

[0176] In contrast, Comparative Example 1, without a pre-diluted conditioning solution, showed localized weak flocculation in the initial preparation stage. After 90 days of storage at 40°C, sedimentation appeared at the bottom accompanied by slight emulsification, with a viscosity change rate of 14.16%. Comparative Example 2, by changing the order of addition of the pre-diluted conditioning solution, vilan gum prehydration solution, and alkali-swellable acrylate copolymer emulsion, showed scattered transparent gel clumps in the initial preparation stage. After storage, the gel aggregation phenomenon worsened, with a viscosity change rate of 31.08%. Comparative Example 7, by changing the addition method of the aqueous isooctyltriethoxysilane emulsion from submerged to dropwise from above the liquid surface, showed a thin layer of milky white floating oil in the initial preparation stage. After storage, oil-water separation and upper emulsification occurred, with a viscosity change rate of 36.73%.

[0177] The comparison results above show that the order of addition of the pre-diluted conditioning solution, the rheological components, and the method of adding the aqueous isooctyltriethoxysilane emulsion all affect the storage stability of the composite admixture product. Compared with the comparative example with different process conditions, the composite admixture obtained in the example showed a lower viscosity change rate and better appearance uniformity after 90 days of accelerated storage at 40°C.

[0178] Test Example 4:

[0179] Test objective: To investigate the effects of alkali-swellable acrylate copolymer emulsion, Weylan gum prehydrate, and ester-based slump-preserving polycarboxylate superplasticizer mother liquor on the workability, segregation resistance, and uniformity of steel fiber distribution of steel fiber reinforced concrete mixtures, and to evaluate their role in the crack-resistant properties of steel fiber reinforced concrete mixtures.

[0180] The experimental steps are as follows:

[0181] (1) Weigh each component according to a unified standard mix proportion, and prepare steel fiber reinforced concrete mixtures using the composite admixtures prepared in Examples 1 to 3 and Comparative Examples 3, 4 and 5, respectively, according to the same mixing regime. The cementitious material composition, water-cement ratio, sand ratio, steel fiber type, steel fiber volume content, composite admixture content and total water content of each concrete group are kept consistent, and the water introduced by the composite admixture is included in the total water content.

[0182] (2) In accordance with the relevant provisions of GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", take freshly mixed steel fiber reinforced concrete and test its initial slump spread. Use an air content meter to determine the air content of the mixture and make aggregate correction according to the standard requirements.

[0183] (3) The bleeding rate under normal pressure was tested according to the relevant methods in GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". A portion of the mixture was loaded into a covered volumetric cylinder, treated with the same loading and compaction regime, and left to stand. The surface bleeding water was periodically absorbed until no more bleeding occurred. The cumulative bleeding amount was included in the bleeding rate calculation. The total water content of the concrete included the mixing water and the water introduced by the composite admixture.

[0184] (4) Measure the freshly mixed concrete and fill it into a cylindrical container with an inner diameter of 150 mm and a height of 300 mm. Mark the 100 mm and 200 mm height lines on the inner wall of the container beforehand. After filling, scrape the surface smooth and tap it evenly 10 times along the outer wall of the container with a rubber mallet without mechanical vibration. Then place the container on a stable platform and let it stand for 60 minutes.

[0185] (5) such as Figure 2 As shown, after settling, without removing the container, samples were taken layer by layer using a scraper, in the order of upper, middle, and lower layers, with each layer height controlled at 100mm. The wet weight of each layer of concrete sample was weighed. The obtained samples were washed and sieved, and magnetically adsorbable steel fibers were separated using a magnet until there was no obvious mortar adhering to the surface of the steel fibers. The washed steel fibers were then dried in an oven at 105±5℃ until constant weight and weighed.

[0186] (6) Calculate the mass fraction of steel fibers in each layer using the following formula:

[0187] Steel fiber mass fraction = mass of dried steel fibers in the layer / wet weight of concrete in the layer × 100%.

[0188] Further calculate the deviation coefficients of the steel fiber mass fraction of the upper, middle and lower layers. The calculation method is to divide the sample standard deviation of the steel fiber mass fraction of the three layers by the average value and then multiply by 100% to obtain the steel fiber distribution deviation coefficient.

[0189] The experimental results are shown in Table 5.

[0190] Table 5. Test results of comprehensive performance and uniformity of steel fiber distribution in steel fiber reinforced concrete mixture:

[0191] Test object Initial collapse spread / mm Gas content / % Normal pressure water excretion rate / % upper layer steel fiber mass fraction / % Middle layer steel fiber mass fraction / % Lower layer steel fiber mass fraction / % Steel fiber distribution deviation coefficient / % Example 1 542 2.6 1.15 1.88 1.94 2.01 3.35 Example 2 538 2.8 0.94 1.85 1.96 1.99 3.86 Example 3 551 2.5 1.28 1.91 1.97 1.92 1.63 Comparative Example 3 558 2.9 5.32 1.34 1.86 2.65 33.72 Comparative Example 4 545 2.7 4.61 1.48 1.92 2.45 24.96 Comparative Example 5 533 2.4 1.52 1.76 1.9 1.82 3.91

[0192] Note: The steel fiber distribution deviation coefficient in Table 5 is calculated from the unrounded mass fraction of steel fibers in each layer. The mass fraction of steel fibers in each layer shown in the table is the rounded data.

[0193] According to the results shown in Table 5, the steel fiber reinforced concrete prepared using the composite admixtures obtained in Examples 1 to 3 had an initial slump spread of 538–551 mm, an air content of 2.5%–2.8%, and a normal pressure bleeding rate of 0.94%–1.28%. After standing for 60 minutes, stratified sampling analysis showed that the differences in steel fiber mass fraction between the upper, middle, and lower layers were small, with corresponding steel fiber distribution deviation coefficients of 1.63%–3.86%.

[0194] Comparative Example 3, without the addition of alkali-swellable acrylate copolymer emulsion, had an initial slump expansion of 558 mm, a normal pressure bleeding rate of 5.32%, a lower layer steel fiber mass fraction of 2.65%, and a steel fiber distribution deviation coefficient of 33.72%. Compared with the Example Group, Comparative Example 3 exhibited a higher bleeding rate and a larger difference in steel fiber distribution.

[0195] Comparative Example 4, without the addition of Weylan gum prehydration solution, had a normal pressure bleeding rate of 4.61% and a steel fiber distribution deviation coefficient of 24.96%. Compared with the Example Group, Comparative Example 4 also exhibited a higher bleeding rate and a larger difference in the mass fraction of steel fibers between the upper and lower layers.

[0196] Comparative Example 5, without the addition of ester-based slump-retaining polycarboxylate superplasticizer mother liquor, had an initial slump spread of 533 mm, a normal pressure bleeding rate of 1.52%, and a steel fiber distribution deviation coefficient of 3.91%. This group showed relatively small differences from the Example group in terms of initial bleeding rate and steel fiber distribution uniformity. However, combined with the slump spread test results of Test Example 2, its slump spread retention performance was lower than that of the Example group.

[0197] The above results indicate that, under the same baseline mix proportion and admixture dosage, alkali-swellable acrylate copolymer emulsion and Weylan gum pre-hydrated liquid contribute to reducing the atmospheric pressure bleeding rate of steel fiber reinforced concrete mixtures and improving the uniformity of steel fiber height distribution; ester-based slump-retaining polycarboxylate superplasticizer mother liquor mainly contributes to the slump spread retention performance. The composite admixtures obtained in the examples exhibit good comprehensive performance in terms of initial working performance, workability over time, atmospheric pressure bleeding rate, and uniformity of steel fiber distribution. These performances correspond to the segregation resistance and crack prevention properties of steel fiber reinforced concrete.

[0198] Test Example 5:

[0199] Test objective: To investigate the effects of waterborne isooctyltriethoxysilane emulsion on the capillary water absorption and chloride ion intrusion resistance of hardened steel fiber reinforced concrete, and to evaluate the effects of the composite admixture system on the mechanical properties, corrosion resistance, and impermeability of steel fiber reinforced concrete foundations.

[0200] The experimental steps are as follows:

[0201] (1) Using the same reference mix ratio as the aforementioned tests, weigh the composite admixtures obtained in Examples 1 to 3 and Comparative Example 6 respectively, and add them to the mixing water and mix evenly. When preparing steel fiber reinforced concrete mixtures, the total water consumption of each group is kept consistent, and the water introduced by the composite admixture is included in the total water consumption.

[0202] (2) Freshly mixed steel fiber reinforced concrete was placed into a standard mold, formed by a vibrating table, covered with a film, and left to stand for 24 hours at 20±5℃. After demolding, the specimens were moved into a standard curing room with a temperature of 20±2℃ and a relative humidity of not less than 95% for curing.

[0203] (3) Mechanical properties were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Cube specimens were taken out after 7 days and 28 days of standard curing to determine compressive strength, and prism specimens were taken out after 28 days of curing to determine flexural strength. Specimen size, loading rate, and result calculation were all performed according to this standard. The average value of the measurements of 3 specimens in each group was taken.

[0204] (4) After the specimens have been cured to standard for 28 days, cylindrical specimens are subjected to capillary water absorption tests. The sides and top of the specimens are sealed with epoxy resin, leaving only the bottom surface as the water absorption surface. The specimens are dried to constant weight at 60±5℃, cooled to room temperature, and then placed in a water tank, with the bottom surface of the specimens submerged in water 2-3 mm. The water absorption mass of the specimens at different time points is recorded, and the capillary water absorption coefficient is calculated by the slope of the linear fitting of the water absorption per unit area with the square root of time.

[0205] (5) The resistance of specimens to chloride ion intrusion was tested using the rapid chloride ion migration coefficient method according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". Cylindrical specimens cured for 28 days were cut into specimens of specified thickness, vacuum-saturated with water, and then installed in the test chamber. A DC voltage was applied to induce chloride ions to migrate into the specimen. After the test, the specimen was split open, sprayed with silver nitrate solution for color development, and the chloride ion intrusion depth was measured. The chloride ion migration coefficient was then calculated based on this measurement.

[0206] The experimental results are shown in Table 6.

[0207] Table 6. Test results of mechanical and durability properties of steel fiber reinforced concrete:

[0208] Test object 7d compressive strength / MPa 28-day compressive strength / MPa 28-day flexural strength / MPa <![CDATA[Capillary water absorption coefficient / [g / (m 2 ·h 0.5 )]]]> <![CDATA[28d chloride ion migration coefficient / (×10 -12 m 2 / s)]]> Example 1 42.4 55.7 6.84 125.6 3.48 Example 2 41.6 54.2 6.67 116.3 3.12 Example 3 43.1 56.4 6.95 132.8 3.75 Comparative Example 6 42.8 55.1 6.79 318.4 7.91

[0209] According to the results shown in Table 6, the 7-day compressive strength of Examples 1 to 3 was 41.6–43.1 MPa, the 28-day compressive strength was 54.2–56.4 MPa, and the 28-day flexural strength was 6.67–6.95 MPa. The 7-day compressive strength, 28-day compressive strength, and 28-day flexural strength of Comparative Example 6 were 42.8 MPa, 55.1 MPa, and 6.79 MPa, respectively. These data indicate that, under the same reference mix proportion and the same total water consumption, the Example groups and Comparative Example 6 are at similar levels in terms of basic mechanical properties.

[0210] Regarding durability indicators, the capillary water absorption coefficients of Examples 1 to 3 were 116.3–132.8 g / (m³). 2 ·h 0.5 The chloride ion migration coefficient after 28 days was 3.12–3.75 × 10⁻⁶. -12 m 2 / s. Comparative Example 6, without the addition of aqueous isooctyltriethoxysilane emulsion, had a capillary water absorption coefficient of 318.4 g / (m²). 2 ·h 0.5 The chloride ion migration coefficient after 28 days was 7.91 × 10⁻⁶. -12 m 2 / s.

[0211] The above results indicate that the introduction of aqueous isooctyltriethoxysilane emulsion contributes to reducing the capillary water absorption coefficient and chloride ion migration coefficient of hardened steel fiber reinforced concrete, which is beneficial to improving the resistance to water intrusion, chloride ion intrusion, and corrosion and rust prevention properties of hardened steel fiber reinforced concrete. The above test results are related to the hydrophobic effect of silane components on water entry channels; these test results do not limit the specific microscopic effects of silane components within the hardened matrix.

[0212] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite admixture suitable for steel fiber reinforced concrete, characterized in that, It consists of the following components by mass percentage: Ether-based water-reducing polycarboxylate superplasticizer mother liquor: 48.0 wt%–52.0 wt%; Ester-based slump-retaining polycarboxylate superplasticizer mother liquor: 18.0 wt%–21.0 wt%; Aqueous isooctyltriethoxysilane emulsion, 9.5 wt%–11.5 wt%; Non-pre-neutralized acid-base swellable acrylate copolymer emulsion, 0.50 wt%–0.70 wt%; Prehydrated solution of vegan gum: 3.5 wt%–4.5 wt%; Triisopropanolamine 1.2wt%~1.6wt%; Sodium gluconate 0.35wt%~0.55wt%; Sodium phytate 0.05wt%~0.10wt%; Polyether-modified silicone defoamer 0.06wt%~0.10wt%; Water-based preservatives: 0.03wt%~0.06wt%; Deionized water replenished to 100 wt%; The solid content of the ether-based water-reducing polycarboxylate superplasticizer mother liquor, the ester-based slump-retaining polycarboxylate superplasticizer mother liquor, and the aqueous isooctyltriethoxysilane emulsion is 40 wt%. The solid content of the non-pre-neutralized acid-base swellable acrylate copolymer emulsion is 25 wt% to 30 wt%. The mass fraction of the vegan gum in the vegan gum prehydration solution is 1.0 wt%.

2. The anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 1, characterized in that, The mass ratio of solids in the mother liquor of the ether-based water-reducing polycarboxylate superplasticizer to solids in the mother liquor of the ester-based slump-retaining polycarboxylate superplasticizer is not less than 2.4:

1.

3. The anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 1, characterized in that, The finished product of the corrosion-resistant, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete has a pH value of 4.0 to 5.

0.

4. The anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 1, characterized in that, The water-based preservative is Kathon preservative.

5. A method for preparing a composite admixture for corrosion prevention, rust inhibition, seepage prevention, and crack prevention adapted to steel fiber reinforced concrete according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Dissolve all sodium gluconate and all sodium phytate in the first portion of deionized water to obtain a salt solution; Then all of the triisopropanolamine was added to the salt solution to prepare a pre-diluted conditioning solution; Step 2: Add the vegan gum to the second part of deionized water and hydrate the vegan gum by stirring to obtain the vegan gum prehydrated solution with a mass fraction of 1.0 wt% in the vegan gum prehydrated solution; Step 3: Add the third portion of deionized water to a mixing tank equipped with a mechanical stirrer, then add the ether-based water-reducing polycarboxylate superplasticizer mother liquor and the ester-based slump-retaining polycarboxylate superplasticizer mother liquor in sequence, and stir at a speed of 60 r / min to 100 r / min for 10 min; then add the Vilan gum pre-hydrated liquid obtained in Step 2, and stir at a speed of 60 r / min to 100 r / min for 10 min; finally add the non-pre-neutralized acid-base swellable acrylate copolymer emulsion and the polyether-modified silicone defoamer, and stir at a speed of 40 r / min to 60 r / min for 10 min to obtain an acidic mixture; Step 4: While maintaining a stirring speed of 40 r / min to 60 r / min, add the pre-diluted conditioning solution obtained in Step 1 to the acidic mixture. After the addition is completed, continue stirring until the mixture is homogeneous. Step 5: Insert the feed pipe into the mixing tank below the liquid surface and add the aqueous isooctyltriethoxysilane emulsion while stirring at a speed of 30 r / min to 50 r / min. Step 6: Maintain a stirring speed of 30r / min to 50r / min, add the water-based corrosion inhibitor and replenish the remaining deionized water, continue stirring until the mixture is uniform, then stop stirring and let it stand for 30min to 60min. The material is then discharged to obtain the anti-corrosion, rust-inhibiting, seepage-resistant and crack-resistant composite admixture suitable for steel fiber concrete. The second portion of deionized water and the vegan gum together form the vegan gum prehydrated solution, and the second portion of deionized water is included in the mass of the vegan gum prehydrated solution; the first portion of deionized water, the third portion of deionized water and the remaining portion of deionized water together constitute the deionized water used to make up to 100 wt% in the composite additive.

6. The preparation method of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 5, characterized in that, In step one, the mass percentage concentration of triisopropanolamine in the pre-diluted conditioning solution is 10wt% to 23wt%.

7. The preparation method of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 5, characterized in that, In step three, before adding the non-pre-neutralized acid-base swellable acrylate copolymer emulsion, the pH value of the liquid in the mixing tank is 3.5 to 5.2; during the addition of the non-pre-neutralized acid-base swellable acrylate copolymer emulsion, the pH value of the liquid in the mixing tank is less than or equal to 5.

5.

8. The preparation method of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 5, characterized in that, In step four, during and after the addition of the pre-diluted conditioning solution, the pH value of the liquid in the mixing tank is controlled to be 4.0 to 5.

5.

9. The preparation method of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 5, characterized in that, In step five, the feeding rate of the aqueous isooctyltriethoxysilane emulsion is less than or equal to 0.8 wt% / min of the total mass of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted for steel fiber reinforced concrete.

10. The preparation method of the anti-corrosion, rust-inhibiting, seepage-resistant, and crack-resistant composite admixture adapted to steel fiber reinforced concrete according to claim 5, characterized in that, In steps three through six, the temperature of the liquid in the mixing tank is controlled between 23°C and 27°C; the stirring temperature in step two is between 20°C and 30°C; when the temperature of the liquid in the mixing tank rises abnormally to above 30°C in steps three through six, external cooling water is used to cool the mixing tank until the temperature of the liquid in the mixing tank returns to 23°C to 27°C.

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