Waterproof and anti-crack dry-mixed mortar and preparation method thereof

Abstract

This invention relates to the field of building materials technology, and discloses a waterproof and crack-resistant dry-mixed mortar and its preparation method. The mortar is composed of cement, graded manufactured sand, powdered composite waterproofing agent, hydrophobic redispersible latex powder, modified fibers, cellulose ether, and polycarboxylate superplasticizer. The core technology lies in utilizing the hydrolysis and condensation of active silane components to form covalent bonds with the cement matrix and undergo interfacial cross-linking with the latex powder, thereby constructing an organic-inorganic interpenetrating network within the micropores of the mortar. Simultaneously, surface-activated and hydrophilically modified fibers achieve uniform monofilament dispersion in the slurry, constructing a three-dimensional crack-resistant network. The preparation process employs step-by-step feeding and differentiated stirring speeds to protect the carrier structure of the waterproofing agent while ensuring sufficient fiber dispersion. This invention solves the technical defects of traditional mortars, such as short-lasting waterproofing and easy fiber agglomeration, achieving high impermeability, low water absorption, and excellent crack resistance, making it suitable for building waterproofing and crack-resistant projects.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a waterproof and crack-resistant dry-mixed mortar and its preparation method. Background Technology

[0002] In modern construction engineering, waterproof and crack-resistant dry-mixed mortar is a key material for ensuring structural durability and safety. To improve the impermeability of the mortar, the current conventional technical means usually involve introducing stearates, silicate powders, or hydrophobic redispersible latex powders into the formula. These waterproof components mainly seal capillary pores in the mortar through physical filling or film formation. However, the interfacial bonding between organic waterproof components and inorganic cement matrix is ​​mostly weak physical adsorption, lacking strong chemical bonding. After long-term temperature and stress changes or repeated freeze-thaw cycles in the service environment, organic components are very likely to peel off from the cement stone surface, causing the originally closed capillary channels to reopen, making it difficult to guarantee the long-term waterproof performance of the material.

[0003] While adding polypropylene or cellulose fibers to the system is a common practice in the industry to improve the crack resistance of mortar, synthetic fibers present significant dispersion challenges in practical applications. Synthetic fibers have high surface energy and lack active hydrophilic groups. During dry powder mixing and water addition, the fiber filaments are prone to entanglement and aggregation due to van der Waals forces. These unevenly dispersed fiber bundles not only fail to build a continuous three-dimensional stress transmission network within the mortar but also form local structural defects in the hardened body, becoming stress concentration sources. Furthermore, existing preparation processes often neglect the differentiated requirements of different functional components for stirring kinetic energy and lack effective control over the timing of material addition. This results in the synergistic effect of waterproofing components and reinforcing fibers in the slurry not being fully realized, making it difficult to simultaneously meet the dual requirements of high-efficiency crack resistance and long-term waterproofing under harsh working conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a waterproof and crack-resistant dry-mixed mortar and its preparation method, which solves the problems of insufficient long-term waterproof performance caused by the weak bonding force between the waterproof component and the cement matrix in existing dry-mixed mortars, and the limited crack-resistant effect caused by the easy agglomeration of synthetic fibers in alkaline slurry.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a waterproof and crack-resistant dry-mixed mortar, which adopts the following technical solution:

[0007] A waterproof and crack-resistant dry-mixed mortar comprises the following raw materials in parts by weight: 280-320 parts cement, 550-600 parts graded manufactured sand, 5-8 parts powdered composite waterproofing agent, 15-25 parts water-repellent redispersible latex powder, 3-6 parts modified fiber, 1-3 parts cellulose ether, and 1-2 parts polycarboxylate superplasticizer.

[0008] In this formulation system, the hydroxide ions released during cement hydration act as an inducing factor, causing the powdered composite waterproofing agent to be released in situ within the mortar. The active silane component establishes stable covalent bonds with the cement hydration products and the silanol groups on the aggregate surface through hydrolysis and condensation. Simultaneously, the hydrophobic latex powder undergoes interfacial cross-linking with the long silane chains during film formation, thus weaving an organic-inorganic interpenetrating network within the mortar's micropores. Meanwhile, modified fibers carrying hydrophilic functional groups spontaneously overcome van der Waals forces to achieve monofilament dispersion within the mortar, constructing a three-dimensional crack-resistant network. This multi-layered nested network structure comprehensively enhances the mortar's impermeability and flexural strength, from micropore sealing to macroscopic crack suppression.

[0009] As a preferred embodiment, the raw materials are in the following weight proportions: 300 parts cement, 580 parts graded manufactured sand, 6.5 parts powdered composite waterproofing agent, 20 parts water-repellent redispersible latex powder, 4.5 parts modified fiber, 2 parts cellulose ether, and 1.5 parts polycarboxylate superplasticizer.

[0010] Under this specific ratio, the bulk density of the cementitious material and graded aggregate reaches a high level. With the addition of appropriate amounts of waterproof and toughening components, the porosity of the hardened mortar is compressed to the maximum extent while maintaining good deformation capacity.

[0011] As a preferred embodiment, the powdered composite waterproofing agent is prepared from the following raw materials in the following weight ratio: 1 part liquid silane mixture and 1-1.5 parts inorganic porous carrier; the liquid silane mixture is prepared by mixing epoxy silane WD-60 and KH560 in a weight ratio of 1:1-1:2; the inorganic porous carrier has a specific surface area of ​​150-250. Precipitation method for silica or ultrafine kaolin.

[0012] The waterproofing mechanism of this composite waterproofing agent mainly involves the following chemical reaction evolution process:

[0013] First, the active components migrate and hydrolyze: the liquid silane mixture precipitates from the support pores into the liquid phase, where it undergoes hydrolysis under alkaline catalysis, losing alkoxy groups to form silanol intermediates.

[0014] ;

[0015] What follows is dehydration condensation and bonding: the silanol intermediates polymerize with each other and condense with the hydroxyl groups on the surface of the inorganic substrate to form a highly hydrophobic mixture. Structural layer. The reaction process is as follows:

[0016] matrix matrix ;

[0017] Finally, the crucial interfacial crosslinking occurs: the epoxy groups in the molecular structures of WD-60 and KH560 undergo ring-opening under alkaline conditions, reacting with the active functional groups exposed during the film formation process of the latex powder. This step chemically links the flexible organic polymer film with the rigid inorganic network, preventing the waterproofing components from peeling off at the interface under temperature differences or stress.

[0018] As a preferred embodiment, the modified fiber is composed of polypropylene fiber and wood fiber in a weight ratio of 2:1-3:1, and the modified fiber is prepared by the following method: after mixing polypropylene fiber and wood fiber, it is immersed in a solution of 3%-5% NaOH and 1%-2% [unspecified substance]. In the composite activation solution, stir at 40-50°C for 30-40 minutes; after washing until neutral, immerse in a 1096-15% potassium ether carboxylate aqueous solution and let stand for 5-8 hours; filter out and dry at 60-70°C.

[0019] The role of modified fibers in the system lies in the reconstruction of their surface physicochemical properties. Pretreatment in a strongly oxidizing alkaline environment not only removes oil from the fiber surface but also creates abundant microcracks and active sites on the surfaces of polypropylene and wood fibers through chemical etching. Subsequently, potassium alcohol ether carboxylate is introduced and covers the fiber surface through hydrogen bonding and physical encapsulation. Its long chain ends have polar groups, which keeps the fibers in a charged repulsive state during dry powder mixing and allows for rapid wetting with water. This ensures a high degree of uniformity in fiber distribution within the mortar, eliminating internal structural defects caused by fiber clumping at the source.

[0020] As a preferred embodiment, the fineness modulus of the graded manufactured sand is 2.3-2.8; the cellulose ether is hydroxypropyl methylcellulose with a viscosity of 40000-60000 mPa·s.

[0021] The matching fineness modulus and the specific viscosity of the cellulose ether together maintain the rheological properties of the slurry, providing a stable physical environment for the uniform distribution of waterproof components and fibers.

[0022] Secondly, the present invention provides a method for preparing waterproof and crack-resistant dry-mixed mortar, which adopts the following technical solution:

[0023] A method for preparing waterproof and crack-resistant dry-mixed mortar includes the following steps:

[0024] S1. Weigh each component raw material according to its weight parts;

[0025] S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer and cellulose ether into a mixer for homogenization and mixing;

[0026] S3. While the main shaft is stirring, the high-speed flying knife group is turned on to continuously feed hydrophobic redispersible latex powder and modified fibers. The modified fibers are distributed in three dimensions without clumping in the powder system by high-speed shearing force.

[0027] S4. Turn off the flying knife assembly, add the powdered composite waterproofing agent, and continue stirring to coat the active waterproofing components onto the surface of the particles; discharge the material and use moisture-proof packaging.

[0028] The core of this preparation process lies in the precise control of the mixing kinetic energy and feeding sequence of the materials. In step S3, the centrifugal shear force generated by the high-speed flying knife is the physical prerequisite for achieving forced dispersion of the modified fibers. The subsequent step S4, which involves feeding materials after turning off the flying knife, is based on the consideration of protecting the structure of the composite waterproofing agent carrier. Since the silica or kaolin carrier is a porous and brittle material, avoiding the direct impact of the high-speed flying knife can prevent premature leakage of silane components caused by carrier damage, thus ensuring the delayed release of the waterproofing function after the mortar is mixed with water.

[0029] As a preferred embodiment, in step S2, the main shaft speed of the mixer is 40-60 r / min, and the mixing time is 3-5 min; in step S3, the speed of the blade is 1000-1500 r / min, and the mixing time is 5-8 min; in step S4, the main shaft speed is 40-60 r / min, and the mixing continues for 5-10 min.

[0030] The aforementioned combination of rotation speed and time ensures the stability of the material flow field inside the mixer and prevents the segregation of components with large differences in specific gravity under prolonged stirring.

[0031] As a preferred option, the powdered composite waterproofing agent in step S4 needs to be pretreated before being added: the liquid silane mixture is sprayed through an atomizing nozzle into an inorganic porous carrier under high-speed stirring, and is converted into a flowable powder through pore adsorption, with the spraying time controlled at 10-15 minutes.

[0032] The atomization adsorption process is used to highly disperse high molecular weight liquid silanes. Micron-sized droplets can penetrate deeper into the deep pores of the carrier, enhancing the adsorption and binding force, and resulting in better physical stability of the finished dry powder during transportation and storage.

[0033] As a preferred option, in step S3, by controlling the surface alcohol ether carboxylate potassium loading of the modified fiber, the initial consistency of the resulting dry-mixed mortar after adding water and stirring is maintained at 90-95 mm, and the consistency loss rate is less than 10% after 1 hour.

[0034] By fine-tuning the fiber surfactant loading rate, the initial flow resistance of the slurry was indirectly controlled, ensuring crack resistance without sacrificing workability.

[0035] As a preferred option, the total mass ratio of water to dry powder of dry-mixed mortar should be controlled at 0.18-0.22 at the application site.

[0036] The significance of controlling this water addition ratio lies in limiting the capillary pore size distribution after mortar hydration, ensuring that it has a low permeability channel ratio while meeting strength requirements.

[0037] This invention provides a waterproof and crack-resistant dry-mixed mortar and its preparation method. It has the following beneficial effects:

[0038] 1. This invention constructs an organic-inorganic interpenetrating network in the microstructure of mortar through interfacial crosslinking of epoxy silane and hydrophobic latex powder. This structure changes the traditional waterproofing agent's reliance on physical filling and sealing of pores. It utilizes the silanol groups generated by silane hydrolysis to form covalent bonds with the cement matrix, significantly enhancing the chemical stability of the hydrophobic component inside the mortar. Experimental data show that this chemical bonding allows the mortar to maintain high impermeability pressure after multiple freeze-thaw cycles, effectively solving the technical problem of waterproofing performance decaying over time.

[0039] 2. The chemical activation of the modified fiber surface and the loading of potassium alcohol ether carboxylate significantly improve the spatial distribution of the fiber in the slurry. By introducing hydrophilic groups on the fiber surface, the tendency of synthetic fibers to agglomerate due to electrostatics and van der Waals forces is counteracted, allowing polypropylene fibers and wood fibers to be distributed in the mortar in the form of monofilaments. This uniform three-dimensional mesh structure effectively disperses the shrinkage stress during the cement hydration process, transforms macroscopic cracks into microscopic microcracks, thereby significantly reducing the compression-flexural ratio of the hardened mortar and improving its crack resistance.

[0040] 3. This invention utilizes a porous carrier to atomize and adsorb liquid silane, combined with a stepwise stirring process, to achieve controlled release and stable storage of active components. The atomization loading process ensures the fluidity of the waterproofing components in the dry powder state, avoiding clumping caused by liquid silane. The specific feeding sequence ensures sufficient fiber dispersion while avoiding damage to the waterproofing agent carrier structure caused by high-speed shearing. This combination of processes gives the finished mortar good workability and high initial consistency retention, meeting the material stability requirements of large-scale mechanized construction. Attached Figure Description

[0041] Figure 1 This is a comparative analysis diagram of the fiber dispersion performance of the present invention;

[0042] Figure 2 This is a bar chart comparing the anti-seepage pressure of the present invention;

[0043] Figure 3 This is a graph showing the evolution trend of the strength retention rate of the present invention as a function of composition.

[0044] Figure 4 This is a comparison chart showing the distribution of key waterproofing indicators of the present invention;

[0045] Figure 5 This is a correlation evaluation diagram of the crack resistance and toughening properties of the present invention;

[0046] Figure 6 This is a comparison chart of the construction performance and stability over time of the present invention. Detailed Implementation

[0047] The following is in conjunction with the appendix Figure 1 - Appendix Figure 6 The present invention will be further described in detail below.

[0048] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0049] The cement used is P·O42.5 grade ordinary Portland cement. The graded manufactured sand is made of quartz sand with a mud content of less than one percent, which is screened to obtain specifications of 20 to 40 mesh, 40 to 80 mesh and 80 to 120 mesh.

[0050] The chemical composition of the hydrophobic redispersible latex powder is a random copolymer of ethylene and vinyl acetate, with CAS number 24937-78-8, a solid content greater than 98%, an average molecular weight distribution index of 2.5 to 3.0, and a glass transition temperature of 5 degrees Celsius.

[0051] The chemical composition of polypropylene fiber is isotactic polypropylene homopolymer, CAS number 9003-07-0, crystallinity is 65%, density is 0.91 g / cm³, chopped length is 10 to 15 mm, and equivalent diameter is 20 to 40 micrometers.

[0052] The main component of wood fiber is natural high molecular weight cellulose, with CAS number 9004-34-6, density of 1.2 g per cubic centimeter, chopped length of 10 to 20 mm, and average diameter of 15 to 25 micrometers.

[0053] The cellulose ether is hydroxypropyl methylcellulose, CAS number 9004-65-3, with a methoxy group mass fraction of 19% to 24% and a hydroxypropoxy group mass fraction of 4% to 12%. The viscosity of a 2% aqueous solution at 20 degrees Celsius is 40,000 mPa·s.

[0054] The chemical composition of polycarboxylate superplasticizer is a random copolymer of methoxy polyethylene glycol methacrylate and methacrylic acid. The main chain is a polyacrylate skeleton composed of carbon-carbon single bonds, and the side chain is a hydrophilic structure of polyethylene glycol ether. The weight average molecular weight is 45,000 Daltons.

[0055] The epoxy silane selected is 3-glycidyl etheroxypropylmethyldiethoxysilane, CAS number 2897-60-1, with a purity greater than 98%.

[0056] Another epoxy silane is gamma-(2,3-epoxypropoxy)propyltrimethoxysilane, CAS number 2530-83-8, with a purity greater than 98%.

[0057] The inorganic porous carrier is precipitated silica, chemically known as hydrated silica, CAS number 14464-46-1, with a specific surface area of ​​200 square meters per gram.

[0058] Potassium lauryl ether carboxylate was selected from potassium lauryl polyoxyethylene ether acetate.

[0059] The molecular formula is The degree of polymerization n ranges from 3 to 9, and the content of active ingredients is greater than 90%.

[0060] Preparation Example 1:

[0061] This preparation example provides a method for preparing a powdered composite waterproofing agent, including the following steps:

[0062] S1. Weigh epoxy silane WD-60 and KH560 at a weight ratio of 1:1, add them to the reaction vessel, and mix at a speed of 200 rpm for 10 minutes to obtain a liquid silane mixture.

[0063] S2. Precipitated silica with a specific surface area of ​​150 square meters per gram was selected as an inorganic porous carrier.

[0064] S3. Place the inorganic porous carrier in a high-speed mixer and spray the liquid silane mixture evenly into the carrier through an atomizing nozzle at a speed of 800 rpm within 10 minutes. The mass ratio of the liquid silane mixture to the inorganic porous carrier is 1:1.

[0065] S4. After spraying, continue high-speed stirring for 5 minutes to ensure that the liquid silane is completely adsorbed, thus obtaining a powdered composite waterproofing agent.

[0066] Preparation Example 2:

[0067] This preparation example provides a method for preparing a powdered composite waterproofing agent, including the following steps:

[0068] S1. Weigh epoxy silane WD-60 and KH560 at a weight ratio of 1:1.5, add them to the reaction vessel, and mix them at a speed of 250 rpm for 12 minutes to obtain a liquid silane mixture.

[0069] S2. Precipitated silica with a specific surface area of ​​200 square meters per gram was selected as an inorganic porous carrier.

[0070] S3. Place the inorganic porous carrier in a high-speed mixer and spray the liquid silane mixture evenly into the carrier through an atomizing nozzle at a speed of 1000 rpm within 12 minutes. The mass ratio of the liquid silane mixture to the inorganic porous carrier is 1:1.2.

[0071] S4. After spraying, continue high-speed stirring for 8 minutes to ensure that the liquid silane is completely adsorbed, thus obtaining a powdered composite waterproofing agent.

[0072] Preparation Example 3:

[0073] This preparation example provides a method for preparing a powdered composite waterproofing agent, including the following steps:

[0074] S1. Weigh epoxy silane WD-60 and KH560 at a weight ratio of 1:2, add them to the reactor, and mix at a speed of 300 rpm for 15 minutes to obtain a liquid silane mixture.

[0075] S2. Ultrafine kaolin with a specific surface area of ​​250 square meters per gram was selected as an inorganic porous carrier.

[0076] S3. Place the inorganic porous carrier in a high-speed mixer and spray the liquid silane mixture evenly into the carrier through an atomizing nozzle at a speed of 1200 rpm within 15 minutes. The mass ratio of the liquid silane mixture to the inorganic porous carrier is 1:1.5.

[0077] S4. After spraying, continue high-speed stirring for 10 minutes to ensure that the liquid silane is completely adsorbed, thus obtaining a powdered composite waterproofing agent.

[0078] Preparation Example 4:

[0079] This preparation example provides a method for preparing modified fibers, including the following steps:

[0080] S1. Physically dry-mix polypropylene fibers with a chopped length of 10 mm and wood fibers with a chopped length of 10 mm at a weight ratio of 2:1.

[0081] S2. Prepare a composite activated aqueous solution, which consists of 3% sodium hydroxide and 1% hydrogen peroxide by mass.

[0082] S3. Immerse the mixed fibers in the activation solution at a ratio of 1 gram to 15 milliliters, and treat for 30 minutes at 40 degrees Celsius with mechanical stirring at 50 revolutions per minute.

[0083] S4. Filter out the fiber and wash it with deionized water until the pH of the washing filtrate is 7.0.

[0084] S5. Immerse the preliminarily modified fiber in a 10% aqueous solution of potassium ether carboxylate and let it stand at 20 degrees Celsius for 5 hours.

[0085] S6. Filter out the fiber and dry it directly at a constant temperature of 60 degrees Celsius for 10 hours. After drying, break it apart to obtain modified fiber.

[0086] Preparation Example 5:

[0087] This preparation example provides a method for preparing modified fibers, including the following steps:

[0088] S1. Physically dry-mix polypropylene fibers with a chopped length of 12 mm and wood fibers with a chopped length of 15 mm at a weight ratio of 2.5:1.

[0089] S2. Prepare a composite activated aqueous solution, which consists of 4% sodium hydroxide and 1.5% hydrogen peroxide by mass.

[0090] S3. Immerse the mixed fibers in the activation solution at a ratio of 1 gram to 18 milliliters, and treat for 35 minutes at 45 degrees Celsius with mechanical stirring at 80 revolutions per minute.

[0091] S4. Filter out the fiber and wash it with deionized water until the pH of the washing filtrate is 7.2.

[0092] S5. Immerse the preliminarily modified fiber in a 12.5% ​​aqueous solution of potassium ether carboxylate and let it stand at 22 degrees Celsius for 6.5 hours.

[0093] S6. Filter out the fiber and dry it directly at a constant temperature of 65 degrees Celsius for 11 hours. After drying, break it apart to obtain modified fiber.

[0094] Preparation Example 6:

[0095] This preparation example provides a method for preparing modified fibers, including the following steps:

[0096] S1. Physically dry-mix polypropylene fibers with a chopped length of 15 mm and wood fibers with a chopped length of 20 mm at a weight ratio of 3:1.

[0097] S2. Prepare a composite activated aqueous solution, which consists of 5% sodium hydroxide and 2% hydrogen peroxide by mass.

[0098] S3. Immerse the mixed fibers in the activation solution at a ratio of 1 gram to 20 milliliters, and treat for 40 minutes at 50 degrees Celsius with mechanical stirring at 100 revolutions per minute.

[0099] S4. Filter out the fiber and wash it with deionized water until the pH of the washing filtrate is 7.5.

[0100] S5. Immerse the preliminarily modified fiber in a 15% aqueous solution of potassium ether carboxylate and let it stand at 25 degrees Celsius for 8 hours.

[0101] S6. Filter out the fiber and dry it directly at a constant temperature of 70 degrees Celsius for 12 hours. After drying, break it apart to obtain modified fiber.

[0102] Example 1:

[0103] This embodiment provides Example 1: using the powdered composite waterproofing agent of Preparation Example 1 and the modified fiber of Preparation Example 4. The components, including cement, graded manufactured sand, powdered composite waterproofing agent, hydrophobic redispersible latex powder, and modified fiber, are all taken as the lowest weight parts within the scope of the claims; the process parameters are taken as the lower limit.

[0104] A waterproof and crack-resistant dry-mixed mortar is composed of the following raw materials in parts by weight: 280 parts cement, 550 parts graded manufactured sand, 5 parts powdered composite waterproofing agent prepared in Preparation Example 1, 15 parts water-repellent redispersible latex powder, 3 parts modified fiber prepared in Preparation Example 4, 1 part cellulose ether, and 1 part polycarboxylate superplasticizer.

[0105] A method for preparing waterproof and crack-resistant dry-mixed mortar includes the following steps:

[0106] S1. Weigh each powder component accurately according to the above proportions to prepare the powdered composite waterproofing agent of Example 1 and the modified fiber of Example 4.

[0107] S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer, and cellulose ether to an industrial-grade twin-shaft zero-gravity mixer. Start the mixer, control the spindle speed at 40 rpm, and mix for 3 minutes.

[0108] S3. Maintain the mixer spindle speed at 40 rpm, turn on the internal blade assembly, and set the blade speed to 1000 rpm. Slowly and continuously add the hydrophobic redispersible latex powder and modified fibers, and mix for 5 minutes.

[0109] S4. Turn off the fly knife assembly and add the powdered composite waterproofing agent into the mixer. Continue stirring at a spindle speed of 40 rpm for 5 minutes. Discharge the material and seal it in a packaging bag with a moisture-proof liner.

[0110] At the application site, add construction water at a ratio of 0.18 (total mass of water to dry mortar powder), and mechanically mix until uniform before application.

[0111] Example 2:

[0112] This embodiment provides Example 2: The powdered composite waterproofing agent from Preparation Example 2 and the modified fiber from Preparation Example 5 are selected. The weight proportions of each component are taken as the intermediate optimal values; the process includes the following steps:

[0113] A waterproof and crack-resistant dry-mixed mortar is composed of the following raw materials in parts by weight: 300 parts cement, 580 parts graded manufactured sand, 6.5 parts powdered composite waterproofing agent prepared in Preparation Example 2, 20 parts water-repellent redispersible latex powder, 4.5 parts modified fiber prepared in Preparation Example 5, 2 parts cellulose ether, and 1.5 parts polycarboxylate superplasticizer.

[0114] A method for preparing waterproof and crack-resistant dry-mixed mortar includes the following steps:

[0115] S1. Weigh each powder component accurately according to the above proportions, prepare the powdered composite waterproofing agent of Example 2, and prepare the modified fiber of Example 5.

[0116] S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer, and cellulose ether to an industrial-grade twin-shaft zero-gravity mixer. Start the mixer, control the spindle speed to 50 rpm, and mix for 4 minutes to fully homogenize the basic inorganic powder.

[0117] S3. Maintain the mixer spindle speed at 50 rpm, turn on the internal blade assembly, and set the blade speed to 1250 rpm. Slowly and continuously add the hydrophobic redispersible latex powder and modified fibers. Utilize the high-speed shearing force of the blade assembly in conjunction with the spindle rotation to mix for 6.5 minutes, ensuring that the modified fibers achieve a clumping-free, three-dimensional, uniform distribution in the dry powder system.

[0118] S4. Turn off the fly knife assembly and add the powdered composite waterproofing agent into the mixer. Continue stirring at a spindle speed of 50 rpm for 8 minutes to ensure that the active waterproofing components are evenly coated on the aggregate surface without damaging the fiber network. After discharge, seal the product in a packaging bag with a moisture-proof liner.

[0119] At the application site, add construction water at a ratio of 0.20 (total mass of water to dry mortar powder), and mechanically mix until uniform before application.

[0120] Example 3:

[0121] This embodiment provides Example 3: using the powdered composite waterproofing agent of Preparation Example 3 and the modified fiber of Preparation Example 6. The weight parts of each component are the highest weight parts within the scope of the claims; the method includes the following steps:

[0122] A waterproof and crack-resistant dry-mixed mortar is composed of the following raw materials in parts by weight: 320 parts cement, 600 parts graded manufactured sand, 8 parts powdered composite waterproofing agent prepared in Preparation Example 3, 25 parts water-repellent redispersible latex powder, 6 parts modified fiber prepared in Preparation Example 6, 3 parts cellulose ether, and 2 parts polycarboxylate superplasticizer.

[0123] A method for preparing waterproof and crack-resistant dry-mixed mortar includes the following steps:

[0124] S1. Weigh each powder component accurately according to the above proportions, prepare the powdered composite waterproofing agent of Example 3, and prepare the modified fiber of Example 6.

[0125] S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer, and cellulose ether into an industrial-grade twin-shaft zero-gravity mixer. Start the mixer, control the spindle speed to 60 rpm, and mix for 5 minutes to ensure macroscopic homogenization of the base powder under high admixture levels.

[0126] S3. Maintain the mixer spindle speed at 60 rpm, turn on the fly knife assembly inside the mixer, and set the fly knife speed to 1500 rpm. Slowly and continuously add the hydrophobic redispersible latex powder and the modified fiber of Preparation Example 6. Run high-intensity shear mixing for 8 minutes to ensure that the modified fiber at the maximum dosage is fully expanded and uniformly distributed in the dense powder particles.

[0127] S4. Turn off the fly knife assembly and add the powdered composite waterproofing agent into the mixer. Continue stirring at a spindle speed of 60 rpm for 10 minutes. After discharging, seal the product in a packaging bag with a moisture-proof liner.

[0128] At the application site, add construction water at a ratio of 0.22 (total mass of water to dry mortar powder), and mechanically mix until uniform before application.

[0129] Example 4:

[0130] This embodiment provides Example 4: using an intermediate weight ratio formulation, but combined with the powdered composite waterproofing agent of Preparation Example 1 and the modified fiber of Preparation Example 6 (demonstrating that the preparation parameters of various custom components are feasible in the final formulation), including the following steps:

[0131] A waterproof and crack-resistant dry-mixed mortar is composed of the following raw materials in parts by weight: 300 parts cement, 580 parts graded manufactured sand, 6.5 parts powdered composite waterproofing agent prepared in Preparation Example 1, 20 parts water-repellent redispersible latex powder, 4.5 parts modified fiber prepared in Preparation Example 6, 2 parts cellulose ether, and 1.5 parts polycarboxylate superplasticizer.

[0132] A method for preparing waterproof and crack-resistant dry-mixed mortar includes the following steps:

[0133] S1. Weigh each powder component accurately according to the above proportions to prepare the powdered composite waterproofing agent of Example 1 and the modified fiber of Example 6.

[0134] S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer, and cellulose ether to an industrial-grade twin-shaft zero-gravity mixer. Start the mixer, control the spindle speed to 50 rpm, and mix for 4.5 minutes to ensure uniform distribution of the basic inorganic cementitious materials and aggregates.

[0135] S3. Maintain the mixer spindle speed at 50 rpm, turn on the internal blade assembly, and set the blade speed to 1250 rpm. Slowly and continuously add the hydrophobic redispersible latex powder and the modified fiber from Preparation Example 6. Utilize the high-speed shearing force of the blade assembly to rapidly disperse the fiber with high surfactant content in Preparation Example 6 in the dry powder system, and run the mixing process for 7 minutes.

[0136] S4. Turn off the fly knife assembly and add the powdered composite waterproofing agent prepared in Example 1 into the mixer. Continue stirring at a spindle speed of 50 rpm for 8 minutes to ensure that the low-load waterproofing agent fully coats the surfaces of each component. After discharge, seal the product in a packaging bag with a moisture-proof liner.

[0137] At the application site, add construction water at a ratio of 0.20 (total mass of water to dry mortar powder), and mechanically mix until uniform before application.

[0138] Comparative Example 1:

[0139] Compared with Example 2, the difference is that the powdered composite waterproofing agent obtained in Preparation Example 2 was not added, and the modified fiber obtained in Preparation Example 5 was not added, while the other components and preparation processes are the same.

[0140] Comparative Example 2:

[0141] Compared with Example 2, the difference is that the modified fibers in Preparation Example 5 were replaced with untreated commercially available ordinary polypropylene fibers (12 mm chopped length) and ordinary wood fibers (15 mm chopped length) in equal amounts, while all other aspects were the same.

[0142] Comparative Example 3:

[0143] Compared with Example 2, the difference is that the powdered composite waterproofing agent obtained in Preparation Example 2 was not added, and only the hydrophobic redispersible latex powder was retained, while the rest were the same.

[0144] Comparative Example 4:

[0145] Compared with Example 2, the difference is that in the preparation of the powdered composite waterproofing agent, all epoxy silanes are replaced with an equal mass of single component KH560, and WD-60 is not added, while the rest are the same.

[0146] Comparative Example 5:

[0147] Compared with Example 2, the difference is that: no inorganic porous carrier is used, and in step S4 of the dry powder mixing stage, an equal mass of liquid silane mixture (a mixture of WD-60 and KH560) is directly added dropwise, while the rest are the same.

[0148] Comparative Example 6:

[0149] The difference from Example 2 is that hydrophobic redispersible latex powder is not added to the formulation, but all other aspects are the same.

[0150] Test Example 1:

[0151] This experiment aims to verify the dispersion quality of modified fibers in mortar systems using macroscopic statistical methods. Example 2 (using the modified fibers from Preparation Example 5) and Comparative Example 2 (using an equal amount of untreated ordinary fibers) were selected as the main research subjects.

[0152] Weigh 2 kg of each of the dry-mixed mortars provided in Example 2 and Comparative Example 2, and put them into a laboratory mortar mixer with a transparent mixing bucket. Add construction water according to the water-to-material ratio determined by each example.

[0153] Start the mixer and mix at a low speed of 140 r / min for 30 seconds, then switch to a high speed of 285 r / min for 120 seconds to simulate the forced mechanical mixing process on the engineering site.

[0154] After mixing, five representative slurry samples with a volume of 200mL were randomly selected from the surface, middle and bottom layers of the slurry and quickly poured into an overflow container containing 2L of clean water for dilution. The slurry was then slowly rinsed with circulating water to allow cement particles to be washed away with the water flow.

[0155] Residual fibers were intercepted using a standard sieve with a pore size of 1.2 mm. The intercepted material was then transferred to a white porcelain dish with a 1 cm × 1 cm grid. The number of fiber clusters with a diameter greater than 2 mm was observed and recorded by the naked eye and a magnifying glass.

[0156] The total number of clusters at the five sampling points is calculated by weighted average, and the standard deviation of the number of clusters at each point is calculated to characterize the fluctuation of fiber distribution in three-dimensional space.

[0157] Table 1. Distribution patterns and dispersibility evaluation data of fiber clusters.

[0158] Group Number of clusters in Sample 1 Number of clusters in Sample 2 (individuals) Number of clusters in sample 3 Number of clusters in sample 4 Number of clusters in sample 5 Average number of clusters (pieces) Standard deviation Example 2 3 1 4 2 2 2.4 1.14 Comparative Example 2 28 19 34 23 26 26.0 5.57

[0159] Reference Figure 1 According to the data in Table 1 and Figure 1 The intuitive distribution pattern reveals that in Example 2, fiber agglomerations are minimal and the distribution is highly uniform, indicating that the fibers have achieved near-molecular-level spreading in the mortar. In contrast, in Comparative Example 2, severe and disordered agglomeration easily leads to numerous physical defects in the hardened mortar.

[0160] This dispersion difference stems from the surface synergistic modification mechanism of this invention. Unmodified fibers are prone to entanglement due to their hydrophobicity and electrostatic properties; however, this method, through alkali-oxygen composite activation, successfully induces a large number of hydroxyl and carboxyl active sites on the surface of the fiber molecular chains. Subsequently, potassium alcohol ether carboxylate is anchored to the active sites, forming a negatively charged directional adsorption layer. Utilizing the repulsion of like charges and the lubrication effect, the agglomeration force between fibers is completely overcome, while significantly improving its wettability with cement. Ultimately, a dense three-dimensional crack-resistant network is constructed at the microscopic level, which is the underlying logic for achieving excellent impermeability.

[0161] Test Example 2:

[0162] This experiment aims to evaluate the contribution of the interpenetrating network structure formed by the composite waterproofing agent and latex powder to the compactness of the mortar by quantitatively measuring the impermeability pressure and water absorption of the mortar at different ages. Examples 2, 3, and 4 were mainly selected as experimental subjects to verify the synergistic effect of the bissilane system.

[0163] Standard mortar specimens were prepared according to the proportions of Example 2, Comparative Example 3, and Comparative Example 4. The specimens were cones with an upper diameter of 70 mm, a lower diameter of 80 mm, and a height of 30 mm.

[0164] After molding, the specimens were cured in a standard curing environment (temperature 20±2°C, relative humidity above 95%) for 24 hours, then demolded and continued to be cured for 28 days.

[0165] The seepage resistance pressure was measured using a mortar permeability meter. The test started with a pressure of 0.1 MPa, and the pressure was increased by 0.1 MPa every 8 hours until signs of water seepage appeared on the end face of the specimen. The pressure value at this time was recorded.

[0166] Take another cubic specimen (70.7mm×70.7mm×70.7mm) from the same batch that has been cured for 28 days, dry it in an oven at 105°C until constant weight, and weigh the initial mass.

[0167] The specimen was immersed in a water tank with a depth of 30 mm, and the mass change was recorded after immersion for 6 h, 12 h, 24 h and 48 h, respectively. The water absorption per unit area was calculated.

[0168] To simulate the durability in actual engineering, some specimens were subjected to 50 freeze-thaw cycles before the retention rate of their impermeability pressure was measured, thereby evaluating the long-term stability of the waterproofing system.

[0169] Table 2 Test data of mortar impermeability and water absorption dynamics

[0170] Group Impermeability pressure (MPa) 24-hour water absorption (g / m²) 48-hour water absorption (g / m²) Permeability pressure after freeze-thaw cycle (MPa) Permeability retention rate (%) Example 2 1.8 243.5 312.2 1.6 88.9 Comparative Example 3 0.6 895.2 1240.6 0.3 50.0 Comparative Example 4 1.1 512.8 728.4 0.7 63.6

[0171] Reference Figure 2 Based on the data performance in Table 2 and Figure 2 The clear performance gradient reveals that Example 2 exhibits superior impermeability and durability (initial impermeability 1.8 MPa, 88.9% retention rate after 50 freeze-thaw cycles), far exceeding the comparative examples containing only single latex powder or single silane in terms of impermeability enhancement and water absorption inhibition. This significant leap in data fully demonstrates the remarkable synergistic enhancement value of the dual-silane system in the microstructure.

[0172] From a deeper mechanistic perspective, the strong alkaline environment generated during mortar hydration triggers the hydrolysis reaction of the bissilanes (WD-60 and KH560) in the composite waterproofing agent in situ. The generated silane molecules not only condense on the capillary walls to form a dense monomolecular hydrophobic film, but also undergo deep chemical cross-linking with the hydrophobic latex powder in the system through epoxy groups.

[0173] This chemical cross-linking breaks away from traditional physical encapsulation, constructing a robust organic-inorganic interpenetrating network (IPN). This network significantly reduces capillary pore size and alters the wetting angle of the inner wall, effectively blocking moisture penetration; simultaneously, its strong chemical bonding forces can resist the expansion stress of freeze-thaw ice crystals, thus endowing the material with excellent long-term waterproof reliability.

[0174] Test Example 3:

[0175] This experiment quantitatively evaluated the crosslinking synergistic effect between epoxy silane and latex powder by measuring the tensile bond strength between mortar and substrate under dry and immersion conditions. The experiment focused on comparing Example 2 (containing composite waterproofing agent and latex powder), Comparative Example 3 (containing latex powder only), and Comparative Example 6 (containing composite waterproofing agent only) to verify the chemical anchoring effect of organic-inorganic interpenetrating network (IPN) at the interface.

[0176] Prepare multiple standard cement concrete base plates (strength grade C40) with dimensions of 400mm×400mm×70mm, and sandblast their surfaces to remove laitance and ensure that the surface roughness of the substrate is uniform.

[0177] Dry-mixed mortar slurries were prepared according to the proportions of Example 2, Comparative Example 3, and Comparative Example 6, respectively.

[0178] A 50mm×50mm forming area was marked on the standard base plate. Each set of mortar was applied to the surface of the substrate using a mold. The plaster thickness was controlled at 5.0mm±0.5mm. Ten independent test points were prepared for each formula.

[0179] The specimens were cured for 14 days under standard laboratory conditions (temperature 23±2°C, relative humidity 50±5%), and then each group of specimens was divided into a dry group and a water-immersed group.

[0180] The specimens in the immersion group need to be completely submerged in a water bath at 20°C for 14 days. After being removed, the surface moisture should be wiped dry with a cloth and placed in a cool place for 24 hours to eliminate the influence of physical water on the surface.

[0181] A steel pull-out head was bonded to the mortar surface using a high-strength epoxy adhesive. A tensile test was conducted using a precision tensile testing machine at a loading rate of (5.0±1.0) N / s, and the ultimate load at fracture was recorded.

[0182] According to the formula Calculate the strength retention rate, where For dry tensile bond strength, This refers to the tensile bond strength when immersed in water.

[0183] Table 3. Tensile bond properties and water retention rates of different interface-reinforced systems.

[0184] Group Drying strength Immersion strength Strength retention rate (%) Forms of destruction Example 2 1.54 1.32 85.7 Substrate / mortar cohesive failure Comparative Example 3 1.28 0.63 49.2 Interface peeling damage Comparative Example 6 0.76 0.52 68.4 Interface peeling damage

[0185] See attached document Figure 3 Based on the experimental data in Table 3 and Figure 3 As can be seen from the strength distribution evolution trend, Example 2 exhibits a qualitative leap in interfacial bonding performance. Under dry conditions, the bonding strength of Example 2 reaches 1.54 MPa, far exceeding the 0.76 MPa of Comparative Example 6; while under the more severe water immersion environment, the strength retention rate of Example 2 is as high as 85.7%, whereas Comparative Example 3, which only added latex powder, saw its strength retention rate plummet to 49.2% after water immersion, losing almost half of its bonding strength. This phenomenon of maintaining extremely high structural integrity even in a humid environment fully demonstrates the key role of the chemical cross-linking network constructed in this scheme at the interface.

[0186] From a microscopic chemical perspective, the reason why Comparative Example 3 experienced a significant performance decline after immersion in water is that while redispersible latex powder (VAE) can provide good physical adhesion through film formation, the bonding between this polymer film and the inorganic substrate (base plate and aggregate) mainly relies on van der Waals forces and physical interactions. When water molecules migrate along the interfacial gaps, their strong polarity generates a wedge-like peeling effect, leading to the failure of physical adsorption sites. In contrast, Example 2, by introducing a bissilane composite system containing epoxy groups, triggered by the highly alkaline environment released during cement hydration, saw the silanol groups at the ends of the silane molecules undergo dehydration condensation with the siloxane bonds on the cement substrate surface, forming a stable chemical anchor.

[0187] Meanwhile, the epoxy groups on the molecular chains of WD-60 and KH560 underwent ring-opening addition reactions with the polar groups (such as hydroxyl or carboxyl groups) in the latex powder molecular chains. This reaction tightly binds the originally independent organic polymer film and inorganic silicate aggregate together through covalent bonds, forming a typical organic-inorganic interpenetrating network (IPN). In this structure, the epoxy silane acts as an interfacial bridge, enabling stress to be effectively transferred between the organic and inorganic phases during tensile testing. The substrate / mortar cohesive failure mode exhibited in Example 2, rather than interfacial delamination failure, macroscopically confirms that the strength of the chemical bond exceeds the tensile strength of the material itself. This transformation from physical encapsulation to chemical bonding is the core inventive aspect of this invention, enabling it to achieve high-performance waterproofing and crack resistance with extremely high water resistance stability.

[0188] Experimental Example 4:

[0189] This experiment aims to quantitatively evaluate the water-blocking performance of a composite waterproofing system under real water pressure by measuring the ultimate impermeability pressure and early capillary water absorption characteristics of the mortar at standard age. The test subjects were Examples 1, 2, 3, and 4, as well as Comparative Examples 1, 3, and 4.

[0190] Based on the material proportions of Examples 1 to 4 and Comparative Examples 1, 3, and 4, dry powder and construction water were weighed and mixed in a constant temperature and humidity test environment to prepare a uniform mortar slurry.

[0191] The slurry is injected into a truncated conical metal mold (upper inner diameter 70mm, lower inner diameter 80mm, height 30mm) and a standard cubic mold (70.7mm×70.7mm×70.7mm), and then compacted at low frequency on a vibrating table to remove large air bubbles trapped inside.

[0192] After the specimens were placed in a standard curing room with a temperature of (20±2)℃ and a relative humidity of over 90% for 24 hours, they were demolded and continued to be cured in the same environment until they reached 28 days of age.

[0193] Remove the 28-day-old truncated cone specimen and fix its sides into the test mold of the mortar permeability meter using sealing material. Apply an initial water pressure of 0.1 MPa to the bottom, and strictly maintain a pressurization frequency of 0.1 MPa every 8 hours during the subsequent test. Stop pressurizing when water droplets are observed seeping from the top surface of the specimen, and record the water pressure value at which no water seepage occurred in the previous stage as the maximum impermeability pressure of the specimen.

[0194] Take out the cubic specimens from the same batch that have been cured for 28 days, place them in an electric heating drying oven set at 105℃ and bake them until the difference between the two weighings does not exceed 0.2%, and record the absolute dry mass at this time.

[0195] The dried specimen was immersed in a constant temperature water bath at 20℃, with the water level approximately 30mm above the top surface of the specimen. After immersion for 24 hours, the specimen was removed, and the surface was quickly wiped dry with a wrung-out damp towel and weighed immediately. The ratio of the increased mass to the surface area of ​​the specimen was calculated to obtain the water absorption per unit area over 24 hours.

[0196] Table 4. Test data of impermeability pressure and 24-hour water absorption of mortar under different formulation systems.

[0197] Group Test object feature description Impermeability pressure (MPa) 24-hour water absorption (g / m²) Example 1 Lower limit of formula parameters 1.5 356.2 Example 2 Median (optimal) formula parameters 1.8 243.5 Example 3 Upper limit of formula parameters 1.9 231.8 Example 4 Cross-validation formulation 1.7 268.4 Comparative Example 1 Ordinary base mortar (unmodified) 0.2 1852.6 Comparative Example 3 Powder waterproofing agent is unavailable (contains only latex powder). 0.6 895.2 Comparative Example 4 Single silane formulation (WD-60 unavailable) 1.1 512.8

[0198] Reference Figure 4 According to the data in Table 4, the unmodified ordinary reference mortar has extremely poor water resistance and is very prone to penetrating leakage in the early stage of pressurization (for example, the anti-seepage pressure of Comparative Example 1 is only 0.2 MPa, and the water absorption is large). The fundamental reason is that the interconnected capillary network formed by water evaporation and hydration shrinkage inside the matrix is ​​not blocked, which is also the core cause of leakage in actual engineering.

[0199] This invention overcomes the limitations of single polymer physical film formation, which is prone to swelling and failure, and the lack of spatial shielding of single silanes. By introducing the synergistic effect of WD-60 and KH560 bissilanes, a deep chemical cross-linking and network-like hydrophobic structure is constructed within the matrix. This enables the mortar to maintain a stable impermeability pressure exceeding 1.5 MPa and significantly reduce water absorption to below 400 g / m², achieving excellent impermeability performance.

[0200] To address the issue of fluctuating waterproofing performance caused by the agglomeration of liquid hydrophobic agents, this invention innovatively employs a powdered porous carrier process. Upon contact with water, this carrier uniformly releases active silanes like microcapsules and undergoes an in-situ reaction, macroscopically blocking the intrusion of moving water and microscopically eliminating capillary water migration, thus ensuring highly stable and excellent waterproofing performance of the system.

[0201] Experimental Example 5:

[0202] This experiment aims to quantitatively evaluate the effect of modified fibers on improving the brittleness of mortar and their contribution to crack prevention by analyzing the variation law of the compression-flexural ratio of mortar and the cracking sensitivity under circular constraints. The test subjects selected were Example 2 (containing the best modified fiber), Comparative Example 1 (without fiber and waterproofing agent) and Comparative Example 2 (containing an equal amount of untreated ordinary fiber).

[0203] Prepare dry materials according to the proportioning schemes of Example 2, Comparative Example 1 and Comparative Example 2, add water and stir evenly, and then pour them into standard prism molds of 40mm×40mm×160mm respectively. Prepare 6 specimens for mechanical strength testing in each group.

[0204] Simultaneously, a circular ring-constrained cracking test apparatus was prepared, and each group of slurry was injected into a circular ring mold with an inner diameter of 254 mm, an outer diameter of 305 mm, and a height of 100 mm. A rigid steel ring was provided at the center of the specimen to form an internal constraint, and the outer wall of the mold was removed 24 hours after molding.

[0205] Strength test specimens were cured in a standard curing room for 28 days; ring specimens were placed in a controlled environment laboratory with a temperature of (20±2)℃, relative humidity of (50±5)%, and wind speed of 0.5m / s to induce the formation of shrinkage cracks.

[0206] After reaching 28 days of age, the flexural strength was obtained by conducting a three-point bending test using a flexural and compressive strength testing machine. Subsequently, a compressive strength test was conducted on the fractured half of the prism to obtain its compressive strength. According to the formula Calculate the compression-to-fold ratio.

[0207] The outer surface of the circular specimen was inspected daily morning and evening using a high-powered microscope, and the time when the first visible crack appeared was recorded (accurate to the hour). If no crack appeared within 28 days of curing, it was recorded as no crack.

[0208] At the end of the test, the width of all cracks on the surface of the ring was measured using a reading microscope with a scale of 0.01 mm, and the maximum value was taken as the limit crack width index of this group of specimens.

[0209] Table 5. Test results of mechanical properties and crack resistance parameters for different fiber-reinforced systems.

[0210] Group compressive strength (MPa) Flexural strength (MPa) Compression ratio First crack time (h) Maximum crack width (mm) Example 2 24.3 8.2 2.96 No cracks 0 Comparative Example 1 21.5 3.8 5.66 42 0.43 Comparative Example 2 22.8 5.1 4.47 158 0.19

[0211] Reference Figure 5 According to the data recorded in Table 5, Example 2 exhibits significant high strength and low brittleness characteristics, with a compression-flexural ratio that decreased by nearly 48%, indicating a substantial enhancement in the material's energy dissipation capacity and making it less prone to brittle fracture. In the stringent ring confinement test, Example 2 remained crack-free for 28 days, verifying that the modified fiber-reinforced mesh structure constructed within the mortar possesses extremely high crack resistance reliability.

[0212] At the microscopic level, the toughening effect depends on the interfacial bonding efficiency between the fiber and the cement matrix. Ordinary unmodified fibers, due to their hydrophobic surface, high chemical inertness, and tendency to agglomerate, not only have weak bonding with the slurry (resulting in limited improvement in flexural strength) but also form stress concentration points, which is the fundamental reason why the comparative sample still cracked.

[0213] This solution uses chemical methods to make the fiber surface hydrophilic and efficiently dispersed, forming a bridging effect in the mortar to counteract tensile stress. Simultaneously, chemical cross-linking at the interface firmly anchors the fibers to the cement matrix through covalent bonds, allowing them to absorb destructive energy through elastic deformation under stress and preventing them from being pulled out. This mechanism, from chemical modification to physical toughening, completely eliminates cracks and provides mechanical protection for the long service life of the mortar.

[0214] Experimental Example 6:

[0215] This experiment evaluated the impact of different introduction methods of active silane components on the adaptability of mortar engineering by quantifying the feed flow rate in the dry powder state and the consistency evolution of the slurry after mixing with water. Example 2, Comparative Example 1, and Comparative Example 5 were selected as test subjects to verify the actual effectiveness of the powder loading process in addressing the pain points of liquid additive engineering.

[0216] 500g of each of the dry mortar samples prepared in Example 2, Comparative Example 1 and Comparative Example 5 were selected and placed in an indoor environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours in a sealed manner to simulate a short-term storage process.

[0217] The flowability of the dry powder material was determined using a standard Hall effect flowmeter. 50.0 g of the powder to be tested was accurately weighed and poured into a funnel with a closed baffle at the bottom. The baffle was removed and a timer was started simultaneously. The time taken for the powder to completely flow out of the funnel orifice was recorded, the powder flow rate was calculated, and the agglomeration characteristics of the powder were recorded during the feeding process.

[0218] Add the remaining dry mortar to the construction water according to the water-to-material ratio determined by the respective formula, and slowly mix in a standard mortar mixer for 30 seconds, then switch to fast mixing for 90 seconds to obtain a uniform test slurry.

[0219] Immediately after the slurry is mixed, the initial consistency is measured using a slurry consistency meter. The slurry is filled into the consistency cone in two batches and compacted. The standard cone is then released to sink into the slurry, and the sinking depth at 10 seconds is recorded as the initial consistency value.

[0220] Pour the tested slurry back into the mixing pot, cover the pot opening with a damp cloth to prevent excessive evaporation of moisture, and let it stand for 60 minutes.

[0221] After the settling period, turn on the mixer and stir quickly for 15 seconds. Repeat the above consistency test operation to obtain the consistency value over 1 hour. Calculate the consistency loss rate over 1 hour by combining the initial consistency data.

[0222] Table 6. Test data on dry powder flowability and slurry consistency loss for different silane introduction processes.

[0223] Group Dry powder flow rate (g / s) Observation of clumping status Initial consistency (mm) 1-hour consistency (mm) Consistency loss rate over 1 hour (%) Example 2 19.4 The powder is loose and has no visible lumps. 93 86 7.5 Comparative Example 1 22.1 The powder is loose and has no visible lumps. 96 84 12.5 Comparative Example 5 4.3 There are obvious wet lumps, so the material needs to be tapped before being discharged. 89 61 31.4

[0224] Reference Figure 6 As shown in Table 6, the direct introduction of liquid additives has a significant negative impact on the basic physical morphology and engineering performance of dry-mixed mortar. The flowability index of Comparative Example 5 shows that its dry powder feed rate is only 4.3 g / s, and the powder stagnates during the funnel flow rate test, requiring external tapping and vibration to maintain intermittent feeding. The sample also contains a large number of wet lumps. In large-scale automated premixed mortar manufacturing, loss of dry material flowability can cause screw conveyor jamming and inaccurate metering in the batching and weighing system, leading to potential quality problems. In contrast, Example 2 has a feed rate of 19.4 g / s, far exceeding Comparative Example 5, and its performance is comparable to the baseline sample of Comparative Example 1 without added liquid modifiers, maintaining the loose and rheological characteristics of the dry powder material.

[0225] The core mechanism leading to the aforementioned differences in macroscopic physical states is the spatial physical isolation effect of the porous carrier. In Comparative Example 5, liquid silane was directly mixed into the powder system. Driven by surface tension, the small-molecule liquid substance permeated between cement and fine aggregate particles, forming a liquid bridge effect, causing the discrete solid particles to agglomerate. In contrast, the powder loading process relied upon in Example 2 pre-adsorbed WD-60 and KH560 into the interior of high specific surface area silica. The porous silica framework formed a stable inorganic barrier around the silane molecules, cutting off the initial physical adhesion channels between the liquid active components and the external coarse and fine aggregates, fundamentally eliminating the risk of agglomeration during powder storage and pipeline transportation.

[0226] The consistency evolution path of the slurry after mixing with water reveals the chemical regulation effect of the powder loading structure on the hydrolysis reaction of the active components. Comparative Example 5 showed a consistency loss rate of 31.4% after 1 hour, and the slurry became rough and hard after standing. This is because the liquid silane lacked protection, and prematurely partially hydrolyzed with the adsorbed water on the surface of the cement particles during the dry powder mixing stage. After adding water, the exposed silanol groups combined with early cement hydration products, consuming a large amount of free water. In contrast, Example 2 showed a consistency loss rate of only 7.5% after 1 hour, and the slurry remained smooth to the touch after standing for one hour. This is because the composite silane deeply embedded in the micropores of the carrier, initially resisted by the pore structure, delayed the entry of water molecules and the release of active substances, avoiding the overlap of the violent hydrolysis stage of silane with the peak of the early rapid hydration period of cement. This microscopic slow-release kinetic regulation ensures that silane molecules exert interfacial cross-linking effects in a mature alkaline environment while also allowing sufficient working time for construction personnel.

[0227] 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 waterproof and crack-resistant dry-mixed mortar, characterized in that, Made from the following ingredients in parts by weight: 280-320 parts cement; 550-600 parts of graded manufactured sand; 5-8 parts of powdered composite waterproofing agent; 15-25 parts of hydrophobic redispersible latex powder; 3-6 parts of modified fiber; 1-3 parts of cellulose ether; 1-2 parts of polycarboxylate superplasticizer; During the mortar hydration process, the powdered composite waterproofing agent and the hydrophobic redispersible latex powder crosslink with the polymer through the epoxy groups of the silane component, constructing an organic-inorganic interpenetrating network to seal the capillary pores of the mortar; the modified fibers achieve uniform dispersion inside the mortar through the hydrophilic active groups on their surface, constructing a three-dimensional crack-resistant network.

2. The waterproof and crack-resistant dry-mixed mortar according to claim 1, characterized in that, The raw materials are in the following weight proportions: 300 parts cement, 580 parts graded manufactured sand, 6.5 parts powdered composite waterproofing agent, 20 parts hydrophobic redispersible latex powder, 4.5 parts modified fiber, 2 parts cellulose ether, and 1.5 parts polycarboxylate superplasticizer.

3. The waterproof and crack-resistant dry-mixed mortar according to claim 1, characterized in that, The powdered composite waterproofing agent is prepared from the following raw materials in the following weight ratio: One part of liquid silane mixture; 1-1.5 parts of inorganic porous carrier; The liquid silane mixture is composed of epoxy silane WD-60 and KH560 mixed at a weight ratio of 1:(1-2); the inorganic porous carrier has a specific surface area of ​​150-250. Precipitation method for silica or ultrafine kaolin.

4. The waterproof and crack-resistant dry-mixed mortar according to claim 1, characterized in that, The modified fiber is composed of polypropylene fiber and wood fiber in a weight ratio of 2:1 to 3:1, and the modified fiber is prepared by the following method: S1. After mixing polypropylene fibers and wood fibers, immerse them in a solution of 396-5% NaOH and 1%-2% [unclear - possibly a specific solution or solution]. In the composite activation solution, stir at 40-50°C for 30-40 minutes; S2. After washing until neutral, immerse in a 10%-15% potassium ether carboxylate aqueous solution and let stand for 5-8 hours. S3. Filter out and dry at 60-70°C. The coating layer formed on the fiber surface by the potassium alcohol ether carboxylate enhances the dispersion activity of the fiber in the dry powder system.

5. The waterproof and crack-resistant dry-mixed mortar according to claim 1, characterized in that, The fineness modulus of the graded manufactured sand is 2.3-2.8; the cellulose ether is hydroxypropyl methylcellulose with a viscosity of 40,000-60,000 mPa·s. .

6. A method for preparing a waterproof and crack-resistant dry-mixed mortar, characterized in that, The preparation of the waterproof and crack-resistant dry-mixed mortar according to any one of 1-5 includes the following steps: S1. Weigh each component raw material according to its weight parts; S2. Add cement, graded manufactured sand, polycarboxylate superplasticizer and cellulose ether into a mixer for homogenization and mixing; S3. While the main shaft is stirring, the high-speed flying knife group is turned on to continuously feed hydrophobic redispersible latex powder and modified fibers. The modified fibers are distributed in three dimensions without clumping in the powder system by high-speed shearing force. S4. Turn off the flying knife assembly, add the powdered composite waterproofing agent, and continue stirring to coat the active waterproofing components onto the surface of the particles; discharge the material and use moisture-proof packaging.

7. The method for preparing a waterproof and crack-resistant dry-mixed mortar according to claim 6, characterized in that: In step S2, the main shaft speed of the mixer is 40-60 r / min, and the mixing time is 3-5 min; In step S3, the speed of the flying knife is 1000-1500 r / min, and the mixing time is 5-8 min; In step S4, the spindle speed is 40-60 r / min, and stirring continues for 5-10 min.

8. The method for preparing a waterproof and crack-resistant dry-mixed mortar according to claim 6, characterized in that, The powdered composite waterproofing agent described in step S4 needs to be pretreated before addition: the liquid silane mixture is sprayed through an atomizing nozzle into an inorganic porous carrier under high-speed stirring, and converted into a flowable powder through pore adsorption, with the spraying time controlled at 10-15 minutes.

9. The method for preparing a waterproof and crack-resistant dry-mixed mortar according to claim 6, characterized in that, In step S3, by controlling the surface alcohol ether carboxylate potassium loading of the modified fiber, the initial consistency of the resulting dry-mixed mortar after adding water and stirring is maintained at 90-95 mm, and the consistency loss rate is less than 10% after 1 hour.

10. The method for preparing a waterproof and crack-resistant dry-mixed mortar according to claim 6, characterized in that, At the application site, the total mass ratio of water to dry powder of dry-mixed mortar should be controlled at 0.18-0.22.

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