Polymer modifier for ultra-high performance concrete and preparation method thereof

Abstract

The invention provides a polymer modifier for ultra-high performance concrete and a preparation method of the polymer modifier, and belongs to the technical field of concrete admixtures. The multifunctional polymer modifier provided by the invention can make all indexes such as compressive strength, impermeability and frost resistance of ultra-high performance concrete reach or exceed predetermined targets. Microstructure analysis proves that the modifier forms a continuous polymer film structure in a cement matrix, and the synergistic effect of strengthening, toughening and durability improvement is achieved by combining the modifier with the nano filler. According to the invention, the compatibility of the modifier and a concrete matrix is improved, and uniform dispersion and stable existence of the modifier in concrete are ensured; and the production cost of the modifier is reduced, the preparation process is simple, and industrial production is easy.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and more particularly to a polymer modifier for ultra-high performance concrete and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC) has been widely used in construction engineering in recent years due to its high strength, high durability, and excellent crack resistance. As the requirements for material performance in building structures continue to increase, traditional concrete is no longer sufficient. UHPC, by adding specific modifiers, can significantly improve its mechanical properties and durability. However, the types of existing modifiers are limited, and most suffer from problems such as single function, high cost, or poor compatibility with the concrete matrix, which restricts the further promotion and application of UHPC.

[0003] Currently, common UHPC modifiers mainly include inorganic modifiers such as silica fume, slag powder, and nanomaterials, as well as organic modifiers such as latex powder and acrylic emulsions. Silica fume and slag powder can improve the density and strength of concrete, but they can easily lead to a decrease in fluidity; although nanomaterials can significantly improve the performance of concrete, they are expensive and their dispersibility is difficult to control; organic modifiers such as latex powder and acrylic emulsions can improve the toughness and crack resistance of concrete, but they have problems such as poor compatibility with cementitious matrices and insufficient durability.

[0004] Existing modifiers generally suffer from drawbacks such as limited functionality, high cost, and poor compatibility with concrete matrices, failing to simultaneously meet the comprehensive requirements of UHPC for high strength, high durability, and good workability. Furthermore, the complex preparation processes of some modifiers increase production costs and limit their application in engineering projects. Summary of the Invention

[0005] The purpose of this invention is to provide a polymer modifier for ultra-high performance concrete and its preparation method, which can simultaneously improve the strength, durability and workability of ultra-high performance concrete, and reduce costs, thus solving the problems of single function and poor compatibility of existing modifiers.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a polymer concrete modifier, comprising the following steps: A polymer concrete modifier is obtained by mixing polymer emulsion, dispersant, nanofiller and stabilizer; The polymer emulsion contains acrylate emulsion and styrene-acrylic emulsion; The dispersant contains a polycarboxylate with a molecular weight of 4500-5500; The nanofiller contains nano-silica and nano-alumina; The stabilizer contains a polyvinyl alcohol solution.

[0007] Preferably, by weight, the polymer emulsion comprises 50-70 parts, the dispersant 1-2 parts, the nanofiller 35-45 parts, and the stabilizer 0.3-0.8 parts.

[0008] Preferably, the weight ratio of acrylate emulsion to styrene-acrylic emulsion in the polymer emulsion is 2.5~3.5:2.

[0009] Preferably, the solid content of the acrylate emulsion is 45-55%; The solid content of the styrene-acrylic emulsion is 45-55%.

[0010] Preferably, the weight ratio of nano-silica to nano-alumina in the nanofiller is 3~5:1; The particle size of the nano-silica is 10~25nm; The particle size of the nano-alumina is 30~50nm.

[0011] Preferably, the polyvinyl alcohol solution has a weight percentage concentration of 8-12%.

[0012] Preferably, the mixing process includes first mixing the polymer emulsion with a dispersant, treating it at 600-800 rpm for 10-20 min, then adding the nanofiller at 800-1000 rpm and mixing for 30-50 min, and finally adding the stabilizer and mixing at 400-600 rpm for 15-25 min.

[0013] The present invention also provides a polymer concrete modifier prepared by the above preparation method.

[0014] This invention also provides the application of the above-mentioned polymer concrete modifier in the modification of ultra-high performance concrete.

[0015] Preferably, the polymer concrete modifier is added at a dosage of 2-4% in ultra-high performance concrete.

[0016] The technical effects and advantages of this invention are as follows: The multifunctional polymer modifier provided by this invention can increase the compressive strength of ultra-high performance concrete by 20.73%, improve its impermeability and frost resistance by 32.36% and 25.71% respectively, and reduce the elemental distribution variation coefficient to 0.28. All indicators meet or exceed the predetermined targets. Microstructural analysis confirms that the modifier forms a continuous polymer film structure in the cement matrix, achieving a synergistic effect of strengthening, toughening, and improving durability in combination with nanofillers. This invention not only improves the compatibility of the modifier with the concrete matrix, ensuring its uniform dispersion and stable existence in concrete, but also reduces the production cost of the modifier, with a simple preparation process that is easy for industrial production. Detailed Implementation

[0017] This invention provides a method for preparing a polymer concrete modifier, comprising the following steps: A polymer concrete modifier is obtained by mixing a polymer emulsion, a dispersant, a nanofiller, and a stabilizer; the polymer emulsion contains acrylate emulsion and styrene-acrylic emulsion; the dispersant contains polycarboxylate with a molecular weight of 4500-5500; the nanofiller contains nano-silica and nano-alumina; and the stabilizer contains a polyvinyl alcohol solution.

[0018] In this invention, preferably, by weight, the polymer emulsion comprises 50-70 parts, the dispersant 1-2 parts, the nanofiller 35-45 parts, and the stabilizer 0.3-0.8 parts. Preferably, the weight ratio of the acrylate emulsion to the styrene-acrylic emulsion in the polymer emulsion is 2.5-3.5:2. Preferably, the solid content of the acrylate emulsion is 45-55%; the solid content of the styrene-acrylic emulsion is 45-55%. Preferably, the weight ratio of nano-silica to nano-alumina in the nanofiller is 3-5:1; the particle size of the nano-silica is 10-25 nm; the particle size of the nano-alumina is 30-50 nm. Preferably, the weight percentage concentration of the polyvinyl alcohol solution is 8-12%. Preferably, the mixing process includes first mixing the polymer emulsion with a dispersant, treating it at 600-800 rpm for 10-20 min, then adding the nanofiller at 800-1000 rpm and mixing for 30-50 min, and finally adding the stabilizer and mixing at 400-600 rpm for 15-25 min.

[0019] The present invention also provides a polymer concrete modifier prepared by the above preparation method.

[0020] This invention also provides the application of the above-mentioned polymer concrete modifier in the modification of ultra-high performance concrete. Preferably, the dosage of the polymer concrete modifier in ultra-high performance concrete is 2-4%.

[0021] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0022] Example 1 In this embodiment, the modifier polymer emulsion is composed of acrylate emulsion and styrene-acrylic emulsion in a weight ratio of 3:2. The solid content of both emulsions is controlled within the range of 48%-52%, and the amount added accounts for 60% of the modifier system.

[0023] The nanofiller is a mixture of nano-silica and nano-alumina in a weight ratio of 4:1. The particle size of the former is strictly limited to 15-25nm, and the particle size of the latter is 30-50nm. The amount added accounts for 38% of the modifier system.

[0024] The dispersant is a polycarboxylate with a molecular weight of 4500-5500 (commercially available product, item number A04506114), and the stabilizer is polyvinyl alcohol with a degree of polymerization of 1600-1800. The total amount of both is 2% of the modifier system, and the dispersant and stabilizer are mixed in a weight ratio of 3:1.

[0025] Preparation process: First, the polymer emulsion and dispersant were mechanically stirred at 700 rpm for 15 minutes at 25±2℃ to achieve pre-dispersion. Then, the nanofiller was slowly added in three batches at 5-minute intervals, maintaining a stirring speed of 900 rpm to avoid local agglomeration. This stage lasted for a total of 40 minutes. Finally, a polyvinyl alcohol solution (10%, 10g polyvinyl alcohol dissolved in 100g water) pre-dissolved in 70℃ warm water was added, and stirring was continued at 500 rpm for 20 minutes to complete the stabilization treatment.

[0026] The standard mix proportion for the ultra-high performance concrete is as follows: 780 kg / m³ of 52.5 grade silicate cement, 10% silica fume (as a percentage of the total cementitious material), and aggregate system consisting of quartz sand (0.1-0.6 mm particle size) and quartz powder (below 40 μm particle size) in a 2:1 weight ratio, with an aggregate-to-binder ratio of 1.1:1. A polycarboxylate superplasticizer is added, and the water-to-binder ratio is strictly controlled at 0.19. A modifier is added at 3% of the cement mass, and steel fiber is added at 2% by volume, with an aspect ratio of 65. The mixing process ensures that the modifier is evenly added during the dry mixing stage, and the wet mixing time is extended to 1.5 times that of conventional processes (360 seconds in this example) to ensure sufficient dispersion.

[0027] Example 2 In this embodiment, the modifier polymer emulsion is composed of acrylate emulsion and styrene-acrylic emulsion in a weight ratio of 2.5:2. The solid content of both emulsions is controlled within the range of 48%-52%, and the amount added accounts for 60% of the modifier system.

[0028] The nanofiller is a mixture of nano-silica and nano-alumina in a weight ratio of 4:1. The particle size of the former is strictly limited to 15-25nm, and the particle size of the latter is 30-50nm. The amount added accounts for 38% of the modifier system.

[0029] The dispersant is a polycarboxylate with a molecular weight of 4500-5500, and the stabilizer is a polyvinyl alcohol with a degree of polymerization of 1600-1800. The total amount of both is 2% of the modifier system, and the dispersant and stabilizer are mixed in a weight ratio of 3:1.

[0030] Preparation process: First, the polymer emulsion and dispersant were mechanically stirred at 700 rpm for 15 minutes at 25±2℃ to achieve pre-dispersion. Then, the nanofiller was slowly added in three batches at 5-minute intervals, maintaining a stirring speed of 900 rpm to avoid local agglomeration. This stage lasted for a total of 30 minutes. Finally, a 10% polyvinyl alcohol solution (10g of polyvinyl alcohol dissolved in 100g of water) was added and stirred at 500 rpm for 20 minutes to complete the stabilization treatment.

[0031] The standard mix proportion for the ultra-high performance concrete is as follows: 780 kg / m³ of 52.5 grade silicate cement, 10% silica fume (as a percentage of the total cementitious materials), and an aggregate system consisting of quartz sand (0.1-0.6 mm particle size) and quartz powder (5-40 μm particle size) at a weight ratio of 2:1, with an aggregate-to-binder ratio of 1.1:1. A polycarboxylate superplasticizer is added, and the water-to-binder ratio is strictly controlled at 0.19. A modifier is added at 4% of the cement mass, and steel fiber is added at a volume fraction of 2%, with an aspect ratio of 65. The mixing process ensures that the modifier is evenly added during the dry mixing stage, and the wet mixing time is extended to 1.5 times that of conventional processes (360 seconds in this example) to ensure sufficient dispersion.

[0032] Example 3 In this embodiment, the modifier polymer emulsion is composed of acrylate emulsion and styrene-acrylic emulsion in a weight ratio of 3.5:2. The solid content of both emulsions is controlled within the range of 48%-52%, and the amount added accounts for 60% of the modifier system.

[0033] The nanofiller is a mixture of nano-silica and nano-alumina in a 3:1 weight ratio. The particle size of the former is strictly limited to 15-25nm, and the particle size of the latter is 30-50nm. The amount added accounts for 38% of the modifier system.

[0034] The dispersant is a polycarboxylate with a molecular weight of 4500-5500, and the stabilizer is a polyvinyl alcohol with a degree of polymerization of 1600-1800. The total amount of both is 2% of the modifier system, and the dispersant and stabilizer are mixed in a weight ratio of 3:1.

[0035] Preparation process: First, the polymer emulsion and dispersant were mechanically stirred at 600 rpm for 15 minutes at 25±2℃ to achieve pre-dispersion. Then, the nanofiller was slowly added in three batches at 5-minute intervals, maintaining a stirring speed of 1000 rpm to avoid local agglomeration. This stage lasted for a total of 50 minutes. Finally, a 10% polyvinyl alcohol solution (10g of polyvinyl alcohol dissolved in 100g of water) was added and stirred at 400 rpm for 20 minutes to complete the stabilization treatment.

[0036] The standard mix proportion for the ultra-high performance concrete is as follows: 780 kg / m³ of 52.5 grade silicate cement, 12% silica fume (as a percentage of total cementitious materials), and aggregate system consisting of quartz sand (0.1-0.6 mm particle size) and quartz powder (5-40 μm particle size) in a 2:1 weight ratio, with an aggregate-to-binder ratio of 1.1:1. A polycarboxylate superplasticizer is added, and the water-to-binder ratio is strictly controlled at 0.19. A modifier is added at 3% of the cement mass, and steel fiber is added at 2% by volume, with an aspect ratio of 65. The mixing process ensures that the modifier is evenly added during the dry mixing stage, and the wet mixing time is extended to 1.5 times that of conventional processes (360 seconds in this example) to ensure sufficient dispersion.

[0037] Example 4 In this embodiment, the modifier polymer emulsion is composed of acrylate emulsion and styrene-acrylic emulsion in a weight ratio of 3:2. The solid content of both emulsions is controlled within the range of 48%-52%, and the amount added accounts for 60% of the modifier system.

[0038] The nanofiller is a mixture of nano-silica and nano-alumina in a weight ratio of 4:1. The particle size of the former is strictly limited to 15-25nm, and the particle size of the latter is 30-50nm. The amount added accounts for 38% of the modifier system.

[0039] The dispersant is a polycarboxylate with a molecular weight of 4500-5500, and the stabilizer is a polyvinyl alcohol with a degree of polymerization of 1600-1800. The total amount of both is 2% of the modifier system, and the dispersant and stabilizer are mixed in a weight ratio of 4:1.

[0040] Preparation process: First, the polymer emulsion and dispersant were mechanically stirred at 800 rpm for 15 minutes at 25±2℃ to achieve pre-dispersion. Then, the nanofiller was slowly added in three batches at 5-minute intervals, maintaining a stirring speed of 1000 rpm to avoid local agglomeration. This stage lasted a total of 30 minutes. Finally, a 10% polyvinyl alcohol solution (10g of polyvinyl alcohol dissolved in 100g of water) was added and stirred at 600 rpm for 20 minutes to complete the stabilization treatment.

[0041] The standard mix proportion for the ultra-high performance concrete is as follows: 780 kg / m³ of 52.5 grade silicate cement, 10% silica fume (as a percentage of the total cementitious materials), and an aggregate system consisting of quartz sand (0.1-0.6 mm particle size) and quartz powder (5-40 μm particle size) in a 3:1 weight ratio, with an aggregate-to-binder ratio of 1.1:1. A polycarboxylate superplasticizer is added, and the water-to-binder ratio is strictly controlled at 0.17. A modifier is added at 3% of the cement mass, and steel fiber is added at 2% by volume, with an aspect ratio of 65. The mixing process ensures that the modifier is evenly added during the dry mixing stage, and the wet mixing time is extended to 1.5 times that of conventional processes (360 seconds in this example) to ensure sufficient dispersion.

[0042] Example 5 In this embodiment, the modifier polymer emulsion is composed of acrylate emulsion and styrene-acrylic emulsion in a weight ratio of 3:2. The solid content of both emulsions is controlled within the range of 48%-52%, and the amount added accounts for 60% of the modifier system.

[0043] The nanofiller is a mixture of nano-silica and nano-alumina in a weight ratio of 4:1. The particle size of the former is strictly limited to 15-25nm, and the particle size of the latter is 20-40nm. The amount added accounts for 38% of the modifier system.

[0044] The dispersant is a polycarboxylate with a molecular weight of 4500-5500, and the stabilizer is a polyvinyl alcohol with a degree of polymerization of 1600-1800. The total amount of both is 2% of the modifier system, and the dispersant and stabilizer are mixed in a weight ratio of 3:1.

[0045] Preparation process: First, the polymer emulsion and dispersant were mechanically stirred at 800 rpm for 20 minutes at 30±2℃ to achieve pre-dispersion. Then, the nanofiller was slowly added in three batches at 5-minute intervals, maintaining a stirring speed of 9000 rpm to avoid local agglomeration. This stage lasted for a total of 40 minutes. Finally, a 10% polyvinyl alcohol solution (10g polyvinyl alcohol dissolved in 100g water) was added and stirred at 400 rpm for 20 minutes to complete the stabilization treatment.

[0046] The standard mix proportion for the ultra-high performance concrete is as follows: 820 kg / m³ of 52.5 grade silicate cement, 10% silica fume (as a percentage of the total cementitious materials), and aggregate system consisting of quartz sand (0.1-0.6 mm particle size) and quartz powder (5-40 μm particle size) in a 2:1 weight ratio, with an aggregate-to-binder ratio of 1.1:1. A polycarboxylate superplasticizer is added, and the water-to-binder ratio is strictly controlled at 0.19. A modifier is added at 3% of the cement mass, and steel fiber is added at a volume fraction of 2.5%, with an aspect ratio of 65. The mixing process ensures that the modifier is evenly added during the dry mixing stage, and the wet mixing time is extended to 1.5 times that of conventional processes (360 seconds in this example) to ensure sufficient dispersion.

[0047] Experimental Example I. Experimental Design This experiment involved two groups of concrete specimens for parallel comparison. The control group used standard concrete without polymer modifier, while the experimental group used optimized concrete with the modifier described in Example 1 (3% of cement mass). All specimens were treated with the same curing regime: after curing in a standard curing room (20±2℃, relative humidity ≥95%) for 24 hours, they were demolded and then transferred to saturated lime water at 20±1℃ for curing until the specified age.

[0048] II. Performance Testing Scheme (a) Mechanical property testing Compressive strength test Six groups of 100mm×100mm×100mm cubic specimens were prepared (three groups for the control group and three groups for the experimental group), and their compressive strength was tested at 3d, 7d, and 28d. Before testing, the surface of the specimens was sanded smooth. A computer-controlled electro-hydraulic servo pressure testing machine (range 3000kN, accuracy ±1%) was used to apply the load according to GB / T 50081-2019 standard, with the loading rate controlled at 0.8MPa / s ± 0.1MPa / s. The peak load was recorded and the compressive strength value was calculated. The testing time for a single specimen was controlled within the range of 90-120s.

[0049] Flexural strength and fracture energy test Six sets of 400mm×100mm×100mm prism specimens were prepared. The three-point bending method was used for testing, with a span of 300mm and a loading rate of 0.08mm / min. The flexural strength (according to GB / T 50081-2019) and fracture energy (according to RILEM TC 50-FMC standard) were calculated using load-displacement curves. The fracture energy was calculated as G_F=(W_0+mgδ_0) / (b(da)), where W_0 is the work done by the load, b and d are the width and height of the specimen, and a is the notch depth.

[0050] (ii) Durability testing Water resistance test Three sets of cylindrical specimens with a diameter of 175 mm and a diameter of 150 mm were prepared, and an improved chloride ion penetration resistance test was conducted according to GB / T 50082-2009. After vacuum saturation with water, the specimens were energized at 60 V DC for 6 hours, and the total electrical flux through the specimens was measured. Simultaneously, capillary water absorption rate was tested, and the cumulative water absorption mass over 72 hours was recorded.

[0051] Antifreeze performance test Three sets of 100mm×100mm×400mm prism specimens were tested using the rapid freezing method (GB / T 50082-2009). The freeze-thaw cycle temperature was controlled between -18℃±2℃ and +5℃±2℃, with each cycle lasting 4 hours. The mass loss rate and relative dynamic elastic modulus were measured every 25 cycles, and the dynamic elastic modulus was determined using the resonant frequency method.

[0052] (III) Microstructure Characterization Scanning electron microscopy (SEM) analysis Internal samples were obtained from 28-day-old specimens after crushing. After vacuum drying and gold sputtering, the morphology of the interfacial transition region was observed under an accelerating voltage of 15 kV. The distribution of nanofillers and the integrity of the polymer film structure were analyzed in detail.

[0053] EDS surface scanning analysis The elemental surface distribution of the selected region (50μm×50μm) was scanned, the uniformity coefficients of Si, Al and Ca elemental distribution were statistically analyzed, and the coefficient of variation (CV) value was calculated to evaluate the dispersion uniformity.

[0054] III. Experimental Results Table 1 Mechanical performance test results

[0055] Table 2 Durability Test Results

[0056] Table 3 Microscopic Analysis Data

[0057] IV. Results Analysis The experimental group of concrete achieved a 28-day compressive strength of 183.94 MPa, a 20.73% increase compared to the control group. Flexural strength and fracture energy increased by 25.11% and 35.60%, respectively, indicating that the modifier effectively improved mechanical properties through the synergistic effect of nanofiller reinforcement and polymer toughening. A 32.36% decrease in electrical flux and a 32.42% decrease in water absorption confirm a significant densification effect. After 300 freeze-thaw cycles, the mass loss rate decreased by 25.71%, demonstrating that the polymer network effectively buffered frost heave stress. Microscopic analysis showed a 44.24% reduction in interfacial porosity and a 40.43% reduction in the coefficient of variation of Si element distribution in the experimental group. Combined with an 89.32% polymer film coverage, this demonstrates that the modifier achieved good dispersion stability.

[0058] V. Experimental Conclusions This solution, through systematic performance testing, confirms that the multifunctional polymer modifier can increase the compressive strength of ultra-high performance concrete by 20.73%, improve its impermeability and frost resistance by 32.36% and 25.71% respectively, and reduce the elemental distribution variation coefficient to 0.28. All indicators meet or exceed the predetermined targets. Microstructural analysis confirms that the modifier forms a continuous polymer film structure in the cement matrix, achieving a synergistic effect of reinforcement, toughening, and durability improvement in combination with nanofillers.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer concrete modifier, characterized in that, Includes the following steps: A polymer concrete modifier is obtained by mixing polymer emulsion, dispersant, nanofiller and stabilizer; The polymer emulsion contains acrylate emulsion and styrene-acrylic emulsion; The dispersant contains a polycarboxylate with a molecular weight of 4500-5500; The nanofiller contains nano-silica and nano-alumina; The stabilizer contains a polyvinyl alcohol solution.

2. The preparation method according to claim 1, characterized in that, The polymer emulsion comprises 50-70 parts by weight, the dispersant comprises 1-2 parts by weight, the nanofiller comprises 35-45 parts by weight, and the stabilizer comprises 0.3-0.8 parts by weight.

3. The preparation method according to claim 1, characterized in that, The weight ratio of acrylate emulsion to styrene-acrylic emulsion in the polymer emulsion is 2.5~3.5:

2.

4. The preparation method according to claim 1, characterized in that, The solid content of the acrylate emulsion is 45-55%; The solid content of the styrene-acrylic emulsion is 45-55%.

5. The preparation method according to claim 1, characterized in that, The weight ratio of nano-silica to nano-alumina in the nanofiller is 3~5:1; The particle size of the nano-silica is 10~25nm; The particle size of the nano-alumina is 30~50nm.

6. The preparation method according to claim 1, characterized in that, The polyvinyl alcohol solution has a weight percentage concentration of 8-12%.

7. The preparation method according to claim 1, characterized in that, The mixing process includes first mixing the polymer emulsion with a dispersant, treating it at 600-800 rpm for 10-20 min, then adding the nanofiller at 800-1000 rpm and mixing for 30-50 min, and finally adding the stabilizer and mixing at 400-600 rpm for 15-25 min.

8. A polymer concrete modifier prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the polymer concrete modifier according to claim 8 in the modification of ultra-high performance concrete.

10. The application according to claim 9, characterized in that, The polymer concrete modifier is added at a dosage of 2-4% in ultra-high performance concrete.

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