Ultra-high performance concrete admixture, preparation method and application thereof

Abstract

The application discloses an ultra-high performance concrete admixture and a preparation method and application thereof, and the ultra-high performance concrete admixture comprises the following components in percentage by mass: 35-50% of mineral powder, 20-30% of white carbon black, 15-25% of cummingtonite, 5-15% of hollow glass microbead, 2-4% of modified latex powder, 2-4% of modified calcium sulfate whisker, 2-4% of synergist, 0.2-0.5% of viscosity reducer and 0.03-0.1% of shrinkage reducing agent. The ultra-high performance concrete admixture can improve the mechanical property, working property and late shrinkage of the ultra-high performance concrete, and is applicable to both coarse aggregate and fine aggregate, and has better applicability.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to an ultra-high performance concrete admixture, its preparation method, and its application. Background Technology

[0002] Ultra-high performance concrete (UHVPC) is a new type of cement-based composite material with ultra-high mechanical properties. It achieves its ultra-high performance by eliminating coarse aggregates, reducing the water-cement ratio, using highly active admixtures, and achieving the densest packing. However, the design of ultra-high cementitious material usage and ultra-low water-cement ratio can lead to problems such as high mixture viscosity, difficulty in removing air bubbles, plastic shrinkage, and large late-stage shrinkage in UHVPC, which in turn affect the mechanical properties, workability, and late-stage shrinkage of UHVPC. Summary of the Invention

[0003] The main objective of this invention is to propose an ultra-high performance concrete admixture, its preparation method, and its application, aiming to solve the problems of high viscosity of existing ultra-high performance concrete mixtures, difficulty in removing air bubbles, large plastic shrinkage, and large late-stage shrinkage, which in turn affect the mechanical properties, workability, and late-stage shrinkage of ultra-high performance concrete.

[0004] To achieve the above objectives, this invention proposes an ultra-high performance concrete admixture, comprising the following components by mass percentage: 35-50% mineral powder, 20-30% silica, 15-25% palladium, 5-15% hollow glass microspheres, 2-4% modified latex powder, 2-4% modified calcium sulfate whiskers, 2-4% synergist, 0.2-0.5% viscosity reducer, and 0.03-0.1% shrinkage inhibitor.

[0005] Optionally, the ore powder includes refined mixed slag powder, ferronickel slag powder from electric arc furnaces, and ferronickel slag powder from blast furnaces; and / or,

[0006] The surface area of ​​the mineral powder is 500-650 m². 2 / kg; and / or,

[0007] The fluidity ratio of the mineral powder is 105-110%; and / or,

[0008] The 7-day activity index of the mineral powder is 96-98%; and / or,

[0009] The 28-day activity index of the mineral powder is 105–110%.

[0010] Optionally, the silica content in the precipitated silica is greater than or equal to 98%; and / or,

[0011] The content of particles with a fineness of less than 1 μm in the precipitated silica is greater than or equal to 80%; and / or,

[0012] The average particle size of the silica is 0.1–0.2 μm.

[0013] Optionally, the grain size of the rettosite is less than 2 μm; and / or,

[0014] The modified calcium sulfate whiskers have a particle size of 50–100 nm; and / or,

[0015] The synergist comprises 40-50% cryolite, 20-30% heavy calcium carbonate, and 20-30% sodium metasilicate pentahydrate; and / or,

[0016] The viscosity reducer includes at least one of oxalic acid, polyaspartic acid, and ethylenediaminetetraacetic acid; and / or,

[0017] The shrinkage inhibitor includes at least one of a modified water-absorbing resin and a water-absorbing resin; and / or, the shrinkage inhibitor includes a modified water-absorbing resin having a particle size of 0.4 to 0.6 mm.

[0018] Optionally, the spherical density of the hollow glass microspheres is 2.0–2.5 g / cm³. 3 ; and / or,

[0019] The bulk density of the hollow glass microspheres is 0.5–0.7 g / cm³. 3 ; and / or,

[0020] The hollow glass microspheres contain 52% or more silica; and / or,

[0021] The 7-day activity index of the hollow glass microspheres is greater than 80%; and / or,

[0022] The 28-day activity index of the hollow glass microspheres is greater than 110%.

[0023] Optionally, the preparation method of the modified latex powder includes the following steps:

[0024] Polyvinyl alcohol, sodium bentonite, and water are mixed to obtain a mixed solution;

[0025] Sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate were added to the mixed solution and stirred to obtain a pre-emulsified solution.

[0026] The pre-emulsified solution was heat-treated, polyvinyl acetate was added dropwise, and an initiator solution was added in portions. The mixture was then kept warm and stirred to obtain an intermediate solution.

[0027] After cooling, dibutyl phthalate was added and stirred to obtain an emulsion;

[0028] The emulsion is demulsified, filtered, and dried to obtain modified latex powder.

[0029] Optionally, the method for preparing the modified calcium sulfate whiskers includes the following steps:

[0030] The silane coupling agent was mixed with an ethanol solution, and then fumed nano-silica was added. The mixture was stirred and shaken to obtain a suspension.

[0031] The suspension was heated, calcium sulfate whiskers were added, and then the mixture was kept at the temperature and stirred to obtain a modified calcium sulfate whisker mixture.

[0032] The modified calcium sulfate whisker mixture was washed, filtered, and vacuum dried to obtain modified calcium sulfate whiskers.

[0033] Optionally, the shrinkage inhibitor includes a modified water-absorbing resin, and the preparation method of the modified water-absorbing resin includes the following steps:

[0034] The water-absorbing resin was soaked in a calcium nitrate solution, shaken, and ball-milled to obtain the modified water-absorbing resin.

[0035] This invention also proposes a method for preparing the ultra-high performance concrete admixture as described above, comprising the following steps:

[0036] Mineral powder, silica, palladium, hollow glass microspheres, modified latex powder, modified calcium sulfate whiskers, synergist, viscosity reducer, and shrinkage inhibitor are homogenized to obtain an ultra-high performance concrete admixture.

[0037] The present invention also proposes an ultra-high performance concrete, comprising aggregates, and ultra-high performance concrete admixtures as described above or ultra-high performance concrete admixtures prepared by the preparation method of ultra-high performance concrete admixtures as described above; wherein the aggregates comprise at least one of coarse aggregates and fine aggregates.

[0038] In the technical solution of this invention, mineral powder can fill the voids in concrete, thereby improving the strength of ultra-high performance concrete; palladium and modified calcium sulfate whiskers can introduce micron-sized crystalline fibers to fill the fine lattice cracks in concrete, significantly reducing the fine cracks caused by the ultra-low water-cement ratio, and improving the compressive and tensile strength of ultra-high performance concrete; the synergistic effect of silica, hollow glass microspheres, modified latex powder, and viscosity reducers can effectively reduce the viscosity of concrete and improve the fluidity of ultra-high performance concrete; the synergist can accelerate the hydration efficiency of concrete and improve the strength of ultra-high performance concrete; the shrinkage inhibitor can suppress the plastic shrinkage and later shrinkage of concrete; thus, it can improve the mechanical properties, workability, and later shrinkage of ultra-high performance concrete; in addition, both coarse and fine aggregates are applicable, making it more versatile. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0040] It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0041] Ultra-high performance concrete (UHVPC) is a new type of cement-based composite material with ultra-high mechanical properties. It achieves its ultra-high performance by eliminating coarse aggregates, reducing the water-cement ratio, using highly active admixtures, and achieving the densest packing. However, the design of ultra-high cementitious material usage and ultra-low water-cement ratio can lead to problems such as high mixture viscosity, difficulty in removing air bubbles, plastic shrinkage, and large late-stage shrinkage in UHVPC, which in turn affect the mechanical properties, workability, and late-stage shrinkage of UHVPC.

[0042] In view of this, the present invention proposes an ultra-high performance concrete admixture, its preparation method and application, which can improve the mechanical properties, workability and later shrinkage of ultra-high performance concrete.

[0043] In some embodiments of the present invention, the ultra-high performance concrete admixture comprises, by mass percentage, the following components: 35-50% mineral powder, 20-30% silica, 15-25% palladium, 5-15% hollow glass microspheres, 2-4% modified latex powder, 2-4% modified calcium sulfate whiskers, 2-4% synergist, 0.2-0.5% viscosity reducer, and 0.03-0.1% shrinkage inhibitor.

[0044] In the technical solution of this invention, mineral powder can fill the voids in concrete, thereby improving the strength of ultra-high performance concrete; palladium and modified calcium sulfate whiskers can introduce micron-sized crystalline fibers to fill the fine lattice cracks in concrete, significantly reducing the fine cracks caused by the ultra-low water-cement ratio, and improving the compressive and tensile strength of ultra-high performance concrete; the synergistic effect of silica, hollow glass microspheres, modified latex powder, and viscosity reducers can effectively reduce the viscosity of concrete and improve the fluidity of ultra-high performance concrete; the synergist can accelerate the hydration efficiency of concrete and improve the strength of ultra-high performance concrete; the shrinkage inhibitor can suppress the plastic shrinkage and later shrinkage of concrete; thus, it can improve the mechanical properties, workability, and later shrinkage of ultra-high performance concrete; in addition, both coarse and fine aggregates are applicable, making it more versatile.

[0045] In some embodiments of the present invention, the mineral powder includes refined mixed slag powder, electric arc furnace nickel-iron slag powder, and blast furnace nickel-iron slag powder, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the mineral powder can be obtained by grinding the refined mixed slag, electric arc furnace nickel-iron slag, and blast furnace nickel-iron slag with an organic grinding aid, wherein the mass ratio of the refined mixed slag, electric arc furnace nickel-iron slag, and blast furnace nickel-iron slag is (3-5):(2-4):(2-4), preferably 4:3:3.

[0046] In some embodiments of the present invention, the surface area of ​​the mineral powder is 500–650 m². 2 / kg, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the surface area of ​​the mineral powder can be 500m². 2 / kg, 550m 2 / kg, 600m 2 / kg or 650m 2 / kg.

[0047] In some embodiments of the present invention, the fluidity ratio of the mineral powder is 105-110%, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the fluidity ratio is 105%, 107%, or 110%.

[0048] In some embodiments of the present invention, the 7-day activity index of the mineral powder is 96-98%, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the 7-day activity index of the mineral powder can be 96%, 97% or 98%.

[0049] In some embodiments of the present invention, the 28-day activity index of the mineral powder is 105-110%, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the 28-day activity index of the mineral powder can be 105%, 108%, or 110%.

[0050] In some embodiments of the present invention, the silica content in the precipitated silica is greater than or equal to 98%, which can improve the fluidity of concrete and is beneficial to improving the workability of ultra-high performance concrete; the silica content in the precipitated silica can be 98.0%, 98.5%, or 99.0%.

[0051] In some embodiments of the present invention, the content of particles with a fineness of less than 1 μm in the silica is greater than or equal to 80%, which can improve the fluidity of concrete and is beneficial to improving the workability of ultra-high performance concrete; the content of particles with a fineness of less than 1 μm in the silica can be 80%, 82%, 84% or 86%.

[0052] In some embodiments of the present invention, the average particle size of the silica is 0.1 to 0.2 μm, which can improve the fluidity of concrete and is beneficial to improving the workability of ultra-high performance concrete; the average particle size of the silica can be 0.1 μm, 0.15 μm or 0.2 μm.

[0053] In some embodiments of the present invention, the particle size of the attapulgite is less than 2 μm, which can fill the fine cracks in concrete and is beneficial to improving the mechanical properties of ultra-high performance concrete; the particle size of the attapulgite can be 1 μm, 1.4 μm or 1.8 μm; it can be understood that the attapulgite is an aluminosilicate mineral with a scaly or fibrous crystal structure.

[0054] In some embodiments of the present invention, the modified calcium sulfate whiskers have a particle size of 50-100 nm, which can fill the fine cracks in concrete and is beneficial to improving the mechanical properties of ultra-high performance concrete; the particle size of the modified calcium sulfate whiskers can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0055] In some embodiments of the present invention, the synergist comprises 40-50% cryolite, 20-30% heavy calcium carbonate, and 20-30% sodium metasilicate pentahydrate, which can accelerate the hydration efficiency of concrete and improve the mechanical properties of ultra-high performance concrete; the synergist may be 40% cryolite, 30% heavy calcium carbonate, and 30% sodium metasilicate pentahydrate; or 50% cryolite, 20% heavy calcium carbonate, and 30% sodium metasilicate pentahydrate; or 50% cryolite, 30% heavy calcium carbonate, and 20% sodium metasilicate pentahydrate.

[0056] In some embodiments of the present invention, the viscosity reducer includes at least one of oxalic acid, polyaspartic acid, and ethylenediaminetetraacetic acid, which can improve the fluidity of ultra-high performance concrete and is beneficial to improving the workability of ultra-high performance concrete; the viscosity reducer can be any one or any combination of oxalic acid, polyaspartic acid, and ethylenediaminetetraacetic acid.

[0057] In some embodiments of the present invention, the shrinkage inhibitor includes at least one of modified water-absorbing resin and water-absorbing resin, which can inhibit the plastic shrinkage and later shrinkage of concrete, and is beneficial to improving the mechanical properties and later shrinkage of ultra-high performance concrete; the shrinkage inhibitor can be any one or a combination of two of modified water-absorbing resin and water-absorbing resin.

[0058] In some embodiments of the present invention, the shrinkage inhibitor includes a modified water-absorbing resin with a particle size of 0.4 to 0.6 mm, which can inhibit the plastic shrinkage and later shrinkage of concrete, enhance the structural strength of concrete, and help improve the mechanical properties and later shrinkage of ultra-high performance concrete; the particle size of the modified water-absorbing resin can be 0.4 mm, 0.5 mm or 0.6 mm.

[0059] In some embodiments of the present invention, the spherical density of the hollow glass microspheres is 2.0–2.5 g / cm³. 3 This can improve the fluidity of concrete, which is beneficial for improving the workability of ultra-high performance concrete; the spherical density of the hollow glass microspheres can be 2.0 g / cm³. 3 2.3g / cm 3 Or 2.5g / cm 3 .

[0060] In some embodiments of the present invention, the bulk density of the hollow glass microspheres is 0.5–0.7 g / cm³. 3 This can improve the fluidity of concrete, which is beneficial for improving the workability of ultra-high performance concrete; the bulk density of the hollow glass microspheres can be 0.5 g / cm³. 3 0.6g / cm 3 Or 0.7g / cm 3 .

[0061] In some embodiments of the present invention, the silica content in the hollow glass microspheres is greater than or equal to 52%, which can improve the fluidity of concrete and is beneficial to improving the workability of ultra-high performance concrete; the silica content in the hollow glass microspheres can be 52%, 56% or 60%.

[0062] In some embodiments of the present invention, the 7-day activity index of the hollow glass microspheres is greater than 80%, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the 7-day activity index of the hollow glass microspheres can be 82%, 83%, or 86%.

[0063] In some embodiments of the present invention, the 28-day activity index of the hollow glass microspheres is greater than 110%, which is beneficial to improving the mechanical properties of ultra-high performance concrete; the 28-day activity index of the hollow glass microspheres can be 111%, 113%, or 115%.

[0064] In some embodiments of the present invention, the preparation method of the modified latex powder includes the following steps:

[0065] Step 1: Mix polyvinyl alcohol, sodium bentonite, and water to obtain a mixed solution;

[0066] Step 2: Add sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate to the mixed solution, stir, and obtain a pre-emulsified solution;

[0067] Step 3: Heat-treat the pre-emulsified solution, add polyvinyl acetate dropwise, and add the initiator solution in portions. Then keep it warm and stir to obtain an intermediate solution.

[0068] Step 4: After cooling, add dibutyl phthalate and stir to obtain an emulsion;

[0069] Step 5: Demulsify, filter and dry the emulsion to obtain modified latex powder.

[0070] By modifying latex powder (polyvinyl acetate) with sodium-based bentonite, the "ball effect" of latex powder can be retained to reduce the viscosity of concrete, while increasing the contact area between other ultrafine powders, latex powder and concrete aggregates, enhancing the bonding ability, improving the compressive strength and tensile strength of concrete, and further improving the mechanical properties of ultra-high performance concrete.

[0071] Furthermore, in step 1 of the method for preparing the modified latex powder, in some embodiments, the mass ratio of polyvinyl alcohol, sodium bentonite and water is (3-4):(0.8-1.2):55, preferably 3.5:1:55.

[0072] In step 2 of the method for preparing the modified latex powder, in some embodiments, the mass ratio of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate to water is (0.1-0.2):(0.4-0.6):(7-8):55, preferably 0.15:0.5:7.5:55; in some embodiments, the stirring time is 20-40 min, preferably 30 min; in some embodiments, the polyvinyl acetate is Wacker Chemie 4036N latex powder from Germany.

[0073] In step S3 of the method for preparing the modified latex powder, in some embodiments, the heat treatment temperature is 80-90°C, preferably 85°C; in some embodiments, the heat treatment time is 0.5-2 hours; polyvinyl acetate is added dropwise during the heat treatment, and the initiator solution is added in portions; in some embodiments, the mass ratio of the added polyvinyl acetate to water is (25-26):55, preferably 25.5:55; in some embodiments, the initiator solution is an ammonium persulfate solution (APS solution) with a mass fraction of 5-10%, and the mass ratio of the initiator solution to water is (1.5-2.5):55, preferably 2:55; in some embodiments, the heat preservation and stirring time is 15-25 minutes, preferably 20 minutes.

[0074] In step 4 of the method for preparing the modified latex powder, in some embodiments, the temperature after cooling is below 50°C; in some embodiments, the mass ratio of dibutyl phthalate to water is (3-4):55; preferably 3.5:55; in some embodiments, the stirring time is 3-8 min, preferably 5 min.

[0075] In step 5 of the method for preparing the modified latex powder, in some embodiments, the demulsification method is ultrasonic demulsification; in some embodiments, the filtration method is vacuum filtration; in some embodiments, the drying temperature is 45-55°C, preferably 50°C.

[0076] In some embodiments of the present invention, the method for preparing the modified calcium sulfate whiskers includes the following steps:

[0077] Step a: Mix the silane coupling agent with the ethanol solution, then add fumed nano-silica, stir and shake to obtain a suspension;

[0078] Step b: Heat the suspension, add calcium sulfate whiskers, and then keep it at the temperature while stirring to obtain a modified calcium sulfate whisker mixture.

[0079] Step c: Wash, filter, and vacuum dry the modified calcium sulfate whisker mixture to obtain modified calcium sulfate whiskers.

[0080] Modifying calcium sulfate whiskers with silane coupling agents and nano-silica can improve the mechanical properties of ultra-high performance concrete.

[0081] In step a of the method for preparing modified calcium sulfate whiskers, in some embodiments, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; in some embodiments, the ethanol solution is an ethanol solution with a mass fraction of 80-90%, preferably 85%; in some embodiments, the mass ratio of silane coupling agent to ethanol solution is (1.5-2.5):1, preferably 2:1; in some embodiments, the mass ratio of silane coupling agent to fumed nano-silica is (1.5-3):1; in some embodiments, the particle size of fumed nano-silica is 40-70 nm; in some embodiments, stirring is performed using a magnetic stirrer at a speed of 800-1200 r / min, preferably 1000 r / min; in some embodiments, the stirring time is 20-30 min; in some embodiments, the oscillation method is ultrasonic oscillation, and the oscillation time is 45-60 min.

[0082] In step b of the method for preparing the modified calcium sulfate whiskers, in some embodiments, the temperature of the suspension is 35-45°C, preferably 40°C; in some embodiments, the molar ratio of fumed silica to calcium sulfate whiskers is (1.5-3):1; in some embodiments, the time for heat preservation and stirring is 0.5-1.5h, preferably 1h, and the stirring is carried out at a uniform speed.

[0083] In step c of the method for preparing modified calcium sulfate whiskers, in some embodiments, the modified calcium sulfate whisker mixture is washed by centrifugation with anhydrous ethanol, and the washing is performed more than 3 times; in some embodiments, the filtration method is vacuum filtration.

[0084] In some embodiments of the present invention, the shrinkage inhibitor comprises a modified water-absorbing resin, and the preparation method of the modified water-absorbing resin includes the following steps:

[0085] The water-absorbing resin was soaked in a calcium nitrate solution, then shaken and ball-milled to obtain the modified water-absorbing resin.

[0086] Introducing calcium ions through modification helps to suppress the later-stage shrinkage of ultra-high performance concrete.

[0087] Furthermore, in some embodiments, the concentration of the calcium nitrate solution is 0.04–0.06 mol / ml; in some embodiments, the oscillation method is ultrasonic oscillation; in some embodiments, the oscillation time is 20–30 min; in some embodiments, the ball milling is performed using a planetary ball mill; in some embodiments, the ball milling speed is 2500–3500 r / min, preferably 3000 r / min; in some embodiments, the ball milling time is 30–45 min.

[0088] This invention also proposes a method for preparing ultra-high performance concrete admixtures, comprising the following steps:

[0089] Mineral powder, silica, palladium, hollow glass microspheres, modified latex powder, modified calcium sulfate whiskers, synergist, viscosity reducer, and shrinkage inhibitor are homogenized to obtain an ultra-high performance concrete admixture.

[0090] The preparation method of ultra-high performance concrete admixture is simple, easy to operate, and convenient for production. It is understood that the preparation method of ultra-high performance concrete admixture provided by the present invention adopts the above-mentioned ultra-high performance concrete admixture formula, and therefore possesses all the beneficial effects brought by the ultra-high performance concrete admixture, which will not be elaborated here.

[0091] Furthermore, in some embodiments, homogenization is performed using a homogenizer, in which all components are placed and homogenized at a rotation speed of 200–400 r / min; in some embodiments, the homogenization time is 20–40 min, preferably 30 min.

[0092] This invention also proposes an ultra-high performance concrete, comprising aggregates, and the ultra-high performance concrete admixtures described above or prepared by the aforementioned method; wherein the aggregates include at least one of coarse aggregates and fine aggregates; the ultra-high performance concrete admixtures include all the technical solutions described above, and therefore possess all the beneficial effects brought about by the aforementioned technical solutions, which will not be elaborated further here; the aggregates include any one or a combination of two of coarse aggregates and fine aggregates.

[0093] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0094] Example 1

[0095] An ultra-high performance concrete admixture, by mass percentage, comprises the following components: 40% mineral powder, 25% silica, 15% palladium, 10.7% hollow glass microspheres, 3% modified latex powder, 3% modified calcium sulfate whiskers, 3% synergist, 0.25% viscosity reducer, and 0.05% shrinkage inhibitor; wherein the synergist is a mixture of 40% cryolite, 30% heavy calcium carbonate, and 30% sodium metasilicate pentahydrate, the viscosity reducer is oxalic acid, and the shrinkage inhibitor is modified superabsorbent polymer.

[0096] The preparation method of ultra-high performance concrete admixtures includes the following steps:

[0097] The above components are placed in a homogenizer at a speed of 300 r / min and homogenized for 30 min to obtain ultra-high performance concrete admixture.

[0098] The preparation method of modified latex powder includes the following steps:

[0099] Step 1: Mix polyvinyl alcohol, sodium bentonite, and water to obtain a mixed solution; wherein the mass ratio of polyvinyl alcohol, sodium bentonite, and water is 3.5:1:55.

[0100] Step 2: Add sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate to the mixed solution and stir to obtain a pre-emulsified solution; wherein the mass ratio of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate to water is 0.15:0.5:7.5:55, the stirring time is 30 min, and the polyvinyl acetate is Wacker Chemie 4036N latex powder from Germany;

[0101] Step 3: Heat-treat the pre-emulsified solution, add polyvinyl acetate dropwise, and add the initiator solution in portions, then keep it warm and stir to obtain an intermediate solution; wherein, the heat treatment temperature is 85℃ and the time is 2h, the polyvinyl acetate and the initiator solution are added during the heat treatment, the initiator solution is a 10% ammonium persulfate solution, the mass ratio of the initiator solution to water is 2:55, the temperature for keeping it warm and stirring is 85℃ and the time for keeping it warm and stirring is 20min;

[0102] Step 4: After cooling, add dibutyl phthalate and stir to obtain an emulsion; wherein, the temperature after cooling is below 50℃, the mass ratio of dibutyl phthalate to water is 3.5:55, and the stirring time is 5 minutes;

[0103] Step 5: Demulsify, filter and dry the emulsion to obtain modified latex powder; wherein, the demulsification method is ultrasonic demulsification, the filtration method is vacuum filtration, and the drying temperature is 50℃.

[0104] The preparation method of modified calcium sulfate whiskers includes the following steps:

[0105] Step a: Mix the silane coupling agent with an ethanol solution, then add fumed silica nanoparticles, stir and vibrate to obtain a suspension; wherein, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane, the mass fraction of the ethanol solution is 85%, the mass ratio of the silane coupling agent to the ethanol solution is 2:1, the mass ratio of the silane coupling agent to the fumed silica nanoparticles is 2.2:1, the particle size of the fumed silica nanoparticles is 50nm, the stirring is carried out using a magnetic stirrer at a speed of 1000r / min for 25min, and the vibration is carried out using ultrasonic vibration for 50min;

[0106] Step b: Heat the suspension, add calcium sulfate whiskers, and then keep it at the temperature and stir to obtain a modified calcium sulfate whisker mixture; wherein, the suspension is heated to 40°C, the molar ratio of fumed nano-silica to calcium sulfate whiskers is 2.2:1; the temperature for keeping it at the temperature and stirring is 40°C, and the time for keeping it at the temperature and stirring is 1 hour.

[0107] Step c: Wash, filter and vacuum dry the modified calcium sulfate whisker mixture to obtain modified calcium sulfate whiskers; wherein, the modified calcium sulfate whiskers are washed three times by centrifugation with anhydrous ethanol and filtered by vacuum filtration.

[0108] The preparation method of the modified water-absorbing resin includes the following steps:

[0109] The water-absorbing resin was soaked in a calcium nitrate solution, and then shaken and ball-milled to obtain the modified water-absorbing resin. The concentration of calcium nitrate was 0.05 mol / ml, the shaking method was ultrasonic shaking, the shaking time was 25 min, the ball milling was carried out using a planetary ball mill, the ball milling speed was 3000 r / min, and the heat preservation and stirring time was 40 min.

[0110] Example 2

[0111] Unlike Example 1, the ultra-high performance concrete admixture comprises the following components by weight percentage: 35% mineral powder, 30% silica, 15% palladium, 10.7% hollow glass microspheres, 3% modified latex powder, 3% modified calcium sulfate whiskers, 3% synergist, 0.25% viscosity reducer, and 0.05% shrinkage inhibitor.

[0112] Example 3

[0113] Unlike Example 1, the ultra-high performance concrete admixture comprises the following components by weight percentage: 40% mineral powder, 25% silica, 15% palladium, 10.7% hollow glass microspheres, 4% modified latex powder, 2% modified calcium sulfate whiskers, 3% synergist, 0.25% viscosity reducer, and 0.05% shrinkage inhibitor.

[0114] Example 4

[0115] The difference from Example 1 is that the ultra-high performance concrete admixture, by mass percentage, consists of 40% mineral powder, 25% silica, 15% palladium, 10.7% hollow glass microspheres, 3% modified latex powder, 3% modified calcium sulfate whiskers, 3% synergist, 0.25% viscosity reducer, and 0.05% shrinkage inhibitor; wherein the viscosity reducer is ethylenediaminetetraacetic acid.

[0116] Example 5

[0117] The difference from Example 1 is that the shrinkage inhibitor is a water-absorbing resin.

[0118] Comparative Example 1

[0119] One type of ultra-high performance concrete admixture is silica fume.

[0120] Comparative Example 2

[0121] Unlike Example 1, the latex powder was not modified; the latex powder used was Wacker Chemie 4036N from Germany.

[0122] Comparative Example 3

[0123] Unlike Example 1, the calcium sulfate whiskers were not modified.

[0124] Comparative Example 4

[0125] Unlike Example 1, the latex powder was not modified; the latex powder was Wacker Chemie 4036N from Germany, and the calcium sulfate whiskers were not modified.

[0126] Performance testing:

[0127] The ultra-high performance concrete admixtures of Examples 1-5 and Comparative Examples 1-4 were prepared into coarse aggregate ultra-high performance concrete according to the specified proportions, and their performance was tested. The results are shown in Table 1. The proportions (kg) of the coarse aggregate ultra-high performance concrete were as follows: cement 550kg, admixture 250kg, sand 620kg, crushed stone (5-10mm) 610kg, crushed stone (10-15mm) 390kg, admixture 19.75kg, steel fiber 120kg, and water 136kg.

[0128] The ultra-high performance concrete admixtures of Examples 1-5 and Comparative Examples 1-4 were prepared into fine aggregate ultra-high performance concrete according to the specified proportions, and their performance was tested. The results are shown in Table 2. The proportions (kg) of the coarse aggregate ultra-high performance concrete were as follows: cement 550kg, admixture 450kg, fine quartz sand 850kg, coarse quartz sand 330kg, water 160kg, admixture 24.5kg, and steel fiber 230kg.

[0129] The performance tests include scalar expansion test, T500 test, compressive strength test, and flexural strength test. The scalar expansion test and T500 test are conducted according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures"; the compressive strength test and flexural strength test are conducted according to GB / T 31387-2015 "Reactive Powder Concrete".

[0130] Table 1 Performance test results of coarse aggregate ultra-high performance concrete

[0131]

[0132] Table 2 Performance test results of fine aggregate ultra-high performance concrete

[0133]

[0134] As shown in Table 1, compared with Comparative Examples 1-4, the ultra-high performance concrete of Examples 1-5 can improve the discharge spread, 28-day flexural strength, and 28-day tensile strength, and reduce the air content, T500 time, and 28-day drying shrinkage rate in coarse aggregate ultra-high performance concrete. Compared with Comparative Examples 2-4, the flexural strength and compressive strength of the ultra-high performance concrete of Example 1 are significantly improved. Modified latex powder and modified calcium sulfate whiskers can effectively improve the mechanical properties of coarse aggregate ultra-high performance concrete. This indicates that the ultra-high performance concrete admixture of the present invention can improve the workability and mechanical properties of coarse aggregate ultra-high performance concrete, and reduce the later shrinkage of coarse aggregate ultra-high performance concrete.

[0135] As shown in Table 2, compared with Comparative Examples 1-4, the ultra-high performance concrete of Examples 1-5 can improve the discharge spread, 28-day flexural strength, and 28-day tensile strength, and reduce the air content, T500 time, and 28-day drying shrinkage rate in fine aggregate ultra-high performance concrete. Compared with Comparative Examples 2-4, the ultra-high performance concrete of Example 1 has significantly improved flexural strength and compressive strength. Modified latex powder and modified calcium sulfate whiskers can effectively improve the mechanical properties of fine aggregate ultra-high performance concrete. This indicates that the ultra-high performance concrete admixture of the present invention can improve the workability and mechanical properties of fine aggregate ultra-high performance concrete, and reduce the later shrinkage of fine aggregate ultra-high performance concrete.

[0136] In summary, the ultra-high performance concrete admixture of the present invention can improve the workability and mechanical properties of ultra-high performance concrete, as well as reduce its later-stage shrinkage; at the same time, it is applicable to both coarse and fine aggregates, thus having better applicability.

[0137] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A high-performance concrete admixture, characterized in that, By mass percentage, it includes the following components: The composition includes: 35-50% mineral powder, 20-30% silica, 15-25% attapulgite, 5-15% hollow glass microspheres, 2-4% modified latex powder, 2-4% modified calcium sulfate whiskers, 2-4% synergist, 0.2-0.5% viscosity reducer, and 0.03-0.1% shrinkage inhibitor; among which: The synergist includes 40-50% cryolite, 20-30% heavy calcium carbonate, and 20-30% sodium metasilicate pentahydrate. The preparation method of the modified latex powder includes the following steps: Polyvinyl alcohol, sodium bentonite, and water are mixed to obtain a mixed solution; Sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and polyvinyl acetate were added to the mixed solution and stirred to obtain a pre-emulsified solution. The pre-emulsified solution was heat-treated, polyvinyl acetate was added dropwise, and an initiator solution was added in portions. The mixture was then kept warm and stirred to obtain an intermediate solution. After cooling, dibutyl phthalate was added and stirred to obtain an emulsion; The emulsion is demulsified, filtered, and dried to obtain modified latex powder; The method for preparing the modified calcium sulfate whiskers includes the following steps: The silane coupling agent was mixed with an ethanol solution, and then fumed nano-silica was added. The mixture was stirred and shaken to obtain a suspension. The suspension was heated, calcium sulfate whiskers were added, and then the mixture was kept at the temperature and stirred to obtain a modified calcium sulfate whisker mixture. The modified calcium sulfate whisker mixture was washed, filtered, and vacuum dried to obtain modified calcium sulfate whiskers.

2. The ultra-high performance concrete admixture as described in claim 1, characterized in that, The mineral powder includes refined mixed slag powder, ferronickel slag powder from electric arc furnaces, and ferronickel slag powder from blast furnaces; and / or, The specific surface area of ​​the mineral powder is 500~650m². 2 / kg; and / or, The fluidity ratio of the mineral powder is 105~110%; and / or, The 7-day activity index of the mineral powder is 96-98%; and / or, The 28-day activity index of the mineral powder is 105-110%.

3. The ultra-high performance concrete admixture as described in claim 1, characterized in that, The silica content in the precipitated silica is greater than or equal to 98%; and / or, The content of particles with a fineness of less than 1 μm in the precipitated silica is greater than or equal to 80%; and / or, The average particle size of the silica is 0.1~0.2μm.

4. The ultra-high performance concrete admixture as described in claim 1, characterized in that, The grain size of the rettosite is less than 2 μm; and / or, The modified calcium sulfate whiskers have a particle size of 50-100 nm; and / or, The viscosity reducer includes at least one of oxalic acid, polyaspartic acid, and ethylenediaminetetraacetic acid; and / or, The shrinkage inhibitor includes at least one of a modified water-absorbing resin and a water-absorbing resin.

5. The ultra-high performance concrete admixture as described in claim 4, characterized in that, The shrinkage inhibitor includes a modified water-absorbing resin, wherein the particle size of the modified water-absorbing resin is 0.4~0.6 mm.

6. The ultra-high performance concrete admixture as described in claim 1, characterized in that, The hollow glass microspheres have a spherical density of 2.0~2.5 g / cm³. 3 ; and / or, The bulk density of the hollow glass microspheres is 0.5~0.7 g / cm³. 3 ; and / or, The hollow glass microspheres contain at least 52% silica; and / or, The 7-day activity index of the hollow glass microspheres is greater than 80%; and / or, The 28-day activity index of the hollow glass microspheres is greater than 110%.

7. The ultra-high performance concrete admixture as described in claim 4, characterized in that, The shrinkage inhibitor includes a modified water-absorbing resin, and the preparation method of the modified water-absorbing resin includes the following steps: The water-absorbing resin was soaked in a calcium nitrate solution, shaken, and ball-milled to obtain the modified water-absorbing resin.

8. A method for preparing an ultra-high performance concrete admixture as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Mineral powder, silica, palladium, hollow glass microspheres, modified latex powder, modified calcium sulfate whiskers, synergist, viscosity reducer, and shrinkage inhibitor are homogenized to obtain an ultra-high performance concrete admixture.

9. A type of ultra-high performance concrete, characterized in that, It includes aggregates, and the ultra-high performance concrete admixture prepared by the preparation method of the ultra-high performance concrete admixture as described in any one of claims 1 to 7 or as described in claim 8; wherein the aggregates include at least one of coarse aggregates and fine aggregates.

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