CN111848026A - Alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete and preparation method thereof - Google Patents
Alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/02—Selection of the hardening environment
- C04B40/024—Steam hardening, e.g. in an autoclave
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- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
- C04B2201/52—High compression strength concretes, i.e. with a compression strength higher than about 55 N/mm2, e.g. reactive powder concrete [RPC]
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Abstract
The invention discloses a preparation method of alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete, which is characterized by comprising the following steps of: the production raw material formula comprises the following components in parts by mass: 650-720 parts of portland cement, 95-130 parts of silica fume, 165-185 parts of mineral powder, 5-10 parts of nano silicon dioxide, 1050-1075 parts of quartz sand, 96-128 parts of straight steel fiber, 24-32 parts of twisted steel fiber, 13.725-15.54 parts of water glass with the modulus of 1.2-1.3, 13.75-18.13 parts of a water reducing agent and 154.7-202 parts of water. The advantages are that: the fluidity and early strength of the ultra-high performance concrete are obviously improved.
Description
Technical Field
The invention relates to the field of building materials, in particular to a concrete material and a preparation method thereof.
Background
Concrete is the most common building material in the modern application, however, common concrete has the defects of great weight, great brittleness, low strength and the like. The ultra-high performance concrete (UHPC) is a cement-based composite material with ultra-high compressive strength, high bending tensile strength and high toughness, and is based on a particle dense packing system (DSP) and a fiber reinforced composite system, so that the fineness and activity of components are improved, and internal defects of the material are reduced to the minimum, thereby obtaining the ultra-high strength and ultra-high durability.
Because the water consumption of the ultra-high performance concrete is extremely low and is far lower than that required by cement hydration, a large amount of unhydrated cement particles exist in the ultra-high performance concrete and are only used as a filling material of a system. In order to reduce resource waste caused by unhydrated cement particles, an admixture system with a large proportion needs to be introduced into a cementing material system, on one hand, the admixture reacts with calcium hydroxide generated by cement hydration to generate C-S-H gel, so that the negative influence of loose flaky calcium hydroxide on a microstructure is reduced, and the compactness of a matrix is improved. On the other hand, the consumption of the cement hydration product calcium hydroxide is beneficial to the improvement of the hydration degree of the cement. However, compared with cement, the strength of the common admixture can be formed only after the cement is hydrated and reacts with the hydration product calcium hydroxide of the cement, and the speed is slow, so that the early strength of the system can be reduced to a certain extent when a system is introduced with a higher content of the admixture system. However, many application scenarios of the ultra-high performance concrete, such as preparation of prefabricated parts, repair, reinforcement, and the like, require rapid formation of strength in an early stage, and it is difficult to well meet the requirements of the application scenarios due to the need of adopting a relatively large amount of admixture system.
Disclosure of Invention
In order to improve the early strength of the ultra-high performance concrete (UHPC), the invention provides the alkali-activated nano-reinforced early-strength ultra-high performance concrete and the preparation method thereof.
The technical scheme adopted by the invention is as follows: the preparation method of the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete comprises the following components in parts by mass: 650-720 parts of portland cement, 95-130 parts of silica fume, 165-185 parts of mineral powder, 5-10 parts of nano silicon dioxide, 1050-1075 parts of quartz sand, 96-128 parts of straight steel fiber, 24-32 parts of twisted steel fiber, 13.725-15.54 parts of water glass with the modulus of 1.2-1.3, 13.75-18.13 parts of a water reducing agent and 154.7-202 parts of water.
The invention adopts water glass with the modulus of 1.2-1.3 as an alkali activator to excite silica fume, superfine mineral powder and nano SiO in a gelling system2The pozzolanic activity of the equal-silicon-aluminum admixture is acceleratedThe hydration process is carried out while adding nano SiO2The microcrystalline nucleation effect is exerted, nucleation and crystallization points of hydration products are provided, the hydration reaction barrier is reduced, the hydration rate of cement is improved, and the early strength of the ultra-high performance concrete is improved under the combined action of the microcrystalline nucleation effect and the hydration reaction barrier.
Experiments show that compared with water glass with higher modulus, the water glass with 1.2-1.3 modulus has stronger alkali excitation property, and is beneficial to exciting silica fume, superfine mineral powder and nano SiO in a gelling system2When the silica-alumina admixture is used, the silica tetrahedron and the alumina tetrahedron are cracked, and partial silica bonds and alumina bonds are broken and are polymerized into the inorganic high polymer with the three-dimensional network structure again under the action of hydroxide ions, so that high strength is formed in a short time, and the early strength of the ultrahigh-performance concrete is improved. Meanwhile, the viscosity of the 1.2-1.3 modulus water glass is lower, and the influence on the fluidity of the ultra-high performance concrete is lower. In addition, the invention can play the role of alkali excitation and avoid the phenomenon of slurry fluidity loss caused by over-high doping amount by controlling the doping amount of the water glass.
In addition, steel fibers with the volume ratio of 1.5-2% are doped into the ultra-high performance concrete, 96-128 parts of straight steel fibers and 24-32 parts of twisted steel fibers are compounded in mass ratio, the straight steel fibers and the twisted steel fibers are in a linear shape, and can be well dispersed in the ultra-high performance concrete slurry with the volume ratio of 1.5-2%, so that the influence on the flow performance of the ultra-high performance concrete is low. The torsional steel fiber is doped, so that the high shear bonding strength and the obvious slip hardening characteristic of the torsional steel fiber can be exerted, and experiments show that the UHPC mechanical property and the deformability are well improved.
As a further improvement of the invention, the particle size of the nano silicon dioxide is 10-20 nm, the average particle size of the silica fume is 0.08-0.12 mu m, the particle size of the mineral powder is 2-10 mu m, and the average particle size of the portland cement is 16-19 mu m. According to the scheme, through forming the gelled material systems with different scale magnitudes and designing the mixing amount of each material, the particles with smaller particle sizes are embedded between larger particle gaps, so that a compact stacking structure is formed, the system strength is improved, the moisture among the particles is replaced, and the flowing property of slurry is improved.
More preferably, the particle size of the quartz sand is less than 1mm, and the quartz sand is graded according to the weight ratio of 20-40 meshes, 40-70 meshes, 70-140 meshes, 56: 25-27: 16-18. The scheme ensures that the fine aggregate is compactly accumulated, so that the prepared slurry has better flowing state and higher strength.
More preferably, the specific surface area of the portland cement is 410m2/kg, density 3150kg/m3And the 28d standard mortar test has the compression strength of 57.6MPa and the breaking strength of 8.9 MPa. According to the scheme, high-grade early-strength portland cement such as P.I52.5R portland cement is adopted, compared with ordinary portland cement, the portland cement in the scheme has the advantages that the proportion of cement minerals is higher, the hydration reaction process is faster, calcium hydroxide formed after hydration is beneficial to exciting the hydration activity of an active admixture, and the whole reaction process of the cementing material is accelerated. Meanwhile, the strength of hardened slurry formed after the mineral phase of the P.I52.5R portland cement is hydrated is higher, and the early strength of the ultrahigh-performance concrete can be improved through the comprehensive effect of the two aspects.
Preferably, the mineral powder is blast furnace slag micro powder, and the specific surface area is 800-1000 m2And/kg, the 7d activity index is more than 95 percent, and the 28d activity index is more than 105 percent. The scheme adopts the specific surface area of 800-1000 m2The superfine granulated blast furnace slag micro powder of/kg is used as admixture, and the main components of the admixture are CaO and SiO2、Al2O3MgO, etc. and contains high content of glass body, and has gelling property and volcanic ash activity. The higher fineness ensures that the superfine granulated blast furnace slag micro powder has higher activity and is beneficial to improving the early strength of the ultra-high performance concrete. Meanwhile, the mineral powder accounts for about 17-19% of the total weight of the cementing material, and can form tight packing with cement particles under the proportion, smaller superfine mineral powder particles (2-10 μm) are filled between the cement particles (16-19 μm) and silica fume particles (0.08-0.12 μm) to form a more compact packing structure, and react with calcium hydroxide and an alkali activator in a matrix, so that the improvement of the microstructure and the improvement of the strength of UHPC are facilitated.
More preferably, SiO of the silica fume2The mass percentage content is more than 95 percent, the volcanic ash activity index is more than 110 percent, and the specific surface area is more than 20000m2Per kg, density 2200kg/m3. The silica fume adopted by the scheme can be better filled in gaps among cement and mineral powder particles and between a cement matrix and an interface transition area of steel fibers, so that the compactness of the matrix and the interface is further improved, and the silica fume reacts with calcium hydroxide and an alkali activator generated by cement hydration to generate hydrated gel which is filled between the matrix and the interface transition area gaps, so that the material strength is improved. The silica fume consumption of the prepared ultra-high performance concrete accounts for about 10-15% of the whole cementing material system, so that the prepared raw materials are enabled to form the closest packing, the silica fume is filled between cement and mineral powder particles, and part of water among the particles is replaced, so that the fluidity of the prepared ultra-high performance concrete is improved. Meanwhile, the phenomenon that slurry is dry and difficult to flow due to the fact that the mixing amount of the silica fume is too high and the moisture needed by particles is too much is avoided.
More preferably, the SiO of the nano-silica2The mass percentage content is more than 99 percent. Nano SiO2The cement hydrate has extremely fine particle size, and can provide nucleation crystallization points of cement hydrate C-S-H gel in the cement hydration process, thereby reducing the hydration reaction barrier, improving the cement hydration rate and promoting the early strength of the ultra-high performance concrete. Nano SiO2The dosage of the nano SiO is 0.5-1% of the weight fraction of the cementing material system, which can ensure that the nano SiO2Improving the early strength of the ultra-high performance concrete and reducing the nano SiO2The slurry viscosity is increased and the fluidity is decreased by the incorporation of (2).
As a further improvement of the invention, the length of the straight steel fiber is 12-14 mm, the diameter is 0.18-0.23 mm, and the tensile strength is 2850-3050 Mpa; the length of the torsional steel fiber is 28-32 mm, the diameter is 0.28-0.32 mm, and the tensile strength is more than 2500 MPa.
As a further improvement of the invention, the water reducing agent is a high-dispersion polycarboxylic acid water reducing agent, and the water reducing rate is more than 35%.
As a further improvement of the invention, the preparation method of the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete specifically comprises the following production steps:
S1, weighing the raw materials according to the formula of the production raw materials;
s2, adding portland cement, silica fume, quartz sand, mineral powder, nano silicon dioxide and a water reducing agent into a stirrer, and stirring to uniformly mix the materials;
s3: taking the water, adding the water into a stirrer, and stirring until the materials form uniform slurry with a flow state;
s4: adding straight steel fibers and twisted steel fibers into the stirrer, and continuing stirring after the addition is finished so as to uniformly disperse the steel fibers in the slurry;
s5: adding the weighed water glass with the modulus of 1.2-1.3 into a stirrer, continuously stirring until the water glass is uniformly mixed, and pouring the ultrahigh-performance concrete into a mould after stirring;
s6, placing the ultra-high performance concrete and the mould in a curing room with the temperature of 18-22 ℃ and the relative humidity of more than 95% for curing for more than 24h, demoulding, and placing the ultra-high performance concrete test block in a steam curing box for curing, wherein the steam curing temperature is set to be 70-80 ℃, and the curing time is set to be more than 48 h.
According to the scheme, a method of firstly mixing the mixture slurry and then doping the alkali activator is adopted, and experiments show that the excitation effect of the alkali activator can be fully exerted, and the influence of the reduction of the slurry flow property caused by the reaction of the alkali activator and a cementing material is reduced.
More preferably, the straight steel fibers and the twisted steel fibers are added in the step S4 in the following manner: and adding the straight steel fibers and the twisted steel fibers at a constant speed while stirring, and controlling the adding speed to ensure that the adding time lasts for 50-70 s. The scheme can avoid the phenomenon of fiber aggregation and agglomeration caused by adding too many steel fibers simultaneously, thereby improving the flow property of the ultra-high performance concrete.
More preferably, the water glass with a modulus of 1.2-1.3 in step S5 is added in the following manner: the addition was completed within 10s and the stirring time after the addition was completed was not more than 1.5 min. According to the scheme, the alkali activator is rapidly added, and the stirring time after the alkali activator is added is controlled, so that the phenomenon of slurry fluidity reduction caused by the reaction of the alkali activator with silica fume, ground mineral powder, nano silicon dioxide and the like is reduced.
The invention also discloses alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete which is prepared by the preparation method of the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete.
The invention has the beneficial effects that:
1) the invention adopts water glass with the modulus of 1.2-1.3 as an alkali activator to excite silica fume, superfine mineral powder and nano SiO in a gelling system 2The volcanic ash activity of the silicon-aluminum admixture is equal, the hydration process is accelerated, and simultaneously, the nano SiO is added2The microcrystalline nucleation effect is exerted, nucleation and crystallization points of hydration products are provided, the hydration reaction barrier is reduced, the hydration rate of cement is improved, and the early strength of the ultra-high performance concrete is improved under the combined action of the microcrystalline nucleation effect and the hydration reaction barrier.
2) The steel fiber with the volume ratio of 1.5-2% is doped into the ultra-high performance concrete, 96-128 parts of straight steel fiber and 24-32 parts of twisted steel fiber are compounded, the straight steel fiber and the twisted steel fiber are in a linear shape, and can be well dispersed in the ultra-high performance concrete slurry with the volume ratio of 1.5-2%, and the influence on the flow property of the ultra-high performance concrete is low. The torsional steel fiber is doped, so that the high shear bonding strength and the obvious slip hardening characteristic of the torsional steel fiber can be exerted, and the mechanical property and the deformability of the UHPC are well improved.
3) By forming a cementing material system with different scale magnitudes (the particle size of nano silicon dioxide is 10-20 nm, the average particle size of silica fume is 0.08-0.12 mu m, the particle size of mineral powder is 2-10 mu m, and the average particle size of portland cement is 16-19 mu m), and designing the mixing amount of each material, particles with smaller particle sizes are embedded between larger particle sizes, so that a compact stacking structure is formed, the system strength is improved, moisture among the particles is replaced, and the flow property of slurry is improved.
4) The method of mixing the mixture slurry and then doping the alkali activator is adopted, so that the excitation effect of the alkali activator can be fully exerted, and the influence of the reduction of the slurry flow property caused by the reaction of the alkali activator and the cementing material is reduced.
Detailed Description
The present invention will be further described with reference to the following examples.
The first embodiment is as follows:
the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete is produced by the following method:
s1, weighing the raw materials according to the formula of the production raw materials;
665kg of Portland cement, 124kg of silica fume, 184kg of mineral powder, 6kg of nano silicon dioxide, 1071kg of quartz sand (20-40 meshes of 599.76 kg; 40-70 meshes of 282.74 kg; 70-140 meshes of 188.90kg) with the grain size of less than 1mm, 128kg of copper-plated micro-wire straight steel fiber, 32kg of twisted steel fiber, 14.685kg of water glass with the modulus of 1.3, 17.13kg of high-dispersion polycarboxylic acid solid water reducing agent with the water reducing rate of 40 percent and 176.22kg of tap water;
the particle size of the nano silicon dioxide is 19.6nm, the average particle size of the silica fume is 0.08 mu m, the particle size of the mineral powder is 7.3 mu m, and the average particle size of the portland cement is 17.7 mu m;
the Portland cement is P.I 52.5R Portland cement, and the specific surface area is 410m2/kg, density 3150kg/m3The 28d standard mortar test has the compression strength of 57.6MPa and the breaking strength of 8.9 MPa;
The mineral powder is blast furnace slag micro powder with a specific surface area of 856m2Kg, 7d activity index 96%, 28d activity index 109%;
SiO of the silica fume296 percent of mass percent, 112 percent of volcanic ash activity index and 26200m of specific surface area2Per kg, density 2200kg/m3；
SiO of the nano silicon dioxide2The mass percentage content is 99.4 percent. The length of the straight steel fiber is 14mm, the diameter is 0.2mm, and the tensile strength is 3000 Mpa; the length of the torsional steel fiber is 30mm, the diameter is 0.3mm, and the tensile strength is 3000 MPa.
S2, adding portland cement, silica fume, quartz sand, mineral powder, nano silicon dioxide and a water reducing agent into a stirrer, and stirring for 2min to uniformly mix the materials;
s3: taking the measured water, adding into a stirrer, and stirring for 5min to form uniform slurry with flow state;
s4: and adding the straight steel fibers and the twisted steel fibers in a stirrer at a constant speed while stirring, wherein the adding time lasts for 62 s. After the addition is finished, stirring is continued for 2min, so that the steel fibers are uniformly dispersed in the slurry;
s5: adding the weighed water glass with the modulus of 1.3 into a stirrer quickly, wherein the adding time lasts only 8s, stirring is continued for 1min after adding, the stirring is stopped immediately, and the ultrahigh-performance concrete is poured into a mold after stirring;
And S6, placing the ultra-high performance concrete and the mould in a standard curing room with the temperature of 20 ℃ and the relative humidity of 97 percent for curing for 24 hours, demoulding, and placing the ultra-high performance concrete test block in a steam curing box for curing, wherein the steam curing temperature is set to be 80 ℃ and the curing time is set to be 48 hours.
S7, detecting the fluidity, the compression strength and the breaking strength of the obtained ultra-high performance concrete, and the results are shown in Table 1.
Example two:
the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete is produced by the following method:
s1, weighing the raw materials according to the formula of the production raw materials;
719.2kg of Portland cement, 111.4kg of silica fume, 182.3kg of mineral powder, 7kg of nano silicon dioxide, 1071kg of quartz sand (20-40 meshes 599.76 kg; 40-70 meshes 282.74 kg; 70-140 meshes 188.90kg) with the grain size smaller than 1mm, 112kg of copper-plated micro-wire straight steel fiber, 28kg of twisted steel fiber, 15.20kg of water glass with the modulus of 1.2, 17.85kg of high-dispersion polycarboxylic acid solid water reducer with the water reducing rate of 40% and 183.58kg of tap water;
the particle size of the nano silicon dioxide is 19.6nm, the average particle size of the silica fume is 0.08 mu m, the particle size of the mineral powder is 7.3 mu m, and the average particle size of the portland cement is 17.7 mu m;
the Portland cement is P.I 52.5R Portland cement, and the specific surface area is 410m 2/kg, density 3150kg/m3The 28d standard mortar test has the compression strength of 57.6MPa and the fracture resistanceThe strength is 8.9 Mpa;
the mineral powder is blast furnace slag micro powder with a specific surface area of 856m2Kg, 7d activity index 96%, 28d activity index 109%;
SiO of the silica fume296 percent of mass percent, 112 percent of volcanic ash activity index and 26200m of specific surface area2Per kg, density 2200kg/m3；
SiO of the nano silicon dioxide2The mass percentage content is 99.4 percent. The length of the straight steel fiber is 14mm, the diameter is 0.2mm, and the tensile strength is 3000 Mpa; the length of the torsional steel fiber is 30mm, the diameter is 0.3mm, and the tensile strength is 3000 MPa.
S2, adding portland cement, silica fume, quartz sand, mineral powder, nano silicon dioxide and a water reducing agent into a stirrer, and stirring for 2min to uniformly mix the materials;
s3: taking the measured water, adding into a stirrer, and stirring for 5min to form uniform slurry with flow state;
s4: and adding the straight steel fibers and the twisted steel fibers in a stirrer at a constant speed while stirring, wherein the adding time lasts 65 s. After the addition is finished, stirring is continued for 2min, so that the steel fibers are uniformly dispersed in the slurry;
s5: adding the weighed water glass with the modulus of 1.2 into a stirrer quickly, wherein the adding time lasts only 9s, continuously stirring for 1.5min after adding, stopping stirring immediately, and pouring the ultrahigh-performance concrete into a mould after stirring;
And S6, placing the ultra-high performance concrete and the mould in a standard curing room with the temperature of 20 ℃ and the relative humidity of 97 percent for curing for 24 hours, demoulding, and placing the ultra-high performance concrete test block in a steam curing box for curing, wherein the steam curing temperature is set to be 80 ℃ and the curing time is set to be 48 hours.
S7, detecting the fluidity, the compression strength and the breaking strength of the obtained ultra-high performance concrete, and the results are shown in Table 1.
Example three:
the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete is produced by the following method:
s1, weighing the raw materials according to the formula of the production raw materials;
660kg of Portland cement, 105kg of silica fume, 204kg of mineral powder, 5kg of nano silicon dioxide, 1074kg of quartz sand (20-40 meshes of 601.44 kg; 40-70 meshes of 283.53 kg; 70-140 meshes of 188.90kg) with the grain size of less than 1mm, 128kg of copper-plated micro-wire straight steel fiber, 32kg of twisted steel fiber, 14.685kg of water glass with the modulus of 1.3, 17.13kg of high-dispersion polycarboxylic acid solid water reducing agent with the water reducing rate of 40 percent and 180.19kg of tap water;
the particle size of the nano silicon dioxide is 19.6nm, the average particle size of the silica fume is 0.08 mu m, the particle size of the mineral powder is 7.3 mu m, and the average particle size of the portland cement is 17.7 mu m;
the Portland cement is P.I 52.5R Portland cement, and the specific surface area is 410m 2/kg, density 3150kg/m3The 28d standard mortar test has the compression strength of 57.6MPa and the breaking strength of 8.9 MPa;
the mineral powder is blast furnace slag micro powder with a specific surface area of 856m2Kg, 7d activity index 96%, 28d activity index 109%;
SiO of the silica fume296 percent of mass percent, 112 percent of volcanic ash activity index and 26200m of specific surface area2Per kg, density 2200kg/m3；
SiO of the nano silicon dioxide2The mass percentage content is 99.4 percent. The length of the straight steel fiber is 14mm, the diameter is 0.2mm, and the tensile strength is 3000 Mpa; the length of the torsional steel fiber is 30mm, the diameter is 0.3mm, and the tensile strength is 3000 MPa.
S2, adding portland cement, silica fume, quartz sand, mineral powder, nano silicon dioxide and a water reducing agent into a stirrer, and stirring for 2min to uniformly mix the materials;
s3: taking the measured water, adding into a stirrer, and stirring for 5min to form uniform slurry with flow state;
s4: and adding the straight steel fibers and the twisted steel fibers in a stirrer at a constant speed while stirring, wherein the adding time lasts for 60 s. After the addition is finished, stirring is continued for 2min, so that the steel fibers are uniformly dispersed in the slurry;
s5: adding the weighed water glass with the modulus of 1.3 into a stirrer quickly, wherein the adding time lasts only 10s, continuously stirring for 1.2min after adding, stopping stirring immediately, and pouring the ultrahigh-performance concrete into a mould after stirring;
And S6, placing the ultra-high performance concrete and the mould in a standard curing room with the temperature of 20 ℃ and the relative humidity of 97 percent for curing for 24 hours, demoulding, and placing the ultra-high performance concrete test block in a steam curing box for curing, wherein the steam curing temperature is set to be 80 ℃ and the curing time is set to be 48 hours.
S7, detecting the fluidity, the compression strength and the breaking strength of the obtained ultra-high performance concrete, and the results are shown in Table 1.
Comparative example one:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: the amount of water glass added was 30 kg.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example two:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: no twisted steel fiber was added, and 160kg of copper-plated micro-wire straight steel fiber was added.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example three:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: the quartz sand composition is as follows: 200kg of 20-40 meshes; 371kg of 40-70 meshes; 70-140 mesh 600 kg.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example four:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: no nano-silica is incorporated.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example five:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: the modulus of water glass is 2.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example six:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: the water glass adding process of the original S5 step is advanced to S3, and is added together with water, namely step S3 is as follows: adding water glass and water, and stirring for 7 min. Step S5 is: and adding the straight steel fibers and the twisted steel fibers in a stirrer at a constant speed while stirring, wherein the adding time lasts for 62 s. And after the addition is finished, stirring for 2min continuously to uniformly disperse the steel fibers in the slurry, and pouring the ultrahigh-performance concrete into a mold after the stirring is finished.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example seven:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: step S4 is: and adding the straight steel fibers and the twisted steel fibers in a stirrer at a constant speed while stirring, wherein the adding time lasts for 10 s. After the addition was complete, stirring was continued for 2 min.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
Comparative example eight:
this comparative example is a control experiment of example one, designed under the same conditions as example one, except that: step S5 is: and (3) quickly adding the weighed water glass with the modulus of 1.3 into the stirrer, wherein the adding time lasts for only 8s, and continuously stirring for 3min after adding.
The fluidity, compression strength and flexural strength of the obtained ultra-high performance concrete are detected, and the results are shown in table 1.
The detection method comprises the following steps:
1. slump expansion degree detection method
The ultra-high performance concrete mixture is prepared according to the proportioning and preparation method of the invention, the mixture is filled into a slump cone until the slump cone is full, and the surplus concrete mixture is scraped off and trowelled for leveling. And vertically and stably lifting the slump cone to the ground, measuring the final maximum diameter and the minimum diameter of the expanded ultrahigh-performance concrete by using a steel ruler, and taking the arithmetic average value as the slump expansion average value.
2. Compression strength and rupture strength detection method
The ultra-high performance concrete is filled into a test mould with the thickness of 40mm multiplied by 160mm, and a test piece is formed through a vibration table. Placing the sample with the mold in a curing room with the temperature of 20 +/-2 ℃ and the relative humidity of 95 +/-5% for 24 hours, then removing the mold, placing the ultrahigh-performance concrete and the mold in a standard curing room with the relative humidity of more than 95% for curing for 24 hours, then demolding, placing the ultrahigh-performance concrete sample in a steam curing box for curing, setting the steam curing temperature to be 70-80 ℃, and curing for 48 hours. The compressive strength and the flexural strength were tested. The compression rate for the flexural strength test was (50. + -.10) N/s, and the final test results were averaged over three test blocks. The pressing rate when the compressive strength was measured was (2400. + -. 200) N/s. The final experimental results were averaged over six blocks.
TABLE 1 test results of fluidity, compression strength and flexural strength of ultra-high performance concrete
As can be seen from Table 1, the slump expansion of the ultra-high performance concrete materials prepared in the first to third examples is greater than 650mm, and the flow performance is good. Tests on the compressive strength and the flexural strength of 7d and 28d show that the 28d compressive strength is greater than 200MPa, the flexural strength is greater than 29MPa, the 7d compressive strength of the prepared ultra-high performance concrete reaches more than 80% of 28d, the 7d flexural strength reaches more than 90% of 28d, and the concrete has excellent early strength performance.
As can be seen from the first example and the first comparative example, at a higher dosage of the alkali activator, the alkali activator and the cementing material have a certain reaction, so that the slump expansion is reduced from 665mm to 545mm, and the flow property is obviously reduced.
As can be seen from the first example and the second comparative example, when the fiber doping mode is changed and only the straight copper-plated steel fiber is doped, the bonding strength and the slippage steric hindrance effect of the torsion fiber cannot be exerted, and the flexural strength of the torsion fiber is reduced by 13.8 percent to 27.3MPa from 31.7MPa, which proves that the flexural strength of the material can be effectively improved by adding the torsion steel fiber.
As can be seen from the first and third examples, when no stage setting is performed, the stacking state of the quartz sand is not reasonable, the slump expansion degree is reduced from 665mm to 620mm, the compressive strength and the flexural strength are also slightly reduced, and the overall performance is reduced compared with the design formula of the invention.
As can be seen from the first and fourth examples, when nano SiO is not doped2In time, nano SiO is lacked2The integral strength performance is reduced due to the microcrystal nucleation effect and high pozzolanic activity, the 7d compressive strength is reduced from 175.3MPa to 158.2MPa, and the early strength is obviously reduced.
As can be seen from the first embodiment and the fifth embodiment, the water glass with the modulus of 1.2-1.3 is adopted as the alkali activator, so that the early strength of the ultrahigh-performance concrete can be activated.
As can be seen from the first example and the sixth comparative example, the flowability of the material can be significantly improved by mixing the slurry of the mixture and then adding the alkali activator.
As can be seen from the first embodiment and the seventh comparative example, the polymorphic steel fibers can be effectively dispersed by prolonging the feeding time of the steel fibers to 50-70 s, so that agglomeration is avoided, and the fluidity and the strength of the mixture are improved.
As can be seen from the first embodiment and the eighth comparative example, when the water glass is rapidly added into the stirrer, the fluidity of the slurry can be ensured and the fluidity loss can be reduced by shortening the stirring time within 1.5min after the water glass is added.
Claims (13)
1. The preparation method of the alkali-activated nano-reinforced early-strength type ultrahigh-performance concrete is characterized by comprising the following steps of: the production raw material formula comprises the following components in parts by mass: 650-720 parts of portland cement, 95-130 parts of silica fume, 165-185 parts of mineral powder, 5-10 parts of nano silicon dioxide, 1050-1075 parts of quartz sand, 96-128 parts of straight steel fiber, 24-32 parts of twisted steel fiber, 13.725-15.54 parts of water glass with the modulus of 1.2-1.3, 13.75-18.13 parts of a water reducing agent and 154.7-202 parts of water.
2. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 1, wherein: the particle size of the nano silicon dioxide is 10-20 nm, the average particle size of the silica fume is 0.08-0.12 mu m, the particle size of the mineral powder is 2-10 mu m, and the average particle size of the portland cement is 16-19 mu m.
3. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 2, wherein: the particle size of the quartz sand is less than 1mm, and the quartz sand is graded according to the weight ratio of (56: 25-27: 16-18) between 20-40 meshes, 40-70 meshes, 70-140 meshes.
4. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 2, wherein: the specific surface area of the portland cement is 410m2/kg, density 3150kg/m3And the 28d standard mortar test has the compression strength of 57.6MPa and the breaking strength of 8.9 MPa.
5. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 2, wherein: the mineral powder is blast furnace slag micro powder, and the specific surface area of the mineral powder is 800-1000 m2And/kg, the 7d activity index is more than 95 percent, and the 28d activity index is more than 105 percent.
6. Preparation of alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 2The method is characterized in that: SiO of the silica fume2The mass percentage content is more than 95 percent, the volcanic ash activity index is more than 110 percent, and the specific surface area is more than 20000m2Per kg, density 2200kg/m 3。
7. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 2, wherein: SiO of the nano silicon dioxide2The mass percentage content is more than 99 percent.
8. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 1, wherein: the length of the straight steel fiber is 12-14 mm, the diameter of the straight steel fiber is 0.18-0.23 mm, and the tensile strength of the straight steel fiber is 2850-3050 Mpa; the length of the torsional steel fiber is 28-32 mm, the diameter is 0.28-0.32 mm, and the tensile strength is more than 2500 MPa.
9. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete according to claim 1, wherein: the water reducing agent is a high-dispersion polycarboxylic acid water reducing agent, and the water reducing rate is more than 35%.
10. The method for preparing alkali-activated nano-reinforced early-strength ultra-high performance concrete according to any one of claims 1 to 9, wherein the method comprises the following steps: comprises the following production steps:
s1, weighing the raw materials according to the formula of the production raw materials;
s2, adding portland cement, silica fume, quartz sand, mineral powder, nano silicon dioxide and a water reducing agent into a stirrer, and stirring to uniformly mix the materials;
S3: taking the water, adding the water into a stirrer, and stirring until the materials form uniform slurry with a flow state;
s4: adding straight steel fibers and twisted steel fibers into the stirrer, and continuing stirring after the addition is finished so as to uniformly disperse the steel fibers in the slurry;
s5: adding the weighed water glass with the modulus of 1.2-1.3 into a stirrer, continuously stirring until the water glass is uniformly mixed, and pouring the ultrahigh-performance concrete into a mould after stirring;
s6, placing the ultra-high performance concrete and the mould in a curing room with the temperature of 18-22 ℃ and the relative humidity of more than 95% for curing for more than 24h, demoulding, and placing the ultra-high performance concrete test block in a steam curing box for curing, wherein the steam curing temperature is set to be 70-80 ℃, and the curing time is set to be more than 48 h.
11. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete of claim 10, wherein: the straight steel fibers and the twisted steel fibers in the step S4 are added in the following manner: and adding the straight steel fibers and the twisted steel fibers at a constant speed while stirring, and controlling the adding speed to ensure that the adding time lasts for 50-70 s.
12. The method of preparing alkali-activated, nano-reinforced, early-strength, ultra-high performance concrete of claim 10, wherein: the adding mode of the water glass with the modulus of 1.2-1.3 in the step S5 is as follows: the addition was completed within 10s and the stirring time after the addition was completed was not more than 1.5 min.
13. The alkali-activated nano-reinforced early strength ultra-high performance concrete prepared by the method for preparing the alkali-activated nano-reinforced early strength ultra-high performance concrete according to any one of claims 1 to 12.
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