CN109678380B - Ultrahigh-performance concrete rheological stabilizer - Google Patents
Ultrahigh-performance concrete rheological stabilizer Download PDFInfo
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- CN109678380B CN109678380B CN201910059202.6A CN201910059202A CN109678380B CN 109678380 B CN109678380 B CN 109678380B CN 201910059202 A CN201910059202 A CN 201910059202A CN 109678380 B CN109678380 B CN 109678380B
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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
- 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
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/60—Planning or developing urban green infrastructure
Abstract
The invention belongs to the technical field of advanced civil engineering materials, and particularly relates to an ultra-high performance concrete rheological stabilizer. After the gel material of the ultrahigh-performance concrete is replaced by equal mass, the anti-disturbance performance of the poured ultrahigh-performance concrete is improved on the basis of not obviously influencing the workability, strength and durability of the ultrahigh-performance concrete, so that the ultrahigh-performance concrete can be quickly poured on a structural part with a certain gradient, and the pouring quality and efficiency are improved.
Description
Technical Field
The invention belongs to the technical field of advanced civil engineering materials, and particularly relates to an ultrahigh-performance concrete rheological stabilizer.
Background
Ultra High Performance Concrete (UHPC) is a novel cement-based composite material with ultra high strength, ultra high toughness and high durability, and can be classified as a light high-strength material from the viewpoint of specific strength and specific stiffness. At present, the ultra-high performance concrete is mainly used for paving orthotropic steel bridge decks, the technology can effectively improve the rigidity of the steel bridge decks, and the two problems of fatigue cracking of steel structures of orthotropic steel bridge deck systems and frequent breakage of paving layers are hopefully solved. However, in the design process of the bridge, due to consideration of elevation design, drainage design, curve section ultrahigh design and the like, the bridge deck has a certain cross slope and a certain longitudinal slope, after the ultrahigh-performance concrete is poured, the ultrahigh-performance concrete flows to a lower position under the action of gravity, so that the thickness of the bridge deck ultrahigh-performance concrete layer is uneven, higher pressure is generated on a lateral formwork, particularly for ramp and other parts, the phenomenon that the ultrahigh-performance concrete flows is more remarkable if the ultrahigh-performance concrete is directly poured on a ramp surface due to large longitudinal slope, and the pouring quality of the ultrahigh-performance concrete is seriously influenced.
In order to solve the problem that the ultra-high performance concrete is easy to flow after being poured at a part with a certain gradient structure, Chengwei proposes that construction is carried out in a mode of reverse formwork in the 'construction technology for paving ultra-high performance concrete on a steel bridge deck', but the method has high requirements on the construction technology level, low construction efficiency and general practical application effect.
The cellulose ether, starch ether or rubber cement and other organic water-retention thickening materials are added into the cement-based mixture, so that the viscosity of the mixture can be obviously improved, the stability of the mixture can be further improved, but the substances have the problems that the mixing amount is difficult to control, the compatibility with other additives is poor and the like, and when the substances are added into the ultra-high performance concrete, the problem that the mixture with relatively high viscosity is easy to cause the rapid loss of the workability and the like can be further solved, and the continuous construction can not be further carried out.
Therefore, the ultrahigh-performance concrete rheological stabilizer is urgently needed to improve the disturbance resistance of the ultrahigh-performance concrete mixture, so that the ultrahigh-performance concrete can be quickly poured and constructed at a part with a certain gradient, and the pouring quality is ensured to be good.
Disclosure of Invention
The invention aims to provide an ultrahigh-performance concrete rheological stabilizer, which can be used for replacing a cementing material of ultrahigh-performance concrete in quality, and the like, and can improve the anti-disturbance performance of the ultrahigh-performance concrete after being poured on the basis of not obviously influencing the workability, strength and durability of the ultrahigh-performance concrete, so that the ultrahigh-performance concrete can be quickly poured on a structural part with a certain gradient, and the construction efficiency is improved.
In order to achieve the purpose, the technical scheme of the invention is as follows: the ultrahigh-performance concrete rheological stabilizer is characterized in that raw materials of the ultrahigh-performance concrete rheological stabilizer comprise bentonite, attapulgite, stearate, lithium salt and white carbon black, and the weight ratio of the raw materials is as follows:
in the invention, the bentonite is one of sodium bentonite or calcium bentonite, and the fineness of the bentonite is 250-300 meshes.
In the invention, the fineness of the attapulgite is 250-300 meshes.
In the invention, the stearate is one of sodium stearate or calcium stearate.
In the invention, the lithium salt is one of lithium nitrate or lithium sulfate.
In the invention, the particle size of the white carbon black is 20-30 nm, and SiO is contained in the white carbon black 2 The content is not less than 90%.
In the present invention, the fineness or the particle diameter refers to the fineness of the raw material or the particle diameter of the particles, that is, the fineness or the particle diameter before grinding.
The preparation method of the ultrahigh-performance concrete rheological stabilizer comprises the following preparation steps:
(1) grinding modification: adding bentonite, attapulgite and stearate into a ball mill according to a certain proportion for grinding modification, wherein the grinding time is 15-30 min;
(2) mixing: after the grinding modification process is finished, adding a certain amount of lithium salt and white carbon black into the ball mill, and then continuously grinding for 2-5 min to ensure that the raw materials are uniformly mixed.
In the invention, the main mineral components contained in the bentonite and the attapulgite have the characteristics of a layered structure, and the van der Waals force connection effect between unit cell layers is weak, so the bentonite and the attapulgite have good water absorption characteristics and are often used as inorganic water-retaining thickening materials.
According to the invention, the stearate has a hydrophobic characteristic, and the bentonite, the attapulgite and the stearate are weighed according to a certain proportion and then ground, so that a certain amount of stearate is attached to the surfaces of the bentonite and the attapulgite, and the water absorption rate of the bentonite and the attapulgite is adjusted. The grinding time is preferably 15-30 min, and the amount of stearate attached to the surfaces of the bentonite and the attapulgite is controlled according to the grinding time.
In the invention, the lithium salt is a common early strength agent in the cement-based materials, can obviously improve the hydration rate of the cement, accelerate the generation of hydration products, convert free water in the cement mixture into crystal water and quickly improve the viscosity of the cement mixture.
According to the invention, the white carbon black has large specific surface area and high activity, the viscosity of the mixture can be obviously improved when the white carbon black is added into the cement mixture, and the strength of hardened slurry can be improved by secondary hydration generated in the later period.
The invention provides an ultrahigh-performance concrete rheological stabilizer, which is prepared by replacing a cementing material in ultrahigh-performance concrete by equal mass, wherein bentonite and attapulgite in the ultrahigh-performance concrete rheological stabilizer are modified by stearate, so that free water in the ultrahigh-performance concrete mixture is gradually adsorbed, and the initial workability of the ultrahigh-performance concrete mixture is not obviously influenced. Meanwhile, the lithium salt can promote the early hydration of the ultra-high performance concrete mixture, the white carbon black in the invention can improve the early viscosity of the ultra-high performance concrete mixture due to the large specific surface area, and the two components have synergistic effect with the modified bentonite and the attapulgite, so that the early anti-disturbance performance of the ultra-high performance concrete mixture is improved. Finally, the white carbon black has high activity, and secondary hydration reaction occurs at the later stage, so that the adverse effect of bentonite and attapulgite on the strength development of the ultrahigh-performance concrete can be compensated.
The ultrahigh-performance concrete rheological stabilizer provided by the invention can effectively solve the problem that the ultrahigh-performance concrete mixture is easy to flow after being poured at a part with a certain gradient structure, and the proportion of the cementing material in the equal-quality alternative ultrahigh-performance concrete can be adjusted according to the gradient of the poured part.
Drawings
FIG. 1 is a diagram of an apparatus for evaluating the effects of examples 1 to 4. In the figure, 1 is horizontal ground, 2 is uncovered cuboid mould, and its inside size is: length, width, height, 500mm, 100mm, 3 is a spacer block, and 4 is an ultra high performance concrete mix.
Detailed Description
The invention provides an ultra-high performance concrete rheological stabilizer, which is further detailed in the following in order to make the purpose, preparation technology and implementation effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In example 1, a rheological stabilizer for ultra-high performance concrete is prepared by weighing raw materials including 100 parts by weight of sodium bentonite, 30 parts by weight of attapulgite, 5 parts by weight of calcium stearate, 5 parts by weight of lithium nitrate and 15 parts by weight of white carbon black, adding the sodium bentonite, the attapulgite and the calcium stearate into a ball mill for milling modification, after 15 minutes of milling, adding the lithium nitrate and the white carbon black into the ball mill, and continuing milling for 2 minutes, wherein the product is marked as W1.
Example 2, an ultra-high performance concrete rheological stabilizer is prepared by weighing raw materials, by weight, 100 parts of calcium bentonite, 40 parts of attapulgite, 8 parts of sodium stearate, 3 parts of lithium sulfate and 19 parts of white carbon black, adding the calcium bentonite, the attapulgite and the sodium stearate into a ball mill for grinding modification, adding the lithium sulfate and the white carbon black into the ball mill after grinding for 20min, and continuing grinding for 3min to obtain the product, which is recorded as W2.
Example 3, an ultra-high performance concrete rheological stabilizer is prepared by weighing raw materials including, by weight, sodium bentonite 100, attapulgite 45, sodium stearate 11, lithium sulfate 2, and white carbon black 22, adding the sodium bentonite, the attapulgite, and the sodium stearate to a ball mill for grinding modification, after grinding for 25min, adding lithium sulfate and white carbon black to the ball mill, and continuing grinding for 4min, wherein the product is denoted as W3.
Example 4, an ultra-high performance concrete rheological stabilizer is prepared by weighing raw materials, by weight, 100 parts of calcium bentonite, 50 parts of attapulgite, 15 parts of calcium stearate, 1 parts of lithium nitrate and 30 parts of white carbon black, adding the calcium bentonite, the attapulgite and the calcium stearate into a ball mill for grinding modification, adding the lithium nitrate and the white carbon black into the ball mill after grinding for 30min, and continuing grinding for 5min to obtain the product, which is recorded as W4.
The implementation effect is that the ultra-high performance concrete mixture is stirred according to the ultra-high performance concrete reference mixing ratio given in the table 1. Wherein the cement is Nanjing Xiaoye field P.II 52.5 grade cement, the mineral powder is Shanghai Baozan S95 grade mineral powder, and the silica fume has a specific surface area not less than 20000m 2 The high-quality silica fume is characterized in that the grain size of quartz sand is less than 1mm, the steel fiber is a long straight type with the diameter of 0.2mm and the length of 13mm, the water reducing agent is a powdery polycarboxylic acid water reducing agent, the defoaming agent is also powdery, and water is tap water.
FIG. 1 is a diagram of an apparatus for evaluating effects of examples 1 to 4. Placing the uncovered cuboid mold 2 on the horizontal ground 1, pouring the ultra-high performance concrete mixture 4 into the uncovered cuboid mold 2, enabling the ultra-high performance concrete mixture 4 to quickly realize self-leveling in the uncovered cuboid mold 2 under the action of gravity, and enabling the ultra-high performance concrete mixture 4 in the uncovered cuboid mold 2 to have the same thickness at each position. At the moment, a cushion block 3 is added at one end of a non-covered cuboid mold 2, a certain slope angle is formed between the non-covered cuboid mold 2 and a horizontal ground 1 and is recorded as a design slope angle alpha, the ultra-high performance concrete mixture 4 in the non-covered cuboid mold 2 flows downwards under the action of gravity and is stable and does not flow any more after half an hour, a certain slope is formed between the bottom surface of the non-covered cuboid mold 2 and the surface of the ultra-high performance concrete mixture 4 and is recorded as an actual measurement slope i, and the thicknesses of the ultra-high performance concrete mixture in the lifted end and the lower end of the non-covered cuboid mold 2 are respectively recorded as h 1 And h 2 And satisfies the following relation:
next, the four products obtained in examples 1 to 4 were evaluated for the effects thereof using the apparatus of fig. 1. The ultra-high performance concrete was prepared using the reference mix ratio of the ultra-high performance concrete given in table 1.
TABLE 1 ultra high Performance concrete base mix ratio (kg/m) 3 )
| Cement | Mineral powder | Silica fume | Quartz sand | Steel fiber | Water reducing agent | Defoaming agent | Water (I) |
| 680 | 210 | 160 | 1135 | 172 | 8.4 | 1.6 | 195 |
Note: the cement, the mineral powder and the silica fume are collectively called as cementing materials.
On the basis of the standard mixing proportion of the ultrahigh-performance concrete given in table 1, the four invention products obtained in examples 1 to 4 are used for replacing gelled materials in the ultrahigh-performance concrete according to different substitution rates and other qualities to mix experimental groups of ultrahigh-performance concrete mixtures, the obtained ultrahigh-performance concrete mixtures are poured into an evaluation device shown in fig. 1, and the actual gradient formed by the surfaces of the ultrahigh-performance concrete mixtures and the bottom surface of a mold under a certain designed slope angle is compared, so that the implementation effect of the invention is further known. Meanwhile, the expansion degree of the ultra-high performance concrete mixture and the 28d compressive strength of the ultra-high performance concrete cubic test piece are respectively measured according to the methods specified in the standard of the test method for the performance of the common concrete mixture GB/T50080-2016 and the standard of the test method for the mechanical property of the common concrete GB/T50081-2002. Specific results are shown in table 2.
TABLE 2 Effect of ultra-high Performance concrete rheology stabilizer under certain design slope angles
Note: (1) designing a slope angle alpha as arctan (0.08);
(2) the evaluation method of the implementation effect is as follows: and calculating the actual measurement gradient reduction degree of the test group ultrahigh-performance concrete mixture (T1-T4) by taking the actual measurement gradient of the reference ultrahigh-performance concrete mixture (group B) as a reference.
It should be noted that the application of the present invention is not limited to the above examples, and that modifications and changes can be made by those skilled in the art according to the above description, and all such modifications and changes are intended to fall within the scope of the appended claims.
Claims (5)
1. The ultrahigh-performance concrete rheological stabilizer is characterized in that the raw materials of the ultrahigh-performance concrete rheological stabilizer comprise bentonite, attapulgite, stearate, lithium salt and white carbon black, and the weight ratio of the raw materials is as follows:
bentonite 100
30-50 parts of attapulgite
Stearate 5-15
Lithium salt 1-5
15-30 parts of white carbon black;
the above-mentionedThe particle size of the white carbon black is 20-30 nm, and the white carbon black is SiO 2 The content is not lower than 90%;
the preparation method of the ultra-high performance concrete rheological stabilizer comprises the following steps:
(1) grinding modification: adding bentonite, attapulgite and stearate into a ball mill according to a certain proportion for grinding modification, wherein the grinding time is 15-30 min;
(2) mixing: after the grinding modification process is finished, adding a certain amount of lithium salt and white carbon black into the ball mill, and then continuously grinding for 2-5 min to ensure that the raw materials are uniformly mixed.
2. The ultra-high performance concrete rheological stabilizer according to claim 1, characterized in that the bentonite is one of sodium bentonite or calcium bentonite, and the fineness of the bentonite is 250-300 meshes.
3. The ultra-high performance concrete rheological stabilizer according to claim 1, characterized in that the fineness of the attapulgite is 250-300 meshes.
4. The ultra-high performance concrete rheology stabilizer according to claim 1, characterized in that the stearate is one of sodium stearate or calcium stearate.
5. The ultra-high performance concrete rheology stabilizer according to claim 1, characterized in that said lithium salt is one of lithium nitrate or lithium sulfate.
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