High-lift pump concrete and preparation method thereof

Abstract

The invention discloses high-lift pump concrete and a preparation method thereof, and belongs to the technical field of building materials. The high-lift pump concrete is prepared from the following raw materials in parts by mass: 400 to 500 parts of cement, 150 to 200 parts of fly ash, 60 to 100 parts of mineral powder, 700 to 750 parts of coarse aggregate, 300 to 400 parts of fine aggregate, 50 to 90 parts of fiber, 1 to 5 parts of retarder, 20 to 25 parts of water reducing agent and 120 to 170 parts of water, the water reducing agent comprises a polycarboxylic acid water reducing agent and sodium lignin sulfonate. According to the designed preparation scheme of the high-lift pumped concrete, the pumping pressure of the concrete can be reduced, the construction performance can be improved, the pipeline blockage phenomenon can be avoided, the later strength development can be promoted, and the high-lift pumped concrete is not prone to drying shrinkage and excellent in comprehensive performance. The concrete raw materials limited by the invention have no compatibility problem, and have good stability.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to high-lift pumping concrete and a preparation method thereof. Background Art

[0002] Concrete has the advantages of high strength, wide source of raw materials, easy preparation, low cost, and wide range of applications. It is the preferred building material in the construction industry. In recent years, with the continuous development of construction technology, higher requirements have been placed on the working performance of concrete. Pumped concrete refers to a type of concrete that can be transported through pipelines. Compared with conventional concrete, it has better fluidity and can continuously and quickly complete the transportation and pouring of concrete, greatly improving construction efficiency. In order to cope with construction scenarios such as high-rise buildings, large bridges, tunnel projects, and water conservancy projects that require long-distance and high-lift transportation of concrete, the formula of pumped concrete still needs to be further improved to improve the pumpability of pumped concrete.

[0003] During the preparation process of pumped concrete, it is usually necessary to add a variety of admixtures to make the water retention, fluidity, and workability of the concrete meet the performance requirements, so as to prevent water seepage, segregation, pumping pipeline blockage and other phenomena, and avoid adverse effects on the pouring effect of concrete. In order to improve the pumpability of concrete, reducing the viscosity of concrete is one of the improvement directions. Although increasing the amount of water can reduce the viscosity of concrete, it will aggravate the shrinkage and swelling phenomenon, increase the deformability of concrete, and also cause the strength to decrease, affecting the quality of the project. Selecting the appropriate type and amount of mineral admixtures can make the concrete have better fluidity and improve the strength of concrete; however, the effect of mineral admixtures on the improvement of the pumpability of concrete is also limited. When the admixture dosage is high, the concrete slump will be too large, resulting in uneven strength of the concrete and more prone to cracks. The size of the concrete slump directly affects the pumping performance. Generally, its pumping resistance decreases with the increase of slump. When the slump is small, the pumping pressure will increase, which is easy to damage the pipeline; when the slump is too large, segregation problems are prone to occur, causing pipe blockage. Therefore, in order to meet the high-lift transportation requirements of pumped concrete, its preparation scheme still needs to be further improved. Summary of the invention

[0004] The object of the present invention is to provide a high-lift pumped concrete and a preparation method thereof to solve the above-mentioned problems in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a high-lift pumping concrete, wherein the raw materials are calculated by weight and include:

[0007] 400-500 parts of cement, 150-200 parts of fly ash, 60-100 parts of mineral powder, 700-750 parts of coarse aggregate, 300-400 parts of fine aggregate, 50-90 parts of fiber, 1-5 parts of retarder, 20-25 parts of water reducer and 120-170 parts of water;

[0008] The water reducer comprises a polycarboxylate water reducer and sodium lignin sulfonate.

[0009] Preferably, the mass ratio of the polycarboxylate water reducer to sodium lignin sulfonate is 1:3.5-5.

[0010] Preferably, the average particle size of the fly ash is less than 5 μm.

[0011] Preferably, the coarse aggregate is ceramsite and / or pebbles, and the average particle size is 5-20 mm.

[0012] Preferably, the fine aggregate is one or more of mineral powder, river sand and machine-made sand, and has an average particle size of 0.16-5 mm.

[0013] Preferably, the fibers are steel fibers; the average length of the fibers is 5-20 mm, and the average diameter is 0.1-0.3 mm.

[0014] Preferably, the retarder is sodium gluconate.

[0015] Preferably, the high-lift pumped concrete is composed of the following raw materials in parts by mass:

[0016] 470 parts of cement, 180 parts of fly ash, 90 parts of mineral powder, 720 parts of coarse aggregate, 380 parts of fine aggregate, 75 parts of fiber, 4.5 parts of retarder, 25 parts of water reducer and 140 parts of water.

[0017] The second technical solution of the present invention is to provide a method for preparing the above-mentioned high-lift pumped concrete, comprising the following steps:

[0018] The mineral powder, coarse aggregate, fine aggregate, fiber and water are mixed to obtain a mixture;

[0019] Cement, fly ash, retarder and water reducing agent are added to the mixture to obtain the high-lift pumping concrete.

[0020] The technical principles of the present invention are as follows:

[0021] The polycarboxylate water-reducing agent added in the present invention is very helpful in reducing the time-dependent loss of concrete slump, and can play a water-reducing effect in concrete for a long time, and improve the density and strength of concrete; however, when only the polycarboxylate water-reducing agent is used as the water-reducing agent of the present invention, the amount of the water-reducing agent must be greatly increased to meet the water-reducing effect, and the amount of the polycarboxylate water-reducing agent needs to be strictly controlled, otherwise it is easy to cause the "inverted" phenomenon in the later stage. Sodium lignin sulfonate can improve the fluidity and plasticity of concrete, and can better improve the compressive strength compared with other types of water-reducing agents, and it also has micro-air entrainment, which can introduce a certain amount of tiny bubbles into the mixture, improve the fluidity of concrete, and reduce pumping resistance, but its water reduction rate is relatively low, and the slump loss is large. The present invention, by mixing polycarboxylate water-reducing agent and sodium lignin sulfonate, can effectively improve the fluidity of concrete while avoiding the problem of difficult control of slump caused by excessive amount of polycarboxylate water-reducing agent, and plays a synergistic role, which provides help for meeting the pump performance requirements of the present invention.

[0022] In order to make the concrete have a certain fluidity, maintain the corresponding pumpability and cohesiveness, and strengthen the strength of the concrete to a certain extent, it is necessary to reasonably select the particle size and proportion of the aggregate. The present invention can improve the fluidity and uniformity of concrete and reduce the viscosity of concrete by increasing the proportion of coarse aggregate in the raw materials, which helps to reduce the energy loss of concrete during the pumping process, thereby further improving the pumping effect of the admixture. At the same time, it is also necessary to ensure that the amount of fine aggregate added in the raw materials is not too low, otherwise it will be difficult to play a lubricating and wrapping role, resulting in increased pumping resistance, and even segregation and water seepage. After limiting the raw material parameters to the level of the present invention, it can be ensured that the mixed aggregates are more densely stacked and have a smaller porosity.

[0023] The randomly distributed fiber components in the concrete matrix can provide certain support for the slurry and aggregates, prevent the aggregates from settling to the bottom in the admixture, prevent the formation of upper and lower layered structures, and improve the homogeneity of the structure.

[0024] The mineral powder added in the present invention is very helpful for improving the water retention, fluidity and workability of concrete. However, the amount of mineral powder added should not be too high, otherwise the concrete will become too viscous, resulting in uneven stress distribution inside the concrete, which is more likely to cause cracks on the concrete surface during the hardening process.

[0025] The beneficial technical effects of the present invention are as follows:

[0026] The high-lift pumping concrete preparation scheme designed by the present invention can reduce the pumping pressure of concrete, improve the construction performance, avoid pipeline blockage, and help promote the later strength development, is not easy to dry and shrink, and has excellent comprehensive performance. There is no compatibility problem between the concrete raw materials defined by the present invention, and it has good stability. DETAILED DESCRIPTION

[0027] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0028] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0031] The preparation method of the polycarboxylate water-reducing agent used in the following embodiments and comparative examples of the present invention is:

[0032] (1) 10 wt% polyoxyethylene ether and a small amount of deionized water were mixed in a three-necked flask and placed in a water bath. The mixture was stirred and pre-dissolved at 30° C. for later use;

[0033] (2) 0.35 wt% initiator ammonium persulfate, 32 wt% acrylic acid and deionized water are mixed to prepare material A; 0.18 wt% chain transfer agent 3-thioglycolic acid and deionized water are mixed to prepare material B; 1.8 wt% monomer γ-methacryloxypropyltrimethoxysilane (KH570) is prepared as material C for later use;

[0034] (3) After the polyoxyethylene ether mixture is completely dissolved, it is placed in a reaction kettle, and material A, material B, and material C are added dropwise at a uniform speed using a peristaltic pump. Material A is added dropwise for 3 hours, material B is added dropwise for 3.5 hours, and material C is added dropwise for 3 hours. After the addition of materials A, B, and C is completed, the mixture is kept at 40° C. for 1 hour;

[0035] (4) After the step (3) is kept warm, the mixture is cooled to room temperature, and the reaction product is neutralized with a 30 wt % sodium hydroxide solution, and the pH is controlled to be 6-8, to obtain a silane-modified polycarboxylic acid water-reducing agent.

[0036] The average particle size of fly ash used in the following examples and comparative examples of the present invention is 3.0 μm and the density is 2.21 g / cm 3 The particle size of the mineral powder used is less than 45μm. The average particle size of the ceramsite used is 15.7mm. The average particle size of the machine-made sand used is 2.3mm. The cement used is PO42.5 grade ordinary Portland cement. The average length of the steel fiber used is 17mm and the average diameter is 0.2mm.

[0037] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0038] Example 1

[0039] A high-lift pumping concrete is composed of the following raw materials in parts by mass:

[0040] 470 parts of cement, 180 parts of fly ash, 90 parts of mineral powder, 720 parts of expanded clay, 380 parts of machine-made sand, 75 parts of steel fiber, 4.5 parts of sodium gluconate, 25 parts of water reducer (composed of polycarboxylate water reducer and sodium lignin sulfonate in a mass ratio of 1:4.5) and 140 parts of water.

[0041] Preparation of high lift pumped concrete:

[0042] Put mineral powder, ceramsite, machine-made sand, steel fiber and water into a mixer and mix them evenly to obtain a mixture;

[0043] Then, cement, fly ash, sodium gluconate and a water reducing agent are added to the mixture and stirred evenly to obtain an admixture, which is then pumped into a mold and cured to obtain high-lift pumped concrete.

[0044] Example 2

[0045] A high-lift pumping concrete is composed of the following raw materials in parts by mass:

[0046] 400 parts of cement, 200 parts of fly ash, 60 parts of mineral powder, 750 parts of expanded clay, 350 parts of machine-made sand, 50 parts of steel fiber, 1 part of sodium gluconate, 20 parts of water reducer (composed of polycarboxylic acid water reducer and sodium lignin sulfonate in a mass ratio of 1:5) and 120 parts of water.

[0047] Preparation of high lift pumped concrete:

[0048] Put mineral powder, ceramsite, machine-made sand, steel fiber and water into a mixer and mix them evenly to obtain a mixture;

[0049] Then, cement, fly ash, sodium gluconate and a water reducing agent are added to the mixture and stirred evenly to obtain an admixture, which is then pumped into a mold and cured to obtain high-lift pumped concrete.

[0050] Comparative Example 1

[0051] The only difference from Example 1 is that the addition of polycarboxylate water-reducing agent is omitted and an equal mass of sodium lignin sulfonate is added.

[0052] Comparative Example 2

[0053] The only difference from Example 1 is that the addition of sodium lignin sulfonate is omitted and an equal mass of polycarboxylate water reducer is added.

[0054] Comparative Example 3

[0055] The only difference from Example 1 is that 300 parts of ceramsite are replaced by 300 parts of machine-made sand.

[0056] Comparative Example 4

[0057] The difference from Example 1 is only that the addition of steel fiber is omitted and the ceramsite of equal mass is supplemented.

[0058] Comparative Example 5

[0059] The only difference from Example 1 is that the addition of mineral powder is omitted and an equal mass of ceramsite is supplemented.

[0060] Comparative Example 6

[0061] The only difference from Example 1 is that the amount of mineral powder added is changed to 150 parts.

[0062] Comparative Example 7 (conventional concrete)

[0063] A concrete composed of the following raw materials in parts by mass:

[0064] 470 parts of cement, 180 parts of fly ash, 720 parts of expanded clay, 380 parts of machine-made sand and 140 parts of water.

[0065] Preparation of concrete:

[0066] Put ceramsite, machine-made sand and water into a mixer and mix them evenly to obtain a mixture;

[0067] Then, cement and fly ash are added to the mixture, stirred evenly to obtain an admixture, which is then cured in a mold to obtain concrete.

[0068] Effect verification

[0069] (1) The products of each embodiment and comparative example were subjected to performance tests.

[0070] Referring to the Standard for Test Methods for Performance of Ordinary Concrete Mixtures (GBT 50080-2016) and 10 New Technologies in the Construction Industry (2017 Edition), the initial expansion, 2h expansion, expansion after 300m pumping, and water bleeding rate of concrete were tested. The test results are shown in Table 1.

[0071] The standard test blocks were made according to the Standard Test Methods for Mechanical Properties of Ordinary Concrete GB / T50081-2019, and the compressive strength of the standard test blocks was measured after curing for 7d and 28d. The test results are shown in Table 2.

[0072] Table 1

[0073]

[0074] Table 2

[0075]

[0076] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A high-lift pumping concrete, characterized in that: Raw materials, calculated by mass, include: 400-500 parts of cement, 150-200 parts of fly ash, 60-100 parts of mineral powder, 700-750 parts of coarse aggregate, 300-400 parts of fine aggregate, 50-90 parts of fiber, 1-5 parts of retarder, 20-25 parts of water reducer and 120-170 parts of water; The water reducer comprises a polycarboxylate water reducer and sodium lignin sulfonate.

2. The high-lift pumping concrete according to claim 1, characterized in that: The mass ratio of the polycarboxylate water reducer to sodium lignin sulfonate is 1:3.5-5.

3. The high-lift pumping concrete according to claim 1, characterized in that: The average particle size of the fly ash is less than 5 μm.

4. The high-lift pumping concrete according to claim 1, characterized in that: The coarse aggregate is ceramsite and / or pebbles.

5. The high-lift pumping concrete according to claim 1, characterized in that: The fine aggregate is one or more of mineral powder, river sand and machine-made sand.

6. The high-lift pumping concrete according to claim 1, characterized in that: The fibers are steel fibers; the average length of the fibers is 5-20 mm, and the average diameter is 0.1-0.3 mm.

7. The high-lift pumping concrete according to claim 1, characterized in that: The retarder is sodium gluconate.

8. The high-lift pumped concrete according to claim 1, characterized in that: The high-lift pumping concrete is composed of the following raw materials in parts by mass: 470 parts of cement, 180 parts of fly ash, 90 parts of mineral powder, 720 parts of coarse aggregate, 380 parts of fine aggregate, 75 parts of fiber, 4.5 parts of retarder, 25 parts of water reducer and 140 parts of water.

9. A method for preparing high-lift pumped concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: The mineral powder, coarse aggregate, fine aggregate, fiber and water are mixed to obtain a mixture; Cement, fly ash, retarder and water reducing agent are added to the mixture to obtain the high-lift pumping concrete.

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