High-mixing-amount superfine fly ash concrete and preparation method thereof

Abstract

The invention discloses high-content superfine fly ash concrete and a preparation method thereof. The high-content superfine fly ash concrete comprises the following components in parts by weight: 50-55 parts of superfine fly ash; 5-10 parts by weight of first-grade fly ash; 5-10 parts by weight of secondary fly ash; 30 to 37 parts by weight of cement; 130 parts by weight of river sand; 0.33 to 0.9 part by weight of a water reducing agent; 195 parts by weight of broken stone; the total doping amount of the superfine fly ash, the first-grade fly ash and the second-grade fly ash is 70%-80% of the total amount of the cementing material. According to the concrete, three-stage synergy of the superfine fly ash (50% or above), the first-stage fly ash and the second-stage fly ash is guaranteed, the total doping amount reaches 70% or above of a cementing material, meanwhile, the 7-day compressive strength is 16.2-24 MPa, the 28-day strength is larger than or equal to 30 MPa, the mechanical property and durability of the concrete are guaranteed, the manufacturing cost is low, the process is simple, technical support is provided for high-value utilization of industrial solid waste, and the concrete has a good application prospect. The method is suitable for the green low-carbon building field.

Description

Technical Field

[0001] The present invention relates to the technical field of green building, and more specifically to a high-volume ultra-fine fly ash concrete and a preparation method thereof. Background Art

[0002] As the main by-product of coal-fired power plants, the emissions of fly ash have been increasing year by year with the development of the power industry, and it has become a large-scale industrial solid waste in China. However, more than half of the fly ash has not been effectively utilized, resulting in a large amount of fly ash becoming industrial waste and imposing a burden on the environment. As a pozzolanic material, the reasonable application of fly ash in concrete can not only achieve the efficient utilization of resources, reduce production costs, but also improve the performance of concrete to a certain extent. Therefore, how to treat and utilize fly ash has become a research hotspot.

[0003] In the existing fly ash concrete, the dosage of fly ash is generally small, and most of it is a single type of fly ash, with low utilization rate of fly ash. Excessive dosage of fly ash is likely to cause the floating of fly ash particles and bleeding, and the early strength of concrete drops significantly. At the same time, to improve the mechanical properties of fly ash, activators are added, increasing the preparation cost and hindering the efficient resource utilization of fly ash.

[0004] Patent application CN112430015A discloses a high-volume fly ash concrete and a preparation method thereof. Although this invention uses fly ash as a raw material to prepare concrete, the dosage of fly ash is only about 40% of the cementitious material. Patent application CN105731919B discloses a high-ultra fly ash concrete. Although the dosage of fly ash in the concrete of this invention can reach 80% of the cementitious material, additional water reducing agent and air entraining agent need to be added, increasing the preparation cost.

[0005] Therefore, it is urgent to develop a high-volume ultra-fine fly ash concrete and a preparation method thereof, which can ensure that while increasing the dosage of fly ash, the fly ash concrete meets the mechanical properties and at the same time meets the requirements of low cost and low energy consumption. Summary of the Invention

[0006] In view of this, the problems existing in the prior art

[0007] (1) Low utilization rate of fly ash and small dosage of fly ash.

[0008] (2) The existing fly ash concrete has the characteristics of low performance, high cost and high energy consumption.

[0009] The object of the present invention is to overcome the above problems existing in the prior art, and to provide a high-volume ultra-fine fly ash concrete and a preparation method thereof. The technical solution adopts a three-stage ratio of ultra-fine fly ash, first-class fly ash, and second-class fly ash, increases the fly ash content to 70% and above, realizes the comprehensive utilization of solid waste, and through optimizing the water-binder ratio and the dosage of polycarboxylate water reducer, the 7-day compressive strength ≥ 15 MPa and the 28-day strength ≥ 30 MPa can be achieved without chemical activators, making the concrete have good mechanical properties.

[0010] The present invention provides a high-volume ultra-fine fly ash concrete and a preparation method thereof.

[0011] To achieve the above object, the present invention provides the following technical solution, which includes the following components by weight:

[0012] Ultra-fine fly ash: 50-55 parts by weight;

[0013] First-class fly ash: 5-10 parts by weight;

[0014] Second-class fly ash: 5-10 parts by weight;

[0015] Cement: 30-37 parts by weight;

[0016] River sand: 130 parts by weight;

[0017] Water reducer: 0.33-0.9 parts by weight;

[0018] Crushed stone: 195 parts by weight;

[0019] The total content of the ultra-fine fly ash, first-class fly ash, and second-class fly ash is 70%-80% of the total amount of cementitious materials.

[0020] Preferably, in the above high-volume ultra-fine fly ash concrete and its preparation method, the cement is PO42.5 ordinary Portland cement;

[0021] The water reducer is a polycarboxylate superplasticizer with a water reduction rate ≥ 27%;

[0022] The water is ordinary domestic water.

[0023] Preferably, in the above high-volume ultra-fine fly ash concrete and its preparation method, the physical and chemical properties of the fly ash are:

[0024] Ultra-fine fly ash: the residue on a 45μm square-hole sieve is 1.5%-3%, and the strength activity index is 85%-90%;

[0025] First-class fly ash: the residue on a 45μm square-hole sieve is 10%-12%, and the strength activity index is 75%-80%;

[0026] Secondary fly ash: residue on 45μm square-hole sieve is 14%-16%, strength activity index is 75%-80%;

[0027] The water demand ratios of the three kinds of fly ash are all 95%-97%, and the loss on ignition is all 1.5%-2%.

[0028] Preferably, in the above-mentioned high-volume ultrafine fly ash concrete and its preparation method, the river sand is standard river sand with a particle size less than 4.7mm;

[0029] The crushed stone is 5-20mm continuously graded crushed stone.

[0030] Preferably, in the above-mentioned high-volume ultrafine fly ash concrete and its preparation method, the following steps are included:

[0031] (1) Mix and stir cement, ultrafine fly ash, primary fly ash, secondary fly ash and river sand to obtain mixed dry material A;

[0032] (2) Add crushed stone and 50% of the total water amount to mixed dry material A, and stir until the surface of the aggregate is wetted to obtain mixture B;

[0033] (3) Add polycarboxylate water reducer and the remaining water amount to mixture B, and stir until uniform to obtain mixture C;

[0034] (4) Pour mixture C into the mold, demold after vibrating tightly, and carry out standard curing.

[0035] Preferably, in the above-mentioned high-volume ultrafine fly ash concrete and its preparation method, the stirring rate in step (1) is 62.5r / min, and the stirring time is 23min;

[0036] The stirring rate in step (2) is 62.5r / min, and the stirring time is 2min;

[0037] The stirring rate in step (3) is 62.5r / min, and the stirring time is 4-6min.

[0038] In step (4), mixture C is poured into the mold in two times, and the vibration time after each pouring is ≥30 seconds, and the total vibration time is ≥1min;

[0039] Preferably, in the above-mentioned high-volume ultrafine fly ash concrete and its preparation method, the standard curing conditions are: temperature 20±2°C, humidity ≥95%, and curing age ≥7 days.

[0040] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a high-volume ultra-fine fly ash concrete and a preparation method thereof. The concrete of the present invention ensures the synergy of ultra-fine fly ash (more than 50%), primary fly ash, and secondary fly ash, and the total dosage reaches more than 70% of the cementitious material. At the same time, the 7-day compressive strength reaches 16.2-24 MPa, and the 28-day strength is ≥30 MPa, ensuring the mechanical properties and durability of the concrete. The production cost is low, and the process is simple, providing technical support for the high-value utilization of industrial solid waste and being applicable to the field of green and low-carbon buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0042] Figure 1 It is a schematic diagram of the preparation method provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0044] Example 1

[0045] The high-volume ultra-fine fly ash concrete in this example is composed of the following components in parts by weight: 55 parts of ultra-fine fly ash, 10 parts of primary fly ash, 5 parts of secondary fly ash, 30 parts of cement, 130 parts of river sand, 195 parts of crushed stone, 35 parts of mixing water, and 0.9 parts of water reducing agent; among them, the water demand ratios of ultra-fine fly ash, primary fly ash, and secondary fly ash are all 95%-97%, and the loss on ignition is all 1.5%-2%. The fineness of ultra-fine fly ash is 1.5%-3% of the residue on a 45μm square-hole sieve, and the strength activity index is 85%-90%; the fineness of primary fly ash is 10%-12% of the residue on a 45μm square-hole sieve, and the strength activity index is 75%-80%; the fineness of secondary fly ash is 14%-16% of the residue on a 45μm square-hole sieve, and the strength activity index is 75%-80%; the cement is PO42.5 ordinary Portland cement; the river sand is standard river sand with a particle size less than 4.7 mm; the crushed stone is 5-20 mm continuously graded crushed stone; the water is ordinary domestic water; the water reducing agent is a pure water-reducing type water reducing agent produced by Shanxi Feike New Materials Technology Co., Ltd.

[0046] AsFigure 1 As shown in the figure, the preparation method of high-volume ultra-fine fly ash concrete in this embodiment includes the following steps:

[0047] Step (1): Put 30 parts of cement, 55 parts of ultra-fine fly ash, 10 parts of first-class fly ash, 5 parts of second-class fly ash, and 130 parts of river sand into a mixer in sequence, and stir at a rate of 62.5 r / min for 2 - 3 min until uniform to obtain mixture A.

[0048] Step (2): Add 195 parts of crushed stone and 17.5 parts of water to the mixer, and stir at a rate of 62.5 r / min for 2 min to obtain mixture B.

[0049] Step (3): Add 0.9 part of water reducer and 17.5 parts of water to obtain mixture C.

[0050] Step (4): Uniformly apply a release agent to the inner surface of the mold, then pour mixture C into the mold in two times, vibrate after each pouring, the total vibration time is not less than 1 min, let it stand, demold, and place it in a standard curing room for curing. The curing conditions of the standard curing room are: the temperature is controlled at 20 ± 2 °C, the humidity is greater than or equal to 95%, and take it out after curing to the specified age, then high-volume ultra-fine fly ash concrete can be obtained.

[0051] In order to test the mechanical properties of the high-volume ultra-fine fly ash concrete prepared in the embodiment, the casting mold used in this embodiment is 100 mm × 100 mm × 100 mm, and the strength of 150 mm standard specimens in actual engineering is correlated through a conversion coefficient (0.95). According to the test method specified in the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081 - 2019), the compressive performance test is carried out, and the compressive strength test is carried out on the fly ash concrete compressive specimens with curing ages of 7 d and 28 d respectively.

[0052] Example 2

[0053] The high-volume ultra-fine fly ash concrete in this embodiment is composed of the following components in parts by weight: 55 parts of ultra-fine fly ash, 5 parts of first-class fly ash, 10 parts of second-class fly ash, 30 parts of cement, 130 parts of river sand, 195 parts of crushed stone, 44 parts of mixing water, and 0.4 part of water reducer.

[0054] The preparation method of the high-volume ultra-fine fly ash concrete in this embodiment is the same as that in Example 1.

[0055] The size of the casting mold and the test method for compressive strength of the high-volume ultra-fine fly ash concrete in this embodiment are the same as those in Example 1.

[0056] Example 3

[0057] The high-volume ultrafine fly ash concrete of this embodiment is composed of the following components in parts by weight: 55 parts of ultrafine fly ash, 10 parts of Class I fly ash, 5 parts of Class II fly ash, 30 parts of cement, 130 parts of river sand, 195 parts of crushed stone, 38 parts of mixing water, and 0.5 part of water reducer.

[0058] The preparation method of the high-volume ultrafine fly ash concrete of this embodiment is the same as that of Embodiment 1.

[0059] The mold size and compressive strength test method of the high-volume ultrafine fly ash concrete poured in this embodiment are the same as those of Embodiment 1.

[0060] Embodiment 4

[0061] The high-volume ultrafine fly ash concrete of this embodiment is composed of the following components in parts by weight: 50 parts of ultrafine fly ash, 10 parts of Class I fly ash, 10 parts of Class II fly ash, 30 parts of cement, 130 parts of river sand, 195 parts of crushed stone, 35 parts of mixing water, and 0.33 part of water reducer.

[0062] The preparation method of the high-volume ultrafine fly ash concrete of this embodiment is the same as that of Embodiment 1.

[0063] The mold size and compressive strength test method of the high-volume ultrafine fly ash concrete poured in this embodiment are the same as those of Embodiment 1.

[0064] After testing, the compressive strengths of the high-volume ultrafine fly ash concretes of Embodiments 1 to 4 are shown in Table 1.

[0065] Table 1 Compressive strengths of high-volume ultrafine fly ash concretes

[0066]

[0067] It can be seen from Table 1 that the 7-day compressive strength of the concrete of the present invention is 16.2 - 24 MPa, and the 28-day strength ≥ 30 MPa. The fly ash content of the concrete of the present invention reaches more than 70% of the cementitious materials, which can greatly reduce the material cost, and is more in line with the environmental protection concept of solid waste resource reuse. At the same time, a three-level ratio of ultrafine fly ash, Class I fly ash, and Class II fly ash is adopted to reinforce the high-volume fly ash concrete, which not only reduces the manufacturing cost of the concrete, but also ensures the corresponding construction performance and service performance. The preparation process flow is simple, the operation is convenient and does not require expensive equipment, achieving low cost and low energy consumption, and is suitable for large-scale popularization and application in actual projects.

[0068] The above has provided a detailed introduction to a high-volume ultra-fine fly ash concrete and its preparation method according to the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. At the same time, for those of ordinary skill in the art, based on the idea of the present application, other different forms of changes can be made on the basis of the above description. In summary, the content of this specification should not be construed as a limitation to the present application.

[0069] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0070] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-volume ultra-fine fly ash concrete, characterized in that, It includes the following components by weight parts: ultrafine fly ash: 50 - 55 weight parts; Grade I fly ash: 5 - 10 weight parts; Grade II fly ash: 5 - 10 weight parts; Cement: 30 - 37 weight parts; River sand: 130 weight parts; Water reducing agent: 0.33 - 0.9 weight parts; Crushed stone: 195 weight parts; The total dosage of the ultrafine fly ash, Grade I fly ash, and Grade II fly ash is 70% - 80% of the total amount of cementitious materials.

2. The high-volume ultrafine fly ash concrete according to claim 1, wherein: The cement is PO42.5 ordinary Portland cement; The water reducing agent is a polycarboxylate superplasticizer with a water reducing rate ≥ 27%; The water is ordinary domestic water.

3. The high-volume ultrafine fly ash concrete according to claim 1, wherein The physical and chemical properties of the fly ash are as follows: Ultrafine fly ash: the residue on a 45μm square hole sieve is 1.5% - 3%, and the strength activity index is 85% - 90%; Grade I fly ash: the residue on a 45μm square hole sieve is 10% - 12%, and the strength activity index is 75% - 80%; Grade II fly ash: the residue on a 45μm square hole sieve is 14% - 16%, and the strength activity index is 75% - 80%; The water demand ratios of the three kinds of fly ash are all 95% - 97%, and the loss on ignition is all 1.5% - 2%.

4. The high-volume ultrafine fly ash concrete according to claim 1, wherein: The river sand is standard river sand with a particle size less than 4.7mm; The crushed stone is continuously graded crushed stone with a size of 5 - 20mm.

5. A method for preparing high-volume ultrafine fly ash concrete according to any one of claims 1-4, characterized in that, It includes the following steps: (1) Mix and stir the cement, ultrafine fly ash, Grade I fly ash, Grade II fly ash, and river sand to obtain a mixed dry material A; (2) Add the crushed stone and 50% of the total water amount to the mixed dry material A, and stir until the surface of the aggregate is wetted to obtain a mixed material B; (3) Add the polycarboxylate water reducing agent and the remaining water amount to the mixed material B, and stir until it is uniform to obtain a mixed material C; (4) Pour the mixed material C into a mold, demold it after vibrating it densely, and conduct standard curing.

6. The preparation method according to claim 5, wherein: The stirring rate in step (1) is 62.5r / min, and the stirring time is 23min; The stirring rate in step (2) is 62.5r / min, and the stirring time is 2min; The stirring rate in step (3) is 62.5r / min, and the stirring time is 4 - 6min.

7. The preparation method according to claim 5, wherein: In step (4), the mixed material C is poured into the mold in two times, and the vibration time after each pouring is ≥ 30 seconds, and the total vibration time is ≥ 1min; The standard curing conditions are: temperature 20 ± 2°C, humidity ≥ 95%, and curing age ≥ 7 days.

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