Reinforced freeze-thaw-resistant premixed concrete and preparation method thereof

Abstract

The invention discloses enhanced freeze-thaw resistant premixed concrete, and belongs to the technical field of concrete. The reinforced freeze-thaw resistant premixed concrete is prepared from the following raw materials: Portland cement, fly ash, fibers, a large-foam air entraining agent, a small-foam air entraining agent, a waterproof agent, medium sand, gravel and water, and the weight ratio of the large-foam air entraining agent to the small-foam air entraining agent is 1: (1-100). According to the reinforced freeze-thaw-resistant premixed concrete disclosed by the invention, the large air entraining agent and the small air entraining agent are introduced, so that the distribution condition of bubbles in the concrete is changed, the compressive strength is improved, the freeze-thaw resistance is improved, and the freeze-thaw-resistant grade reaches F250.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to an enhanced freeze-thaw resistant ready-mixed concrete and a preparation method thereof. Background Art

[0002] Compared with ordinary concrete, freeze-thaw resistant concrete is a high-performance material designed specifically for low-temperature environments, and can still maintain the structural integrity and performance after multiple freeze-thaw cycles. In cold regions, parts such as the outer walls and roofs of buildings are often faced with frequent freeze-thaw tests, and freeze-thaw resistant concrete can effectively resist this kind of damage and protect the structure from being damaged. This kind of concrete not only performs well in the short term, but also can maintain good performance during long-term use, significantly reducing the maintenance and repair costs. It is widely used in various scenarios such as building structures, bridges, roads, water conservancy projects, underground projects and artificial ice surface bearing layers in cold regions, effectively improving the durability and safety of these engineering structures, and at the same time reducing the later maintenance costs.

[0003] The current freeze-thaw resistant concrete can only be applicable to environments with temperatures of -20°C and above, and its performance will be greatly reduced at lower temperatures.

[0004] In low-temperature environments, in addition to regions, there are also some specific scenarios. For example, in the southern regions of China, although the climate is relatively warm, in some special scenarios, the freeze-thaw resistance performance of concrete still needs to be considered when storing liquid nitrogen tanks in buildings. The boiling point of liquid nitrogen is about -196°C. Even in the southern regions, the local environmental temperature around the liquid nitrogen tank will be significantly reduced due to the low-temperature characteristics of liquid nitrogen. Therefore, the building floor for storing liquid nitrogen tanks needs to use freeze-thaw resistant concrete to ensure durability and safety in low-temperature environments. Summary of the Invention

[0005] In view of the above problems, the present invention provides an enhanced freeze-thaw resistant ready-mixed concrete, which contains a variety of air-entraining agents capable of generating multi-scale pore structures.

[0006] The first aspect of the present invention is to disclose an enhanced freeze-thaw resistant ready-mixed concrete, and the raw materials for preparation include portland cement, fly ash, fiber, large-bubble air-entraining agent, small-bubble air-entraining agent, waterproof agent, medium sand, crushed stone and water, wherein the weight ratio of the large-bubble air-entraining agent to the small-bubble air-entraining agent is 1:(1 - 100).

[0007] In some preferred embodiments of the present invention, the raw materials for preparation include portland cement, fly ash, fiber, large-bubble air-entraining agent, small-bubble air-entraining agent, waterproof agent, medium sand, crushed stone and water, wherein the weight ratio of the large-bubble air-entraining agent to the small-bubble air-entraining agent is 1:(4 - 5).

[0008] In some preferred embodiments of the present invention, the raw materials for preparation include the following components in parts by weight:

[0009] 40 - 45 parts of portland cement, 5 - 10 parts of fly ash, 1 - 5 parts of fiber, 0.01 - 0.5 parts of large - bubble air - entraining agent, 0.1 - 1.0 parts of small - bubble air - entraining agent, 0.5 - 3 parts of waterproofing agent, 20 - 40 parts of medium sand, 30 - 50 parts of crushed stone, 15 - 40 parts of water.

[0010] In some preferred embodiments of the present invention, the raw materials for preparation include the following components in parts by weight:

[0011] 40 - 45 parts of portland cement, 5 - 10 parts of fly ash, 1 - 5 parts of fiber, 0.1 - 0.2 parts of large - bubble air - entraining agent, 0.4 - 0.5 parts of small - bubble air - entraining agent, 0.5 - 3 parts of waterproofing agent, 20 - 40 parts of medium sand, 30 - 50 parts of crushed stone, 15 - 40 parts of water.

[0012] In some embodiments of the present invention, the large - bubble air - entraining agent is sodium lauryl sulfate.

[0013] In some embodiments of the present invention, the small - bubble air - entraining agent is triterpenoid saponin.

[0014] In some embodiments of the present invention, the fiber is polypropylene fiber with a length of 3 - 9 mm.

[0015] In some embodiments of the present invention, the waterproofing agent is sodium methyl silicate.

[0016] In some embodiments of the present invention, the particle size of the crushed stone is 5 - 20 mm.

[0017] The second aspect of the present invention lies in disclosing a preparation method of the enhanced freeze - thaw resistant ready - mixed concrete described in the first aspect, comprising the following steps:

[0018] S01, Take ordinary portland cement, class - I fly ash and water, mix them, and add polypropylene fiber and mix again;

[0019] S02, Add the large - bubble air - entraining agent, small - bubble air - entraining agent, and waterproofing agent, and mix;

[0020] S03, Add medium sand and mix, then add crushed stone and mix to obtain concrete.

[0021] Advantages of the present invention:

[0022] The enhanced freeze - thaw resistant ready - mixed concrete of the present invention introduces two kinds of air - entraining agents of different sizes, changes the distribution of air bubbles in the concrete, improves the compressive strength, and improves the freeze - thaw resistance performance, reaching the freeze - thaw resistance grade of F250.

[0023] The enhanced freeze - thaw resistant ready - mixed concrete of the present invention can be applied to low - temperature scenarios in cold climate regions or general regions. Detailed implementation mode

[0024] The following uses specific specific examples to illustrate the implementation modes of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Unless otherwise specified, the examples and comparative examples are parallel tests with the same components, component contents, preparation steps, and preparation parameters.

[0026] In the following examples and comparative examples, the large air-entraining agent is sodium lauryl sulfate, the small air-entraining agent is triterpenoid saponin, and the waterproofing agent is sodium metasilicate.

[0027] Example 1

[0028] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete includes the following steps:

[0029] (1) Take 40 kg of ordinary Portland cement and 10 kg of class I fly ash and put them into a mixer, add 20 kg of water, stir for 3 min, and then add 5 kg of polypropylene fiber with a diameter of 3 - 9 mm and stir for 5 min;

[0030] (2) Add 0.1 kg of large air-entraining agent, 0.5 kg of small air-entraining agent, and 1 kg of waterproofing agent, and stir for 3 min;

[0031] (3) Add 30 kg of medium sand for construction, stir for 3 min, and then add 40 kg of crushed stone with a particle size of 5 - 20 mm and stir for 5 min to obtain concrete.

[0032] Example 2

[0033] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete includes the following steps:

[0034] (1) Take 45 kg of ordinary Portland cement and 10 kg of class I fly ash and put them into a mixer, add 25 kg of water, stir for 3 min, and then add 5 kg of polypropylene fiber with a diameter of 3 - 9 mm and stir for 5 min;

[0035] (2) Add 0.1 kg of large air-entraining agent, 0.5 kg of small air-entraining agent, and 1 kg of waterproofing agent, and stir for 3 min;

[0036] (3) Add 30 kg of medium sand for construction, stir for 3 min, and then add 40 kg of crushed stone with a particle size of 5 - 20 mm and stir for 5 min to obtain concrete.

[0037] Example 3

[0038] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, comprising the following steps:

[0039] (1) Take 40 kg of ordinary Portland cement and 5 kg of class I fly ash and put them into a mixer, add 20 kg of water, stir for 3 min, then add 4 kg of polypropylene fiber with a diameter of 3-9 mm, and stir for 5 min;

[0040] (2) Add 0.1 kg of large-bubble air-entraining agent, 0.4 kg of small-bubble air-entraining agent, and 1 kg of waterproofing agent, and stir for 3 min;

[0041] (3) Add 30 kg of medium sand for construction, stir for 3 min, then add 40 kg of crushed stone with a particle size of 5-20 mm and stir for 5 min to obtain concrete.

[0042] Example 4

[0043] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, comprising the following steps:

[0044] (1) Take 40 kg of ordinary Portland cement and 10 kg of class I fly ash and put them into a mixer, add 20 kg of water, stir for 3 min, then add 5 kg of polypropylene fiber with a diameter of 3-9 mm, and stir for 5 min;

[0045] (2) Add 0.1 kg of large-bubble air-entraining agent, 1.0 kg of small-bubble air-entraining agent, and 1 kg of waterproofing agent, and stir for 3 min;

[0046] (3) Add 30 kg of medium sand for construction and stir for 3 min, then add 40 kg of crushed stone with a particle size of 5-20 mm and stir for 5 min to obtain concrete.

[0047] Example 5

[0048] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, comprising the following steps:

[0049] (1) Take 40 kg of ordinary Portland cement and 10 kg of class I fly ash and put them into a mixer, add 20 kg of water, stir for 3 min, then add 5 kg of polypropylene fiber with a diameter of 3-9 mm, and stir for 5 min;

[0050] (2) Add 0.01 kg of large-bubble air-entraining agent, 0.5 kg of small-bubble air-entraining agent, and 1 kg of waterproofing agent, and stir for 3 min;

[0051] (3) Add 30 kg of medium sand for construction and stir for 3 min, then add 40 kg of crushed stone with a particle size of 5-20 mm and stir for 5 min to obtain concrete.

[0052] Comparative Example 1

[0053] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, different from Example 1 in that 0.6 kg of large-bubble air-entraining agent is added and no small-bubble air-entraining agent is added.

[0054] Comparative Example 2

[0055] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, different from Example 1 in that 0.6 kg of small-bubble air-entraining agent is added and no large-bubble air-entraining agent is added.

[0056] Comparative Example 3

[0057] A preparation method of enhanced freeze-thaw resistant ready-mixed concrete, different from Example 1 in that the preparation method includes the following steps:

[0058] (1) Take 40 kg of ordinary Portland cement and 5 kg of class I fly ash and put them into a mixer, add 20 kg of water, and stir for 3 min;

[0059] (2) Add 0.1 kg of large-bubble air-entraining agent, 0.4 kg of small-bubble air-entraining agent, and 1 kg of waterproof agent, and stir for 3 min;

[0060] (3) Add 30 kg of medium sand for construction, stir for 3 min, then add 40 kg of gravel with a particle size of 5 - 20 mm and stir for 5 min; then add 4 kg of polypropylene fiber with a particle size of 3 - 9 mm and stir for 5 min to obtain concrete.

[0061] Performance test:

[0062] For the enhanced freeze-thaw resistant ready-mixed concrete obtained in the examples and comparative examples, the 28-day strength was detected according to the compressive strength test in Section 6 of "Standard Test Method for Mechanical Properties of Ordinary Concrete" (GB / T 50081 - 2002). The freeze-thaw resistance grade was determined according to the method in "Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082 - 2009). The results are shown in Table 1.

[0063] Table 1 Performance test

[0064] 28-day compressive strength Mpa Freeze-thaw resistance grade Example 1 73.82 F250 Example 2 71.27 F250 Example 3 65.35 F250 Example 4 59.15 F250 Example 5 62.57 F250 Comparative Example 1 45.07 F150 Comparative Example 2 49.10 F150 Comparative Example 3 57.10 F250

[0065] The results show that the freeze-thaw resistance grades of Examples 1 - 5 using both large and small air-entraining agents are better than those of Comparative Example 1 and Comparative Example 2 using only one air-entraining agent. Among them, the strength loss rate of Examples 1 - 3 after 300 freeze-thaw cycles is ≤10%, which is significantly better than that of Examples 4 and 5, and is applicable to the extreme environment of -40°C. The compressive strength of Comparative Example 3 with the changed addition timing of polypropylene fiber also decreases, but the freeze-thaw resistance grade remains unchanged.

[0066] Microstructure observation:

[0067] The enhanced frost-resistant and thaw-resistant ready-mixed concrete obtained in the examples and comparative examples was used to prepare concrete test blocks of standard size (such as cubic test blocks of 150 mm×150 mm×150 mm). The fresh concrete was filled into the test mold and vibrated on a vibrating table for about 10 seconds to ensure the compaction of the concrete. After the concrete hardened (usually 24 hours), it was demolded, and each side of the test block was numbered and photographed. The bubble distribution was recorded.

[0068] The data shows that in Comparative Example 1, the bubbles larger than 3 mm accounted for more than 80%, and the bubbles smaller than 3 mm were less than 5%; in Comparative Example 2, the bubbles smaller than 3 mm accounted for more than 80%, and the bubbles larger than 3 mm were less than 3%. In Examples 1-3, the bubbles larger than 3 mm accounted for about 30%, and the bubbles smaller than 3 mm accounted for 40%. In Comparative Example 3, the bubbles larger than 3 mm accounted for 15%, and the bubbles smaller than 3 mm were less than 35%. The results show that using two types of air-entraining agents of different sizes does change the bubble distribution in the concrete and improves the frost-resistant and thaw-resistant performance. The addition timing of the polypropylene fiber also slightly changes the bubble distribution in the concrete.

[0069] The specific preferred embodiments and examples of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments and examples. Various changes can be made without departing from the concept of the present invention within the scope of knowledge possessed by those skilled in the art.

Claims

1. An enhanced frost-resistant and thaw-resistant ready-mixed concrete, characterized in that, The raw materials for preparation include Portland cement, fly ash, fiber, large-bubble air-entraining agent, small-bubble air-entraining agent, waterproof agent, medium sand, crushed stone and water. Among them, the weight ratio of the large-bubble air-entraining agent to the small-bubble air-entraining agent is 1:(1 - 100).

2. The enhanced freeze-thaw resistant ready-mixed concrete according to claim 1, wherein The raw materials for preparation include Portland cement, fly ash, fiber, large-bubble air-entraining agent, small-bubble air-entraining agent, waterproof agent, medium sand, crushed stone and water. Among them, the weight ratio of the large-bubble air-entraining agent to the small-bubble air-entraining agent is 1:(4 - 5).

3. The enhanced freeze-thaw resistant ready-mixed concrete according to claim 1 or 2, wherein The raw materials for preparation include the following components in parts by weight: 40 - 45 parts of Portland cement, 5 - 10 parts of fly ash, 1 - 5 parts of fiber, 0.01 - 0.5 parts of large-bubble air-entraining agent, 0.1 - 1.0 parts of small-bubble air-entraining agent, 0.5 - 3 parts of waterproof agent, 20 - 40 parts of medium sand, 30 - 50 parts of crushed stone, 15 - 40 parts of water.

4. The enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-3, characterized in that, The raw materials for preparation include the following components in parts by weight: 40 - 45 parts of Portland cement, 5 - 10 parts of fly ash, 1 - 5 parts of fiber, 0.1 - 0.2 parts of large-bubble air-entraining agent, 0.4 - 0.5 parts of small-bubble air-entraining agent, 0.5 - 3 parts of waterproof agent, 20 - 40 parts of medium sand, 30 - 50 parts of crushed stone, 15 - 40 parts of water.

5. The enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-4, characterized in that The large-bubble air-entraining agent is sodium lauryl sulfate.

6. The enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-5, characterized in that, The small-bubble air-entraining agent is triterpenoid saponin.

7. The enhanced frost-resistant and thaw-resistant ready-mixed concrete according to any one of claims 1-6, characterized in that The fiber is polypropylene fiber with a length of 3 - 9 mm.

8. The enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-7, characterized in that, The waterproof agent is sodium methyl silicate.

9. The enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-8, characterized in that, The particle size of the crushed stone is 5 - 20 mm.

10. A method for preparing the enhanced freeze-thaw resistant ready-mixed concrete according to any one of claims 1-9, characterized in that, It includes the following steps: S01, Take ordinary Portland cement, grade-I fly ash and water, mix them, and add polypropylene fiber and mix again; S02, Add the large-bubble air-entraining agent, small-bubble air-entraining agent and waterproof agent, and mix; S03, Add medium sand and mix, then add crushed stone and mix to obtain concrete.