CN116332591B - A kind of basalt fiber reinforced concrete and preparation method thereof - Google Patents

Abstract

The invention discloses basalt fiber reinforced concrete and a preparation method thereof, and belongs to the technical field of concrete, wherein the basalt fiber reinforced concrete comprises the following raw materials in parts by weight: 80-90 parts of fly ash, 25-30 parts of volcanic ash, 240-260 parts of cement, 10-20 parts of modified basalt fiber, 300-480 parts of cobble, 200-260 parts of river sand, 8-20 parts of water reducer and 130-150 parts of water. According to the invention, before basalt fibers are added into concrete, the basalt fibers are modified, so that the problem that basalt fibers are unevenly dispersed in the concrete and the concrete fibers are agglomerated in the concrete is avoided, and the mechanical properties and durability of the concrete are improved.

Description

A kind of basalt fiber reinforced concrete and preparation method thereof

Technical Field

The invention belongs to the technical field of concrete, and in particular relates to basalt fiber reinforced concrete and a preparation method thereof.

Background Art

Ordinary cement concrete is a three-phase concrete. It is made of cementitious materials, granular aggregates, water, and admixtures and admixtures when necessary. It is prepared according to the concrete mix design and test verification, and is mixed evenly, compacted, and cured to form an artificial stone. Concrete will deform under the action of external loads or environmental factors (temperature and humidity). Concrete has low tensile strength and poor deformation performance, and it is difficult to avoid the occurrence of structural cracks caused by concrete deformation. As the strength of concrete continues to increase, its brittleness becomes more and more obvious. Therefore, reducing concrete deformation cracks and enhancing its toughness has become one of the current research focuses on improving concrete performance.

Basalt fiber is made of single-component basalt mineral raw materials through melting and drawing, with an equivalent diameter of 7-15μm. Basalt fiber has a smooth surface, good stability, and excellent flexibility. It can be used as a toughening material in cement-based composite materials. Adding basalt fiber to concrete can increase the toughness of the material and enhance the performance of concrete. However, the basalt fiber just produced is in a bundled state and cannot be directly added to the concrete mixer for mixing. Otherwise, it will cause uneven dispersion of basalt fiber in concrete, causing the fiber to clump in the concrete, greatly limiting the improvement of concrete mechanical properties and durability.

Summary of the invention

In order to solve the above technical problems, the present invention provides a basalt fiber reinforced concrete and a preparation method thereof.

To achieve the above object, the present invention provides a basalt fiber reinforced concrete, which comprises the following raw materials in parts by weight:

80-90 parts of fly ash, 25-30 parts of volcanic ash, 240-260 parts of cement, 10-20 parts of modified basalt fiber, 300-480 parts of pebbles, 200-260 parts of river sand, 8-20 parts of water reducer and 130-150 parts of water.

Furthermore, the basalt fiber reinforced concrete comprises the following raw materials in parts by weight:

80-85 parts of fly ash, 25-28 parts of volcanic ash, 240-250 parts of cement, 10-15 parts of modified basalt fiber, 350-420 parts of pebbles, 220-240 parts of river sand, 8-15 parts of water reducer and 130-140 parts of water.

Furthermore, the fly ash is Class I fly ash, the cement is Class 42.5 ordinary Portland cement, the pebble particle size is 10-20 mm, and the river sand is natural river sand with a fineness modulus of 2.5-3.0 mm.

In the basalt fiber reinforced concrete of the present invention, cement can ensure the early strength of concrete; fly ash can increase the density of concrete and ensure the later strength of concrete; volcanic ash can not only increase the density of concrete, but also improve the workability of concrete and provide some later strength; modified basalt fiber has good temperature resistance, can work continuously in the range of -269 to 700°C, has excellent acid resistance, alkali resistance and corrosion resistance, high tensile strength and ultimate strain rate, large elastic modulus, can increase the structural strength and anti-cracking effect of concrete, and belongs to the silicate series, has good compatibility with cement-based concrete, and can be well dispersed during the mixing process.

Furthermore, the preparation method of the modified basalt fiber is as follows:

a. Place basalt fiber in sodium chloride solution, heat to 50-70°C for 3-5 minutes, then heat to 90-100°C for 1-3 minutes to obtain solution A. During the heating process, seal the device containing sodium chloride solution;

b. Adding sodium dodecylbenzene sulfonate and dimethylformamide to the solution A, performing ultrasonic treatment while stirring, taking out the basalt fiber, and drying to obtain modified basalt fiber.

The present invention uses sodium chloride solution to treat basalt fiber, thereby increasing the activation energy of the basalt fiber surface, and in combination with the heat treatment process, further improving the activation energy, which is beneficial to improving the subsequent binding ability of the basalt fiber with sodium dodecylbenzene sulfonate and dimethylformamide. In the process of combining with sodium dodecylbenzene sulfonate and dimethylformamide, ultrasound can reduce the aggregation of basalt fiber in the dispersion system, promote the effective dispersion of basalt fiber, and prevent the generation of flocculent or hair ball-shaped aggregated fibers. The basalt fiber can form hydrogen bonds or covalent bonds with the active groups of the two, spread on the surface of the basalt fiber and form a continuous new surface layer, repair, fill, and wrap the defects on the surface of the basalt fiber, and soften the basalt fiber to a certain extent, thereby reducing the loss of basalt fiber in the process of mixing with concrete.

Furthermore, in the preparation method of the modified basalt fiber, in step a, the length of the basalt fiber is 3-20 mm and the diameter is 15±2 μm. Basalt fibers of this length can effectively inhibit the cracking of concrete, increase the bonding performance of concrete, and effectively improve the mechanical properties of concrete, such as compression resistance, splitting tensile strength, flexural strength, etc. In addition, the durability of concrete can also be increased.

Furthermore, in step a, the mass fraction of the sodium chloride solution is 10-20%;

The temperature was raised to 50-70°C at a rate of 1-3°C/min, and then raised to 90-100°C at a rate of 3-5°C/min.

Furthermore, in step b, the mass volume ratio of sodium dodecylbenzene sulfonate to the solution A is (3-5) g:100 mL; and the volume ratio of dimethylformamide to the solution A is 0.5-1.5:10.

Furthermore, in step b, the stirring rate is 100-150 r/min.

Furthermore, in step b, the ultrasonic power is 250-300W.

Furthermore, the water reducing agent is a polycarboxylic acid high performance water reducing agent, and its water reducing rate is ≥25%.

A method for preparing the basalt fiber reinforced concrete comprises the following steps:

(1) mixing pebbles, river sand, fly ash, volcanic ash and cement, and stirring evenly to obtain a mixture;

(2) Adding modified basalt fiber to the mixture, stirring evenly, adding a water reducer and water, and continuing to stir evenly to obtain basalt fiber reinforced concrete.

Furthermore, in step (2), after adding the modified basalt fiber, the stirring rate is 800-900r/min; after adding the water reducer and water, the stirring refers to first slow stirring and then fast stirring; the slow stirring time is 10-15min, the speed is 300-500r/min; the fast stirring time is 3-5min, the speed is 700-850r/min. The process of basalt fiber forming a dispersion can be divided into three processes: wetting, diffusion and stabilization, that is, the wetting process in which the air in the fiber bundle is replaced by the solution. The surfactant of the wetted fiber bundle or single fiber is replaced by the dispersion medium, forming a process of mutual repulsion and diffusion at the fiber-water-fiber interface. When basalt fiber is used in concrete, the wet concrete formed by solid building materials, fibers and water is a non-stable dispersion. This non-stable process will undergo uneven changes over time, affecting the performance of the concrete. In order to avoid this effect, the present invention adopts a process of first slow stirring and then fast stirring, avoiding the agglomeration and stratification of the dispersed phase caused by the gravity of the fibers, the precipitation of surfactants and water, thereby greatly improving the bonding performance between the basalt fiber and the concrete matrix and promoting the improvement of the concrete strength.

Compared with the prior art, the present invention has the following advantages and technical effects:

(1) The present invention modifies the basalt fibers before adding them to concrete, thereby avoiding the problem of uneven dispersion of the basalt fibers in the concrete and agglomeration of the concrete fibers inside the concrete, thereby improving the mechanical properties and durability of the concrete.

(2) The basalt fiber reinforced concrete prepared by the present invention has a 28d compressive strength of ≥46.5MPa and a 56d compressive strength of ≥51.2MPa, which solves the problem of low late strength of basalt fiber reinforced concrete and improves the durability of concrete.

(3) The basalt fiber reinforced concrete prepared by the present invention has a 28d splitting strength of ≥4.0 MPa and a crack resistance grade of L-III, which solves the problem of easy cracking of basalt fiber concrete.

DETAILED DESCRIPTION

Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope 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 described 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.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

The room temperature in the present invention refers to 25±2°C.

In the embodiment of the present invention, each raw material can be purchased, wherein the fly ash is Grade I fly ash of Guodian Heli Thermal Power Company; the cement is PO 42.5 grade ordinary Portland cement purchased from Hunan Xindingli New Material Technology Co., Ltd.; the particle size of the pebbles is 10-20 mm; the river sand is natural river sand with a fineness modulus of 2.5-3.0 mm purchased from a sand mining plant in Hunan; the water reducer is ROCK-280 type polycarboxylic acid high-performance water reducer purchased from Wuhan Sanyuan Special Building Materials Co., Ltd.; the water is tap water; the basalt fiber is purchased from Hunan Bangbei Basalt Co., Ltd., and its single fiber tensile strength is 2.25×10 ³ MPa.

Example 1

Preparation of modified basalt fiber:

a. Add 100 mL of sodium chloride solution (mass fraction 15%) into a beaker, add 5 g of basalt fiber (length 10 mm, diameter 15±2 μm), heat from room temperature to 60°C at a heating rate of 2°C/min for 4 min, then heat to 95°C at a heating rate of 4°C/min, and keep warm for 2 min to obtain solution A. Seal the beaker during the heating process;

b. Add 3 g of sodium dodecylbenzene sulfonate and 5 mL of dimethylformamide to solution A, perform ultrasonic treatment, the ultrasonic power is 280 W, stir while performing ultrasonic treatment, the stirring rate is 120 r/min, take out the basalt fiber, dry it, and obtain modified basalt fiber.

The preparation method of basalt fiber reinforced concrete is as follows:

(1) 350 parts of pebbles, 240 parts of river sand, 85 parts of fly ash, 28 parts of volcanic ash and 250 parts of cement are mixed and stirred uniformly to obtain a mixture;

(2) Add 15 parts of modified basalt fiber to the mixture, stir at a rate of 850 r/min for 3 min, add 15 parts of water reducer (ROCK-280 polycarboxylic acid high performance water reducer, the same below) and 140 parts of water, first slowly stir at a rate of 400 r/min for 12 min, and then quickly stir at a rate of 750 r/min for 4 min to obtain basalt fiber reinforced concrete.

Take any five samples of the basalt fiber reinforced concrete prepared in this embodiment, weigh them respectively, put the samples into a blast drying oven for drying, weigh them after drying, and finally obtain the mass fractions of basalt fiber in the five samples in the total mass of the single sample: 1.30%, 1.29%, 1.26%, 1.31%, and 1.28%, respectively. It can be seen that the basalt fiber is dispersed more evenly in the concrete.

Example 2

Preparation of modified basalt fiber:

a. Add 100 mL of sodium chloride solution (mass fraction 15%) into a beaker, add 5 g of basalt fiber (length 10 mm, diameter 15±2 μm), heat from room temperature to 70°C at a heating rate of 3°C/min for 3 min, then heat to 100°C at a heating rate of 5°C/min, and keep warm for 1 min to obtain solution A. Seal the beaker during the heating process;

b. Add 5 g of sodium dodecylbenzene sulfonate and 15 mL of dimethylformamide to solution A, perform ultrasonic treatment, the ultrasonic power is 300 W, stir while performing ultrasonic treatment, the stirring rate is 100 r/min, take out the basalt fiber, dry it, and obtain modified basalt fiber.

The preparation method of basalt fiber reinforced concrete is as follows:

(1) 420 parts of pebbles, 220 parts of river sand, 90 parts of fly ash, 25 parts of volcanic ash and 240 parts of cement are mixed and stirred uniformly to obtain a mixture;

(2) Add 10 parts of modified basalt fiber to the mixture, stir at a rate of 800 r/min for 3 min, add 20 parts of water reducer and 130 parts of water, first slowly stir at a rate of 300 r/min for 15 min, and then quickly stir at a rate of 700 r/min for 5 min to obtain basalt fiber reinforced concrete.

Example 3

Preparation of modified basalt fiber:

a. Add 100 mL of sodium chloride solution (mass fraction 20%) into a beaker, add 5 g of basalt fiber (length 20 mm, diameter 15±2 μm), heat from room temperature to 50°C at a heating rate of 1°C/min for 5 min, then heat to 90°C at a heating rate of 3°C/min, and keep warm for 3 min to obtain solution A. Seal the beaker during the heating process;

b. Add 3 g of sodium dodecylbenzene sulfonate and 10 mL of dimethylformamide to solution A, perform ultrasonic treatment, the ultrasonic power is 250 W, stir while performing ultrasonic treatment, the stirring rate is 150 r/min, take out the basalt fiber, dry it, and obtain modified basalt fiber.

The preparation method of basalt fiber reinforced concrete is as follows:

(1) 480 parts of pebbles, 200 parts of river sand, 80 parts of fly ash, 25 parts of volcanic ash and 260 parts of cement were mixed and stirred uniformly to obtain a mixture;

(2) Add 20 parts of modified basalt fiber to the mixture, stir at a rate of 800 r/min for 3 min, add 8 parts of water reducer and 130 parts of water, first slowly stir at a rate of 500 r/min for 10 min, and then quickly stir at a rate of 850 r/min for 3 min to obtain basalt fiber reinforced concrete.

Example 4

The preparation method of modified basalt fiber is the same as that in Example 1.

The preparation method of basalt fiber reinforced concrete is as follows:

(1) 300 parts of pebbles, 250 parts of river sand, 85 parts of fly ash, 30 parts of volcanic ash and 240 parts of cement are mixed and stirred uniformly to obtain a mixture;

(2) Add 10 parts of modified basalt fiber to the mixture, stir at a rate of 850 r/min for 3 min, add 15 parts of water reducer and 150 parts of water, first slowly stir at a rate of 400 r/min for 12 min, and then quickly stir at a rate of 700 r/min for 3 min to obtain basalt fiber reinforced concrete.

Comparative Example 1

The same as Example 1, except that an equal amount of basalt fibers is directly added.

Take any 5 samples of the basalt fiber reinforced concrete prepared in this comparative example, weigh them separately, put the samples into a blast drying oven for drying, weigh their masses after drying, and finally obtain the mass fractions of basalt fiber in the five samples in the total mass of the single sample: 1.28%, 0.12%, 0.00%, 0.25%, and 0.31%, respectively. It can be seen that the basalt fiber is unevenly dispersed in the concrete.

Comparative Example 2

The same as Example 1, except that the modified basalt fiber is prepared as follows:

5 g of basalt fiber (length 10 mm, diameter 15±2 μm) was mixed with 3 g of sodium dodecylbenzene sulfonate and 5 mL of dimethylformamide, and ultrasonically treated at an ultrasonic power of 280 W. Stirring was performed while ultrasonically treating at a stirring rate of 120 r/min. The basalt fiber was taken out and dried to obtain modified basalt fiber.

Comparative Example 3

The same as Example 1, except that the modified basalt fiber is prepared as follows:

Add 100 mL of sodium chloride solution (mass fraction of 15%) into a beaker, add 5 g of basalt fiber (length 10 mm, diameter 15±2 μm), heat from room temperature to 60°C at a heating rate of 2°C/min and keep warm for 4 minutes, then heat to 95°C at a heating rate of 4°C/min and keep warm for 2 minutes. During the heating process, seal the beaker to obtain solution A, take out the basalt fiber, and dry it to obtain modified basalt fiber.

Comparative Example 4

The same as Example 1, except that in the preparation method of basalt fiber reinforced concrete, after adding the water reducer and water, stirring is directly performed at a speed of 750 r/min for 16 min.

The compressive strength, flexural strength, splitting strength and elastic modulus of the basalt fiber reinforced concrete of each embodiment and each comparative example were tested according to GB/T 50081 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", the crack resistance grade was evaluated according to GB-50010- "Code for Design of Concrete Structures", and the crack resistance grade was tested according to GB/T 50082 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", and the results are shown in Table 1. Comparative Example 5 in Table 1 is the same as Example 1, except that no modified basalt fiber is added.

Table 1

As can be seen from Table 1, the concrete of Examples 1-4 can meet the requirements in terms of 28d compressive strength, 28d flexural strength, 28d splitting strength, 28d elastic modulus and crack resistance grade technical indicators, and overcome the defects of low late strength and easy cracking of basalt fiber concrete. The concrete of Comparative Example 1 can meet the requirements in terms of 28d compressive strength, 28d flexural strength, 28d elastic modulus and crack resistance grade technical indicators, but the 28d splitting strength cannot meet the requirements, and the 56d compressive strength of Comparative Example 1 after adding basalt fiber is lower than the 56d compressive strength of the concrete of Comparative Example 5, which confirms that the addition of basalt fiber will reduce the late compressive strength of concrete; the concrete of Comparative Example 5 does not meet the requirements in terms of 28d compressive strength, 28d flexural strength, 28d splitting strength and crack resistance grade technical indicators.

The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (5)

1. A basalt fiber reinforced concrete, characterized in that it comprises the following raw materials in parts by weight: 80-90 parts of fly ash, 25-30 parts of volcanic ash, 240-260 parts of cement, 10-20 parts of modified basalt fiber, 300-480 parts of pebbles, 200-260 parts of river sand, 8-20 parts of water reducer and 130-150 parts of water; The preparation method of the modified basalt fiber is as follows: a. Place basalt fiber in sodium chloride solution, heat to 50-70℃ and keep warm for 3-5min, then heat to 90-100℃ and keep warm for 1-3min to obtain solution A; b. adding sodium dodecylbenzene sulfonate and dimethylformamide to the solution A, performing ultrasonic treatment while stirring, taking out the basalt fiber, and drying to obtain modified basalt fiber; In step a, the temperature is increased to 50-70°C at a heating rate of 1-3°C/min, and the temperature is increased to 90-100°C at a heating rate of 3-5°C/min; In step b, the mass volume ratio of sodium dodecylbenzenesulfonate to the solution A is (3-5) g: 100 mL; the volume ratio of dimethylformamide to the solution A is 0.5-1.5: 10; In step b, the stirring rate is 100-150 r/min; In step b, the ultrasonic power is 250-300W. 2. The basalt fiber reinforced concrete according to claim 1, characterized in that it comprises the following raw materials in parts by weight: 80-85 parts of fly ash, 25-28 parts of volcanic ash, 240-250 parts of cement, 10-15 parts of modified basalt fiber, 350-420 parts of pebbles, 220-240 parts of river sand, 8-15 parts of water reducer and 130-140 parts of water. 3. The basalt fiber reinforced concrete according to claim 1, characterized in that the water reducer is a polycarboxylic acid water reducer, and its water reduction rate is ≥25%. 4. A method for preparing the basalt fiber reinforced concrete according to any one of claims 1 to 3, characterized in that it comprises the following steps: (1) mixing pebbles, river sand, fly ash, volcanic ash and cement, and stirring evenly to obtain a mixture; (2) Adding modified basalt fiber to the mixture, stirring evenly, adding a water reducer and water, and continuing to stir evenly to obtain basalt fiber reinforced concrete. 5. The preparation method according to claim 4 is characterized in that, in step (2), after adding the modified basalt fiber, the stirring rate is 800-900r/min; after adding the water reducer and water, the stirring refers to first slow stirring and then fast stirring; the slow stirring time is 10-15min, and the rotation speed is 300-500r/min; the fast stirring time is 3-5min, and the rotation speed is 700-850r/min.