Basalt fiber modified graphite tailing road concrete with fatigue bending resistance and preparation method of basalt fiber modified graphite tailing road concrete

Abstract

The invention discloses basalt fiber modified graphite tailing road concrete with fatigue bending resistance and a preparation method of the basalt fiber modified graphite tailing road concrete, and belongs to the field of road concrete and preparation thereof, graphite tailing sand is used for replacing part of natural river sand, solid waste is recycled and ecologically utilized, basalt fibers are doped, the breaking strength is remarkably improved, and the fatigue life is remarkably prolonged. The concrete is prepared from the following components in parts by weight: 43 to 45 parts of coarse aggregate, 12 to 22 parts of natural river sand, 0 to 9 parts of graphite tailing sand, 10 to 12 parts of cement, 0.08 to 0.2 part of basalt fiber, 5 to 7 parts of water and 0.015 to 0.15 part of water reducing agent. Uniformly mixing and stirring the weighed water and water reducing agent to form a mixed solution; stirring the dried graphite tailing sand and the natural river sand to form uniformly dispersed fine aggregate, then doping coarse aggregate, and uniformly stirring; putting the cement and the basalt fiber into the mixed aggregate, and uniformly mixing; and putting the mixed solution into the prepared dry material in two times, and uniformly stirring to obtain the product.

Description

Technical Field

[0001] The present invention belongs to the technical field of road concrete and its preparation, and particularly relates to a fiber-modified road concrete and a preparation method thereof. Background Art

[0002] With the acceleration of the urbanization process, a large number of people pour into cities, resulting in a continuous surge in traffic volume. When facing frequent dynamic loads and environmental factors, traditional concrete often shows fatigue damage and cracks, thus affecting the safety and service life of roads. Therefore, developing new road concrete to enhance its fatigue resistance has become an urgent problem to be solved.

[0003] At the same time, with the acceleration of the global industrialization process, the generation of solid waste has increased significantly. Especially with the growth of the demand for battery materials, lubricants and other high-tech products, the mining of graphite ore has gradually increased, resulting in a large amount of graphite tailings. Graphite tailings not only occupy land resources, but also pollute water and soil, causing great pressure on the environment. To promote the concept of sustainable development, the research on reducing the use of non-renewable resources and the efficient resource utilization of solid waste has been increasingly emphasized, which has further promoted the application and development of graphite tailings in the fields of construction, road engineering, etc.

[0004] Fibers have been proven to be effective in improving the fatigue resistance of concrete. Fibers form a three-dimensional network structure in concrete, which can effectively limit the expansion of cracks and play a "bridging" role, thereby improving the overall stability of concrete. At the same time, the introduction of fibers enhances the toughness and tensile strength of concrete, enabling it to more effectively absorb and disperse stress under repeated loads, contributing to delaying the formation and expansion of cracks and reducing the risk of fatigue brittle failure. In addition, fibers can delay the process of fatigue failure by absorbing part of the energy and reducing stress concentration, thereby extending the service life of concrete under multiple loads.

[0005] Basalt fiber has been widely used in the research of crack resistance, toughness improvement and durability enhancement of concrete due to its excellent green environmental protection, mechanical properties and stability. Graphite tailings sand has a volcanic activation effect and is mainly composed of chemical elements such as CaO, SiO2, Al2O3, Fe2O3, SO3, MgO, K2O. At different 2θ angles, it exhibits the main crystal structure characteristics of silica, gypsum, dolomite and calcite, and most of the graphite tailings sand particles have rough surfaces, which provides a solid foundation for replacing river sand with graphite tailings sand. Existing research shows that graphite tailings sand has varying degrees of enhancement effects on the durability of concrete such as mechanical strength, shrinkage deformation and freeze-thaw resistance. Using basalt fiber to modify graphite tailings sand concrete can reduce costs and be environmentally friendly while enhancing the road performance of concrete. However, there is currently no solution for preparing road-use concrete with basalt fiber-modified graphite tailings sand to enhance the anti-fatigue bending performance of concrete. Summary of the Invention

[0006] The purpose of the present invention is to provide a road-use concrete with basalt fiber-modified graphite tailings sand having fatigue-resistant bending performance and a preparation method thereof. Using graphite tailings sand to replace part of natural river sand to prepare concrete not only enables the resource-based and ecological utilization of solid waste graphite tailings sand, reduces the use of non-renewable resources, but also improves the anti-fatigue performance of concrete while enhancing its basic mechanical properties. When basalt fiber is incorporated into this concrete, both the flexural strength and the fatigue life under different stress ratios are significantly improved.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A road-use concrete with basalt fiber-modified graphite tailings sand having fatigue-resistant bending performance, characterized in that the weight part composition of the concrete is: 43 - 45 parts of coarse aggregate, 12 - 22 parts of natural river sand, 0 - 9 parts of graphite tailings sand, 10 - 12 parts of cement, 0.08 - 0.2 parts of basalt fiber, 5 - 7 parts of water, and 0.015 - 0.15 parts of water reducer.

[0009] For the above-mentioned road-use concrete with basalt fiber-modified graphite tailings sand having fatigue-resistant bending performance, the coarse aggregate is continuously graded gravel with a particle size of 5 - 25 mm; the natural river sand is medium sand; the cement is ordinary Portland cement with a strength grade of 42.5; the water reducer is polycarboxylate water reducer.

[0010] For the above-mentioned road-use concrete with basalt fiber-modified graphite tailings sand having fatigue-resistant bending performance, the graphite tailings sand is the graphite tailings produced in Yunshan Graphite Park, Luobei County, China, with a particle size between 10 um and 1 mm and a specific surface area of 10.87 m 2 / kg.

[0011] The above-mentioned basalt fiber-modified graphite tailings road concrete with fatigue-resistant bending performance, wherein the basalt fiber is micron-level short-cut fiber with a single-filament diameter of 15 μm and a length of 12 mm.

[0012] The preparation method of the above-mentioned basalt fiber-modified graphite tailings road concrete with fatigue-resistant bending performance comprises the following steps:

[0013] I. Weigh all water and water reducer by weight parts, mix them evenly to form a mixed solution.

[0014] II. Weigh dry graphite tailings sand and natural river sand by weight parts, stir them to form all fine aggregates with uniform dispersion, and then add coarse aggregates weighed by weight, and stir evenly to obtain mixed aggregates.

[0015] III. Put the cement and basalt fiber weighed by weight parts into the mixed aggregates prepared in step II, and mix them evenly to obtain dry materials.

[0016] IV. Put the mixed solution prepared in step I into the dry materials prepared in step III in two times, stir evenly, and what is obtained is the basalt fiber-modified graphite tailings road concrete.

[0017] The beneficial effects of the present invention are as follows:

[0018] First, by partially and equally replacing natural river sand with graphite tailings sand, it can effectively reduce the demand for the exploitation of natural river sand, make full use of local tailings resources, obtain materials locally, strengthen the comprehensive utilization of bulk solid wastes, relieve the pollution to the environment on the basis of saving material costs, and at the same time, the production cost of this concrete is relatively low, which can effectively reduce the stacking of tailings waste and promote the development of sustainable building materials, meeting the concept of green buildings.

[0019] Second, graphite tailings sand can exert pozzolanic activity to promote the bonding between fibers and cement paste, jointly reducing the bending stiffness degradation process. At the same time, basalt fiber plays a role in toughening and crack resistance to the cement paste, cross-connecting arbitrarily in the concrete to form a dense network structure, inhibiting the development of micro-cracks and delaying the generation of macro-cracks, and playing a role in dispersing the energy in the stress concentration area. The synergistic effect of the two makes the discreteness of the fatigue life the smallest, which is beneficial to further comprehensively improving the flexural strength and fatigue life of graphite tailings sand concrete.

[0020] Third, an appropriate amount of graphite tailings sand can promote the absorption of Al element, improve the chain length and strength of C-S-H gel, and further increase the total content of C-S-H gel, reduce the pores and micro-cracks at the ITZ, make the ITZ more dense, improve its elastic modulus and reduce the width. It further verifies that basalt fiber-modified graphite tailings concrete can improve the flexural mechanical properties and fatigue life of concrete, and promote the application of graphite tailings concrete in road engineering. Description of the Drawings

[0021] Figure 1 Physical photo during the flexural strength test of the concrete prepared by the method of the present invention;

[0022] Figure 2 Physical photo during the fatigue resistance test of the concrete prepared by the method of the present invention;

[0023] Figure 3 Statistical chart of the 28-day flexural strength data of the experimental specimens of the present invention; Detailed Description of the Invention Detailed Description of the Invention 1:

[0025] A basalt fiber modified graphite tailings road concrete with fatigue-resistant bending performance, which is simultaneously mixed with basalt fibers and graphite tailings sand; the weight fraction components of the concrete are: 43-45 parts of coarse aggregate, 12-22 parts of natural river sand, 0-9 parts of graphite tailings sand, 10-12 parts of cement, 0.08-0.2 parts of basalt fiber, 5-7 parts of water, and 0.015-0.15 parts of water reducing agent.

[0026] For the above-mentioned basalt fiber modified graphite tailings road concrete, the weight fraction ratio of basalt fiber to cement is 0.8%-1.6%. When the dosage of basalt fiber exceeds the upper limit of the above range, the fibers will be unevenly dispersed and easily agglomerate in the cement mortar, unable to play the modification role well, resulting in a significant reduction in the slump and mechanical properties of the concrete, not meeting the corresponding indicators. And the graphite tailings sand replaces 0%-40% of the original natural river sand.

[0027] For the above-mentioned basalt fiber modified graphite tailings road concrete with fatigue-resistant bending performance, the coarse aggregate is gravel with a continuous gradation of 5-25 mm in particle size; the natural river sand is medium sand; the cement is ordinary Portland cement with a strength grade of 42.5; the water reducing agent is polycarboxylate water reducing agent.

[0028] For the above-mentioned basalt fiber modified graphite tailings road concrete with fatigue-resistant bending performance, the graphite tailings sand is the graphite tailings produced by Yunshan Graphite Park in Luobei County, China, with a particle size between 10 um and 1 mm and a specific surface area of 10.87 m 2 / kg.

[0029] For the above-mentioned basalt fiber modified graphite tailings road concrete with fatigue-resistant bending performance, the basalt fiber is micron-sized short-cut fiber with a single filament diameter of 15 um and a length of 12 mm.

[0030] The preparation method of the above-mentioned basalt fiber modified graphite tailings road concrete with fatigue-resistant bending performance includes the following steps:

[0031] 1. Weigh all the water and water reducer according to the weight parts, mix them evenly to form a mixed solution.

[0032] 2. Stir the dried graphite tailings sand and natural river sand weighed according to the weight parts to form all the fine aggregates with uniform dispersion, and then add the coarse aggregates weighed by weight, and stir evenly to obtain the mixed aggregates.

[0033] 3. Put the cement and basalt fiber weighed according to the weight parts into the mixed aggregates prepared in step 2, and mix evenly to obtain the dry materials.

[0034] 4. Put the mixed solution prepared in step 1 into the dry materials prepared in step 3 in two batches, stir evenly, and what is obtained is the basalt fiber modified graphite tailings road concrete.

[0035] Example 1:

[0036] Flexural strength test: A total of 15 groups of specimens were made in this example. Among them, 1 group did not add any fibers and the substitution rate of graphite tailings sand was 0 as the control group, and 14 groups were used as the test groups. The weight fraction composition of the matrix ordinary concrete is: 43 - 45 parts of coarse aggregates, 12 - 22 parts of natural river sand, 10 - 12 parts of cement, 5 - 7 parts of water, and 0.015 - 0.15 parts of water reducer.

[0037] The flexural strength test was carried out on cuboids with side lengths of 100×100×400 mm. 6 specimens were made in each group. The test grouping is shown in Table 1 below. In Table 1, the values corresponding to the substitution rate of graphite tailings sand GT of 10% are 1.2 - 2.2 parts of ore sand and 10.8 - 19.8 parts of river sand; 20% corresponds to 2.4 - 4.4 parts of ore sand and 9.6 - 17.6 parts of river sand; 30% corresponds to 3.6 - 6.6 parts of ore sand and 8.4 - 15.4 parts of river sand; 40% corresponds to 4.8 - 8.8 parts of ore sand and 7.2 - 13.2 parts of river sand. The BF weight fraction corresponding to the weight fraction ratio of basalt fiber BF to cement of 0.8% is 0.08 - 0.096 parts; 1.6% corresponds to BF weight fraction of 0.16 - 0.192 parts.

[0038] Table 1

[0039]

[0040]

[0041] The 28-day flexural strength test results are as Figure 3 shown.

[0042] From the above Figure 3It can be seen that when the fiber content is constant, the flexural strength of the concrete also shows a trend of first increasing and then decreasing with the increase of the replacement rate of graphite tailings sand, and reaches the maximum value when the replacement rate of graphite tailings sand is 20% (i.e., 20% corresponds to 2.4 - 4.4 parts of ore sand and 9.6 - 17.6 parts of river sand). Compared with PC, the flexural strength of GT20BF0.1 and GT20BF0.2 increased by 19.10% and 3.53% respectively, while the flexural strength of GT40BF0.1 and GT40BF0.2 decreased by 0.48% and 4.17% respectively. It shows that adding basalt fibers with a weight ratio of 0.8% or using graphite tailings sand with a low replacement rate to replace natural river sand can help improve the flexural strength of the concrete. The improvement effect is more significant when the two are mixed, and the optimal mixing variable is GT20BF0.1. GT20BF0.1 corresponds to 2.4 - 4.4 parts of ore sand, 9.6 - 17.6 parts of river sand, and 0.08 - 0.096 parts of basalt fibers. Its static load flexural strength at 28 days can reach up to 5.30 MPa, which can maximize the anti-bending ability of the concrete.

[0043] Example 2:

[0044] Fatigue test: In this example, only specimens with 4 mix ratios were made, and the matrix concrete mix ratio was the same as that in Example 1.

[0045] In this example, the size and number of specimens made for each mix ratio were the same as those in Example 1.

[0046] In this example, the load wave of the fatigue load was a sine wave, the loading frequency was 5 Hz, and the stress levels S (S = S max / S0) were set to 0.6, 0.7, and 0.8 respectively, and the minimum bending fatigue load S min was set to 10% of S max (S min / S max = 0.1), that is, the fatigue characteristic value was 0.1.

[0047] The test results of the fatigue life of the concrete are shown in the following table:

[0048]

[0049] As can be seen from the above table, at the same stress level, appropriately adding graphite tailings sand to replace natural river sand can significantly extend the flexural fatigue life of concrete. For example, when the stress level is 0.6, the fatigue characteristic life of the GT20BF0 specimen is 60.44% higher than that of the PC specimen. When the weight fraction ratio of basalt fiber is 0.8%, as the replacement rate of graphite tailings sand increases from 0 to 20%, the fatigue life of concrete shows a gradually increasing trend under three stress levels and reaches the maximum value when the replacement rate of graphite tailings sand is 20%, that is, the fatigue life improvement effect of the GT20BF0.1 specimen is the most significant. When the stress level is 0.6, the fatigue characteristic life of the GT20BF0.1 specimen is 1.95 times higher than that of the GT0BF0.1 specimen. It shows that different dosages of basalt fiber and graphite tailings sand not only affect the flexural strength of concrete, but also have a positive correlation with the flexural fatigue life of concrete.

Claims

1. A basalt fiber modified graphite tailings road concrete with fatigue bending resistance, characterized in that The weight ratio of the concrete is as follows: 43-45 parts of coarse aggregate, 12-22 parts of natural river sand, 0-9 parts of graphite tailings sand, 10-12 parts of cement, 0.08-0.2 parts of basalt fiber, 5-7 parts of water, and 0.015-0.15 parts of water reducing agent.

2. The basalt fiber modified graphite tailings road concrete with fatigue bending resistance according to claim 1 is characterized in that The coarse aggregate is crushed stone with a particle size of 5-25 mm and continuous grading; the natural river sand is medium sand; the cement is ordinary Portland cement with a strength grade of 42.5; and the water reducer is a polycarboxylate water reducer.

3. The basalt fiber modified graphite tailings road concrete with fatigue bending resistance according to claim 1 or 2, characterized in that The graphite tailings sand is produced by Yunshan Graphite Park in Luobei County, China, with a particle size between 10um-1mm and a specific surface area of ​​10.87m 2 / kg.

4. According to the basalt fiber modified graphite tailings road concrete with fatigue bending resistance as described in claim 1 or 2, it is characterized in that The basalt fiber is a micron-grade short-cut fiber with a single fiber diameter of 15um and a length of 12mm.

5. The basalt fiber modified graphite tailings road concrete with fatigue bending resistance according to claim 1 or 2, characterized in that The weight composition of the concrete is: 44 parts of coarse aggregate, 17.2 parts of natural river sand, 4.3 parts of graphite tailings sand, 11.05 parts of cement, 0.088 parts of basalt fiber, 5.08 parts of water, and 0.07 parts of water reducer.

6. The basalt fiber modified graphite tailings road concrete with fatigue bending resistance according to claim 1 or 2, characterized in that The weight ratio of graphite tailings sand and river sand is 2.4-4.4 parts of ore sand and 9.6-17.6 parts of river sand.

7. The basalt fiber modified graphite tailings road concrete with fatigue bending resistance according to claim 6, characterized in that The weight ratio of graphite tailings, river sand and basalt fiber is 2.4-4.4 parts of graphite tailings, 9.6-17.6 parts of river sand and 0.08-0.096 parts of basalt fiber.

8. The method for preparing the basalt fiber modified graphite tailings road concrete with fatigue bending resistance as claimed in any one of claims 1 to 3, comprising the following steps:

1. Weigh all the water and water reducing agent by weight, mix them and stir them evenly to form a mixed solution; 2. Weigh dry graphite tailings sand and natural river sand by weight and stir them to form evenly dispersed fine aggregates, then add coarse aggregates weighed by weight and stir them evenly to obtain mixed aggregates; 3. Add the cement and basalt fiber weighed by weight into the mixed aggregate prepared in step 2, and mix them evenly to obtain dry material; 4. Add the mixed solution prepared in step 1 into the dry material prepared in step 3 twice and stir evenly.

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