Cement-denitrification and dust removal product improved red clay filler and its preparation method and application

Abstract

The present application belongs to the field of roadbed filler technology and specifically provides a cement-denitrification and dust removal product-improved red clay filler, comprising the following components by mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance red clay. This application addresses the problem that red clay alone has poor physical properties as a roadbed filler. The application utilizes denitrification and dust removal products and cement to improve red clay, thereby obtaining good physical properties that meet the requirements for roadbed use. The application also provides a preparation method and application of a cement-denitrification and dust removal product-improved red clay filler.

Description

Technical Field

[0001] The present application relates to the technical field of road fillers, and in particular to a cement-denitrification and dust removal product improved red clay filler, and a preparation method and application thereof. Background Art

[0002] Red clay is a highly plastic, reddish-brown or brownish-yellow clay formed by the weathering and laterization of carbonate rocks. Red clay is a special type of clay characterized by poor physical properties, including high dispersibility, a high porosity, a high natural water content, strong structure, extreme water swelling, and poor water stability.

[0003] During the roadbed paving process, for the convenience of construction, soil is generally taken on-site as the roadbed filler. When constructing in red clay areas, due to the poor physical properties of red clay, if it is used directly as filler, it is very easy to slip and form obvious tensile cracks during the dry-wet alternation process, affecting the service life of the roadbed.

[0004] Therefore, it is necessary to provide a cement-denitrification and dust removal product improved red clay filler and its preparation method and application to solve the problems raised in the above background technology. Summary of the Invention

[0005] The present application provides a cement-denitrification and dust removal product improved red clay filler and its preparation method and application. To address the problem that red clay alone has poor physical properties as a roadbed filler, the red clay is improved using denitrification and dust removal products and cement to obtain good physical properties that meet the use requirements of road subgrades.

[0006] In order to solve the above technical problems, the technical solution of this application is:

[0007] A cement-denitrification and dust removal product improved red clay filler comprises the following components in percentage by mass: (0.5-1)% of cement, (8-11)% of denitrification and dust removal product, and the balance of red clay.

[0008] Preferably, the content of montmorillonite in the red clay is not higher than 9%.

[0009] Preferably, it includes the following components in percentage by mass: 1% cement, 10% denitrification and dust removal product, and the remainder red clay.

[0010] Preferably, the denitrification and dust removal product is the substance obtained by removing nitrogen oxides from the flue gas generated by a cement production line.

[0011] Preferably, the denitrification and dust removal product includes the following components in weight percentage: 25.5% calcium hydroxide, 41.5% calcium carbonate, 27.5% calcium sulfate, 1.8% sodium chloride, 1.5% potassium chloride, 1% magnesium chloride and 1.2% silicate.

[0012] The present application also provides a method for preparing the above-mentioned cement-denitrification and dust removal product improved red clay filler, comprising the following steps:

[0013] Grind the denitrification and dust removal products and filter them;

[0014] Crush, filter and dry the red clay;

[0015] A mixture is prepared, wherein the mixture comprises the following components by mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance red clay;

[0016] The mixture is placed in a container, stirred evenly, and then water is added to the target moisture content, and the mixture is sealed for more than 7 hours to complete the preparation.

[0017] The present application also provides the application of the above-mentioned cement-denitrification and dust removal product to improve the red clay filler, which is used as a roadbed filler.

[0018] The beneficial effects of this application are:

[0019] (1) Using denitrification and dust removal products and cement to improve red clay, so that it has good physical properties and meets the requirements for road subgrade use;

[0020] (2) This improvement can reduce the use of raw materials, save production costs, and reduce the overall cost of the product;

[0021] (3) Red clay is a common natural material widely distributed in many areas. The use of improved red clay can reduce the demand for other scarce or environmentally sensitive materials, reduce environmental impact, promote the sustainable use and development of local resources, enhance the sustainability of economic development, and has good market development prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Represents the relationship curve between the loading times and the maximum strain value of each group of samples;

[0023] Figure 2 Represents the relationship curve between the number of loading times and the minimum strain value of each group of specimens;

[0024] Figure 3 The relationship curve between the number of loading times and the dynamic elastic modulus of each group of samples is shown;

[0025] Figure 4The relationship curve between the number of loading times and the damping ratio of each group of samples is shown;

[0026] Figure 5 Represents the relationship curve between loading times and pore pressure of each group of samples. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0028] The present application provides a cement-denitrification and dust removal product improved red clay filler, comprising the following components in mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance red clay.

[0029] Preferably, the cement-denitrification and dust removal product improved red clay filler includes the following components in mass percentage: 1% cement, 10% denitrification and dust removal product, and the balance red clay.

[0030] The content of montmorillonite in red clay is not higher than 9%. Montmorillonite has an important influence on the swelling and shrinkage of red clay. The swelling and shrinkage of red clay with high montmorillonite content will be more unfavorable, so it needs to be controlled.

[0031] The denitrification and dust removal product is the product after nitrogen oxides are removed from the flue gas generated by the cement production line. Testing has revealed that the denitrification and dust removal product contains the following components, by weight: 25.5% calcium hydroxide, 41.5% calcium carbonate, 27.5% calcium sulfate, 1.8% sodium chloride, 1.5% potassium chloride, 1% magnesium chloride, and 1.2% silicate.

[0032] The main components of denitrification and dust removal products are calcium carbonate, calcium sulfate and calcium hydroxide. The Ca(OH)2 in the components dissolves in water to form an alkaline solution, which plays a low-alkaline stimulation role in improving the strength of cement base, cement mortar and concrete.

[0033] CaSO₄ is dehydrated gypsum, which forms mature gypsum upon contact with water, regulating the hydration and setting rate of cement. Furthermore, under certain conditions, during the hydration process, ettringite (AFt) or monosulfurized calcium sulfoaluminate hydrate crystals (AFm) can form, which also contribute to strength. However, excessive gypsum can cause significant volume changes in concrete during hardening, leading to cracks. Furthermore, both Ca(OH)₂ crystals and gypsum compete for water during the hydration process. Therefore, to achieve satisfactory strength after hardening, the water-cement ratio may need to be increased.

[0034] The main components of cement include CaO, SiO2, Al2O3, Fe2O3, in addition to MgO, K2O, Na2O, SO3, etc. The main mineral components of cement clinker are tricalcium silicate (3CaO·SiO3, abbreviated as C3S), dicalcium silicate (2CaO·SiO2, abbreviated as C2S), tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3, abbreviated as C4AF), and tricalcium aluminate (3CaO·Al2O3, abbreviated as C3A).

[0035] The main reactions that occur when cement hydrates with water are:

[0036] C3S+H→CSH(calcium silicate hydrate)+CH(calcium hydroxide);

[0037] C2S+H→CS-H+CH;

[0038] C3A+H→C3AH6 (tricalcium aluminate hydrate);

[0039] C4AF+H→C3AH6+CFH (monocalcium ferrite hydrate).

[0040] Calcium silicate hydrate (CSH) and calcium hydroxide (CH)·CSH, formed by the hydration of tricalcium aluminate or dicalcium silicate, are insoluble in water and immediately precipitate as colloidal particles, gradually coagulating to form a CSH gel. The CH concentration in the solution quickly reaches supersaturation, precipitating as hexagonal plate-like crystals. Calcium aluminate hydrate is a cubic crystal. In a saturated calcium hydroxide solution, a portion of it can further react with calcium hydroxide to form hexagonal tetracalcium aluminate hydrate.

[0041] Because cement often contains a small amount of gypsum, the resulting calcium aluminate hydrate reacts with the gypsum to form high-sulfur calcium sulfoaluminate hydrate (3CaO·Al2O3·3CaSO4·32H2O) needle-shaped crystals, known as ettringite (AFt). Once the gypsum is completely consumed, a portion of it transforms into monosulfur calcium sulfoaluminate hydrate crystals (AFm). AFt typically forms in large quantities within 24 hours of adding water to the cement, then gradually transforms into AFm.

[0042] Therefore, from the above chemical composition analysis, it can be seen that the main components of denitrification and dust removal by-products, Ca(OH)2, CaCO3 and CaSO4, will definitely participate in the hydration reaction when they meet water after mixing with cement. The generated hydration products have strong cementing properties and good water stability. They can fill the pores of red clay, improve the pore structure, increase the adhesion between soil particles, and improve the dynamic characteristics of red clay.

[0043] The present application also provides a method for preparing the above-mentioned cement-denitrification and dust removal product improved red clay filler, comprising the following steps:

[0044] Grind the denitrification and dust removal products and filter them;

[0045] Crush, filter and dry the red clay;

[0046] A mixture is prepared, wherein the mixture comprises the following components by mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance red clay;

[0047] The mixture is placed in a container, stirred evenly, and then water is added to the target moisture content, and the mixture is sealed for more than 7 hours to complete the preparation.

[0048] This application also provides the application of the above-mentioned cement-denitrification and dust removal product-improved red clay filler for roadbed filling. The construction process of the roadbed filling is as follows: the roadbed filler is spread and leveled, and a full-width, longitudinal, horizontal layered filling and compaction method is adopted to form the roadbed.

[0049] Direct sampling in red clay areas and improving it for use as roadbed material facilitates access and reduces the use of other fillers, lowering construction costs. Denitrification and dust removal products are also used as modifiers, enabling waste recycling and meeting the concept of sustainable development.

[0050] In order to verify the performance of the improved red clay filler provided in this application, the following comparative test was set up:

[0051] The comparative example is red clay soil;

[0052] Example 1: Red clay soil was improved by using 0.5% cement and 8% denitrification and dust removal products;

[0053] Example 2: Red clay soil was improved by using 0.5% cement and 9% denitrification and dust removal products;

[0054] Example 3: Red clay soil was improved by using 0.5% cement and 10% denitrification and dust removal products;

[0055] Example 4: Red clay soil was improved using 0.5% cement and 11% denitrification and dust removal products;

[0056] Example 5: Red clay soil was improved by using 1% cement and 8% denitrification and dust removal products;

[0057] Example 6: Red clay soil was improved by using 1% cement and 9% denitrification and dust removal products;

[0058] Example 7: Red clay soil was improved by using 1% cement and 10% denitrification and dust removal products;

[0059] Example 8: Red clay soil was improved by using 1% cement and 11% denitrification and dust removal products.

[0060] Among them, the red clay soil is taken from the Jinqu Basin in western Zhejiang.

[0061] Dynamic triaxial tests were performed on each group of samples in Examples 1-8 and the comparative example to explore the relationship between the number of loading times N and the maximum strain value. The relationship diagram obtained is as follows: Figure 1 As shown. Figure 1 It can be found that with the increase in the number of loading times, the maximum strain values of all groups show an increase at first and then slow down to reach stability. However, the specific performance of each group is different: in the control group, when the number of loading times is small, the maximum strain does not increase rapidly. After the number of loading times increases to a certain extent, the strain value finally stabilizes at about 2.4. In Example 5, as the number of loading times increases, the trend of change of its strain value is the slowest. In Example 8, as the number of loading times increases, the strain value stabilizes at about 0.1, which is the group with the smallest strain value among all groups.

[0062] Dynamic triaxial tests were performed on each group of samples in Examples 1-8 and the comparative example to explore the relationship between the number of loading times N and the minimum strain value. The relationship diagram obtained is as follows: Figure 2 As shown. Figure 2 It can be found that with the increase of the number of loading times, the minimum strain values of all groups show an increase at first and then slow down to reach stability, and the distribution and trend of each group of curves are similar to the distribution of the maximum strain value curve. In the comparative example, when the number of loading times is small, the maximum strain does not increase rapidly. After the number of loading times increases to a certain extent, the strain value eventually stabilizes at about 2.3. In Example 5, with the increase of the number of loading times, the trend of change of its strain value is the slowest, which is similar to the trend of the maximum strain value change curve. In Example 8, with the increase of the number of loading times, the strain value stabilizes at about 0.04, which is the group with the smallest strain value in all groups. In Example 7, the minimum strain value appears negative when the number of loading times is less than 5 times.

[0063] Dynamic triaxial tests were performed on each group of samples of Examples 1-8 and the comparative example to explore the relationship between the number of loading times N and the dynamic elastic modulus. The relationship diagram obtained is as follows: Figure 3 As shown. Figure 3 As can be seen, as the number of loading times increases, the curves of each group basically conform to the general trend of first rising steeply and then gradually stabilizing. The difference is that there are large differences in the values of the curves of each group after stabilization. In Example 1, as the number of loading times increases, the dynamic elastic modulus value growth curve trend is relatively gentle, and the final dynamic elastic modulus value stabilizes at around 52.3 MPa. This group has the largest dynamic elastic modulus value after stabilization among all groups; in Example 2, as the number of loading times increases, the dynamic elastic modulus value after stabilization is the smallest among all groups, stabilizing at around 19.4 MPa; in the comparative example, the final stable value of the dynamic elastic modulus after stabilization is 20.2 MPa.

[0064] Dynamic triaxial tests were performed on each group of samples of Examples 1-8 and the comparative example to explore the relationship between the number of loading times N and the damping ratio. The relationship diagram obtained is shown in FIG. Figure 4 As shown. Figure 4 As can be seen from the figure, as the number of loading cycles increases, the damping ratio of each group of samples generally shows a trend of first increasing sharply and then slowly stabilizing. The damping ratio of the comparative example ultimately stabilizes at around 0.042; in Example 8, the damping ratio is the smallest among all groups, ultimately stabilizing at around 0.02.

[0065] Dynamic triaxial tests were performed on each group of samples in Examples 1-8 and the comparative example to explore the relationship between the number of loading times N and the pore pressure. The relationship diagram obtained is shown in FIG. Figure 5 As shown. Figure 5 As can be seen, the pore pressure curves for the comparative example differ significantly from those for Examples 1-8. In the comparative example, the pore pressure rises significantly after more than five loading cycles, eventually stabilizing at around 4.4 kPa as the number of loading cycles increases, a value far greater than that of the other groups of samples. In Examples 1-8, the pore pressures of each group follow roughly the same trend as the number of loading cycles, ultimately converging between 0.05 and 0.40 kPa, significantly lower than those of the comparative example. In particular, the pore pressures of Examples 3 and 4 exhibit negative values at certain loading cycles.

[0066] From the above tests, it can be seen that the maximum strain and minimum strain of Examples 4, 6, and 7 after loading stabilization are larger in all groups, but not extremely large. The stable values of the maximum strain and the minimum strain are generally smaller than those of the comparative example, and the stable value of the dynamic elastic modulus is significantly improved compared with the comparative example as a whole.

[0067] In Example 1, the dynamic elastic modulus value after loading reaches stability is stable at about 52.3MPa. This group has the largest dynamic elastic modulus value after stability among all groups. The reason is that the hydration products of cement and denitrification and dust removal by-products have strong cementing properties, which improve the adhesion between particles and can be filled in the pores of the soil, making the soil more uniform and dense, thereby increasing the dynamic elastic modulus and reducing deformation. Overall, the damping ratio of Examples 1-8 after loading stability is smaller than that of the comparative example. The reason is that the hydration products of cement and denitrification and dust removal by-products fill the pores of the soil, and the particles are fully engaged, which greatly reduces the probability of sliding and relative dislocation between particles, thereby reducing energy dissipation. Compared with the comparative example, the addition of cement and denitrification and dust removal by-products in Examples 1-8 improves the pore structure, greatly reduces the complexity of the pores, and thus reduces the pore pressure. The maximum strain value and the minimum strain value of Example 7 are large, but not extremely large. The dynamic elastic modulus value is 41.7 MPa after stabilization, which is at a higher value compared with other groups. The damping ratio value is stable at 0.044, which is not much different from the damping ratio values of other groups after stabilization. The pore pressure value after stabilization is 0.07 kPa, which is basically in the middle of the pore pressure values after stabilization in all comparative examples. The improved red clay improves the CBR (California Bearing Ratio) value. At the same time, the expansion rate performs well and can meet the requirements of various indicators of the roadbed.

[0068] The sample in Example 7 was applied to the K50+400-K50+540 section of the Kecheng main line subgrade fill. After testing, the improved soil in this section had a liquid limit of 40.0%, a plastic limit of 18.2%, a plastic limit index of 21.8, an optimum moisture content of 10.7%, and a maximum dry density of 1.90 g / cm 3 .

[0069] The compaction test results all meet the requirements of the design drawings:

[0070] Table 1 Improved soil compaction test

[0071] Serial number Pile number Offset Test results Result determination 1 K50+635 Left 3.4 91.6 qualified 2 K50+665 Right 3.8 91.2 qualified 3 K50+690 Left 2.3 91.8 qualified 4 K50+710 Right 4.1 91.4 qualified

[0072] Test conclusion: After testing, the compaction test results of this road section meet the requirements of the design drawings (≥90%).

[0073] Table 2 The fifth rolling compaction test

[0074] Serial number Pile number Offset Test results Result determination 1 K50+630 Left 2.9 93.6 qualified 2 K50+650 Right 3.6 93.4 qualified 3 K50+670 Left 4.3 93.9 qualified 4 K50+700 Right 3.8 93.5 qualified

[0075] Test conclusion: After testing, the compaction test results of this road section meet the requirements of the design drawings (≥93%).

[0076] Table 3 The 7th rolling compaction test

[0077] Serial number Pile number Offset Test results Result determination 1 K50+645 Right 2.6 96.4 qualified 2 K50+665 Left 3.3 96.6 qualified 3 K50+685 Right 3.7 96.5 qualified 4 K50+705 Left 3.0 936.6 qualified

[0078] Test conclusion: After testing, the compaction test results of this road section meet the requirements of the design drawings (≥96%).

[0079] This indicates that the cement-denitrification and dust removal product-modified red clay filler provided in this application can be well applied to roadbed fillers and meet the relevant design requirements of roadbed fillers.

[0080] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A cement-denitrification and dust removal product improved red clay filler, characterized in that: The composition comprises the following components by mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance is red clay; the denitrification and dust removal product comprises the following components by weight percentage: 25.5% calcium hydroxide, 41.5% calcium carbonate, 27.5% calcium sulfate, 1.8% sodium chloride, 1.5% potassium chloride, 1% magnesium chloride and 1.2% silicate.

2. The cement-denitrification and dust removal product improved red clay filler according to claim 1, characterized in that: The content of montmorillonite in red clay is no more than 9%.

3. The cement-denitrification and dust removal product improved red clay filler according to claim 1, characterized in that: The composition includes the following components by mass percentage: 1% cement, 10% denitrification and dust removal products, and the balance red clay.

4. The cement-denitrification and dust removal product improved red clay filler according to claim 1, characterized in that: Denitrification and dust removal products are substances produced by removing nitrogen oxides from the flue gas generated by the cement production line.

5. A method for preparing the cement-denitrification and dust removal product improved red clay filler according to any one of claims 1 to 4, characterized in that: The steps include: Grind the denitrification and dust removal products and filter them; Crush, filter and dry the red clay; A mixture is prepared, wherein the mixture includes the following components by mass percentage: (0.5-1)% cement, (8-11)% denitrification and dust removal product, and the balance red clay; The mixture is placed in a container, stirred evenly, and then water is added to the target moisture content, and the mixture is sealed for more than 7 hours to complete the preparation.

6. An application of cement-denitrification and dust removal product modified red clay filler according to any one of claims 1 to 4, characterized in that: Used for roadbed filling.

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