Modified stone powder light soil as well as preparation method and application thereof

Abstract

The invention provides modified stone powder light soil as well as a preparation method and application thereof, and belongs to the technical field of building materials. The preparation method comprises the following steps: mixing hydroxylated multi-walled carbon nanotubes and single-stranded desoxyribonucleic acid to form a suspension; adding a foaming agent into the suspension to generate foam; mixing 10 parts by mass of stone powder, 40 parts by mass of cement, 20 parts by mass of sand and 5.5 parts by mass of water, uniformly stirring, finally adding 0.32 part by mass of a water reducing agent and 5.5 parts by mass of water, and stirring to form slurry; adding the foam into the slurry, uniformly stirring, and curing and forming to complete the preparation of the modified stone powder light soil. The hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid are introduced on the basis of an existing foaming agent to form stable three-phase foam, a traditional thickening agent is not introduced in the preparation process of the three-phase foam, and the adverse effects of slurry fluidity reduction and mechanical property reduction caused by the traditional thickening agent are effectively avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a modified stone powder lightweight soil and a preparation method and application thereof. Background Art

[0002] Stone powder, as a by-product produced during stone processing, has traditionally been regarded as industrial waste. However, by combining it with cement, lime and other cementitious materials, stone powder lightweight soil can be used as an environmentally friendly and economical lightweight building material. During the preparation process of stone powder lightweight soil, it is usually necessary to form pores inside through the foaming of aqueous foam. Therefore, its mechanical properties, thermal properties and durability largely depend on the characteristics of the pore structure formed by foaming. As a thermodynamic metastable system, aqueous foam is prone to unstable phenomena such as Ostwald ripening, agglomeration and liquid film drainage during the hardening and molding process of stone powder lightweight soil, resulting in a large number of harmful pores in the stone powder lightweight soil, which in turn deteriorates its mechanical properties and durability.

[0003] In the related art, the stability of the foam is increased by adding a thickener, but the addition of the thickener will lead to a decrease in the fluidity of the material and deterioration of the mechanical properties.

[0004] Therefore, it is necessary to provide a modified stone powder lightweight soil and a preparation method and application thereof to solve the above problems. Summary of the invention

[0005] The present invention provides a modified stone powder lightweight soil and a preparation method and application thereof, wherein hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid are introduced into the existing foaming agent to form a stable three-phase foam, and the traditional thickener is not introduced in the preparation process of the three-phase foam, which effectively avoids the adverse effects of reduced slurry fluidity and decreased mechanical properties caused by the traditional thickener, thereby effectively solving at least one technical problem involved in the background technology.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows: A method for preparing modified stone powder lightweight soil comprises the following steps: Step S1, mixing hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid in water at a mass ratio of 1:1 and stirring to form a first mixed solution with a concentration range of 1-3%, and performing ultrasonic dispersion on the first mixed solution to form a suspension; Step S2, adding a foaming agent to the suspension, continuously stirring at a first rate so that the foaming agent and the suspension are fully mixed to form a second mixed liquid, and continuously stirring the second mixed liquid at a second rate to generate foam; Step S3, according to the mass proportions, 10 parts of stone powder, 40 parts of cement, 20 parts of sand and 5.5 parts of water are mixed and stirred evenly, and then 0.32 parts of a water reducer and 5.5 parts of water are added and stirred to form a slurry; the foam generated in step S2 is added to the slurry and stirred evenly, and then the slurry is poured into a mold, the mold is covered with a plastic film and solidified into shape, and the molded sample is taken out of the mold for curing to complete the preparation of modified stone powder lightweight soil.

[0007] As a preferred improvement, the length of the hydroxylated multi-walled carbon nanotubes is 0.5-12 μm, the purity is greater than 95%, the carboxyl content is 0.45-0.55 wt%, and the specific surface area is greater than 40 m² / g; the single-stranded deoxyribonucleic acid is extracted from salmon testicles with a purity greater than 92%.

[0008] As a preferred improvement, in step S1, the stirring time is 20-30 minutes; the frequency of ultrasonic dispersion is 20-40 kHz, and the ultrasonic dispersion time is 30-45 minutes.

[0009] As a preferred improvement, in step S1, ultrasonic dispersion is performed in an ice water bath.

[0010] As a preferred improvement, in step S2, the foaming agent is sodium dodecylbenzene sulfonate with a concentration of 0.45-0.55%.

[0011] As a preferred improvement, in step S2, the first speed is 50-100 rpm, and the stirring time is 20-30 minutes; the second speed is 1550-2000 rpm, and the stirring time is 2-3 minutes.

[0012] As a preferred improvement, in step S3, the cement is selected as ordinary Portland cement; the sand is selected as natural grade quartz sand with a particle size range of 100-600 μm; the stone powder is taken from solid waste generated by tunnel excavation; and the water reducing agent component is a polycarboxylic acid polymer.

[0013] As a preferred improvement, in step S3, during the curing process, the slurry is weighed to ensure that the wet density remains at 800 kg / m3; the curing process is carried out in a standard curing room for 24 hours.

[0014] A modified stone powder lightweight soil is prepared by adopting the above-mentioned modified stone powder lightweight soil preparation method.

[0015] An application of the modified stone powder lightweight soil as a building material.

[0016] The beneficial effects of the present invention are: (1) Hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid are introduced into the existing foaming agent to form a stable three-phase foam. No traditional thickener is introduced in the preparation process of the three-phase foam, which effectively avoids the adverse effects of reduced slurry fluidity and decreased mechanical properties caused by traditional thickeners; (2) Single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes formed a stable network structure in the foam liquid film, effectively inhibiting the merging of foam and liquid loss, and significantly improving the stability of the foam. This new type of foam was applied to the preparation of stone powder lightweight soil, which enhanced the mechanical properties of the stone powder lightweight soil. (3) The introduction of three-phase foam significantly reduces the proportion of macropores in the stone powder lightweight soil and significantly increases the proportion of micropores. This optimization of the pore structure effectively prevents the connectivity of the pores, increases the proportion of closed micropores, reduces the formation of harmful macropores, and thus improves the durability of the concrete. (4) Stone powder, as a by-product generated during stone processing, has traditionally been regarded as industrial waste. The present invention combines it with cement to prepare stone powder lightweight soil, which not only realizes the resource recycling of industrial solid waste, but also significantly reduces material costs, which is in line with the concept of sustainable development. In addition, stone powder lightweight soil has good durability, can extend the service life of buildings, reduce the frequency of building maintenance and reconstruction, and thus reduce the environmental impact of buildings throughout their life cycle; (5) By partially replacing cement with stone powder, the amount of cement used can be effectively reduced, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 Schematic diagram showing the combination principle of hydroxylated multi-walled carbon nanotube / single-stranded deoxyribonucleic acid / foaming agent; Figure 2 A schematic diagram showing the principle of foam formation; Figure 3 represents the SEM image of the comparative sample at a scale of 2000 μm; Figure 4 The SEM image of the sample of Example 1 at a scale of 2000 μm is shown; Figure 5 represents the SEM image of the sample of Example 2 at a scale of 2000 μm; Figure 6 The SEM image of the sample of Example 3 at a scale of 2000 μm is shown; Figure 7 The XRD comparison diagrams of the samples of comparative example and embodiments 1-3 are shown. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1-Figure 2 This embodiment provides a method for preparing modified stone powder lightweight soil, comprising the following steps: Step S1, mixing hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid in water at a mass ratio of 1:1 and stirring to form a first mixed solution with a concentration range of 1-3%, and performing ultrasonic dispersion on the first mixed solution to form a suspension.

[0020] Among them, the length of hydroxylated multi-walled carbon nanotubes is 0.5-12μm, the purity is greater than 95%, the carboxyl content is 0.45-0.55wt%, and the specific surface area is greater than 40 m² / g; single-stranded deoxyribonucleic acid is extracted from salmon testicles with a purity greater than 92%.

[0021] In step S1, the stirring time is 20-30 minutes; the frequency of ultrasonic dispersion is 20-40 kHz, and the ultrasonic dispersion time is 30-45 minutes.

[0022] The stirring and ultrasonic dispersion process can fully disperse the hydroxylated multi-walled carbon nanotubes and the single-stranded deoxyribonucleic acid in water to form a uniformly distributed suspension. Considering the characteristics of the single-stranded deoxyribonucleic acid as a biological macromolecule, in order to avoid the influence of the high temperature waves generated during the ultrasonic dispersion process on it, an ice water bath is required during the ultrasonic dispersion process of the present invention, that is, the container containing the mixed solution is placed in an ice water bath to absorb the heat generated during the ultrasonic dispersion process and control the temperature of the mixed solution.

[0023] Hydroxylated multi-walled carbon nanotubes can be used to improve the toughness of cement-based materials due to their high specific surface area, excellent tensile strength and unique nano effect, and have the potential to stabilize foam. However, hydroxylated multi-walled carbon nanotubes are prone to agglomeration due to van der Waals forces, which affects the uniformity of dispersion. Single-stranded deoxyribonucleic acid, as a natural biomacromolecule, can form a stable and well-dispersed single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotube composite system in an aqueous environment by non-covalent bonding of the base pairs in its molecular chain through π-π stacking. Hydroxylated multi-walled carbon nanotubes are modified by single-stranded deoxyribonucleic acid, which improves the defect of easy agglomeration while retaining the excellent performance of hydroxylated multi-walled carbon nanotubes.

[0024] Step S2, adding a foaming agent to the suspension, continuously stirring at a first rate so that the foaming agent and the suspension are fully mixed to form a second mixed liquid, and continuously stirring the second mixed liquid at a second rate to generate foam.

[0025] The foaming agent is sodium dodecylbenzene sulfonate with a concentration of 0.45-0.55%.

[0026] In step S2, the first speed is 50-100 rpm, and the stirring time is 20-30 minutes; the second speed is 1550-2000 rpm, and the stirring time is 2-3 minutes.

[0027] like Figure 1-Figure 2 As shown, single-stranded deoxyribonucleic acid (ssDNA) disperses high concentrations of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) in the solution through its self-assembly. With the addition of the foaming agent, the competitive adsorption of the foaming agent and single-stranded deoxyribonucleic acid on the hydroxylated multi-walled carbon nanotubes causes some hydroxylated multi-walled carbon nanotubes to detach from the single-stranded deoxyribonucleic acid chain and combine with its hydrophobic chain. Subsequently, the foaming agent and hydroxylated multi-walled carbon nanotubes adhere to the foam liquid film, forming a stable three-phase foam during the foaming process. Due to its hydrophilicity, the remaining single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes are evenly distributed in the Platonic channels and boundaries between the foam liquid films. These single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes effectively inhibit the drainage of the foam, avoid the merging between the foams, and ensure the formation of the final stable foam.

[0028] No traditional thickener is introduced during the preparation of the three-phase foam system, effectively avoiding the adverse effects of reduced slurry fluidity and reduced strength that may be caused by traditional thickeners.

[0029] Step S3, according to the mass proportions, 10 parts of stone powder, 40 parts of cement, 20 parts of sand and 5.5 parts of water are mixed and stirred evenly, and then 0.32 parts of a water reducer and 5.5 parts of water are added and stirred to form a slurry; the foam generated in step S2 is added to the slurry and stirred evenly, and then the slurry is poured into a mold, the mold is covered with a plastic film and solidified into shape, and the molded sample is taken out of the mold for curing to complete the preparation of modified stone powder lightweight soil.

[0030] The cement selected is ordinary Portland cement; the sand selected is natural grade quartz sand with a particle size range of 100-600 μm; the stone powder is taken from solid waste, such as solid waste generated by road tunnel excavation; the water reducing agent component is polycarboxylic acid polymer.

[0031] During the curing process, the slurry needs to be weighed to ensure that the wet density remains at 800 kg / m 3 The curing process is carried out in a standard curing room (temperature 20°C, 100% relative humidity) for 24 hours.

[0032] Introducing a new type of stable three-phase foam into the preparation process of stone powder lightweight soil, the stone powder lightweight soil is modified, the pore structure is improved, and the slurry fluidity is increased, so that high-strength and high-toughness stone powder lightweight soil can be obtained.

[0033] This embodiment also provides a modified stone powder lightweight soil, which is prepared using the above-mentioned modified stone powder lightweight soil preparation method.

[0034] This embodiment also provides an application of modified stone powder lightweight soil as a building material.

[0035] In order to study the influence of the first mixed liquid on the performance of the final product, a comparative test was set up to form Examples 1-3 and a comparative example, wherein the concentration of the first mixed liquid in Example 1 was 1%, the concentration of the second mixed liquid in Example 2 was 2%, and the concentration of the third mixed liquid in Example 3 was 3%. The first mixed liquid was not added to the comparative example, and the other conditions of Examples 1-3 and the comparative example were kept consistent. The stone powder lightweight soil samples obtained from Examples 1-3 and the comparative example were taken for performance testing.

[0036] According to the "Method for Determination of Fluidity of Cement Mortar" GB / T 2419-2005 and the "Standard for Test Methods for Physical and Mechanical Properties of Concrete" GB / T 50081-2019, the fluidity and compressive strength of Examples 1-3 and the comparative example samples were measured. The fluidity test results are shown in Table 1: Table 1 Fluidity test results As can be seen from Table 1, since there is no thickener in the modified foam, the modified foam will not reduce the fluidity of the slurry. The hydroxyl, amino and phosphate groups on the surface of the single-stranded DNA / hydroxylated multi-walled carbon nanotubes have hydrophilic functional properties, which can improve the fluidity of the slurry. The test results show that a higher single-stranded DNA / hydroxylated multi-walled carbon nanotube content can improve the fluidity of the slurry, reduce the formation of macropores, and reduce the impact of stress concentration.

[0037] The compressive strength test results are shown in Table 2: Table 2 Compressive strength test results As can be seen from Table 2, with the increase of ssDNA / hydroxylated multi-walled carbon nanotube content, the compressive strength of the stone powder lightweight soil first increases and then decreases. Compared with ordinary stone powder lightweight soil, the compressive strength of the stone powder lightweight soil with 2% ssDNA / hydroxylated multi-walled carbon nanotubes added can reach 4.49 MPa at 28 days, an increase of 169%. The significant increase in compressive strength can be attributed to the stabilization of the foam by hydroxylated multi-walled carbon nanotubes and the large number of nucleation sites provided by cement hydration. When the ssDNA / hydroxylated multi-walled carbon nanotube content increases to 3%, the strength decreases to 3.34 MPa. According to microscopic observation, agglomeration occurs in the foam, resulting in a decrease in compressive strength.

[0038] The hydration products of the comparative example and examples 1-3 were observed and characterized by scanning electron microscopy (SEM). Figure 3-Figure 6 As shown. Figure 3-Figure 6 It can be seen that with the addition of single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes, the pore size of the hydration product gradually decreases, the pores are close to spherical, and the distribution of the hydration product on the pore wall is more refined. The hydroxylated multi-walled carbon nanotubes and the hydration product are intertwined to form a network structure. The hydroxylated multi-walled carbon nanotubes provide a large number of nucleation sites for the formation of CSH gel on the pore wall, making the hydration product more refined.

[0039] The phase composition and crystal structure of the hydration products of the comparative example and Examples 1-3 were observed and characterized by X-ray diffraction (XRD). Figure 7 As shown. The results showed that the incorporation of ssDNA / MWCNTs-OH led to a significant decrease in the Ca / Si ratio in the stone powder lightweight soil. This further suggests that multi-walled carbon nanotubes promote the formation of more CSH on the pore walls of cement particles, resulting in a denser pore wall structure. The comparative example contains a large amount of unreacted C2S and C3S mineral phases and shows a lower degree of hydration.

[0040] The microstructure of the comparative example and Examples 1-3 was studied by X-ray computed tomography (X-CT). The results showed that the micropore ratio (diameter <200 μm) of ordinary stone powder lightweight soil was 11.85%, when the content of single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes was 1%, the micropore ratio (diameter <200 μm) reached 47.13%, and when the content of single-stranded deoxyribonucleic acid / hydroxylated multi-walled carbon nanotubes was 2%, the micropore ratio (diameter <200 μm) reached 82.5%. The significant increase in the proportion of small pores is conducive to the improvement of the strength of stone powder lightweight soil. In addition, the optimization of the pore structure effectively prevents the connectivity of the pores, increases the proportion of closed micropores, and reduces the formation of harmful macropores, thereby improving the durability of stone powder lightweight soil.

[0041] Compared with ordinary stone powder lightweight soil, the compressive strength of stone powder lightweight soil with 2% single-stranded DNA / hydroxylated multi-walled carbon nanotubes can reach 4.49 MPa at 28 days, an increase of 169%. Through X-ray computed tomography (X-CT) analysis, most of the pores in ordinary stone powder lightweight soil have a diameter of more than 200μm and are interconnected, while after adding single-stranded DNA / hydroxylated multi-walled carbon nanotubes, the proportion of macropores is significantly reduced and the proportion of micropores is significantly increased. When the content of single-stranded DNA / hydroxylated multi-walled carbon nanotubes is 2%, the proportion of micropores reaches 82.5%, while that of ordinary stone powder lightweight soil is only 11.85%. This optimization of pore structure effectively prevents the connectivity of pores, increases the proportion of closed micropores, and reduces the formation of harmful macropores, thereby improving the durability of concrete. In addition, due to the hydrophilic groups on the surface of ssDNA / hydroxylated multi-walled carbon nanotubes, the fluidity of the stone powder lightweight soil is significantly improved, which is beneficial to construction operations, reduces the formation of macropores, reduces stress concentration, and further improves the performance of concrete.

[0042] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for preparing modified stone powder lightweight soil, characterized in that: The steps include: Step S1, mixing hydroxylated multi-walled carbon nanotubes and single-stranded deoxyribonucleic acid in water at a mass ratio of 1:1 and stirring to form a first mixed solution with a concentration range of 1-3%, and performing ultrasonic dispersion on the first mixed solution to form a suspension; Step S2, adding a foaming agent to the suspension, continuously stirring at a first rate so that the foaming agent and the suspension are fully mixed to form a second mixed liquid, and continuously stirring the second mixed liquid at a second rate to generate foam; Step S3, according to the mass proportions, 10 parts of stone powder, 40 parts of cement, 20 parts of sand and 5.5 parts of water are mixed and stirred evenly, and then 0.32 parts of a water reducer and 5.5 parts of water are added and stirred to form a slurry; the foam generated in step S2 is added to the slurry and stirred evenly, and then the slurry is poured into a mold, the mold is covered with a plastic film and solidified into shape, and the molded sample is taken out of the mold for curing to complete the preparation of modified stone powder lightweight soil.

2. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: The length of hydroxylated multi-walled carbon nanotubes is 0.5-12μm, the purity is greater than 95%, the carboxyl content is 0.45-0.55 wt%, and the specific surface area is greater than 40 m² / g; the single-stranded deoxyribonucleic acid is extracted from salmon testicles with a purity greater than 92%.

3. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: In step S1, the stirring time is 20-30 minutes; the frequency of ultrasonic dispersion is 20-40 kHz, and the ultrasonic dispersion time is 30-45 minutes.

4. The method for preparing modified stone powder lightweight soil according to claim 3, characterized in that: In step S1, ultrasonic dispersion is performed in an ice water bath.

5. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: In step S2, the foaming agent is sodium dodecylbenzene sulfonate with a concentration of 0.45-0.55%.

6. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: In step S2, the first speed is 50-100 rpm, and the stirring time is 20-30 minutes; the second speed is 1550-2000 rpm, and the stirring time is 2-3 minutes.

7. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: In step S3, the cement is selected as ordinary Portland cement; the sand is selected as natural grade quartz sand with a particle size range of 100-600 μm; the stone powder is taken from solid waste generated by tunnel excavation; and the water reducing agent component is a polycarboxylic acid polymer.

8. The method for preparing modified stone powder lightweight soil according to claim 1, characterized in that: In step S3, during the curing process, the slurry is weighed to ensure that the wet density remains at 800 kg / m 3 ; The curing process is carried out in a standard curing room and the curing time is 24 hours.

9. A modified stone powder lightweight soil, characterized in that: The modified stone powder lightweight soil is prepared by the preparation method of any one of claims 1 to 8.

10. An application of the modified stone powder lightweight soil as claimed in claim 9, characterized in that: Used as building material.

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