Quick-setting early-strength bubble lightweight modified in-situ soil, preparation method thereof and application of quick-setting early-strength bubble lightweight modified in-situ soil in highway emergency repair

Abstract

The invention relates to quick-setting early-strength bubble light modified in-situ soil and a preparation method and application thereof.The quick-setting early-strength bubble light modified in-situ soil is prepared from foam and slurry according to the volume ratio of (1-3): 1, the slurry is prepared from, by weight, 0-265 parts of in-situ soil, 265-530 parts of quick-hardening sulphoaluminate cement and 132-398 parts of water, and the foam is prepared from a foaming agent and water. Compared with the prior art, the bubble light-weight modified in-situ soil has the characteristics of rapid hardening, early strength, light weight, adjustability and high fluidity, and meets the rapid traffic requirement of emergency repair of roads.

Description

Technical Field

[0001] The present invention relates to the technical field of highway repair, in particular to a quick-setting, early-strength, bubble-filled, lightweight modified in-situ soil, a preparation method thereof, and an application thereof in highway emergency repair. Background Art

[0002] Highway subgrades are a crucial component of highway construction, and their stability directly impacts their service life and driving safety. However, due to natural disasters (such as heavy rain, floods, and earthquakes) or human factors (such as overloading and improper construction), highway subgrades often collapse and sink, leading to traffic disruptions and seriously threatening driving safety. Traditional subgrade repair methods, such as gravel filling, concrete pouring, or cement-stabilized soil repair, are subject to long construction periods, difficult material transportation, and high costs, making them difficult to implement quickly in remote areas or emergency situations.

[0003] In recent years, bubble-filled lightweight soil has garnered widespread attention in ground treatment and roadbed repair due to its lightweight, adjustable strength, and high fluidity. Bubble-filled lightweight soil, created by incorporating foam into cement slurry, creates a lightweight material with numerous tiny bubbles. This effectively reduces material density and improves fluidity while maintaining a certain level of strength.

[0004] However, there are the following deficiencies when applied to highway emergency repairs:

[0005] First, the rapid setting performance is insufficient. Existing bubble lightweight soil is mostly used with ordinary Portland cement as the binder in roadbed projects. Its initial setting time is long, which makes it difficult to meet the requirements of rapid emergency repairs.

[0006] Second, the adaptability of in-situ soil is limited. The water content, particle grading, porosity and chemical composition of the sandy in-situ soil in accident-prone areas vary greatly. If used directly without treatment, it is easy to cause foam collapse or insufficient strength.

[0007] Third, the ratio of foam content to mud is insufficiently optimized. In existing technologies, foam content is often fixed, without systematic research into the impact of the foam-to-mud volume ratio on material properties. This results in a poor balance between density, strength, and fluidity. For example, too high a foam content can reduce strength, while too low a foam content makes it difficult to achieve lightweighting.

[0008] Fourth, there is a contradiction between early strength and lightness. Existing bubble lightweight soils often lack early strength when pursuing low density, making it difficult to meet the needs of emergency repair scenarios.

[0009] For example, CN117024103A discloses a high-dosage phosphogypsum foam lightweight soil roadbed backfill material and its preparation, comprising the following raw materials in parts by weight: 10-15 parts of cement, 30-35 parts of mineral powder, 50-60 parts of phosphogypsum, 0.1-0.5 parts of foaming agent, 3-5 parts of coagulant, 2-4 parts of waterproofing agent, 0.2-0.5 parts of water reducing agent, 40-60 parts of water, and 1-1.5 parts of corn straw fiber. The performance shown in Examples 1-4 is: 790 kg / m 3 and 800kg / m 3 The high-density phosphogypsum foam lightweight soil roadbed backfill material has a 28d compressive strength of 1.2MPa.

[0010] Therefore, developing a method based on in-situ soil to make it have the characteristics of rapid setting and early strength has become a technical problem that needs to be solved urgently in the field of highway emergency repair. Summary of the Invention

[0011] The purpose of the present invention is to provide a fast-setting, early-strength, bubble-formed lightweight modified in-situ soil and its preparation method and application in highway emergency repair in order to overcome any one or more of the above-mentioned defects of the existing in-situ soil.

[0012] The purpose of the present invention can be achieved by the following technical solutions:

[0013] One of the technical solutions of the present invention is to provide a fast-setting, early-strength, bubbled, lightweight modified in-situ soil, comprising foam and mud in a volume ratio of (1 to 3): 1, wherein the mud comprises the following raw materials in parts by weight: 0 to 265 parts of in-situ soil, 265 to 530 parts of fast-hardening sulphoaluminate cement, and 132 to 398 parts of water, and the foam comprises a foaming agent and water.

[0014] In some specific embodiments, the in-situ soil is sandy soil, meeting the following requirements: moisture content of 10% to 15%, fine particles <15%, medium-coarse sand >70%, porosity of 30% to 35%, organic matter <1.5%, sulfate <0.3%, and pH 6.5 to 7.5.

[0015] In some embodiments, the foaming agent is an anionic surfactant.

[0016] In some embodiments, the density of the foam is 50±2 kg / m 3 .

[0017] In some specific embodiments, the mass ratio of the in-situ soil to sulphoaluminate cement is (0-5):(5-10).

[0018] More preferably, the mass ratio of the in-situ soil to sulphoaluminate cement may be 0:10, 1:9, 2:8, 3:7, 4:6, or 5:5.

[0019] In some specific embodiments, the ratio of the mass of water, the mass of in-situ soil and the mass of sulphoaluminate cement in the slurry is 1:(1-3).

[0020] More preferably, the ratio of the sum of the mass of water, the mass of the in-situ soil and the mass of the sulphoaluminate cement in the slurry is 1:2.

[0021] In some specific embodiments, the mass ratio of water to foaming agent in the foam is (50-70):1.

[0022] More preferably, the mass ratio of water to foaming agent in the foam is 60:1.

[0023] The second technical solution of the present invention is to provide a method for preparing the fast-setting, early-strength, bubbled, lightweight modified in-situ soil as described in one of the above technical solutions, comprising the following steps:

[0024] S1. Weigh in-situ soil, sulfoaluminate cement, and water according to weight and mix to obtain a uniform, lump-free slurry;

[0025] S2, mixing a foaming agent and water, and introducing compressed air to obtain foam;

[0026] S3. Mixing the mud obtained in step S1 with the foam obtained in step S2 to obtain soil slurry, which is the rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil.

[0027] The third technical solution of the present invention is to provide a use of the fast-setting, early-strength, bubbled, lightweight modified in-situ soil as described in one of the above technical solutions in highway maintenance.

[0028] In some specific embodiments, the rapid-setting early-strength bubble lightweight modified in-situ soil is used as a roadbed filler, and the curing temperature during highway maintenance is 20±2° C., the humidity is ≥95%, and the curing time is at least 6 hours.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention uses fast-hardening sulphoaluminate cement as a cementitious material, combines it with systematically treated sandy in-situ soil and an optimized foam dosage to prepare a bubble-filled lightweight modified in-situ soil with fast setting, early strength, light weight, adjustable weight and high fluidity, so as to meet the demand for rapid opening to traffic in emergency highway repairs.

[0031] By systematically treating the sandy in-situ soil to ensure its compatibility with sulphoaluminate cement and foam, problems such as foam collapse or insufficient strength can be effectively avoided, thereby improving the stability of the material.

[0032] The rapid hydration of fast-hardening sulphoaluminate cement as the cementitious material significantly improves its rapid-setting and early-strength properties. Compared to ordinary Portland cement, sulphoaluminate cement develops a certain compressive strength within 6 hours, with a 24-hour strength of 0.95-1.40 MPa, meeting the needs of rapid highway reopening during emergency repairs.

[0033] By optimizing the volume ratio of foam to slurry, a balance between lightweight and strength is achieved, effectively reducing material density while ensuring foam stability. This invention, through systematic testing, validates the impact of different volume ratios on material performance, providing a more flexible performance control solution.

[0034] (2) The present invention provides a method for preparing fast-setting, early-strength, bubble-filled, lightweight modified in-situ soil using sandy in-situ soil as raw material. This method can efficiently utilize the in-situ soil in accident-prone areas, reduce the demand for externally transported materials, and lower construction costs. It has great economic value and potential for promotion and application.

[0035] (3) The preparation method of the fast-setting, early-strength, bubble-formed lightweight modified in-situ soil of the present invention is simple and easy to transport. As a repair material for roadbed collapse, it is lightweight, quickly develops strength, and has a certain degree of lightness on the basis of meeting the roadbed performance requirements to reduce the vertical pressure on the original foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The figure is a schematic diagram of the preparation process of the rapid-setting, early-strength, bubbled, lightweight modified in-situ soil of the present invention. DETAILED DESCRIPTION

[0037] The present invention provides a rapid-setting, early-strength, bubble-filled, lightweight modified in-situ soil and a preparation method thereof, the preparation method comprising the following steps:

[0038] (1) Preparation of raw materials:

[0039] In-situ soil: Sandy in-situ soil taken from accident-prone areas. After pretreatment, the moisture content is 10% to 15%, fine particles (<0.075mm) <15%, medium-coarse sand (0.252mm) >70%, porosity 30% to 35%, organic matter <1.5%, sulfate <0.3%, and pH 6.5 to 7.5.

[0040] Sulphoaluminate cement: The cement used is Shili brand R·SAC42.5 fast-hardening sulphoaluminate cement produced by Dengdian Group Cement Co., Ltd., which meets the requirements of "Sulphoaluminate Cement" (GB20472-2006), with an initial setting time of <30 minutes and a one-day compressive strength of ≥30MPa.

[0041] Foaming agent: anionic surfactant (FB-602 plant-based cement foaming agent produced by Shanghai Fangbao Building Materials Technology Co., Ltd.), diluted 60 times with water and foamed, with a foam density of 50±2kg / m 3 .

[0042] Water: Clean water, pH 6.5-7.5, free of harmful impurities.

[0043] (2) Pretreatment of sandy in-situ soil:

[0044] 50 kg of sandy soil was collected and sealed. The moisture content (105°C oven-drying method), particle size distribution (standard sieving method), porosity (pycnometer method), organic matter (potassium dichromate oxidation method), sulfate (barium chloride titration method), and pH (1:2.5 soil-water ratio) were determined.

[0045] Adjust the moisture content: If the moisture content is >15%, dry at 40-50°C to 10-15%. If the moisture content is <10%, spray with distilled water and stir for 5 minutes. Verify the moisture content with three 200g subsamples. The standard deviation should be <0.5%.

[0046] Optimize particle size distribution: If fine particles are >15%, remove them with a 0.075mm wet sieve. If medium-coarse sand is <70%, add 0.25-2mm quartz sand. Take three samples to confirm that fine particles are <15% and medium-coarse sand is >70%.

[0047] Porosity control: If >35%, lightly compact with 50% Proctor energy; if <30%, loosely mix. Take three samples to verify the porosity is 30% to 35%.

[0048] Chemical correction: If organic matter is >1.5%, treat with 3% hydrogen peroxide (1:10 soil-to-liquid ratio); if sulfate is >0.3%, wash with distilled water (1:5 soil-to-water ratio); if pH is <6.5, add 0.5%-1% lime; if pH is >7.5, add 0.1%-0.3% dilute sulfuric acid. Take three samples to confirm organic matter is <1.5%, sulfate is <0.3%, and pH is 6.5-7.5.

[0049] (3) Weigh the treated sand (0-265 parts), sulphoaluminate cement (265-530 parts), and water (1 / 2 of the sum of the mass of the sand and sulphoaluminate cement) according to the mass ratio. Dry mix the sand and cement for 2 minutes. After adding water, stir with a mechanical mixer for 2-3 minutes until the slurry is uniform and free of lumps.

[0050] (4) Take a plant-based foaming agent and dilute it with water at a ratio of 1:60. Place the diluted solution in a high-pressure foaming machine, introduce compressed air, and foam at high speed until the foam density reaches 50±2kg / m 3 . Check foam stability to ensure volume loss <5% within 30 minutes.

[0051] (5) Mix foam and slurry in a volume ratio of 1 to 3:1 and stir for 80 to 120 seconds until uniform, forming a fast-setting, early-strength, and lightweight in-situ soil slurry. Measure the fluidity (160 to 200 mm). If it does not meet the standard, fine-tune the water volume or foam ratio.

[0052] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0053] In the following examples and comparative examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0054] Example 1:

[0055] 26.5 kg of sand, 26.5 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 3:1.

[0056] Example 2:

[0057] 26.5 kg of sand, 26.5 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 2:1.

[0058] Example 3:

[0059] 26.5 kg of sand, 26.5 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 1:1.

[0060] Example 4:

[0061] 21.2 kg of sand, 31.8 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 3:1.

[0062] Example 5:

[0063] 21.2 kg of sand, 31.8 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 2:1.

[0064] Example 6:

[0065] 21.2 kg of sand, 31.8 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 1:1.

[0066] Example 7:

[0067] 15.9 kg sand, 37.1 kg sulphoaluminate cement, 26.5 kg water, and the volume ratio of foam to mud is 3:1.

[0068] Example 8:

[0069] 15.9 kg sand, 37.1 kg sulphoaluminate cement, 26.5 kg water, and the volume ratio of foam to mud is 2:1.

[0070] Example 9:

[0071] 15.9 kg sand, 37.1 kg sulphoaluminate cement, 26.5 kg water, and the volume ratio of foam to mud is 1:1.

[0072] Example 10:

[0073] 10.6 kg of sand, 42.4 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 3:1.

[0074] Example 11:

[0075] 10.6 kg of sand, 42.4 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 2:1.

[0076] Example 12:

[0077] 10.6 kg of sand, 42.4 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 1:1.

[0078] Example 13:

[0079] 5.3 kg of sand, 47.7 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 3:1.

[0080] Example 14:

[0081] 5.3 kg of sand, 47.7 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 2:1.

[0082] Example 15:

[0083] 5.3 kg of sand, 47.7 kg of sulphoaluminate cement, 26.5 kg of water, and the volume ratio of foam to mud is 1:1.

[0084] Example 16:

[0085] 0kg of sand, 53kg of sulphoaluminate cement, 26.5kg of water, and the volume ratio of foam to mud is 3:1.

[0086] Example 17:

[0087] 0kg sand, 53kg sulphoaluminate cement, 26.5kg water, foam to mud volume ratio is 2:1.

[0088] Example 18:

[0089] 0kg sand, 53kg sulphoaluminate cement, 26.5kg water, and the volume ratio of foam to mud is 1:1.

[0090] The slurries prepared in Examples 1-18 were poured into 70.7 mm cubic molds and gently vibrated for 10-15 seconds to remove large pores. After pouring, the molds were cured at 20±2°C and ≥95% humidity. The compressive strength was tested after 6, 8, 12, and 24 hours.

[0091] Perform the following performance tests:

[0092] (1) Fluidity: Measured according to the Technical Specification for Bubble Mixed Lightweight Soil Filling Engineering (CJJ / T 177-2012), with a target value of 160-200 mm. Each example was measured three times, and the average value was taken. The measurement results are shown in Table 1.

[0093] (2) Compressive strength: A fully automatic compression and flexural testing machine was used to measure the compressive strength after 6 hours, 8 hours, 12 hours, and 24 hours according to the Standard for Test Methods for Physical and Mechanical Properties of Concrete (GB-T 50081-2019). The crossbeam movement speed of the fully automatic compression and flexural testing machine was 1.00 mm / min, and the test was stopped when the maximum displacement reached 5 mm. The average value of three specimens was taken for each group. The test results are shown in Table 1.

[0094] (3) Wet density: Weigh immediately after pouring to calculate the wet density. The target value is 600-1000 kg / m 3 , take the average value of three specimens in each group, and the test results are shown in Table 1.

[0095] Table 1 Fluidity and compressive strength of rapid-setting, early-strength, bubble-filled lightweight in-situ soil

[0096]

[0097] As can be seen from Table 1, in terms of rapid setting and early strength, the 6-hour strength of all prepared examples is significantly affected by the sulphoaluminate cement and foam content. For example, Examples 1 and 4 do not meet the 0.4 MPa performance index for roadbed filling specified in the "Technical Specification for Bubble Mixed Lightweight Soil Fill Engineering" (CJJT177-2012), but their 8-hour strength is ≥0.65 MPa, 12-hour strength is ≥0.78 MPa, and 24-hour strength is ≥0.95 MPa, meeting the emergency traffic requirements. As the sulphoaluminate cement content increases, the early strength also increases. However, when the sand content is 0, there are problems such as increased material costs and reduced construction economy.

[0098] As can be seen from Table 1, in terms of lightness, the wet density of the prepared rapid-setting early-strength bubble lightweight in-situ soil slurry is 600-1000 kg / m3 On the one hand, it is inversely proportional to the amount of foam added. When the volume ratio of foam to mud is 3:1, the lowest wet density appears, that is, Example 1: 620 kg / m 3 When the volume ratio of foam to slurry is 1:1, the highest wet density appears, i.e., Example 18: 980 kg / m 3 On the other hand, it is also proportional to the amount of sulphoaluminate cement added. As the amount of sulphoaluminate cement increases, the wet density also increases. Therefore, it can be adjusted according to the bearing capacity requirements of the foundation.

[0099] It can be seen from Table 1 that in terms of fluidity, the prepared rapid-setting early-strength bubble lightweight in-situ soil slurry has a fluidity of 155-195 mm, which meets the construction requirement of 160-200 mm. The higher the foam volume ratio, the better the fluidity, but the strength formation rate may decrease.

[0100] As can be seen from Table 1, with respect to the in-situ soil content, reducing the sand content from 265 parts to 0 parts (Examples 1-18) gradually increases the compressive strength, but slightly increases the wet density. Overall, controlling the in-situ soil to sulphoaluminate cement content to 10%:90% achieves a good balance between fluidity, economic efficiency, and in-situ soil content, as demonstrated in Example 13, which is suitable for practical engineering.

[0101] As can be seen from Table 1, in terms of foam dosage, as the foam to mud volume ratio changes from 3:1 to 1:1, the compressive strength gradually increases, but the wet density increases and the fluidity decreases. When the foam to mud volume ratio is 1:1, the highest early strength appears, that is, it reaches 0.65-0.90MPa in 6 hours, which is suitable for rapid traffic; when the foam to mud volume ratio is 3:1, the lowest wet density appears, that is, 620-720kg / m 3 , suitable for scenarios with low foundation bearing capacity.

[0102] To illustrate the impact of the key technical parameters of the present invention on material properties, comparative tests were conducted with representative examples. Using Example 13 as a control, the following variables were tested: untreated in-situ soil (Comparative Example 1), foaming density deviation (Comparative Example 2), and the binder was replaced with ordinary Portland cement (produced by Taicang Conch Cement Co., Ltd., P·C42.5 composite Portland cement) (Comparative Example 3). The test results showed that:

[0103] In Comparative Example 1, due to the in-situ soil moisture content of 22%, foam collapse and a significant decrease in early strength occurred (6h strength <0.2MPa);

[0104] In Comparative Example 2, the foam density is 45 kg / m 3 , the slurry fluidity is reduced and the forming is uneven;

[0105] In Comparative Example 3, the 6h strength of the Portland cement group was only 0.18 MPa, which was much lower than 0.52 MPa of Example 13.

[0106] The above data show that the in-situ soil pretreatment method, foam density control, and selection of fast-hardening cement proposed in the present invention are all necessary prerequisites for achieving rapid repair of roads to facilitate traffic.

[0107] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A fast-setting, early-strength, bubble-filled, lightweight modified in-situ soil, characterized in that: The invention comprises foam and mud in a volume ratio of (1-3):

1. The mud comprises the following raw materials in parts by weight: 0-265 parts of in-situ soil, 265-530 parts of fast-hardening sulphoaluminate cement, and 132-398 parts of water. The foam comprises a foaming agent and water.

2. The rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil according to claim 1, characterized in that: The in-situ soil is sandy soil, meeting the following requirements: moisture content of 10% to 15%, fine particles <15%, medium-coarse sand >70%, porosity of 30% to 35%, organic matter <1.5%, sulfate <0.3%, and pH 6.5 to 7.

5.

3. The rapid-setting, early-strength, bubble-formed lightweight modified in-situ soil according to claim 1, characterized in that: The foaming agent is an anionic surfactant.

4. The rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil according to claim 1, characterized in that: The density of the foam is 50±2 kg / m 3 .

5. The rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil according to claim 1, characterized in that: The mass ratio of the in-situ soil to the sulphoaluminate cement is (0-5):(5-10).

6. The rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil according to claim 1, characterized in that: The ratio of the mass of water in the slurry to the mass of the in-situ soil and the mass of the sulphoaluminate cement is 1:(1-3).

7. The rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil according to claim 1, characterized in that: The mass ratio of water to foaming agent in the foam is (50-70):

1.

8. A method for preparing the fast-setting, early-strength, bubble-filled lightweight modified in-situ soil according to any one of claims 1 to 7, characterized in that: The steps include: S1. Weigh in-situ soil, sulfoaluminate cement, and water according to weight and mix to obtain a uniform, lump-free slurry; S2, mixing a foaming agent and water, and introducing compressed air to obtain foam; S3. Mixing the mud obtained in step S1 with the foam obtained in step S2 to obtain soil slurry, which is the rapid-setting, early-strength, bubble-filled lightweight modified in-situ soil.

9. Use of the fast-setting, early-strength, bubbled, lightweight modified in-situ soil according to any one of claims 1 to 7 in highway maintenance.

10. The use according to claim 9, characterized in that The quick-setting, early-strength, bubble-filled lightweight modified in-situ soil is used as a roadbed filler and is cured and solidified at a temperature of 20±2° C., a humidity of ≥95%, and a time of at least 6 hours during highway maintenance.

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