A high-performance foam lightweight soil material for bridge head settlement

Abstract

The present invention relates to a high-performance foamed lightweight soil material for bridgehead settlement, and relates to the field of highway technology. The foamed lightweight soil material comprises the following components by weight: 50-60 parts cement, 40-45 parts fly ash, 35-40 parts mineral powder, 6-9 parts foaming agent, 5-8 parts modified carbon fiber, and 50-70 parts water. The lightweight soil material of the present invention has low density, light weight, high strength, and excellent overall performance. It effectively solves the technical problem that existing lightweight soil materials have poor anti-settlement effects and are therefore unable to effectively address bridgehead settlement. It is of great significance to the construction and development of highway projects.

Description

Technical Field

[0001] The invention relates to the technical field of highways, in particular to a high-performance foamed lightweight soil material for bridge head settlement. Background Art

[0002] In recent years, with the rapid development of highway construction, while the overall operating quality and driving speeds of highways have been significantly improved, the problem of vehicle bouncing at bridgeheads due to uneven settlement has become increasingly prominent. The bridgehead is a critical part of the highway, connected to the roadbed and forming the transition between the roadbed and the bridge. If this location is not properly treated during construction, it can easily cause vehicles to bouncing and jolt during passage, affecting normal operation and, in severe cases, even leading to traffic accidents. How to solve the problem of bridgehead settlement, ensure smooth passage of vehicles through the bridgehead, and avoid vehicle bouncing has always been a technical issue that highway construction departments are eager to address.

[0003] The fundamental cause of vehicle bouncing at bridgeheads is when the difference in settlement between the abutment and the adjacent road exceeds a certain threshold, causing vehicles to jolt as they pass. Treating the roadbed at the bridgehead and using lightweight soil materials to reduce its own weight, minimize settlement, and lower roadbed stress is an effective approach.

[0004] Foam lightweight soil material is a new type of lightweight material with a large number of closed pores, which is formed by preparing a foaming agent aqueous solution into foam by physical methods, fully foaming it mechanically, uniformly mixing it with necessary components (cementitious materials, water, fine-grained sand or sandy soil, etc.) in a certain proportion, and hardening it through physical and chemical actions. This material has many advantages such as light weight, adjustable strength, high fluidity, and self-solidification. Despite this, the existing lightweight soil materials are limited by their own performance. When they are actually used at bridge heads, a large degree of settlement is still inevitable, and the problem of vehicle jumping at the bridge head cannot be effectively solved. Therefore, providing a new type of high-performance foam lightweight soil material for bridge head settlement is the key to promoting highway engineering construction. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance foam lightweight soil material for bridge head settlement, so as to solve the problems existing in the above-mentioned prior art, thereby effectively solving the settlement problem that is prone to occur at the bridge head.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a foamed lightweight soil material, comprising the following raw material components in parts by weight:

[0008] 50-60 parts of cement, 40-45 parts of fly ash, 35-40 parts of mineral powder, 6-9 parts of foaming agent, 5-8 parts of modified carbon fiber and 50-70 parts of water.

[0009] Furthermore, the preparation method of the foaming agent comprises the following steps:

[0010] a. Mix hexamethylene diisocyanate and propylene oxide ethylene oxide copolyol at 55-60°C, then add a chain extender and a catalyst, react, and emulsify the resulting reaction system with water to obtain a polyurethane emulsion;

[0011] b. mixing rosin with the polyurethane emulsion, adding a crosslinking agent, and reacting to obtain the foaming agent.

[0012] Furthermore, the molecular weight of the propylene oxide ethylene oxide copolyether polyol is 2500-3500.

[0013] Furthermore, the mass ratio of the propylene oxide ethylene oxide copolyether polyol to hexamethylene diisocyanate is 70-90:30-45.

[0014] Furthermore, the temperature of the mixed reaction in step a is 70° C. and the time is 1-1.5 hours; the reaction in step a is: reacting at 70° C. for 1 hour and then keeping warm at 80° C. for 1-2 hours.

[0015] Furthermore, the chain extender is a mixture of dimethylolpropionic acid and diethylene glycol in a mass ratio of 2.3-2.5:1; and the catalyst is dibutyltin dilaurate or stannous octoate.

[0016] Furthermore, the mass ratio of the propylene oxide ethylene oxide copolyether polyol, hexamethylene diisocyanate, chain extender and catalyst is 70-90:30-45:5-12:0.02-0.03.

[0017] The reaction system was cooled to 45-50°C before adding water for emulsification.

[0018] Furthermore, the added amount of rosin is 2-3 times the mass of the raw material hexamethylene diisocyanate; and the added amount of the cross-linking agent is 8-10% of the mass of the rosin.

[0019] Furthermore, in step b, the temperature of the system for adding the cross-linking agent is 70-75°C; in step b, the temperature of the reaction is 70-75°C and the reaction time is 0.5h.

[0020] Furthermore, the preparation of the modified carbon fiber comprises the following steps:

[0021] (1) Oxidation treatment of carbon fiber using concentrated nitric acid;

[0022] Specifically, the carbon fiber is immersed in concentrated nitric acid, heated to 65-70°C for reaction for 1-2 hours, then taken out, washed, and dried.

[0023] (2) The oxidized carbon fiber obtained in step (1), an ionic surfactant, and an ethanol solution of ethylenediamine and a silane coupling agent are mixed, and then ethyl orthosilicate and titanium tetrachloride are added to react. After the reaction is completed, the mixture is filtered, washed, and dried to obtain the modified carbon fiber.

[0024] Furthermore, the reaction conditions in step (2) are: stirring and reacting at 45-50° C. for 7-8 hours; and the mass fraction of the silane coupling agent in the ethanol solution of the silane coupling agent is 5%.

[0025] Furthermore, the mass ratio of the silane coupling agent, surfactant and ethylenediamine is 2-3:0.8-1:8-10; the volume ratio of the ethyl orthosilicate, titanium tetrachloride and the ethanol solution of the silane coupling agent is 6-7:3-4:100.

[0026] The ionic surfactant is dodecylbenzenesulfonic acid.

[0027] The present invention also provides a method for preparing the foamed lightweight soil material, comprising the following steps:

[0028] (1) uniformly mixing the cement, fly ash, mineral powder, modified carbon fiber and water in proportion by mass to obtain a mixture;

[0029] (2) The foaming agent is foamed by a foam generator to obtain prefabricated foam, and then the prefabricated foam is mechanically mixed with the mixture to obtain the foamed lightweight soil material.

[0030] The foaming effect of the foaming agent directly affects the performance of the foamed lightweight soil. The appropriate foaming ratio is the basis for meeting the ultra-light density requirements of the lightweight soil. At the same time, the higher foam strength and foam stabilizing effect can effectively ensure the pouring height of the lightweight soil and maintain its own weight before initial setting. After the cement is hydrated, the foam performance will also affect the overall water absorption rate of the lightweight soil material. The existing foaming agents mainly include rosin, animal protein, plant protein, composite foaming agents, etc. The main problems they have are poor foam stabilizing performance and serious water bleeding, which directly limit the improvement of the performance of the lightweight soil material. The rosin-polyurethane cross-linked foaming agent prepared by the present invention has good foaming effect and excellent stability in the lightweight soil material. At the same time, it gives the lightweight soil material good impermeability, effectively ensures the lightweight and practical application performance of the lightweight soil, and further ensures the application of lightweight soil as a material to prevent bridgehead settlement.

[0031] Carbon fiber is light, strong and corrosion-resistant, and has shown good application prospects in many fields. However, when it is used in building materials, it still inevitably has the problem of unsatisfactory bonding at the interface with cement-based gelling materials. The present invention combines the polyurethane foaming agent used, proceeds from the aspect of ensuring foam stability, and combines the actual need of improving the bonding force between carbon fiber materials and interfaces, and specifically determines the modification method of carbon fiber. The carbon fiber modified by the present invention can not only achieve efficient bonding with the substrate, ensuring the high strength of the lightweight soil material, but more importantly, it can achieve effective stabilization of the polyurethane component foam in the present invention, avoiding damage to the foam; at the same time, the addition of modified carbon fiber also effectively achieves effective stress dispersion, avoiding cracking and settlement of the material, and comprehensively ensuring the effect of light weight, high strength and low settlement of the foam lightweight soil material.

[0032] The present invention discloses the following technical effects:

[0033] The lightweight soil material of the present invention has low density, light weight, high strength and excellent comprehensive performance. It effectively solves the technical problem that the existing lightweight soil material has poor anti-settlement effect and cannot effectively solve the bridge head settlement. It is of great significance to the construction and development of highway engineering. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The fly ash used in the embodiments of the present invention is Class II fly ash.

[0040] Example 1 Preparation of Foam Lightweight Soil Material

[0041] The raw material mass proportions of the foamed lightweight soil material of this embodiment are as follows:

[0042] 55 parts of cement, 45 parts of fly ash, 35 parts of mineral powder, 8 parts of foaming agent, 7 parts of modified carbon fiber and 60 parts of water.

[0043] Step 1, preparation of foaming agent:

[0044] (1) 80 parts of propylene oxide ethylene oxide copolyether polyol (molecular weight 2500) that had been vacuum dehydrated (vacuum dehydration at 110°C for 2 hours) were mixed with 42 parts of hexamethylene diisocyanate, and reacted at 70°C for 1 hour. 10 parts of a chain extender and 0.02 parts of a catalyst were then added, and the temperature was kept constant for 1 hour. The mixture was then kept at 80°C for 1.5 hours. The system was cooled to 45°C, and water was then added for emulsification to obtain a polyurethane emulsion system.

[0045] The chain extender is a mixture of dimethylolpropionic acid and diethylene glycol in a mass ratio of 2.3:1; and the catalyst is dibutyltin dilaurate.

[0046] (2) At 55°C, rosin and polyurethane emulsion system were uniformly mixed, then heated to 70°C, 9 parts of silane coupling agent A-171 were added, and the mixture was reacted for 0.5h to obtain a foaming agent;

[0047] The added amount of rosin is 2.5 times the mass of the raw material hexamethylene diisocyanate; the added amount of the cross-linking agent is 9% of the mass of the rosin.

[0048] Step 2, preparation of modified carbon fiber:

[0049] (1) Add carbon fiber to concentrated nitric acid, heat to 65°C for 2 hours, wash and dry to obtain oxidized carbon fiber;

[0050] (2) Add the oxidized carbon fiber to an ethanol solution of the silane coupling agent KH550 (KH550 mass fraction is 5%), then add dodecylbenzenesulfonic acid and ethylenediamine, and stir and react at room temperature for 15 minutes; then add ethyl orthosilicate and titanium tetrachloride to the system, and stir and react at 50°C for 7 hours; after the reaction is completed, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0051] The mass ratio of the silane coupling agent, the surfactant and ethylenediamine is 2:0.9:8; the volume ratio of the ethyl orthosilicate, titanium tetrachloride and the ethanol solution is 7:3:100.

[0052] Step 3: Prepare foam lightweight soil material:

[0053] (1) mixing cement, fly ash, mineral powder, modified carbon fiber and water in proportion by mass to obtain a mixture;

[0054] (2) The foaming agent is foamed using a foam generator to obtain a density of 55 kg / m 3 The prefabricated foam is then mechanically mixed with the mixture of step (1) to obtain a foamed lightweight soil material.

[0055] Example 2

[0056] The raw material mass proportions of the foamed lightweight soil material of this embodiment are as follows:

[0057] 60 parts of cement, 40 parts of fly ash, 40 parts of mineral powder, 9 parts of foaming agent, 5 parts of modified carbon fiber and 70 parts of water.

[0058] Step 1, preparation of foaming agent:

[0059] (1) 90 parts of propylene oxide ethylene oxide copolyether polyol (molecular weight 3000) that has been vacuum dehydrated (vacuum dehydration at 110°C for 2 hours) and 43 parts of hexamethylene diisocyanate were mixed and reacted at 70°C for 1.5 hours. Then, 5 parts of a chain extender and 0.03 parts of a catalyst were added and the temperature was kept constant for 1 hour. Then, the temperature was kept at 80°C for 1 hour. The system was cooled to 50°C and then water was added for emulsification to obtain a polyurethane emulsion system.

[0060] The chain extender is a mixture of dimethylolpropionic acid and diethylene glycol in a mass ratio of 2.5:1; and the catalyst is stannous octoate.

[0061] (2) At 60°C, rosin and polyurethane emulsion system were uniformly mixed, then heated to 75°C, 10 parts of silane coupling agent A-171 were added, and the mixture was reacted for 0.5h to obtain a foaming agent;

[0062] The added amount of rosin is 2 times the mass of the raw material hexamethylene diisocyanate; the added amount of the cross-linking agent is 10% of the mass of the rosin.

[0063] Step 2, preparation of modified carbon fiber:

[0064] (1) Add carbon fiber to concentrated nitric acid, heat to 70°C for 1 hour, wash and dry to obtain oxidized carbon fiber;

[0065] (2) Add the oxidized carbon fiber to an ethanol solution of the silane coupling agent KH550 (KH550 mass fraction is 5%), then add dodecylbenzenesulfonic acid and ethylenediamine, and stir and react at room temperature for 20 minutes; then add ethyl orthosilicate and titanium tetrachloride to the system, and stir and react at 45°C for 8 hours; after the reaction is completed, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0066] The mass ratio of the silane coupling agent, the surfactant and ethylenediamine is 2:1:10; the volume ratio of the ethyl orthosilicate, titanium tetrachloride and the ethanol solution is 7:4:100.

[0067] Step 3: Prepare foam lightweight soil material:

[0068] (1) mixing cement, fly ash, mineral powder, modified carbon fiber and water in proportion by mass to obtain a mixture;

[0069] (2) Use a foam generator to foam the foaming agent to obtain a density of 60Kg / m 3 The prefabricated foam is then mixed with the mixture of step (1) to obtain a foamed lightweight soil material.

[0070] Example 3

[0071] The raw material mass proportions of the foamed lightweight soil material of this embodiment are as follows:

[0072] 50 parts of cement, 43 parts of fly ash, 38 parts of mineral powder, 7 parts of foaming agent, 6 parts of modified carbon fiber and 50 parts of water.

[0073] Step 1, preparation of foaming agent:

[0074] (1) 70 parts of propylene oxide ethylene oxide copolyether polyol (molecular weight 2500-3500) that has been vacuum dehydrated (vacuum dehydration at 110°C for 2 hours) and 38 parts of hexamethylene diisocyanate are mixed and reacted at 70°C for 1.5 hours. Then, 7 parts of a chain extender and 0.02 parts of a catalyst are added and the temperature is kept constant for 1 hour. Then, the temperature is kept at 80°C for 2 hours. The system is cooled to 45°C and then water is added for emulsification to obtain a polyurethane emulsion system.

[0075] The chain extender is a mixture of dimethylolpropionic acid and diethylene glycol in a mass ratio of 2.5:1; and the catalyst is dibutyltin dilaurate.

[0076] (2) At 60°C, rosin and polyurethane emulsion system were uniformly mixed, then heated to 70°C, 8 parts of silane coupling agent A-171 were added, and the mixture was reacted for 0.5h to obtain a foaming agent;

[0077] The added amount of rosin is 2.5 times the mass of the raw material hexamethylene diisocyanate; the added amount of the cross-linking agent is 8% of the mass of the rosin.

[0078] Step 2, preparation of modified carbon fiber:

[0079] (1) Add carbon fiber to concentrated nitric acid, heat to 70°C for 1 hour, wash and dry to obtain oxidized carbon fiber;

[0080] (2) Add the oxidized carbon fiber to an ethanol solution of the silane coupling agent KH550 (KH550 mass fraction is 5%), then add dodecylbenzenesulfonic acid and ethylenediamine, and stir the reaction at room temperature for 15-20 minutes; then add ethyl orthosilicate and titanium tetrachloride to the system, and stir the reaction at 50°C for 7 hours; after the reaction is completed, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0081] The mass ratio of the silane coupling agent, the surfactant and ethylenediamine is 2.5:0.8:9; the volume ratio of the ethyl orthosilicate, titanium tetrachloride and the ethanol solution is 6:4:100.

[0082] Step 3: Prepare foam lightweight soil material:

[0083] (1) mixing cement, fly ash, mineral powder, modified carbon fiber and water in proportion by mass to obtain a mixture;

[0084] (2) Use a foam generator to foam the foaming agent to obtain a density of 60Kg / m 3 The prefabricated foam is then mixed with the mixture of step (1) to obtain a foamed lightweight soil material.

[0085] Comparative Example 1

[0086] The only difference from Example 1 is that the carbon fibers are not modified.

[0087] The properties of the foaming agent used in the embodiment of the present invention are shown in Table 1:

[0088] Table 1

[0089] Technical requirements Example 1 Example 2 Example 3 Foaming ratio / times 15-30 27 25 25 Water bleeding rate / % ≤70 33 35 36

[0090] The foaming agent used for foamed lightweight soil needs to have a moderate foaming ratio. A foaming ratio that is too high will affect the stability of the foam, while a foaming ratio that is too low will affect the strength of the foamed lightweight soil. The foaming agent used in the present invention has a moderate foaming ratio, good foam stability, and low water bleeding rate, effectively ensuring the stability of the lightweight soil material during the cementation process and the structural strength.

[0091] The performance of the foamed lightweight soil material prepared by the present invention was verified:

[0092] 1. Standard settlement distance: measured in accordance with JCT2199-2013 "Foaming Agents for Foamed Concrete";

[0093] 2.28d compressive strength: measured using a 100mm×100mm×100mm test sample in accordance with JG / T266-2011 Foamed Concrete;

[0094] 3.28d flexural strength: measured using a 40mm×40mm×160mm test specimen in accordance with JE / T 3420-2020, Test Procedure for Cement and Cement Concrete in Highway Engineering;

[0095] 4. Thermal conductivity: measured in accordance with JG / T266-2011 Foam Concrete;

[0096] 5. Flow value: measured in accordance with CJJ / T177-2012 Technical Specification for Bubble Mixed Lightweight Soil Filling Engineering;

[0097] 6. Dry density, drying shrinkage, and impermeability: Test according to the experimental methods in GB / T29062-2012 "Autoclaved Foam Concrete Bricks and Blocks";

[0098] The performance test results are shown in Table 2.

[0099] Table 2

[0100] Example 1 Example 2 Example 3 Comparative Example 1 Standard settlement distance / mm 2 3 3 4 28d compressive strength / MPa 1.65 1.59 1.60 1.31 28d flexural strength / MPa 1.31 1.24 1.25 0.92 Thermal conductivity / [W / (m*k)] 0.05 0.05 0.06 0.08 Flow value / mm 180 176 182 179 <![CDATA[Dry density (g / m 3 )]]> 558 561 568 664 Drying shrinkage value (mm / m) 0.2 0.2 0.2 0.3 Impermeability / mm 36 38 40 45 <![CDATA[Unit weight (kg / m 3 )]]> 309 310 314 354

[0101] The foamed lightweight soil material prepared by the present invention has the advantages of being lightweight and high-strength, and has a low standard settlement distance, which can significantly reduce the settlement of the road connected to the highway bridge head. The high strength of the material can ensure the stability of the road connected to the highway bridge head. In addition, the foamed lightweight soil material of the present invention has good construction performance and can be constructed in a narrow space. The construction is convenient and efficient, and continuous casting construction is possible.

[0102] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A foam lightweight soil material, characterized in that: The invention comprises the following raw material components in parts by weight: 50-60 parts of cement, 40-45 parts of fly ash, 35-40 parts of mineral powder, 6-9 parts of foaming agent, 5-8 parts of modified carbon fiber and 50-70 parts of water; The preparation method of the foaming agent comprises the following steps: a. The hexamethylene diisocyanate and propylene oxide ethylene oxide copolyether polyol are mixed and reacted, followed by adding a chain extender and a catalyst, and the reaction is performed, and the resulting reaction system is emulsified with water to obtain a polyurethane emulsion; b. The rosin is mixed with the polyurethane emulsion, a crosslinking agent is added, and the reaction is carried out to obtain the foaming agent; The preparation of the modified carbon fiber comprises the following steps: (1) Oxidation treatment of carbon fiber using concentrated nitric acid; (2) The oxidized carbon fiber obtained in step (1), an ionic surfactant, and an ethanol solution of ethylenediamine and a silane coupling agent are mixed, and then ethyl orthosilicate and titanium tetrachloride are added to react. After the reaction is completed, the mixture is filtered, washed, and dried to obtain the modified carbon fiber.

2. The foamed lightweight soil material according to claim 1, characterized in that: The chain extender is a mixture of dimethylol propionic acid and diethylene glycol in a mass ratio of 2.3-2.5:1; the catalyst is dibutyltin dilaurate or stannous octoate; the mass ratio of propylene oxide ethylene oxide copolyether polyol, hexamethylene diisocyanate, chain extender and catalyst is 70-90:30-45:5-12:0.02-0.

03.

3. The foamed lightweight soil material according to claim 1, characterized in that: The temperature of the mixed reaction in step a is 70° C. and the time is 1-1.5 hours; the reaction in step a is: reacting at 70° C. for 1 hour and then keeping warm at 80° C. for 1-2 hours.

4. The foamed lightweight soil material according to claim 1, characterized in that: The added amount of rosin is 2-3 times the mass of the hexamethylene diisocyanate; and the added amount of the cross-linking agent is 8-10% of the mass of the rosin.

5. The foamed lightweight soil material according to claim 1, characterized in that: In step b, the temperature for adding the cross-linking agent is 70-75° C.; in step b, the temperature for the reaction is 70-75° C. and the reaction time is 0.5 h.

6. The foamed lightweight soil material according to claim 1, characterized in that: The reaction conditions in step (2) are: stirring and reacting at 45-50° C. for 7-8 hours; the mass fraction of the silane coupling agent in the ethanol solution of the silane coupling agent is 5%.

7. The foamed lightweight soil material according to claim 6, characterized in that: The mass ratio of the silane coupling agent, the surfactant and ethylenediamine is 2-3:0.8-1:8-10; the volume ratio of the ethyl orthosilicate, titanium tetrachloride and the ethanol solution of the silane coupling agent is 6-7:3-4:

100.

8. The method for preparing the foamed lightweight soil material according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) uniformly mixing the cement, fly ash, mineral powder, modified carbon fiber and water in proportion by mass to obtain a mixture; (2) The foaming agent is foamed by a foam generator to obtain prefabricated foam, and then the prefabricated foam is mixed with the mixture to obtain the foamed lightweight soil material.