Foamed lightweight concrete suitable for long distance pipeline transportation and preparation method thereof

Abstract

The application relates to the field of building materials, and discloses a foamed lightweight concrete suitable for long-distance pipeline transportation and a preparation method thereof. The foamed lightweight concrete suitable for long-distance pipeline transportation comprises slurry and foams; the slurry comprises the following raw materials: cement, fly ash, hydroxypropyl methyl cellulose, polycarboxylic acid superplasticizer and first water; the foams are prepared from a nano-stable foaming agent composition and second water. The foamed lightweight concrete suitable for long-distance pipeline transportation has high fluidity, foam stability and anti-segregation performance, and can solve the problem of material performance degradation in long-distance pipeline transportation of ordinary foamed lightweight concrete.

Description

Technical Field

[0001] This application relates to the field of building materials, and mainly to a foamed lightweight concrete suitable for long-distance pipeline transportation and its preparation method. Background Technology

[0002] With increasing societal emphasis on environmental protection and sustainable development, the construction industry is facing an urgent need to transform towards green building materials. Green building materials must not only possess excellent performance but also minimize their environmental impact during production, use, and disposal. As a promising green building material, the improvement of the performance and technological innovation of foamed lightweight concrete are particularly important.

[0003] Foamed lightweight concrete faces numerous engineering challenges during long-distance pipeline transportation:

[0004] Poor material stability: Traditional foaming agents generate bubbles with low survival rate (<80%), which are prone to breakage during pumping, resulting in uneven density;

[0005] Insufficient pumping performance: Due to the high viscosity of conventional concrete, long-distance pumping can easily clog the pipeline. During long-term pumping operations, the pipeline needs to be cleaned every 2 hours and every 200-300m to ensure smooth pumping.

[0006] High carbon emissions: Traditional processes account for over 60% of cement usage, fly ash replacement rate is less than 30%, and carbon emission intensity reaches 150 kg CO2 / m³. 3 ;

[0007] Low construction efficiency: The layered pouring process is time-consuming, the thickness of a single pour is limited to within 200mm, and the formwork removal cycle is ≥7 days.

[0008] Therefore, developing a high-performance foamed lightweight concrete material and its construction method to meet the needs of long-distance pipeline transportation has become a research hotspot in the current construction field. Consequently, existing technologies still require improvement and development. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this application is to provide a foamed lightweight concrete suitable for long-distance pipeline transportation and its preparation method, aiming to solve the problem of material performance deterioration of existing foamed lightweight concrete in long-distance pipeline transportation (≥500 meters).

[0010] The technical solution of this application is as follows:

[0011] A foamed lightweight concrete suitable for long-distance pipeline transportation, comprising a slurry and a foam group;

[0012] The volume ratio of foam clusters to slurry is 1.67-2.5:1;

[0013] The slurry, by weight, includes the following raw materials:

[0014] 30-50 parts cement, 10-25 parts fly ash, 0.02-0.04 parts hydroxypropyl methylcellulose, 0.08-0.2 parts water-reducing agent, and 25-40 parts first water;

[0015] The foam cluster was prepared from a nano-stabilized foaming agent composition and a second water.

[0016] The mass ratio of the nano-stabilized foaming agent composition to the second water is 1:300-350;

[0017] The nano-stabilized foaming agent composition comprises, by weight parts:

[0018] Polyacrylamide 0.5-5 parts, polyethyleneimine 3-20 parts, polyvinylpyrrolidone 10-20 parts, hydroxypropyl methylcellulose 35-50 parts, triethanolamine 1-5 parts, surface-modified hydrophilic nano-titanium oxide 20-35 parts, surfactant 15-30 parts.

[0019] In this application, the stability and mechanical properties of foamed lightweight concrete are improved through material composition optimization (synergistic foam stabilization of hydroxypropyl methylcellulose and nanoparticles, and dynamic rheological regulation of water-reducing agent), making it suitable for long-distance pipeline transportation.

[0020] The foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the apparent viscosity of the hydroxypropyl methylcellulose is 100,000 - 200,000 mPa·s;

[0021] The water-reducing agent is a polycarboxylate superplasticizer, and the solid content of the polycarboxylate superplasticizer is 50±1%.

[0022] Hydroxypropyl methylcellulose in lightweight foamed concrete reduces the surface tension of the liquid, helping air bubbles to disperse evenly in the slurry. This reduces the likelihood of merging or breaking up of the foamed lightweight concrete during long-distance pipeline transportation. In vertical or inclined construction, it improves the adhesion of the slurry, prevents sagging, and ensures structural stability, primarily improving workability and stabilizing the air bubble structure. Polycarboxylate superplasticizers are used to improve the fluidity of lightweight foamed concrete and enhance its early strength.

[0023] The aforementioned foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the density of the foam aggregate is less than 50 kg / m³. 3 .

[0024] The foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the cement is silicate cement and the fly ash is grade I fly ash.

[0025] The foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the cement is P·II 52.5R silicate cement.

[0026] The aforementioned foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the nano-stabilized foaming agent composition comprises, by weight parts:

[0027] Polyacrylamide 0.8-3 parts, polyethyleneimine 4-15 parts, polyvinylpyrrolidone 12-18 parts, hydroxypropyl methylcellulose 36-45 parts, triethanolamine 2-4 parts, surface hydrophilic modified nano titanium dioxide 22-30 parts, surfactant 16-25 parts.

[0028] The surface-modified hydrophilic nano-titanium oxide is obtained by surface-modifying the nano-titanium oxide with at least one of alkoxylated alkyl diols, alkoxylated alkyl alkynyl diols, and siloxane copolyols.

[0029] The surfactant is selected from at least one of alkoxylated alkyl diols, alkoxylated alkyl alkynyl diols, or siloxane copolyols.

[0030] The aforementioned foamed lightweight concrete suitable for long-distance pipeline transportation, wherein the wet density of the foamed lightweight concrete suitable for long-distance pipeline transportation is 640-830 kg / m³. 3 Dry density is 480-620 kg / m³ 3 .

[0031] A method for preparing foamed lightweight concrete suitable for long-distance pipeline transportation as described above, comprising the following steps:

[0032] S1. The cement, fly ash and hydroxypropyl methylcellulose are mixed evenly to obtain a dry powder material;

[0033] S2. Mix the nano-stabilized foaming agent composition with the second water to obtain a foaming agent solution; after the foaming agent solution is left to stand for 30-40 minutes, a foam group is prepared.

[0034] S3. After the water-reducing agent and the first water are mixed evenly, the mixture is added to the dry powder material obtained in step S1 and mixed evenly to obtain the slurry; the foam group obtained in S2 is stirred and mixed with the slurry to obtain the foamed lightweight concrete suitable for long-distance pipeline transportation.

[0035] The method for preparing foamed lightweight concrete suitable for long-distance pipeline transportation, wherein in step S2, the temperature of the second water is 20-40℃.

[0036] The method for preparing foamed lightweight concrete suitable for long-distance pipeline transportation, wherein, after preparing the foam group in step S2, the method further includes the following steps:

[0037] Weigh the density of the foam cluster; it should be less than 50 kg / m³. 3 The standard is ready for use.

[0038] Beneficial effects: The foamed lightweight concrete of this application, suitable for long-distance pipeline transportation, has high fluidity, bubble stability and anti-segregation properties. The material properties are improved by the synergistic effect of hydroxypropyl methylcellulose in the slurry and nano foaming agent, making it suitable for long-distance pipeline transportation. Attached Figure Description

[0039] Figure 1 This is a fitted curve of the foam drainage rate data of the foam group prepared in Example 1 of this application.

[0040] Figure 2 The images show scanning electron microscope (SEM) images of the foam groups prepared by the nano-stabilized foaming agent in Example 1 of this application and the commercially available common plant protein foaming agent in Comparative Example 1. Detailed Implementation

[0041] This application provides a foamed lightweight concrete suitable for long-distance pipeline transportation and its preparation method. To make the objectives, technical solutions, and effects of this application clearer and more explicit, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0042] This application provides a foamed lightweight concrete (hereinafter referred to as "foamed lightweight concrete") suitable for long-distance pipeline transportation, which is specifically designed for the needs of lightweight, high-strength, and low-cost concrete transportation in municipal engineering, underground utility tunnels and other scenarios. It has high fluidity, bubble stability and anti-segregation performance, and can solve the problem of material performance degradation in long-distance pipeline transportation (≥500 meters) of ordinary foamed lightweight concrete.

[0043] Specifically, the foamed lightweight concrete of this application, suitable for long-distance pipeline transportation, includes slurry and foam aggregate;

[0044] The volume ratio of foam clusters to slurry is 1.67-2.5:1;

[0045] The slurry, by weight, includes the following raw materials:

[0046] 30-50 parts cement, 10-25 parts fly ash, 0.02-0.04 parts hydroxypropyl methylcellulose, 0.08-0.2 parts water-reducing agent, and 25-40 parts first water;

[0047] The foam cluster was prepared from a nano-stabilized foaming agent composition and a second water.

[0048] The mass ratio of the nano-stabilized foaming agent composition to the second water is 1:300-350;

[0049] The nano-stabilized foaming agent composition comprises, by weight parts:

[0050] Polyacrylamide 0.5-5 parts, polyethyleneimine 3-20 parts, polyvinylpyrrolidone 10-20 parts, hydroxypropyl methylcellulose 35-50 parts, triethanolamine 1-5 parts, surface-modified hydrophilic nano-titanium oxide 20-35 parts, surfactant 15-30 parts.

[0051] Preferably, the nano-stabilized foaming agent composition comprises, by weight parts, 0.8-3 parts polyacrylamide, 4-15 parts polyethyleneimine, 12-18 parts polyvinylpyrrolidone, 36-45 parts hydroxypropyl methylcellulose, 2-4 parts triethanolamine, 22-30 parts surface-modified hydrophilic nano-titanium oxide, and 16-25 parts surfactant.

[0052] The surface-modified hydrophilic nano-titanium oxide is obtained by using at least one of alkoxylated alkyl diols, alkoxylated alkyl alkynyl diols, and siloxane copolyols to modify the surface of nano-titanium oxide to be hydrophilic (the specific modification process is a conventional process in this field).

[0053] The surfactant is selected from at least one of alkoxylated alkyl diols, alkoxylated alkyl alkynyl diols, or siloxane copolyols.

[0054] The nano-stabilized foaming agent composition is prepared by directly mixing the components.

[0055] In this application, the surfactant in the nano-stabilized foaming agent composition is the basis of foaming, responsible for efficient foaming and the formation of initial foam as well as reducing surface tension; the surface-hydrophilically modified nano-titanium oxide is the key to achieving nanoscale stability in this composition. The nanoparticles are closely arranged on the bubble surface, forming a strong physical barrier, which greatly enhances the mechanical strength and anti-disturbance ability of the liquid film, effectively prevents bubble coalescence and Oswald ripening (gas diffusion from small bubbles into large bubbles), and significantly improves the long-term stability of the foam. Its hydrophilic modification ensures its good dispersibility in the formulation aqueous solution; the high molecular weight polyacrylamide can significantly increase the viscosity of the aqueous solution after dissolution. High viscosity slows down the drainage rate of liquid in the foam wall (liquid film) (preventing bubble coalescence and rupture), increases liquid film strength, thereby extending foam life and improving foam stability (anti-collapse). Polyethyleneimine, as a high-molecular polymer with a large number of cationic (amino) groups, can attract and adsorb oil droplets, particles, or negatively charged substances in the foam liquid film through electrostatic attraction, neutralizing the charge and reducing the repulsive force that causes foam instability. More importantly, it can form a stronger adsorption layer or composite adsorption layer at the bubble interface (especially when combined with anionic surfactants), increasing the elasticity and mechanical strength of the liquid film and significantly inhibiting liquid film drainage and rupture. Polyvinylpyrrolidone has good water solubility and film-forming properties, and can form on the bubble surface. A protective film with a certain mechanical strength is formed, which can stabilize and disperse other components in the system (such as nanoparticles), prevent their aggregation and sedimentation, and ensure that the nanoparticles are evenly distributed in the liquid film to play their role. Hydroxypropyl methylcellulose, as a non-ionic cellulose ether, mainly provides a thickening effect, which greatly increases the viscosity of the aqueous phase, slows down the drainage rate of the liquid film, has strong water absorption and excellent water retention properties, and can delay the drying and cracking of foam caused by water evaporation. It also has certain surface activity and film-forming properties, which helps to stabilize the liquid film. Triethanolamine, as a pH adjuster, can adjust the pH value of the entire system to a suitable alkaline range. Its weak alkalinity helps the dissolution and stability of cellulose, and it also has certain emulsifying, wetting and foam stabilizing auxiliary effects.

[0056] In this application, silicate cement and fly ash provide cementitious components, while hydration products provide the mechanical properties of the matrix. Fly ash enhances rheological properties and reduces heat of hydration and carbon emissions. Hydroxypropyl methylcellulose in foamed lightweight concrete reduces the surface tension of the liquid, helps air bubbles to disperse evenly in the slurry, and reduces the merging or rupture of foamed lightweight concrete during long-distance pipeline transportation. When constructing on vertical or inclined surfaces, it can improve the adhesion of the slurry, prevent sagging, and ensure the stability of structural forming, mainly improving workability and stabilizing the air bubble structure. Polycarboxylate superplasticizer in foamed lightweight concrete reduces slurry viscosity and improves fluidity, while hydroxypropyl methylcellulose increases the yield stress and thixotropy of the slurry, synergistically regulating rheological properties to ensure the stability and uniformity of air bubbles in foamed lightweight concrete during pumping.

[0057] In this application, the synergistic effect of hydroxypropyl methylcellulose (HMCMC) and the nano-foaming agent is key to improving material performance. HMCMC has excellent thickening, water retention, and bubble stabilization properties, while the nano-foaming agent generates a large number of fine and uniform bubbles. When combined, HMCMC forms a protective film on the bubble surface, effectively preventing bubble rupture and coalescence, thus improving bubble stability. The innovation of this application lies in using HMCMC to increase slurry viscosity, inhibiting bubble rising and water bleeding, and forming an elastic film on the bubble surface through molecular chain adsorption, reducing surface tension differences and resisting film rupture caused by pumping shear force. This breaks the paradox of traditional foamed lightweight concrete: "high fluidity → low viscosity → easy segregation" versus "high viscosity → anti-segregation → poor fluidity." Furthermore, the utilization rate of fly ash solid waste is ≥25%, reducing cement carbon emissions and highlighting the green benefits of the material.

[0058] Furthermore, the cement is silicate cement, and even further, P·II 52.5R silicate cement is used.

[0059] The fly ash is classified as Grade I fly ash. In this application, the amount of fly ash used is 10-25 parts, and the utilization rate of fly ash solid waste is ≥25%.

[0060] In the raw materials of the slurry, the apparent viscosity of hydroxypropyl methylcellulose (HPMC) is 100,000-200,000 mPa·s. In this application, the amount of hydroxypropyl methylcellulose in the slurry is 0.02-0.04 parts. The main functions of HPMC in this application are water retention to delay moisture loss, appropriate thickening effect to ensure uniform foam distribution, and enhanced foam stability to prevent bubble collapse during pipeline transportation and casting.

[0061] In the raw materials of the slurry, the water-reducing agent is a polycarboxylate superplasticizer with a solid content of 50.0±1%. In this application, the dosage of the polycarboxylate superplasticizer is 0.08-0.2 parts. The polycarboxylate superplasticizer is used to improve the fluidity of lightweight foamed concrete and enhance its early strength.

[0062] Furthermore, the density of the foam cluster is less than 50 kg / m³. 3 Excessive foam density can directly lead to insufficient fluidity of foamed lightweight concrete slurry, thus affecting construction performance and reducing the mechanical properties of the product.

[0063] In this application, a composite nano-modified stabilizing foaming agent is used. The foam group produced by the foaming machine has the advantages of low density, high stability, and uniform and closed foam pores. The foamed lightweight concrete prepared using this foam group has the characteristics of higher strength at the same dry density level and lower dry density at the same strength level.

[0064] Furthermore, the foamed lightweight concrete of this application, suitable for long-distance pipeline transportation, has a wet density of 640-830 kg / m³. 3 Dry density is 480-620 kg / m³ 3 .

[0065] This application also provides a method for preparing foamed lightweight concrete suitable for long-distance pipeline transportation, comprising the following steps:

[0066] S1. Cement, fly ash and hydroxypropyl methylcellulose are mixed evenly to obtain dry powder material.

[0067] Specifically, cement, fly ash, and hydroxypropyl methylcellulose can be mixed evenly in the mixer of an integrated machine for 1-2 minutes to obtain a dry powder material.

[0068] S2. Mix the nano-stabilized foaming agent composition with the second water to obtain a foaming agent solution; after letting the foaming agent solution stand for 30-40 minutes, prepare foam clusters using a foaming machine and weigh their density, which should be below 50 kg / m³. 3 The standard is ready for use.

[0069] In step S2, the temperature of the second water is preferably 20-40°C. Too high a water temperature will cause the generated foam to defoam, and too low a water temperature will cause the nano-stabilized foaming agent composition to fail to dissolve completely in the water.

[0070] Furthermore, this foamed lightweight concrete is prepared and pumped using the NJFZY-50 foamed lightweight concrete foaming, mixing, and pumping integrated machine from Shandong Naijiu Industrial Equipment Co., Ltd. The foam produced by the foaming machine of this equipment has the characteristics of lower density, greater uniformity, and stability.

[0071] S3. After mixing the polycarboxylate superplasticizer and the first water evenly, add it to the dry powder material obtained in step S1 and mix evenly to obtain a slurry; mix the foam group obtained in S2 with the slurry to obtain the foamed lightweight concrete suitable for long-distance pipeline transportation of this application.

[0072] Specifically, the first water can be added to the dry powder material obtained in step S1 and mixed evenly for 2-3 minutes to obtain a slurry; then, the foam group obtained in S2 is rapidly stirred and mixed with the slurry in the spiked feeding pipe of the above equipment, and foamed lightweight concrete suitable for long-distance pipeline transportation can be obtained at the outlet of the spiked feeding pipe.

[0073] This application's solution systematically resolves the contradiction between stability and construction efficiency in long-distance pipeline transport of foamed lightweight concrete through material composition optimization (synergistic foam stabilization by hydroxypropyl methylcellulose and nanoparticles, and dynamic rheological control by water-reducing agents). It combines improved mechanical properties, controllable cost, and environmental friendliness, demonstrating significant potential for industrial application. HPMC has thickening and water-retaining effects, while water-reducing agents can reduce the water-cement ratio and improve the fluidity of foamed concrete. The synergistic effect of these two components allows for dynamic rheological control of the water-reducing agent.

[0074] This application also provides a construction method for foamed lightweight concrete suitable for long-distance pipeline transportation, which can be used in conjunction with this foamed lightweight concrete suitable for long-distance pipeline transportation, including the following steps:

[0075] A1. Use high-pressure hoses with a diameter of DN100mm-DN150mm as pumping pipelines;

[0076] A2. Before conveying foamed lightweight concrete, pre-wet the pumping pipeline with a 0.05%-0.15% mass concentration hydroxypropyl methylcellulose aqueous solution to form a lubricating layer on the inner wall of the pumping pipeline, thereby reducing the friction between the foamed lightweight concrete and the inner wall of the pipeline.

[0077] A3. The foamed lightweight concrete is transported to the construction area for pouring through a pumping pipeline. When transporting the foamed lightweight concrete, a hydraulic piston pump is used to transport the foamed lightweight concrete, the pumping pressure is adjusted to 10-15MPa, and the flow rate is controlled at 1.5-2.0 m / s.

[0078] In this application, the pre-wetting process is an important measure to improve the stability of pipeline transportation. Before each operation, the pipeline is pre-wetted with a 0.05-0.15% (w / w) aqueous solution of hydroxypropyl methylcellulose (HPMC) to form a lubricating layer, reducing the friction between the concrete and the inner wall of the pipeline. Using an HPMC aqueous solution within this concentration range results in good viscosity and pipeline lubrication. The HPMC used for pre-wetting is the same as that used in the slurry.

[0079] Specifically, the pre-wetting process of pipelines using HPMC aqueous solution includes the following steps:

[0080] (1) Pipeline pretreatment: First, rinse the inner wall of the pipeline with tap water, and then blow it dry with compressed air to remove oil and particles;

[0081] (2) Solution preparation: Dissolve HPMC in hot water at 50-70℃ to prepare an aqueous solution of HPMC with a mass concentration of 0.05%-0.15%, and cool it naturally to 25±2℃;

[0082] (3) Circulating coating: First, fill the pumping pipe with HPMC aqueous solution, and then circulate the HPMC aqueous solution in the pumping pipe for 2-4 minutes to ensure uniform wetting;

[0083] (4) Drying and film formation: Drain the excess liquid and allow it to dry naturally for 30-45 minutes to form a dense lubricating layer.

[0084] The specific operation of step (3) can be as follows: put the HPMC aqueous solution into the storage tank, connect the inlet of the pumping pipe to the outlet of the storage tank, then place the outlet of the pumping pipe into the storage tank containing the HPMC aqueous solution, pump the pumping pipe to fill it with HPMC aqueous solution, and then continue pumping to circulate the HPMC aqueous solution in the pumping pipe to make the pumping pipe uniformly wet.

[0085] Meanwhile, optimizing pumping parameters, such as controlling pumping speed and pressure (controlling flow velocity to 1.5-2.0 m / s and pumping pressure to 10-15 MPa, enabling a delivery distance of up to 500 meters (the traditional process limit is 300 meters), effectively improves bubble survival rate and pumping efficiency. The selection of pumping pipeline diameter and pressure control also have important engineering logic. If the pipe diameter is too small, it can easily lead to pipe blockage; if the pipe diameter is too large, it will reduce pumping efficiency. Based on experimental results, a pipe diameter of DN100mm-DN150mm is more suitable, with DN150mm being the preferred choice. Regarding pressure control, the pumping pressure is reasonably adjusted according to the delivery distance and height to ensure the smooth delivery of foamed lightweight concrete.

[0086] In existing technologies, the stable pipeline transportation distance for general foamed lightweight concrete is generally within 300m, and traditional processes can also achieve long-distance transportation of 500m. However, beyond 300m, due to high pumping pressure, rough pipe surface and high frictional resistance, ordinary foaming agent foamed lightweight concrete exhibits low bubble survival rate and significant bubble breakage after long-distance transportation, leading to a sharp increase in density at the discharge end, resulting in unstable transportation and unreliable quality. Through performance data verification, the pre-wetting process and optimized pumping parameters in this application achieve a bubble survival rate of ≥90% after 500m pipeline transportation (compared to only 70%-80% for traditional materials). Simultaneously, pre-coating the inner wall of the pipeline with a 0.1% HPMC solution forms a hydrophilic lubricating layer approximately 20-30μm thick. Compared to traditional materials of the same density, this reduces pumping pressure by 20%-30%, eliminates pipe blockage after 2 hours of continuous transportation, improves construction efficiency by 40%, and maintains the lubricating layer's effectiveness for 4 hours, adapting to intermittent construction needs and effectively solving the problem of long-distance pipeline transportation.

[0087] The present application will be further described below through specific embodiments.

[0088] All raw materials used in the following examples are commercially available products. The main sources of the raw materials and equipment used in the following examples are as follows:

[0089] The P·II 52.5R silicate cement was purchased from China Resources Cement (Jiangmen) Co., Ltd., and the model is P·II 52.5R.

[0090] The Grade I fly ash was purchased from Zhongshan Jieanqiao New Material Co., Ltd., and is classified as Class F, Grade I.

[0091] Hydroxypropyl methylcellulose (for slurry, pre-wetting) was purchased from Langfang Longteng New Materials Co., Ltd., model number 100000 mPa·s.

[0092] The polycarboxylate superplasticizer was purchased from Zhongyan Building Materials Technology Co., Ltd., model number DA-100.

[0093] The all-in-one machine was purchased from Shandong Naijiu Industrial Equipment Co., Ltd., model number NJFZY-50.

[0094] Polyacrylamide was purchased from Sinopharm Reagent, specification Acros-178045000.

[0095] Polyethyleneimine was purchased from Sinopharm Reagent, specification MW 70,000, 50% aqueous solution (Wokai).

[0096] Polyvinylpyrrolidone was purchased from Sinopharm Reagent, with an average molecular weight of 220,000 and a K60 rating (Wokai).

[0097] Hydroxypropyl methylcellulose (used as a foaming agent) was purchased from Sinopharm Reagent, type I, viscosity: 30 mPa.s (Wokai).

[0098] The alkoxylated alkyl diols were purchased from: Sinopharm Reagent, 3-methoxy-1,2-propanediol.

[0099] Nano titanium dioxide was purchased from Sinopharm Reagent, with specifications of 99.5% and 500nm (Wokai).

[0100] Triethanolamine was purchased from Sinopharm Reagent, specification Alfa-L04486, 98+.

[0101] Example 1

[0102] The foamed lightweight concrete provided in this embodiment, suitable for long-distance pipeline transportation, consists of the following raw materials in parts by weight:

[0103] P·II 52.5R silicate cement 45.98 parts, grade 1 fly ash 19.71 parts, water 34.16 parts, hydroxypropyl methylcellulose 0.02 parts, polycarboxylate superplasticizer 0.13 parts;

[0104] The apparent viscosity of hydroxypropyl methylcellulose is 100,000 mPa·s.

[0105] The nano-stabilized foaming agent composition comprises the following raw materials in parts by weight:

[0106] 1.3 parts polyacrylamide, 4.5 parts polyethyleneimine, 13 parts polyvinylpyrrolidone, 37 parts hydroxypropyl methylcellulose, 3.5 parts triethanolamine, 23.5 parts nano-titanium oxide with hydrophilic surface modification by alkoxylated alkyl diol, and 17.2 parts alkoxylated alkyl diol.

[0107] The method for preparing foamed lightweight concrete in this embodiment includes:

[0108] Weigh out P·II 52.5R silicate cement, grade I fly ash, and hydroxypropyl methylcellulose and put them into the mixer of the integrated machine and mix for 2 minutes to obtain a mixed dry material; weigh out polycarboxylate superplasticizer and first water and mix them evenly in the water storage tank and then pour them into the mixer and mix them thoroughly with the mixed dry material for 3 minutes to obtain a slurry.

[0109] A foaming agent solution was prepared by mixing a nano-stabilized foaming agent composition with second water (at 29°C) at a mass ratio of 1:330. After standing for 30 minutes, the solution was connected to an integrated foaming machine to produce a foam cluster with a density of 45 kg / m³. 3 ;

[0110] The prepared foam group and slurry are simultaneously pumped into the spiked pipe at a volume ratio of 2.30:1 for rapid mixing. The foamed lightweight concrete suitable for long-distance pipeline transportation in this embodiment is obtained at the outlet of the spiked pipe.

[0111] A 500m long, DN150mm high-pressure hose was used as the pumping pipeline. Before construction, the inner wall of the high-pressure hose was wetted with a 0.1% hydroxypropyl methylcellulose aqueous solution to reduce flow resistance. The specific steps included:

[0112] (1) Pipeline pretreatment: First, rinse the inner wall of the pipeline with tap water, and then blow it dry with compressed air to remove oil and particles;

[0113] (2) Solution preparation: Dissolve HPMC in hot water at 60℃ to prepare an aqueous solution of HPMC with a mass concentration of 0.01%, and cool it naturally to 25±2℃;

[0114] (3) Circulating coating: First, fill the pumping pipeline with HPMC aqueous solution, and then circulate the HPMC aqueous solution in the 500m pumping pipeline for 2-4 minutes to ensure uniform wetting;

[0115] (4) Drying and film formation: Drain the excess liquid and allow it to dry naturally for 40 minutes to form a dense lubricating layer.

[0116] During the pouring process, the inlet of the high-pressure hose is connected to the outlet of the spiked concrete delivery pipe. The outlet of the high-pressure hose is located in the construction area. The foamed lightweight concrete, suitable for long-distance pipeline transportation in this embodiment, is pumped to the construction area for pouring. During construction, the pumping pressure is set to 11.5 MPa, and the flow rate is controlled at 2.0 m / s. Furthermore, samples are taken and retained at the 0m and 500m outlets of the pumping pipeline for future testing.

[0117] Example 2

[0118] The foamed lightweight concrete suitable for long-distance pipeline transportation provided in this embodiment has the same raw material composition of slurry and nano-stabilized foaming agent composition as in Example 1.

[0119] The method for preparing foamed lightweight concrete in this embodiment includes:

[0120] Weigh out P·II 52.5R silicate cement, grade I fly ash, and hydroxypropyl methylcellulose and put them into the mixer of the integrated machine and mix for 2 minutes to obtain a mixed dry material; weigh out polycarboxylate superplasticizer and first water and mix them evenly in the water storage tank and then pour them into the mixer and mix them thoroughly with the mixed dry material for 3 minutes to obtain a slurry.

[0121] A foaming agent solution was prepared by mixing a nano-stabilized foaming agent composition with second water (at 29°C) at a mass ratio of 1:330. After standing for 30 minutes, the solution was connected to an integrated foaming machine to produce a foam cluster with a density of 45 kg / m³. 3 ;

[0122] The prepared foam group and slurry are simultaneously pumped into the spiked pipe at a volume ratio of 1.71:1 for rapid mixing. The foamed lightweight concrete suitable for long-distance pipeline transportation in this embodiment is obtained at the outlet of the spiked pipe.

[0123] A high-pressure flexible hose with a length of 500m and a diameter of DN150mm was used as the pumping pipeline.

[0124] Before construction, the inner wall of the high-pressure hose is wetted with an aqueous solution of hydroxypropyl methylcellulose (0.1% by mass) to reduce flow resistance. The specific steps are the same as in Example 1.

[0125] During the pouring process, the inlet of the high-pressure hose is connected to the outlet of the spiked concrete delivery pipe. The outlet of the high-pressure hose is located in the construction area. The foamed lightweight concrete, suitable for long-distance pipeline transportation in this embodiment, is pumped to the construction area for pouring. During construction, the pumping pressure is set to 12.5 MPa, and the flow rate is controlled at 2.0 m / s. Furthermore, samples are taken and retained at the 0m and 500m outlets of the pumping pipeline for future testing.

[0126] Comparative Example 1

[0127] In Comparative Example 1, the foamed lightweight concrete was identical to that in Example 1, except that a commercially available plant protein foaming agent was used instead of a nano-stabilized foaming agent composition.

[0128] Comparative Example 2

[0129] Comparative Example 2 was identical to Example 1 except that hydroxypropyl methylcellulose was not added to the slurry.

[0130] The drainage rate of the foam group prepared by the nano-stabilized foaming agent in Example 1 was tested, and the results are as follows: Figure 1 As shown, from Figure 1 It can be seen that this foam group possesses excellent stability performance. Experiments revealed a significant time-dependent process in the foam drainage process. In the initial stage (0-10 min), the drainage rate is relatively slow. During this stage, the foam mainly migrates along the thin film within the foam structure under gravity. At this time, the liquid phase content in the foam is low, the gas phase content is high, and the liquid flow resistance is small. Subsequently, a rapid drainage and volume decay period (10-40 min) begins, and the foam gradually enters a "dry foam" state. At this point, the liquid film thickness decreases significantly, and the contact mode between bubbles changes from direct contact to separation through the thin film. The main characteristic of this stage is bubble coarsening, i.e., gas in small bubbles diffuses into larger bubbles, leading to an increase in the average bubble size. In the final stage (60-120 min), bubble merging and rapid volume decay occur. In this stage, the liquid phase in the foam system is almost completely emptied, the liquid film becomes extremely fragile and prone to rupture, and bubble merging becomes the dominant mechanism, leading to rapid foam volume decay. The merging process releases surface free energy, ultimately causing the foam to tend towards complete rupture. In summary, the foam group prepared by this nano-stabilizing foaming agent exhibits good stability and can maintain a stable state for a long time under natural conditions.

[0131] According to JCT 2199-2013 "Foaming Agents for Foamed Lightweight Concrete", the performance of foam groups prepared by the nano-stabilized foaming agent composition in Example 1 and the commercially available common plant protein foaming agent in Comparative Example 1 were tested. The results are shown in Table 1.

[0132] Table 1

[0133]

[0134] In addition, the foam groups prepared by the nano-stabilized foaming agent in Example 1 and the commercially available common plant protein foaming agent in Comparative Example 1 were characterized by scanning electron microscopy (SEM), and the test results are as follows: Figure 2 As shown, (a) is a SEM image of the nano-stabilized foaming agent, and (b) is a SEM image of a commercially available common plant protein foaming agent. Comparative analysis reveals significant differences in the microstructure of the foam groups prepared by the two foaming agents: the foam group prepared by the nano-stabilized foaming agent exhibits a more uniform pore size distribution, with an average pore size significantly lower than that prepared by the commercially available common plant protein foaming agent—the latter has a wider pore size distribution and some macroporous structures, while the former has the vast majority of pores concentrated below 100 μm, with the smallest pore size even reaching tens of micrometers. It is noteworthy that the highly uniform pore size distribution of the nano-stabilized foam group further endows it with an ultra-high specific surface area advantage; this microstructural feature has a positive significance for improving foam stability.

[0135] The performance test results above show that the foam group prepared in Example 1 has excellent performance, which enables the foamed lightweight concrete prepared using this foam group to have excellent pore size and stability, which is directly reflected in its lightweight, high strength and stirring resistance.

[0136] In Examples 1-2 and Comparative Examples 1-2, samples were taken at the 0m and 500m outlets of the pumping pipeline, and their wet density, dry density, flowability, specimen compressive strength, and specimen water absorption rate were tested. The bubble survival rate from 0m to 500m was also calculated. The test results are shown in Table 2.

[0137] Table 2

[0138]

[0139] As shown in Table 2, the wet density increase rates of the foamed lightweight concrete prepared in Examples 1 and 2 for long-distance pipeline transportation were 6.08% and 3.55% respectively from 0m to 500m, and the fluidity loss rates were 11.25% and 12.82% respectively. Furthermore, due to the compression and resistance experienced during the 500m long-distance transportation, a small amount of foam ruptured, leading to an increase in paste density. Correspondingly, the compressive strength increased by 23.47% and 22.60%, and the water absorption decreased by 2.89% and 12.23%. In contrast, the foamed lightweight concrete prepared using a common foaming agent in Comparative Example 1 showed a wet density increase rate and fluidity loss rate as high as 40.30% and 19.16% respectively after 500m long-distance transportation. The long-distance transport of foamed lightweight concrete resulted in unstable quality and reduced workability during construction. Furthermore, the 500m transport distance caused significant foam breakage due to compression and resistance, leading to increased slurry density and a 17.67% increase in compressive strength and a 31.62% decrease in water absorption. In contrast, Comparative Example 2, without hydroxypropyl methylcellulose, showed a 12.91% increase in wet density and an 11.73% decrease in fluidity after 500m transport. The poor foam stability during long-distance transport caused some foam breakage, resulting in increased slurry density, a 31.63% increase in compressive strength, and a 9.08% decrease in water absorption.

[0140] In summary, after a 500m long-distance transport, the bubble survival rates of the foamed lightweight concrete in Examples 1 and 2 reached 94.3% and 96.6%, respectively, while the bubble survival rate of Comparative Example 1, which used a common foaming agent to prepare foamed lightweight concrete, was only 71.2%, and the bubble survival rate of Comparative Example 3, which did not add hydroxypropyl methylcellulose, was 88.6%. The foamed lightweight concrete provided in this application, suitable for long-distance pipeline transport, combines high fluidity, bubble stability, and anti-segregation performance. It not only possesses superior mechanical properties at the same density level but also exhibits higher slurry foam stability during long-distance transport of up to 500m.

[0141] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A foamed lightweight concrete suitable for long distance pipeline transport, characterised in that, The slurry and the foam group are included; The volume ratio of the foam group to the slurry is 1.67-2.5:1; The slurry includes the following raw materials in mass fraction: Cement 30-50 parts, fly ash 10-25 parts, hydroxypropyl methyl cellulose 0.02-0.04 parts, water reducing agent 0.08-0.2 parts, first water 25-40 parts; The foam group is prepared from a nano-stable foaming agent composition and second water; The mass ratio of the nano-stable foaming agent composition to the second water is 1:300-350; The nano-stable foaming agent composition includes the following in mass fraction: Polyacrylamide 0.5-5 parts, polyethylene imine 3-20 parts, polyvinylpyrrolidone 10-20 parts, hydroxypropyl methyl cellulose 35-50 parts, triethanolamine 1-5 parts, surface hydrophilic modified nano titanium oxide 20-35 parts, surfactant 15-30 parts; The apparent viscosity of the hydroxypropyl methyl cellulose in the slurry is 100000-200000 mPa·s; The surface hydrophilic modified nano titanium oxide is obtained by using at least one of alkoxylated alkyl glycol, alkoxylated alkyl acetylenic diol, and siloxane copolyol to perform surface hydrophilic modification on the nano titanium oxide; The density of the foam population is less than 50 kg / m 3 ; The wet density of the foam lightweight concrete suitable for long distance pipeline transportation is 640-830 kg / m 3 , and the dry density is 480-620 kg / m 3 .

2. Foam lightweight concrete suitable for long distance pipeline transport according to claim 1, characterized in that, The water reducing agent is a polycarboxylic acid superplasticizer, and the solid content of the polycarboxylic acid superplasticizer is 50±1%.

3. The foamed lightweight concrete suitable for long distance pipeline transportation according to claim 1, characterized in that, The cement is Portland cement, and the fly ash is first-grade fly ash.

4. Foam lightweight concrete suitable for long distance pipeline transport according to claim 3, characterized in that, The cement is P·II 52.5R Portland cement.

5. The foamed lightweight concrete suitable for long distance pipeline transportation according to claim 1, characterized in that, The nano-stable foaming agent composition includes the following in mass fraction: Polyacrylamide 0.8-3 parts, polyethylene imine 4-15 parts, polyvinylpyrrolidone 12-18 parts, hydroxypropyl methyl cellulose 36-45 parts, triethanolamine 2-4 parts, surface hydrophilic modified nano titanium oxide 22-30 parts, surfactant 16-25 parts; The surfactant is selected from at least one of alkoxylated alkyl glycol, alkoxylated alkyl acetylenic diol, or siloxane copolyol.

6. A method of producing a foam lightweight concrete for long distance pipeline transport according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1, uniformly blending the cement, the fly ash, and the hydroxypropyl methyl cellulose to obtain a dry powder material; S2, mixing the nano-stable foaming agent composition and the second water to obtain a foaming agent solution; after the foaming agent solution is left to stand for 30-40 min, a foam group is prepared; S3, uniformly mixing the water reducing agent and the first water, and then adding the dry powder material obtained in step S1 to obtain the slurry; the foam group obtained in S2 is mixed with the slurry to obtain the foam lightweight concrete suitable for long-distance pipeline transportation.

7. A method of manufacturing foamed lightweight concrete suitable for long distance pipeline transport according to claim 6, characterized in that, In step S2, the temperature of the second water is 20-40℃.

8. A method of manufacturing foamed lightweight concrete suitable for long distance pipeline transport according to claim 6, characterized in that, In step S2, after the foam group is prepared, the following steps are further included: The foam group density is weighed, and conforms to the standard of less than 50 kg / m 3 for standby.

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