High-durability self-compacting lightweight aggregate concrete filled steel tube material and preparation method thereof

Abstract

The invention discloses a high-durability self-compacting lightweight aggregate concrete filled steel tube material, which is prepared from the following components in parts by weight: 997 to 1157 parts of coarse aggregate, 547 to 648 parts of fine aggregate, 321 to 389 parts of cement, 54 to 66 parts of fly ash, 19 to 23 parts of silica fume, 61 to 72 parts of phosphate tailing powder, 32 to 38 parts of efficient anti-cracking expanding agent, 3 to 3.5 parts of water reducing agent and 190 to 210 parts of water, the particle size of the phosphate tailing powder is 5-40 microns, and the density of the phosphate tailing powder is 2.5-3.2 g / cm < 3 >; the invention further discloses a corresponding preparation method. The performance of the novel building material is improved, the technical problems of low shell making efficiency and the like of a traditional preparation process are solved, and secondary utilization of waste materials is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and more specifically, relates to a high-durability self-compacting lightweight aggregate steel tube concrete material and a preparation method thereof. Background Art

[0002] With the rapid development of modern construction technology, steel structures are widely used in the construction field due to their excellent performance. Steel tube concrete, as a composite material that combines the advantages of steel and concrete, has become a popular choice in engineering practice. However, its application also faces many challenges: the closed nature of the steel tube limits the effect of traditional vibration, resulting in insufficient vibration of the concrete, affecting the density and strength; the volume of concrete shrinks when hardening, making it difficult to fit tightly with the steel tube wall, forming cavities or gaps, weakening the constraint effect, becoming a structural weak point, and reducing load bearing and durability. At the same time, traditional steel tube concrete materials have increased construction difficulty and design costs due to their heavy weight.

[0003] In order to solve these problems, the existing technologies often focus on optimizing performance by using a specific material combination or improving the process. For example, industrial waste slag lightweight aggregate is mixed with artificial lightweight aggregate, and its impact on concrete performance is reduced through a specific mixing process; or the strength, fluidity and thermal insulation performance of concrete are improved through the synergistic effect of lightweight aggregate, cementitious materials, water reducers and other components. In addition, there are also stainless steel tube concrete composite columns designed for seismic requirements to improve the ductility and energy dissipation capacity of the structure. However, these solutions generally have a problem: lack of research and explanation of the comprehensive performance of materials or structures. For example, the basic properties and durability of the materials are not evaluated in detail, or the working performance of steel tube concrete is not fully studied, which leads to the lack of practical application orientation of the technology and the inability to fully solve the various problems existing in steel tube concrete. Summary of the invention

[0004] In view of the above defects or improvement requirements of the prior art, the present invention aims to solve the problems in the prior art.

[0005] In order to achieve the above object, according to a first aspect of the present invention, a highly durable self-compacting lightweight aggregate steel tube concrete material is provided, comprising:

[0006] The components are calculated by weight: 997-1157 parts of coarse aggregate, 547-648 parts of fine aggregate, 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water;

[0007] The phosphate tailings powder has a particle size of 5 to 40 μm and a density of 2.5 to 3.2 g / cm 3 .

[0008] Furthermore, the coarse aggregate includes crushed stone and light shale ceramsite in a mass ratio of 1:1, the crushed stone has a particle size of 10 to 25 mm, continuous grading, and a bulk density of 1500 to 1600 kg / m 3 The particle size of the lightweight shale ceramsite is 5 to 15 mm, with continuous grading and a bulk density of 700 to 800 kg / m 3 .

[0009] Furthermore, the fine aggregate is river sand with a particle size of 0.10-4 mm, a fineness modulus of 2.2-2.7, and a bulk density of 1570-1630 kg / m 3 .

[0010] Furthermore, the cement is ordinary Portland cement.

[0011] Furthermore, the fly ash is Class I C fly ash, the particle size of the fly ash is distributed between 0.5 and 2 μm, and the maximum particle size does not exceed 12.8 μm.

[0012] Furthermore, the silica fume ignition loss is 4-7%, and the silica fume water requirement ratio is 95-105%.

[0013] Furthermore, the high-efficiency anti-cracking expansion agent comprises a material compounded by lightly burning CaO and MgO clinker at a mass ratio of 4:1 at high temperature, and has a specific surface area of ​​250-320 m 2 / kg, limiting the expansion rate of the expansion agent in water for 7 days to 0.035-0.045%, and the expansion rate in air for 21 days to 0.005-0.01%.

[0014] Furthermore, the water reducer is a polycarboxylic acid high performance water reducer.

[0015] According to a second aspect of the present invention, a method for preparing a high-durability self-compacting lightweight aggregate steel tube concrete material is provided, characterized in that it comprises the following steps:

[0016] S1, coarse aggregate preparation, each component is calculated by weight, and 498.5 to 578.5 parts of crushed stone and lightweight shale ceramsite are weighed at a mass ratio of 1:1;

[0017] S2, preparation of fine aggregate, each component is calculated by weight, and 547-648 parts of river sand are weighed;

[0018] S3, prepare other raw materials, each component is measured by weight, weigh 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water;

[0019] S4, using cement-wrapped sand and gravel shell mixing process, first add crushed stone, river sand, phosphorus tailings powder and 75-85% mixing water in sequence and stir for 25-35 seconds; after being evenly mixed, add cement, fly ash and silica fume and stir for 25-35 seconds to form a dense low water-cement ratio slurry shell; then add water reducer dissolved in the remaining mixing water and stir for 25-35 seconds; then, while the mixer is continuously working, evenly add pre-wetted lightweight shale ceramsite and stir for 50-70 seconds to form a shell for the mixed aggregate; then add high-efficiency anti-cracking expansion agent in proportion and stir for 60-90 seconds before stopping;

[0020] S5, preparing concrete materials according to the above mix ratio and preparation process, conducting tests to determine the basic mechanical properties and chloride ion permeability at 7d and 28d, and obtaining the highly durable self-compacting lightweight aggregate steel tube concrete material.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0022] 1. The highly durable self-compacting lightweight aggregate steel tube concrete material and preparation method of the present invention use lightweight shale ceramsite and phosphate tailings powder to replace part of the concrete aggregate, which is beneficial to the optimized design of the foundation bearing capacity, and solves the shortcomings of traditional mixed steel tube concrete materials in the construction process, such as large dead weight, large shrinkage deformation, general working performance and durability; effectively eliminates the risk of alkali corrosion reaction in concrete, prolongs the service life of the structure, so that the new building material has better structural strength, self-compacting performance and durability, and at the same time, the matrix compensation shrinkage effect is good.

[0023] 2. The highly durable self-compacting lightweight aggregate steel tube concrete material and preparation method of the present invention utilize cement-wrapped sand and gravel shell-making mixing technology twice, thereby solving the technical problems of the traditional preparation technology such as easy agglomeration, insufficient hydration, and low shell-making efficiency, effectively improving the working performance and volume stability, facilitating the transportation of concrete, and improving the pouring and molding quality.

[0024] 3. The highly durable self-compacting lightweight aggregate steel tube concrete material and preparation method of the present invention can recycle solid wastes such as lightweight shale ceramsite and phosphate tailings powder, solve the problem of tailings solid waste utilization, reduce foundation treatment costs, and produce better environmental protection effects and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A physical picture of lightweight shale ceramsite provided for a preferred embodiment of the present invention;

[0026] Figure 2 A physical picture of the phosphorus tailings powder provided for a preferred embodiment of the present invention;

[0027] Figure 3A physical picture of a high-efficiency anti-cracking expansion agent provided in a preferred embodiment of the present invention;

[0028] Figure 4 A conventional stirring process flow chart provided for a preferred embodiment of the present invention;

[0029] Figure 5 A flow chart of a secondary cement-wrapped sand and gravel shell mixing process provided for a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] The present invention relates to a high-durability self-compacting lightweight aggregate steel tube concrete material, comprising:

[0032] The components are calculated by weight: 997-1157 parts of coarse aggregate, 547-648 parts of fine aggregate, 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water;

[0033] The phosphate tailings powder has a particle size of 5 to 40 μm and a density of 2.5 to 3.2 g / cm 3 .

[0034] Phosphorus tailings powder with smaller particle size has a larger specific surface area, which can increase the contact area with cement hydration products, thereby promoting the hydration reaction and improving the early strength of concrete. It also helps to reduce the permeability of concrete and enhance durability. However, too small a particle size will lead to an overfilling effect. At this time, the phosphorus tailings powder may enter the microscopic pores of cement particles, resulting in the hydration reaction between cement particles being hindered. And phosphorus tailings powder with too small a particle size may absorb too much water, reducing the effective water available for cement hydration, thereby affecting the strength development of concrete.

[0035] If the particle size of phosphorus tailings powder is too large, it may reduce its dispersibility in cement paste and reduce its contact efficiency with cement hydration products, thus affecting the density and strength development of concrete. At the same time, too large a particle size may lead to uneven distribution of phosphorus tailings powder in concrete, increase porosity, and reduce the overall performance of concrete. Based on the above factors, the particle size of phosphorus tailings powder is limited to between 5 and 40 μm.

[0036] If the density of phosphorus tailings powder is too high, it will affect the workability and fluidity of concrete. Lower density helps to reduce the weight of concrete and improve its application performance in the structure, especially in places where the weight needs to be reduced, such as steel tube concrete. If the density of phosphorus tailings powder is too low, it may reduce the density and strength of concrete, and easily lead to segregation or bleeding problems. Based on the above factors, the density of phosphorus tailings powder is finally limited to 2.5-3.2g / cm 3 between.

[0037] Phosphate tailings are mainly waste generated during the mining and processing of phosphate ore. At present, a considerable part of phosphate tailings in my country has been piled up in large quantities due to poor utilization, which not only occupies a large amount of land, but also may cause environmental pollution. Phosphate tailings powder has the potential to replace fine aggregates under proper treatment. Its fineness modulus and main components are similar to those of fine aggregates. The fineness of phosphate tailings powder is controllable, which can improve the fluidity and slump of concrete. The chemical components in phosphate tailings powder, such as aluminum oxide and iron oxide, can strengthen the granular aggregate in concrete, thereby improving the strength and durability of concrete. In addition, the silicate substances in phosphate tailings powder can also react with the silicate cementitious materials in concrete to generate new hydration products, thereby further improving the structure of concrete and enhancing its compressive strength and durability. Through reasonable proportioning and process treatment, phosphate tailings powder can effectively replace part of fine aggregates, reduce the cost of concrete, and improve the comprehensive utilization efficiency of resources. This patent can be used to produce phosphorus tailings powder from Zhangcunping Town, Yiling District, Yichang City, Hubei Province, through a vertical mill high-fine mineral powder production line, with a particle size of 5-40μm and a density of 2.8g / cm 3 , mass coefficient 1.3, specific surface area 420m 2 / kg, the main mineral components are dolomite CaCO3·MgCO3, fluoroapatite Ca5(PO4)3F and quartz SiO2. The specific components are shown in the following table:

[0038]

[0039] The coarse aggregate includes crushed stone and light shale ceramsite in a mass ratio of 1:1. The crushed stone has a particle size of 10 to 25 mm, continuous grading, and a bulk density of 1500 to 1600 kg / m 3 The particle size of the lightweight shale ceramsite is 5 to 15 mm, with continuous grading and a bulk density of 700 to 800 kg / m 3 .

[0040] The crushed stone plays a role in supporting the skeleton and is the main factor determining the strength of concrete. Graded crushed stone is used, and the maximum particle size is not greater than 25mm. After screening, the oversized and smaller particles are removed, and the crushed stone with a continuous particle size of 10mm to 25mm is used. In some preferred embodiments, its basic parameters are as follows:

[0041]

[0042] The lightweight shale ceramsite can effectively replace the consumption of natural materials such as crushed stone, and the price of shale ceramsite is low, which can reduce the mining of natural stone and meet the requirements of green environmental protection. In addition, the ceramsite lightweight aggregate concrete structure is light in weight, which can effectively reduce the amount of steel used in the lower structure of the building and reduce the construction cost. The performance of lightweight aggregate concrete components under dynamic loads exceeds that of ordinary concrete. Its characteristics are that the damping ratio of vibration is quite high, the natural frequency is also high, and the amplitude is relatively low. Therefore, the vibration of this component structure can be suppressed more quickly, thereby showing more outstanding seismic performance. This patent can use 700-grade crushed stone shale ceramsite with a particle size of 5 to 15 mm continuous grading to meet the strength requirements. And pre-wet the lightweight shale ceramsite 24 hours before incorporation. The pre-wetted lightweight aggregate can effectively promote the hydration process of cementitious materials (cement, fly ash, silica fume and phosphorus tailings powder mixture), further strengthen the close bonding between aggregate and cementitious materials, thereby reducing the self-shrinkage of lightweight aggregate. In some preferred embodiments, the basic performance parameters are shown in the following table:

[0043]

[0044] The fine aggregate is river sand with a particle size of 0.10-4 mm, a fineness modulus of 2.2-2.7, and a bulk density of 1570-1630 kg / m 3 It plays an important role in the filling and bonding of cementitious materials. In some preferred embodiments, the basic performance parameters are shown in the following table:

[0045]

[0046] The cement is ordinary Portland cement, which can be Huaxin brand standard ordinary Portland cement, with the label PO42.5, and the basic properties are as follows:

[0047]

[0048] The fly ash is Class I C fly ash, the particle size of the fly ash is distributed between 0.5 and 2 μm, and the maximum particle size does not exceed 12.8 μm.

[0049] The addition of fly ash can effectively reduce alkali-aggregate reaction, improve the impermeability of cement-based materials, and inhibit the diffusion of chloride ions therein. Through laser particle size measurement, it was found that the particle size of fly ash is mainly distributed in the range of 0.5 to 2 μm, and the maximum particle size is 12.8 μm, but large-size fly ash is relatively rare. In some preferred embodiments, 75% of the particle size is mainly distributed in the range of 0.5 to 2 μm. Partially replacing cement with Class I Class C fly ash can not only improve the working performance of the matrix, but also reduce the diffusion of acidic ions and improve durability, while saving cement and fine aggregate and enhancing the early strength of concrete. In some preferred embodiments, the basic performance indicators of fly ash are as follows:

[0050] Fineness / % Loss on ignition / % Water requirement ratio / % Water content / % 25 6 101.5 0.9

[0051] The silica ash ignition loss is 4-7%, and the silica ash water requirement ratio is 95-105%.

[0052] Silica fume can react with cement hydration products to form more hydrated calcium silicate colloids, increasing the strength of concrete. Silica fume can also fill micropores and cracks in cement-based materials, reduce porosity and permeability, and thus improve the durability of concrete. The addition of silica fume can make concrete materials more difficult to segregate and bleed, effectively improve the anti-segregation performance of the matrix, reduce the floating phenomenon of lightweight aggregates and alkali-aggregate reaction, and enhance the stability of the matrix. In some preferred embodiments, the basic performance indicators of silica fume are shown in the following table:

[0053] Fineness / % Loss on ignition / % Water requirement ratio / % Water content / % 25 6 101.5 0.9

[0054] The high-efficiency anti-cracking expansion agent comprises a material compounded by lightly burning CaO and MgO clinker at a mass ratio of 4:1 at high temperature, and has a specific surface area of ​​250-320 m 2 / kg, limiting the expansion rate of the expansion agent in water for 7 days to 0.035-0.045%, and the expansion rate in air for 21 days to 0.005-0.01%.

[0055] The main material of the expansion agent is a compound of CaO and MgO clinkers lightly burned at high temperature in a mass ratio of 4:1. Adding an appropriate amount of expansion agent to the concrete will cause the concrete to expand appropriately through the hydration reaction. Under the constraints of steel bars and adjacent positions, a pre-compression stress of 0.2 to 0.6 MPa is established in the concrete, which can offset the tensile stress generated by part of the concrete shrinkage and control the final shrinkage stress of the concrete within a certain range, thereby preventing the concrete from cracking. At the same time, the calcium aluminate crystals generated by the hydration reaction can fill, block and cut off the capillaries in the concrete, greatly improving the impermeability of the concrete, thereby achieving the purpose of self-waterproofing of the concrete structure. In some preferred embodiments, the specific parameter requirements are as follows:

[0056]

[0057] The water reducing agent is a polycarboxylic acid high performance water reducing agent.

[0058] In some preferred embodiments, HT-100 polycarboxylic acid high-performance water-reducing agent is selected, which has the appearance of a colorless or brown-red transparent liquid, and its main component is a polycarboxylic acid polymer with a molecular weight of 500-5000. This water-reducing agent can greatly increase the early strength of concrete by more than 70%, reduce slump loss, reduce water-cement ratio, improve workability, and enhance durability. Even at high slump, the concrete will not have obvious segregation and bleeding, and the appearance color of the concrete is uniform, which is conducive to the preparation of various types of high-fluidity concrete. When used for high-grade concrete, it has excellent workability and cohesiveness, is easy to stir, and can significantly reduce concrete shrinkage and improve matrix stability and durability. The powder dosage is 0.15-0.25% of the total weight of the cementitious material, and the bulk density is 500-730kg / m 3 , the pH value range is 9 to 11.1.

[0059] The water used is neutral, clean city tap water.

[0060] As another aspect of the present invention, it also relates to a method for preparing a high-durability self-compacting lightweight aggregate steel tube concrete material, comprising the following steps:

[0061] S1, coarse aggregate preparation, each component is calculated by weight, and 498.5 to 578.5 parts of crushed stone and lightweight shale ceramsite are weighed at a mass ratio of 1:1;

[0062] S2, preparation of fine aggregate, each component is calculated by weight, and 547-648 parts of river sand are weighed;

[0063] S3, prepare other raw materials, each component is measured by weight, weigh 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water;

[0064] S4, using cement-wrapped sand and gravel shell mixing process (the shell-forming effect of this mixing process can effectively optimize the microstructure of lightweight aggregate concrete, thereby improving the strength and related properties of concrete), first add crushed stone, river sand, phosphorus tailings powder and 75-85% mixing water in sequence and stir for 25-35 seconds; after being evenly mixed, add cement, fly ash and silica fume and stir for 25-35 seconds to form a dense low water-cement ratio slurry shell; then add the water reducer dissolved in the remaining mixing water and stir for 25-35 seconds; then, while the mixer is continuously working, evenly add the pre-wetted lightweight shale ceramsite and stir for 50-70 seconds to form a shell for the mixed aggregate; then add the high-efficiency anti-cracking expansion agent in proportion and stir for 60-90 seconds before stopping;

[0065] S5, preparing concrete materials according to the above mix ratio and preparation process, conducting tests to determine the basic mechanical properties and chloride ion permeability at 7d and 28d, and obtaining the highly durable self-compacting lightweight aggregate steel tube concrete material.

[0066] Comparative Example 1

[0067] Preparation of C35 strength grade concrete-filled steel tube material

[0068] The concrete material, each component is measured by weight, the coarse aggregate is only 997 parts of crushed stone, the fine aggregate is 720 parts of river sand, 321 parts of cement, 54 parts of fly ash, 19 parts of silica fume, 35 parts of high-efficiency anti-cracking expansion agent, 3.5 parts of polyhydroxy acid water reducer, 190 parts of water (light shale ceramsite is not added to replace crushed stone and phosphorus tailings powder is not added to replace river sand), and the preparation process is as follows:

[0069] Step 1: first add coarse aggregate crushed stone, fine aggregate river sand and 80% mixing water in sequence and stir for 30 seconds;

[0070] Step 2: After the mixture is uniformly mixed, cement, fly ash and silica fume are added and stirred for 30 seconds to form a dense slurry shell with a low water-cement ratio; then the polyhydroxy acid water reducer dissolved in the remaining 20% ​​of the mixing water is added and stirred for 30 seconds;

[0071] Step 3: While the mixer is still working, evenly add the pre-wetted lightweight shale ceramsite and stir for 60 seconds to form a shell for the mixed aggregate;

[0072] Step 4: Add the high-efficiency anti-cracking expansion agent in proportion, stir continuously for 75 seconds and then stop, to obtain the target product.

[0073] Comparative Example 2

[0074] Preparation of C40 strength grade concrete-filled steel tube material

[0075] The concrete material, each component is measured by weight, the coarse aggregate is only 1157 parts of crushed stone, the fine aggregate is 608 parts of river sand, 389 parts of cement, 66 parts of fly ash, 23 parts of silica fume, 35 parts of high-efficiency anti-cracking expansion agent, 3 parts of polyhydroxy acid water reducer, 210 parts of water (lightweight shale ceramsite is not added to replace crushed stone and phosphorus tailings powder is not added to replace river sand), and the preparation process is the same as that of Comparative Example 1.

[0076] Example 1

[0077] Preparation of high-durability self-compacting lightweight aggregate steel tube concrete material with strength grade LC35

[0078] Compared with Comparative Example 1, the concrete material uses lightweight shale ceramsite to replace part of the crushed stone and uses phosphorus tailings powder to replace part of the river sand. The components are measured by weight, and the coarse aggregate is 997 parts of a mixture of lightweight shale ceramsite and crushed stone (the lightweight shale ceramsite accounts for 25% of the total mass of the coarse aggregate), the fine aggregate and phosphorus tailings powder account for 720 parts (the mass of the phosphorus tailings powder accounts for 5%), 321 parts of cement, 54 parts of fly ash, 19 parts of silica fume, 35 parts of a high-efficiency anti-cracking expansion agent, 3.5 parts of a polyhydroxy acid water reducer, and 190 parts of water. The preparation process is as follows:

[0079] Step 1: first add crushed stone, fine aggregate river sand, phosphate tailings powder and 80% mixing water in sequence and stir for 30 seconds;

[0080] Step 2: After the mixture is uniformly mixed, cement, fly ash and silica fume are added and stirred for 30 seconds to form a dense slurry shell with a low water-cement ratio; then the polyhydroxy acid water reducer dissolved in the remaining 20% ​​of the mixing water is added and stirred for 30 seconds;

[0081] Step 3: While the mixer is still working, evenly add the pre-wetted lightweight shale ceramsite and stir for 60 seconds to form a shell for the mixed aggregate;

[0082] Step 4: Add the high-efficiency anti-cracking expansion agent in proportion, stir continuously for 75 seconds and then stop, to obtain the target product.

[0083] Embodiments 2 to 9

[0084] The preparation steps are the same as those in Example 1. In Examples 2 to 9, the components are measured in parts by weight, and the coarse aggregate is a mixture of lightweight shale ceramsite and crushed stone totaling 997 parts, the fine aggregate and phosphate tailings powder are 720 parts, the cement is 321 parts, the fly ash is 54 parts, the silica fume is 19 parts, the high-efficiency anti-cracking expansion agent is 35 parts, the polyhydroxy acid water reducer is 3.5 parts, and the water is 190 parts.

[0085] The only difference between Examples 2 to 9 and Example 1 is the percentage of lightweight shale ceramsite in the total mass of coarse aggregate and the percentage of phosphate tailings powder in the total mass of fine aggregate and phosphate tailings powder.

[0086] In Examples 2 and 3, the phosphorus tailings powder accounts for 5% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounts for 50% and 75% of the total mass of the coarse aggregate, respectively.

[0087] In Examples 4 to 6, the phosphorus tailings powder accounted for 10% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounted for 25%, 50% and 75% of the total mass of the coarse aggregate, respectively.

[0088] In Examples 7 to 9, the phosphorus tailings powder accounted for 15% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounted for 25%, 50% and 75% of the total mass of the coarse aggregate, respectively.

[0089] Example 10

[0090] Preparation of high-durability self-compacting lightweight aggregate steel tube concrete material with strength grade LC40

[0091] Compared with Comparative Example 2, the concrete material uses lightweight shale ceramsite to replace part of the crushed stone and uses phosphorus tailings powder to replace part of the river sand. The components are measured by weight: the coarse aggregate is 1157 parts of a mixture of lightweight shale ceramsite and crushed stone (the lightweight shale ceramsite accounts for 25% of the total mass of the coarse aggregate), the fine aggregate and phosphorus tailings powder account for 608 parts in total (the mass proportion of the phosphorus tailings powder is 5%), 389 parts of cement, 66 parts of fly ash, 23 parts of silica fume, 35 parts of a high-efficiency anti-cracking expansion agent, 3 parts of a polyhydroxy acid water reducer, and 210 parts of water. The preparation process is the same as that of Example 1.

[0092] Examples 11 to 18

[0093] The preparation steps are the same as those in Example 1. In Examples 11 to 18, the components are measured in parts by weight, and the coarse aggregate is a mixture of lightweight shale ceramsite and crushed stone, totaling 1157 parts, the fine aggregate and phosphate tailings powder are 608 parts, the cement is 389 parts, the fly ash is 66 parts, the silica fume is 23 parts, the high-efficiency anti-cracking expansion agent is 35 parts, the polyhydroxy acid water reducer is 3 parts, and the water is 210 parts.

[0094] The only difference between Examples 11 to 18 and Example 10 is the percentage of lightweight shale ceramsite in the total mass of coarse aggregate and the percentage of phosphate tailings powder in the total mass of fine aggregate and phosphate tailings powder.

[0095] In Example 11 and Example 12, the phosphorus tailings powder accounts for 5% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounts for 50% and 75% of the total mass of the coarse aggregate, respectively.

[0096] In Examples 13 to 15, the phosphorus tailings powder accounted for 10% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounted for 25%, 50% and 75% of the total mass of the coarse aggregate, respectively.

[0097] In Examples 16 to 18, the phosphorus tailings powder accounted for 15% of the total mass of the fine aggregate and the phosphorus tailings powder, and the lightweight shale ceramsite accounted for 25%, 50% and 75% of the total mass of the coarse aggregate, respectively.

[0098] The composition table of light shale ceramsite and phosphorus tailing powder in the embodiments 1 to 18 and comparative examples 1 to 2 is as follows: (the mass fraction replacement rate of the light shale ceramsite in the partial replacement of crushed stone refers to the percentage of light shale ceramsite in the total mass of coarse aggregate, and the mass fraction replacement rate of the phosphorus tailing powder in the partial replacement of river sand refers to the percentage of phosphorus tailing powder in the total mass of fine aggregate and phosphorus tailing powder)

[0099]

[0100]

[0101] The working performance, basic mechanical properties and durability of Examples 1 to 18 and Comparative Examples 1 to 2 were tested by the following experiments:

[0102] According to the relevant provisions and requirements of GB / T50080-2016 "Standard for Test Methods of Ordinary Concrete Mixtures", GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" and the rapid chloride ion migration coefficient method (RCM method for short) of the experimental principle of NT Build 492, the basic performance tests were carried out on the concrete materials prepared in Comparative Examples 1 and 2 and Examples 1 to 18. The test contents included concrete working performance (slump, Vebe consistency), 28d cube specimen compressive strength test (150mm 3 cubic specimen), 28d cubic specimen splitting tensile strength test (150mm3 cubic specimen) and 28d / 56d rapid chloride ion migration coefficient method (RAC method, φ100×50mm cylindrical specimen).

[0103] The RCM chloride ion diffusion coefficient method is a test method designed based on the principle that chloride ions in the solution will migrate to the inside of the specimen under the action of an electric field. A concrete cylindrical specimen with a size of φ100×50mm was used and first subjected to a vacuum saturation treatment. The specimen was then placed in a rubber cylinder, 300ml of 0.2mol / L KOH solution was injected into the rubber cylinder (anode), and 0.2mol / L KOH solution containing 5% NaCl was injected into the test tank (cathode). After applying 30V direct current to the specimen, chloride ions will migrate to the inside of the specimen under the action of the electric field. After 24 hours of power-on, the chloride ion diffusion coefficient can be calculated by measuring the penetration depth of chloride ions in the specimen and combining indicators such as time, temperature, current and penetration depth. This coefficient is then used to evaluate the chloride ion diffusion capacity of concrete.

[0104] By quantitatively evaluating and analyzing the chloride diffusion performance of concrete, we can effectively determine the optimal mix design of concrete in a chloride ion corrosion environment to improve its resistance to chloride ion corrosion. In addition, this analysis method can also provide a valuable reference for accurately evaluating the service life of concrete structures. The chloride diffusion coefficient can not only be used as an important parameter for evaluating concrete quality, but also provide basic data for the durability design and service life prediction of concrete structures.

[0105] The following table shows the results:

[0106]

[0107]

[0108] Embodiments 1 to 18 are based on the steel tube concrete materials prepared in Comparative Examples 1 and 2, and 25% to 75% lightweight shale ceramsite and 5% to 15% phosphorus tailings powder are added to replace the original aggregate. The experimental results show that the working performance of the concrete material increases with the increase in the amount of phosphorus tailings powder, and the phenomenon of first increasing and then decreasing occurs. When the amount of phosphorus tailings powder added is 5%, the fluidity of the concrete material is optimal, and the maximum slump of the concrete material with strength grades LC35 and LC40 reaches 241mm and 225mm, respectively, which is 41.8% and 42.4% higher than that of the comparative examples 1 and 2 of the comparison group. After adding lightweight shale ceramsite, the workability of the concrete material is significantly improved, and the anti-segregation ability is improved. Combined with the slump and Vebe consistency of the concrete material, the matrix shows good fluidity and excellent initial workability, and has the basic characteristics of the working performance of self-compacting concrete.

[0109] The addition of lightweight shale ceramsite and phosphate tailing powder effectively improves the compressive strength and splitting tensile strength of the matrix. The silicate substances in the phosphate tailing powder react with the silicate cementitious materials in the concrete to generate new hydration products, thereby further improving the structure of the concrete and enhancing its compressive strength. The addition of other composite auxiliary materials (fly ash, silica fume, and water reducer) has a synergistic effect on the compressive and splitting tensile strength of lightweight aggregate concrete. The maximum 28d compressive strength of lightweight aggregate steel tube concrete with strength grades of LC35 and LC40 reaches 41.04MPa and 47.18MPa, respectively, which is 7.24% and 11.40% higher than that of the control group of comparative examples 1 and 2, respectively. The splitting tensile strength value is proportional to the compressive strength result, which is 0.081 to 0.085 times the compressive strength value. These results show that the material strength grade has been improved by accurately designing the mix ratio, and the LC35 and LC40 mix ratios have improved one strength grade.

[0110] Furthermore, the RCM chloride diffusion coefficient method test was conducted on the examples. Compared with the benchmark specimens, the diffusion depth of chloride ions was significantly reduced when light shale ceramsite and phosphorus tailings powder were added. Moreover, the change of diffusion depth gradually decreased with the increase of age. From the analysis of the change range of the diffusion coefficient value, the chloride ion diffusion coefficient at the age of 28 days was 65×10 -14 m 2 s -1 ~119×10 -14 m 2 s -1 In the range of 56 days, the chloride ion diffusion coefficient is 56×10 -14 m 2 s -1 ~112×10 -14 m 2 s-1 The range is about 5% to 13% compared with 28d. The lowest chloride ion diffusivity test group of 28d concrete decreased by 59.9% and 58.2% compared with control groups 1 and 2, respectively. The low chloride ion diffusivity can effectively inhibit the diffusion of chloride ions and improve the durability of materials and the service life of structures. The key factors that determine the chloride ion diffusion performance are the porosity and micropore distribution inside the matrix. The addition of composite auxiliary materials (fly ash, silica fume, funny anti-cracking expansion agent) and the secondary cement-wrapped sand and gravel shell mixing process effectively compensate for the large porosity of lightweight aggregate.

[0111] In particular, when the lightweight shale ceramsite is substituted at 50% and the phosphorus tailings powder is substituted at 10% (the proportions of each component are shown in the following table), the chloride ion permeability coefficient of the steel tube concrete reaches the lowest value of the test group, and the durability of the matrix is ​​significantly improved. The strength of the above-mentioned Example 6 and Example 15 reaches LC35 and LC40 of the designed mix ratio, respectively, and the working performance meets the characteristics of self-compacting concrete.

[0112]

[0113] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A highly durable self-compacting lightweight aggregate steel tube concrete material, characterized in that: include: The components are calculated by weight: 997-1157 parts of coarse aggregate, 547-648 parts of fine aggregate, 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water; The phosphate tailings powder has a particle size of 5 to 40 μm and a density of 2.5 to 3.2 g / cm 3 .

2. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The coarse aggregate includes crushed stone and light shale ceramsite in a mass ratio of 1:

1. The crushed stone has a particle size of 10 to 25 mm, continuous grading, and a bulk density of 1500 to 1600 kg / m 3 The particle size of the lightweight shale ceramsite is 5 to 15 mm, with continuous grading and a bulk density of 700 to 800 kg / m 3 .

3. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The fine aggregate is river sand with a particle size of 0.10-4 mm, a fineness modulus of 2.2-2.7, and a bulk density of 1570-1630 kg / m 3 .

4. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The cement is ordinary Portland cement.

5. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The fly ash is Class I C fly ash, the particle size of the fly ash is distributed between 0.5 and 2 μm, and the maximum particle size does not exceed 12.8 μm.

6. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The silica ash ignition loss is 4-7%, and the silica ash water requirement ratio is 95-105%.

7. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The high-efficiency anti-cracking expansion agent comprises a material compounded by lightly burning CaO and MgO clinker at a mass ratio of 4:1 at high temperature, and has a specific surface area of ​​250-320 m 2 / kg, limiting the expansion rate of the expansion agent in water for 7 days to 0.035-0.045%, and the expansion rate in air for 21 days to 0.005-0.01%.

8. The highly durable self-compacting lightweight aggregate steel tube concrete material according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid high performance water reducing agent.

9. A method for preparing a highly durable self-compacting lightweight aggregate steel tube concrete material as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: S1, coarse aggregate preparation, each component is calculated by weight, and 498.5 to 578.5 parts of crushed stone and lightweight shale ceramsite are weighed at a mass ratio of 1:1; S2, preparation of fine aggregate, each component is calculated by weight, and 547-648 parts of river sand are weighed; S3, prepare other raw materials, each component is measured by weight, weigh 321-389 parts of cement, 54-66 parts of fly ash, 19-23 parts of silica fume, 61-72 parts of phosphorus tailings powder, 32-38 parts of high-efficiency anti-cracking expansion agent, 3-3.5 parts of water reducer, and 190-210 parts of water; S4, using cement-wrapped sand and gravel shell mixing process, first add crushed stone, river sand, phosphorus tailings powder and 75-85% mixing water in sequence and stir for 25-35 seconds; after being evenly mixed, add cement, fly ash and silica fume and stir for 25-35 seconds to form a dense low water-cement ratio slurry shell; then add water reducer dissolved in the remaining mixing water and stir for 25-35 seconds; then, while the mixer is continuously working, evenly add pre-wetted lightweight shale ceramsite and stir for 50-70 seconds to form a shell for the mixed aggregate; then add high-efficiency anti-cracking expansion agent in proportion and stir for 60-90 seconds before stopping; S5, preparing concrete materials according to the above mix ratio and preparation process, conducting tests to determine the basic mechanical properties and chloride ion permeability at 7d and 28d, and obtaining the highly durable self-compacting lightweight aggregate steel tube concrete material.

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