Runner repairing method based on alkali-activated concrete

Abstract

The invention discloses a runner repairing method based on alkali-activated concrete, the alkali-activated concrete comprises the following raw materials: fly ash, slag and an alkali activator, the alkali activator is a sodium silicate solution formed by mixing Na2O and SiO2, and the weight ratio of fly ash to slag to sodium hydroxide to the sodium silicate solution is (33-45): (187-200): (8-16): (80-100); according to the alkali-activated concrete produced by the invention, the quality and efficiency of runner repair can be improved, the long-term stability and durability of the repaired runner can be ensured, meanwhile, cyclic utilization of resources and environmental protection can be promoted, and the alkali-activated concrete has remarkable economical efficiency and can reduce the engineering repair cost and improve the engineering economic benefit.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to a flow channel repair method based on alkali-activated concrete. Background Art

[0002] In many industrial and construction facilities, flow channel structures play a vital role, such as water delivery channels in water conservancy projects, chemical pipelines, etc. As time goes by and the environment factors affect them, flow channels often suffer from problems such as damage, cracks, and leakage, which seriously affect their normal use functions and bring safety hazards.

[0003] Ordinary Portland cement is currently the most commonly used filling material for repairing flow channels, but its material properties are limited and there are many shortcomings, especially its weak early mechanical properties. Although adding early strength agents, accelerators and other admixtures to ordinary Portland cement concrete can improve its early strength to a certain extent, its setting and hardening time is still slow, and it is difficult to form satisfactory strength within a few hours. It is also easy to crack and has poor adhesion, making it difficult to meet the engineering requirements of repairing flow channel cracks in a short time.

[0004] In contrast, alkali-activated concrete shows unique advantages in flow channel repair. Alkali-activated concrete has higher durability due to its special material composition and reaction mechanism. In complex flow channel environments, such as long-term water erosion, chemical erosion, and temperature changes, alkali-activated concrete can better maintain its structural integrity and reduce performance degradation caused by environmental factors. It has low permeability and can effectively prevent the intrusion of liquids and gases, which is crucial for flow channel repair, preventing leakage and ensuring the sealing of the flow channel.

[0005] At the same time, the early strength development of alkali-activated concrete is relatively fast, which can shorten the waiting time for use after the flow channel is repaired and improve the engineering efficiency. In addition, the shrinkage of alkali-activated concrete is relatively small, which reduces the risk of cracks caused by shrinkage, thereby improving the structural stability of the flow channel after repair. Therefore, it is of great practical significance to develop a new flow channel repair method based on alkali-activated concrete. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide an alkali-activated concrete.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions: an alkali-activated concrete is provided, characterized in that the raw materials of the alkali-activated concrete are fly ash, slag and an alkali activator, and the alkali activator is Na 2 O and SiO 2 The mixed water glass solution, the weight ratio of each component of the concrete is fly ash: slag: sodium hydroxide: water glass solution = 30-35: 180-190: 5-10: 75-85.

[0010] Another object of the present invention is to overcome the deficiencies in the prior art and provide a flow channel repair method based on alkali-activated concrete.

[0011] As a preferred embodiment of the flow channel repair method of the present invention, the method comprises:

[0012] Flow channel surface treatment: clean the flow channel surface, remove dirt and loose particles on the surface, and ensure that the flow channel surface is clean and flat with a certain degree of roughness;

[0013] Preparation of slurry: first mix sodium hydroxide with water glass solution, cool to room temperature to prepare alkali activator, then mix with fly ash and slag, add to mixer and stir to form slurry until concrete is evenly mixed;

[0014] Fill the slurry into the damaged part of the flow channel and vibrate it to make it dense, ensuring that the concrete is tightly combined with the original flow channel structure without any gaps;

[0015] Maintenance: After laying the concrete in the flow channel, the repaired flow channel surface is smoothed and maintained for 14 to 18 days.

[0016] As a preferred embodiment of the flow channel repair method of the present invention, the fly ash is the fine ash collected from the flue gas after coal combustion, which is the main solid waste discharged from coal-fired power plants; the slag is granulated blast furnace slag; the alkali activator is 8.2% Na 2 O and 26% SiO 2 Mix the water glass solution.

[0017] As a preferred embodiment of the flow channel repair method of the present invention, the density of the fly ash is 2.1 to 3.5 g / cm 3 , bulk density is 1.10~2.9g / cm 3 .

[0018] As a preferred embodiment of the flow channel repair method of the present invention, the specific surface area of ​​the slag is 429m 2 / kg, flow ratio is 98%, activity index 7d is 84.20%, activity index 28d is 98.50%, density is 3.10g / cm 3 , loss on ignition is 0.84, and water content is 0.45.

[0019] As a preferred embodiment of the flow channel repair method of the present invention, the alkaline activator is 8.2% Na 2 O and 26% SiO 2 The mixed water glass solution has a ratio of sodium hydroxide to the water glass solution in the alkaline activator of 1:10-15.

[0020] As a preferred solution of the flow channel repair method of the present invention, in the slurry preparation, the concrete is mixed evenly, has a uniform color, and has no obvious caking phenomenon.

[0021] As a preferred embodiment of the flow channel repair method of the present invention, the slurry is filled into the damaged part of the flow channel by pumping or manual pouring, and is vibrated and compacted by tools such as vibrators to ensure that the concrete is tightly combined with the original flow channel structure without gaps, and the paved thickness is 15 to 20 mm.

[0022] As a preferred embodiment of the flow channel repair method of the present invention, the curing is carried out in a stable environment with a temperature of 20±2° C. and a relative humidity greater than 95% for 14 to 18 days.

[0023] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of alkali-activated concrete in flow channel repair.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention innovatively uses fly ash and slag as the main raw materials. Fly ash, as an industrial waste, has rich volcanic ash activity and can react with alkali activators to form hydration products with high strength. Slag can deeply change the hydration reaction process of concrete and improve the tensile properties and overall strength of concrete.

[0026] 2. By adding fly ash and slag, the concrete mixture of the present invention exhibits excellent flow characteristics, making it easier for concrete to fill the damaged part of the flow channel to form a uniform repair layer. At the same time, the reaction product of fly ash and slag can effectively improve the performance of the interface transition zone (ITZ), reduce microcracks and pores in this area, and improve the overall strength and durability of concrete.

[0027] 3. Alkali activators can quickly drive the hydration reaction in concrete, accelerate the reaction speed of active ingredients in fly ash and slag, and thus generate more hydration products. These hydration products can not only fill the pores in concrete and increase the density of concrete, but also form a tight skeleton structure and improve the strength of concrete.

[0028] 4. The raw materials used in the repair method of the present invention are widely available and have low cost. Fly ash and slag are industrial wastes with relatively low prices, which promote resource recycling and environmental protection. Although the cost of alkaline activators is slightly higher, the amount used is small and the impact on the overall cost is limited. Therefore, the repair method of the present invention has significant cost-effectiveness, can reduce the cost of engineering repair, and improve the economic benefits of engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0030] Figure 1 This is a splitting tensile strength analysis diagram of the alkali-activated concrete paste and the interface transition zone in Example 1 of the present invention.

[0031] Figure 2 This is a microhardness analysis diagram of the alkali-activated concrete paste and the interface transition zone in Example 1 of the present invention.

[0032] Figure 3 The pore size distribution of the interface transition zone of the alkali-activated concrete in Example 1 of the present invention changes with age.

[0033] Figure 4 This is the XRD diffraction pattern of the ITZ of the alkali-activated concrete interface in Example 1 of the present invention as it changes with age.

[0034] Figure 5 This is a scanning electron microscope image of the surface of the alkali-activated concrete paste in Example 1 of the present invention at 2000 times magnification.

[0035] Figure 6 This is a scanning electron microscope image of the surface of the alkali-activated concrete paste in Example 1 of the present invention at a magnification of 5000 times. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0037] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0039] Raw materials and reagents in the present invention: The slag used in this test is S95 grade slag produced by Gongyi Longze Water Purification Material Co., Ltd. This test uses fly ash (FA) produced by Gongyi Borun Co., Ltd., with a median particle size of D50 = 19.7 μm and a specific surface area of ​​480 m 2 / kg, Class F, Level I. The NaOH used in the test was a commercially available solid NaOH produced by Shanghai Wokai Biotechnology Co., Ltd., in white granular form with a content of 96.0%. The water glass (Na 2 O·nSiO 2 ·rH 2 O) Commercially available industrial grade liquid sodium silicate produced by Shandong Yousuo Chemical Co., Ltd., with a content of 34%, and water glass containing 26.5wt% SiO 2 and 8.3 wt% Na 2 O.

[0040] Example 1

[0041] The invention discloses alkali-activated concrete, which is prepared from the following raw materials in parts by weight: 33 parts of fly ash, 187 parts of slag, and 88 parts of alkali activator (containing 9.09% sodium hydroxide and 90.91% water glass solution).

[0042] Preparation method: prepare materials in a weight ratio of fly ash: slag: sodium hydroxide: water glass solution = 33:187:8:80 (W / B = 0.4, CH = 85%) and mix them to form alkali-activated concrete.

[0043] The repair method of the flow channel is as follows:

[0044] (1) Flow channel surface treatment: Clean the flow channel surface to remove dirt and loose particles on the surface to ensure that the flow channel surface is clean and flat with a certain degree of roughness.

[0045] (2) Slurry preparation: Prepare the materials in a weight ratio of fly ash: slag: sodium hydroxide: water glass solution = 33:187:8:80. First, mix the sodium hydroxide and water glass solution, cool to room temperature to prepare an alkali activator, and then mix with the fly ash and slag. Add the mixture into a mixer and stir to form a slurry until the concrete is evenly mixed, has a uniform color, and has no obvious caking.

[0046] (3) The slurry is pumped or poured manually into the damaged part of the flow channel, and vibrated and compacted using tools such as vibrators to ensure that the concrete is tightly combined with the original flow channel structure without any gaps. The paved thickness is about 15 mm.

[0047] (4) Maintenance: After laying the concrete in the flow channel, the repaired flow channel surface is smoothed and provided with a stable environment with a temperature of 20±2℃ and a relative humidity greater than 95% for 14 days of maintenance.

[0048] Example 2

[0049] In this test, the WAW-Y1000C universal testing machine was used to test the mechanical properties of the specimen. During the test, the specimen was first taken out of the curing box and accurately placed in the center of the lower platen of the testing machine. In the initial stage of the test, if it is found that the upper platen and the specimen are not parallel when they are about to contact, the test should be stopped immediately and the ball seat of the testing machine should be quickly adjusted to ensure that the upper platen and the specimen can contact smoothly and evenly to ensure that the specimen is evenly stressed during the entire test. Subsequently, the loading speed was set to 0.3MPa / s on the microcomputer control end to ensure a steady increase in load. When the specimen shows obvious crack expansion and the peak load drops rapidly, the test should be stopped in time and the throttle should be closed to cut off the pressure transmission. At the same time, the maximum load reached during the test, that is, the peak stress, is recorded. This value is an important indicator for evaluating the compressive performance of the specimen.

[0050] Figure 1 The results show that the splitting tensile strength of the alkali-activated concrete paste and the interface transition zone increases with the increase of curing time, especially from the initial curing period to the 7th day, the growth of splitting tensile strength is particularly significant; and after the 7th day, the hydration reaction inside the material continues, the cement clinker reacts chemically with water to generate hydration products and gradually fill the pores and cracks inside the material, thereby improving the density and strength of the material. As the hydration reaction is gradually completed, the material structure tends to be stable, and the growth rate of splitting tensile strength also slows down, indicating that the material performance has stabilized.

[0051] Example 3

[0052] In this test, a manual disk automatic turret microhardness tester (HV-1000Z) is used for testing, that is, a micrometer-sized diamond cone is pressed on the surface of the material to obtain the micromechanical properties of the sample. At the beginning of the test, the specimen is first removed from the curing box and the surface of the specimen is made clean and flat. Then, the appropriate test force is selected according to the characteristics of the specimen, and the focal length of the microhardness tester is adjusted to ensure that the specimen is clearly visible in the field of view. Then, the test force is applied, and the instrument will automatically complete the process of loading, holding and unloading. After unloading, turn the objective lens to the appropriate position, measure the diagonal length of the indentation through the micrometer eyepiece, and enter the value to calculate the hardness value.

[0053] Figure 2 The effect of alkali on the microhardness of the concrete paste and the interface transition zone was studied. The results showed that with the gradual increase of curing time, the microhardness also showed a steady upward trend. During the first 7 days of the curing process, that is, from the 3rd day (3d) to the 7th day (7d), the hydration reaction was most active, resulting in the gradual densification of the internal structure of the material and the most significant increase in microhardness; then, from the 7th day, although the microhardness continued to increase, the growth rate gradually slowed down, indicating that the material performance tended to be stable.

[0054] Figure 3 The pore size distribution of the interface transition zone changes with age. It was observed that the contact surface showed a trend of total pore volume increasing first and then decreasing. The progress of hydration reaction: As the reaction deepens, the larger pores are first filled with hydration products. Then, as the hydration reaction continues, the formed hydration products can fill the pores more effectively, resulting in a decrease in the total pore volume. However, as the age increases, the incompletely reacted cement and slag continue to hydrate. Since the water content is relatively insufficient at this time, the new products produced by the hydration reaction cannot fully fill the pores. Instead, new pores will be formed due to water evaporation or migration, causing the total pore volume to increase again. This phenomenon is different from normal concrete, and is particularly significant in alkali-activated concrete, because the alkali activator can accelerate the hydration reaction, promote the formation of hydration products and the filling of pores.

[0055] Figure 4 The XRD diffraction pattern of the ITZ of the alkali-activated concrete interface changes with age. The hydration products of the cementitious materials prepared by alkali-activated slag / fly ash mainly include Friendel's salt, Ettringite, Tobermorite, α-SiO 2(α-quartz), and CSH / CASH gel. As the water-cement ratio decreases, the "hump" of CSH / CASH gel changes significantly, and the main characteristic peak of Tobermorite at 29.2° is significantly enhanced. This is because the reduction of the water-cement ratio means a reduction in the water content in the system, which promotes the crystallization and aggregation of hydration products, increases the generation of crystals such as tobermorite, and also makes the gel structure more compact and stable, thereby improving the strength of the material.

[0056] In summary, from the test results, it can be seen that the alkali-activated concrete of the present invention can improve the quality and efficiency of flow channel repair, ensure the long-term stability and durability of the flow channel after repair, and at the same time can promote the recycling of resources and environmental protection, has significant economy, can reduce the cost of engineering repair, and improve the economic benefits of the project.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the solid phase components are replaced by 33:187:10:100 (W / B=0.5, CH=85%). Figure 1 and Figure 2 It can be seen that when the dosage remains unchanged and the water-cement ratio is used as a variable, the study reveals the inverse relationship between the water-cement ratio and the microhardness: that is, the smaller the water-cement ratio, the greater the microhardness. This may be because a lower water-cement ratio means less free water in the material, which is conducive to the formation of a denser and stronger microstructure. At the same time, in terms of positional differences, although the slurry area still maintains the highest hardness, the microhardness of the interface transition zone is about 60% of that of the slurry area at this time. This change may be related to the hydration reaction rate, water migration and microstructure formation mechanism.

[0059] When the slag content remains unchanged and the water-cement ratio is used as a variable factor, the change in splitting tensile strength shows a more complex trend. In the paste area and the interface transition area, reducing the water-cement ratio has a positive effect on the improvement of splitting tensile strength. This may be because these two areas are relatively less sensitive to moisture changes, and a smaller water-cement ratio helps to build a more compact microstructure.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the content of the solid phase components is 33:77:5:50 (W / B=0.5, CH=70%). Figure 1 and Figure 2It can be seen that when the water-cement ratio remains unchanged and the slag content is used as a variable, the increase in the content has a significant positive effect on the splitting tensile strength. This shows that the addition of an appropriate amount of slag helps to improve the tensile properties of the material, probably because the admixture plays a reinforcing role in the material and improves the overall strength of the material. At the same time, in terms of position differences, the splitting tensile strength of the slurry area always maintains the highest level, significantly higher than the interface transition zone.

[0062] When the water-cement ratio remains unchanged and the dosage is used as a variable, the increase in the dosage ratio directly promotes the improvement of microhardness. This shows that the addition of an appropriate amount of dosage can significantly improve the microstructure of the material and enhance its mechanical properties. At the same time, in the comparison of different positions, the microhardness of the slurry area always maintains the highest level, significantly higher than the interface transition zone. Specifically, at the 14th day (14d), the microhardness of the interface transition zone is about 40% of that of the slurry area, which reflects that the interface transition zone is a relatively weak link inside the material and its hardness performance is relatively poor.

[0063] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An alkali-activated concrete, characterized in that: The raw materials of the alkali-activated concrete are fly ash, slag and alkali activator, the alkali activator is a water glass solution mixed with Na2O and SiO2, and the weight ratio of the components of the concrete is fly ash: slag: sodium hydroxide: water glass solution = 30-35: 180-190: 5-10: 75-85.

2. A flow channel repair method based on alkali-activated concrete, characterized in that: include, Flow channel surface treatment: clean the flow channel surface, remove dirt and loose particles on the surface, and ensure that the flow channel surface is clean and flat with a certain degree of roughness; Preparation of slurry: first mix sodium hydroxide with water glass solution, cool to room temperature to prepare alkali activator, then mix with fly ash and slag, add to mixer and stir to form slurry until concrete is evenly mixed; Fill the slurry into the damaged part of the flow channel and vibrate it to make it dense, ensuring that the concrete is tightly combined with the original flow channel structure without any gaps; Maintenance: After laying the concrete in the flow channel, the repaired flow channel surface is smoothed and maintained for 14 to 18 days.

3. The flow channel repair method according to claim 1, characterized in that: The fly ash is fine ash collected from the flue gas after coal combustion and is the main solid waste discharged from coal-fired power plants; the slag is granulated blast furnace slag; and the alkali activator is a water glass solution mixed with 8.2% Na2O and 26% SiO2.

4. The flow channel repair method according to claim 2 or 3, characterized in that: The fly ash density is 2.1-3.5 g / cm 3 , bulk density is 1.10~2.9g / cm 3 .

5. The flow channel repair method according to claim 2 or 3, characterized in that: The specific surface area of ​​the slag is 429m 2 / kg, flow ratio is 98%, activity index 7d is 84.20%, activity index 28d is 98.50%, density is 3.10g / cm 3 , loss on ignition is 0.84, and water content is 0.

45.

6. The flow channel repair method according to claim 2 or 3, characterized in that: The alkaline activator is a water glass solution mixed with 8.2% Na2O and 26% SiO2, and the ratio of sodium hydroxide to the water glass solution in the alkaline activator is 1:10-15.

7. The flow channel repair method according to claim 2, characterized in that: In the slurry preparation, the concrete is mixed evenly, has a uniform color, and has no obvious caking phenomenon.

8. The flow channel repair method according to claim 2, characterized in that: Fill the slurry into the damaged part of the flow channel by pumping or manual pouring, and use tools such as vibrators to vibrate and compact it to ensure that the concrete is tightly combined with the original flow channel structure without any gaps. The paving thickness is 15 to 20 mm.

9. The method for preparing a macromolecular cross-linking agent according to claim 2, characterized in that: During the curing, the temperature is 20±2° C. and the relative humidity is greater than 95% in a stable environment for 14 to 18 days.

10. Use of the alkali-activated concrete according to claim 1 in flow channel repair.

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