CN101007715A - High anti-penetration concrete mixing material for tunnel shield tube plate and its preparation method - Google Patents

Abstract

The invention relates to a shield segment concrete admixture and a preparation method thereof. Shield segment high impermeability concrete admixture is characterized in that it is mainly prepared by mixing and grinding slag, fly ash, silica fume and function adjustment component raw materials, and the mass percentage of each raw material is: slag 25%- 40%, fly ash 40%-50%, silica fume 15%-25%, function adjustment components 3%-6%; the function adjustment components are reinforcing agent, waterproofing agent and toughening agent, reinforcing agent, waterproofing agent The mass percent of the functional adjustment component accounted for by the agent and the toughening agent is as follows: 36-40 percent of the reinforcing agent, 48-51 percent of the waterproofing agent, and 10-15 percent of the toughening agent. The shield segment high impermeability concrete admixture of the invention is used in the shield segment concrete, can improve the impermeability and the demoulding strength can meet the needs of the shield segment production.

Description

Shield segment high impermeability concrete admixture and preparation method thereof

technical field

The invention relates to a shield segment concrete admixture and a preparation method thereof.

Background technique

With the development of urbanization in our country, urban traffic is also developing in a three-dimensional direction. As a part of three-dimensional transportation, underground tunnels will play an important role in alleviating traffic congestion in cities in our country. Underground tunnels require concrete as a structural component to have good impermeability; at the same time, the shield tunneling method is the mainstream technology of tunnel engineering, and the shield segment is its most important and critical structural component. Therefore, the impermeability of shield segment concrete will directly affect the quality of the tunnel and its service life.

For the shield segments, measures to improve the impermeability of the segments are divided into two categories: one is to paint waterproof materials on the water-facing surface of the segments. The waterproof materials are generally organic components, and organic materials are better than ordinary materials in waterproof Inorganic non-metallic materials, but the disadvantages of using organic materials are also obvious. The organic materials and the concrete constituting the segments belong to different material systems, and their interface effects cannot be ignored; in addition, the organic materials are easy to age and cause the waterproof treatment to fail, so that the segments can serve safely Life is limited by it. The second is to use self-waterproof concrete. Self-waterproof is to improve the impermeability of the segment structure material body. The technical measure is to add an expansion agent to the concrete to fill the pore structure of the concrete by generating ettringite crystals to improve the compactness of the concrete. . However, the ettringite crystal volume generated by the expansion agent will expand, which will affect the volume stability of the concrete and reduce the durability of the concrete; or add a waterproofing agent to the concrete. The waterproofing agent generally uses inorganic materials such as chlorine salt waterproofing agent and water glass. Waterproofing agent, both of which will introduce harmful ions (sodium ions and chloride ions) into concrete. At present, to improve the impermeability of concrete, the technical means generally used are single or double mixed auxiliary cementitious materials (such as fly ash, slag , silica fume), optimize the aggregate gradation and reduce the water-cement ratio to achieve. The core of these technical means is to start with improving the pore structure of concrete and reducing the weak interface of concrete. For example, fly ash is used as a pozzolanic material, and its secondary hydration reaction can fill the gel pores, and its micro-aggregate effect can also be reduced. It can effectively block the connected capillary pores in the system; slag can react with Ca(OH) ₂ formed by cement hydration, which can break the directional arrangement of Ca(OH) ₂ and reduce the interface weak area; the micro-aggregate filling effect of silica fume, Seeding can greatly improve the compactness of the gelling system and reduce the size of Ca(OH) ₂ crystals, etc. The shield segment is a prefabricated component, and its curing system is steam curing, which requires high early strength of the segment (the demoulding strength must be greater than 15MPa). The premise is the dosage (fly ash is generally about 30%, and the mineral powder dosage is higher), although the dosage of silica fume is small (5%-8%), silica fume will increase the early self-shrinkage of concrete, resulting in microcracks. The addition of auxiliary cementitious materials will reduce the amount of primary hydration phase cement and affect the release strength. The requirements for release strength will inevitably limit the amount of the secondary hydration phase in the material component. Therefore, using the traditional technical route of configuring high-performance concrete to prepare high-impermeability concrete for shield segments will not be able to meet engineering requirements.

Contents of the invention

The object of the present invention is to provide a shield segment high impermeability concrete admixture with high impermeability and a preparation method thereof, whose demoulding strength can meet the needs of shield segment production.

In order to achieve the above object, the technical solution adopted in the present invention is: shield segment high impermeability concrete admixture, which is characterized in that it is mainly prepared by mixing and grinding slag, fly ash, silica fume and function adjustment component raw materials The mass percentage of each raw material is: 25%-40% of slag, 40%-50% of fly ash, 15%-25% of silica fume, 3%-6% of function adjustment components; wherein the function adjustment components are Strengthening agent, waterproofing agent and toughening agent, the mass percentage of reinforcing agent, waterproofing agent and toughening agent in the function adjustment component is: 36-40% of strengthening agent, 48-51% of waterproofing agent, 10-15% of toughening agent .

The reinforcing agent is formed by compounding ferric nitrate and calcium sulfate in a mass ratio of 1:1-2.

The waterproofing agent is a cement-based permeable crystalline waterproofing material (powder).

The toughening agent is a hybrid fiber, and the hybrid fiber is compounded by a modified polypropylene fiber of 3mm and a modified polypropylene fiber of 10mm, and the quality of the modified polypropylene fiber of 3mm and the modified polypropylene fiber of 10mm is The ratio is (1-2):1. The surface of polypropylene fiber needs to be modified to enhance its grip with the gelling system.

The specific surface area of the fly ash is greater than 4500cm ² /g, and its performance should meet the requirements of the GB1596-2005 standard.

The preparation method of the above-mentioned shield segment high impermeability concrete admixture is characterized in that it comprises the following steps:

1) According to the mass percentage of each raw material: 25%-40% of slag, 40%-50% of fly ash, 15%-25% of silica fume, 3%-6% of functional adjustment components, select slag and fly ash , silica fume, and function-adjusting component raw materials, wherein the function-adjusting component is a reinforcing agent, waterproofing agent and toughening agent, and the mass percentage of the function-regulating component accounted for by the reinforcing agent, waterproofing agent, and toughening agent is: reinforcing agent 36-40 %, waterproofing agent 48-51%, toughening agent 10-15%;

2) Mix the silica fume and the toughening agent in advance to disperse the fibers;

3) Mix and grind slag, reinforcing agent and waterproofing agent until the specific surface area is ≥ 4500cm ² /g, then add fly ash and mix and grind, then add prefabricated silica fume and toughening agent and mix and grind evenly to obtain the product.

The use method of the shield segment high impermeability concrete admixture provided by the present invention is that, in the process of preparing concrete, 30%-50% of the shield segment high impermeability concrete admixture is used to replace cement in an equivalent amount according to the weight ratio .

The features of the present invention are:

1. Designed according to the specific requirements of the shield segment, it can meet the needs of the actual production process of the shield segment, specifically reflected in: considering the production method of the shield segment, it can provide sufficient demoulding strength; for the shield segment According to the environment characteristics of the shield segment, the key point is to meet the anti-seepage requirements of the shield segment.

2. The impermeability can be achieved step by step, that is, the primary filling of the micro-aggregate effect of the mineral admixture, the filling of the pores of the cementitious material system by the hydration product of the secondary hydration phase, and the cement-based permeable crystalline material in the entire system Dispersed, it can react with water to form crystals to fill pores and achieve long-term anti-seepage effect.

3. The nano-size effect of silica fume can greatly increase the compactness of concrete, thereby improving the impermeability of concrete, but silica fume reduces the cohesion of the system, and will cause microcracks during the hydration reaction process, providing The rapid passage of water and harmful ions is ensured, and the addition of toughening agent compounded fibers can refine cracks and play a compensatory role.

4. The function regulating components can not only realize their respective functions, but also promote each other. The reinforcing agent uses ferric nitrate, which can react with Ca(OH) ₂ generated by cement hydration to promote the early hydration reaction process; at the same time, the reaction product ferric hydroxide colloid can close capillary pores to achieve impermeability, improving impermeability sex. Cement-based permeable crystalline materials can play a catalytic role in cement hydration, and can also accelerate the early hydration process. The toughening agent fiber can not only reduce the microcracks caused by the volume change of the hydration reaction of the system, but the surface-treated fiber can reduce the total amount of the gelled material due to the interface effect due to the enhanced grip force with the gelled system. Increased porosity improves impermeability.

In the prior art, Chinese patent 02137419.8 uses 60%-80% of slag powder, 10%-30% of fly ash, 0-15% of silica fume, and 1%-5% of additives to prepare special admixtures for high-performance marine concrete , the difference between the present invention and the patent 02137419.8 is: the present invention differs from the composition of the mineral admixture, the specific surface area of the fly ash used is greater than 4500cm ² /g, and it only needs to be stirred evenly; the most important difference is the function Regulating components (corresponding to the patented additives), the present invention does not need grinding aids in the production process, and the technology to improve the release strength is to rely on the Ca(OH) generated by the hydration of iron nitrate in the reinforcing agent component and cement ₂ reaction, speeding up the hydration process by consuming the reaction product: at the same time, the sulfate group in the other component calcium sulfate will combine with the C ₃ A in the cement to form AFt to provide early strength. Another important difference between the present invention and this patent is that although both rely on secondary hydration products to fill the pores in the cementitious material system, the cement-based osmotic crystalline material in the function adjustment component of the present invention will react with water to form crystals Fill pores to achieve long-term anti-seepage effect. Moreover, the anti-seepage performance of the shield segment requires that the segment material should not crack, and the toughening agent used in the function adjustment component can better meet this requirement. The invention is specially designed for shield segment materials, and has stronger pertinence than Chinese patent 02137419.8.

Description of drawings

Fig. 1 is a flow chart of the preparation process of the shield segment high impermeability concrete admixture of the present invention.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Embodiment 1-2:

1, the preparation method of shield segment high impermeability concrete admixture, it comprises the following steps:

1), prepare this admixture by mixing the raw material ratio of table 1:

Table 1 Mass percentage of each component of the admixture

Example Slag fine powder fly ash Silica fume Ferric nitrate Calcium sulfate Cement-based penetrating crystalline powder mixed fiber 1 32% 48% 15.5% 0.75% 1% 2.25% 0.5% 2 27% 42% 25% 0.75% 1.5% 2.95% 0.8%

The mixed fiber is 3mm modified polypropylene fiber and 10mm modified polypropylene fiber compounded at a ratio of 2:1, and the surface of the used polypropylene fiber needs to be modified. Ferric nitrate and calcium sulfate use commercially pure chemicals.

2) Add the silica fume and hybrid fibers into the blender in proportion and mix them. The hybrid fibers need to be dispersed manually before adding. The small particles of silica fume are used to disperse the fibers as evenly as possible.

3) Mix and grind slag fine powder, ferric nitrate, calcium sulfate, and cement-based osmotic crystalline powder in proportion, then add fly ash and mix until the specific surface area is greater than 4500cm ² /g, and then mix the pre-mixed silica fume and The mixed fiber is added into the mixed mill evenly (the detailed process flow is shown in Figure 1), and the product is obtained.

2. Performance test of high impermeability concrete admixture for shield segment:

The prepared shield segment high-impermeability concrete admixture is replaced by 30% of the same amount of cement. ) to form a 100×100×100mm sample for testing; form a Φ100×200mm sample according to the American ASTM C1202 standard, and the mix ratio and test results are shown in Table 2. For comparison and illustration, a comparative test was carried out using pure cement samples. The curing system is consistent with the system used in the production of prefabricated segments, that is, steam curing for 11 hours after forming, then water curing for 7 days, and standard curing for 28 days.

Table 2 Mixing ratio and test results of each group

serial number cement HIS Example 1 HIS Example 2 sand stone water Release strength D _eff (×10 ^-13 m ² /s) Coulomb 1 540 0 0 676 1013 162 35.0 14.3 721 2 378 162 0 676 1013 162 28.0 4.47 137 3 378 0 162 676 1013 162 22.3 0.91 25

Note: HIS is shield segment high impermeability concrete admixture.

It can be seen from the test results that although the demoulding strength is reduced, it can still meet the needs of shield segment production, and its chloride ion diffusion coefficient and electric flux are greatly reduced, indicating that the high impermeability concrete admixture of shield segments Improve the impermeability of concrete.

In order to illustrate the stepwise anti-seepage effect of the high-impermeability concrete admixture of the shield segment, the chloride ion diffusion coefficient of the experimental group (number) 2 after demoulding, 14d age and 28d age was tested, and the experimental group (number) Group 1 for comparison. The test results are shown in Table 3.

Table 3 Test results of chloride ion diffusion coefficients at different ages

serial number D _eff (×10 ^-13 m ² /s) 11h 14d 28d 1 28.57 20.16 14.3 2 39.14 10.13 4.47 3 30.72 5.28 0.91

The experimental results show that due to the reduction of the primary hydration phase during demoulding, the chloride ion diffusion coefficient of the sample using the shield segment high impermeability concrete admixture is still greater than that of the pure cement sample, and the structure is not completely dense at this time However, the physical filling of mineral admixtures alone is not enough to make concrete have high impermeability. After 14 days of hydration, the secondary hydration greatly reduced the chloride ion diffusion coefficient value of the sample using the shield segment high impermeability concrete admixture, which was already lower than the test value of the comparison pure cement sample at 28 days. When the hydration age reaches 28 days, the chloride ion diffusion coefficient of the shield segment high impermeability concrete admixture is much lower than that of pure cement, indicating that the shield segment high impermeability concrete admixture can achieve long-term impermeability . Moreover, the waterproofing agent of the function adjustment component also has a water reaction, which can close some possible water seepage channels, and has a certain self-repairing function.

Example 3:

Shield segment high impermeability concrete admixture, which is mainly prepared by mixing and grinding slag, fly ash, silica fume and function adjustment component raw materials. The mass percentage of each raw material is: 25% slag, fly ash 47%, silica fume 25%, and functional adjustment component 3%; wherein the functional adjustment component is a reinforcing agent, a waterproofing agent and a toughening agent, and the mass percentage of the reinforcing agent, waterproofing agent, and toughening agent in the functional regulating component is: Strengthening agent 36%, waterproofing agent 51%, toughening agent 13%.

The reinforcing agent is formed by compounding ferric nitrate and calcium sulfate in a mass ratio of 1:1. The waterproofing agent is a cement-based permeable crystalline waterproofing material (powder). The toughening agent is a hybrid fiber, and the hybrid fiber is compounded by a modified polypropylene fiber of 3mm and a modified polypropylene fiber of 10mm, and the quality of the modified polypropylene fiber of 3mm and the modified polypropylene fiber of 10mm is The ratio is 1:1. The surface of polypropylene fiber needs to be modified to enhance its grip with the gelling system. The specific surface area of the fly ash is greater than 4500cm ² /g, and its performance should meet the requirements of the GB1596-2005 standard.

The preparation method of above-mentioned shield segment high impermeability concrete admixture, it comprises the steps:

1) Select each raw material according to the ratio of each raw material;

2) Mix the silica fume and the toughening agent in advance to disperse the fibers.

3) Mix and grind slag, reinforcing agent and waterproofing agent until the specific surface area is ≥ 4500cm ² /g, then add fly ash and mix and grind, then add prefabricated silica fume and toughening agent and mix and grind evenly to obtain the product.

Example 4:

Shield segment high impermeability concrete admixture, which is mainly prepared by mixing and grinding slag, fly ash, silica fume and function adjustment component raw materials. The mass percentage of each raw material is: slag 40%, fly ash 40%, silica fume 15%, and functional adjustment components 5%; wherein the functional adjustment components are reinforcing agents, waterproofing agents and toughening agents, and the mass percentages of reinforcing agents, waterproofing agents and toughening agents in the functional regulating components are: Strengthening agent 40%, waterproofing agent 48%, toughening agent 12%.

The reinforcing agent is formed by compounding ferric nitrate and calcium sulfate in a mass ratio of 1:2. The waterproofing agent is a cement-based permeable crystalline waterproofing material (powder). The toughening agent is a hybrid fiber, and the hybrid fiber is compounded by a modified polypropylene fiber of 3mm and a modified polypropylene fiber of 10mm, and the quality of the modified polypropylene fiber of 3mm and the modified polypropylene fiber of 10mm is The ratio is 2:1. The surface of polypropylene fiber needs to be modified to enhance its grip with the gelling system. The specific surface area of the fly ash is greater than 4500cm ² /g, and its performance should meet the requirements of the GB1596-2005 standard.

The preparation method of above-mentioned shield segment high impermeability concrete admixture, it comprises the steps:

1) Select each raw material according to the ratio of each raw material;

2) Mix the silica fume and the toughening agent in advance to disperse the fibers;

3) Mix and grind slag, reinforcing agent and waterproofing agent until the specific surface area is ≥ 4500cm ² /g, then add fly ash and mix and grind, then add prefabricated silica fume and toughening agent and mix and grind evenly to obtain the product.

Example 5:

The shield segment high impermeability concrete admixture is characterized in that it is mainly prepared by mixing and grinding slag, fly ash, silica fume and functional adjustment component raw materials. The mass percentage of each raw material is: slag 29%, 50% of fly ash, 15% of silica fume, and 6% of functional adjustment components; among them, the functional adjustment components are reinforcing agents, waterproofing agents and toughening agents, and the weight of the functional regulating components accounted for by reinforcing agents, waterproofing agents and toughening agents The percentages are: strengthening agent 36%, waterproofing agent 49%, toughening agent 15%.

The reinforcing agent is formed by compounding ferric nitrate and calcium sulfate at a mass ratio of 1:1.5. The waterproofing agent is a cement-based permeable crystalline waterproofing material (powder). The toughening agent is a hybrid fiber, and the hybrid fiber is compounded by a modified polypropylene fiber of 3mm and a modified polypropylene fiber of 10mm, and the quality of the modified polypropylene fiber of 3mm and the modified polypropylene fiber of 10mm is The ratio is 1.5:1. The surface of polypropylene fiber needs to be modified to enhance its grip with the gelling system. The specific surface area of the fly ash is greater than 4500cm ² /g, and its performance should meet the requirements of the GB1596-2005 standard.

The preparation method of the above-mentioned shield segment high impermeability concrete admixture is characterized in that it comprises the following steps:

1) Select each raw material according to the ratio of each raw material;

2) Mix the silica fume and the toughening agent in advance to disperse the fibers;

3) Mix and grind slag, reinforcing agent and waterproofing agent until the specific surface area is ≥ 4500cm ² /g, then add fly ash and mix and grind, then add prefabricated silica fume and toughening agent and mix and grind evenly to obtain the product.

Claims (6)

1. Shield segment high impermeability concrete admixture is characterized in that it is mainly prepared by mixing and grinding slag, fly ash, silica fume and function adjustment component raw materials, and the mass percentage of each raw material is: slag 25 %-40%, fly ash 40%-50%, silica fume 15%-25%, function adjustment components 3%-6%; the function adjustment components are reinforcing agent, waterproofing agent and toughening agent, strengthening agent The mass percentages of the functional adjustment components accounted for by the waterproofing agent and the toughening agent are: 36-40% of the reinforcing agent, 48-51% of the waterproofing agent, and 10-15% of the toughening agent. 2. The high impermeability concrete admixture for shield segment according to claim 1, characterized in that: the reinforcing agent is compounded by ferric nitrate and calcium sulfate at a ratio of 1:1-2 by mass. 3. The high-impermeability concrete admixture for shield segment according to claim 1, characterized in that: the waterproofing agent is a cement-based permeable crystalline waterproofing material. 4. shield segment high impermeability concrete admixture according to claim 1, is characterized in that: described toughening agent is hybrid fiber, and hybrid fiber is modified polypropylene fiber by 3mm and the modification of 10mm Polypropylene fibers are compounded, and the mass ratio of 3mm modified polypropylene fibers to 10mm modified polypropylene fibers is (1-2):1. 5. The high impermeability concrete admixture for shield segment according to claim 1, characterized in that: the specific surface area of the fly ash is greater than 4500 cm ² /g. 6. the preparation method of shield segment high impermeability concrete admixture as claimed in claim 1 is characterized in that it comprises the steps: 1) According to the mass percentage of each raw material: 25%-40% of slag, 40%-50% of fly ash, 15%-25% of silica fume, 3%-6% of functional adjustment components, select slag and fly ash , silica fume, and function-adjusting component raw materials, wherein the function-adjusting component is a reinforcing agent, waterproofing agent and toughening agent, and the mass percentage of the function-regulating component accounted for by the reinforcing agent, waterproofing agent, and toughening agent is: reinforcing agent 36-40 %, waterproofing agent 48-51%, toughening agent 10-15%; 2) Mix silica fume and toughening agent in advance; 3) Mix and grind slag, reinforcing agent and waterproofing agent until the specific surface area is ≥ 4500cm ² /g, then add fly ash and mix and grind, then add prefabricated silica fume and toughening agent and mix and grind evenly to obtain the product.