Alkali-activated fly ash-slag-silica fume ternary base shield synchronous grouting material and preparation method thereof

Abstract

The invention relates to an alkali-activated fly ash-slag-silica fume ternary base shield synchronous grouting material and a preparation method thereof, and the grouting material is prepared from the following raw materials in percentage by mass: gel powder consisting of 60%-100% of fly ash, 0%-16% of silica fume and 0%-40% of slag, an alkali-activated solution with the modulus of 1.2-1.8, and a water-retaining agent, the alkali doping amount, the fine sand, the water reducing agent and the retarder respectively account for 7%-10%, 70%-100%, 150%, 1.0% and 2.0% of the gelling powder. The preparation method comprises the following steps: putting the coal ash, the silica fume, the slag, the fine sand, the water reducing agent and the retarder into a stirrer, uniformly stirring in a dry manner, weighing the required alkali-activated solution according to the liquid-solid ratio requirement that the ratio of the mass of the alkali-activated solution to the mass of the gelling powder is 0.7-1.0, slowly adding the alkali-activated solution into the uniformly mixed powder, and continuously uniformly stirring. The alkali-activated fly ash-slag-silica fume-based shield synchronous grouting material prepared by the preparation method disclosed by the invention is relatively good in flowing property, working property, hardening property and economical efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of engineering materials, in particular to an alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material and a preparation method thereof. Background Art

[0002] In the process of shield tunnel construction, synchronous grouting technology plays a vital role in ensuring project quality, controlling ground settlement, and enhancing tunnel structure stability. This requires synchronous grouting materials to have excellent fluidity, suitable setting time, sufficient mechanical strength and good stability to adapt to various complex and changeable geological conditions and construction requirements. However, in traditional cement-based shield synchronous grouting materials, a large amount of cement is used, the production process has high energy consumption and large carbon emissions, which does not conform to the concept of green environmental protection. In addition, under complex geological conditions, such as water-rich and high-water pressure formations, its impermeability and anti-scouring capabilities are insufficient, which easily leads to slurry loss, tunnel leakage and other problems, making it difficult to effectively control ground settlement. Alkali-activated cementitious materials have good corrosion resistance, low permeability, excellent durability, and low cost, but existing alkali-activated grouting materials generally have low strength, especially low early strength and other problems.

[0003] At the same time, some materials have limitations in the selection of raw materials and performance. For example, some synchronous grouting materials with silicate cement, fine sand, etc. as the main components have certain anti-scouring and anti-dispersion properties, but under complex geological conditions, there is limited room for improvement in their mechanical properties. In addition, due to the high dependence on traditional raw materials, they have not been able to effectively solve the problems of resource consumption and environmental impact, and it is difficult to meet the development concept of green environmental protection. Materials suitable for water-rich strata with cement, fly ash, quicklime, etc. as raw materials have challenges in the precise control of their setting time during the construction process, and when dealing with extreme geological conditions such as high water pressure and strong dissolution, their durability is insufficient and cannot guarantee the long-term stable operation of the tunnel.

[0004] The resource utilization of industrial solid waste has become a research focus in the field of construction engineering. Alkali activation technology can stimulate the activity of fly ash, silica fume and slag, and under their synergistic effect, it not only realizes the efficient resource utilization of industrial solid waste, effectively reduces the amount of cement, reduces energy consumption and carbon emissions, but also significantly improves the fluidity, stability, controllability of setting time and mechanical properties of the slurry after hardening compared with traditional cement-based synchronous grouting materials and some existing alkali-activated synchronous grouting materials through scientific optimization of formula and preparation process. However, most of the current research on shield synchronous grouting materials focuses on basic physical and mechanical properties, and the discussion on the durability properties such as impermeability and corrosion resistance required for the material as the primary protective layer in the tunnel lining is relatively insufficient. These durable properties are crucial to ensure the long-term stable operation of tunnels under extreme geological conditions and are key indicators for evaluating the comprehensive performance of synchronous grouting materials. Therefore, the development of an efficient and environmentally friendly synchronous grouting material that takes into account basic performance indicators and has excellent durability and stability has become the key to solving the construction problems of shield tunnels under water-rich strata. Summary of the invention

[0005] The object of the present invention is to provide an alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material and a preparation method thereof. The material uses fly ash, slag and silica fume instead of cement to prepare an alkali-activated fly ash-slag-silica fume-based grouting slurry. By adjusting the proportion of cementitious powder, the modulus of the alkali-activated solution, the alkali dosage and the liquid-solid ratio, a grouting material with low fluidity, low water seepage rate, high stone rate, long setting time, high compressive strength and low water absorption rate is obtained. For special strata requiring a short slurry setting time, high early strength and good anti-seepage performance of water-rich gravel, the alkali dosage can be increased or the liquid-solid ratio can be reduced to prepare a slurry that meets the engineering requirements.

[0006] The technical solution adopted by the present invention is: to provide an alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material, which is made of the following raw materials in percentage by mass:

[0007] Cementitious powder: fly ash 60%-100%, silica fume 0%-16%, slag 0%-40%;

[0008] Alkali-activated solution: a sodium water glass solution with a modulus of 1.2-1.8, wherein the alkali-activated solution accounts for 70%-100% of the gelling powder;

[0009] Alkali dosage: 7%-10% of the gelling powder;

[0010] Fine sand: 150% of cementitious powder;

[0011] Water reducing agent: 1.0% of the cementitious powder;

[0012] Retarder: 2.0% of the cementitious powder.

[0013] The fly ash is Class II F fly ash with a specific surface area of ​​≥360m 2 / kg; the SiO2 content of the silica ash is 98.40%, and the specific surface area is ≥360m 2 / kg; the slag is S95 grade, with a specific surface area of ​​≥360m 2 / kg.

[0014] The alkali-activated solution is made of sodium water glass, NaOH particles and deionized water, and the solution modulus is controlled within the range of 1.2-1.8 by adjusting the amount of NaOH added.

[0015] The alkaline excitation solution is prepared by adjusting the amount of NaOH added to control the solution modulus within the range of 1.2-1.8, and the steps are as follows:

[0016] The SiO2 content of sodium water glass used is 27.3%, the Na2O content is 8.54%, the modulus n is 3.3, and the modulus after deployment is 1.2-1.8. The alkali dosage refers to the proportion of the alkaline oxide Na2O in the alkali-activated solution to the mass of the gelling powder. When the modulus of the sodium water glass solution is 1.6, the Na2O content is y. According to formula (1), y is calculated to be 17.06%. If the required alkali dosage is 8%, the required sodium water glass content is calculated to be 35.16% according to formula (2). According to formula (3), the required deionized water content is 64.84%. According to this algorithm, the required sodium water glass content when making alkali-activated solutions of different moduli can be calculated.

[0017] SiO2 / Na2O=27.3% / y=1.6 (1)

[0018] 8% / 17.06%=46.89% (2)

[0019] 100%-46.89%=53.11% (3)

[0020] Described sodium water glass solution is prepared as follows:

[0021] Add an appropriate amount of NaOH to the water glass solution to reduce the modulus of the water glass to the target value. The specific method is to take a certain amount of sodium water glass solution, calculate the mass of each component of Na2O, SiO2 and H2O according to the mass percentage of Na2O and SiO2, and change SiO2 / Na2O by adding NaOH. According to formula (4), the original modulus of sodium water glass with a modulus of 3.3 can be adjusted to the required modulus. To obtain a sodium water glass solution with a modulus of 1.6, the Na2O content in the sodium water glass with a modulus of 3.3 can be set as x. According to formulas (5) and (6), the amount of Na2O added is calculated to be 9.07%, the relative molecular weight of Na2O is 62, and the relative molecular weight of NaOH is 80. According to formula (7), the amount of NaOH added is calculated to be 11.7%.

[0022] Na2SiO3+2NaOH→Na2SiO3+Na2O+H2O (4)

[0023] 3.3 / 1.6=x / 8.54 (5)

[0024] 17.61%-8.54%=9.07% (6)

[0025] (80×9.07%)×62=11.7% (7).

[0026] The fineness modulus of the fine sand is 1.86, and the mud content is 1.68%; the water reducer is a naphthalene-based water reducer; and the retarder is barium nitrate.

[0027] The preparation method of the alkali-activated fly ash-slag-silica ash ternary-based shield synchronous grouting material comprises the following steps:

[0028] (1) Weigh fly ash, silica fume, and slag to make a cementitious powder, and separately take fine sand, a water reducer, and a retarder. Place the above materials in a mixer and dry stir for 5 minutes to make the powder mix evenly;

[0029] (2) According to the liquid-to-solid ratio of 0.7-1.0, weigh the alkali-activated solution according to 70%-100% of the mass of the gelling powder, slowly add it to the uniformly mixed powder and continue stirring for 3 minutes to obtain the grouting material.

[0030] In the preparation method, the mixer is a JJ-5 planetary cement mortar mixer.

[0031] The optimal ratio of the alkali-activated fly ash-slag-silica fume ternary shield synchronous grouting material is: the cementitious powder ratio is 72% fly ash, 20% slag and 8% silica fume, the alkali-activated solution modulus is 1.6, the alkali content is 8% and the liquid-solid ratio is 0.9.

[0032] The optimal preparation method of the alkali-activated fly ash-slag-silicon ash ternary-based shield synchronous grouting material comprises the following steps:

[0033] (1) Weigh the cementitious powder material with a ratio of 72% fly ash, 20% slag and 8% silica fume, and separately take fine sand, water reducer and retarder, place the above materials in a mixer and dry stir for 5 minutes to make the powder material evenly mixed;

[0034] (2) Based on a liquid-to-solid ratio of 0.9, an alkali-activated solution with a modulus of 1.6 is weighed at 90% of the mass of the gelled powder, wherein the alkali content of the solution is 8%, and then slowly added to the uniformly mixed powder and stirred for 3 minutes to obtain the grouting material.

[0035] The alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material is used in shield tunnel construction. The grouting material is suitable for water-rich gravel strata. By adjusting the alkali dosage or the liquid-solid ratio, a slurry that meets different engineering requirements can be prepared.

[0036] Through the above technical scheme, three kinds of industrial solid waste admixtures replace cement as cementitious powder. Under their combined action, the rheological properties, working performance and hardening performance of the slurry can be optimized to the greatest extent at the same time. By optimizing the dosage of each raw material of the shield synchronous grouting material, the dosage of the shield synchronous grouting material is made within this range, and its fluidity, water seepage rate, stone rate, setting time, compressive strength and water absorption rate can all achieve maximum optimization effect.

[0037] Technical principle:

[0038] Slag contains a large amount of SiO2 and Al2O3, which can react with alkali-activated solution under alkaline conditions to form aluminosilicate gel, making it a substitute for traditional cement cementitious powder. Fly ash contains a large amount of aluminosilicate glass, which can be activated by alkali activation to activate its gelling activity, improve the workability of the slurry, and increase the later strength. Silica fume has the characteristics of large specific surface area and good dispersibility. The appropriate amount of silica fume can promote the formation of cementitious substances, and the fine inert particles in silica fume have a filling effect on pores, making the hardened sample of cementitious materials denser, thereby improving the compressive strength.

[0039] The use of barium nitrate retarder can react with OH in the alkali-activated cementitious material system. - 、[SiO4] 4- and Ca 2+ The plasma reacts to form hydroxides or silicates on the surface of the cementitious material particles, thereby slowing down the speed of contact and reaction between the alkali-activated solution and the cementitious powder, thereby effectively extending the setting time of the alkali-activated cementitious material.

[0040] The appropriate liquid-to-solid ratio is conducive to the regular construction of the gel network and promotes the optimization of the material density and strength. An imbalance in the liquid-to-solid ratio, whether it is too high or too low, will destroy the normal formation and uniform distribution of the gel and have a negative effect on the porosity and durability of the material.

[0041] Water glass has an important influence on the mechanical properties of grouting materials. The SiO4 tetrahedral structural unit in water glass is not unique. In the process of lowering the modulus of the alkaline solution, the SiO4 tetrahedral structural unit gradually changes from Q 3 Structure and Q 4 Structural transition to Q 0 Structure, Q 1 The structure (the superscript Q refers to the number of Si atoms connected to adjacent Si atoms through Si-O-Si bonds) promotes the hydrolysis of Si-O-Si, reduces the polymerization degree of SiO4, makes SiO4 easier to participate in the reaction, and generates more gel material at the same time, thereby reducing the fluidity of the slurry. However, the larger the modulus of the alkali-activated solution, the greater the solution viscosity, which will also have a negative effect on the fluidity of the slurry.

[0042] The beneficial effects of the present invention are:

[0043] 1. Use fly ash, slag, silica fume and other industrial waste residues as cementitious powder to reduce dependence on cement, realize the recycling of industrial waste residues, reduce energy consumption and environmental pollution, actively respond to the green and low-carbon development strategy, improve resource utilization, and reduce waste emissions.

[0044] 2. The characteristics of alkali-activated industrial solid waste powder in the field of synchronous grouting of shield tunnels were explored. By optimizing the slurry ratio, the slurry met the requirements of pumping and engineering application, laying the foundation for the application of alkali-activated fly ash-slag-silica fume based slurry in shield synchronous grouting construction.

[0045] 3. Study the law of change of slurry performance under a higher liquid-to-solid ratio (0.7-1.0), optimize the flow, working and hardening performance of the slurry, improve the adaptability of synchronous grouting materials in complex geological environments, reduce costs and improve construction efficiency while ensuring project quality, and provide a more cost-effective and stable material solution for shield tunnel construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the effect of slag dosage on slurry fluidity.

[0047] Figure 2 Schematic diagram of the effect of slag dosage on slurry rheological curve.

[0048] Figure 3 Schematic diagram of the effect of slag dosage on slurry setting time.

[0049] Figure 4Schematic diagram of the effect of slag content on unconfined compressive strength.

[0050] Figure 5 Schematic diagram of the effect of slag content on the stress-strain curve (3d).

[0051] Figure 6 Schematic diagram of the effect of slag content on stress-strain curve (28d).

[0052] Figure 7 Schematic diagram of the effect of slag content on elastic modulus.

[0053] Figure 8 Schematic diagram of the effect of slag dosage on water absorption.

[0054] Fig. 9 (3d) XRD patterns at different slag dosages.

[0055] Fig.10 (28d) XRD patterns at different slag dosages.

[0056] Fig.11 Schematic diagram of the effect of silica fume dosage on slurry fluidity.

[0057] Fig.12 Schematic diagram of the effect of silica fume dosage on slurry rheological curve.

[0058] Fig.13 Schematic diagram of the effect of silica fume dosage on slurry setting time.

[0059] Fig.14 Schematic diagram of the effect of silica fume content on unconfined compressive strength.

[0060] Fig.15 Schematic diagram of the effect of silica fume content on the stress-strain curve (3d).

[0061] Fig.16 Schematic diagram of the effect of silica fume content on stress-strain curve (28d).

[0062] Fig.17 Schematic diagram of the effect of silica fume content on elastic modulus.

[0063] Fig.18 Schematic diagram of the effect of silica fume dosage on water absorption.

[0064] Fig.19 (3d) XRD patterns at different silica fume dosages.

[0065] Fig. 20 (28d) XRD patterns at different silica fume dosages.

[0066] Fig.21 Schematic diagram of the effect of alkali-activated solution modulus on slurry fluidity.

[0067] Fig. 22 Schematic diagram of the effect of alkali-activated solution modulus on the rheological curve of the slurry.

[0068] Fig.23 Schematic diagram of the effect of alkali-activated solution modulus on slurry setting time.

[0069] Fig.24 Schematic diagram of the effect of alkali-activated solution modulus on unconfined compressive strength.

[0070] Fig.25 Schematic diagram of the effect of alkali-induced solution modulus on the stress-strain curve (3d).

[0071] Fig.26 Schematic diagram of the effect of alkali-induced solution modulus on the stress-strain curve (28d).

[0072] Fig. 27 Schematic diagram of the effect of alkali-excited solution modulus on the elastic modulus.

[0073] Fig.28 Schematic diagram of the effect of alkali-excited solution modulus on water absorption.

[0074] Fig.29 (3d) XRD patterns of the solutions under different base excitation moduli.

[0075] Fig.30 (28d) XRD patterns of the solutions under different base excitation moduli.

[0076] Fig.31 Schematic diagram of the effect of alkali dosage on slurry fluidity.

[0077] Fig.32 Schematic diagram of the effect of alkali dosage on the rheological curve of slurry.

[0078] Fig.33 Schematic diagram of the effect of alkali dosage on slurry setting time.

[0079] Fig.34 Schematic diagram of the effect of alkali content on unconfined compressive strength.

[0080] Fig.35 Schematic diagram of the effect of alkali dosage on the stress-strain curve (3d).

[0081] Fig.36 Schematic diagram of the effect of alkali dosage on the stress-strain curve (28d).

[0082] Fig.37 Schematic diagram of the effect of alkali content on elastic modulus.

[0083] Fig.38 Schematic diagram of the effect of alkali dosage on water absorption.

[0084] Fig.39 (3d) XRD patterns at different alkali dosages.

[0085] Fig.40 (28d) XRD patterns at different alkali doping levels.

[0086] Fig.41 Schematic diagram of the effect of liquid-to-solid ratio on slurry fluidity.

[0087] Fig.42 Schematic diagram of the effect of liquid-to-solid ratio on the rheological curve of slurry.

[0088] Fig.43 Schematic diagram of the effect of liquid-to-solid ratio on slurry setting time.

[0089] Fig.44 Schematic diagram of the effect of liquid-to-solid ratio on unconfined compressive strength.

[0090] Fig.45 Schematic diagram of the effect of liquid-to-solid ratio on the stress-strain curve (3d).

[0091] Fig.46 Schematic diagram of the effect of liquid-to-solid ratio on stress-strain curve (28d).

[0092] Fig.47 Schematic diagram of the effect of liquid-to-solid ratio on elastic modulus.

[0093] Fig.48 Schematic diagram of the effect of liquid-to-solid ratio on water absorption.

[0094] Fig.49 (3d) XRD patterns at different liquid-to-solid ratios.

[0095] Fig.50 (28d) XRD patterns at different liquid-to-solid ratios. DETAILED DESCRIPTION

[0096] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0097] Example 1

[0098] The alkali-activated fly ash-slag-silicon ash ternary-based shield synchronous grouting material of the present invention is made of the following raw materials in percentage by mass:

[0099] Fly ash: Class II F fly ash, produced by Gongyi Longze Water Purification Materials Co., Ltd.

[0100] Silica fume: The manufacturer is Gongyi Longze Water Purification Materials Co., Ltd.

[0101] Slag: S95 grade slag, produced by Gongyi Longze Water Purification Materials Co., Ltd.;

[0102] Solid sodium hydroxide: purity ≥96%;

[0103] Fine sand: ordinary fine river sand, fineness modulus 1.86, mud content 1.68%, bulk density 1528kg / m 3 ;

[0104] Retarder: barium nitrate, purity ≥99.5%, produced by Chengdu Jinshan Chemical Reagent Co., Ltd.;

[0105] Water reducer: Naphthalene-based water reducer, manufactured by Shandong Yousuo Chemical Technology Co., Ltd.

[0106] The specific surface area of ​​the fly ash selected above is 360m 2 / kg, the specific surface area of ​​silica fume is 2497m 2 / kg, the specific surface area of ​​slag is 429m 2 / kg, the chemical compositions of the three industrial solid wastes are shown in Table 1.

[0107] Table 1 Chemical composition content of three types of industrial solid waste (%)

[0108]

[0109] Example 1 is an example of a method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, wherein various raw materials and amounts thereof are shown in Table 3, and the method comprises the following steps:

[0110] (1) Weigh the required fly ash, silica fume, slag, fine river sand, retarder, and water reducer, and then put them into a mixer and stir for 5 minutes until they are evenly mixed;

[0111] (2) Weigh out the required alkali-stimulating solution according to the corresponding liquid-to-solid ratio, then slowly add it to the evenly mixed powder and continue stirring for 3 minutes.

[0112] The water reducer and retarder are fixed at 1.0% and 2.0%, the ratio of fine sand mass to cementitious powder mass is fixed at 1.5, the ratio of alkali-activated solution mass to cementitious powder mass is 0.9, fly ash is 100%, slag is 0%, silica fume is 0%, alkali solution modulus is 1.6, and alkali dosage is 8%.

[0113] The specific performance indicators of the sodium water glass solution selected above are shown in Table 2.

[0114] Table 2 Performance indicators of sodium water glass

[0115]

[0116]

[0117] The alkali-activated solution used in the present invention is made of sodium water glass, NaOH particles and deionized water. Adding an appropriate amount of NaOH to the water glass solution can reduce the modulus of the water glass to a target value, and the specific method is as follows:

[0118] Take a certain amount of sodium water glass solution, calculate the mass of each component of Na2O, SiO2 and H2O according to the mass percentage of Na2O and SiO2, and change SiO2 / Na2O by adding NaOH, as shown in formula 1:

[0119] Na2SiO3+2NaOH→Na2SiO3+Na2O+H2O (1)

[0120] The modulus of the original sodium water glass solution (modulus = 3.3) can be adjusted to the required modulus.

[0121] The sodium water glass used in the present invention has a SiO2 content of 27.3%, a Na2O content of 8.54%, and a modulus n of 3.3. To obtain a sodium water glass with a modulus of 1.6, the Na2O content of the sodium water glass can be set to x when n=3.3, as shown in Formula 2:

[0122] 3.3 / 1.6=x / 8.54 (2)

[0123] That is: the content of Na2O to be added is

[0124] 17.61%-8.54%=9.07% (3)

[0125] The relative molecular weight of Na2O is 62, and the relative molecular weight of NaOH is 80. The amount of NaOH added is

[0126] (80×9.07%)×62=11.7% (4)

[0127] By adding 11.7% NaOH to the original sodium water glass with a modulus of 3.3, a sodium water glass solution with a modulus of 1.6 can be obtained.

[0128] According to the algorithm, the mass of NaOH required to adjust the modulus of sodium water glass with a modulus of 3.3 to different moduli can be calculated.

[0129] Example 2

[0130] This embodiment is an example of a method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, and its raw materials and dosage ratio are shown in Table 3, comprising the following steps:

[0131] (1) Weigh the required mass of different materials, place the weighed materials in a JJ-5 planetary cement mortar mixer and dry stir for 5 minutes to ensure that the powders are fully mixed.

[0132] (2) After the materials are evenly stirred, weigh out the required alkali excitation solution according to the corresponding liquid-to-solid ratio, then slowly add it to the evenly mixed powder and continue stirring for 3 minutes to obtain the slurry required for the test.

[0133] Table 3 Slurry ratio of Examples 1-18

[0134]

[0135]

[0136] (Continued Table 3)

[0137]

[0138] Example 2

[0139] This embodiment is the second example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0140] The difference between this embodiment and embodiment 1 is that the fly ash content is 90%, the slag content is 10%, and the remaining steps and amounts are the same as those in embodiment 1.

[0141] Example 3

[0142] This embodiment is the third example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0143] The difference between this embodiment and embodiment 1 is that the fly ash content is 80%, the slag content is 20%, and the remaining steps and amounts are the same as those in embodiment 1.

[0144] Example 4

[0145] This embodiment is the fourth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0146] The difference between this embodiment and embodiment 1 is that the fly ash content is 70%, the slag content is 30%, and the remaining steps and amounts are the same as those in embodiment 1.

[0147] Example 5

[0148] This embodiment is the fifth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0149] The difference between this embodiment and embodiment 1 is that the fly ash content is 60%, the slag content is 40%, and the remaining steps and amounts are the same as those in embodiment 1.

[0150] Example 6

[0151] This embodiment is the sixth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0152] The difference between this embodiment and embodiment 1 is that the fly ash content is 76%, the slag content is 20%, and the silica fume content is 4%. The remaining steps and amounts are the same as those in embodiment 1.

[0153] Example 7

[0154] This embodiment is the seventh example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0155] The difference between this embodiment and embodiment 6 is that the fly ash content is 72%, the silica fume content is 8%, and the remaining steps and amounts are the same as those in embodiment 6.

[0156] Example 8

[0157] This embodiment is the eighth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0158] The difference between this embodiment and embodiment 6 is that the fly ash content is 68%, the silica fume content is 12%, and the remaining steps and amounts are the same as those in embodiment 6.

[0159] Example 9

[0160] This embodiment is the ninth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0161] The difference between this embodiment and embodiment 6 is that the fly ash content is 64%, the silica fume content is 16%, and the remaining steps and amounts are the same as those in embodiment 6.

[0162] Example 10

[0163] This embodiment is the tenth example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0164] The difference between this embodiment and embodiment 7 is that the modulus of the alkaline solution is 1.2, and the remaining steps and amounts are the same as those in embodiment 7.

[0165] Embodiment 11

[0166] This embodiment is the 11th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0167] The difference between this embodiment and embodiment 10 is that the modulus of the alkaline solution is 1.4, and the remaining steps and amounts are the same as those of embodiment 10.

[0168] Example 12

[0169] This embodiment is the 12th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0170] The difference between this embodiment and embodiment 10 is that the modulus of the alkaline solution is 1.8, and the remaining steps and amounts are the same as those in embodiment 10.

[0171] Example 13

[0172] This embodiment is the 13th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0173] The difference between this embodiment and embodiment 7 is that the alkali dosage is 7%, and the remaining steps and dosages are the same as those in embodiment 7.

[0174] Embodiment 14

[0175] This embodiment is the 14th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0176] The difference between this embodiment and embodiment 7 is that the alkali dosage is 9%, and the remaining steps and dosages are the same as those in embodiment 7.

[0177] Embodiment 15

[0178] This embodiment is the 15th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0179] The difference between this embodiment and embodiment 7 is that the alkali dosage is 10%, and the remaining steps and dosages are the same as those in embodiment 7.

[0180] Example 16

[0181] This embodiment is the 16th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0182] The difference between this embodiment and embodiment 7 is that the liquid-to-solid ratio is 0.7, and the remaining steps and amounts are the same as those in embodiment 7.

[0183] Embodiment 17

[0184] This embodiment is the 17th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0185] The difference between this embodiment and embodiment 7 is that the liquid-to-solid ratio is 0.8, and the remaining steps and amounts are the same as those in embodiment 7.

[0186] Embodiment 18

[0187] This embodiment is the 18th example of the method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material of the present invention, comprising the following steps:

[0188] The difference between this embodiment and embodiment 7 is that the liquid-to-solid ratio is 1.0, and the remaining steps and amounts are the same as those in embodiment 7.

[0189] Performance testing

[0190] Detection method / test method

[0191] The material was prepared according to the preparation method of alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material in Example 1-18, and then tested according to the following test method. The test results are shown in Table 4.

[0192] Fluidity: Refer to GB / T 50448-2015 "Technical Specifications for Application of Cement-based Grouting Materials".

[0193] Water seepage rate: refer to T / CECS 563-2018 "Technical Specifications for Application of Synchronous Grouting Materials in Shield Tunnels".

[0194] Stone rate: refer to T / CECS 563-2018 "Technical Code for Application of Synchronous Grouting Materials in Shield Tunnels".

[0195] Setting time: Refer to GB / T 1346-2011 "Test methods for water consumption, setting time and stability of cement of standard consistency".

[0196] Unconfined compressive strength: Referring to JGJ / T70-2009 "Standard for Test Methods of Basic Properties of Building Mortar", the mixed slurry was poured into a 70.7mm×70.7mm×70.7mm triple test mold and sealed with plastic wrap to reduce water evaporation. The mold was removed after standing at 20±2℃ for 24 hours. The demolded test block was placed in a standard curing box at 20±2℃ and relative humidity of 95% for curing to different test ages. The unconfined pressure test was carried out using the TWJ-1000 electro-hydraulic servo rock multifunctional testing machine, and the deformation of the test block was collected using a grating sensor.

[0197] Water absorption rate: refer to JGJ / T 70-2009 "Standard for test methods of basic properties of building mortar".

[0198] The main performance index requirements for synchronous grouting slurry in shield tunnels under water-rich gravel conditions are shown in Table 5.

[0199] Table 4 Test results of Examples 1-18

[0200]

[0201]

[0202] (Continued Table 4)

[0203]

[0204] Table 5 Performance index requirements of synchronous grouting slurry for shield tunnel

[0205]

[0206] It can be seen from the test data of single factor tests in Examples 1-18 that fly ash, silica fume, slag, alkali-activated solution modulus, alkali dosage and liquid-solid ratio all have different degrees of influence on the initial fluidity, water seepage rate and stone rate, setting time, 3d compressive strength, 28d compressive strength and 48h water absorption of the slurry, and it is necessary to reduce the negative influence and increase the positive influence. By using industrial solid waste powder fly ash, slag, and silica fume as cementitious powders and combining them with alkali-activated solution to prepare alkali-activated industrial solid waste-based slurry, the slurry ratio of synchronous grouting that meets engineering applications and has good performance is selected, laying the foundation for the application of alkali-activated industrial solid waste-based slurry in shield synchronous grouting construction.

[0207] When the slag content increases from 0% to 40%, the compressive strength and elastic modulus of the samples at 3d and 28d increase to varying degrees, and the water absorption rate of the samples gradually decreases, indicating that the addition of slag has a positive effect on the deformation resistance and impermeability of the samples. The rate of decrease of the stress-strain curve of the samples increases with the increase of slag content, indicating that the greater the amount of slag added, the more likely the samples are to suffer brittle failure.

[0208] When the silica fume content increases from 0% to 16%, the compressive strength and elastic modulus of the samples at 3d and 28d show a change pattern of first increasing and then decreasing, reaching the maximum value when the silica fume content is 8%; the water absorption rate of the samples shows a change pattern of first decreasing and then increasing, reaching the minimum value when the silica fume content is 8%, indicating that the deformation resistance and impermeability of the samples do not increase completely with the increase of silica fume content, and the optimal value of silica fume content is 8%. For the 28d stress-strain curve, the decreasing rate of the sample with a silica fume content of 16% is faster than that of the sample with a silica fume content of 0%, indicating that excessive silica fume addition will not only reduce the deformation resistance and impermeability of the sample, but also make it more prone to brittle failure.

[0209] As the modulus of the alkali-activated solution increases from 1.2 to 1.8, the compressive strength and elastic modulus of the samples at ages of 3d and 28d show a change pattern of first increasing and then decreasing, reaching the maximum value when the modulus is 1.6; the water absorption rate of the samples shows a change pattern of first decreasing and then increasing, reaching the minimum value when the modulus is 1.6. This shows that the deformation resistance and impermeability of the samples do not completely increase with the increase of the modulus, and the optimal value of the alkali-activated solution modulus is 1.6.

[0210] As the alkali content increases from 7% to 10%, the compressive strength and elastic modulus of the samples at 3d and 28d increase to varying degrees, and the water absorption rate of the samples gradually decreases, indicating that increasing the alkali content has a positive effect on the deformation resistance and impermeability of the samples. The rate of decrease of the stress-strain curve of the sample increases with the increase of the alkali content, indicating that the larger the alkali content, the more likely the sample is to produce brittle failure.

[0211] As the liquid-solid ratio increases from 0.7 to 1.0, the compressive strength and elastic modulus of the samples at ages of 3d and 28d decrease to varying degrees, and the water absorption rate of the samples gradually increases, indicating that increasing the liquid-solid ratio has a negative effect on the sample's ability to resist deformation and impermeability.

[0212] The XRD test results of samples with different proportions show that the phase components of the samples under different factors and levels are roughly the same, but the degree of hydration of the cementitious powder is different. For samples with an age of 3d, the crystal components contained in the samples are mainly quartz and mullite; for samples with an age of 28d, the crystal components contained in the G1 test group (pure fly ash) are mainly quartz and mullite, and the crystal components contained in other test groups include calcium carbonate in addition to quartz and mullite. When the slag content increases, the diffraction peak intensity of quartz and mullite gradually weakens, and the degree of hydration of the cementitious powder increases, which is beneficial to promote the mechanical properties of the sample, but the diffraction peak intensity of calcium carbonate crystals gradually becomes sharper, which is more susceptible to carbonization and thus affects the mechanical properties of the sample. When the silica fume content increases, the diffraction peak intensity of calcium carbonate crystals gradually decreases, which is beneficial to improve the anti-carbonization ability of the sample. When the modulus of the alkali-excited solution increases, the diffraction peak intensity of quartz, mullite and calcium carbonate crystals shows a change pattern of first decreasing and then increasing, indicating that the hydration degree and carbonation resistance of the cementitious powder do not completely increase with the increase of the modulus, and the modulus has an optimal value of 1.6. When the alkali content increases, the diffraction peak intensity of quartz, mullite and calcium carbonate crystals gradually weakens, indicating that the hydration degree of the cementitious powder and the carbonation resistance of the sample increase with the increase of the alkali content. When the liquid-solid ratio increases, the diffraction peak intensity of quartz, mullite and calcium carbonate crystals gradually becomes sharp, indicating that the hydration degree of the cementitious powder and the carbonation resistance of the sample decrease with the increase of the liquid-solid ratio.

[0213] According to the geological conditions and construction requirements in different actual projects, different proportions of slurry are selected. Generally, the larger the modulus and liquid-solid ratio of the alkali-activated solution and the lower the alkali content, the better the slurry economy. Therefore, the use of a cementitious powder ratio of 72% fly ash, 20% slag and 8% silica fume, an alkali-activated solution modulus of 1.6, an alkali content of 8%, and a liquid-solid ratio of 0.9 to prepare synchronous grouting slurry has the following advantages:

[0214] (1) Under this ratio, the slurry has excellent fluidity. Combined with the test data of Example 7, it can be seen that its fluidity can reach 321 mm, which meets the 160-340 mm range of the shield tunnel synchronous grouting slurry performance index requirements in Table 5. The fluidity under this ratio is in a reasonable range, which can ensure that the slurry is smooth and unobstructed during the pumping process, effectively avoiding pipe blockage.

[0215] (2) In terms of stability, combined with the test data of Example 7, it can be seen that the water seepage rate and stone formation rate of the slurry under this ratio are 0% and 99.79%, respectively, which are lower and higher than the 3.5% and 95% required in Table 5, respectively. This fully demonstrates that the slurry has excellent stability during the standing and coagulation and hardening process, can effectively prevent powder sedimentation and water separation, and ensure the uniformity and integrity of the slurry.

[0216] (3) In terms of setting time, combined with the test data of Example 7, it can be seen that the setting time of the slurry under this ratio is 307 minutes, which meets the range of 180-600 minutes required in Table 5. The appropriate setting time can not only ensure sufficient operation time during pumping, but also can set and harden in time after injection into the formation, effectively control the formation settlement, and avoid problems such as pipe blockage caused by too short setting time or formation deformation that cannot be controlled in time due to too long setting time.

[0217] (4) Good mechanical properties. Combined with the test data of Example 7, it can be seen that after the slurry hardens, the 3d compressive strength under this ratio reaches 3.45MPa, and the 28d compressive strength is 12.51MPa, both of which meet the requirements of 3d compressive strength greater than 0.5MPa and 28d compressive strength greater than 2.5MPa in Table 5. Therefore, its strength is sufficient to effectively resist the formation pressure and deformation, ensure the stable fixation of the pipe segment, thereby effectively controlling the formation settlement and improving the waterproof performance of the tunnel, and effectively meeting the actual needs of the project.

[0218] (5) In terms of cost, the large amount of industrial solid waste powder used to replace traditional cement as a cementitious material significantly reduces the cost of raw materials, demonstrating its advantages in cost and environmental protection.

[0219] In summary, the present invention provides an alkali-activated fly ash-slag-silica ash ternary shield synchronous grouting material using industrial solid waste powder fly ash, slag and silica ash as main raw materials. By controlling the proportion of fly ash, silica ash and slag in the cementitious powder, the modulus, alkali dosage and liquid-solid ratio of the alkali-activated solution, the material's flowability, working performance, hardening performance and economy are optimized, making it have significant application advantages in the field of shield tunnel synchronous grouting in water-rich gravel formations. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several optimizations can still be made, and these optimizations should also be regarded as the protection scope of the present invention.

Claims

1. Alkali-activated fly ash-slag-silica fume ternary shield synchronous grouting material, characterized in that: Made from the following raw materials in percentage by mass: Cementitious powder: fly ash 60%-100%, silica fume 0%-16%, slag 0%-40%; Alkali-activated solution: a sodium water glass solution with a modulus of 1.2-1.8, wherein the alkali-activated solution accounts for 70%-100% of the gelling powder; Alkali dosage: 7%-10% of the gelling powder; Fine sand: 150% of cementitious powder; Water reducing agent: 1.0% of the cementitious powder; Retarder: 2.0% of the cementitious powder.

2. The alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material according to claim 1, characterized in that: The fly ash is Class II F fly ash with a specific surface area of ​​≥360m 2 / kg; the SiO2 content of the silica ash is 98.40%, and the specific surface area is ≥360m 2 / kg; the slag is S95 grade, with a specific surface area of ​​≥360m 2 / kg.

3. The alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material according to claim 1, characterized in that: The alkali-activated solution is made of sodium water glass, NaOH particles and deionized water, and the solution modulus is controlled within the range of 1.2-1.8 by adjusting the amount of NaOH added.

4. The alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material according to claim 3, characterized in that: The alkaline excitation solution is prepared by adjusting the amount of NaOH added to control the solution modulus within the range of 1.2-1.8, and the steps are as follows: The SiO2 content of sodium water glass used is 27.3%, the Na2O content is 8.54%, the modulus n is 3.3, and the modulus after deployment is 1.2-1.

8. The alkali dosage refers to the proportion of the alkaline oxide Na2O in the alkali-activated solution to the mass of the gelling powder. When the modulus of the sodium water glass solution is 1.6, the Na2O content is y. According to formula (1), y is calculated to be 17.06%. If the required alkali dosage is 8%, the required sodium water glass content is calculated to be 35.16% according to formula (2). According to formula (3), the required deionized water content is 64.84%. According to this algorithm, the required sodium water glass content when making alkali-activated solutions of different moduli can be calculated. SiO2 / Na2O=27.3% / y=1.6 (1) 8％ / 17.06％＝46.89％ (2) 100％-46.89％＝53.11％ (3) Described sodium water glass solution is prepared as follows: Add an appropriate amount of NaOH to the water glass solution to reduce the modulus of the water glass to the target value. The specific method is to take a certain amount of sodium water glass solution, calculate the mass of each component of Na2O, SiO2 and H2O according to the mass percentage of Na2O and SiO2, and change SiO2 / Na2O by adding NaOH. According to formula (4), the original modulus of sodium water glass with a modulus of 3.3 can be adjusted to the required modulus. To obtain a sodium water glass solution with a modulus of 1.6, the Na2O content in the sodium water glass with a modulus of 3.3 can be set as x. According to formulas (5) and (6), the amount of Na2O added is calculated to be 9.07%, the relative molecular weight of Na2O is 62, and the relative molecular weight of NaOH is 80. According to formula (7), the amount of NaOH added is calculated to be 11.7%. Na2SiO3+2NaOH→Na2SiO3+Na2O+H2O (4) 3.3 / 1.6＝x / 8.54 (5) 17.61％-8.54％＝9.07％ (6) (80×9.07％)×62＝11.7％ (7)。 5. The alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material according to claim 1, characterized in that: The fineness modulus of the fine sand is 1.86, and the mud content is 1.68%; the water reducer is a naphthalene-based water reducer; and the retarder is barium nitrate.

6. A method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Weigh fly ash, silica fume, and slag to make a cementitious powder, and separately take fine sand, a water reducer, and a retarder. Place the above materials in a mixer and dry stir for 5 minutes to make the powder mix evenly; (2) According to the liquid-to-solid ratio of 0.7-1.0, weigh the alkali-activated solution according to 70%-100% of the mass of the gelling powder, slowly add it to the uniformly mixed powder and continue stirring for 3 minutes to obtain the grouting material.

7. The preparation method according to claim 6, characterized in that: The mixer is a JJ-5 planetary cement mortar mixer.

8. An alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material as claimed in claims 1 to 5, characterized in that: The cementitious powder ratio is 72% fly ash, 20% slag and 8% silica fume, the alkali-activated solution modulus is 1.6, the alkali content is 8% and the liquid-to-solid ratio is 0.

9.

9. A method for preparing the alkali-activated fly ash-slag-silica fume ternary-based shield synchronous grouting material as claimed in claims 1 to 6, characterized in that: The following steps are involved: (1) Weigh the cementitious powder material with a ratio of 72% fly ash, 20% slag and 8% silica fume, and separately take fine sand, water reducer and retarder, place the above materials in a mixer and dry stir for 5 minutes to make the powder material evenly mixed; (2) Based on a liquid-to-solid ratio of 0.9, an alkali-activated solution with a modulus of 1.6 is weighed at 90% of the mass of the gelled powder, wherein the alkali content of the solution is 8%, and then slowly added to the uniformly mixed powder and stirred for 3 minutes to obtain the grouting material.

10. An application of the alkali-activated fly ash-slag-silica fume ternary shield synchronous grouting material according to any one of claims 1 to 5 in shield tunnel construction, characterized in that: The grouting material is suitable for water-rich gravel strata, and slurry that meets different engineering requirements can be prepared by adjusting the alkali content or the liquid-solid ratio.

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