A silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material and a preparation method thereof

Abstract

The application discloses a kind of silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material and preparation method thereof, method includes the following steps: step 1, according to mass fraction, 100 parts of 30%~50% nano-silica sol, 50~60 parts aluminate cement, 30~36 parts water, 0.5~1 parts water reducing agent, 2.6~3.6 parts magnesium oxide and 4~6.6 parts natural zeolite are weighed respectively, for standby;Step 2, after mixing aluminate cement, magnesium oxide and natural zeolite, water and water reducing agent are added, high-speed stirring is obtained uniform slurry;Step 3, first, the pH value of nano-silica sol is adjusted to 6~10, then uniform slurry is added to nano-silica sol, and stirring is uniformly obtained silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material.The composite grouting material prepared by the application has high injectability, high strength, high impermeability and excellent heavy metal fixation performance.

Description

Technical Field

[0001] This invention relates to the compound modification of silica sol, specifically a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material and its preparation method. Background Technology

[0002] According to the "Code for Design of Tailings Facilities" (GB 50863-2013), for tailings ponds storing Class II general industrial solid waste and hazardous waste, the permeability coefficient of the anti-seepage system should not exceed 1×10⁻⁶. -7 In practical engineering, vertical curtain grouting technology is commonly used to construct seepage prevention systems for tailings ponds that have been built or have been closed but are experiencing leakage. Tailings pond leachate often contains various heavy metal ions such as lead, cadmium, copper, zinc, and arsenic. Vertical seepage prevention curtains not only need to effectively cut off seepage but also need to have the function of inhibiting the migration of heavy metals to prevent heavy metals from penetrating the curtain and causing water and soil pollution in the surrounding area.

[0003] Existing grouting materials are mainly divided into two categories: organic and inorganic. First, organic chemical grouts (such as acrylamide and polyurethane) have good seepage prevention effects, but are expensive, toxic, and lack specific adsorption capacity for heavy metal ions. Second, inorganic grouting materials mainly include cement-based grouts, water glass grouts, and nano-silica sols. Among them: 1) Cement-based grouts have the advantages of low cost and high hardened body strength, but the grout contains a large number of micron-sized solid particles, resulting in poor injectability and difficulty in penetrating nano-sized geological fissures, failing to meet high-level seepage prevention requirements. The retention of heavy metals mainly relies on physical encapsulation, which has a long-term... 1) Insufficient stability; 2) Water glass slurry has low viscosity, good injectability, low price and non-toxicity, but the gelation time and strength are unstable, the solidified body has a high dissolution rate in water, poor volume stability and durability, and weak adsorption affinity for dissolved heavy metals; 3) Nano-silica sol has received widespread attention in the field of inorganic grouting due to its low viscosity, good permeability, strong injectability and outstanding durability. However, the gelation process of single nano-silica sol has poor controllability, the strength of the solidified body is not high, and its surface is rich in silanols, which are highly hydrophilic. The solidified body is prone to water absorption and swelling, which leads to structural deterioration, and the impermeability is difficult to reach 1×10. -9 The speed is on the order of cm / s; at the same time, silica sols have inherently low adsorption capacity and poor selectivity for heavy metal ions, making them unable to effectively immobilize multiple heavy metals in leachate. Existing technologies generally control the gelation time of nano-silica sols by adding gelling agents or curing agents, but they have failed to simultaneously solve the problems of high impermeability and efficient heavy metal adsorption.

[0004] In summary, existing grouting materials cannot simultaneously meet the comprehensive performance requirements of high injectability, high strength, ultra-high impermeability, and good heavy metal adsorption. Therefore, there is an urgent need to develop a new type of modified silica sol-based grouting material that combines high injectionability, high strength, high impermeability, and excellent heavy metal fixation performance. Summary of the Invention

[0005] The purpose of this invention is to provide a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material and its preparation method. The prepared composite grouting material has high injectability, high strength, high impermeability and excellent heavy metal fixation performance.

[0006] This invention is achieved through the following technical solution: A method for preparing a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material includes the following steps: Step 1: Weigh out 100 parts of nano silica sol (30%~50% by mass), 50~60 parts of aluminate cement, 30~36 parts of water, 0.5~1 parts of water-reducing agent, 2.6~3.6 parts of magnesium oxide, and 4~6.6 parts of natural zeolite by mass, and set aside. Step 2: Mix aluminate cement, magnesium oxide and natural zeolite, then add water and water-reducing agent, and stir at high speed to obtain a uniform slurry; Step 3: First, adjust the pH value of the nano silica sol to 6-10, then add a uniform slurry to the nano silica sol and stir evenly to obtain a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material.

[0007] Furthermore, the water-reducing agent in step 1 is a retarding water-reducing agent, namely the DS-J2 retarding polycarboxylate-based high-performance water-reducing agent produced by Dr. Stone Technology Group Co., Ltd.

[0008] Furthermore, the purity of the magnesium oxide in step 1 is 93%~95%.

[0009] Furthermore, the natural zeolite in step 1 is clinoptilolite, mordenite, or chalcogenite.

[0010] Furthermore, the high-speed stirring in step 2 is carried out at a speed of 1000~1500 r / min for 5~10 min.

[0011] Furthermore, in step 3, the pH value of the nano-silica sol is adjusted to 6-10 using acetic acid.

[0012] A silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material has a compressive strength of 4.17~5.9 MPa after the composite grouting material is cured at room temperature for 28 days.

[0013] Furthermore, the permeability coefficient of the composite grouting material used for sand fixation is 2.11 × 10⁻⁶. -10 ~7.2×10 -11 cm / s.

[0014] Furthermore, composite grouting materials for Cd 2+The adsorption capacity of the ions is 36.25 ~ 40.20 mg·g. -1 .

[0015] The present invention has the following beneficial technical effects: 1) Excellent high impermeability: Utilizing the low viscosity and strong permeability of nano-silica sol, it can be effectively injected into nanoscale formation fractures, filling pore channels. Moreover, the hydration products of aluminate cement and silica sol gel form a dense three-dimensional network structure, which, in conjunction with the micro-expansion effect of magnesium oxide, solidifies the material into a dense solidified body, resulting in a permeability coefficient as low as 7.2 × 10⁻⁶. - 11 The flow rate is on the order of cm / s, meeting extremely stringent seepage prevention requirements; 2) High compressive strength and good volume stability: Aluminate cement provides the foundation for early and late strength. Silica sol participates in the hydration reaction to form a silicate gel reinforcing phase. Magnesium oxide compensates for gel drying shrinkage through moderate micro-expansion, reducing the risk of cracking of the cured body. This allows the material to maintain excellent impermeability while possessing high compressive strength and long-term structural stability. 3) High-efficiency adsorption and retention capacity of heavy metals: Natural zeolite has a high specific surface area and ion exchange performance, and exhibits strong adsorption affinity for a variety of heavy metal ions, including cadmium. At the same time, aluminate cement hydration products and silica sol gel can also fix heavy metal ions through surface complexation, chemical precipitation and physical encapsulation, achieving multiple synergistic adsorption and fixation, effectively inhibiting the migration of heavy metals, and can be used for the treatment of heavy metal leakage in tailings ponds. 4) Excellent injectability and construction adaptability: The silica sol grout has low viscosity. After being dispersed by water-reducing agent, the system has good fluidity and strong injectability, which can be injected into fine cracks. In addition, the gel time can be adjusted by the component ratio to adapt to the grouting construction requirements under different engineering conditions. 5) Moderate cost and environmentally friendly: The main components are all commercially available bulk inorganic materials, the cost is controllable, the materials are non-toxic and there is no organic solvent volatilization, which effectively reduces the environmental and health risks caused by organic chemical slurries. Attached Figure Description

[0016] Figure 1 The grouting material prepared in Example 1 for Cd 2+ The curve showing the change in adsorption capacity over time. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0018] The nano-silica sol used in Examples 1 to 48 of this invention was purchased from Qingdao Jiyida Silica Sol Reagent Co., Ltd.

[0019] The water-reducing agent selected in Examples 1 to 48 of this invention is a retarding water-reducing agent, namely DS-J2 retarding polycarboxylate-based high-performance water-reducing agent produced by Dr. Stone Technology Group Co., Ltd.

[0020] The magnesium oxide used in Examples 1 to 48 of this invention has a purity of 93% to 95%.

[0021] Example 1 Step 1: Weigh out 100 parts of 40% nano silica sol, 57 parts of aluminate cement, 36 parts of water, 0.7 parts of water-reducing agent, 3.6 parts of magnesium oxide, and 4.4 parts of mordenite according to the mass fraction. Step 2: Mix aluminate cement, magnesium oxide and mordenite, then add water and water-reducing agent, and stir at 1500 r / min for 5 min to obtain a uniform slurry. Step 3: First, adjust the pH value of the nano-silica sol to 6 using acetic acid, then add a uniform slurry and stir evenly to obtain a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material.

[0022] Examples 2 to 48 The difference between Examples 2 to 48 and Example 1 lies in the different raw material ratios, as shown in Table 1. In Examples 2 to 48, the mass fraction of nano-silica sol is 100 parts.

[0023] Table 1. Raw materials, their proportions, and process parameters for Examples 2 to 48 According to the method in the national standard "Viscosity Measurement Method" (GB / T10247-2008), the initial viscosity of the grouting materials prepared in Examples 1 to 48 was measured using a rotational viscometer, and the setting time was recorded. The results are shown in Tables 2 and 3, respectively. It can be seen that the initial viscosity of the grouting materials prepared in Examples 1 to 48 is 7.22~9.98 mPa·s, and the setting time is 32~895 min.

[0024] Table 2 Initial viscosity (mPa·s) of grouting materials prepared in Examples 1 to 48 Table 3. Setting time (in min) of grouting materials prepared in Examples 1 to 48 The silica sol grouting materials prepared in Examples 1 to 48 were poured into molds with a diameter of 90 mm and a height of 35 mm containing standard sand, allowing the grout to form a silica sol solid sand body within the mold. The top of the mold was covered with plastic wrap, and after standard curing for 7 days, the permeability coefficient of the silica sol solid sand body was tested using a mortar permeameter. The experimental procedure was as follows: water was injected into the silica sol solid sand body from the bottom using a mortar permeameter, allowing water to pass through the silica sol solid sand body sample. When water flowed out of the drain outlet of the mortar permeameter, the maximum pressure (H1) and minimum pressure (H2) on the instrument panel of the mortar permeameter and the starting time were recorded. The overflow water was collected, and the duration (t) was recorded. The amount of water collected (Q) was calculated to calculate the permeability coefficient. The results are shown in Table 4. It can be seen that the permeability coefficient of the solid sand body corresponding to the grouting materials prepared in Examples 1 to 48 is 2.11 × 10⁻⁶. -10 ~7.2×10 -11 cm / s.

[0025] Table 4. Permeability coefficients (unit: cm / s) of the grouting materials prepared in Examples 1 to 48 A detachable, thickened ABS plastic mold (a 50×50×50 cm triple mold) was used to cast the solidified sand. The test procedure was as follows: the uniformly mixed standard sand was poured into the pre-installed mold, and the silica sol grouting materials prepared in Examples 1 to 48 were injected into the standard sand until the liquid overflowed from the surface. Then, a small amount of standard sand was added to smooth the surface, and the upper surface was wrapped with plastic wrap. After curing at room temperature for 28 days, the mold was removed, and the volume change rate after 28 days of curing was calculated. The strength of the specimen was tested using a universal testing machine. The results are shown in Tables 5 and 6. It can be seen that the solidified sand corresponding to the grouting materials prepared in Examples 1 to 48 had a compressive strength of 4.17 to 5.9 MPa and a volume change rate of 0.00051 to 0.0199 after curing at room temperature for 28 days.

[0026] Table 5. Strength of grouting materials prepared in Examples 1 to 48 (unit: MPa) Table 6. Volume change rate of grouting materials prepared in Examples 1 to 48 After the silica sol grouting materials prepared in Examples 1 to 48 have solidified and cured for 3 days, they are placed in a vacuum drying oven to dry until their weight no longer changes. The materials are then ground and sieved. 0.2 g of the ground and sieved sample is taken and a 100 mg / L concentration of Cd is added. 2+In the solution, the sample was shaken at room temperature for 3 h to allow it to reach adsorption equilibrium. 3–5 mL of the supernatant was then taken and filtered through a 0.22 µm microporous membrane. The residual Cd in the supernatant was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ Ion concentrations, the results are shown in Table 7. It can be seen that the grouting materials prepared in Examples 1 to 48 have a positive effect on Cd. 2+ The adsorption capacity is 36.25 ~ 40.08 mg·g. -1 In addition, see Figure 1 It can be seen that the grouting material prepared in Example 1 reached adsorption equilibrium at 120 min, and its adsorption of Cd was satisfactory. 2+ The adsorption capacity reached 40.08 mg·g. -1 .

[0027] Table 7. Grouting materials prepared in Examples 1 to 48 and their effect on Cd 2+ Adsorption capacity (unit: mg·g) -1 )

Claims

1. A method for preparing a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material, characterized in that, Includes the following steps: Step 1: Weigh out 100 parts of nano silica sol (30%~50% by mass), 50~60 parts of aluminate cement, 30~36 parts of water, 0.5~1 parts of water-reducing agent, 2.6~3.6 parts of magnesium oxide, and 4~6.6 parts of natural zeolite by mass, and set aside. Step 2: Mix aluminate cement, magnesium oxide and natural zeolite, then add water and water-reducing agent, and stir at high speed to obtain a uniform slurry; Step 3: First, adjust the pH value of the nano silica sol to 6-10, then add a uniform slurry to the nano silica sol and stir evenly to obtain a silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material.

2. The preparation method of the silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 1, characterized in that, The water-reducing agent used in step 1 is a retarding water-reducing agent, namely DS-J2 retarding polycarboxylate-based high-performance water-reducing agent produced by Dr. Stone Technology Group Co., Ltd.

3. The preparation method of the silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 1, characterized in that, The purity of the magnesium oxide in step 1 is 93%~95%.

4. The preparation method of the silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 1, characterized in that, The natural zeolite used in step 1 is clinoptilolite, mordenite, or chalcogenite.

5. The preparation method of the silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 1, characterized in that, The high-speed stirring in step 2 is carried out at a speed of 1000~1500 r / min for 5~10 min.

6. The preparation method of the silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 1, characterized in that, In step 3, the pH value of the nano-silica sol is adjusted to 6-10 using acetic acid.

7. A silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material prepared by the method according to any one of claims 1 to 6, characterized in that, After the composite grouting material was cured at room temperature for 28 days, the compressive strength of the sand-stabilized body was 4.17~5.9MPa.

8. The silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 7, characterized in that, The permeability coefficient of the composite grouting material used for sand fixation is 2.11 × 10⁻⁶. -10 ~7.2×10 -11 cm / s.

9. The silica sol / aluminate cement / magnesium oxide / zeolite composite grouting material according to claim 7, characterized in that, For Cd 2+ The adsorption capacity of the ions is 36.25 ~ 40.20 mg·g. -1 .

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