Cement-ardealite-water glass solidified engineering muck mixed filler and preparation method thereof

Abstract

The invention discloses a cement-ardealite-water glass solidified engineering muck mixed filler and a preparation method thereof. The mixed filler comprises the following raw materials: engineering residue soil, cement, ardealite, water glass and water, wherein the mass ratio of the engineering residue soil to the cement to the ardealite to the water glass is 100: (10-15): (1-3): (0.5-1.5); the preparation method comprises the following steps: mixing the engineering residue soil, the cement, the crushed ardealite and the water, and then adding the water glass for mixing. The mixed filler can be applied to backfilling of fertilizer grooves or pipeline pit grooves, resource utilization of engineering residue soil and bulk solid waste is achieved, the mixed filler has important social and economic significance in reducing occupation of scarce land resources caused by industrial waste accumulation, reducing environmental pollution hazards and saving construction cost, and the mixed filler is simple in preparation engineering and low in cost. Raw materials are easily available, and popularization in engineering practice is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a cement-phosphogypsum-water glass solidified engineering slag mixed filler and a preparation method thereof. Background Art

[0002] The rapid development of infrastructure construction has generated a large amount of construction waste (including excavation waste and shield tunneling waste). Due to its poor engineering properties, this waste is often transported and discarded, increasing project costs and wasting soil resources. In recent years, the increasing scale of underground construction and the amount of waste have led to saturated landfill sites in many cities. Efficiently disposing of this rapidly growing amount of waste has become a critical issue for urban construction and social development.

[0003] Phosphogypsum is a solid waste residue from the industrial production of phosphoric acid. Because it contains soluble, harmful components, it is difficult to use directly in the production of building materials. Disposal of this massive accumulation of phosphogypsum is an urgent issue. Waterglass, an aqueous solution of sodium silicate, reacts with cement to rapidly solidify. It is often used in grouting to block water and prevent seepage, and it also provides an alkaline environment for cement hydration.

[0004] Cement is a common curing agent, and its hydration products are the main factor in forming strength, playing a major role in the curing of construction waste. During its reaction with cement, phosphogypsum produces needle-rod-shaped ettringite, which forms a spatial network structure with the hydration products, improving the strength of the cured construction waste. However, phosphogypsum has a certain retarding effect, and often fails to reach the required strength in the early stages of the reaction. To meet the rapid hardening and early strength requirements of engineering projects, it is necessary to add an appropriate amount of water glass. Water glass reacts rapidly with cement to produce a gelling agent, greatly improving the early strength of cured construction waste. Therefore, if a suitable curing agent ratio can be optimized so that the cured construction waste meets the requirements of foundation pit backfill and is economically efficient, this will not only achieve the disposal of construction waste, but also realize the resource utilization of large amounts of solid waste; it has important technical value in reducing environmental pollution, construction costs, and construction time. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a cement-phosphogypsum-water glass solidified engineering slag mixed filler, the raw materials of which include: engineering slag, cement, phosphogypsum, water glass and water; wherein the mass ratio of engineering slag, cement, phosphogypsum and water glass is 100:10-15:1-3:0.5-1.5.

[0006] Furthermore, the cement is PO 42.5 ordinary Portland cement, and the proportions of CaO and SiO2 in the cement are 62% and 22% respectively.

[0007] Furthermore, the content of CaSO4·2H2O in the phosphogypsum is above 90%.

[0008] Furthermore, the Baume degree of the water glass is 38.5, the modulus is 3.30, the pH value is 10-13, and the contents of Na2O and SiO2 are 8.53% and 26.98% respectively.

[0009] A second object of the present invention is to provide a method for preparing the above-mentioned cement-phosphogypsum-water glass solidified engineering slag mixed filler, comprising the following steps:

[0010] Step 1: crush the phosphogypsum for standby use and measure the initial moisture content of the construction waste soil;

[0011] Step 2: Calculate the amount of water to be added to the mixed filler based on the backfill soil requirements and the initial moisture content of the construction waste soil;

[0012] Step 3: Mix construction waste soil, cement, crushed phosphogypsum and water, and then add water glass for mixing;

[0013] Step 4: backfill the mixed filler obtained in step 3 and then perform curing.

[0014] The backfill soil requirements include strength, strength development time and workability. If higher strength is required, the cement content and phosphogypsum content can be appropriately increased; if the strength requirements need to be reached earlier, the water glass content can be appropriately increased.

[0015] The principle of the present invention is that cement, a common curing agent, produces a certain strength after its hydration product bonds with the soil particles. During the reaction between phosphogypsum and cement, needle-rod-shaped ettringite is produced. This forms a spatial network structure with the hydration product, improving the strength of the solidified construction soil. However, phosphogypsum has a certain retarding effect, often failing to reach the required strength in the early stages of the reaction. To meet the rapid hardening and early strength requirements of the project, water glass reacts rapidly with cement to produce a gelling substance, significantly improving the early strength of the solidified construction soil.

[0016] This invention addresses the technical deficiencies of existing construction waste disposal methods, including the high cost of backfilling foundation pits. By designing a cement-phosphogypsum-water glass solidified construction waste mixed filler and its preparation method, the invention addresses the disposal of construction waste and the comprehensive resource utilization of large quantities of solid waste. Using the solidified waste as foundation pit filler eliminates the cost of transporting the waste and the need for storage space. Furthermore, the rapid hardening and early strength of the solidified waste significantly increases construction speed and reduces maintenance costs.

[0017] Compared with the existing technology, this application has the following advantages:

[0018] 1. The solidified construction waste mixed filler reduces the land resources occupied by construction waste stacking and the cost of transportation. At the same time, the improved construction waste backfill replaces traditional backfill materials (sand, gravel), reducing the consumption of natural resources and having important social value and economic benefits.

[0019] 2. The solidified engineering slag mixed filler comprehensively utilizes phosphogypsum waste, solidifies metal ions by physical adsorption and chemical reaction, and has a good long-term solidification effect on soluble phosphorus, soluble fluorine and other heavy metal ions in phosphogypsum, thereby reducing the risk of pollution to the surrounding environment caused by phosphogypsum storage.

[0020] 3. The preparation process of the cement-phosphogypsum-water glass solidified engineering slag mixed filler of the present invention is simple and does not increase the technical difficulty of on-site construction.

[0021] 4. The cement-phosphogypsum-water glass solidified engineering slag mixed filler of the present invention has high strength in the early stage. The unconfined compressive strength can reach 0.1-0.3 MPa after 1 day of standard curing, which can meet the needs of people walking on it; the 28-day strength can reach 1.2 MPa-1.8 MPa, which can basically meet the strength requirements of foundation pit backfill soil, and the economic cost is low, which is conducive to the promotion of engineering technology.

[0022] 5. The cement-phosphogypsum-water glass solidified engineering slag mixed filler of the present invention reduces the amount of cement used by adding water glass and phosphogypsum, and can effectively save curing time and construction period, and the construction quality is better than that of traditional construction methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The unconfined compressive strength and permeability coefficient test results of the mixed filler samples in the examples and comparative examples are shown. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0026] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0027] In the following examples, the construction waste soil was excavated from a foundation pit in a project in Nanjing's Southern New Town. This soil is classified as silty clay, with a liquid limit of 33.6% and a plastic limit of 16.8%. The cement is ordinary Portland cement with a PO42.5 ratio, containing 62% CaO and 22% SiO2. The phosphogypsum is produced using a wet process, using a pulverizer to crush air-dried phosphogypsum from a phosphogypsum yard. The powder has a natural moisture content of 20.7%, and the CaSO4·2H2O content in the phosphogypsum is above 90%. The water glass was obtained from a refractory materials company in Jiashan County. Testing revealed a Baume degree of 38.5, a modulus of 3.30, a pH of 10-13, and Na2O and SiO2 contents of 8.53% and 26.98%, respectively.

[0028] The following examples test and analyze the mechanical strength properties of cement-phosphogypsum-water glass solidified engineering slag mixed filler through unconfined compressive strength tests. The permeability coefficient of cement-phosphogypsum-water glass solidified engineering slag mixed filler is tested and analyzed through flexible wall permeability tests.

[0029] Example 1

[0030] A cement-phosphogypsum-water glass solidified construction waste mixed filler, wherein the construction waste, cement, phosphogypsum and water glass are mixed in the following proportions by mass: 100 parts of construction waste, 15 parts of cement, 1.5 parts of phosphogypsum and 0.75 parts of water glass.

[0031] The preparation method of the cement-phosphogypsum-water glass solidified engineering slag mixed filler specifically comprises the following steps:

[0032] Step 1: Prepare the materials, including construction waste soil and the cement, phosphogypsum, and water glass used. Use a pulverizer to crush the original phosphogypsum, and control the particle size of the phosphogypsum to 2mm; measure the initial moisture content of the construction waste soil and calculate the water required to be added.

[0033] Step 2: Calculate the mass of water required to be added based on the water-to-solid ratio of the mixed filler (about 0.6) and the initial moisture content of the construction waste soil.

[0034] Step 3: Mix the weighed construction waste soil, cement and phosphogypsum with appropriate amount of water, and then add water glass and mix well.

[0035] Step 4: backfilling and curing, backfilling the obtained solidified engineering slag, properly leveling the site and then curing, to obtain the cement-phosphogypsum-water glass solidified engineering slag mixed filler.

[0036] Sample preparation: Samples were prepared according to the method specified in the "Standard for Geotechnical Test Methods" (GB-T 50123-2019) using cylindrical specimens measuring 3.91 cm × 8 cm. Permeability coefficient samples were prepared using a 5 cm × 10 cm cylindrical mold. After demolding, the samples were placed in a ziplock bag and cured in a standard curing room (20°C ± 2°C, humidity ≥ 95%). After curing for 1, 3, 7, and 28 days, the soil was removed for unconfined compressive testing to determine the unconfined compressive strength of the solidified construction waste soil. The loading rate was controlled at 1 mm / min. After 28 days, the permeability samples were removed and tested using a flexible wall permeameter.

[0037] Table 1 Unconfined compressive strength test data of solidified engineering slag mixed filler in Example 1

[0038]

[0039] Example 2

[0040] A cement-phosphogypsum-water glass solidified construction waste mixed filler, the preparation method of which is roughly the same as that of Example 1, except that the mass proportions of the raw materials are: 100 parts of construction waste, 15 parts of cement, 1.5 parts of phosphogypsum, and 1.5 parts of water glass.

[0041] Table 2 Unconfined compressive strength test data of solidified engineering slag mixed filler in Example 2

[0042]

[0043] Example 3

[0044] A cement-phosphogypsum-water glass solidified construction waste mixed filler, the preparation method of which is roughly the same as that of Example 1, except that the mass proportions of the raw materials are: 100 parts of construction waste, 15 parts of cement, 3 parts of phosphogypsum, and 0.75 parts of water glass.

[0045] Table 3 Unconfined compressive strength test data of solidified engineering slag mixed filler in Example 3

[0046]

[0047] Example 4

[0048] A cement-phosphogypsum-water glass solidified construction waste mixed filler, the preparation method of which is substantially the same as that of Example 1, except that the mass proportions of the raw materials are: 100 parts of construction waste, 15 parts of cement, 3 parts of phosphogypsum, and 1.5 parts of water glass.

[0049] Table 4 Unconfined compressive strength test data of solidified engineering slag mixed filler in Example 4

[0050]

[0051] Comparative Example 1

[0052] A cement-phosphogypsum-water glass solidified construction waste soil mixed filler, the preparation method of which is substantially the same as that of Example 1, except that the mass proportions of the raw materials are: 100 parts of construction waste soil, 15 parts of cement, 0 parts of phosphogypsum, and 0 parts of water glass.

[0053] Table 5 Unconfined compressive strength test data of solidified engineering slag mixed filler in comparative example 1

[0054]

[0055] It can be concluded from Table 1-4 that the strength of the cement-phosphogypsum-water glass solidified engineering slag mixed filler can reach 0.13MPa at the age of 1 day, which fully meets the needs of the superior. When the added phosphogypsum is 3 parts, the early strength of the solidified engineering slag is lower than that of the ratio of 1.5 parts of phosphogypsum due to the retarding effect of phosphogypsum, but the 28d strength has increased; the addition of water glass is beneficial to the early strength and late strength of the solidified engineering slag, but because water glass reacts quickly with cement, a high water glass content will reduce the workability of the material. The 28d permeability coefficients of Examples 1-4 are all above 10 -8 , 10 -9 This shows that the density and impermeability of solidified engineering waste have been greatly improved, effectively reducing the environmental problems caused by the overflow of phosphogypsum impurities.

[0056] Compared with Comparative Example 1, Examples 1-4 all showed significant improvements in their 3d, 7d, and 28d unconfined compressive strengths. However, due to the high amount of phosphogypsum added, which resulted in a strong retarding effect, and the relatively low amount of waterglass, Example 3 failed to achieve good early strength development, resulting in a lower 1d unconfined compressive strength than Comparative Example 1. However, after 3d, the strength of Example 3 caught up with that of Comparative Example 1, and its subsequent strength was significantly greater than that of Comparative Example 1, which only added cement. Regarding the 28d permeability coefficient, that of Comparative Example 1 was 1-2 orders of magnitude higher than that of the examples, demonstrating the significant role of phosphogypsum and waterglass in filling the pores of the slag. This demonstrates that the addition of phosphogypsum and waterglass in the slag-solidified cement-phosphogypsum-waterglass mixed filler effectively solidifies the soluble ions in the phosphogypsum, ensuring its environmental performance. The components of the cement-phosphogypsum-waterglass mixed filler for slag-solidified designed and prepared by the present invention exhibit good compatibility and synergistic effects, leveraging their respective strengths and providing a theoretical basis for practical application.

[0057] The cement-phosphogypsum-water glass solidified engineering slag mixed filler designed and prepared by the present invention has good mechanical strength and impermeability after treatment, and the amount of curing agent used is relatively small, and has good economic benefits. It can be used as a foundation pit backfill material, and is of great significance for improving the utilization of slag, the resource utilization of phosphogypsum, reducing the occupation of land resources by the accumulation of industrial and engineering waste, and reducing environmental pollution.

[0058] The above description is merely an illustration of the preferred embodiments of the present invention and is not intended to limit the scope of the present invention. For those skilled in the art, the above description may be subject to other variations and modifications, and any modifications, improvements, replacements, etc. made within the principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A cement-phosphogypsum-water glass solidified engineering slag mixed filler, characterized in that: Raw materials include construction waste, cement, phosphogypsum, water glass and water; The mass ratio of construction waste soil, cement, phosphogypsum and water glass is 100:10-15:1-3:0.5-1.

5.

2. The cement-phosphogypsum-water glass solidified engineering slag mixed filler according to claim 1, characterized in that: The cement is PO 42.5 ordinary Portland cement, and the proportions of CaO and SiO2 in the cement are 62% and 22% respectively.

3. The cement-phosphogypsum-water glass solidified engineering slag mixed filler according to claim 1, characterized in that: The content of CaSO4·2H2O in the phosphogypsum is above 90%.

4. The cement-phosphogypsum-water glass solidified engineering slag mixed filler according to claim 1, characterized in that: The water glass has a Baume degree of 38.5, a modulus of 3.30, a pH of 10-13, and contents of Na2O and SiO2 of 8.53% and 26.98% respectively.

5. The method for preparing the cement-phosphogypsum-water glass solidified engineering slag mixed filler according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: crush the phosphogypsum for standby use and measure the initial moisture content of the construction waste soil; Step 2: Calculate the amount of water to be added to the mixed filler based on the backfill soil requirements and the initial moisture content of the construction waste soil; Step 3: Mix construction waste soil, cement, crushed phosphogypsum and water, and then add water glass for mixing; Step 4: backfill the mixed filler obtained in step 3 and then perform curing.

6. The cement-phosphogypsum-water glass solidified engineering slag mixed filler according to any one of claims 1 to 4 is used to prepare foundation pit fertilizer tanks or pipeline pit backfill.

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