Mining alkaline slag coal gasification coarse slag cement mortar and preparation method thereof

Abstract

The invention belongs to the technical field of mortar materials, and particularly discloses mining alkaline residue and coal gasification coarse residue cement mortar and a preparation method thereof.The cement mortar is prepared by mixing alkaline residues, coal gasification coarse residues, yellow sand, cement and water; wherein the mass ratio of the alkaline residues to the coal gasification coarse residues to the yellow sand to the cement to the water is (0.03-0.18): (1.073-1.379): (1.686-1.992): 2: 1. Compared with the prior art, yellow sand in a traditional cement mortar material is partially replaced with the coal gasification coarse slag, and the effect of filling internal pores of mortar is achieved; caCl2, NaCl and other internally-doped chlorine salts rich in the alkaline residues can be combined with the cement mortar, the hydration reaction of the cement mortar is promoted, the strength is improved, and the defect that the strength performance is reduced due to the fact that yellow sand is replaced by the coal gasification coarse residues is overcome; under the combined action of the coal gasification slag and the alkaline slag, the alkaline slag and coal gasification coarse slag cement mortar provided by the invention has the performance equivalent to that of the traditional cement mortar, and resource utilization of the alkaline slag and coal gasification coarse slag solid waste is realized at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of mortar materials, and relates to a coal mine tunnel surface spraying mortar material, in particular to a mining alkali slag coal gasification coarse slag cement mortar and a preparation method thereof. Background Art

[0002] my country's ammonia-soda process can produce up to 4.21 million tons of soda ash annually. For every ton of soda ash produced, 0.3-0.6 tons of soda ash residue is discharged. For a plant producing 800,000 tons of soda ash annually, waste residue disposal costs are approximately 10 million yuan annually. The main components of soda ash residue are CaCO₃, CaSO₄·2H₂O, and Ca(OH)₂. Soluble salts account for over 20% of the total, primarily chlorides (CaCl₂ and NaCl), resulting in an extremely high chloride ion content. The current comprehensive utilization rate of solid waste soda residue is less than 4%, significantly below the national requirement for bulk solid waste utilization. Soda residue is typically deposited on the surface, which can easily pollute the surrounding sea.

[0003] Annual emissions of coal gasification slag as solid waste exceed 60 million tons, and are rapidly increasing at 35 million tons per year. The comprehensive utilization rate is less than 8.12%, far below the national target of 60%. Coal gasification slag contains some ungasified carbon, heavy metals, and fine particulate matter. If not properly handled, it can cause significant damage and pollution to soil, water, and the atmosphere.

[0004] A layer of mortar is sprayed on the surrounding rock surface around the roadway to prevent weathering, flaking, and water softening caused by exposure to air, thereby avoiding localized collapse. The sprayed layer forms a dense barrier, reducing groundwater infiltration into the roadway, preventing swelling or softening of the surrounding rock due to water infiltration, and mitigating the risk of water inrush. Timely spraying prevents the fall of surrounding rock fragments, ensuring the safety of construction personnel and equipment, while also improving construction efficiency and reducing the risk of accidents.

[0005] Traditional shotcrete materials are composed of cement, sand, gravel, water, and admixtures. The construction process consumes a large amount of raw materials and is costly. Research has shown that both coal gasification slag and alkali slag have the potential to be used in cement mortar materials. Coarse coal gasification slag has a lower carbon content than fine slag, is similar in particle size to sand, and has a graded distribution, making it a suitable alternative to yellow sand. The CaCO3 particles in alkali slag have a filling effect, and the rich internal chloride salts such as CaCl2 and NaCl combine with cement to increase the material's unconfined compressive strength. Currently, there are applications where either coal gasification slag or alkali slag has been added to cement mortar materials. However, research on the simultaneous addition of both types of solid waste to cement mortar materials is limited, and there is still a gap. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide a mining alkali slag coal gasification coarse slag cement mortar. The present invention utilizes the characteristics of the coal gasification coarse slag having a surface of mostly dense and multi-angular particles and a particle size composition similar to that of natural fine aggregate yellow sand to partially replace the yellow sand in traditional cement mortar materials, thereby filling the internal pores of the mortar. The alkali slag is rich in internal chlorine salts such as CaCl2 and NaCl, which will combine with the cement mortar. Under the condition of appropriate dosage, it can promote its hydration reaction and improve the strength, thereby compensating for the decrease in strength performance caused by the replacement of yellow sand by coal gasification coarse slag. Under the combined action of coal gasification slag and alkali slag, the alkali slag coal gasification coarse slag cement mortar provided by the present invention has performance comparable to that of traditional cement mortar, thereby realizing the resource utilization of alkali slag and coal gasification coarse slag solid waste in the mining field, and effectively solving the problems in the background technology. Another object of the present invention is to provide a preparation method of the cement mortar.

[0007] The present invention is achieved through the following technical solutions: A mining alkali slag coal gasification coarse slag cement mortar is prepared by mixing alkali slag, coal gasification coarse slag, yellow sand, cement and water; Among them, the mass ratio of alkali slag, coal gasification coarse slag, yellow sand, cement and water is 0.03-0.18:1.073-1.379:1.686-1.992:2:1.

[0008] A further improvement of the present invention is: The mass ratio of the alkali residue, coal gasification coarse residue, yellow sand, cement and water is 0.03-0.18:1.226:1.839:2:1.

[0009] Furthermore, the mass ratio of the alkali residue, coal gasification coarse residue, yellow sand, cement and water is 0.06:1.226:1.839:2:1.

[0010] A further embodiment of the present invention is: A method for preparing mining alkali slag coal gasification coarse slag cement mortar comprises the following steps: S1. Raw material quality control: Dry and crush the alkali residue and coal gasification residue for future use; S2. Mixing: according to the mass ratio, weigh the alkali residue treated in S1, coal gasification coarse slag, cement, yellow sand and water, put them into the underground mixer in turn for mixing, and obtain the alkali residue coal gasification coarse slag cement mortar for mining.

[0011] A further improvement of the present invention is: In S1, the moisture content of the dried alkali slag and coal gasification coarse slag is controlled to be less than 5%.

[0012] A further improvement of the present invention is: In S1, the nominal maximum particle size of the crushed alkali slag and coal gasification coarse slag is 4.75 mm. Beneficial effects

[0013] Compared with the prior art, the present invention has the following obvious advantages: 1. The present invention provides a mining alkali slag coal gasification coarse slag cement mortar, which utilizes the characteristics that the surface of the coal gasification coarse slag is mostly dense and multi-angular particles, and the particle size composition is similar to that of natural fine aggregate yellow sand, to partially replace the yellow sand in traditional cement mortar materials, and plays the role of filling the internal pores of the mortar; the alkali slag is rich in CaCl2 and NaCl and other internal chlorine salts, which will combine with the cement mortar. Under the condition of appropriate dosage, it can promote its hydration reaction and improve the strength, making up for the decline in strength performance caused by the coal gasification coarse slag replacing yellow sand; under the combined action of coal gasification slag and alkali slag, the alkali slag coal gasification coarse slag cement mortar provided by the present invention has performance comparable to that of traditional cement mortar, and can be applied in actual production.

[0014] 2. The present invention provides a new type of cement mortar material. By adding alkali slag and coal gasification coarse slag to traditional cement mortar, it provides a new way for the resource utilization of the two types of industrial solid wastes. It can not only realize the comprehensive utilization of solid waste resources and reduce their adverse effects on the environment, but also save engineering costs.

[0015] 3. The preparation method provided by the present invention has a simple raw material processing process, a short preparation process, is easy to reproduce, and is suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a dot-line graph of the unconfined compressive strength of specimens A0-A5 at 28 days from the coal gasification slag dosage design test in Example 1; Figure 2 This is a dot-line graph of the unconfined compressive strength of specimens K0-K4 at 28 days from the alkali slag dosage design test in Example 2; Figure 3 This is a dot-line graph of the unconfined compressive strength of specimens B1-B5 at 28 days from the alkali slag dosage verification test in Example 8; Figure 4 This is a dot-line graph of the unconfined compressive strength of specimens C1-C5 at 28 days from the coal gasification slag dosage verification test in Example 9; Figure 5 Comparison diagram of cross sections of some test specimens from Example 1, where (a) is A0, (b) is A2, and (c) is A3; Figure 6 Unconfined compressive strength test diagram of the specimen; Figure 7 This is an overall view of the finished product of some test pieces in Example 1. DETAILED DESCRIPTION

[0017] Raw material quality control: Alkali residue and coal gasification coarse residue are dried, the moisture content is controlled to less than 5%, crushed and ground, and then sieved through a 4.75mm square hole sieve for later use; yellow sand is natural river sand; cement and water are both commercially available.

[0018] The following is a detailed introduction to the material mass ratio design process of the mortar provided by the present invention in conjunction with Examples 1-2.

[0019] Example 1: Coal gasification slag dosage design test 1. Test Method: Based on the ability of coal gasification slag to replace yellow sand, six test groups, A0-A5, were planned to determine the mass ratio range of coal gasification slag. A0 was the control group (i.e., without coal gasification slag), and the mass ratio of the materials used was yellow sand: cement: water = 3.065:2:1. The mass ratios of coal gasification slag in groups A1-A5 were 0.613, 1.226, 1.839, 2.452, and 3.065, respectively. The mass ratios of the materials used to prepare the specimens in each group are shown in Table 1 below, and the specimen mass calculation table is shown in Table 2 below.

[0020] Table 1 Material mass ratio of A0-A5 compression test pieces

[0021] Table 2 A0-A5 compression test piece mass calculation table

[0022] 2. Specimen preparation: (1) Weighing: During the weighing process, ensure that the material container is dry and measure the required weight of the materials according to Table 2 above.

[0023] (2) Mixing materials: Add the weighed materials in sequence, mix them, and add water several times to mix them to ensure that the mixed materials are dense and do not separate.

[0024] (3) Mold loading: Before loading, wipe the triple test mold (70.7mm×70.7mm×70.7mm) clean and apply a thin layer of mineral oil on the inner wall of the mold to prevent the test piece and the mold from sticking together during demolding. When loading, use a spatula to tamp along the inner wall of the test mold to remove the air in the mold.

[0025] (4) Vibration: Place the assembled mold on a vibration table to further expel bubbles.

[0026] (5) Initial setting: Place the vibrated mold at room temperature and wait for 24 hours for initial setting.

[0027] (6) Demolding: Use the manual demoulding method, gently turn the specimen over so that the surface is facing down, lift both sides of the test mold with both hands, shake the test mold up and down to make it fall out, and mark the number on the specimen.

[0028] The A0-A5 specimens were placed in a YH-40B curing box under standard conditions of 25±2℃ and relative humidity above 92% for curing. After 28 days of curing, the specimens were taken out and unconfined compressive strength was tested using a WAW-1000B electro-hydraulic servo universal material testing machine. The data were recorded and a dot-line graph was drawn. The test results are shown in Table 3 below and the dot-line graph is shown in Table 3 below. Figure 1 .

[0029] Table 3 Unconfined compressive strength test results of specimens A0-A5 at 28 days

[0030] Conclusion: According to the above table and Figure 1 It can be seen that as the mass ratio of gasification coarse slag increases, the compressive strength of the specimen decreases compared to the control group A0. When the mass ratio of gasification coarse slag is in the range of 0.613-1.226, the compressive strength recovers. When the mass ratio of gasification coarse slag is greater than 1.226, the compressive strength gradually decreases and no longer recovers.

[0031] Based on these conclusions, the standard for the addition of gasification slag was established: after addition, the 28-day compressive strength of the specimens must be no less than 90% of the A0 control group. This standard was met when the mass ratio of gasification slag was between 1.073 and 1.379, and the specimens achieved optimal strength performance when the mass ratio was 1.226.

[0032] Example 2: Alkali slag dosage design test 1. Test Method: Based on the mass ratio of coal gasification coarse slag determined in Example 1, five test groups, K0-K4, were designed to determine the mass ratio range of alkali slag. K0 was the control group (i.e., containing no alkali slag), and the mass ratio of the materials used was coal gasification coarse slag: yellow sand: cement: water = 1.226:1.839:2:1. The mass ratios of alkali slag in groups K1-K4 were 0.06, 0.12, 0.18, and 0.24, respectively. The mass ratios of the materials used to prepare the specimens in each group are shown in Table 4 below, and the specimen mass calculation table is shown in Table 5 below.

[0033] Table 4 Material mass ratio of K0-K4 compression test pieces

[0034] Table 5 K0-K4 compression test piece mass calculation table

[0035] 2. Specimen preparation: The specific preparation steps are the same as those in Example 1.

[0036] After the preparation of K0-K4 specimens, they were left to stand for 28 days and subjected to unconfined compressive strength test. The specific curing conditions and compressive strength test method were the same as those in Example 1. The data were recorded and a dot-line graph was drawn. The test results are shown in Table 6 below. Figure 2 .

[0037] Table 6 Compressive strength test results of specimens K0-K4 at 28 days

[0038] Conclusion: According to the above table and Figure 2 It can be seen that as the mass ratio of alkali slag increases, the compressive strength of the specimens increases compared to the control group K0. When the mass ratio of alkali slag is less than 0.06, the compressive strength increases significantly; when the mass ratio of coal gasification slag is greater than 0.06, the compressive strength gradually decreases, but is still higher than the control group K0.

[0039] Based on the above conclusions, the standard for the addition of alkali residue was determined as follows: after addition, the 28-day compressive strength of the specimen was no less than that of the control group A0 in Example 1. This standard was met when the alkali residue mass ratio was in the range of 0.03-0.18, and the specimen's strength performance was optimal when the alkali residue mass ratio was 0.06.

[0040] Based on Examples 1-2, it is determined that the mass ratio of materials used in the mortar provided by the present invention is: alkali slag: coal gasification coarse slag: yellow sand: cement: water = 0.03-0.18: 1.073-1.379: 1.686-1.992: 2: 1, preferably: alkali slag: coal gasification coarse slag: yellow sand: cement: water = 0.06: 1.226: 1.839: 2: 1.

[0041] The actual strength performance of the mortar provided by the present invention is described in detail below in conjunction with Examples 3-9.

[0042] Examples 3-7 1. Test method: According to the mining alkali slag coal gasification coarse slag cement mortar and its preparation method provided by the present invention, five groups of tests were set up. The mass ratio of the preparation materials used in each group of specimens is shown in Table 7 below, and the specimen mass calculation table is shown in Table 8 below.

[0043] Table 7 Material mass ratio of compression test pieces of Example 3-7

[0044] Table 8 Calculation table of mass of compression test pieces of Example 3-7

[0045] 2. Specimen preparation: The specific preparation steps are the same as those in Example 1.

[0046] Comparative Example 1 1. Test method: A control group was set up without adding alkali slag and coal gasification coarse slag. The mass ratio of the remaining specimen materials was yellow sand: cement: water = 3.065:2:1. The specific material mass was calculated as follows: yellow sand 1317.95g, cement 860g, and water 430g.

[0047] 2. Specimen preparation: The specific preparation steps are the same as those in Example 1.

[0048] After the specimens of Examples 3-7 and Comparative Example 1 were prepared, they were left to stand and cured for 28 days, and then subjected to unconfined compressive strength tests. The specific curing conditions and compressive strength test methods were the same as those of Example 1. The data were recorded, and the test results are shown in Table 9 below.

[0049] Table 9 Unconfined compressive strength test results of specimens of Examples 3-7 and Comparative Example 1 at 28 days of age

[0050] Conclusion: According to the above table, the 28d average unconfined compressive strength of the specimens of Examples 3-7 is higher than that of Comparative Example 1 (the control group without the addition of alkali slag and coal gasification coarse slag), which proves that the alkali slag coal gasification coarse slag cement mortar provided by the present invention has excellent performance, which is equivalent to traditional cement mortar and can meet the actual production requirements.

[0051] Example 8-9: Alkali slag and coal gasification slag dosage verification test 1. Test method: (1) Alkali slag dosage verification test: Under the condition of a fixed coal gasification coarse slag dosage, the alkali slag mass ratio of the mortar provided by the present invention is 0.03-0.18. Five groups of tests, B1-B5, are set. The mass ratios of the materials used to prepare the specimens in each group are shown in Table 10 below, and the specimen mass calculation table is shown in Table 11 below.

[0052] (2) Coal gasification slag dosage verification test: Under the condition of fixed alkali slag dosage, according to the mass ratio of coal gasification coarse slag: 1.839-3.065 (larger than the mass ratio range of coal gasification coarse slag of the mortar provided by the present invention), five groups of tests C1-C5 are set. The mass ratio of the preparation materials used for each group of specimens is shown in Table 12 below, and the specimen mass calculation table is shown in Table 13 below.

[0053] Table 10 Alkali slag dosage verification test: Material mass ratio of B1-B5 compression test pieces

[0054] Table 11 Alkali slag dosage verification test: B1-B5 compression test piece mass calculation table

[0055] Table 12 Coal gasification slag dosage verification test: C1-C5 compression test piece material mass ratio

[0056] Table 13 Coal gasification slag dosage verification test: C1-C5 compression test piece mass calculation table

[0057] 2. Specimen preparation: The specific preparation steps are the same as those in Example 1.

[0058] After the preparation of B1-B5 and C1-C5 specimens, they were left to stand for 28 days and subjected to unconfined compressive strength test. The specific curing conditions and compressive strength test method were the same as those in Example 1. The data were recorded and a dot-line graph was drawn. The test results are shown in Tables 14-15 below. Figure 3-4 .

[0059] Table 14 Unconfined compressive strength test results of specimens B1-B5 at 28 days

[0060] Conclusion: By comparing the data in the above table with comparative example 1, it can be seen that when the mass ratio of coal gasification slag is 1.226 and the mass ratio of alkali slag is in the range of 0.03-0.18, the obtained specimens have good strength properties, which are higher than traditional cement mortar; when the mass ratio of alkali slag is 0.06, the strength performance of the specimen is optimal.

[0061] Table 15 Unconfined compressive strength test results of specimens C1-C5 at 28 days

[0062] Conclusion: By comparing the data in the above table with comparative example 1, it can be seen that when the mass ratio of alkali slag is 0.06 and the mass ratio of coal gasification coarse slag is in the range of 1.839-3.065, the strength performance of the obtained specimen is lower than that of traditional cement mortar, showing a downward trend; when the amount of coal gasification coarse slag added is greater than the mass ratio range described in the method provided by the present invention, the addition of alkali slag cannot restore the strength of the cement mortar to meet the compressive strength standard of traditional cement mortar.

[0063] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A mining alkali slag coal gasification coarse slag cement mortar, characterized in that: It is prepared by mixing alkali residue, coal gasification coarse residue, yellow sand, cement and water; Among them, the mass ratio of alkali slag, coal gasification coarse slag, yellow sand, cement and water is 0.03-0.18:1.073-1.379:1.686-1.992:2:

1.

2. The mining alkali slag coal gasification coarse slag cement mortar according to claim 1, characterized in that: The mass ratio of the alkali residue, coal gasification coarse residue, yellow sand, cement and water is 0.03-0.18:1.226:1.839:2:

1.

3. The mining alkali slag coal gasification coarse slag cement mortar according to claim 2, characterized in that: The mass ratio of the alkali residue, coal gasification coarse residue, yellow sand, cement and water is 0.06:1.226:1.839:2:

1.

4. A method for preparing mining alkali slag coal gasification coarse slag cement mortar according to any one of claims 1 to 3, characterized in that: The steps include: S1. Raw material quality control: Dry and crush the alkali residue and coal gasification residue for future use; S2. Mixing: according to the mass ratio, weigh the alkali residue treated in S1, coal gasification coarse slag, cement, yellow sand and water, put them into the underground mixer in turn for mixing, and obtain the alkali residue coal gasification coarse slag cement mortar for mining.

5. The method for preparing a mining alkali slag coal gasification coarse slag cement mortar according to claim 4, characterized in that: In S1, the moisture content of the dried alkali slag and coal gasification coarse slag is controlled to be less than 5%.

6. The method for preparing a mining alkali slag coal gasification coarse slag cement mortar according to claim 4, characterized in that: In S1, the nominal maximum particle size of the crushed alkali slag and coal gasification coarse slag is 4.75 mm.

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