A cement mortar thickening, flow increasing and reinforcing additive, its preparation method and application

Abstract

The application discloses a cement mortar thickening, flow increasing and reinforcing additive and a preparation method and application thereof, and belongs to the technical field of functional additives of cement-based materials. Microcrystalline cellulose is modified into sulfonated carboxyl microcrystalline cellulose through oxidation and sulfonation, the controllability of morphological change of the sulfonated carboxyl microcrystalline cellulose is improved, the sulfonated carboxyl microcrystalline cellulose is sequentially changed from a crystal phase into a swelling body, a microcrystalline region and an amorphous region microgel state and an interwoven crosslinking hydrogel state under alkaline conditions, the cohesiveness, fluidity, formation of hydration products in a solidification process, strength and durability of cement mortar filled with high-content coal chemical industry solid waste are regulated, and problems existing in the preparation of the cement mortar filled with high-content coal chemical industry solid waste in a goaf are solved. The prepared high-content coal chemical industry solid waste cement mortar can be used not only as a filling material in a coal goaf, but also as a cement ground, a cement road, a cement product, a wall cement mortar coating and a proper building cement mortar material.

Description

Technical Field

[0001] This invention belongs to the technical field of functional additives for cement-based materials, specifically relating to a tackifier, flow enhancer, and reinforcing agent for cement mortar, its preparation method, and its application. Background Technology

[0002] With the ongoing global resource extraction, especially mineral extraction, the problem of goaf areas has gradually become a global technological challenge. Goaf areas not only lead to instability in the geological structure but can also cause serious damage to the surrounding environment. During coal mining, as coal is extracted, numerous cavities are formed underground. If these cavities are not properly filled, they may trigger ground subsidence, damaging farmland, roads, buildings, and houses.

[0003] Cement-based backfill materials are widely used for filling goaf areas due to their good fluidity and self-hardening properties. However, traditional cement-based backfill materials are costly and have significant negative environmental impacts. Therefore, finding a high-performance, low-cost, and environmentally friendly backfill material has become a current research hotspot. Meanwhile, the global development of the coal chemical industry has generated a large amount of solid waste. The treatment and disposal of this solid waste is equally challenging. Traditional landfill and stockpiling methods not only occupy large amounts of land but may also have long-term environmental and ecological impacts. Applying coal chemical solid waste to the preparation of cement-based backfill materials can not only solve the solid waste treatment problem but also reduce the cost of backfill materials, achieving multiple benefits. Using coal chemical solid waste to prepare cement-based backfill materials for goaf areas has advantages in terms of location, quantity, and price. Only cement-based backfill materials with a solid waste content greater than 50% have practical application prospects, but they suffer from problems such as poor adhesion between components, easy water seepage, stratification and settling, low strength of the backfill, shrinkage and voiding, and poor durability. These problems severely restrict the promotion and application of cement-based backfill materials with high solid waste content.

[0004] Therefore, there is an urgent need to conduct research in this area to solve the theoretical and technical problems encountered in preparing cement-based backfill materials for goaf areas with high solid waste content. This will improve the performance of the backfill materials, promote their widespread application in goaf backfilling, and ultimately achieve efficient resource utilization and sustainable environmental development. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a viscosity-enhancing and flow-increasing additive for cement mortar, its preparation method and application, so as to solve the technical problems of poor adhesion between components, easy bleeding, stratification and sedimentation, low strength, non-dense structure, voiding of filling body and poor durability of existing cement-based filling materials for coal goaf.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar, comprising the following steps:

[0008] 1) Add microcrystalline cellulose to deionized water, adjust the pH to 2-4, heat, then add hydrogen peroxide dropwise, continue the reaction at the temperature, then cool, filter, wash, and dry to obtain carboxyl microcrystalline cellulose.

[0009] 2) Add the carboxylated microcrystalline cellulose prepared in step 1) to ethyl acetate, then add 1,3-propanesulfonate lactone, heat, keep warm and stir to react, then cool, filter, wash and dry to obtain sulfonated carboxylated microcrystalline cellulose.

[0010] 3) Add the sulfonated carboxylated microcrystalline cellulose prepared in step 2) to deionized water, adjust the pH value to 8.0-9.0, heat, keep warm and stir to react until the sulfonated carboxylated microcrystalline cellulose is in a swollen and microgel state, and after cooling, obtain the cement mortar thickening and flow-enhancing additive.

[0011] Preferably, in step 1), the ratio of microcrystalline cellulose: deionized water: hydrogen peroxide by weight is (50-60): (100-120): (20-30);

[0012] When adjusting the pH value, use a 10% hydrochloric acid solution; the hydrogen peroxide solution has a 30% mass fraction.

[0013] The heating temperature is 80–90℃; the hydrogen peroxide is added dropwise over a period of 1–1.5 hours; and the reaction is maintained at this temperature for 3–5 hours.

[0014] The average particle size of microcrystalline cellulose is 100–180 μm, and the degree of polymerization is 110–370.

[0015] Preferably, in step 2), the ratio of carboxymethyl microcrystalline cellulose: ethyl acetate: 1,3-propanesulfonic acid lactone by weight is (50-60): (80-100): (10-15).

[0016] The heating temperature is 60-70℃; the reaction time with stirring and maintaining the temperature is 5-6 hours.

[0017] Preferably, in step 3), 75-90 parts of deionized water are added to every 50-60 parts by weight of sulfonated carboxylated microcrystalline cellulose;

[0018] When adjusting the pH value, use a 5% sodium hydroxide solution;

[0019] The heating temperature is 40–50℃; the stirring and holding time is 30–40 min.

[0020] The content of sulfonated carboxylated microcrystalline cellulose is controlled at 10%–15%.

[0021] The present invention also discloses a tackifier, flow enhancer, and reinforcing agent for cement mortar prepared by the above preparation method.

[0022] This invention also discloses the application of the above-mentioned cement mortar thickening and flow-enhancing additive in coal mining subsidence areas with high content of coal chemical solid waste. First, cement, ash, fine slag and natural sand are mixed evenly to obtain a solid material mixture; then, water-reducing agent, sulfonated carboxylic microcrystalline cellulose and water are mixed evenly and added to the solid material mixture and stirred evenly to obtain cement mortar for coal mining subsidence areas with coal chemical solid waste.

[0023] In the 50% coal chemical solid waste cement mortar from coal mining subsidence areas, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 450:100:800:450:2.25:9.0:216.

[0024] This invention also discloses the application of the above-mentioned tackifier, flow enhancer, and reinforcing agent for cement mortar in coal goaf areas with high content of coal chemical solid waste. In cement mortar for coal goaf areas with 60% coal chemical solid waste, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 420:120:960:300:1.89:32.4:177.6.

[0025] This invention also discloses the application of the above-mentioned cement mortar thickening and flow-enhancing additive in coal goaf areas with high content of coal chemical solid waste. In cement mortar in coal goaf areas with 70% coal chemical solid waste, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 390:140:1120:150:1.755:63.0:132.

[0026] This invention also discloses the application of the above-mentioned cement mortar thickening and flow-enhancing additive in coal mining subsidence areas with high content of coal chemical solid waste. In cement mortar from coal mining subsidence areas with 80% coal chemical solid waste, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 320:180:1260:40:1.755:129.6:30.4.

[0027] Preferably, the ash has a particle size of 5–12 μm and a specific surface area of ​​not less than 3300 m². 2 / kg, loss on ignition not greater than 3.2%, water requirement not greater than 91%, SiO2 content 55.3%, Al2O3 content 22.5%, CaO content 9.5%, Fe2O3 content 6.5%, MgO content 3.2%, Na2O content 1.3%;

[0028] The cement is PO42.5 grade Portland cement;

[0029] The water-reducing agent is a polycarboxylate-based water-reducing agent with a mass fraction of 40% and a water reduction rate of 33%.

[0030] The natural sand is river sand with a fineness modulus of 1.6–2.2 mm and a bulk density of 1450–1510 kg / m³. 3 ;

[0031] The fine slag has a particle size of 0.6–3.5 mm and a specific surface area of ​​not less than 2500 m². 2 / kg, loss on ignition not greater than 3.5%, water requirement not greater than 95%, SiO2 content 53.5%, Al2O3 content 21.5%, CaO content 11.6%, Fe2O3 content 5.7%, MgO content 3.5%, Na2O content 2.3%.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention discloses a method for preparing a viscosity-enhancing and flow-promoting additive for cement mortar. Microcrystalline cellulose is modified by oxidation and sulfonation to become sulfonated carboxyl microcrystalline cellulose, improving the controllability of its morphological changes. This allows for the coordinated development of the morphological changes of sulfonated carboxyl microcrystalline cellulose in cement paste, from swelling to microgel clusters, and finally to a network of interwoven microcrystalline and amorphous regions, in accordance with the flow, setting, and solidification processes of the cement paste. Ultimately, this achieves a key technology for controlling the structure and properties of cement-based filling materials by utilizing the morphological changes of sulfonated carboxyl microcrystalline cellulose. The key technology of this research lies in the coordinated morphological changes of sulfonated carboxyl microcrystalline cellulose and its complementary and enhanced functional properties with the cement-based filling materials. By regulating the flow dynamics, sulfonated carboxylated microcrystalline cellulose is made to exist in the following states in cement-based materials: swollen, microgel clusters, and a network of interwoven microcrystalline and amorphous regions during solidification. This process demonstrates its thickening, flow-promoting, nucleation effect, and ability to promote the formation of intercalated composite network structures, thereby improving structural stability, strength, and durability. By utilizing the morphological changes of sulfonated carboxylated microcrystalline cellulose under alkaline conditions to improve the cohesion, structure, and properties of cement-based backfill materials, this study solves the key technical problem of coordinating the morphological changes of sulfonated carboxylated microcrystalline cellulose with those of cement-based backfill materials and achieving complementary functional improvements. The resulting cement mortar thickener and flow enhancer improves the cohesiveness, fluidity, dispersibility, strength, volume stability, and durability of cement mortar used for backfilling coal goaf areas containing high-content coal chemical solid waste. It addresses existing problems such as water seepage, stratification and sedimentation, low strength, non-dense structure, voids in the backfill, and poor durability, providing theoretical and technical support for the preparation of high-content, high-performance cement-based backfill materials for coal chemical solid waste and coal goaf areas.

[0034] This invention also discloses a tackifier and flow enhancer for cement mortar prepared by the above method. The introduction of carboxyl and sulfonated groups improves the interaction between the enhancer and the cement matrix, thereby strengthening the overall bonding performance. This tackifying effect helps to improve the cohesion and adhesion of cement mortar, making its bonding on various substrates more robust.

[0035] This invention also discloses the application of the aforementioned cement mortar thickening and flow-enhancing additive in coal mining subsidence areas with high content of coal chemical solid waste. "High content" refers to the content of coal chemical solid waste in cement-based filling materials ranging from 50% to 80%. High solid waste content reduces the cohesiveness of cement slurry and its ability to form hydration products. Based on previous research, this invention utilizes the structural morphological changes of sulfonated carboxyl microcrystalline cellulose to improve the cohesiveness of cement slurry and the ability to form cement hydration products. Sulfonated carboxyl microcrystalline cellulose exhibits a transformation process under alkaline conditions, progressing from a swollen body to a microgel state, a microcrystalline region, and an amorphous interwoven network hydrogel state. By combining the morphological changes of sulfonated carboxyl microcrystalline cellulose with the flow period, setting period, and solidification period of cement-based slurry, the morphology of sulfonated carboxyl microcrystalline cellulose can respectively improve the cohesiveness and flowability of cement slurry during the flow period, the formation of hydration products during the setting period, and the formation of a cross-linked network structure during the solidification period, thus eliminating existing problems. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the chemical reaction and chemical structure for preparing carboxylated microcrystalline cellulose according to the present invention;

[0037] Figure 2 A schematic diagram of the chemical reaction and chemical structure for the preparation of sulfonated carboxylated microcrystalline cellulose according to the present invention;

[0038] Figure 3 The microstructure of sulfonated carboxyl microcrystalline fibers prepared according to the present invention is shown in (a) at 1000x SEM magnification; (b) at 3000x SEM magnification; (c) at 8000x SEM magnification; and (d) at 10000x SEM magnification.

[0039] Figure 4 This is a schematic diagram illustrating the swelling and dispersion of sulfonated carboxylated microcrystalline cellulose to form a network structure, as presented in this invention.

[0040] Figure 5 This is a schematic diagram illustrating the structural enhancement effect of the sulfonated carboxyl microcrystalline cellulose gel in improving cohesion, increasing fluidity, and creating a network structure hydrogel according to the present invention; wherein, (a) shows the water absorption, viscosity enhancement, and flow-increasing principle of the sulfonated carboxyl microcrystalline cellulose gel clusters; (b) shows the interwoven network structure of the sulfonated carboxyl microcrystalline cellulose hydrogel with microcrystalline and amorphous regions.

[0041] Figure 6 This invention relates to the nucleation effect of microcrystalline regions on hydration products in the hydrogel formed by sulfonated carboxyl microcrystalline cellulose; wherein, (a) the carboxyl and sulfonic acid groups on the surface of the microcrystalline region attract cement particles and begin to form hydration products; (b) the hydration products continue to grow in the microcrystalline region and become templates; and (c) the templates promote the growth of hydration products and form interwoven cross-linked structures.

[0042] Figure 7 This is a SEM image showing the morphology and aggregation state of cement hydration products in the hydrogel formed by sulfonated carboxylic microcrystalline cellulose under the influence of the nucleation effect and template effect in the microcrystalline region. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings:

[0046] This invention discloses a method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar, comprising the following steps, where all parts are by weight:

[0047] Step 1: Preparation of carboxylated microcrystalline cellulose; Take 50-60 parts by weight of microcrystalline cellulose and add it to 100-120 parts by weight of deionized water. Adjust the pH to 2-4 with a 10% (w / w) dilute hydrochloric acid solution. Heat to 80-90℃, and begin adding 20-30 parts by weight of 30% hydrogen peroxide dropwise over 1-1.5 hours. Continue the reaction at this temperature for 3-5 hours. Then cool, filter, wash, and dry to obtain carboxylated microcrystalline cellulose. See [link to chemical reaction process] for details. Figure 1 .

[0048] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose; 50-60 parts of the carboxylated microcrystalline cellulose prepared in Step 1 were added to 80-100 parts of ethyl acetate, and 10-15 parts of 1,3-propanesulfonate lactone were added. The mixture was heated to 60-70℃ and stirred for 5-6 hours. Then, the mixture was cooled, filtered, washed, and dried to obtain sulfonated carboxylated microcrystalline cellulose. See [link to chemical reaction process] for details. Figure 2 .

[0049] Step 3: Preparation of the viscosity-enhancing and flow-promoting additive for cement mortar; namely, pretreatment of sulfonated carboxylated microcrystalline cellulose. Add 50-60 parts of the sulfonated carboxylated microcrystalline cellulose prepared in Step 2 to 75-90 parts of deionized water. Adjust the pH to 8.0-9.0 with a 5% sodium hydroxide solution. Heat to 40-50℃, stir and maintain the temperature for 30-40 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel. Control the sulfonated carboxylated microcrystalline cellulose content to 10%-15% to obtain the viscosity-enhancing and flow-promoting additive for cement mortar. Then cool and set aside for later use. See [link to sulfonated carboxylated microcrystalline cellulose morphological changes process] for details. Figure 3 See chemical reaction process. Figure 3 and Figure 4 .

[0050] In the above preparation method:

[0051] The average particle size of microcrystalline cellulose is 100–180 μm, and the degree of polymerization is 110–370.

[0052] This invention also discloses a tackifier and flow enhancer for cement mortar prepared by the above-described method. The introduction of carboxyl and sulfonated groups improves the interaction between the enhancer and the cement matrix, thereby strengthening the overall bonding performance. This tackifying effect helps to improve the cohesion and adhesion of cement mortar, making its bonding on various substrates more robust.

[0053] This invention also discloses the application of a viscosity-enhancing and flow-promoting additive for cement mortar in coal goaf areas with high content of coal chemical solid waste. The preparation method of cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes:

[0054] (1) The material composition of 50% coal chemical solid waste coal mining goaf cement mortar is as follows: cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylated microcrystalline cellulose: water, with a weight ratio of 450:100:800:450:2.25:9.0:216. During preparation, cement, ash, fine slag, and sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylated microcrystalline cellulose are mixed evenly and added to the cement-based material mixture, and stirred evenly. This mixture is used to prepare test samples and for curing. For the structural morphology changes and viscosity-increasing and flow-enhancing mechanism of sulfonated carboxylated microcrystalline cellulose, please refer to [reference needed]. Figure 5 , Figure 6 and Figure 7.

[0055] (2) The material composition of 60% coal chemical solid waste coal mining goaf cement mortar is as follows: cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylated microcrystalline cellulose: water, with a weight ratio of 420:120:960:300:1.89:32.4:177.6. During preparation, cement, ash, fine slag, and sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylated microcrystalline cellulose are mixed evenly and added to the cement-based material mixture, and stirred evenly. This mixture is used to prepare test samples and for curing. For the structural morphology changes and viscosity-increasing and flow-enhancing mechanism of sulfonated carboxylated microcrystalline cellulose, please refer to [reference needed]. Figure 5 , Figure 6 and Figure 7 .

[0056] (3) The material composition of 70% coal chemical solid waste coal mining goaf cement mortar is as follows: cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylated microcrystalline cellulose: water, with a weight ratio of 390:140:1120:150:1.755:63.0:132. During preparation, cement, ash, fine slag, and sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylated microcrystalline cellulose are mixed evenly and added to the cement-based material mixture, and stirred evenly. This mixture is used to prepare test samples and for curing. For the structural morphology changes and viscosity-increasing and flow-enhancing principles of sulfonated carboxylated microcrystalline cellulose, please refer to [link to relevant documentation]. Figure 5 , Figure 6 and Figure 7 .

[0057] (4) The material composition of cement mortar from 80% coal chemical solid waste coal mining subsidence area is as follows: cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylated microcrystalline cellulose: water, with a weight ratio of 320:180:1260:40:1.755:129.6:30.4. During preparation, cement, ash, fine slag, and sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylated microcrystalline cellulose are mixed evenly and added to the cement-based material mixture, and stirred evenly. This mixture is used to prepare test samples and for curing. For the structural morphology changes and viscosity-increasing and flow-enhancing principles of sulfonated carboxylated microcrystalline cellulose, please refer to [reference needed]. Figure 5 , Figure 6 and Figure 7 .

[0058] In the above application process:

[0059] The amount of material used should be increased or decreased according to the given range of variation.

[0060] Ash residue is a fine powdery solid waste similar to fly ash in coal chemical solid waste, with a particle size of 5-12 μm and a specific surface area of ​​not less than 3300 m². 2 / kg, loss on ignition not greater than 3.2%, water requirement not greater than 91%, SiO2 content 55.3%, Al2O3 content 22.5%, CaO content 9.5%, Fe2O3 content 6.5%, MgO content 3.2%, Na2O content 1.3%.

[0061] Fine slag is a granular solid waste from coal chemical industry, with a particle size similar to sand, ranging from 0.6 to 3.5 mm, and a specific surface area of ​​not less than 2500 m². 2 / kg, loss on ignition not greater than 3.5%, water requirement not greater than 95%, SiO2 content 53.5%, Al2O3 content 21.5%, CaO content 11.6%, Fe2O3 content 5.7%, MgO content 3.5%, Na2O content 2.3%.

[0062] The cement is PO42.5 grade silicate cement; the water-reducing agent is a polycarboxylate superplasticizer with a mass fraction of 40% and a water reduction rate of 33%.

[0063] The natural sand is river sand with a fineness modulus of 1.6–2.2 mm and a bulk density of 1450–1510 kg / m³. 3 .

[0064] See Figure 1 This is a schematic diagram of the chemical reaction and chemical structure for preparing carboxylated microcrystalline cellulose according to the present invention. As can be seen from the figure, microcrystalline cellulose is added to deionized water, the pH value is adjusted to 2-4, heated, and then hydrogen peroxide is added dropwise. The reaction is continued at a constant temperature, and then cooled, filtered, washed, and dried to obtain carboxylated microcrystalline cellulose.

[0065] See Figure 2 This is a schematic diagram of the chemical reaction and chemical structure for preparing sulfonated carboxylic microcrystalline cellulose according to the present invention. As can be seen from the figure, carboxylic microcrystalline cellulose is added to ethyl acetate, followed by the addition of 1,3-propanesulfonate lactone. The mixture is heated, kept warm and stirred, and then cooled, filtered, washed and dried to obtain sulfonated carboxylic microcrystalline cellulose.

[0066] See Figure 3 The microstructure of sulfonated carboxyl microcrystalline fibers prepared according to the present invention is shown in the figures. (a) is the SEM microstructure at 1000x magnification; (b) is the SEM microstructure at 3000x magnification; (c) is the SEM microstructure at 8000x magnification; and (d) is the SEM microstructure at 10000x magnification. As can be seen from the figures, the amorphous components in the sulfonated and carboxylated microcrystalline cellulose are well dispersed.

[0067] See Figure 4This diagram illustrates the swelling and dispersion of sulfonated carboxylated microcrystalline cellulose to form a network structure, as shown in the figure. It can be seen that during the dispersion process of sulfonated carboxylated microcrystalline cellulose, the amorphous regions swell and disperse, forming an interwoven structure with the crystalline regions. SCMCC is the abbreviation for sulfonated carboxylated microcrystalline cellulose. The cellulose molecular chain composed of glucose rings refers to the molecular chain composed of six-membered rings in the microcrystalline cellulose molecule, which is a structure inherent in cellulose itself.

[0068] See Figure 5 This is a schematic diagram illustrating the structural enhancement effect of sulfonated carboxyl microcrystalline cellulose gel in improving cohesion, increasing fluidity, and forming a network structure hydrogel according to the present invention. (a) shows the water absorption, viscosity increase, and flow-promoting principle of the sulfonated carboxyl microcrystalline cellulose gel clusters; (b) shows the interwoven hydrogel network structure of the microcrystalline and amorphous regions of sulfonated carboxyl microcrystalline cellulose. As can be seen from the diagram, sulfonated carboxyl microcrystalline cellulose, in a swollen and microgel state, absorbs water in cement mortar, increasing the cohesion between components and forming a ball-bearing effect with the mortar, thus exhibiting a flow-promoting effect. The sulfonated carboxyl cellulose forms an interwoven hydrogel state with the interwoven microcrystalline and amorphous regions, creating an interwoven gel structure with the cement mortar.

[0069] See Figure 6 This invention illustrates the nucleation effect of microcrystalline regions on hydration products in the hydrogel formed by sulfonated carboxyl microcrystalline cellulose. (a) shows that carboxyl and sulfonic acid groups on the surface of the microcrystalline regions attract cement particles and begin to form hydration products; (b) shows that the hydration products continue to grow in the microcrystalline regions and become templates; (c) shows that the templates promote the growth of hydration products and form an interwoven cross-linked structure. As can be seen from the figures, the mechanism by which sulfonated carboxyl microcrystalline cellulose regulates the structural morphology of cement hydration products is demonstrated. The hydrogel formed by sulfonated carboxyl microcrystalline cellulose also contains many smaller microcrystalline regions. The promoting effect of cement hydration products on the formation of hydration product crystals is also known as the nucleation effect. The carboxyl and sulfonic acid groups on the surface of the microcrystalline region attract cement particles and promote the formation of cement hydration products. The hydration products grow on the microcrystalline region of sulfonated carboxyl microcrystalline cellulose. The regular shape of the microcrystalline region has an influence on the shape of the hydration products and becomes a template for the morphology of cement hydration products. Cement hydration products have a variety of different shapes, such as rod-shaped, needle-shaped, and polyhedral. The cement hydration products aggregated on the microcrystalline region grow and form a relatively dense interwoven and cross-linked structure.

[0070] See Figure 7 This is a SEM image of the morphology and aggregation state of cement hydration products in the hydrogel formed by sulfonated carboxylic microcrystalline cellulose under the effects of crystal nucleation and template effects in the microcrystalline region. As can be seen from the image, under the effects of crystal nucleation and template effects, the cement hydration products form an interwoven structure of clustered needle-like hydration products and polyhedral aggregates.

[0071] This invention provides a viscosity-enhancing and flow-promoting additive for cement mortar, its preparation method, and its application. Specifically, it includes a method for preparing the additive and a method for preparing cement mortar for filling coal goaf areas with high-content coal chemical solid waste. "High content" refers to the coal chemical solid waste content in the cement-based filling material being 50%–80%. The viscosity-enhancing and flow-promoting additive for cement mortar prepared by this invention improves the cohesiveness, fluidity, and dispersibility of the prepared goaf filling cement mortar during mixing, as well as the density and uniformity of the filling structure after filling, and enhances its strength, volume stability, and durability. It utilizes the structural morphological changes of sulfonated carboxyl microcrystalline cellulose to improve the cohesiveness of the cement paste and the ability to form cement hydration products. Sulfonated carboxylated microcrystalline cellulose exhibits a transformation process under alkaline conditions, evolving from a swollen body to microgel clusters, microcrystalline regions, and an amorphous interwoven network hydrogel state. By linking the morphological changes of sulfonated carboxylated microcrystalline cellulose with the flow, setting, and curing stages of cement slurry, the morphology of sulfonated carboxylated microcrystalline cellulose can be used to improve the cohesiveness and fluidity of cement slurry during the flow stage, the formation of hydration products during the setting stage, and the formation of a cross-linked network structure during the curing stage, thereby eliminating existing problems.

[0072] Example 1

[0073] A method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar includes the following steps:

[0074] Step 1: Preparation of Carboxylated Microcrystalline Cellulose

[0075] By weight, 50 parts of microcrystalline cellulose were added to 100 parts of deionized water. The pH of the aqueous solution was adjusted to 2 with 10% hydrochloric acid. The solution was then heated to 80°C, and 20 parts of 30% hydrogen peroxide were added dropwise over 1 hour. The reaction was continued for 3 hours, and then the solution was cooled, filtered, washed, and dried to obtain carboxyl microcrystalline cellulose.

[0076] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose

[0077] Add 50 parts of the carboxylated microcrystalline cellulose prepared in step one to 80 parts of ethyl acetate, add 10 parts of 1,3-propanesulfonate lactone, heat to 60°C, keep warm and stir for 5 hours, then cool down, filter, wash and dry to obtain sulfonated carboxylated microcrystalline cellulose.

[0078] Step 3: Preparation of viscosity-enhancing and flow-promoting additives for cement mortar

[0079] Add 50 parts of the sulfonated carboxylated microcrystalline cellulose prepared in step 2 to 75 parts of deionized water, adjust the pH to 8.0 with a 5% sodium hydroxide solution, heat to 40°C, stir and keep warm for 30 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel state, control the sulfonated carboxylated microcrystalline cellulose content to 10%, and obtain a cement mortar thickening and flow-enhancing additive, and then cool it down for later use.

[0080] A method for preparing cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes the following methods:

[0081] (1) Preparation method of cement mortar containing 50% coal chemical solid waste from coal mining goaf: The material composition is cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water in a weight ratio of 450:100:800:450:2.25:9.0:216. During preparation, cement, ash, fine slag, and natural sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylic microcrystalline cellulose are mixed evenly and added to the cement-based material mixture and stirred evenly to obtain 50% coal chemical solid waste from coal mining goaf cement mortar, which is used to prepare test samples and for curing.

[0082] (2) Preparation method of cement mortar containing 60% coal chemical solid waste from coal mining goaf: The material composition is cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water in a weight ratio of 420:120:960:300:1.89:32.4:177.6. During preparation, cement, ash, fine slag, and natural sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylic microcrystalline cellulose are mixed evenly and added to the cement-based material mixture and stirred evenly to obtain 60% coal chemical solid waste from coal mining goaf cement mortar, which is used to prepare test samples and for curing.

[0083] (3) Preparation method of cement mortar containing 70% coal chemical solid waste from coal mining goaf: The material composition is cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water in a weight ratio of 390:140:1120:150:1.755:63.0:132. During preparation, cement, ash, fine slag, and natural sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylic microcrystalline cellulose are mixed evenly and added to the cement-based material mixture and stirred evenly to obtain 70% coal chemical solid waste from coal mining goaf cement mortar, which is used to prepare test samples and for curing.

[0084] (4) Preparation method of cement mortar containing 80% coal chemical solid waste from coal mining goaf: The material composition is cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water in a weight ratio of 320:180:1260:40:1.755:129.6:30.4. During preparation, cement, ash, fine slag, and natural sand are first mixed evenly in a mixer. Then, water, water-reducing agent, and sulfonated carboxylic microcrystalline cellulose are mixed evenly and added to the cement-based material mixture and stirred evenly to obtain 80% coal chemical solid waste from coal mining goaf cement mortar, which is used to prepare test samples and for curing.

[0085] The ash has a particle size of 5–12 μm and a specific surface area of ​​not less than 3300 m². 2 / kg, loss on ignition not greater than 3.2%, water requirement not greater than 91%, SiO2 content 55.3%, Al2O3 content 22.5%, CaO content 9.5%, Fe2O3 content 6.5%, MgO content 3.2%, Na2O content 1.3%;

[0086] The cement is PO42.5 grade Portland cement;

[0087] The water-reducing agent is a polycarboxylate-based water-reducing agent with a mass fraction of 40% and a water reduction rate of 33%.

[0088] The natural sand is river sand with a fineness modulus of 1.6–2.2 mm and a bulk density of 1450–1510 kg / m³. 3 ;

[0089] The fine slag has a particle size of 0.6–3.5 mm and a specific surface area of ​​not less than 2500 m². 2 / kg, loss on ignition not greater than 3.5%, water requirement not greater than 95%, SiO2 content 53.5%, Al2O3 content 21.5%, CaO content 11.6%, Fe2O3 content 5.7%, MgO content 3.5%, Na2O content 2.3%.

[0090] Example 2

[0091] A method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar includes the following steps:

[0092] Step 1: Preparation of Carboxylated Microcrystalline Cellulose

[0093] By weight, 53 parts of microcrystalline cellulose were added to 108 parts of deionized water. The pH of the aqueous solution was adjusted to 3 with 10% hydrochloric acid. The solution was then heated to 85°C, and 24 parts of 30% hydrogen peroxide were added dropwise over 1.5 hours. The reaction was continued for 4 hours, followed by cooling, filtration, washing, and drying to obtain carboxylated microcrystalline cellulose.

[0094] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose

[0095] Add 53 parts of the carboxylated microcrystalline cellulose prepared in step one to 86 parts of ethyl acetate, add 12 parts of 1,3-propanesulfonate lactone, heat to 65°C, keep warm and stir for 5.5 hours, then cool down, filter, wash and dry to obtain sulfonated carboxylated microcrystalline cellulose.

[0096] Step 3: Preparation of viscosity-enhancing and flow-promoting additives for cement mortar

[0097] Add 53 parts of the sulfonated carboxylated microcrystalline cellulose prepared in step 2 to 82 parts of deionized water, adjust the pH to 9.0 with a 5% sodium hydroxide solution, heat to 45°C, stir and keep warm for 35 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel state, control the sulfonated carboxylated microcrystalline cellulose content to 12%, and obtain a cement mortar thickening and flow-enhancing additive, and then cool it down for later use.

[0098] A method for preparing cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes the following methods:

[0099] The preparation methods for cement mortar containing 50%, 60%, 70%, and 80% coal chemical solid waste from coal mining subsidence areas are the same as in Example 1.

[0100] Example 3

[0101] A method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar includes the following steps:

[0102] Step 1: Preparation of Carboxylated Microcrystalline Cellulose

[0103] By weight, 57 parts of microcrystalline cellulose were added to 115 parts of deionized water. The pH of the aqueous solution was adjusted to 4 with 10% hydrochloric acid. The solution was then heated to 90°C, and 26 parts of 30% hydrogen peroxide were added dropwise over 1.2 hours. The reaction was continued for 5 hours, followed by cooling, filtration, washing, and drying to obtain carboxylated microcrystalline cellulose.

[0104] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose

[0105] 56 parts of the carboxylated microcrystalline cellulose prepared in step one were added to 93 parts of ethyl acetate, and 13 parts of 1,3-propanesulfonate lactone were added. The mixture was heated to 70°C and stirred for 6 hours. Then the mixture was cooled, filtered, washed, and dried to obtain sulfonated carboxylated microcrystalline cellulose.

[0106] Step 3: Preparation of viscosity-enhancing and flow-promoting additives for cement mortar

[0107] Add 57 parts of the sulfonated carboxylated microcrystalline cellulose prepared in step 2 to 85 parts of deionized water, adjust the pH to 8.5 with a 5% sodium hydroxide solution, heat to 50°C, stir and keep warm for 40 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel state, control the sulfonated carboxylated microcrystalline cellulose content to 13%, and obtain a cement mortar thickening and flow-enhancing additive, and then cool it down for later use.

[0108] A method for preparing cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes the following methods:

[0109] The preparation methods for cement mortar containing 50%, 60%, 70%, and 80% coal chemical solid waste from coal mining subsidence areas are the same as in Example 1.

[0110] Example test results

[0111] Table 1. Performance of high-content coal chemical solid waste and coal goaf cement mortar in Examples 1-3

[0112]

[0113] *: Freeze-thaw resistance: The results of the mass and compressive strength of the sample before and after 50 freeze-thaw cycles at 28 days, with freeze-thaw temperatures of -18±2℃ and 5±2℃, freezing for 2 hours and thawing for 2 hours.

[0114] Table 1 shows the performance of cement mortar from coal mining subsidence areas with high content of coal chemical solid waste in Examples 1-3. As can be seen from the table, the initial and 90-minute flowability values ​​indicate that sulfonated carboxyl microcrystalline cellulose improves the flowability of cement mortar; the bleeding rate at the initial and 90-minute times indicates that the cohesion between components is improved; and the compressive strength and freeze-thaw resistance at 28 days indicate that the strength and durability are improved.

[0115] Example 4

[0116] A method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar includes the following steps:

[0117] Step 1: Preparation of Carboxylated Microcrystalline Cellulose

[0118] By weight, 58 parts of microcrystalline cellulose were added to 117 parts of deionized water. The pH of the aqueous solution was adjusted to 2 with 10% hydrochloric acid. The solution was then heated to 80°C, and 28 parts of 30% hydrogen peroxide were added dropwise over 1 hour. The reaction was continued for 3.5 hours, then cooled, filtered, washed, and dried to obtain carboxyl microcrystalline cellulose.

[0119] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose

[0120] 57 parts of the carboxylated microcrystalline cellulose prepared in step one were added to 96 parts of ethyl acetate, and 14 parts of 1,3-propanesulfonate lactone were added. The mixture was heated to 60°C and stirred for 5 hours. Then the mixture was cooled, filtered, washed, and dried to obtain sulfonated carboxylated microcrystalline cellulose.

[0121] Step 3: Preparation of viscosity-enhancing and flow-promoting additives for cement mortar

[0122] Add 55 parts of the sulfonated carboxylated microcrystalline cellulose prepared in step 2 to 85 parts of deionized water, adjust the pH to 8.0 with a 5% sodium hydroxide solution, heat to 40°C, stir and keep warm for 30 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel state, control the sulfonated carboxylated microcrystalline cellulose content to 14%, and obtain a cement mortar thickening and flow-enhancing additive, and then cool it down for later use.

[0123] A method for preparing cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes the following methods:

[0124] The preparation methods for cement mortar containing 50%, 60%, 70%, and 80% coal chemical solid waste from coal mining subsidence areas are the same as in Example 1.

[0125] Example 5

[0126] A method for preparing a viscosity-enhancing, flow-promoting, and reinforcing additive for cement mortar includes the following steps:

[0127] Step 1: Preparation of Carboxylated Microcrystalline Cellulose

[0128] By weight, 60 parts of microcrystalline cellulose were added to 120 parts of deionized water. The pH of the aqueous solution was adjusted to 4 with 10% hydrochloric acid. The solution was then heated to 90°C, and 30 parts of 30% hydrogen peroxide were added dropwise over 1.5 hours. The reaction was continued at this temperature for 4.5 hours. The solution was then cooled, filtered, washed, and dried to obtain carboxylated microcrystalline cellulose.

[0129] Step 2: Preparation of sulfonated carboxylated microcrystalline cellulose

[0130] Add 60 parts of the carboxylated microcrystalline cellulose prepared in step one to 100 parts of ethyl acetate, add 15 parts of 1,3-propanesulfonate lactone, heat to 70°C, keep warm and stir for 6 hours, then cool down, filter, wash and dry to obtain sulfonated carboxylated microcrystalline cellulose.

[0131] Step 3: Preparation of viscosity-enhancing and flow-promoting additives for cement mortar

[0132] Add 60 parts of the sulfonated carboxylated microcrystalline cellulose prepared in step two to 90 parts of deionized water, adjust the pH to 9.0 with a 5% sodium hydroxide solution, heat to 50°C, stir and keep warm for 40 minutes to allow the sulfonated carboxylated microcrystalline cellulose to swell and microgel state, control the sulfonated carboxylated microcrystalline cellulose content to 15%, and obtain a cement mortar thickening and flow-enhancing additive, and then cool it down for later use.

[0133] A method for preparing cement mortar for filling coal goaf areas with high content of coal chemical solid waste includes the following methods:

[0134] The preparation methods for cement mortar containing 50%, 60%, 70%, and 80% coal chemical solid waste from coal mining subsidence areas are the same as in Example 1.

[0135] This invention utilizes the structural morphological changes of sulfonated carboxyl microcrystalline cellulose under alkaline conditions, which sequentially transform from a crystalline phase to a swollen body, a microcrystalline region, an amorphous region, and an interwoven cross-linked hydrogel state. This allows for the regulation of the workability, flow dynamics, solidification state, curing process, and hydration product formation of cement mortar for filling high-content coal chemical solid waste, thus solving the problems existing in the preparation of cement mortar for filling coal goaf areas using high-content coal chemical solid waste. The high-content coal chemical solid waste cement mortar prepared by this invention can not only be used as a filling material for coal goaf areas, but also as a cement floor tile, cement road, cement product, wall cement mortar coating, and appropriate building cement mortar material.

[0136] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a tackifier, flow enhancer, and reinforcing agent for cement mortar, characterized in that, Includes the following steps: 1) Add microcrystalline cellulose to deionized water, adjust the pH to 2-4, heat, then add hydrogen peroxide dropwise, continue the reaction at the temperature, then cool, filter, wash, and dry to obtain carboxyl microcrystalline cellulose; 2) Add the carboxylated microcrystalline cellulose prepared in step 1) to ethyl acetate, then add 1,3-propanesulfonate lactone, heat, keep warm and stir to react, then cool, filter, wash and dry to obtain sulfonated carboxylated microcrystalline cellulose. 3) Add the sulfonated carboxylated microcrystalline cellulose prepared in step 2) to deionized water, adjust the pH value to 8.0~9.0, heat, keep warm and stir to react until the sulfonated carboxylated microcrystalline cellulose is in a swollen and microgel state, and after cooling, obtain the cement mortar thickening and flow-enhancing additive.

2. The preparation method of the cement mortar thickening and flow-enhancing additive according to claim 1, characterized in that, In step 1), the ratio of microcrystalline cellulose: deionized water: hydrogen peroxide by weight is (50~60):(100~120):(20~30). When adjusting the pH value, a 10% (w / w) dilute hydrochloric acid solution is used; the hydrogen peroxide has a (w / w) fraction of 30%. The heating temperature is 80~90℃; the hydrogen peroxide is added dropwise over a period of 1~1.5 hours; and the heat preservation reaction time is 3~5 hours. The microcrystalline cellulose has an average particle size of 100-180 μm and a degree of polymerization of 110-370.

3. The preparation method of the cement mortar thickening and flow-enhancing additive according to claim 1, characterized in that, In step 2), the ratio of carboxylated microcrystalline cellulose: ethyl acetate: 1,3-propanesulfonic acid lactone by weight is (50~60):(80~100):(10~15). The heating temperature is 60~70℃; the heat preservation and stirring reaction time is 5~6h.

4. The preparation method of the cement mortar thickening and flow-enhancing additive according to claim 1, characterized in that, In step 3), 75-90 parts of deionized water are added to every 50-60 parts by weight of sulfonated carboxylated microcrystalline cellulose; When adjusting the pH value, use a 5% sodium hydroxide solution; The heating temperature is 40~50℃; the heat preservation and stirring reaction time is 30~40min; The content of sulfonated carboxylated microcrystalline cellulose is controlled at 10%~15%.

5. The cement mortar thickening and flow-enhancing additive prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the cement mortar thickening, flow-enhancing, and reinforcing additive according to claim 5 in coal mining subsidence areas with high content of coal chemical solid waste, characterized in that... First, mix cement, ash, fine slag and natural sand evenly to obtain a solid material mixture; then mix water-reducing agent, sulfonated carboxylic microcrystalline cellulose and water evenly, add to the solid material mixture and mix evenly to obtain coal chemical solid waste coal mining goaf cement mortar. Among them, in 50% of the coal chemical solid waste and coal mining goaf cement mortar, the weight ratio of cement: ash: fine slag: natural sand: water reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 450:100:800:450:2.25:9.0:

216. The ash has a particle size of 5~12μm and a specific surface area of ​​not less than 3300m². 2 / kg, loss on ignition not greater than 3.2%, water requirement not greater than 91%, SiO2 content 55.3%, Al2O3 content 22.5%, CaO content 9.5%, Fe2O3 content 6.5%, MgO content 3.2%, Na2O content 1.3%; The fine slag has a particle size of 0.6~3.5mm and a specific surface area of ​​not less than 2500m². 2 / kg, loss on ignition not greater than 3.5%, water requirement not greater than 95%, SiO2 content is 53.5%, Al2O3 content is 21.5%, CaO content is 11.6%, Fe2O3 content is 5.7%, MgO content is 3.5%, and Na2O content is 2.3%.

7. The application of the cement mortar thickening, flow-enhancing, and reinforcing additive according to claim 5 in coal mining subsidence areas with high content of coal chemical solid waste, characterized in that... In 60% of coal chemical solid waste and coal mining subsidence area cement mortar, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 420:120:960:300:1.89:32.4:177.

6.

8. The application of the cement mortar thickening, flow-enhancing, and reinforcing additive of claim 5 in coal mining subsidence areas with high content of coal chemical solid waste, characterized in that... In 70% of coal chemical solid waste and coal mining subsidence area cement mortar, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 390:140:1120:150:1.755:63.0:

132.

9. The application of the cement mortar thickening, flow-enhancing, and reinforcing additive according to claim 5 in coal mining subsidence areas with high content of coal chemical solid waste, characterized in that... In 80% of coal chemical solid waste and coal mining goaf cement mortar, the weight ratio of cement: ash: fine slag: natural sand: water-reducing agent: sulfonated carboxylic microcrystalline cellulose: water is 320:180:1260:40:1.755:129.6:30.

4.

10. The application of the cement mortar thickening, flow-enhancing, and reinforcing additive according to any one of claims 6 to 9 in coal mining subsidence areas with high content of coal chemical solid waste, characterized in that... The ash has a particle size of 5~12μm and a specific surface area of ​​not less than 3300m². 2 / kg, loss on ignition not greater than 3.2%, water requirement not greater than 91%, SiO2 content 55.3%, Al2O3 content 22.5%, CaO content 9.5%, Fe2O3 content 6.5%, MgO content 3.2%, Na2O content 1.3%; The cement is PO42.5 grade silicate cement; The water-reducing agent is a polycarboxylate-based water-reducing agent with a mass fraction of 40% and a water reduction rate of 33%. The natural sand is river sand with a fineness modulus of 1.6~2.2mm and a bulk density of 1450~1510kg / m³. 3 ; The fine slag has a particle size of 0.6~3.5mm and a specific surface area of ​​not less than 2500m². 2 / kg, loss on ignition not greater than 3.5%, water requirement not greater than 95%, SiO2 content is 53.5%, Al2O3 content is 21.5%, CaO content is 11.6%, Fe2O3 content is 5.7%, MgO content is 3.5%, and Na2O content is 2.3%.

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