A method for regulating the properties of cement mortar by adding attapulgite-based modifiers

Abstract

This invention discloses a method for regulating the performance of cement mortar by adding attapulgite-based modified materials. First, 90% water is mixed with cement, fly ash, and sand and stirred evenly. Then, a water-reducing agent and an air-entraining agent are added and stirred for 3 minutes. Finally, a suspension prepared by adding the attapulgite-based modified material and the remaining 10% water is added and stirred again for 3-5 minutes to obtain the cement mortar. The attapulgite-based modified material is obtained by removing sand, dissociating rod-crystal bundles, and modifying the raw ore with inorganic salts. The separated quartz sand can be reused as a mortar component. This invention successfully prepares cement mortar with excellent cohesiveness, thixotropy, and strength by adding highly dispersed nano-sized attapulgite-based modified materials, controlling the ratio of water-reducing agent to air-entraining agent, and optimizing the mix proportions. It shows promising application prospects in complex component manufacturing, functional material molding, and 3D printing.

Description

Technical Field

[0001] This invention relates to a method for preparing high-performance cement mortar, and more particularly to a method for regulating the performance of cement mortar by adding attapulgite-based modifiers, which belongs to the field of green and low-carbon building materials. Background Technology

[0002] As is well known, cement mortar possesses excellent mechanical and durability properties, and is widely used in construction, decoration, and 3D intelligent manufacturing. Classified by specific application scenarios, cement mortar includes masonry mortar, plastering mortar, floor mortar, waterproof mortar, interface mortar, tile adhesive, self-leveling mortar, and concrete repair mortar. With the rapid development of infrastructure projects in my country, engineering structures are becoming more complex and multi-dimensional. Construction equipment and machinery are also gradually developing towards specialization, automation, and integration, promoting continuous innovation in building materials towards green, low-carbon, and functional directions. In recent years, the consumption of cement mortar has steadily increased, and the requirements for its water retention, cohesiveness, thixotropy, strength, and durability are also rising. Furthermore, there is a strong market demand for cement mortar and its additives that offer easily controllable workability and convenient operation. Therefore, there is an urgent need to develop a green and efficient additive or modifier to improve / control the workability of cement mortar to meet the ever-changing market demands and future development trends in the construction industry.

[0003] In the construction industry, modifiers (such as hydroxyethyl cellulose ether and hydroxypropyl methyl cellulose ether) are often added to improve the cohesiveness and thixotropic properties of cementitious materials. Unlike chemical modifiers or additives, natural micro- and nano-structured clay minerals possess excellent surface, volume, size, and filling effects, making them a preferred choice for environmentally friendly functional materials and novel auxiliary reinforcement materials. Attapulgite, a hydrous magnesium-aluminate silicate clay mineral with a layered chain structure, is a natural one-dimensional nanostructured material. Its unique nanorod-shaped crystal morphology, pore structure, and charged properties give it excellent colloidal properties, adsorption properties, and reinforcement and toughening properties for polymer materials, making it widely used in various industrial fields such as petroleum, chemical, environmental protection, pharmaceutical, food, and energy. Research shows that green, environmentally friendly, and low-cost attapulgite can also improve the workability and compatibility of cementitious materials, such as reducing the heat of hydration during curing and improving the stability of cement paste. In recent years, the application of attapulgite in cementitious systems has gradually come into focus and has become one of the hottest research areas in the field of cementitious materials. Patents such as "A high-performance concrete composition suitable for spraying (CN114075059A)," "Attapulgite clay-based composite mortar admixture (CN1325422C)," "A waterproof and thermally insulating mortar and its preparation method (CN104163604A)," "A dry powder mortar and its admixture (CN104310837B)," "A composite penetrating crystallizing waterproofing agent (CN101348386B)," and "A special gypsum mortar for screeding and its preparation method (CN111484300B)" all involve this content. However, the above-mentioned technical solutions for improving mortar performance using attapulgite all include technical features such as fine grinding of attapulgite, high-temperature calcination of attapulgite, or high-proportion addition of attapulgite, and do not achieve truly efficient utilization of the unique structural characteristics and nano-effects of attapulgite itself. In fact, both grinding and high-temperature calcination severely damage the unique rod-like morphology, length, and pore structure of attapulgite. Furthermore, attapulgite is a non-renewable mineral resource that cannot be artificially synthesized to date. Adding it in high proportions contradicts its unique "MSG-like" additive approach and its high-value utilization concept; in fact, excessive addition can negatively impact other properties of the composite product. Therefore, this invention employs multiple strategies, including adding highly dispersed nano-sized attapulgite-based modifiers, controlling the ratio of water-reducing agents / air-entraining agents, and optimizing the mix proportions. It quantitatively analyzes the structure-property relationship between key factors such as the type and amount of attapulgite-based modifiers and the workability of cement mortar, successfully preparing cement mortar with controllable cohesiveness, thixotropy, shape retention, and strength. This mortar shows promising application prospects in fields such as ancient building and cultural relic protection and restoration, high-strength cement mortar, functional material molding, and 3D printing. Summary of the Invention

[0004] To address the shortcomings of using attapulgite to improve the workability of cement mortar, such as the severe damage to its unique physicochemical properties caused by grinding or calcination, and the reduction in mortar strength due to improper addition methods or excessive amounts, this invention provides a method for regulating cement mortar performance by adding attapulgite-based modifiers. This method is based on a deep understanding of the physicochemical properties of attapulgite, the rod-crystal bundle dissociation modification process, and the key factors affecting cement mortar workability. First, the efficiently and non-destructively dissociated nano-attapulgite is modified to obtain nano-sized attapulgite-based modifiers. Then, the workability of the cement mortar is rationally controlled by adjusting key parameters such as the amount of nano-sized attapulgite-based modifier added and the ratio of water-reducing agent / air-entraining agent.

[0005] The present invention discloses a method for regulating the performance of cement mortar by adding attapulgite-based modifiers. The cement mortar is composed of the following raw materials in parts by weight: 425-450 parts cement, 110-120 parts fly ash, 1200-1250 parts sand, 225-240 parts water, 6-8 parts water-reducing agent, 0.07-0.35 parts air-entraining agent, and 1.5-10 parts attapulgite-based modifiers. The attapulgite-based modifiers are obtained by sequentially acid-activating, desanding, rod-cluster dissociation, and inorganic salt modification of raw attapulgite ore. The quartz sand separated by desanding can be reused as a sand component in the mortar. The attapulgite content in the raw attapulgite ore is not less than 50%. The acid activation treatment of attapulgite involves dispersing the raw ore in an aqueous solution of sulfuric acid or phosphoric acid with a pH of 3.5–4.0 and stirring for 4–8 hours. Sand removal is achieved by passing the acid-activated attapulgite slurry through a hydrocyclone or high-speed spiral classifier. The dissociation of the rod-shaped crystal bundles is achieved through ultrasonic or high-pressure homogenization. Inorganic salt modification involves adding 0.25%–2.0% by weight of at least one of magnesium salts, ammonium salts, aluminum sulfates, phosphates, or alkylbenzene sulfonates of attapulgite and then stirring to modify the mixture.

[0006] The cement mortar mixing process is as follows: First, mix 90% water with cement, sand, and fly ash, and stir evenly. Then, add water-reducing agent and air-entraining agent, and stir for 3 minutes. Finally, add a suspension prepared from attapulgite-based material and 10% water, and stir again for 3-5 minutes to obtain cement mortar with added attapulgite-based modified material. The cement is any one or a mixture of silicate cement, white cement, and sulfoaluminate cement. The fly ash is grade F fly ash, and the sand is natural sand or manufactured sand with a fineness modulus of 2.6-3.0. The water-reducing agent is a retarding naphthalene-based water-reducing agent or a polycarboxylate-based water-reducing agent with a water reduction rate of 25-40%. The air-entraining agent is one of rosin-based, alkylbenzene sulfonate-based, triterpenoid saponin-based, or rosin thermal polymer-based air-entraining agents.

[0007] The acid activation of attapulgite in this invention can remove unstable carbonates, soluble salts, and other impurities from the raw ore. The significantly reduced conductivity of the acid-activated slurry confirms a decrease in the amount of soluble salts. Hydrocyclone or high-speed spiral classification can effectively separate associated quartz sand from the raw ore. As shown in Table 1, the sand content in the liberated attapulgite is 0.56%, only 1 / 10 of the sand content in the raw ore. This sand removal process not only significantly reduces the wear and damage to ultrasonic equipment or high-pressure homogenizers caused by quartz sand, facilitating continuous and batch-scale rod-cluster liberation, but also allows the separated quartz sand to be reused as a mortar component, further reducing mortar preparation costs and improving the comprehensive utilization rate of mineral resources. During ultrasonic or high-pressure homogenization, intense physical effects (such as cavitation) create tens of thousands of cavitation bubbles within the microspaces between the rod-shaped crystal bundles and individual crystals. These cavitation bubbles then undergo continuous and violent implosion, generating powerful microjets that, acting on the heterogeneous interface or within the microspaces, gently tear the rod-shaped crystal bundles and gradually dissociate them into individual nanorods. Moreover, this physical dissociation process does not damage the rod-shaped crystal structure, length, material structure, or chemical morphology of attapulgite. Figure 1 It can be seen that the dispersion of rod-shaped crystals is significantly improved after dissociation, the number of individual rod-shaped crystals increases, and the original rod-shaped crystal morphology is retained. From the particle size distribution and rod-shaped crystal length data in Table 1, it can be seen that the D50 of the dissociated attapulgite is only about 32% of that of the original ore, confirming that the attapulgite is dissociated from clusters into small-diameter rod-shaped crystal bundles or nano-rod-shaped crystals, with almost no change in rod-shaped crystal length, achieving efficient and non-destructive dissociation of the rod-shaped crystal bundles. XRD, infrared, and XRF results also confirm that the phase composition, main functional groups, and chemical composition of attapulgite did not change significantly before and after dissociation. Simultaneously, dissociation also effectively improves the specific surface area of ​​attapulgite, the suspension stability of the slurry, and the viscosity; the specific surface area increases from the original 185.64 m². 2 / g increased to 218.65m 2 / g, which improves the hydrophilicity and reaction contact area of ​​attapulgite, and the Zeta potential of the dissociated attapulgite surface is -26.17mv, which is much higher than the Zeta potential of cement, fly ash and sand (-2.55mv, -15.96mv and -17.42mv, respectively). The increased repulsive force between the highly dispersed and negatively charged nanorod crystals leads to an increase in the thickness of the double electric layer formed in the solution, which is manifested as an increase in the suspension stability and rotational viscosity of the slurry. This is conducive to the formation of a stable and dense three-dimensional network structure, thereby improving the thixotropy and structural stability of the cement slurry.

[0008]

[0009] The inorganic salt modification process of attapulgite involves adding 0.25%–2.0% by mass of dissociated attapulgite from at least one of magnesium salts, ammonium salts, aluminum sulfate salts, phosphates, or alkylbenzene sulfonates. Inorganic salt modification of the highly dispersed nano-attapulgite significantly improves the modification reaction rate and efficiency, resulting in attapulgite-based modified materials with good thixotropic properties. In a static state, the nanocrystals and crystal bundles intertwine and interweave to form flocculated aggregates, binding a large number of water molecules within the network structure, which is conducive to forming a gel with low flowability and high load-bearing capacity. Repeated shearing or agitation disrupts the three-dimensional network structure, releasing water molecules and improving the flowability of the composite. The rheological properties of cement paste were tested using a rheometer (Anton-Paar MCR102). The ratio of initial stress to equilibrium stress was defined as the thixotropic index, which quantitatively describes the relationship between static and dynamic yield stresses. A higher thixotropic index indicates that the composite cement paste material is more prone to static thickening and shear thinning, indicating better thixotropy. Attapulgite-based modifiers with mass fractions of 0%, 0.5%, and 1.0% were rapidly dispersed in the cement paste, and the change in thixotropic index was used to characterize the effect of the additives on the thixotropy of the cement paste material. As... Figure 2 As shown, the thixotropic index of cement paste is 1.91. However, the addition of attapulgite-based modifier significantly improves the thixotropic index of composite cement paste. Adding only 1% of attapulgite-based modifier can increase the thixotropic index by 37%. This confirms that the reasonable addition of attapulgite-based modifier can yield cement-based mixed cementitious materials with low dynamic yield stress, high static yield stress, and thixotropic properties. This has good application prospects in fields such as 3D printing, cultural relic protection and restoration, and the molding of complex components.

[0010] This invention quantitatively studies and compares the factors affecting the cohesiveness, fluidity, and strength of cement mortar by adjusting key parameters such as the amount of attapulgite-based material added and the mix ratio. It summarizes the structure-property relationship between the above-mentioned key preparation parameters and the workability of cement mortar, obtains the range of preparation process parameters for cement mortar with good workability, and reasonably adjusts the workability of cement mortar according to specific construction projects, requirements, conditions, and environments to maximize the satisfaction of high-standard, special, or complex construction scenarios.

[0011] In practical applications, slump and strength are important indicators for evaluating the quality of cement mortar. The slump value of cement mortar directly reflects its self-compacting ability, deformation capacity, and shape retention under gravity. High-strength cement mortar not only ensures the quality of construction projects but also provides strong protection for building safety. The changes in slump spread or slump over time of cement mortar after adding attapulgite-based modifiers are shown in the figure. Figure 3It can be seen that the slump expansion of cement mortar after 3 hours of mixing is 187 mm, still exhibiting good fluidity, before rapidly agglomerating. After 4 hours, the slump is 67 mm. With the addition of 0.25% and 0.5% attapulgite-based modifiers, the slump expansions after 2 hours are 190 mm and 160 mm, respectively, and after 3 hours are 50 mm and 40 mm, respectively, demonstrating good cohesiveness and shape retention. With the addition of 1% attapulgite-based modifiers, the slump after 2 hours and 3 hours are 98 mm and 20 mm, respectively. The trend of mortar slump expansion over time shows that the freshly mixed mortar agglomerates, the fluidity of the mortar increases after shearing, and it agglomerates again in the later stage, demonstrating the advantages of controlling thixotropy and inhibiting rapid curing. When the addition amount is increased to 2%, the mortar accumulation shape after mixing is an ideal frustum shape with a height approximately equal to the slump cylinder, and the outer surface of the accumulated mortar is smooth and dense, exhibiting excellent cohesiveness and self-compacting ability. The compressive and flexural strengths of the cement mortar test blocks were further tested after curing for 28 days. Figure 4 It can be seen that adding attapulgite-based modifiers can improve the mechanical strength of cement mortar, especially when the addition amount is 1-2%. This is mainly related to the small-size filling effect of micro / nano materials and the chemical composition of attapulgite. From the particle size distribution, it can be seen that the D of cement particles... 50 and D 90 The D values ​​of fly ash are 21.63 and 71.50 μm. 50 and D 90 The thicknesses are 24.05 and 157.33 μm, while the D of the attapulgite-based modified material is... 50 and D 90 With particle sizes of only 9.18 and 20.77 μm, highly dispersible and small-particle-size attapulgite-based modified materials are uniformly mixed with two main cementing materials. The micro-nano structured mineral materials efficiently and rapidly fill the gaps between the cementing materials and sand, facilitating the formation of a stable and dense structure. Furthermore, the attapulgite-based material, rich in active silicon, aluminum, magnesium, and calcium, promotes the gelation reaction of the cement slurry. The uniformly dispersed nanorod-shaped crystal structure contributes to toughening and reinforcing properties. Therefore, based on specific applications and usage scenarios, fully utilizing the nanostructured, highly dispersed, and thixotropic attapulgite-based materials to rationally control the cohesiveness, thixotropy, and strength of cement mortar is of guiding significance for expanding the application fields of cement mortar and improving its performance.

[0012] In summary, the present invention has the following advantages compared with the prior art:

[0013] 1. This invention obtains nanostructured, highly dispersible, and thixotropic attapulgite-based modified materials through non-destructive dissociation of rod crystal bundles and inorganic salt modification processes. The attapulgite-based modified material slurry is further added to cement mortar with optimized mix proportions, and then mixed in stages to obtain cement mortar with high cohesiveness, thixotropy, and high strength. This mortar can meet the specific working performance requirements of mortar used in the construction of complex structures, the molding of functional materials, and 3D printing. It has promising application prospects in the fields of ancient building and cultural relic protection and restoration, high-strength cement mortar, and additive manufacturing.

[0014] 2. This invention, based on specific application scenarios and construction requirements, organically combines techniques such as adding nanostructured attapulgite-based modified materials, adjusting the water-cement ratio, and controlling the proportion of water-reducing agents / air-entraining agents to rationally control the workability of cement mortar, including its cohesiveness, thixotropy, and shape retention. It fully utilizes the filling effect and gelling reactivity of nano-attapulgite rod crystals to simultaneously improve the compressive and flexural strength of the cement mortar. Only minor adjustments are made to conventional cement mortar mixing, curing, and construction processes to obtain functional cement mortar with adjustable fluidity, cohesiveness, and strength.

[0015] 3. This invention utilizes hydrophilic magnesium-aluminate silicate clay minerals (attapulgite-based materials) to regulate the performance of cement mortar. After the attapulgite-based materials are mixed with the cement mortar components, there will be no quality deterioration such as poor workability or bleeding. Furthermore, the introduction of attapulgite-based materials can effectively inhibit the segregation or over-curing of cement mortar. After repeated shearing or vibration, the cement mortar still has fluidity and self-compacting ability. In specific situations, it can also reduce the amount of cement used or the loss of formwork, which is convenient for on-site construction and practical application. It has little environmental pollution and ecological damage, and has good economic and social benefits. Attached Figure Description

[0016] Figure 1 SEM images of raw attapulgite ore (left) and dissociated attapulgite (right).

[0017] Figure 2 The thixotropic index of cement slurry after adding attapulgite-based materials is given, where APT-1, 2, 3, and 4 are respectively Mingguang dissociated attapulgite, Xuyi dissociated attapulgite, Mingguang dissociated & modified attapulgite, and Xuyi dissociated & modified attapulgite.

[0018] Figure 3 This describes the change in slump spread or slump over time of cement mortar after the addition of attapulgite-based modifiers.

[0019] Figure 4 The compressive and flexural strengths of cement mortar with added attapulgite-based modifiers were measured after 28 days of curing. Detailed Implementation

[0020] The preparation process of the attapulgite-based modified material in this invention and the method of using the attapulgite-based modified material to regulate the performance of cement mortar are further explained below through specific embodiments. The slump and mortar block strength were tested according to the methods and experimental conditions in the Chinese Cement Mortar Standard (GB / T17671-2021).

[0021] Example 1

[0022] (1) Preparation of attapulgite-based modified materials: First, the raw attapulgite ore from Xuyi (wherein, the attapulgite content is >50% and the quartz sand mass fraction is about 30%) is crushed to 100 mesh and then dispersed in a sulfuric acid aqueous solution with a solid-liquid ratio of 1:10 and stirred for 4 hours to obtain activated attapulgite slurry. Then, after three-stage hydrocyclone treatment, a desanded attapulgite slurry is obtained. Then, after ultrasonic rod crystal bundle dissociation treatment (20kHz, 40W / L, 10min), a dissociated attapulgite slurry is obtained. Finally, 0.25% magnesium oxide and 1.0% sodium hexametaphosphate are added to the dissociated attapulgite slurry and stirred for 4 hours. After solid-liquid separation and drying, the attapulgite-based modified materials are obtained. Among them, the quartz sand in the tailings obtained from the hydrocyclone desanding treatment is dried and reused as a sand component in cement mortar.

[0023] (2) Cement mortar mixing: Accurately weigh the following raw materials in parts by weight: 450 parts silicate cement, 110 parts grade F fly ash, 1200 parts sand (fineness modulus 2.6), 225 parts water, 6 parts polycarboxylate superplasticizer, 0.07 parts alkylbenzene sulfonate air-entraining agent, and 1.5 parts attapulgite-based material. The specific mixing process is as follows: First, mix 90% of the total water with cement, sand, and fly ash and stir evenly. Then, add the polycarboxylate superplasticizer and air-entraining agent and stir for 3 minutes. Finally, add the suspension prepared by the attapulgite-based material and 10% of the total water and stir again for 5 minutes to obtain cement mortar with added attapulgite-based modified material, labeled as cement mortar + 0.25% modified APT. Its slump change over time and strength data after 28 days are shown in the figure. Figure 3 and 4 .

[0024] Example 2

[0025] (1) Preparation of attapulgite-based modified materials: First, the raw attapulgite ore from Mingguang (with an attapulgite content >50% and a quartz sand mass fraction of approximately 6%) was pulverized to 100 mesh and dispersed in a phosphoric acid aqueous solution with a solid-liquid ratio of 1:15 at pH 4.0. The mixture was stirred and reacted for 8 hours to obtain activated attapulgite slurry. Then, after passing through a high-speed spiral classifier, a desanded attapulgite slurry was obtained. This slurry was then subjected to ultrasonic rod crystal bundle dissociation treatment (20 kHz, 40 W / L, 10 min) to obtain dissociated attapulgite slurry. Finally, 1.0% magnesium oxide and 2.0% hexamethylenetetrammonium were added to the dissociated attapulgite slurry and stirred and reacted for 4 hours. After solid-liquid separation and drying, the attapulgite-based modified materials were obtained. The quartz sand in the tailings obtained from the hydrocyclone desanding treatment was dried and reused as a sand component in cement mortar.

[0026] (2) Cement mortar mixing: Accurately weigh the following raw materials in parts by weight: 450 parts silicate cement, 120 parts grade F fly ash, 1200 parts sand (fineness modulus 3.0), 240 parts water, 7 parts polycarboxylate superplasticizer, 0.14 parts alkylbenzene sulfonate air-entraining agent, and 3 parts of the above-mentioned attapulgite-based material. The specific mixing process is as follows: First, mix 90% water with cement, sand, and fly ash and stir evenly. Then add the superplasticizer and air-entraining agent and stir for 3 minutes. Finally, add the suspension prepared by attapulgite-based material and 10% water and stir again for 5 minutes to obtain cement mortar with added attapulgite-based modified material, labeled as cement mortar + 0.5% modified APT. Its slump change over time and strength data after 28 days are shown in the figure. Figure 3 and 4 .

[0027] Example 3

[0028] (1) Preparation of attapulgite-based modified materials: First, the raw attapulgite ore from Mingguang (with an attapulgite content >50% and a quartz sand mass fraction of approximately 6%) was crushed to 100 mesh and dispersed in a phosphoric acid aqueous solution with a solid-liquid ratio of 1:15 at pH 4. The mixture was stirred and reacted for 8 hours to obtain activated attapulgite slurry. Then, after three stages of hydrocyclone treatment, a desanded attapulgite slurry was obtained. Finally, a dissociated attapulgite slurry was obtained by high-pressure homogenization at 30 MPa. Finally, 0.5% disodium hydrogen phosphate and 2.0% hexamethylenetetrammonium were added to the dissociated attapulgite slurry and stirred and reacted for 4 hours. After solid-liquid separation and drying, the attapulgite-based modified materials were obtained. The quartz sand in the tailings obtained from the hydrocyclone desanding treatment was dried and reused as a sand component in cement mortar.

[0029] (2) Cement mortar mixing: Accurately weigh the following raw materials in parts by weight: 425 parts silicate cement, 120 parts grade F fly ash, 1250 parts sand (fineness modulus 3.0), 240 parts water, 7 parts retarding naphthalene-based water-reducing agent, 0.21 parts alkylbenzene sulfonate air-entraining agent, and 6 parts of the above-mentioned attapulgite-based material. The specific mixing process is as follows: First, mix 90% water with cement, sand, and fly ash and stir evenly. Then add water-reducing agent and air-entraining agent and stir for 3 minutes. Finally, add the suspension prepared by attapulgite-based material and 10% water and stir again for 3 minutes to obtain cement mortar with added attapulgite-based modified material, labeled as cement mortar + 1.0% modified APT. Its slump change over time and strength data after 28 days are shown in the figure. Figure 3 and 4 .

[0030] Example 4

[0031] (1) Preparation of attapulgite-based modified materials: First, the raw attapulgite ore from Xuyi (wherein, the attapulgite content is >50% and the quartz sand mass fraction is about 30%) is crushed to 100 mesh and then dispersed in a sulfuric acid aqueous solution with a pH of 3.5 at a solid-liquid ratio of 1:10 and stirred for 8 hours to obtain activated attapulgite slurry. Then, after three-stage hydrocyclone treatment, a desanded attapulgite slurry is obtained. Then, after ultrasonic rod crystal bundle dissociation treatment (20kHz, 40W / L, 10min), a dissociated attapulgite slurry is obtained. Finally, 0.5% sodium alkylbenzene sulfonate and 2.0% hexamethylenetetrammonium are added to the dissociated attapulgite slurry and stirred for 4 hours. After solid-liquid separation and drying, the attapulgite-based modified materials are obtained. Among them, the quartz sand in the tailings obtained from the hydrocyclone desanding treatment is dried and reused as a sand component in cement mortar.

[0032] (2) Cement mortar mixing: Accurately weigh the following raw materials in parts by weight: 400 parts silicate cement, 25 parts sulfoaluminate cement, 120 parts F-grade fly ash, 1250 parts sand (fineness modulus 2.6), 240 parts water, 8 parts retarding naphthalene-based water-reducing agent, 0.35 parts rosin-based air-entraining agent, and 10 parts of the above-mentioned attapulgite-based material. The specific mixing process is as follows: First, mix 90% water with cement, sand, and fly ash and stir evenly. Then add water-reducing agent and air-entraining agent and stir for 3 minutes. Finally, add the suspension prepared by attapulgite-based material and 10% water and stir again for 3 minutes to obtain cement mortar with added attapulgite-based modified material, labeled as cement mortar + 2.0% modified APT. Its slump change over time and strength data after 28 days are shown in the figure. Figure 3 and 4 .

[0033] Comparative Example 1

[0034] Accurately weigh the following raw materials in parts by weight: 450 parts silicate cement, 115 parts grade F fly ash, 1250 parts sand (fineness modulus 2.8), 225 parts water, 7 parts polycarboxylate superplasticizer, and 0.07 parts alkylbenzene sulfonate air-entraining agent. The cement mortar mixing process is as follows: First, mix the water, cement, sand, and fly ash thoroughly. Then, add the superplasticizer and air-entraining agent and mix for 3 minutes to obtain the cement mortar. The slump of the cement mortar over time is shown in the figure. Figure 3 The strength data of the mortar test blocks after 28 days of curing are shown in [the original text]. Figure 4 .

Claims

1. A method for regulating the properties of cement mortar by adding attapulgite-based modifiers, characterized in that: Cement mortar is made by mixing the following raw materials in parts by weight: 425-450 parts cement, 110-120 parts fly ash, 1200-1250 parts sand, 225-240 parts water, 6-8 parts water-reducing agent, 0.07-0.35 parts air-entraining agent, and 1.5-10 parts attapulgite-based material. Among them, the attapulgite-based material is obtained by sequentially acid-activating, desanding, rod-crystal bundle dissociation and inorganic salt modification of attapulgite ore, and the quartz sand separated by desanding can be reused as a sand component in mortar; the cement mortar mixing process is as follows: first, 90% of the total water volume is mixed with cement, sand and fly ash and stirred evenly, then water-reducing agent and air-entraining agent are added and stirred for 3 minutes, and finally, a suspension prepared by attapulgite-based material and 10% of the total water volume is added and stirred again for 3-5 minutes to obtain cement mortar with added attapulgite-based modified material; The attapulgite acid activation involves crushing the raw attapulgite ore to 100 mesh, dispersing it in an aqueous solution of sulfuric acid or phosphoric acid with a pH of 3.5–4.0, and stirring for 4–8 hours. The sand removal process is achieved using a hydrocyclone or a high-speed spiral classifier. The dissociation of the attapulgite rod crystal bundles is achieved through ultrasonic or high-pressure homogenization treatment. The inorganic salt modification involves adding at least one of magnesium salts, ammonium salts, aluminum sulfate salts, phosphates, and alkylbenzene sulfonates at 0.25% to 2.0% of the mass of attapulgite and then stirring to modify it.

2. The method for regulating the performance of cement mortar by adding attapulgite-based modifiers as described in claim 1, characterized in that: The attapulgite ore contains no less than 50% attapulgite.

3. The method for regulating the properties of cement mortar by adding attapulgite-based modifiers as described in claim 1, characterized in that: The water-reducing agent is a retarding naphthalene-based water-reducing agent or a polycarboxylate-based water-reducing agent, with a water reduction rate of 25-40%.

4. The method for regulating the performance of cement mortar by adding attapulgite-based modifiers as described in claim 1, characterized in that: The air-entraining agent is one of the following: rosin-based, alkylbenzene sulfonate-based, triterpenoid saponin-based, or rosin thermopolymer-based air-entraining agents.

5. The method for regulating the properties of cement mortar by adding attapulgite-based modifiers as described in claim 1, characterized in that: The cement is at least one of silicate cement, white cement, and sulfoaluminate cement; the fly ash is grade F fly ash; and the sand is natural sand or manufactured sand with a fineness modulus of 2.6 to 3.0.

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