Cement-based-slag-steel slag cementing material and sleeve grouting material prepared from cement-based-slag-steel slag cementing material

Abstract

The invention discloses a cement-based-slag-steel slag cementing material and a prepared sleeve grouting material, and relates to the technical field of solid waste resource utilization, the cement-based-slag-steel slag composite cementing material comprises the following components by mass: 38.5%-50.4% of Portland cement, 16.5%-21.6% of sulphoaluminate cement, 5%-10% of titanium gypsum powder, 20%-25% of slag, and 3%-15% of steel slag powder; the titanium gypsum powder is obtained by drying, crushing and grinding original-state titanium gypsum to pass through a 200-mesh sieve. According to the invention, secondary utilization of industrial wastes such as titanium gypsum, slag and steel slag can be realized, pollution is reduced, the use amount of cement in the grouting material can be reduced, and the production cost is reduced. Meanwhile, the grading of sand used by the sleeve grouting material is optimized, and the working performance and the mechanical property of the reinforcing steel bar sleeve grouting material are further optimized and regulated.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization technology, specifically to a cement-based slag-steel slag cementitious material and the resulting sleeve grouting material. Background Technology

[0002] Sleeve grouting connection technology is one of the key connection methods in prefabricated concrete structures, and its connection quality directly affects the structural integrity and safety. As the core material of the connection component, sleeve grouting material must have good fluidity, adhesion, and high strength development capability to ensure construction quality and service life. Currently, commonly used grouting materials are mostly cement-based; however, a single cement system still has shortcomings in terms of early strength, fluidity, volume stability, and later strength development.

[0003] Therefore, developing high-performance, highly adjustable multi-component cementitious material systems has become an important direction for improving the performance of grouting materials. With the large-scale generation of solid waste from the construction industry, its resource utilization in the building materials field has become a research hotspot. Among these efforts, using industrial by-product gypsum to replace some traditional cementitious materials can optimize material performance while achieving environmentally friendly development.

[0004] Titanium gypsum is an industrial solid waste byproduct of titanium dioxide production. Its main component is CaSO4·2H2O, containing a certain amount of unreacted TiO2, Fe2O3, and SiO2 impurities. my country's annual emissions exceed ten million tons, with a resource utilization rate of less than 10%. Long-term stockpiling not only occupies land resources but also may cause environmental pollution. Granulated blast furnace slag (GGBS) and steel slag are also industrial solid wastes with huge output. Their large-scale, high-value-added utilization in the building materials sector is a research hotspot and an industrial demand. Granulated blast furnace slag (GGBS) is a granular material formed by water quenching of blast furnace ironmaking slag. Its main chemical components are CaO, SiO2, and Al2O3. Its microstructure is mainly glassy, ​​containing high potential activity. Steel slag is a solid waste residue discharged during the steelmaking process. It has a complex composition, containing various oxides such as CaO, SiO2, and Fe2O3. Steel slag also contains certain potential mineral activity and has good hard aggregate characteristics. How to effectively activate and utilize the activity of steel slag as a functional component in cement concrete materials is of great significance for digesting the huge stockpile of steel slag and reducing environmental pressure.

[0005] While focusing on optimizing the cementitious material system to improve the core performance of grouting materials, the performance of fine aggregates, a key component of castable high-strength mortar, cannot be ignored. Quartz sand, due to its high hardness, good particle shape, and stable chemical properties, is an ideal fine aggregate commonly used in sleeve grouting materials. However, the gradation of natural or simply crushed quartz sand is often random, making it difficult to achieve the theoretically optimal packing state.

[0006] Therefore, there is an urgent need to develop a new type of sleeve grouting material that can comprehensively utilize industrial solid wastes such as titanium gypsum, slag, and steel slag to construct high-performance cementitious materials, while simultaneously achieving optimized gradation of fine aggregates. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a novel sleeve grouting material that comprehensively utilizes industrial solid wastes such as titanium gypsum, slag, and steel slag to construct high-performance cementitious materials, while simultaneously achieving optimized fine aggregate gradation. This not only enables the secondary utilization of industrial wastes such as titanium gypsum, slag, and steel slag, reducing pollution, but also reduces the amount of cement used in the grouting material, lowering production costs. Furthermore, the optimization of the sand gradation used in the sleeve grouting material further optimizes and controls the working performance and mechanical properties of the rebar sleeve grouting material.

[0008] One objective of this invention is to provide a cement-based slag-steel slag composite cementitious material, comprising the following components by mass percentage: Portland cement 38.5%~50.4%, sulfoaluminate cement 16.5%~21.6%, titanium gypsum powder 5%~10%, slag 20%~25%, steel slag powder 3%~15%; The titanium gypsum powder is obtained by drying, crushing, and grinding undisturbed titanium gypsum to pass through a 200-mesh sieve. The steel slag powder is obtained by drying, crushing, and grinding undisturbed steel slag to pass through a 200-mesh sieve. The slag powder is obtained by drying, crushing, and grinding undisturbed slag to pass through a 400-mesh sieve. The sum of the mass percentages of silicate cement, sulfoaluminate cement, titanium gypsum powder, slag powder, and steel slag powder is 100%.

[0009] The preferred cement-slag-steel slag composite cementitious material is wherein the silicate cement is P·I 52.5 grade silicate cement, the sulfoaluminate cement is 42.5 grade sulfoaluminate cement, and the mass ratio of silicate cement to sulfoaluminate cement is 7:3.

[0010] The preferred cement-slag-steel slag composite cementitious material comprises the following components by mass percentage: 50.4% silicate cement, 21.6% sulfoaluminate cement, 5% titanium gypsum, 20% slag, and 3% steel slag.

[0011] A second objective of this invention is to provide a method for preparing a cement-based slag-steel slag composite cementitious material, comprising the following steps: Raw titanium gypsum, raw steel slag, and raw slag are processed to obtain titanium gypsum powder, steel slag powder, and slag powder, respectively. Silicate cement, sulfoaluminate cement, titanium gypsum powder, slag powder and steel slag powder are mixed to obtain cement-based slag-steel slag composite cementitious material.

[0012] A preferred method for preparing cement-based slag-steel slag composite cementitious material, wherein the mass percentage of each component in the cement-based slag-steel slag composite cementitious material is as follows: silicate cement 38.5%~50.4%, sulfoaluminate cement 16.5%~21.6%, titanium gypsum 5%~10%, slag 20%~25%, and steel slag 3%~15%.

[0013] Preferred preparation method of cement-based slag-steel slag composite cementitious material, Raw titanium gypsum is dried, crushed, and ground to pass through a 200-mesh sieve to obtain titanium gypsum powder; raw steel slag is dried, crushed, and ground to pass through a 200-mesh sieve to obtain steel slag powder; raw slag is dried, crushed, and ground to pass through a 400-mesh sieve to obtain slag powder.

[0014] The drying process includes drying to constant weight at a temperature of 100–105 °C, and the crushing process includes crushing to a particle size of no more than 1 cm.

[0015] A third objective of this invention is to provide a sleeve grouting material based on any one of the above-mentioned cement-based slag-steel slag composite cementitious materials, comprising the following raw materials in parts by weight: 100 parts of cement-based slag-steel slag composite cementitious material 110-120 parts of sand 1-1.2 parts of polycarboxylate superplasticizer Defoamer 0.2~0.3 parts, Expanding agent 0.08~0.1 parts, 23-24 parts water.

[0016] The sand is a blend of quartz sand with three particle sizes: 16-26 mesh, 26-40 mesh, and 40-70 mesh, based on close packing density.

[0017] Preferred sleeve grouting materials, based on a compact packing density blend, include: Fine sand of 40-70 mesh and medium sand of 26-40 mesh are mixed at multiple preset mass ratios, and the compact packing density of the mixed sand at each ratio is measured; the mass ratio of fine sand to medium sand corresponding to the largest compact packing density is selected, and the mixture is mixed to obtain grade I sand; The primary sand is mixed with coarse sand of 16-26 mesh at multiple preset mass ratios, and the compact packing density of the mixed sand at each ratio is measured. The mass ratio of primary sand to coarse sand corresponding to the maximum compact packing density is selected and mixed to obtain secondary sand, which is the sand for sleeve grouting material.

[0018] The compacted bulk density is determined according to the compacted density test of sand in the "Standard for Quality and Testing Methods of Sand and Stone for Ordinary Concrete" (JGJ 52-2006). The compacted bulk density is calculated using the following formula.

[0019] ρ c =(m2-m1) / V In the formula: ρ c —Close packing density, in g·cm³ -3 m1—mass of the measuring container, in grams; m2—total mass of the measuring container and sand, in grams; V—volume of the measuring container, in liters. The arithmetic mean of the two test results is used as the measured value.

[0020] A more preferred sleeve grouting material has ten preset mass ratios of fine sand to medium sand at equal intervals in the range of 0.4 to 1.3, and ten preset mass ratios of primary sand to coarse sand at equal intervals in the range of 0.6 to 1.5. Specifically, ten preset mass ratios of fine sand (40-70 mesh quartz sand) to medium sand (26-40 mesh quartz sand) are set at 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3, and the maximum bulk density corresponding to a certain ratio is obtained through experiments and calculations. The sand obtained by blending fine sand and medium sand at this ratio is primary sand. Specifically, ten preset mass ratios of primary sand and coarse sand are set at 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5, and the maximum bulk density corresponding to a certain ratio is obtained through experiments and calculations. The sand obtained by mixing primary sand with coarse sand (16-26 mesh quartz sand) in this ratio is secondary sand, which is the sand used to prepare the sleeve grouting material.

[0021] The preferred sleeve grout has an initial flowability ≥355 mm, a 30-minute flowability ≥330 mm, and a 28-day compressive strength ≥70 MPa. A more preferred sleeve grout has a 28-day compressive strength ≥85 MPa.

[0022] The preferred sleeve grouting material has a vertical expansion rate of 0.02%~2% after 3 hours, a difference of 0.02%~0.40% between the vertical expansion rates after 24 hours and 3 hours, and a water bleeding rate of 0%.

[0023] The fourth objective of this invention is to provide a method for preparing sleeve grouting material, characterized in that... Based on the compact packing density, the mass ratio of quartz sand with three particle sizes of 16~26 mesh, 26~40 mesh, and 40~70 mesh was determined, and the quartz sand with the three particle sizes was blended according to the determined mass ratio to obtain sand. The cement-slag-steel slag composite cementitious material, sand, water-reducing agent, defoamer, and expansion agent are dry-mixed to obtain powder. Then, water is completely poured in within 10 seconds and stirred to obtain sleeve grouting material.

[0024] The preferred method for preparing sleeve grouting material involves adding cement-based slag-steel slag composite cementitious material, sand, water-reducing agent, defoamer, and expansion agent into a planetary cement mortar mixer and dry-mixing for 1 minute to obtain powder. Then, pour in all the water within 10 seconds and stir. The stirring process includes: stirring slowly for 1 minute, then stirring quickly for 30 seconds, stopping for 1.5 minutes, and then stirring quickly for 1 minute to obtain the sleeve grouting material. The slow stirring has a revolution speed of 60~64 r / min and a rotation speed of 138~142 r / min, and the fast stirring has a revolution speed of 122~128 r / min and a rotation speed of 282~288 r / min.

[0025] The preferred method for preparing sleeve grouting material involves blending three types of quartz sand: mixing 40-70 mesh fine sand and 26-40 mesh medium sand at multiple preset mass ratios, measuring the compact packing density of each proportion of the mixed sand, selecting the mass ratio of fine sand to medium sand corresponding to the maximum compact packing density, and mixing to obtain grade one sand. The primary sand is mixed with coarse sand of 16-26 mesh at multiple preset mass ratios, and the compact packing density of the mixed sand at each ratio is measured. The mass ratio of primary sand to coarse sand corresponding to the maximum compact packing density is selected and mixed to obtain secondary sand, which is the sand for sleeve grouting material.

[0026] The titanium plaster powder used in this invention, after component analysis, has the following mass content for each component: 35%~45% SO3, 30%~40% CaO, 8%~12% Fe2O3, 1%~5.5% TiO2, 2%~6% SiO2, 1%~4% MgO, 0.5%~2% Al2O3, 0.5%~1% Na2O, 0.1%~1% MnO, and unavoidable impurities.

[0027] The slag powder used in this invention, after component analysis, has the following mass content for each component: 35%~45% CaO, 28%~35% SiO2, 15%~20% Al2O3, 5%~10% MgO, 1%~3% SO3, 0.1%~2% Fe2O3, 0.1%~1% Na2O, 0.1%~5% MnO, 0.1%~0.5% K2O, and unavoidable impurities.

[0028] The steel slag powder used in this invention, after component analysis, has the following mass content for each component: 35%~45% CaO, 20%~30% Fe2O3, 8%~13% SiO2, 5%~10% MnO, 2%~6% MgO, 2%~5% P2O5, 1%~3% Al2O3, 0.2%~1% SO3, 0.02%~0.1% K2O, and unavoidable impurities.

[0029] The beneficial effects of this invention are: 1. This invention incorporates industrial solid wastes such as titanium gypsum, granulated blast furnace slag, and steel slag as effective components into the cementitious system, which significantly reduces the amount of silicate cement used. The total cement content in the cementitious material is reduced to about 55% to 72%, which not only reduces the cost of raw materials but also significantly improves the resource utilization level of low-utilization solid wastes such as titanium gypsum, which is in line with the development direction of green building materials.

[0030] 2. The titanium gypsum, slag, and steel slag of this invention form a synergistic chain reaction of sulfate-activated and alkali-activated reactions, and together with two types of cement, constitute a high-performance cementitious system with multi-path, staged hydration. Titanium gypsum is the key sulfate activation source, slag is the main contributor to later-stage strength, and steel slag is an alkalinity regulator and a participant in later stages. Their combination realizes the transformation of waste into treasure, significantly reducing cement usage and environmental costs while improving performance.

[0031] 3. Based on the theory of close packing, a two-stage blending optimization was performed on three particle sizes of quartz sand: 16-26 mesh, 26-40 mesh, and 40-70 mesh, to maximize the close packing density of the mixed sand. This gradation effectively reduces the porosity between sand particles, improving the fluidity, filling capacity, and stability of the slurry at the same water-cement ratio, which is beneficial for forming a uniform and dense hardened body structure.

[0032] 4. A silicate cement-sulfoaluminate cement composite system was adopted, with the addition of titanium gypsum, slag, and steel slag. Each component exhibits a synergistic effect during hydration: sulfoaluminate cement and titanium gypsum promote the formation of ettringite, enhancing early strength; slag and steel slag are activated in an alkaline environment to generate gel phases such as CSH, filling pores and enhancing later-stage strength and durability. The resulting grout exhibits a 1-day compressive strength as high as 45.4 MPa, a 3-day compressive strength as high as 69.3 MPa, and a 28-day compressive strength as high as 87.7 MPa, demonstrating excellent and stable later-stage strength.

[0033] 5. Based on the optimization of the cementitious system and aggregate gradation, the grouting material has excellent fluidity (initial ≥355 mm, 30 min ≥330 mm) and bleeding rate of 0 through the reasonable combination of admixtures such as polycarboxylate superplasticizer and expanding agent. The expansion performance is controllable (vertical expansion rate of 0.02%~2% at 3 h, difference between 24 h and 3 h of 0.02%~0.40%), effectively compensating for early shrinkage, ensuring that the grout in the sleeve is full and saturated, and ensuring the safety and reliability of the steel bar connection. Attached Figure Description

[0034] Figure 1 Images of the original titanium plaster, titanium plaster powder, and SEM microstructure. Figure 2 Images show the appearance of undisturbed steel slag, the appearance of steel slag powder, and its microscopic morphology as shown by SEM. Figure 3 Images show the original appearance of the slag, the appearance of the slag powder, and the microscopic morphology obtained via SEM. Figure 4 Appearance images of 16-26 mesh, 26-40 mesh, and 40-70 mesh quartz sand. Figure 5 A schematic diagram showing the relationship between particle size and particle packing number. Figure 6 Schematic diagram of close packing of quartz sand Figure 7 This is a schematic flowchart illustrating the preparation process of the sleeve grouting material involved in this invention. Figure 8 This is a flowability test diagram used in the performance testing of this invention. Figure 9 This is a diagram of the compressive strength test in the performance testing of this invention. Figure 10 The present invention relates to a scanning electron microscope (SEM) microscopic image of the mortar specimen 1. Detailed Implementation

[0035] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] This invention provides a cement-slag-steel slag composite cementitious material, wherein the cement-based system includes silicate cement, sulfoaluminate cement, and titanium gypsum, and its preparation process is as follows: (1) The original titanium gypsum was dried at a temperature of 105 °C until constant weight was achieved. The dried titanium gypsum was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed titanium gypsum was then placed in a ball mill for ball milling. The ball-milled titanium gypsum powder was then passed through a 200-mesh sieve to obtain titanium gypsum powder.

[0037] (2) The original steel slag is dried at a temperature of 105 ℃ until constant weight is achieved. The dried steel slag is crushed to a particle size of no more than 1 cm while removing impurities. The crushed steel slag is then placed in a ball mill for ball milling. The ball-milled steel slag powder is then passed through a 200-mesh sieve to obtain steel slag powder.

[0038] The retrieved undisturbed slag was dried at 105 ℃ until constant weight was achieved. The dried slag was then crushed to a particle size of no more than 1 cm while removing impurities. The crushed slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 400-mesh sieve to obtain slag powder.

[0039] (3) The slag powder, titanium gypsum powder, and steel slag powder after sieving are mixed with P·I 52.5 grade silicate cement and 42.5 grade sulfoaluminate cement in a certain proportion to obtain cement-based slag-steel slag composite cementitious material. The content of each component is as follows: silicate cement 38.5%~50.4%, sulfoaluminate cement 16.5%~21.6%, titanium gypsum powder 5%~10%, slag powder 20%~25%, and steel slag powder 3%~15%. The sum of the mass percentages of the above components is 100%.

[0040] The original appearance of titanium gypsum, the dried and finely ground titanium gypsum powder, and scanning electron microscope images are shown below. Figure 1 As shown.

[0041] The original appearance of steel slag, and the dried and ground steel slag powder, as shown in the scanning electron microscope images. Figure 2 As shown.

[0042] Original slag appearance, dried and ground slag powder, and scanning electron microscope images are shown below. Figure 3 As shown.

[0043] The required mass content of each component in the titanium plaster powder used in this invention is as follows: 35%~45% SO3, 30%~40% CaO, 8%~12% Fe2O3, 1%~5.5% TiO2, 2%~6% SiO2, 1%~4% MgO, 0.5%~2% Al2O3, 0.5%~1% Na2O, 0.1%~1% MnO, and unavoidable impurities.

[0044] The required mass content of each component in the slag powder used in this invention is as follows: 35%~45% CaO, 28%~35% SiO2, 15%~20% Al2O3, 5%~10% MgO, 1%~3% SO3, 0.1%~2% Fe2O3, 0.1%~1% Na2O, 0.1%~5% MnO, 0.1%~0.5% K2O, and unavoidable impurities.

[0045] The required mass content of each component in the steel slag powder used in this invention is as follows: 35%~45% CaO, 20%~30% Fe2O3, 8%~13% SiO2, 5%~10% MnO, 2%~6% MgO, 2%~5% P2O5, 1%~3% Al2O3, 0.2%~1% SO3, 0.02%~0.1% K2O, and unavoidable impurities.

[0046] The specific mass content of each component in the titanium plaster powder used in this invention is as follows: 42.13% SO3, 34.66% CaO, 10.81% Fe2O3, 3.97% TiO2, 3.30% SiO2, 2.14% MgO, 1.20% Al2O3, 0.81% Na2O, 0.48% MnO, and the remaining 0.5% is unavoidable impurities.

[0047] The specific mass content of each component in the slag powder used in this invention is as follows: 40.48% CaO, 31.23% SiO2, 16.60% Al2O3, 6.70% MgO, 2.39% SO3, 0.41% Fe2O3, 0.81% Na2O, 0.37% MnO, 0.33% K2O, and the remaining 0.68% is unavoidable impurities.

[0048] The specific mass content of each component in the steel slag powder used in this invention is as follows: 39.75% CaO, 26.77% Fe2O3, 11.94% SiO2, 6.10% MnO, 5.20% MgO, 3.20% P2O5, 2.73% Al2O3, 0.41% SO3, 0.026% K2O, and the remaining 3.88% are unavoidable impurities.

[0049] like Figure 7 As shown, the preparation process of the sleeve grouting material using the above cement-slag-steel slag composite cementitious material is as follows: S1. Three types of quartz sand with particle sizes of 16~26 mesh, 26~40 mesh and 40~70 mesh are mixed based on the close packing density to obtain sand for sleeve grouting material. The mixing mass ratio is determined by the following method.

[0050] In this invention, quartz sand with particle sizes of 16-26 mesh, 26-40 mesh, and 40-70 mesh is referred to as coarse sand, medium sand, and fine sand, respectively, and their appearance is as follows: Figure 4 As shown in Table 1 below: Table 1. Grain size distribution of quartz sand

[0051] like Figure 5 As shown, based on the theory of close packing and specifically the theory of close packing of spherical particles, the design steps for sand gradation of sleeve grouting material are optimized and simplified. Fine sand is mixed with medium sand in a certain proportion to complete the first-stage packing. The bulk density of the first-stage packed quartz sand under the densest state is obtained by actual measurement, and the ratio of fine sand to medium sand during mixing is recorded. The proportion with the highest measured bulk density in the first-stage packing is used as the first-stage sand. The first-stage sand is then mixed with coarse sand according to the new ratio for a second-stage packing. The bulk density of the second-stage packed quartz sand when it reaches the densest state is measured, and the ratio of first-stage sand to coarse sand is recorded.

[0052] The compacted bulk density is determined according to the compacted density test of sand in the "Standard for Quality and Testing Methods of Sand and Aggregate for Ordinary Concrete" (JGJ 52-2006). The compacted bulk density is calculated using the following formula.

[0053] ρ c =(m2-m1) / V In the formula: ρ c —Close packing density, in g·cm³ -3 m1—mass of the measuring container, in grams; m2—total mass of the measuring container and sand, in grams; V—volume of the measuring container, in liters. The arithmetic mean of the two test results is used as the measured value.

[0054] This comparative study examines the effects of layer-by-layer stacking at various proportions on the optimization of quartz sand gradation, providing a certain experimental basis for further improving the performance of grouting materials for steel reinforcement connections.

[0055] Level 1 stacking: Ten mass ratios of fine sand to medium sand were set: 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3. The maximum bulk density corresponding to one of these ratios was obtained through experiments and calculations. Sand obtained by blending fine sand and medium sand in this ratio is classified as Grade 1 sand.

[0056] Secondary stacking: Ten ratios of primary sand to coarse sand were set at mass ratios of 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5. The maximum bulk density corresponding to one of these ratios was obtained through experiments and calculations. The sand obtained by mixing primary sand and coarse sand at this ratio was designated as secondary sand, which is the sand used for preparing the subsequent working sleeve grout.

[0057] The bulk density test results are as follows Figure 6 In the primary packing, experimental measurements showed that the densest packing density, reaching 1.481 g•cm³, was achieved when the mass ratio of fine sand to medium sand was 1.1. -3 In the secondary packing, the bulk density initially increases and then decreases with the increase of the mass ratio of primary sand to coarse sand. This indicates that a certain amount of primary sand has filled the packing voids of the coarse sand. The densest packing density is highest when the ratio is 1.1, reaching 1.533 g·cm³. -3 After conversion, the mass ratio of quartz sand with particle sizes of 16~26 mesh, 26~40 mesh, and 40~70 mesh is 1:0.52:0.58.

[0058] This optimal gradation reduces the porosity between sand particles, effectively improving the fluidity and filling properties of the grout under the same water-cement ratio. This allows the grout to form a stable, uniform grout structure with good flow retention within the sleeve. The increased bulk density of the sand particles makes the system more compact and reduces material usage, improving the stability of the grout and the density of the hardened structure. This, in turn, enhances the compressive strength of the grout joint and its bonding performance with the reinforcing steel and the inner wall of the sleeve.

[0059] S2. Add 110-120 parts of sand and 100 parts of cement-based slag-steel slag composite cementitious material obtained by mixing according to the mass ratio in step S1 to a planetary cement mortar mixer. At the same time, add 1-1.2 parts of water-reducing agent, 0.2-0.3 parts of defoamer and 0.08-0.1 parts of expansion agent. Dry mix slowly for 1 min (60-64 r / min revolution and 138-142 r / min rotation) to make the powder evenly mixed. Within 10 s, pour 23-24 parts of water into the planetary cement mortar mixer and mix slowly for 1 min, then mix quickly for 30 s (122-128 r / min revolution and 282-288 r / min rotation). Stop for 1.5 min, then mix quickly for 1 min to obtain the sleeve grouting material. Both the defoamer and the expanding agent are commercially available products. The defoamer is a white powder with mineral oil and polyethylene glycol as its main chemical components. It is a nonionic surfactant suitable for cement dry powder mortar, model P803. The expanding agent is a yellow powder plastic expanding agent with bauxite mineral as its main material, which is used to compensate for the shrinkage of the grout during the plastic stage.

[0060] The present invention will be further described in detail below through specific embodiments.

[0061] Example 1 This embodiment provides a cement-based slag-steel slag composite cementitious material, wherein the cement-based system includes silicate cement, sulfoaluminate cement, and titanium gypsum. Its preparation process is as follows: (1) The original titanium gypsum was dried at a temperature of 105°C until constant weight was achieved. The dried titanium gypsum was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed titanium gypsum was then placed in a ball mill for ball milling. After ball milling, the gypsum was passed through a 200-mesh sieve to obtain titanium gypsum powder.

[0062] (2) The original steel slag was dried at a temperature of 105 ℃ until constant weight was achieved. The dried steel slag was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed steel slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 200-mesh sieve to obtain steel slag powder.

[0063] The retrieved undisturbed slag was dried at 105 ℃ until constant weight was achieved. The dried slag was then crushed to a particle size of no more than 1 cm while removing impurities. The crushed slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 400-mesh sieve to obtain slag powder.

[0064] (3) Mix 431.3 g of P·I 52.5 grade silicate cement, 184.9 g of 42.5 grade sulfoaluminate cement, 42.75 g of titanium gypsum powder from step (1), 171 g of slag powder from step (2), and 25.05 g of steel slag powder to obtain a cement-based slag-steel slag composite cementitious material. The cementitious material contains 50.4% silicate cement, 21.6% sulfoaluminate cement, 5% titanium gypsum, 20% slag, and 3% steel slag.

[0065] The preparation process of sleeve grouting material using the above composite cementitious material is as follows: Add 950 g of sand, 855 g of cement-based slag-steel slag composite cementitious material prepared in step (3), 8.55 g of polycarboxylate superplasticizer, 1.71 g of defoamer, and 0.684 g of expansion agent to a planetary cement mortar mixer, and dry mix slowly for 1 min (in this embodiment, slow mixing is a revolution speed of 60 r / min and a rotation speed of 140 r / min) to make the powder uniformly mixed; within 10 s, completely pour in 196.6 g of water, slowly mix for 1 min, then quickly mix for 30 s (in this embodiment, quick mixing is a revolution speed of 125 r / min and a rotation speed of 285 r / min), stop for 1.5 min, and then quickly mix for 1 min to obtain mortar, wherein the mass ratio of cement-based slag-steel slag composite cementitious material, sand, superplasticizer, defoamer, expansion agent, and water is 100:111.1:1:0.2:0.08:23. The mortar was placed in a 40×40×160 mm mold to obtain mortar specimen 1.

[0066] Example 2 This embodiment provides a cement-based slag-steel slag composite cementitious material, wherein the cement-based system includes silicate cement, sulfoaluminate cement, and titanium gypsum. Its preparation process is as follows: (1) The original titanium gypsum was dried at a temperature of 105 °C until constant weight was achieved. The dried titanium gypsum was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed titanium gypsum was then placed in a ball mill for ball milling. After ball milling, the gypsum was passed through a 200-mesh sieve to obtain titanium gypsum powder.

[0067] (2) The original steel slag was dried at a temperature of 105 ℃ until constant weight was achieved. The dried steel slag was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed steel slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 200-mesh sieve to obtain steel slag powder.

[0068] The retrieved undisturbed slag was dried at 105 ℃ until constant weight was achieved. The dried slag was then crushed to a particle size of no more than 1 cm while removing impurities. The crushed slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 400-mesh sieve to obtain slag powder.

[0069] (3) Mix 389.03 g of P·I 52.5 grade silicate cement, 166.72 g of 42.5 grade sulfoaluminate cement, 42.75 g of titanium gypsum powder from step (1), 213.75 g of slag powder from step (2), and 42.75 g of steel slag powder to obtain cement-based slag-steel slag composite cementitious material. The cementitious material content is 45.5% silicate cement, 19.5% sulfoaluminate cement, 5% titanium gypsum, 25% slag, and 5% steel slag.

[0070] The preparation process of sleeve grouting material using the above composite cementitious material is as follows: Add 950 g of sand, 855 g of cement-based slag-steel slag composite cementitious material prepared in step (3), 8.55 g of polycarboxylate superplasticizer, 1.71 g of defoamer, and 0.684 g of expansion agent to a planetary cement mortar mixer. Mix slowly for 1 min (in this embodiment, slow mixing is 60 r / min revolution speed and 140 r / min rotation speed) to make the powder uniformly mixed. Within 10 s, pour in 196.6 g of water completely and mix slowly for 1 min, then mix quickly for 30 s (in this embodiment, fast mixing is 125 r / min revolution speed and 285 r / min rotation speed), stop for 1.5 min, and then mix quickly for 1 min to obtain mortar. The mass fraction ratio of cement-based slag-steel slag composite cementitious material, sand, superplasticizer, defoamer, expansion agent, and water is 100:111.1:1:0.2:0.08:23. The mortar was placed in a 40×40×160 mm mold to obtain mortar specimen 2.

[0071] Example 3 This embodiment provides a cement-based slag-steel slag composite cementitious material, wherein the cement-based system includes silicate cement, sulfoaluminate cement, and titanium gypsum. Its preparation process is as follows: (1) The original titanium gypsum was dried at a temperature of 105°C until constant weight was achieved. The dried titanium gypsum was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed titanium gypsum was then placed in a ball mill for ball milling. After ball milling, the gypsum was passed through a 200-mesh sieve to obtain titanium gypsum powder.

[0072] (2) The original steel slag was dried at a temperature of 105 ℃ until constant weight was achieved. The dried steel slag was crushed to a particle size of no more than 1 cm and impurities were removed. The crushed steel slag was then placed in a ball mill for ball milling. After ball milling, the slag was passed through a 200-mesh sieve to obtain steel slag powder.

[0073] The retrieved slag was dried at 105 ℃ until constant weight was achieved. The dried slag was then crushed to a particle size of no more than 1 cm while removing impurities. The crushed slag was then placed in a ball mill for ball milling. The ball-milled steel slag powder was then passed through a 400-mesh sieve to obtain slag powder.

[0074] (3) Mix 329.18 g of P·I 52.5 grade silicate cement, 141.07 g of 42.5 grade sulfoaluminate cement, 42.75 g of titanium gypsum treated in step (1), 213.75 g of slag powder, and 128.25 g of steel slag treated in step (2) to obtain cement-based slag-steel slag composite cementitious material. The cementitious material content is 38.5% silicate cement, 16.5% sulfoaluminate cement, 5% titanium gypsum, 25% slag, and 15% steel slag.

[0075] The preparation process of sleeve grouting material using the above composite cementitious material is as follows: Add 950 g of sand, 855 g of cement-based slag-steel slag composite cementitious material prepared in step (3), 8.55 g of polycarboxylate superplasticizer, 1.71 g of defoamer, and 0.684 g of expansion agent to a planetary cement mortar mixer. Mix slowly for 1 min (in this embodiment, slow mixing is 60 r / min revolution speed and 140 r / min rotation speed) to make the powder uniformly mixed. Within 10 s, pour in 196.6 g of water completely and mix slowly for 1 min, then mix quickly for 30 s (in this embodiment, fast mixing is 125 r / min revolution speed and 285 r / min rotation speed), stop for 1.5 min, and then mix quickly for 1 min to obtain mortar. The mass fraction ratio of cement-based slag-steel slag composite cementitious material, sand, superplasticizer, defoamer, expansion agent, and water is 100:111.1:1:0.2:0.08:23. The mortar was placed in a 40×40×160 mm mold to obtain mortar specimen 3.

[0076] Comparative example: This comparative example relates to the preparation of silicate cement-sulfoaluminate cement binary cementitious mortar, and its preparation process is as follows: 598.5 g of P·I 52.5 grade silicate cement, 256.5 g of 42.5 grade sulfoaluminate cement, 950 g of quartz sand, 8.55 g of polycarboxylate superplasticizer, 1.71 g of defoamer, and 0.684 g of expansive agent were added to a planetary cement mortar mixer and mixed at a slow dry speed for 1 min to ensure uniform mixing of the powder. Within 10 s, 196.6 g of water was completely poured in and the mixture was slowly mixed for 1 min, then rapidly mixed for 30 s, paused for 1.5 min, and then rapidly mixed for 1 min to obtain the mortar (the slow and rapid mixing speeds in this comparative example are the same as in Example 1). The mortar was placed in a 40×40×160 mm mold to form mortar comparative specimen 1.

[0077] Performance testing The performance tests involved the flowability, compressive strength, vertical expansion rate, and bleeding rate of mortar specimen 1, mortar specimen 2, mortar specimen 3, and mortar comparison specimen 1.

[0078] Initial flowability, 30-minute flowability, 1-day, 3-day, and 28-day compressive strength, vertical expansion rate, and bleeding rate were tested for mortar specimens 1, 2, and 3, and control specimen 1, respectively. The results are shown in Table 2 below. Table 2 Test Data for Each Indicator

[0079] The flowability test results are as follows Figure 8 As shown, the compressive strength test results are as follows: Figure 9 As shown, the SEM image of mortar specimen 1 is as follows: Figure 10 As shown.

[0080] The test results show that: The mortar comparison specimen 1 used a composite system of silicate cement and sulfoaluminate cement, without the addition of titanium gypsum, slag, and steel slag. The compressive strength of this group at 1d, 3d, and 28d was approximately 53.6MPa, 60.3MPa, and 62.5MPa, respectively. The overall hydration relied solely on the cement itself, lacking the participation of external sulfur sources and potential active minerals, resulting in limited hydration products and a generally weak ability to densify the structure. At the same time, the vertical expansion rate was 0, indicating a lack of shrinkage compensation ability.

[0081] Mortar specimens 1-3, all based on the comparative examples, were supplemented with titanium gypsum, slag, and steel slag, resulting in significantly improved performance. Taking mortar specimen 1 as an example, the titanium gypsum provided an external sulfur source, promoting the rapid formation of a large amount of AFt, thus significantly increasing early strength. Its 1-day, 3-day, and 28-day compressive strengths reached 45.4 MPa, 69.3 MPa, and 87.7 MPa, respectively, significantly higher than those of mortar specimen 2 (approximately 42.9 / 59.6 / 71.4 MPa) and mortar specimen 3 (approximately 34.0 / 59.4 / 74.6 MPa). Simultaneously, mortar specimen 1 exhibited a 3-hour micro-expansion rate of 0.891%, effectively compensating for early shrinkage, while mortar specimens 2 and 3 showed slightly lower rates (0.640% and 0.414%, respectively). The continuous hydration of slag provides CSH gel, ensuring the strength increase in the later stage of 28 days; steel slag plays the role of particle filling and structural support, but its excessive dosage in mortar specimen 3 leads to a decrease in early strength due to high water absorption and insufficient activity.

[0082] SEM images of mortar specimen 1 reveal a large number of interwoven, needle-like ettringite (AFt) crystals and flocculent, gel-like C-(A)-SH hydration products within the specimen. These materials fill and tightly overlap each other, forming a dense three-dimensional framework structure. Simultaneously, some incompletely reacted slag and steel slag particles are encapsulated by secondary hydration products and participate in later reactions, significantly reducing pore connectivity. This micro-densification structure effectively explains the high compressive strength and good volumetric stability of specimen 1 at 28 days, indicating that the cement-based slag-steel slag composite cementitious system can achieve a unified balance between micro-expansion compensation and strength enhancement through synergistic hydration and filling effects, demonstrating significant advantages in engineering applications.

[0083] In summary, the high bulk density sand system obtained through optimized quartz sand particle size distribution further enhances the construction adaptability, strength development, and connection reliability of the sleeve grouting material, providing a key performance foundation for the cement solid waste cementitious material system of this invention. Example 1, based on the optimal bulk density of quartz sand with different particle sizes, uses a combination of "appropriate amount of titanium gypsum + medium slag + small amount of steel slag" mixed with composite cement as a cementing material to prepare a sleeve grouting material for rebar connections, achieving optimal synergistic effects. It exhibits good flowability, far exceeding the specifications' requirements of initial flowability ≥300 mm and 30-minute flowability ≥260 mm; its strength also meets the specifications, with significant subsequent strength replenishment, ensuring structural safety; and it possesses suitable micro-expansion characteristics, with no bleeding, demonstrating excellent overall performance.

Claims

1. A cement-based slag-steel slag composite cementitious material, characterized in that, Includes the following components by mass percentage: Portland cement 38.5%~50.4%, sulfoaluminate cement 16.5%~21.6%, titanium gypsum powder 5%~10%, slag powder 20%~25%, steel slag powder 3%~15%; The titanium gypsum powder is obtained by drying, crushing, and grinding raw titanium gypsum to pass through a 200-mesh sieve. The steel slag powder is obtained by drying, crushing, and grinding raw steel slag to pass through a 200-mesh sieve. The slag powder is obtained by drying, crushing, and grinding raw slag to pass through a 400-mesh sieve.

2. The cement-based slag-steel slag composite cementitious material as described in claim 1, characterized in that, The silicate cement is P·I 52.5 grade silicate cement, and the sulfoaluminate cement is 42.5 grade sulfoaluminate cement. The mass ratio of silicate cement to sulfoaluminate cement is 7:

3.

3. The cement-based slag-steel slag composite cementitious material as described in claim 1, characterized in that, It includes the following components by mass percentage: silicate cement 50.4%, sulfoaluminate cement 21.6%, titanium gypsum 5%, slag 20%, and steel slag 3%.

4. A method for preparing a cement-based slag-steel slag composite cementitious material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Raw titanium gypsum, raw steel slag, and raw slag are processed to obtain titanium gypsum powder, steel slag powder, and slag powder, respectively. Silicate cement, sulfoaluminate cement, titanium gypsum powder, slag powder and steel slag powder are mixed to obtain cement-based slag-steel slag composite cementitious material.

5. A sleeve grouting material based on the cement-slag-steel slag composite cementitious material as described in any one of claims 1 to 3, characterized in that, Includes the following raw materials by weight: 100 parts of cement-based slag-steel slag composite cementitious material 110-120 parts of sand 1-1.2 parts of polycarboxylate superplasticizer Defoamer 0.2~0.3 parts, Expanding agent 0.08~0.1 parts, 23-24 parts water; The sand is a blend of quartz sand with three particle sizes: 16-26 mesh, 26-40 mesh, and 40-70 mesh, based on close packing density.

6. The sleeve grouting material as described in claim 5, characterized in that, Based on close packing density blends include: Fine sand of 40-70 mesh and medium sand of 26-40 mesh are mixed at multiple preset mass ratios, and the compact packing density of the mixed sand at each ratio is measured; the mass ratio of fine sand to medium sand corresponding to the largest compact packing density is selected, and the mixture is mixed to obtain grade I sand; The primary sand is mixed with coarse sand of 16-26 mesh at multiple preset mass ratios, and the compact packing density of the mixed sand at each ratio is measured. The mass ratio of primary sand to coarse sand corresponding to the maximum compact packing density is selected and mixed to obtain secondary sand, which is the sand for sleeve grouting material.

7. The sleeve grouting material as described in claim 6, characterized in that, Ten preset mass ratios are set at equal intervals in the range of 0.4 to 1.3 for fine sand and medium sand, and ten preset mass ratios are set at equal intervals in the range of 0.6 to 1.5 for primary sand and coarse sand.

8. The sleeve grouting material as described in claim 5, characterized in that, The initial flowability of the sleeve grout is ≥355 mm, the flowability at 30 min is ≥330 mm, and the compressive strength at 28 d is ≥70 MPa.

9. The sleeve grouting material as described in claim 5, characterized in that, The vertical expansion rate of the sleeve grouting material is 0.02%~2% after 3 hours, and the difference between the vertical expansion rates after 24 hours and 3 hours is 0.02%~0.40%; the bleeding rate is 0%.

10. A method for preparing a sleeve grouting material as described in any one of claims 5 to 9, characterized in that, Based on the compact packing density, the mass ratio of quartz sand with three particle sizes of 16~26 mesh, 26~40 mesh, and 40~70 mesh was determined, and the quartz sand with the three particle sizes was blended according to the determined mass ratio to obtain sand. The cement-slag-steel slag composite cementitious material, sand, water-reducing agent, defoamer, and expansion agent are dry-mixed to obtain powder. Then, water is completely poured in within 10 seconds and stirred to obtain sleeve grouting material.

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