Magnesite-lime synergistic activated slag-based material for improving quality of concrete pole and preparation method thereof

Abstract

The present application relates to inorganic cementing material and centrifugal forming concrete product technical field, specifically relates to a kind of magnesium lime synergic excitation slag-based material for improving the quality of concrete pole and preparation method thereof.The present application discloses a kind of magnesium lime synergic excitation slag-based material for improving the quality of concrete pole and preparation method thereof, the slag-based material is by granulated blast furnace slag powder, ultrafine slag powder, pre-stabilized converter steel slag micro powder, light-burned magnesia, carbide slag, wollastonite powder, gypsum, sodium silicate micro powder, water reducing agent, air entraining agent, aggregate and water composition.Pre-stabilized steel slag micro powder free calcium oxide content is 1.5%~2.0%, and the citric acid activity value of light-burned magnesia is 60~90s.The present application is by free calcium oxide and magnesium-containing hydration product in time domain superimposed expansion inhibition shrinkage, by segmented centrifugation in the direction of pole wall thickness forms outer layer dense, inner layer air-entraining gradient structure, suitable for high-cold saline soil area concrete pole.

Description

Technical Field

[0001] This invention relates to the field of inorganic cementitious materials and centrifugally molded concrete products, specifically to a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles and its preparation method. Background Technology

[0002] Circular concrete poles typically employ low water-cement ratio concrete, centrifugal molding, and steam curing. However, in high-altitude saline-alkali soil regions, multiple environmental factors interact, including freeze-thaw cycles, chloride or sulfate migration, wet-dry cycles, and temperature differences, placing higher demands on pole durability. While alkali-activated slag materials offer advantages such as early strength and high solid waste utilization, their pore structure is dominated by fine capillary pores and gel pores. Early reactions are concentrated, making them prone to self-shrinkage, drying shrinkage, and shrinkage due to water loss from the centrifugal inner wall. Furthermore, if the hardened body lacks stable microbubbles, the water pressure and osmotic pressure generated during salt solution freezing are difficult to release, further accelerating salt-freeze erosion and crack propagation.

[0003] To address these issues, existing technologies attempt to reduce shrinkage by adding fibers, chemical admixtures, mineral additives, and altering curing regimes. For example, CN121552524A discloses a method for preparing eco-friendly cement poles using industrial solid waste. This method involves co-grinding steel slag and granulated blast furnace slag, then compounding them with fly ash, carbide slag, and desulfurized gypsum. After centrifugal molding, a curing regime is employed, consisting of approximately 1 hour of static rest, 3-4 hours at 60℃, 4-6 hours at 80℃, and 2-3 hours at 50℃. However, this method does not introduce lightly calcined magnesium oxide, does not precisely control the content of free calcium oxide in the steel slag, and does not utilize the bubble migration patterns during centrifugal molding to construct a gradient structure, making the curing process relatively complex.

[0004] In summary, how to innovate a new preparation method that can effectively suppress the shrinkage of alkali-activated slag materials, improve their resistance to salt freezing, and take into account the formation of gradient structures, while ensuring the adaptability of the centrifugal molding process and mechanical properties of the poles, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a magnesium-lime synergistic activated slag-based material and its preparation method for improving the quality of concrete poles, so as to solve the technical problems of shrinkage cracking and poor salt-freezing durability of alkali-activated slag poles in the prior art.

[0006] The specific technical solution is as follows: This invention provides a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles, comprising pre-activated composite powder, aggregate, and water; the pre-activated composite powder is based on a total mass of 100 parts of granulated blast furnace slag powder and pre-stabilized converter steel slag powder, wherein the granulated blast furnace slag powder comprises 75-85 parts and the pre-stabilized converter steel slag powder comprises 15-25 parts. The raw materials also include: 5-8 parts of ultrafine granulated blast furnace slag powder, 5-8 parts of lightly calcined magnesia, 8-12 parts of calcium carbide slag, and wollastonite powder. The pre-stabilized converter slag powder contains 3-5 parts of gypsum, 2-3 parts of sodium silicate, and 1-2 parts of sodium silicate powder. The free calcium oxide content in the pre-stabilized converter slag powder is 1.5%-2.0%. The water-cement ratio of the slag-based material is 0.28-0.32, defined as the ratio of the total water content to the total mass of the pre-activated composite powder. The total water content includes mixing water and water introduced from the polycarboxylate superplasticizer and sodium dodecyl sulfonate. The ratio of the total mass of the aggregate to the total mass of the pre-activated composite powder is 3.5:1.

[0007] Furthermore, the lightly calcined magnesium oxide has a citric acid activity value of 60-90s, an MgO mass fraction of not less than 90%, and an active MgO mass fraction of not less than 85%; the carbide slag has a Ca(OH)₂ mass fraction of not less than 80%, a moisture content of not more than 1.0%, a chloride ion mass fraction of not more than 0.05%, and D 50 The value is 8~25μm.

[0008] Furthermore, the sodium silicate micro powder has a modulus of 1.8 to 2.2, and the contents of Na2O and SiO2 match the modulus, wherein the mass fraction of Na2O is 24% to 28%.

[0009] This invention also provides a method for preparing a magnesium-lime synergistic activated slag-based material to improve the quality of concrete poles, comprising the following steps: S1: The converter steel slag is crushed, pre-stabilized, and then ground. The free calcium oxide content is measured at the same time to obtain pre-stabilized converter steel slag micro powder. Granulated blast furnace slag powder, ultrafine granulated blast furnace slag powder, pre-stabilized converter steel slag micro powder and wollastonite powder are ground together to obtain mechanochemical pre-activated powder.

[0010] S2: Mix the pre-activated powder with lightly calcined magnesium oxide, carbide slag, gypsum and sodium silicate powder to obtain pre-activated composite powder; stir the pre-activated composite powder with aggregate, add mixing water, polycarboxylate superplasticizer and sodium dodecyl sulfonate, mix evenly to obtain concrete mixture, i.e. slag-based material finished product.

[0011] The obtained slag-based material was used for the centrifugal molding of utility poles. The specific steps are as follows: S3: The concrete mixture is poured into the steel mold of the pole and centrifuged in three stages to form a gradient structure; after centrifugation, the exposed inner wall surface is pre-wetted by spraying.

[0012] S4: After spraying and pre-wetting, the molded poles are left to stand still for pre-curing, followed by steam curing. After cooling, they are removed from the kiln to obtain magnesium-lime synergistic activated slag-based concrete poles.

[0013] Furthermore, the grinding after the pre-stabilization treatment described in S1 is performed under the following conditions: temperature 170~190℃, treatment time 30~60 minutes, until the specific surface area is 400~500m². 2 / kg; the free calcium oxide content is controlled within the range of 1.5% to 2.0%; the co-grinding conditions are set as follows: ball-to-material ratio (2.5 to 3.5): 1, rotation speed 350 to 450 rpm, and grinding time 12 to 18 minutes.

[0014] Further, in S2, the mixing time is 3-8 minutes; the stirring time for mixing the pre-activated composite powder and aggregate is set to 50-70 seconds; and the stirring time for uniform mixing is set to 90-150 seconds.

[0015] Furthermore, the three-stage centrifugal molding described in S3 is specifically as follows: first, centrifuging at low speed for 1-3 minutes under a centrifugal acceleration of 10-20g; then, centrifuging at medium speed for 5-7 minutes under a centrifugal acceleration of 30-70g to allow the bubbles to migrate towards the center; and finally, centrifuging at high speed for 1-3 minutes under a centrifugal acceleration of 70-130g to achieve compaction. The spray pre-wetting conditions are set to a time of 30-90 seconds and a droplet size of 50-100μm.

[0016] Furthermore, the static pre-curing described in S4 has a pre-curing time of 10-30 minutes; the steam curing requires heating to 55-65°C at a heating rate of 8-12°C / h, maintaining the temperature at 95% relative humidity for 3-5 hours, followed by heating to 75-85°C and maintaining the temperature at 75-85°C for 4-6 hours; the cooling rate is set to 6-10°C / h.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Controllable coagulation and process adaptability: This invention uses carbide slag and sodium silicate micro powder to synergistically regulate alkalinity release, which helps to adapt the coagulation time to the operation requirements of centrifugal molding process. At the same time, the use of solid alkali activation components avoids the use of liquid strong alkali and has good compatibility with existing pole production processes.

[0018] (2) Double expansion superposition to compensate shrinkage: The present invention uses the magnesium-containing hydration products generated by the hydration of free calcium oxide and lightly burned magnesium oxide in pre-stabilized steel slag as double expansion sources. The two are superimposed in the time domain, which is beneficial to compensate for the shrinkage of alkali-activated slag materials.

[0019] (3) Gradient antifreeze with dense outer layer and sparse inner layer: The present invention uses a segmented centrifugal process to make the bubbles migrate toward the center of the component, forming a radial gradient structure in the wall thickness direction with a lower permeability outer layer containing controlled microbubbles and a relatively higher air content in the inner layer. This is beneficial to balance the concrete’s resistance to salt and frost erosion and structural uniformity.

[0020] (4) Low-carbon and environmentally friendly solid waste utilization: This invention uses industrial solid waste such as slag, steel slag, and carbide slag as the main raw materials, realizing the resource utilization of solid waste and having good environmental benefits. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating a magnesium-lime synergistic slag-based material for improving the quality of concrete poles and its preparation method, according to the present invention.

[0022] Figure 2 These are XRD phase diffraction patterns of different hydration ages in Example 1 of the present invention.

[0023] Figure 3 The curves showing the relative content of each hydration product as a function of age in Example 1 of this invention are shown.

[0024] Figure 4 The curves showing the restricted length changes of the samples from Example 1 (H1), Comparative Example 3 (C3), Comparative Example 4 (C4), and Comparative Example 5 (C5) of this invention from 0 to 90 days are shown.

[0025] Figure 5 The curves show the effect of the free calcium oxide content of the pre-stabilized steel slag obtained in Example 1 of this invention on the material's mechanical properties, expansion, and salt-freezing durability. Detailed Implementation

[0026] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0027] This invention proposes a magnesium-lime synergistic activated slag-based material for improving the quality of concrete utility poles and its preparation method, such as... Figure 1 The diagram shows a flowchart of a magnesium-lime synergistic slag-based material for improving the quality of concrete poles and its preparation method, according to the present invention. The detailed preparation steps are as follows: 1. Preparation of pre-activated powder Converter slag is pre-stabilized by autoclaving and then ground to control the free calcium oxide content within the range of 1.5% to 2.0%, resulting in pre-stabilized steel slag powder. This treatment helps to make the subsequent hydration and expansion behavior of free calcium oxide in the steel slag relatively controllable in the time domain, reducing the risk of volume expansion caused by the concentrated hydration of excessive free calcium oxide. Granulated blast furnace slag powder, ultrafine granulated blast furnace slag powder, pre-stabilized converter slag powder, and wollastonite powder are co-ground. This allows the ultrafine slag particles to pre-activate the surface of the main slag glass through mechanochemical effects, increasing its surface active sites and facilitating the deagglomeration of the glass structure during subsequent hydration reactions.

[0028] 2. Preparation and mixing of composite powder The pre-activated powder was mixed with lightly calcined magnesium oxide, carbide slag, gypsum, and sodium silicate powder. The carbide slag, acting as a rapid alkali source, provided a high concentration of hydroxide and calcium ions in the initial mixing stage, promoting the dissolution of the slag glass. The citric acid activity of lightly calcined magnesium oxide, with a value of 60-90s, gradually hydrated in an alkaline environment, helping to maintain alkalinity in the middle stage. The sodium silicate powder, working in conjunction with the carbide slag, maintained the alkalinity of the pore solution for a longer period, providing conditions for the continuous hydration of the slag. The mixed composite powder was then combined with aggregates, mixing water, polycarboxylate superplasticizer, and sodium dodecyl sulfonate to obtain a concrete mixture, i.e., the finished slag-based material.

[0029] The obtained slag-based material was used for the centrifugal molding of utility poles. The specific steps are as follows: 3. Centrifugal molding and spray pre-wetting The mixture is poured into the pole mold in one go and centrifuged in three stages. The low-speed stage ensures the mixture is evenly distributed on the inner wall of the mold; the medium-speed stage causes the less dense air bubbles to migrate towards the center of rotation under centrifugal force; and the final speed stage further densifies the outer layer of slurry, thus creating a gradient structure along the pole wall thickness with a lower air content in the outer layer and a higher air content in the inner layer. Immediately after centrifugation, a nozzle is inserted into the hollow cavity of the pole to pre-wet the exposed inner wall surface. This helps replenish some of the moisture lost from centrifugal drainage and provides conditions for the hydration of the expansion components in the subsequent curing stage.

[0030] 4. Steam curing After being pre-wetted by spraying, the molded poles were statically cured and then sent to a steam curing kiln. They were first cured at 60℃, then the temperature was increased to 80℃ for further curing. During steam curing, the hydration expansion of free calcium oxide in the pre-stabilized steel slag and the volume expansion of magnesium-containing hydration products generated from the hydration of lightly burned magnesium oxide superimposed in the time domain. These two factors worked together to inhibit the shrinkage of the alkali-activated slag material during the hardening process. After curing, the poles were cooled and removed from the kiln, yielding a magnesium-lime synergistic activated slag-based concrete pole.

[0031] The technical solution designed by this invention to solve the existing problems includes the following key points: 1. Temporal superposition compensation mechanism of dual expansion sources Traditional alkali-activated slag materials typically rely on a single expansion source to compensate for shrinkage. However, the expansion time domain of a single expansion source often does not perfectly match the rapid shrinkage stage of the alkali-activated slag material, resulting in limited compensation effects. This invention uses free calcium oxide and lightly calcined magnesium oxide from pre-stabilized steel slag powder as dual expansion sources. The expansion effects of the two sources differ in their time domains, creating a cumulative compensation effect. This mechanism involves two levels of reactions: First, free calcium oxide hydrates to form calcium hydroxide. This reaction begins in the early stages of steam curing, and its expansion effect is most significant within 3-10 days of age, accompanied by an increase in solid phase volume. Second, lightly calcined magnesium oxide hydrates in an alkaline environment to form magnesium hydroxide. Magnesium hydroxide further reacts with aluminate ions dissolved from the slag glass to form a hydrotalcite-like phase. The formation of this phase is accompanied by an increase in volume, and its expansion effect is relatively delayed, gradually increasing mainly within 7-14 days of age. The expansion products generated by the two types of reactions overlap in the temporal domain during the 7-10 day age period. During this stage, the expansion of free calcium oxide has not yet subsided, while the formation of the hydrotalcite-like phase has begun to contribute to the volume increase. This overlap helps to more fully compensate for the volume shrinkage of alkali-activated slag materials during the rapid shrinkage development stage. Furthermore, since the expansion peak of free calcium oxide occurs in the earlier age period, while the expansion peak of hydrotalcite-like phase occurs in the later age period, this partial temporal overlap may be more adaptable to the time-varying trend of the shrinkage rate of alkali-activated slag materials than a single expansion source, thus helping to reduce the drying shrinkage rate and improve the volumetric stability of the material.

[0032] To verify the phase evolution law of the above-mentioned dual expansion source superposition compensation. Figure 2 and Figure 3 The XRD phase diffraction patterns of Example 1 at different hydration ages and the relative contents of each hydration product as a function of age are presented respectively. Figure 2 It can be seen that as the hydration age increases from 3 days to 28 days, the intensity of the characteristic diffraction peaks of hydrotalcite-like materials gradually increases, while the intensity of the diffraction peaks of free calcium oxide and magnesium oxide gradually decreases. From... Figure 3 It is observed that the content of free calcium oxide decreases rapidly within 3–10 days of curing, while the content of calcium hydroxide increases accordingly. The content of hydrotalcite-like phase increases significantly within 7–14 days of curing, overlapping with the consumption time of free calcium oxide (7–10 days). This indicates that lightly calcined magnesia gradually hydrates under steam curing conditions, reacting with aluminate ions dissolved from the slag to form a hydrotalcite-like phase. The expansion time of this phase overlaps with that of free calcium oxide. These phase evolution patterns correspond to the development trend of shrinkage strain, providing microstructural evidence for the mechanism of dual expansion source superposition compensating for shrinkage.

[0033] 2. Centrifugal gradient molding method based on alkali-activated slurry rheological properties Traditional centrifugal molding processes are primarily designed for ordinary cement concrete. However, alkali-activated slag slurry differs from ordinary cement slurry in its particle morphology and surface chemical properties, resulting in variations in thixotropy and yield stress. Traditional centrifugation methods struggle to achieve the desired gradient distribution. This invention designs a segmented, accelerated centrifugation process based on the rheological properties of alkali-activated slag slurry. The principle involves the migration behavior of components with different densities in a centrifugal force field: bubbles, with a significantly lower density than the slurry, migrate towards the center of rotation under centrifugal force; while solid particles and the slurry migrate towards the outer wall. Because alkali-activated slag slurry has a high yield stress, the migration rate of particles and bubbles is relatively slow at lower speeds, which helps maintain the homogeneity of the mixture. As the speed gradually increases, the shear rate increases, reducing the apparent viscosity of the slurry and consequently decreasing the resistance to bubble migration, promoting bubble migration towards the center in the mid-speed range. The higher speed in the final stage promotes the compaction of the slurry wall, and due to the shorter centrifugation time, bubbles that have migrated to the center are less likely to migrate back to the outer wall, thus creating a gradient distribution with lower air content in the outer layer and higher air content in the inner layer along the component's wall thickness. The outer concrete layer has good impermeability due to its low air content, while the inner concrete layer has good frost resistance due to its rich air bubbles, which is beneficial for balancing the impermeability and frost resistance of the pole components. At the same time, spraying pre-wetting treatment on the outer surface after centrifugation helps to replenish some of the moisture lost from centrifugation drainage, providing conditions for the hydration of expansion components in the subsequent steam curing stage.

[0034] Example 1 Table 1 Raw Material Information Table ; A magnesium-lime synergistic activated slag-based material for improving the quality of concrete utility poles and its preparation method, comprising the following steps: S1: After crushing the converter slag to a particle size ≤5mm, place it in a pressure autoclave and pre-stabilize it for 45 minutes under saturated steam pressure at 180℃. Then grind it to a specific surface area of ​​450m². 2 / kg, the free calcium oxide content was determined to be 1.7% by ethylene glycol-EDTA titration, and pre-stabilized converter steel slag powder was obtained; 80 parts of granulated blast furnace slag powder, 6 parts of ultrafine granulated blast furnace slag powder, 20 parts of pre-stabilized converter steel slag powder and 4 parts of wollastonite powder were put into a planetary ball mill and dry-mixed and ground for 15 minutes at a ball-to-material ratio of 3:1 and a rotation speed of 400 rpm, so that the ultrafine slag particles pre-activate the surface of the main slag glass body through mechanochemical effect, and mechanochemical pre-activated powder is obtained.

[0035] S2: The pre-activated powder is simply mixed with 6 parts of lightly calcined magnesium oxide, 10 parts of calcium carbide slag, 2.5 parts of gypsum and 1.5 parts of sodium silicate micro powder in a twin-shaft paddle mixer for 5 minutes to obtain the pre-activated composite powder. The pre-activated composite powder, fine aggregate and coarse aggregate are added to the mixer at a mass ratio of 1:1.3:2.2 and dry-mixed for 60 seconds. Then, mixing water, 1.2 parts of polycarboxylate superplasticizer and 0.04 parts of sodium dodecyl sulfonate are added, and the water-cement ratio is controlled at 0.30. The water-cement ratio is the ratio of the total mass of mixing water to the pre-activated composite powder. The water brought in by the admixture solution is included in the total mass of mixing water. Wet-mix for 120 seconds to obtain the concrete mixture, which is the finished slag-based material.

[0036] The obtained slag-based material was used for the centrifugal molding of utility poles. The specific steps are as follows: S3: The concrete mixture is poured into the steel mold of the pole in one go, and centrifuged in three stages using a centrifuge: first, centrifuge at a low speed of 15g for 2 minutes, then centrifuge at a medium speed of 50g for 6 minutes to allow the air bubbles to migrate towards the center, and finally centrifuge at a high speed of 100g for 2 minutes to compact it and form a gradient structure; after centrifugation and molding, immediately insert the nozzle into the hollow cavity of the pole and spray the exposed inner wall surface for 60 seconds to pre-wet it, with the droplet size controlled at 80μm.

[0037] S4: After being pre-wetted by spraying, the molded poles were left to stand at room temperature for 20 minutes for pre-curing. After the surface showed no obvious free water, they were sent to a steam curing kiln and heated to 60°C at a rate of 10°C / h. They were then kept at a constant temperature for 4 hours under a relative humidity of 95%. Subsequently, the temperature was increased to 80°C and kept at a constant temperature for 5 hours. During this stage, the hydration expansion of f-CaO and the overall volume expansion of magnesium hydration products were superimposed in the time domain, jointly covering the peak period of slag shrinkage. Finally, the poles were cooled to room temperature at a rate of 8°C / h and removed from the kiln to obtain magnesium lime synergistic slag-based concrete poles.

[0038] Example 2 The preparation method is the same as in Example 1, except that: S1: 75 parts granulated blast furnace slag powder, 5 parts ultrafine granulated blast furnace slag powder, 25 parts pre-stabilized converter steel slag powder and 3 parts wollastonite powder. S2: 5 parts lightly calcined magnesium oxide, 8 parts calcium carbide slag, 2 parts gypsum and 1 part sodium silicate powder; 1 part polycarboxylate superplasticizer and 0.03 parts sodium dodecyl sulfonate; control the water-cement ratio at 0.28; All other steps are the same.

[0039] Example 3 The preparation method is the same as in Example 1, except that: S1: 85 parts granulated blast furnace slag powder, 8 parts ultrafine granulated blast furnace slag powder, 15 parts pre-stabilized converter steel slag powder and 5 parts wollastonite powder. S2: 8 parts lightly calcined magnesium oxide, 12 parts calcium carbide slag, 3 parts gypsum and 2 parts sodium silicate powder; 1.5 parts polycarboxylate superplasticizer and 0.05 parts sodium dodecyl sulfonate; control the water-cement ratio at 0.32; All other steps are the same.

[0040] Example 4 The preparation method is the same as in Example 1, except that: S1: Pre-stabilize at 170℃ and saturated steam pressure for 30 minutes; grind to a specific surface area of ​​400 m². 2 / kg, the free calcium oxide content was determined to be 1.5% by ethylene glycol-EDTA titration; dry-mixed and milled for 12 minutes at a ball-to-powder ratio of 2.5:1 and a rotation speed of 350 rpm; S2: Simple mix for 3 minutes; dry mix for 50 seconds; wet mix for 90 seconds; S3: First, centrifuge at low speed for 1 minute under centrifugal acceleration of 10g, then centrifuge at medium speed for 5 minutes under centrifugal acceleration of 30g to make the bubbles migrate towards the center, and finally centrifuge at high speed for 1 minute under centrifugal acceleration of 70g to make them dense; spray pre-wet for 30 seconds, and control the droplet size at 50μm; S4: Static pre-curing for 10 minutes; heating to 55℃ at a rate of 8℃ / h, and maintaining constant temperature for 3 hours at 95% relative humidity; continuing to heat to 75℃ and maintaining constant temperature for 4 hours; cooling at a rate of 6℃ / h. All other steps are the same.

[0041] Example 5 The preparation method is the same as in Example 1, except that: S1: Pre-stabilize under saturated steam pressure at 190℃ for 60 minutes; grind to a specific surface area of ​​500 m². 2 / kg, the free calcium oxide content was determined to be 2% by ethylene glycol-EDTA titration; dry-mixed and milled for 18 minutes at a ball-to-powder ratio of 3.5:1 and a rotation speed of 450 rpm; S2: Simple mix for 8 minutes; dry mix for 70 seconds; wet mix for 150 seconds; S3: First, centrifuge at a low speed of 20g for 3 minutes, then centrifuge at a medium speed of 70g for 7 minutes to allow the bubbles to migrate towards the center, and finally centrifuge at a high speed of 130g for 3 minutes until compacted; spray pre-wet for 90 seconds, and control the droplet size at 100μm; S4: Static pre-curing for 30 minutes; heating to 65℃ at a rate of 12℃ / h, and maintaining constant temperature for 5 hours under a relative humidity of 95%; continuing to heat to 85℃ and maintaining constant temperature for 6 hours; cooling at a rate of 10℃ / h. All other steps are the same.

[0042] Comparative Example 1 The traditional process for preparing slag-based materials involves mixing 100 parts of granulated blast furnace slag powder with 10-20 parts of alkali activator, adding aggregate and water, with a water-cement ratio of 0.30-0.40, and stirring to obtain a concrete mixture, which is the slag-based material.

[0043] Comparative Example 2 The preparation method is the same as in Example 1, except that: S1, S2: The step-by-step grinding process is omitted, and all raw materials are ball-milled together for 28 minutes to obtain pre-activated powder; All other steps are the same.

[0044] Comparative Example 3 The preparation method is the same as in Example 1, except that: S1: Omit the preparation and addition steps of pre-stabilized converter steel slag powder and replace it with an equal mass of granulated blast furnace slag powder; All other steps are the same.

[0045] Comparative Example 4 The preparation method is the same as in Example 1, except that: S1: The pre-stabilization treatment step is omitted, and unstabilized steel slag is used subsequently; All other steps are the same.

[0046] Comparative Example 5 The preparation method is the same as in Example 1, except that: S2: Omit the step of adding lightly calcined magnesium oxide and replace it with an equal mass of granulated blast furnace slag powder; All other steps are the same.

[0047] Comparative Example 6 The preparation method is the same as in Example 1, except that: S2: Omit the steps of adding carbide slag and sodium silicate powder, and replace them with a composite alkali activator prepared by sodium hydroxide and liquid water glass. The replacement amount is calculated according to the equivalent of Na2O, so that the total alkalinity is equivalent to the alkalinity provided by carbide slag and sodium silicate powder in the original scheme. All other steps are the same.

[0048] Comparative Example 7 The preparation method is the same as in Example 1, except that: S2: The step of adding sodium silicate powder is omitted; All other steps are the same.

[0049] Comparative Example 8 The preparation method is the same as in Example 1, except that: S2: The step of adding sodium dodecyl sulfonate is omitted; All other steps are the same.

[0050] Comparative Example 9 The preparation method is the same as in Example 1, except that: S3: Omit the three-stage acceleration step and replace it with constant centrifugation at 50g for 10 minutes; All other steps are the same.

[0051] Experimental Example 1 The slag-based materials and concrete poles prepared in Examples 1-5 and Comparative Examples 1-9 were subjected to process adaptation and strength performance testing: (1) Initial setting: Referring to GB / T 1346-2024 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", the Vicat apparatus method was used for determination. The slag-based material was loaded into a circular mold and leveled before being placed under the Vicat apparatus. The test needle was allowed to fall freely until it stopped sinking. The time from the addition of water to when the test needle sank into the neat cement paste to a distance of 4±1mm from the bottom plate was measured as the initial setting time. Each group of valid samples should have no less than 3 samples, and the final result is the average.

[0052] (2) Demolding compressive strength: Referring to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", on the day of demolding after centrifugation and curing of the pole, a core sample with a diameter of 100 mm was drilled circumferentially at the middle of the pole wall thickness. The core sample was then processed into a specimen with a height-to-diameter ratio of 1:1 and placed between the bearing plates of a compression testing machine. The specimen was continuously and uniformly loaded at the specified loading rate until failure. The failure load was recorded and the compressive strength value was calculated. Each group of valid specimens should have no less than 3 specimens, and the final result is the average.

[0053] (3) 28-day compressive strength: GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". After the steam curing of the pole is completed and standard curing continues for 28 days, a core sample with a diameter of 100 mm is drilled circumferentially at the middle of the pole wall thickness. The core sample is then processed into a specimen with a height-to-diameter ratio of 1:1. The specimen is placed between the bearing plates of a compression testing machine and continuously and uniformly loaded at the specified loading rate until the specimen fails. The failure load is recorded and the 28-day compressive strength value is calculated. Each group of valid specimens should have no less than 3 specimens, and the final result is the average.

[0054] Experimental Example 2 Shrinkage inhibition and durability performance tests were conducted on the slag-based materials and concrete poles prepared in Examples 1-5 and Comparative Examples 1-9: (1) Shrinkage strain at 90 days: Referring to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete", after the pole is steam-cured and continues to be cured to the specified age, an arc-shaped plate specimen including the entire cross-section from the outer wall to the inner wall is cut along the thickness direction of the pole. It is then processed into a strip specimen with a length of not less than 400 mm, a width of 100 mm, and a thickness of 100 mm. Reflective targets are pre-embedded at both ends of the specimen. The specimen is then moved into a constant temperature and humidity chamber (temperature 20±2℃, relative humidity 60±5%) to determine the initial setting time of the concrete. After the initial setting, the initial reading is taken. The measurement is then continuously taken at the set time interval until 90 days. The length change rate is calculated as the shrinkage strain value. There should be no less than 3 valid specimens in each group, and the final result is the average.

[0055] (2) Air bubble spacing coefficient of hardened concrete: Referring to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete", after the pole is steam-cured and continues to be cured according to standard for 28 days, an arc-shaped specimen including the full cross-section of the wall thickness is cut along the circumferential direction at the middle position of the pole. The observation surface is carefully ground and polished with 400 and 800 grit diamond abrasives respectively until the edges of the air bubbles are clear, and a specimen that meets the observation requirements is prepared. The prepared specimen is placed on the microscope stage, and the wire spacing marks are attached to both ends of the observation surface so that the selected wires are evenly distributed within the observation surface. The length of the truncated chord of the air bubble is measured for each wire using an eyepiece micrometer, and the air bubble spacing coefficient is calculated according to the Powers formula. Each group of valid specimens should have no less than 3 specimens, and the final result is the average.

[0056] (3) Salt-freezing erosion amount after 56 cycles: Referring to GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete", after the pole is steam-cured and continues to be cured to the specified age, an arc-shaped specimen including the outer wall surface is cut along the circumferential direction at the middle position of the pole. The original outer wall surface is used as the test surface. The sides and top surface of the specimen are sealed with sealing materials such as epoxy resin, leaving only one test surface in contact with a NaCl solution with a mass concentration of about 3%~5%. A salt-freezing cycle test is carried out for 56 cycles. After each cycle, the eroded material is collected and weighed, and the cumulative erosion amount per unit area is calculated as the salt-freezing erosion amount. Each group of valid samples should have no less than 3 samples, and the final result is the average.

[0057] Table 2 Comparison of setting and strength performance test results between the examples and the comparative examples ; Table 3 Comparison of shrinkage and durability test results between the examples and comparative examples ; The experimental results of Examples 1-5 and Comparative Examples 1-9 are shown in Tables 2 and 3. The slag-based material prepared in Example 1 of this invention has an initial setting time of 61 min, which meets the requirements for workable time in centrifugal molding of electric poles; a demolding compressive strength of 49.2 MPa, which meets the requirements for demolding and prestressing tension; a 28-day compressive strength of 92.3 MPa, which meets the structural bearing requirements; a 90-day shrinkage strain of 312 με; a bubble spacing coefficient of 210 μm; and a salt-freezing erosion amount of 0.42 kg / m² after 56 cycles. 2 This indicates that the present invention, through the superposition compensation mechanism of f-CaO and magnesium-containing hydration products and the gradient structure of three-stage centrifugal molding, maintains excellent mechanical properties while taking into account shrinkage inhibition, antifreeze and anti-salt erosion properties.

[0058] Example 2: Reducing the composition of each cementitious material to the lower limit resulted in an increase in 90-day shrinkage strain to 407 με, indicating that the superimposed compensation effect of the two expansion sources weakened after reducing the total amount of cementitious material and the amount of expansion component, proving the feasibility of the lower limit of the proportion range of the present invention. Example 3: Increasing the composition of each cementitious material to the upper limit resulted in a decrease in 90-day shrinkage strain to 203 με, the lowest among all examples, indicating that the shrinkage compensation effect was further enhanced after increasing the amount of expansion component, and the 28-day compressive strength was 92.1 MPa, proving the feasibility of the upper limit of the proportion range of the present invention. Example 4: Reducing each process parameter to the lower limit resulted in a decrease in 90-day shrinkage strain to 407 με. The shrinkage strain increased to 392 με, indicating that the process parameters have a synergistic effect on the material properties, but all indicators still meet the design requirements, proving the feasibility of the lower limit of the process range of the present invention. In Example 5, the process parameters were increased to the upper limit, and the steam curing temperature and time were extended, which is conducive to the full hydration of f-CaO and the generation of magnesium-containing hydration products. The shrinkage strain decreased to 227 με, but the demolding compressive strength and 28-day compressive strength were not significantly improved compared with Example 1. This indicates that within the range of process parameters given in the present invention, the adjustment of process parameters has a relatively limited effect on strength, but a relatively significant effect on improving shrinkage and durability.

[0059] Due to the lack of key technologies, the overall effects of Comparative Examples 1-9 were reduced to varying degrees compared to the Examples. Comparative Example 1 used a traditional process to prepare slag-based materials, mixing granulated blast furnace slag powder with a liquid alkali activator before casting. This process did not involve centrifugal molding or steam curing. The 90-day shrinkage strain increased to 493 με, indicating that the traditional liquid alkali activation system lacked an expansion compensation mechanism and insufficient shrinkage suppression. In Comparative Example 2, after ball milling all raw materials together for 28 minutes, the 90-day shrinkage strain increased to 682 με, indicating that the lightly calcined magnesium oxide reacted prematurely with the alkali-activated components during the long ball milling process, weakening the effect. The expansion compensation effect of f-CaO during the steam curing stage was observed, and stepwise grinding is necessary to protect the reactivity of lightly calcined magnesia. In Comparative Example 3, after omitting the steel slag powder, the lack of f-CaO expansion source resulted in an increase in shrinkage strain to 528 με at 90 days, demonstrating that the early expansion compensation provided by f-CaO during the 3-10 day curing period plays an irreplaceable role in inhibiting the shrinkage of alkali-activated slag materials. In Comparative Example 4, after using unstabilized steel slag, the shrinkage strain at 90 days showed a negative value of -121 με (net expansion), and the compressive strength at 28 days decreased to 84.6 MPa, while the salt-freezing erosion increased to 2.75 kg / m³. 2 The results indicate that when the f-CaO content is too high, excessive later expansion leads to the propagation of microcracks inside the material, verifying the necessity of controlling f-CaO within a narrow window of 1.5%~2.0%. In Comparative Example 5, after replacing lightly calcined magnesia with an equal mass of granulated blast furnace slag powder, the 90-day shrinkage strain increased to 887 με, indicating that without lightly calcined magnesia, no magnesium-containing hydration products are generated in the system, the dual expansion source superposition compensation mechanism fails, and it cannot effectively inhibit the shrinkage of alkali-activated slag material. In Comparative Example 6, after omitting carbide slag and sodium silicate powder and replacing them with sodium hydroxide solution and liquid water glass, the initial setting time was extended to 116 min, and the 28-day compressive strength decreased to 77.8 MPa, indicating that the early high alkalinity environment provided by carbide slag is a necessary condition for the rapid dissolution of slag glass, and the strength development is severely insufficient when there is a lack of rapid alkali source. In Comparative Example 7, after omitting sodium silicate powder, the bubble spacing coefficient increased to 417 μm, and the 56-time salt freeze erosion increased to 2.18 kg / m². 2 This indicates that the synergistic regulation of alkalinity release by sodium silicate micropowder and calcium carbide slag has a regulatory effect on the rheology and bubble stability of the slurry; in Comparative Example 8, after omitting sodium dodecyl sulfonate, the bubble spacing coefficient increased to 524 μm and the salt freeze erosion amount increased to 3.14 kg / m³ after 56 cycles. 2 This indicates that without sodium dodecyl sulfonate, the mixture lacks a stable source of microbubbles, and a sufficient amount of uniform bubble cluster cannot be formed in the inner layer of the component during centrifugation. This verifies the necessity of using sodium dodecyl sulfonate in conjunction with a three-stage centrifugation process to achieve a gradient structure. In Comparative Example 9, after centrifugation at a constant speed without segmented acceleration, the bubble spacing coefficient increased to 432 μm, and the salt freeze erosion amount increased to 2.38 kg / m³ after 56 cycles. 2This indicates that constant high-speed centrifugation cannot form a bubble gradient distribution, and three-stage acceleration centrifugation is the key process measure for enriching the inner layer of bubbles and densifying the outer layer.

[0060] To visually demonstrate the differences between the embodiments and the comparative examples in the shrinkage development process, Figure 4 The constraint length variation curves of samples from Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 5 from 0 to 90 days are given. Figure 4 It can be seen that the shrinkage strain development in Example 1 within 90 days was relatively gradual, and the final shrinkage value was significantly lower than that of Comparative Examples 3 and 5, and the negative shrinkage phenomenon of Comparative Example 4 was not observed, which is consistent with the shrinkage data pattern shown in Table 3. Furthermore, to verify the necessity of narrow-window control of free calcium oxide content, Figure 5 The effects of free calcium oxide content in pre-stabilized steel slag on the 28-day compressive strength, 90-day shrinkage strain, and 56 cycles of salt-freezing erosion are presented. Figure 5 It can be seen that the material has the best overall performance when the free calcium oxide content is in the range of 1.5% to 2.0%; when it is below 1.5%, the shrinkage strain increases, and when it is above 2.0%, the salt freeze erosion increases significantly, indicating that the free calcium oxide content needs to be controlled within the narrow window.

[0061] In summary, this invention achieves a comprehensive effect by superimposing the expansion of free calcium oxide and magnesium hydration products generated from the hydration of lightly calcined magnesium oxide in pre-stabilized steel slag powder over time, thereby compensating for the shrinkage of alkali-activated slag materials. Through a three-stage centrifugal process, a gradient antifreeze structure with a dense outer layer and an air-entrained inner layer is formed along the pole's wall thickness. Furthermore, by synergistically regulating alkalinity release with calcium carbide slag and sodium silicate powder, pre-activating the ultrafine slag mechanically and chemically, and employing two-stage steam curing, this invention provides a slag-based material solution for concrete poles in cold, saline-alkali soil areas that requires no strong liquid alkali, has strong process adaptability, and excellent durability.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A magnesium-lime synergistic activated slag-based material for improving the quality of concrete utility poles, comprising pre-activated composite powder, aggregate, and water, characterized in that, The pre-activated composite powder is based on a total mass of 100 parts of granulated blast furnace slag powder and pre-stabilized converter steel slag powder, wherein the granulated blast furnace slag powder comprises 75-85 parts and the pre-stabilized converter steel slag powder comprises 15-25 parts. The raw materials also include: 5-8 parts of ultrafine granulated blast furnace slag powder, 5-8 parts of light-burned magnesia, 8-12 parts of calcium carbide slag, 3-5 parts of wollastonite powder, 2-3 parts of gypsum, and 1-2 parts of sodium silicate powder. The pre-stabilized converter steel slag powder contains 1.5%-2.0% free calcium oxide. The light-burned magnesia has a citric acid activity value of 60-90s, an MgO mass fraction of not less than 90%, and an active MgO mass fraction of not less than 85%. The calcium carbide slag has a Ca(OH)2 mass fraction of not less than 80%, a moisture content of not more than 1.0%, and a chloride ion mass fraction of not more than 0.05%. 50 The particle size is 8~25μm; the sodium silicate micro powder has a modulus of 1.8~2.2, and the Na2O and SiO2 contents match the modulus, wherein the mass fraction of Na2O is 24%~28%; the water-cement ratio of the slag-based material is 0.28~0.32, and the water-cement ratio is defined as the ratio of the total water content to the total mass of the preactivated composite powder, wherein the total water content includes mixing water and water introduced from the polycarboxylate superplasticizer and sodium dodecyl sulfonate; the ratio of the total mass of the aggregate to the total mass of the preactivated composite powder is 3.5:

1.

2. The method for preparing a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 1, characterized in that, Includes the following steps: After crushing and pre-stabilizing the converter slag, it is ground and the free calcium oxide content is measured to obtain pre-stabilized converter slag powder. Granulated blast furnace slag powder, ultrafine granulated blast furnace slag powder, pre-stabilized converter slag powder and wollastonite powder are ground together and then mixed with lightly calcined magnesium oxide, carbide slag, gypsum and sodium silicate powder to obtain pre-activated composite powder. The pre-activated composite powder is mixed with aggregate, and mixing water, polycarboxylate superplasticizer and sodium dodecyl sulfonate are added and mixed evenly to obtain concrete mixture, which is the finished slag-based material.

3. The preparation method of a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 2, characterized in that, The pre-stabilization treatment followed by grinding is performed under the following conditions: temperature 170~190℃, treatment time 30~60 minutes, until the specific surface area is 400~500 m². 2 / kg.

4. The preparation method of a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 2, characterized in that, The conditions for the co-grinding are set as follows: ball-to-material ratio (2.5~3.5):1, rotation speed 350~450 rpm, and grinding time 12~18 minutes.

5. The preparation method of a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 2, characterized in that, The mixing time is 3-8 minutes; the stirring time for mixing the pre-activated composite powder and aggregate is set to 50-70 seconds; the mixing time for achieving uniform mixing is set to 90-150 seconds.

6. The method for preparing a magnesium-lime synergistic activated slag-based material to improve the quality of concrete poles as described in claim 2, characterized in that, The slag-based material is used for the centrifugal molding of utility poles. The specific steps are as follows: the concrete mixture is put into the steel mold of the utility pole and centrifuged in three stages to form a gradient structure; after centrifugal molding, the exposed inner wall surface is sprayed with pre-wet; then the pre-wetted utility pole with mold is statically pre-cured, followed by steam curing, and after cooling, it is taken out of the kiln to obtain a magnesium-lime synergistic activated slag-based material concrete utility pole.

7. The preparation method of a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 6, characterized in that, The three-stage centrifugal molding process is as follows: first, centrifugation at low speed for 1-3 minutes at a centrifugal acceleration of 10-20g; then, centrifugation at medium speed for 5-7 minutes at a centrifugal acceleration of 30-70g to allow the bubbles to migrate towards the center; and finally, centrifugation at high speed for 1-3 minutes at a centrifugal acceleration of 70-130g to achieve compaction. The spray pre-wetting conditions are set to a time of 30-90 seconds and a droplet size of 50-100μm.

8. The method for preparing a magnesium-lime synergistic activated slag-based material for improving the quality of concrete poles as described in claim 6, characterized in that, The static curing pre-curing time is set to 10-30 minutes; the steam curing requires heating to 55-65°C at a rate of 8-12°C / h, maintaining the temperature at 95% relative humidity for 3-5 hours, followed by heating to 75-85°C and maintaining the temperature at 75-85°C for 4-6 hours; the cooling rate is set to 6-10°C / h.

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