Steel slag cement concrete accelerated curing method based on three-stage microwave control

Abstract

The application discloses a kind of steel slag cement concrete accelerated curing methods based on three-stage microwave control, including preparation steel slag cement concrete mixture C, after pouring out mixer of prepared steel slag cement concrete mixture C, uniform pouring into test mould, sequentially carried out initial microwave accelerated curing, mid-term microwave curing and later microwave curing in microwave curing equipment;After the end of later curing, concrete component is removed from microwave curing equipment and can be demoulded, then natural cooling to room temperature can complete curing;Three-stage microwave curing strategy is used, by accurately regulating and controlling microwave frequency, power, temperature and heating rate and other parameters of each stage, realize the rapid, uniform heating of concrete, effectively promote the hydration reaction of each component in steel slag cement concrete, accelerate the strength development of concrete, while it can realize efficient, energy-saving, environmental protection curing effect.

Description

Technical Field

[0001] This invention belongs to the field of maintenance technology for civil engineering materials, and more specifically, relates to a method for accelerating the curing of steel slag cement concrete based on three-level microwave control. Background Technology

[0002] With the continuous development of my country's construction industry, concrete has become an important component of engineering structures, and its construction efficiency and quality assurance have always been key concerns in the industry. In the concrete production process, the selection of cement and curing techniques have always been crucial factors affecting concrete performance. In recent years, steel slag, as a major solid waste generated during the steel industry, has been rationally applied to cement concrete production. This can not only effectively solve the problem of steel slag storage and reduce environmental pressure, but also reduce concrete production costs to a certain extent, achieving resource recycling and meeting the current requirements of energy conservation, emission reduction, and environmental protection. However, because steel slag cement releases relatively low heat during hydration, the curing effect is difficult to guarantee, resulting in slow concrete strength development. This problem restricts the widespread application of steel slag cement concrete.

[0003] Traditional concrete curing methods typically include water curing, covering curing, and steam curing. Water curing promotes cement hydration by keeping the concrete surface moist, usually requiring continuous water spraying or covering with damp cloths. Covering curing uses plastic film or straw mats to reduce moisture evaporation and maintain stable humidity. Steam curing is commonly used for precast components, accelerating cement hydration through steam heating and shortening curing time. While traditional methods are low-cost and simple to operate, they also have drawbacks such as difficulty in moisture control and long curing times. Traditional concrete curing methods also often suffer from high energy consumption, long cycles, and stringent environmental requirements.

[0004] Therefore, there is an urgent need for a high-efficiency, energy-saving, and highly adaptable method for curing steel slag cement concrete. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control. Through rational microwave radiation design and curing time control, this method effectively enhances the early strength of steel slag cement concrete and solves the problems encountered during its curing process. Through experiments and engineering applications, this invention achieves low energy consumption and a short construction cycle while ensuring the development of concrete strength. This invention, through microwave accelerated curing technology, not only solves the problem of insufficient early strength in steel slag cement concrete but also achieves efficient, energy-saving, and environmentally friendly curing effects. It possesses significant technical and application advantages, promoting the widespread application of steel slag cement concrete in practical engineering projects. It provides the construction industry with a high-performance, green, and sustainable concrete material and its curing method, achieving efficient, early-strength, and high-quality technical effects, meeting the current construction industry's multiple demands for construction efficiency, quality assurance, and environmental protection.

[0006] To achieve the above objectives, the present invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control, comprising the following steps:

[0007] S1: Pour ordinary silicate cement, silica fume, and steel slag-based solid waste into a planetary mixer and dry mix for 1 minute to obtain mixture A;

[0008] S2: Add river sand, steel slag sand, limestone crushed stone, and steel slag coarse aggregate to mixture A and dry mix for 2 minutes to obtain mixture B;

[0009] S3: After mixing the polycarboxylate superplasticizer with water, slowly add it to the mixture B in two batches, and mix for 2 minutes at a temperature of 10-30℃ to obtain steel slag cement concrete mixture C.

[0010] S4: After pouring the steel slag cement concrete mixture C out of the mixer, it is evenly poured into the test mold and placed in the microwave curing equipment for initial microwave accelerated curing, intermediate microwave curing and later microwave curing in sequence.

[0011] The initial microwave accelerated curing time in step S4 is 0.4 to 0.8 hours, the temperature is controlled between 45 and 60 degrees Celsius, the frequency used for the initial microwave curing is set to 1500 to 3000 MHz, the power is set to 1000 to 5000 W, and the heating rate is set to 10 to 20 degrees Celsius / h.

[0012] The intermediate microwave curing time in step S4 is 0.5 to 1.0 h, the temperature is controlled between 50 and 75 °C, the frequency used for intermediate microwave curing is set to 2450 to 5000 MHz, the power is set to 2000 to 5000 W, and the heating rate is set to 10 to 20 °C / h.

[0013] The subsequent microwave curing time is 0.5 to 1.0 hours, the temperature is controlled between 70 and 90 degrees Celsius, the frequency used for the subsequent microwave curing is set to 2450 to 5000 MHz, the power is set to 3000 to 5000 W, and the heating rate is set to 15 to 20 degrees Celsius / hour.

[0014] S5: After the later curing is completed, the concrete component can be removed from the microwave curing equipment for demolding, and then allowed to cool naturally to room temperature to complete the curing.

[0015] Further, the raw material composition by weight in step S1 is 10.2 to 11.8 parts of ordinary Portland cement, 1.0 to 1.4 parts of silica fume, and 9.7 to 11.3 parts of steel slag-based solid waste.

[0016] Furthermore, the steel slag-based solid waste mentioned in step S1 includes steel slag powder, slag, raw ash, desulfurization gypsum, and silica fume;

[0017] 100 parts of steel slag-based solid waste include 31.8–42.2 parts of steel slag powder, 19.1–25.9 parts of slag, 14.2–19.8 parts of raw ash, 13.5–17.5 parts of desulfurized gypsum, and 7.7–9.4 parts of silica fume.

[0018] Further, in step S2, the raw material composition by weight is 26.2-28.4 parts fine aggregate, 18.8-22.9 parts limestone crushed stone, and 19.9-24.5 parts steel slag coarse aggregate.

[0019] Furthermore, the fine aggregate mentioned in step S2 includes river sand and steel slag sand;

[0020] 100 parts of fine aggregate includes 40-60 parts of river sand and 40-60 parts of steel slag sand.

[0021] Further, in step S3, the raw material composition by weight is 0.3-0.4 parts of polycarboxylate superplasticizer and 6.2-6.3 parts of water.

[0022] Furthermore, the polycarboxylic acid superplasticizer is composed of acrylic acid, methacrylic acid, maleic anhydride, polyoxyethylene allyl ester, polyoxyethylene methacrylate, polyoxyethylene acrylate, water, etc.

[0023] Furthermore, in step S2, the stirring speed is 60-100 r / min, and the mixture is poured into blocks after the stirring time is reached.

[0024] Furthermore, the initial microwave curing described in step S4 adopts a continuous microwave heating curing method;

[0025] The intermediate microwave curing adopts a microwave gradient heating curing method, with 500W as a gradient to achieve gradual temperature increase;

[0026] The subsequent microwave curing continues to use intermittent microwave heating curing method, with 10 minutes as a cycle, each cycle heating for 5 minutes and stopping for 5 minutes, the total cycle length is 0.5 to 1 hour, the heating rate is controlled at 15 to 20℃ / h, and the temperature is controlled at 70 to 90℃.

[0027] Furthermore, the microwave curing equipment includes a microwave source, a waveguide, a cavity, and a control system. The microwave source is capable of generating microwaves with a frequency of 1500–5000 MHz and a power of 1000–5000 W. The microwaves generated by the microwave source are transmitted to the cavity through the waveguide. The cavity is used to place steel slag cement concrete components. The control system is capable of precisely controlling the frequency, power, and curing time of the microwaves, as well as the temperature and heating rate within the cavity.

[0028] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0029] (1) This invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control. By adopting a three-level microwave curing strategy, the microwave frequency, power, temperature and heating rate at each stage are precisely controlled, which effectively promotes the hydration reaction of various components in steel slag cement concrete and accelerates the development of concrete strength. The 72h compressive strength of Examples 2-6 reached 55.4-57.7MPa and the splitting tensile strength reached 4.2-4.4MPa, which are much higher than the comparative examples of traditional curing and simplified microwave curing. This shows that the method can efficiently improve the early strength of concrete and solve the problem of slow strength development of steel slag cement concrete.

[0030] (2) This invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control. The microwave radiation technology used utilizes microwave energy to accelerate the vibration and friction of water molecules inside the concrete, causing the concrete temperature to rise rapidly, thereby accelerating the hydration reaction of cement and promoting the rapid increase of concrete strength. Microwave radiation has the characteristic of selective heating, which can uniformly heat the inside of the concrete and avoid the cracking problem caused by the large temperature gradient in traditional curing methods.

[0031] (3) This invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control. The microwave curing equipment used can precisely control the curing parameters, achieving rapid and uniform heating of the concrete. Compared with traditional steam curing and other methods, it significantly shortens the curing time and reduces energy consumption. In addition, this method is not limited by environmental conditions and can adapt to the curing needs of concrete components of different sizes and shapes, providing a flexible and efficient solution for the application of steel slag cement concrete in various engineering scenarios.

[0032] (4) This invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control, which enables steel slag-based solid waste to be effectively applied to the production of cement concrete. This not only consumes a large amount of steel slag and reduces environmental pressure, but also reduces production costs and realizes resource recycling. It is in line with the concepts of energy conservation, emission reduction and green environmental protection, and provides strong technical support for the widespread application of steel slag cement concrete, thus promoting the sustainable development of the construction industry. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of steel slag cement concrete mix C in an embodiment of the present invention, which is a method for accelerating the curing of steel slag cement concrete based on three-level microwave control.

[0034] Figure 2 This is a schematic flowchart of a method for accelerating the curing of steel slag cement concrete based on three-level microwave control, according to an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] To overcome the shortcomings of traditional curing methods and meet the dual demands of modern construction projects for construction efficiency and quality, microwave curing technology has emerged and is gradually showing great application potential in the field of concrete construction.

[0037] Microwaves are a type of high-frequency electromagnetic wave. When microwaves act on concrete, the polar molecules in the concrete (such as water molecules) will vibrate and rub against each other under the influence of the microwave electromagnetic field, generating heat. This heats the interior of the concrete, accelerates the cement hydration reaction, and achieves rapid curing.

[0038] Microwave heating utilizes electromagnetic radiation to create a uniform heating effect within the material, achieving rapid and even temperature rise inside the concrete. This accelerates the hydration process of the cement and effectively shortens the curing time. Furthermore, the energy transfer method during microwave curing differs from traditional heating methods, exhibiting greater selectivity and targeting, enabling better regulation of the hydration process in steel slag cement concrete and promoting its early strength improvement.

[0039] Compared with traditional curing methods, microwave curing not only heats up faster, but also heats concrete more evenly, ensuring that the cement hydration reaction proceeds fully and uniformly. This helps to improve key performance indicators of concrete such as strength and density, and has the advantages of high efficiency, high quality, energy saving and environmental protection, and flexibility and controllability.

[0040] Example 1

[0041] One aspect of the present invention provides a method for accelerating the curing of steel slag cement concrete based on three-level microwave control, comprising the following steps:

[0042] S1: Pour ordinary silicate cement, silica fume, and steel slag-based solid waste into a planetary mixer and dry mix for 1 minute to obtain mixture A;

[0043] S2: Add river sand, steel slag sand, limestone crushed stone, and steel slag coarse aggregate to mixture A and dry mix for 2 minutes to obtain mixture B;

[0044] S3: After mixing the polycarboxylate superplasticizer with water, slowly add it to the mixture B in two batches, and mix for 2 minutes at a temperature of 10-30℃ to obtain steel slag cement concrete mixture C.

[0045] S4: After pouring the steel slag cement concrete mixture C out of the mixer, it is evenly poured into the test mold and placed in the microwave curing equipment for initial microwave accelerated curing, intermediate microwave curing and later microwave curing in sequence.

[0046] The initial microwave accelerated curing time is 0.4 to 0.8 hours, the temperature is controlled between 45 and 60 degrees Celsius, the frequency used for the initial microwave curing is set to 1500 to 3000 MHz, the power is set to 1000 to 5000 W, and the heating rate is set to 10 to 20 degrees Celsius / hour.

[0047] The intermediate microwave curing time is 0.5 to 1.0 hours, the temperature is controlled between 50 and 75 degrees Celsius, the frequency used for intermediate microwave curing is set to 2450 to 5000 MHz, the power is set to 2000 to 5000 W, and the heating rate is set to 10 to 20 degrees Celsius / hour.

[0048] The subsequent microwave curing time is 0.5 to 1.0 hours, the temperature is controlled between 70 and 90 degrees Celsius, the frequency used for the subsequent microwave curing is set to 2450 to 5000 MHz, the power is set to 3000 to 5000 W, and the heating rate is set to 15 to 20 degrees Celsius / hour.

[0049] S5: After the later curing is completed, the concrete component can be removed from the microwave curing equipment for demolding, and then allowed to cool naturally to room temperature to complete the curing.

[0050] Furthermore, step S1 also includes weighing ordinary silicate cement, silica fume, steel slag-based solid waste, river sand, steel slag sand, limestone crushed stone, steel slag coarse aggregate, polycarboxylate superplasticizer and water by weight, wherein the steel slag-based solid waste includes steel slag powder, slag, raw ash, desulfurized gypsum and silica fume, and the fine aggregate includes river sand and steel slag sand.

[0051] The raw materials for preparing 100 parts of the steel slag cement concrete mix C include 10.2–11.8 parts of ordinary Portland cement, 9.7–11.3 parts of steel slag-based solid waste, 6.2–6.3 parts of water, 26.2–28.4 parts of fine aggregate, 19.9–24.5 parts of steel slag coarse aggregate, 18.8–22.9 parts of limestone crushed stone, 0.3–0.4 parts of polycarboxylate superplasticizer, and 1.0–1.4 parts of silica fume;

[0052] 100 parts of steel slag-based solid waste include 31.8–42.2 parts of steel slag powder, 19.1–25.9 parts of slag, 14.2–19.8 parts of raw ash, 13.5–17.5 parts of desulfurized gypsum, and 7.7–9.4 parts of silica fume;

[0053] 100 parts of fine aggregate includes 40-60 parts of river sand and 40-60 parts of steel slag sand.

[0054] Furthermore, the planetary mixer described in step S2 has a mixing speed of 60-100 r / min, and is cast into blocks after the mixing time is reached.

[0055] Further, the polycarboxylate superplasticizer mentioned in step S3 is composed of acrylic acid, methacrylic acid, maleic anhydride, polyoxyethylene allyl ester, polyoxyethylene methacrylate, polyoxyethylene acrylate, water, etc. The preparation process of the steel slag cement concrete mix C mentioned in step S3 is as follows: Figure 1 As shown.

[0056] Furthermore, the microwave curing equipment described in step S4 includes a microwave heating device for heating the steel slag in stages; a temperature sensor for monitoring the temperature of the steel slag in real time; and a control system for controlling the curing parameters.

[0057] The microwave heating device includes a microwave source, a waveguide, and a cavity;

[0058] The microwave source is capable of generating microwaves with a frequency of 1500-5000MHz and a power of 1000-5000W. The microwaves generated by the microwave source are transmitted to the cavity through the waveguide. The cavity is used to house steel slag cement concrete components.

[0059] The control system is used to precisely control the frequency, power, and curing time of the microwaves, as well as the temperature and heating rate inside the cavity, according to preset parameters.

[0060] Furthermore, in step S6, during the natural cooling stage, the time required for the steel slag to cool from the temperature at the end of the later heating phase to room temperature is 2 to 4 hours.

[0061] Example 2

[0062] The difference between this embodiment and Embodiment 1 is that:

[0063] The raw materials for preparing 100 parts of the steel slag cement concrete mix C in step S3 include, by weight, 11.2 parts of ordinary Portland cement, 10.2 parts of steel slag-based solid waste, 6.2 parts of water, 27.7 parts of fine aggregate, 21.6 parts of steel slag coarse aggregate, 21.7 parts of limestone crushed stone, 0.3 parts of polycarboxylate superplasticizer, and 1.1 parts of silica fume.

[0064] The 100 parts of the steel slag-based solid waste included 42.5 parts steel slag powder, 20.8 parts slag, 14.8 parts raw ash, 13.5 parts desulfurized gypsum, and 8.4 parts silica fume;

[0065] 100 parts of the fine aggregate mentioned above include 50 parts river sand and 50 parts steel slag sand;

[0066] The initial microwave curing described in step S4 adopts the continuous microwave heating curing method, with a frequency of 2450MHz and a power of 3000W for continuous microwave curing for 0.5h, the heating rate is controlled at 10℃ / h, and the temperature is controlled at 55~60℃.

[0067] After the initial curing is completed, the intermediate microwave curing is carried out. The intermediate microwave curing adopts the microwave gradient heating curing method, with microwaves of 2450MHz frequency and power of 2000W, 2500W, 3000W, 3500W and 4000W respectively curing for 0.2h, for a total duration of 1h. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 15℃ / h and the temperature controlled at 60~75℃.

[0068] After the mid-term curing is completed, the later microwave curing is carried out. The later microwave curing adopts the intermittent microwave heating curing method, with the curing frequency set at 2450MHz, the power at 5000W, and a cycle of 10 minutes. Each cycle heats for 5 minutes and stops for 5 minutes, with a total cycle duration of 1 hour. The heating rate is controlled at 15℃ / h, and the temperature is controlled at 75~90℃.

[0069] After the entire maintenance cycle is completed, allow it to cool naturally to room temperature to finish the maintenance process. See the maintenance procedure below. Figure 2 .

[0070] Example 3

[0071] The difference between this embodiment and Embodiment 2 is that:

[0072] The initial microwave curing in step S4 adopts the continuous microwave heating curing method, with a frequency of 3000Hz and a power of 5000W for continuous microwave curing for 0.4h, the heating rate is controlled at 20℃ / h, and the temperature is controlled at 47~55℃.

[0073] After the initial curing is completed, the intermediate microwave curing is carried out. The intermediate microwave curing adopts the microwave gradient heating curing method, with microwaves at a frequency of 4200MHz and power of 2500W, 3000W, 3500W, 4000W and 4500W respectively for 0.2h, for a total duration of 1h. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 20℃ / h and the temperature controlled at 55~75℃.

[0074] After the mid-term curing is completed, the later microwave curing will be carried out. The later microwave curing will continue to use the intermittent microwave heating curing method, with a frequency of 2450MHz, a power of 5000W, and a cycle of 10 minutes. Each cycle is heated for 5 minutes and stopped for 5 minutes, with a total cycle duration of 1 hour. The heating rate is controlled at 15℃ / h, and the temperature is controlled at 75~90℃.

[0075] After the entire maintenance cycle is completed, the system will naturally cool to room temperature to finish the maintenance process.

[0076] Example 4

[0077] The difference between this embodiment and Embodiment 2 is that:

[0078] The initial microwave curing described in step S4 adopts the continuous microwave heating curing method, with a frequency of 2450MHz and a power of 3000W for continuous microwave curing for 0.5h, the heating rate is controlled at 10℃ / h, and the temperature is controlled at 55~60℃.

[0079] After the initial curing is completed, the intermediate microwave curing is carried out. The intermediate microwave curing adopts the microwave gradient heating curing method, with microwaves of 5000MHz frequency and power of 3000W, 3500W, 4000W, 4500W and 5000W respectively for 0.1h, for a total duration of 0.5h. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 20℃ / h and the temperature controlled at 60~70℃.

[0080] After the mid-term curing is completed, the later microwave curing will be carried out. The later microwave curing will continue to use the intermittent microwave heating curing method, with a frequency of 2450MHz, a power of 5000W, and a cycle of 10 minutes. Each cycle is heated for 5 minutes and stopped for 5 minutes, with a total cycle duration of 1 hour. The heating rate is controlled at 15℃ / h, and the temperature is controlled at 70~85℃.

[0081] After the entire maintenance cycle is completed, the system will naturally cool to room temperature to finish the maintenance process.

[0082] Example 5

[0083] The difference between this embodiment and Embodiment 2 is that:

[0084] The initial microwave curing described in step S4 adopts the continuous microwave heating curing method, with a frequency of 2450MHz and a power of 1000W for continuous microwave curing for 0.8h, the heating rate is controlled at 10℃ / h, and the temperature is controlled at 52~60℃.

[0085] After the initial curing is completed, the intermediate microwave curing is carried out. The intermediate microwave curing adopts the microwave gradient heating curing method, with microwaves of 2450MHz frequency and power of 2000W, 2500W, 3000W, 3500W and 4000W respectively for 0.2h, for a total duration of 1h. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 15℃ / h and the temperature controlled at 60~75℃.

[0086] After the mid-term curing is completed, the later microwave curing is carried out. The later microwave curing adopts the intermittent microwave heating curing method, with the curing frequency set at 5000MHz and the power at 5000W. The cycle is 10 minutes, with each cycle heating for 5 minutes and stopping for 5 minutes. The total cycle duration is 0.5h, the heating rate is controlled at 20℃ / h, and the temperature is controlled at 75~85℃.

[0087] After the entire maintenance cycle is completed, the system will naturally cool to room temperature to finish the maintenance process.

[0088] Example 6

[0089] The difference between this embodiment and Embodiment 2 is that:

[0090] The initial microwave curing in step S4 adopts the continuous microwave heating curing method, with a frequency of 1500MHz and a power of 2000W for continuous microwave curing for 0.5h, the heating rate is controlled at 10℃ / h, and the temperature is controlled at 45~50℃.

[0091] After the initial curing is completed, the intermediate microwave curing is carried out. The intermediate microwave curing adopts the microwave gradient heating curing method, with microwaves of 4200MHz frequency and power of 2000W, 2500W, 3000W, 3500W and 4000W respectively for 0.2h, for a total duration of 1h. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 20℃ / h and the temperature controlled at 50~70℃.

[0092] After the mid-term curing is completed, the later microwave curing is carried out. The later microwave curing adopts the intermittent microwave heating curing method, with the curing frequency set at 5000MHz, the power at 3000W, and a cycle of 10 minutes. Each cycle heats for 5 minutes and stops for 5 minutes, with a total cycle duration of 1 hour. The heating rate is controlled at 15℃ / h, and the temperature is controlled at 70~85℃.

[0093] After the entire maintenance cycle is completed, the system will naturally cool to room temperature to finish the maintenance process.

[0094] Comparative Example

[0095] The difference between Comparative Example 1 and Example 2 is that microwave curing is not used in step S4, but a standard curing chamber is used for curing. The curing temperature is 20°C, the humidity is 95%, and the curing time is 72 hours.

[0096] The difference between Comparative Example 2 and Example 2 is that in step S4, microwave curing does not employ three-stage microwave curing, but rather two-stage microwave curing. The steel slag cement concrete mix C obtained in step S3 is placed in a microwave curing device for first-stage microwave curing. Under these first-stage microwave curing conditions, continuous microwave heating curing is used, with a frequency of 2450MHz and a power of 3000W for 0.5 hours, a heating rate controlled at 10℃ / h, and a temperature controlled at 50-55℃. After the initial curing is completed, a secondary microwave curing is performed. The secondary microwave curing adopts the microwave gradient heating curing method, with microwaves at a frequency of 2450MHz and powers of 2000W, 2500W, 3000W, 3500W, and 4000W respectively for 0.3 hours, for a total duration of 1.8 hours. The temperature is gradually increased in increments of 500W, with the heating rate controlled at 20℃ / h and the temperature controlled at 55~91℃. After the entire curing cycle is completed, the system is allowed to cool naturally to room temperature to complete the curing process.

[0097] The difference between Comparative Example 3 and Example 2 is that, in step S4, microwave curing does not employ three-stage microwave curing, but rather two-stage microwave curing. The steel slag cement concrete mix C obtained in step S3 is placed in a microwave curing device for first-stage microwave curing. Under these conditions, continuous microwave heating is used at a frequency of 2450MHz and a power of 3000W for 0.5 hours, with a heating rate controlled at 10℃ / h and a temperature controlled between 50 and 55℃. After the first-stage curing is completed, second-stage microwave curing is performed using intermittent microwave heating. The curing frequency is set to 3500MHz and the power to 5000W, with a 10-minute cycle. Each cycle consists of 5 minutes of heating followed by a 5-minute pause, for a total cycle duration of 2.5 hours. The temperature is controlled between 55 and 90℃. After the entire curing cycle is completed, the mixture is allowed to cool naturally to room temperature to complete the curing process.

[0098] The difference between Comparative Example 4 and Example 2 is that in step S4, three-stage microwave curing is not used, but only continuous microwave heating curing is used. The curing time is 3 hours, the frequency is set to 2450MHz, the power is set to 3000W, and the maximum curing temperature is maintained at 90℃.

[0099] The difference between Comparative Example 5 and Example 2 is that in step S4, the three-stage microwave curing method is not used, but only the intermittent microwave heating curing method is used. The curing time is 3 hours, with 10 minutes as a cycle. Each cycle is heated for 5 minutes and stopped for 5 minutes. The frequency is set to 3500MHz, the power is set to 4000W, and the maximum curing temperature is maintained at 90℃.

[0100] Following the methods described in Examples 2-6 and Comparative Examples 1-5, cubic specimens with dimensions of 100mm×100mm×100mm were prepared in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The 72h compressive strength and 72h splitting tensile strength of the cubic specimens were measured. The test results are shown in Table 1.

[0101] Table 1. Performance test results for each embodiment and comparative example.

[0102]

[0103] Examples 2-6 demonstrate the effects of different combinations of microwave curing parameters on the performance of steel slag cement concrete. Each example differs in microwave frequency, power, curing time, and heating rate, resulting in variations in the compressive strength and splitting tensile strength of the concrete. For example, Example 3 exhibits a compressive strength of 56.2 MPa and a splitting tensile strength of 4.3 MPa; Example 5 achieves a compressive strength of 56.8 MPa and a splitting tensile strength of 4.3 MPa, indicating that the concrete performs well under specific microwave curing conditions.

[0104] Comparative Example 1 used a standard curing chamber for curing. Although the curing time was relatively long (72h), the compressive strength of the concrete was only 37.2MPa and the splitting tensile strength was 3.0MPa, which was far lower than the performance indicators in the example. This shows that the microwave curing method has significant advantages in improving the early strength of concrete.

[0105] Comparative Examples 2-5 employed different microwave curing strategies, such as two-stage microwave curing, continuous microwave heating only, or intermittent microwave heating only. Compared to Example 2, their concrete performance also showed some differences. For example, the compressive strength of Comparative Example 2 was 47.6 MPa, and the splitting tensile strength was 3.9 MPa; while the compressive strength of Comparative Example 4 was 47.2 MPa, and the splitting tensile strength was 3.9 MPa. This indicates that the three-stage microwave curing method (initial, intermediate, and late stages) is more effective in improving overall performance.

[0106] By comparing the performance test results of the embodiments and comparative examples, it can be concluded that the three-stage microwave curing method can significantly improve the compressive strength and splitting tensile strength of steel slag cement concrete. A reasonable combination of microwave frequency, power, curing time, and heating rate is a key factor in achieving high-performance concrete. In practical engineering applications, appropriate microwave curing parameters should be selected based on the specific concrete mix proportions, raw material characteristics, and the requirements for the final performance.

[0107] The curing method of this invention can accelerate the hydration reaction rate compared with existing curing methods: by rapidly and uniformly heating concrete with microwaves, the hydration rate of cement is significantly increased, while traditional curing methods (such as watering and steam curing) often require a long time to achieve the same hydration effect. This allows microwave curing to promote strength development in a shorter time.

[0108] The curing method of this invention can improve the early strength of concrete compared with existing curing methods: microwave curing can enable concrete to reach a higher strength in a shorter time. The strength improvement of steel slag concrete under microwave curing is more significant than that of traditional curing methods, especially in the early stage of concrete, which can significantly shorten the curing time.

[0109] Compared with existing curing methods, the curing method of the present invention can save energy and time: microwave curing has high energy conversion efficiency and does not require a large supply of heat and water like traditional steam curing, which can save energy and reduce the dependence of traditional curing methods on equipment and materials, thereby improving production efficiency.

[0110] Compared with existing curing methods, the curing method of the present invention has stronger uniformity and controllability: microwave energy can be more evenly distributed in all parts of the concrete, thereby reducing temperature gradient and stress concentration, and avoiding cracks and uneven quality caused by excessive local temperature difference in traditional curing.

[0111] The maintenance method described in this invention is more environmentally friendly than existing maintenance methods: traditional maintenance methods may consume a lot of water and energy, while microwave maintenance reduces dependence on water and resources, helps to reduce the environmental burden, and meets the requirements of modern green and environmentally friendly buildings.

[0112] The implementation of this invention not only helps improve the performance of steel slag cement concrete, but also provides new technical support for sustainable development and the application of green building materials. In practical engineering, microwave accelerated curing of steel slag cement concrete can significantly improve construction efficiency and reduce costs, showing broad application prospects.

[0113] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for accelerating the curing of steel slag cement concrete based on three-stage microwave control, characterized in that: Includes the following steps: S1: Pour ordinary silicate cement, silica fume, and steel slag-based solid waste into a planetary mixer and dry mix for 1 minute to obtain mixture A; S2: Add river sand, steel slag sand, limestone crushed stone, and steel slag coarse aggregate to mixture A and dry mix for 2 minutes to obtain mixture B; S3: After mixing the polycarboxylate superplasticizer with water, slowly add it to the mixture B in two batches, and mix for 2 minutes at a temperature of 10-30℃ to obtain steel slag cement concrete mixture C. S4: After pouring the steel slag cement concrete mix C out of the mixer, it is evenly poured into the test mold and placed in the microwave curing equipment for initial microwave curing, intermediate microwave curing and final microwave curing in sequence. The initial microwave accelerated curing time in step S4 is 0.4 to 0.8 hours, the temperature is controlled between 45 and 60 degrees Celsius, the frequency used for the initial microwave curing is set to 1500 to 3000 MHz, the power is set to 1000 to 5000 W, and the heating rate is set to 10 to 20 degrees Celsius / h. The intermediate microwave curing time in step S4 is 0.5 to 1.0 h, the temperature is controlled between 50 and 75 °C, the frequency used for intermediate microwave curing is set to 2450 to 5000 MHz, the power is set to 2000 to 5000 W, and the heating rate is set to 10 to 20 °C / h. The subsequent microwave curing time is 0.5 to 1.0 hours, the temperature is controlled between 70 and 90 degrees Celsius, the frequency used for the subsequent microwave curing is set to 2450 to 5000 MHz, the power is set to 3000 to 5000 W, and the heating rate is set to 15 to 20 degrees Celsius / hour. S5: After the later curing is completed, the concrete component can be removed from the microwave curing equipment for demolding, and then allowed to cool naturally to room temperature to complete the curing.

2. The method for accelerated curing of steel slag cement concrete based on three-stage microwave control according to claim 1, characterized in that: The raw materials in step S1 consist of 10.2 to 11.8 parts by weight of ordinary Portland cement, 1.0 to 1.4 parts of silica fume, and 9.7 to 11.3 parts of steel slag-based solid waste.

3. The accelerated curing method for steel slag cement concrete based on three-stage microwave control according to claim 2, characterized in that: The steel slag-based solid waste mentioned in step S1 includes steel slag powder, slag, raw ash, desulfurization gypsum, and silica fume; 100 parts of steel slag-based solid waste include 31.8–42.2 parts of steel slag powder, 19.1–25.9 parts of slag, 14.2–19.8 parts of raw ash, 13.5–17.5 parts of desulfurized gypsum, and 7.7–9.4 parts of silica fume.

4. The accelerated curing method for steel slag cement concrete based on three-stage microwave control according to claim 2, characterized in that: In step S2, the raw material composition by weight is 26.2-28.4 parts fine aggregate, 18.8-22.9 parts limestone crushed stone, and 19.9-24.5 parts steel slag coarse aggregate.

5. The accelerated curing method for steel slag cement concrete based on three-stage microwave control according to claim 4, characterized in that: The fine aggregates mentioned in step S2 include river sand and steel slag sand; 100 parts of fine aggregate includes 40-60 parts of river sand and 40-60 parts of steel slag sand.

6. The accelerated curing method for steel slag cement concrete based on three-stage microwave control according to claim 5, characterized in that: In step S3, the raw material composition by weight is 0.3-0.4 parts of polycarboxylate superplasticizer and 6.2-6.3 parts of water.

7. A method for accelerating the curing of steel slag cement concrete based on three-stage microwave control according to any one of claims 1-6, characterized in that: The polycarboxylic acid high-efficiency water-reducing agent is composed of acrylic acid, methacrylic acid, maleic anhydride, polyoxyethylene allyl ester, polyoxyethylene methacrylate, polyoxyethylene acrylate, and water.

8. A method for accelerating the curing of steel slag cement concrete based on three-level microwave control according to any one of claims 1-6, characterized in that: In step S2, the stirring speed is 60-100 r / min, and the mixture is poured into blocks after the stirring time is reached.

9. A method for accelerating the curing of steel slag cement concrete based on three-stage microwave control according to any one of claims 1-6, characterized in that: The initial microwave curing described in step S4 adopts the continuous microwave heating curing method; The intermediate microwave curing adopts a microwave gradient heating curing method, with 500W as a gradient to achieve gradual temperature increase; The subsequent microwave curing continues to use intermittent microwave heating curing method, with 10 minutes as a cycle, each cycle heating for 5 minutes and stopping for 5 minutes, the total cycle length is 0.5 to 1 hour, the heating rate is controlled at 15 to 20℃ / h, and the temperature is controlled at 70 to 90℃.

10. A method for accelerated curing of steel slag cement concrete based on three-level microwave control according to any one of claims 1-6, characterized in that: The microwave curing equipment includes a microwave source, a waveguide, a cavity, and a control system. The microwave source can generate microwaves with a frequency of 1500-5000MHz and a power of 1000-5000W. The microwaves generated by the microwave source are transmitted to the cavity through the waveguide. The cavity is used to place steel slag cement concrete components. The control system can precisely control the frequency, power, and curing time of the microwaves, as well as the temperature and heating rate inside the cavity.

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