Panel concrete active crack prevention method

Abstract

The application discloses a kind of panel concrete active crack prevention methods, comprising: step 1: according to the compressive strength of panel concrete, expansion starting time, expansion amount design index requirement, using engineering raw materials to carry out concrete mix proportion optimization design of magnesium oxide expansive agent and conductive phase material, determine the key parameters of magnesium oxide expansive agent content, fly ash content, conductive phase material content and concrete test piece curing temperature influence concrete expansion performance;Step 2, along the direction parallel to panel, a pair of electrodes is arranged in the concrete, and the electrode is connected with voltage regulating device;Step 3, temperature sensor is arranged in the concrete;Step 4, voltage regulating device and temperature sensor are electrically connected with controller respectively, so as to regulate and control the internal temperature of panel concrete;The application improves the temperature distribution of concrete, so that it has the ability of active temperature control, and then regulates and controls the expansion history of panel concrete under real service environment, realizes the purpose of active crack prevention of panel concrete.

Description

Technical Field

[0001] This invention relates to the field of crack prevention technology for concrete panels, and in particular to an active crack prevention method for concrete panels. Background Technology

[0002] Faced concrete rockfill dams occupy an important position in dam construction due to their advantages such as simple construction and good seismic resistance. Among them, controlling cracks in the face concrete has always been a major challenge in the construction of face concrete dams. Controlling cracks in the face concrete from a material perspective, and minimizing cracking of the face from pouring to operation, is also a hot research topic in the hydraulic engineering field. At present, the main measures to control cracks in face concrete from a material perspective include mix proportion optimization, adding mineral admixtures such as fly ash or slag, using fiber toughening, and introducing expansion components. The main purpose is to reduce or compensate for concrete shrinkage and limit the occurrence or development of concrete cracks.

[0003] Lightly calcined magnesium oxide is the preferred expansion agent for hydraulic concrete. It has the characteristic of delayed micro-expansion, which can not only compensate for the shrinkage generated during the temperature drop of the dam concrete to reduce the tensile stress of the concrete and prevent cracks, but also simplify concrete temperature control measures, speed up construction progress and save project investment.

[0004] From a materials perspective, controlling concrete cracks by optimizing mix proportions or adding mineral admixtures, fibers, and magnesium oxide expansive agents to improve concrete crack resistance are all passive crack prevention technologies. In particular, the expansive properties of magnesium oxide are significantly affected by temperature. Low concrete temperatures hinder the hydration of magnesia in the expansive agent, making it difficult for it to exert its shrinkage compensation effect. High concrete temperatures accelerate the hydration of magnesia in the expansive agent, increasing the concrete expansion rate and deformation. If expansion is completed before the concrete cools down, it cannot compensate for the shrinkage caused by temperature drop. Therefore, due to temperature variations, the expansion performance of panel concrete with magnesium oxide expansive agents under actual construction and operation conditions often differs from the test results under standard indoor curing conditions, which is detrimental to the control and improvement of concrete crack resistance. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide an active crack prevention method for concrete panels, which improves the temperature distribution of concrete, enables it to have active temperature control capability, and thereby regulates the expansion process of concrete panels under real service conditions, thus achieving active crack prevention of concrete panels.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an active crack prevention method for concrete panels, which includes the following steps:

[0007] Step 1: Based on the design requirements of the panel concrete compressive strength, expansion initiation time, expansion amount, etc., the concrete mix design with magnesium oxide expansion agent and conductive phase material is optimized using engineering raw materials. The key parameters affecting the expansion performance of concrete, such as the dosage of magnesium oxide expansion agent, fly ash, conductive phase material, and curing temperature of concrete specimens, are determined.

[0008] Step 2: Place a pair of electrodes inside the concrete along a direction parallel to the panel, and connect the electrodes to the voltage regulating device.

[0009] Step 3: Install temperature sensors inside the concrete to monitor the concrete temperature; when the temperature drops suddenly, take temporary insulation measures on the concrete surface to prevent the heat generated by the conductive material from being lost and to help regulate the internal temperature of the concrete.

[0010] Step 4: Connect the voltage regulator and temperature sensor to the controller. The controller controls the voltage regulator to adjust the voltage on both sides of the concrete and converts electrical energy into heat energy, thereby regulating the internal temperature of the concrete panel.

[0011] Furthermore, step 1 specifically includes the following steps:

[0012] Step 1.1: Based on the performance requirements of hydraulic concrete for delayed expansion of magnesium oxide, select a magnesium oxide expansion agent with a reaction time of 240s±40s.

[0013] Step 1.2: Test the self-generated volume deformation of magnesium oxide concrete with different amounts of magnesium oxide expansive agent, different amounts of fly ash, and different curing temperatures. The magnesium oxide expansive agent dosage is 4%~6%, the fly ash dosage is 20%~70%, and the curing temperature is 20℃~40℃.

[0014] Step 1.3: The autogenous volume deformation of the above concrete specimens at the same age is accumulated and the average value is taken. The average value of the autogenous deformation is then used to perform regression analysis on the observed age to obtain the basic equation G0(t) of the autogenous volume deformation of magnesium oxide concrete.

[0015] Step 1.4: Assume that the influence coefficient of magnesium oxide expansive agent dosage on the autogenous volume deformation of concrete is K1 and the magnesium oxide expansive agent dosage is M; statistically analyze the average value of autogenous volume deformation of concrete under different magnesium oxide expansive agent dosage conditions, and obtain the calculation formula between the influence coefficient of magnesium oxide expansive agent dosage K1 and the magnesium oxide expansive agent dosage M through regression analysis.

[0016] Step 1.5: Assume that the influence coefficient of fly ash content on the autogenous volume deformation of concrete is K2 and the fly ash content is F; statistically analyze the average value of autogenous volume deformation of concrete under different fly ash content conditions, and obtain the calculation formula between the influence coefficient of fly ash content K2 and the fly ash content F through regression analysis.

[0017] Step 1.6: Assume the influence coefficient of curing temperature on the autogenous volume deformation of concrete is K3; statistically analyze the average value of autogenous volume deformation of concrete under different curing temperatures, select the autogenous volume deformation of concrete at a certain curing temperature as the calculation benchmark, that is, the influence coefficient of curing temperature on the autogenous volume deformation of concrete is 1.00, and obtain the influence coefficient K3 of curing temperature on the autogenous volume deformation of concrete by calculating the ratio of other curing temperatures to the autogenous volume deformation of concrete at this curing temperature;

[0018] Step 1.7: Considering the effects of magnesium oxide expansion agent dosage, fly ash, and temperature, the mathematical model for the self-generated volume deformation of concrete is G(t) = β × k1 × k2 × k3 × G0(t). Substituting G0(t), k1, k2, and k3 into the model G(t) = β × k1 × k2 × k3 × G0(t) and regressing the experimental data, the comprehensive correction coefficient β can be obtained.

[0019] Step 1.8: Based on the design requirements such as the compressive strength, expansion initiation time, and expansion amount of the panel concrete, comprehensively determine the dosage of magnesium oxide expansion agent, fly ash dosage, and curing temperature;

[0020] Step 1.9: The dosage of conductive phase material is 3% to 6% of the mass of cementitious material. The minimum dosage of conductive phase material is determined by test to ensure that the compressive strength is not lower than the design strength and the resistivity of concrete is 5 (Ω·m) to 10 (Ω·m).

[0021] Furthermore, in step 1.9, the conductive phase material is one or more of carbon black, carbon fiber, and metal fiber.

[0022] Furthermore, in step 2, the electrodes are made of mesh copper material, and the distance between the two electrodes is 200mm~300mm; the voltage adjustment device is an AC voltage regulator with a voltage adjustment range of 0V~220V, which adjusts the internal temperature change of the concrete by voltage regulation.

[0023] Furthermore, in step 3, the temperature sensor measures temperatures from -20°C to 60°C; the temporary insulation material for the concrete surface is one or more of polystyrene board, polyurethane, cotton quilt, and curing felt.

[0024] Furthermore, in step 4, the voltage is adjusted to ensure that the internal temperature of the concrete panel during actual construction is consistent with and stable with the curing temperature determined in step 1.

[0025] Beneficial effects of this invention:

[0026] 1. This invention proposes a concrete mix design method that incorporates magnesium oxide expansion agent and conductive phase material. By applying voltage to both sides of the concrete panel, electrical energy is converted into heat energy. By adjusting the voltage, the internal temperature of the concrete is controlled to maintain a stable target value, so that the expansion process of magnesium oxide concrete, such as the expansion initiation time and expansion amount, is not affected by the external ambient temperature. This allows the expansion efficiency of magnesium oxide to be fully utilized to compensate for concrete shrinkage, transforming the passive crack prevention of the concrete panel into active temperature-controlled crack prevention.

[0027] 2. The active crack prevention technology for concrete panels proposed in this invention can precisely control the expansion process of concrete panels under real environmental conditions according to design requirements, thereby improving the crack resistance of concrete, reducing temperature control measures, saving temperature control costs, and improving project efficiency.

[0028] 3. This invention combines a novel functional material, conductive phase material, with a magnesium oxide expansive agent and applies it to the construction of panel concrete. This transforms the passive crack prevention of panel concrete into active temperature-controlled crack prevention, improves the temperature distribution of concrete, and enables it to actively control temperature. This, in turn, regulates the expansion process of panel concrete under real service conditions, achieving the effect of active crack prevention. This not only improves the crack resistance and durability of panel concrete throughout its entire life cycle but also expands the engineering application field of conductive phase materials, showing broad market prospects. Attached Figure Description

[0029] Figure 1 This is a graph showing the change in autogenous volume deformation of concrete panels in a laboratory and construction site in a cold region over time. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] A method for actively preventing cracking in concrete panels includes the following steps:

[0032] Step 1: Based on the design requirements of the panel concrete compressive strength, expansion initiation time, expansion amount, etc., the concrete mix design with magnesium oxide expansion agent and conductive phase material is optimized using engineering raw materials. The key parameters affecting the expansion performance of concrete, such as the dosage of magnesium oxide expansion agent, fly ash, conductive phase material, and curing temperature of concrete specimens, are determined.

[0033] Step 2: Place a pair of electrodes inside the concrete along a direction parallel to the panel, and connect the electrodes to the voltage regulating device.

[0034] Step 3: Install temperature sensors inside the concrete to monitor the concrete temperature; when the temperature drops suddenly, take temporary insulation measures on the concrete surface to prevent the heat generated by the conductive material from being lost and to help regulate the internal temperature of the concrete.

[0035] Step 4: Connect the voltage regulator and temperature sensor to the controller. The controller controls the voltage regulator to adjust the voltage on both sides of the concrete and converts electrical energy into heat energy, thereby regulating the internal temperature of the concrete panel.

[0036] Furthermore, step 1 specifically includes the following steps:

[0037] Step 1.1: Based on the performance requirements of hydraulic concrete for delayed expansion of magnesium oxide, select a magnesium oxide expansion agent with a reaction time of 240s±40s.

[0038] Step 1.2: Test the self-generated volume deformation of magnesium oxide concrete with different amounts of magnesium oxide expansive agent, different amounts of fly ash, and different curing temperatures. The magnesium oxide expansive agent dosage is 4%~6%, the fly ash dosage is 20%~70%, and the curing temperature is 20℃~40℃.

[0039] Step 1.3: The autogenous volume deformation of the above concrete specimens at the same age is accumulated and the average value is taken. The average value of the autogenous deformation is then used to perform regression analysis on the observed age to obtain the basic equation G0(t) of the autogenous volume deformation of magnesium oxide concrete.

[0040] Step 1.4: Assume that the influence coefficient of magnesium oxide expansive agent dosage on the autogenous volume deformation of concrete is K1 and the magnesium oxide expansive agent dosage is M; statistically analyze the average value of autogenous volume deformation of concrete under different magnesium oxide expansive agent dosage conditions, and obtain the calculation formula between the influence coefficient of magnesium oxide expansive agent dosage K1 and the magnesium oxide expansive agent dosage M through regression analysis.

[0041] Step 1.5: Assume that the influence coefficient of fly ash content on the autogenous volume deformation of concrete is K2 and the fly ash content is F; statistically analyze the average value of autogenous volume deformation of concrete under different fly ash content conditions, and obtain the calculation formula between the influence coefficient of fly ash content K2 and the fly ash content F through regression analysis.

[0042] Step 1.6: Assume the influence coefficient of curing temperature on the autogenous volume deformation of concrete is K3; statistically analyze the average value of autogenous volume deformation of concrete under different curing temperatures, select the autogenous volume deformation of concrete at a certain curing temperature as the calculation benchmark, that is, the influence coefficient of curing temperature on the autogenous volume deformation of concrete is 1.00, and obtain the influence coefficient K3 of curing temperature on the autogenous volume deformation of concrete by calculating the ratio of other curing temperatures to the autogenous volume deformation of concrete at this curing temperature;

[0043] Step 1.7: Considering the effects of magnesium oxide expansion agent dosage, fly ash, and temperature, the mathematical model for the self-generated volume deformation of concrete is G(t) = β × k1 × k2 × k3 × G0(t). Substituting G0(t), k1, k2, and k3 into the model G(t) = β × k1 × k2 × k3 × G0(t) and regressing the experimental data, the comprehensive correction coefficient β can be obtained.

[0044] Step 1.8: Based on the design requirements such as the compressive strength, expansion initiation time, and expansion amount of the panel concrete, comprehensively determine the dosage of magnesium oxide expansion agent, fly ash dosage, and curing temperature;

[0045] Step 1.9: The dosage of conductive phase material is 3% to 6% of the mass of cementitious material. The minimum dosage of conductive phase material is determined by test to ensure that the compressive strength is not lower than the design strength and the resistivity of concrete is 5 (Ω·m) to 10 (Ω·m).

[0046] Furthermore, in step 1.9, the conductive phase material is one or more of carbon black, carbon fiber, and metal fiber.

[0047] Furthermore, in step 2, the electrodes are made of mesh copper material, and the distance between the two electrodes is 200mm~300mm; the voltage adjustment device is an AC voltage regulator with a voltage adjustment range of 0V~220V, which adjusts the internal temperature change of the concrete by voltage regulation.

[0048] Furthermore, in step 3, the temperature sensor measures temperatures from -20°C to 60°C; the temporary insulation material for the concrete surface is one or more of polystyrene board, polyurethane, cotton quilt, and curing felt.

[0049] Furthermore, in step 4, the voltage is adjusted to ensure that the internal temperature of the concrete panel during actual construction is consistent with and stable with the curing temperature determined in step 1.

[0050] In this invention, by applying voltage to both sides of the concrete panel, the conductive phase material generates an electrothermal effect, converting electrical energy into heat energy, promoting an increase in the internal temperature of the concrete, and protecting the concrete panel from the effects of ambient temperature such as diurnal temperature differences or cold waves. By flexibly adjusting the voltage, the internal temperature of the concrete panel during actual construction is made consistent with and stable with the curing temperature determined in step 1. Key crack-resistant parameters such as the onset time and amount of concrete expansion meet design requirements, achieving active crack prevention and control of the concrete panel under real service environment conditions.

[0051] Example 1:

[0052] The design parameters for the concrete face of a rockfill dam in a cold region are C30W12F200. The concrete is required to have a self-generated volumetric deformation ≥0με within 5-7 days after pouring, a self-generated volumetric deformation ≥30με at 28 days, and a maximum self-generated volumetric deformation ≤60με.

[0053] Step 1: The concrete mix design was optimized using the raw materials required for this project, including 42.5 ordinary Portland cement, Grade II fly ash, sandstone aggregate, magnesium oxide expansion agent, and carbon black. The specific method is as follows:

[0054] (1) Based on the performance requirements of hydraulic concrete for delayed expansion of magnesium oxide, a magnesium oxide expansion agent with a reaction time of 250s was selected;

[0055] (2) Select magnesium oxide expansion agent dosage of 4%, 5% and 6%, fly ash dosage of 20% and 25%, and curing temperature of 20℃, 30℃ and 40℃; test the autogenous volume deformation of magnesium oxide concrete with different magnesium oxide expansion agent dosage, different fly ash dosage and different curing temperature.

[0056] (3) The autogenous volumetric deformations of the above specimens at the same age were summed and averaged. A regression analysis was then performed on the average autogenous deformation against the observed age to obtain the basic equation for the autogenous volumetric deformation of magnesium oxide concrete: G0(t) = 12.99ln(t) - 17.305

[0057] (4) Assume the influence coefficient of magnesium oxide expansive agent dosage on the autogenous volume deformation of concrete is K1, and the magnesium oxide expansive agent dosage is M. Statistical analysis was performed on the average autogenous volume deformation of concrete under the condition of 4%~6% magnesium oxide expansive agent dosage. Through regression analysis, the calculation formula between the influence coefficient of magnesium oxide expansive agent dosage K1 and the magnesium oxide expansive agent dosage M is obtained as follows: k1=906.22M-13.141

[0058] (5) Assume the influence coefficient of fly ash content on the autogenous volume deformation of concrete is K2, and the fly ash content is F. Statistically analyze the average autogenous volume deformation of concrete under 20% and 25% fly ash content conditions. Through regression analysis, the calculation formula between the influence coefficient of fly ash content K2 and the fly ash content F is obtained as: k2 = 36F 2 -87.63F +51.161

[0059] (6) Assume that the influence coefficient of curing temperature on the autogenous volume deformation of concrete is K3. Statistically analyze the average value of autogenous volume deformation of concrete under curing temperatures of 20℃, 30℃ and 40℃. Select the autogenous volume deformation of concrete under the condition of 30℃ as the calculation benchmark, that is, the influence coefficient of curing temperature on the autogenous volume deformation of concrete is 1.00. By calculating the ratio of the autogenous volume deformation of concrete under curing temperatures of 20℃, 40℃ and 30℃, the influence coefficient K3 of curing temperature on the autogenous volume deformation of concrete is obtained, as detailed in Table 1.

[0060] Table 1 Temperature Influence Coefficient k3

[0061] Maintenance temperature T 20℃ 30℃ 40℃ <![CDATA[k3]]> 0.37 1.00 1.52

[0062] (7) The mathematical model for the self-generated volume deformation of concrete considering the effects of magnesium oxide expansion agent dosage, fly ash effect and temperature effect is G(t)=β×k1×k2×k3×G0(t). Substituting G0(t), k1, k2 and k3 into the model G(t)=β×k1×k2×k3×G0(t) and regressing the experimental data, the comprehensive correction coefficient β is 0.00115.

[0063] (8) Based on the mathematical model, the dosage of magnesium oxide expansion agent is determined to be 5%, the dosage of fly ash is 25%, and the curing temperature is 30℃; the compressive strength of the concrete at 28 days in the laboratory is 40.3 MPa, and the curve of autogenous volume deformation with age is shown in the figure. Figure 1 The autogenous volumetric deformation of the concrete at 5 days was 1.0 με, the autogenous volumetric deformation of the concrete at 28 days was 38.4 με, and the maximum autogenous volumetric deformation was 59.7 με, which meets the design requirements.

[0064] (9) Using carbon black as the conductive phase material, compressive strength and resistivity tests were conducted at dosages of 3%, 4%, and 5%. The tests determined that with a carbon black dosage of 4%, the concrete compressive strength was 38.4 MPa and the resistivity was 6.2 (Ω·m), which met the design requirements.

[0065] Step 2: Along the direction parallel to the panel, lay brass mesh electrodes inside the concrete, with a spacing of 200mm between the two electrodes, and connect them to the STG-500W AC voltage regulator.

[0066] Step 3: Install JDC-2 temperature sensors inside the concrete, with a sensor spacing of 1.0m.

[0067] Step 4: Connect the STG-500W AC voltage regulator and the JDC-2 temperature sensor to the control panel. The output voltage is dynamically adjusted to keep the internal temperature of the concrete stable at 30℃, and the temperature deviation is controlled to be <1℃, depending on the ambient temperature and the temperature rise of the concrete hydration.

[0068] Strain sensors embedded in the concrete panel monitored changes in concrete deformation at the construction site as the curing age progressed. Figure 1 As shown, the concrete panel began to expand after 5 days, with an autogenous expansion of 38.9 με after 28 days and a maximum autogenous volume deformation of 59.0 με, which meets the design requirements. The expansion deformation stabilized after 50 days, and the laboratory test data and field monitoring data of the autogenous volume deformation of the concrete are basically consistent.

[0069] Using the active crack-prevention materials and technology proposed in Example 1, no visible cracks were found on the surface of the concrete panel during construction and operation.

[0070] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for actively preventing cracking in concrete panels, characterized in that: It includes the following steps: Step 1: Based on the design requirements of the compressive strength, expansion initiation time, and expansion amount of the panel concrete, the concrete mix design with magnesium oxide expansion agent and conductive phase material is optimized using engineering raw materials. The key parameters affecting the expansion performance of concrete are determined by the dosage of magnesium oxide expansion agent, fly ash, conductive phase material, and the curing temperature of concrete specimens. Step 2: Place a pair of electrodes inside the concrete along a direction parallel to the panel, and connect the electrodes to the voltage regulating device. Step 3: Install temperature sensors inside the concrete to monitor the concrete temperature; when the temperature drops suddenly, take temporary insulation measures on the concrete surface to prevent the heat generated by the conductive material from being lost and to help regulate the internal temperature of the concrete. Step 4: Connect the voltage regulator and temperature sensor to the controller. The controller controls the voltage regulator to adjust the voltage on both sides of the concrete and converts electrical energy into heat energy, thereby regulating the internal temperature of the concrete panel. In step 4, the voltage is adjusted to ensure that the internal temperature of the concrete panel during actual construction is consistent with and stable with the curing temperature determined in step 1.

2. The method of claim 1, wherein: Step 1 specifically includes the following steps: Step 1.1: Based on the performance requirements of hydraulic concrete for delayed expansion of magnesium oxide, select a magnesium oxide expansion agent with a reaction time of 240s±40s. Step 1.2: Test the self-generated volume deformation of magnesium oxide concrete with different amounts of magnesium oxide expansive agent, different amounts of fly ash, and different curing temperatures. The magnesium oxide expansive agent dosage is 4%~6%, the fly ash dosage is 20%~70%, and the curing temperature is 20℃~40℃. Step 1.3: The autogenous volume deformation of the above concrete specimens at the same age is accumulated and the average value is taken. The average value of the autogenous deformation is then used to perform regression analysis on the observed age to obtain the basic equation G0(t) of the autogenous volume deformation of magnesium oxide concrete. Step 1.4: Assume that the influence coefficient of magnesium oxide expansive agent dosage on the autogenous volume deformation of concrete is K1 and the magnesium oxide expansive agent dosage is M; statistically analyze the average value of autogenous volume deformation of concrete under different magnesium oxide expansive agent dosage conditions, and obtain the calculation formula between the influence coefficient of magnesium oxide expansive agent dosage K1 and the magnesium oxide expansive agent dosage M through regression analysis. Step 1.5: Assume that the influence coefficient of fly ash content on the autogenous volume deformation of concrete is K2 and the fly ash content is F; statistically analyze the average value of autogenous volume deformation of concrete under different fly ash content conditions, and obtain the calculation formula between the influence coefficient of fly ash content K2 and the fly ash content F through regression analysis. Step 1.6: Assume the influence coefficient of curing temperature on the autogenous volume deformation of concrete is K3; statistically analyze the average value of autogenous volume deformation of concrete under different curing temperatures, select the autogenous volume deformation of concrete at a certain curing temperature as the calculation benchmark, that is, the influence coefficient of curing temperature on the autogenous volume deformation of concrete is 1.00, and obtain the influence coefficient K3 of curing temperature on the autogenous volume deformation of concrete by calculating the ratio of other curing temperatures to the autogenous volume deformation of concrete at this curing temperature; Step 1.7: Considering the effects of magnesium oxide expansion agent dosage, fly ash, and temperature, the mathematical model for the self-generated volume deformation of concrete is G(t) = β × k1 × k2 × k3 × G0(t). Substituting G0(t), k1, k2, and k3 into the model G(t) = β × k1 × k2 × k3 × G0(t) and regressing the experimental data, the comprehensive correction coefficient β can be obtained. Step 1.8: Based on the design requirements of the compressive strength, expansion initiation time, and expansion amount of the panel concrete, comprehensively determine the dosage of magnesium oxide expansion agent, fly ash dosage, and curing temperature; Step 1.9: The dosage of conductive phase material is 3% to 6% of the mass of cementitious material. The minimum dosage of conductive phase material is determined by test to ensure that the compressive strength is not lower than the design strength and the resistivity of concrete is 5Ω·m to 10Ω·m.

3. The method of claim 2, wherein: In step 1.9, the conductive phase material is one or more of carbon black, carbon fiber, and metal fiber.

4. The active crack prevention method for concrete panels according to claim 1, characterized in that: In step 2, the electrodes are made of mesh copper material, and the distance between the two electrodes is 200mm~300mm; the voltage adjustment device is an AC voltage regulator with a voltage adjustment range of 0V~220V, which adjusts the internal temperature change of the concrete by adjusting the voltage.

5. The method of claim 1, wherein: In step 3, the temperature sensor measures temperatures from -20℃ to 60℃; the temporary insulation material for the concrete surface is one or more of polystyrene board, polyurethane, cotton quilt, and curing felt.

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