Mixed rock granite rock aggregate concrete and preparation method thereof

Abstract

The invention discloses mixed lithiated granite rock aggregate concrete and a preparation method thereof, and the mixed lithiated granite rock aggregate concrete comprises the following components in percentage by mass: 65-75% of mixed lithiated granite aggregate comprising coarse aggregate with the particle size of 5-10 mm and fine aggregate with the particle size of 2.36-4.75 mm in a mass ratio of 3: 1-4: 1; the cementing material is composed of Portland cement and mineral micro powder, and the mixing amount of the mineral micro powder accounts for 15%-25% of the total mass of the cementing material; 0.5%-1.5% of an additive, wherein the additive comprises a water reducing agent and an alkali inhibitor; the ratio of the water to the binder is 0.35 to 0.45; the aggregate is subjected to pre-wetting treatment, the pre-wetting time is 12-24 hours, and the surface moisture content is controlled to be 3%-5%. By designing the mass ratio of coarse and fine particles of the mixed rock granite aggregate, improving the interface structure through pre-wetting treatment, accurately controlling the mixing amount of mineral micro powder of a cementing material, optimizing the water-binder ratio and introducing a composite admixture system, the strength and durability of the concrete are synergistically improved, and the problems that traditional aggregate is prone to strength attenuation and insufficient in durability are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering materials, in particular to a mixed-migmatized granite aggregate concrete and a preparation method thereof. BACKGROUND

[0002] In the existing concrete technology, the granite aggregate has large chemical composition fluctuation and high alkali activity risk, resulting in insufficient durability of the concrete.

[0003] Traditional researches mainly focus on single rock aggregate, and lack of systematic analysis on the engineering properties of mixed-migmatized granite aggregate under complex environment.

[0004] Especially in infrastructure construction such as bridges, the demand for aggregate is large, and the mixed-migmatized granite is easy to cause damage to the interface transition zone due to temperature alternation and humidity cycle when used as aggregate, resulting in attenuation of the strength of the concrete.

[0005] The existing technology does not establish the quantitative correlation between the particle size of the aggregate, the mineral powder content and the macro-mechanical behavior of the concrete, and the measures to inhibit the reaction of alkali and silicon mainly rely on empirical formula, lacking multi-scale analysis support, therefore, the present application provides a mixed-migmatized granite aggregate concrete and a preparation method thereof. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a mixed-migmatized granite aggregate concrete and a preparation method thereof to solve the problems in the background art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a mixed-migmatized granite aggregate concrete, which is composed of the following components in mass percentage: Mixed-migmatized granite aggregate: 65% to 75%, including coarse aggregate with a particle size of 5 to 10 mm and fine aggregate with a particle size of 2.36 to 4.75 mm, and the mass ratio is 3:1 to 4:1; Cementitious material: 20% to 28%, composed of Portland cement and mineral powder, wherein the mineral powder content is 15% to 25% of the total mass of the cementitious material; Admixtures: 0.5% to 1.5%, including water reducing agent and alkali inhibitor; Water: the balance, and the water-binder ratio is 0.35 to 0.45; The aggregate is pre-wetted, the pre-wetting time is 12 to 24 hours, and the surface water content is controlled at 3% to 5%; In the aggregate pretreatment stage, the vacuum saturation method is adopted, the saturation pressure is controlled at-0.08 to-0.1 MPa, the saturation time is adjusted according to the aggregate particle size, and the surface water content is accurately controlled at 3% to 5%, at the same time, the laser particle size analyzer is used to optimize the aggregate particle size distribution, the fineness modulus of the fine aggregate is ensured to be 2.6 to 3.0, and the void ratio of the coarse aggregate is ≤40%, so as to improve the compactness and strength of the concrete; The mixed granitization granite aggregate concrete significantly improves the comprehensive performance of the concrete by accurately controlling the aggregate ratio, the composition of cementitious materials and the dosage of admixtures, combining with the optimized pre-wetting treatment process. The reasonable aggregate ratio ensures the compactness and strength of the concrete, the addition of mineral micro-powder in the cementitious material improves the fluidity and later strength development of the cement paste, the use of admixtures effectively reduces the water-binder ratio, improves the workability, and the addition of alkali inhibitor effectively inhibits the alkali-aggregate reaction, prolongs the service life of the concrete. The pre-wetting treatment ensures the good adhesion of the aggregate and the cement paste, further improves the durability and crack resistance of the concrete, and is suitable for engineering construction in various complex environments.

[0008] Preferably, the SiO2 content in the mixed granitization granite aggregate is ≥70%, and the alkali activity expansion rate is ≤0.06%; To ensure that the SiO2 content in the mixed granitization granite aggregate is ≥70% and the alkali activity expansion rate is ≤0.06%, the chemical composition of the rock mass is analyzed during the aggregate mining stage, and the mine area with high SiO2 content is preferentially selected. In the processing process, the laser particle size analyzer is used to monitor the aggregate particle size distribution, so as to ensure that the fineness modulus of the fine aggregate is between 2.6 and 3.0, and the void ratio of the coarse aggregate is ≤40%. At the same time, the alkali activity expansion rate of the aggregate is detected by rapid mortar bar method and other test methods, and the aggregate that does not meet the requirements is removed or taken inhibition measures, such as adding lithium salt alkali inhibitor. The provision that the SiO2 content in the mixed granitization granite aggregate is ≥70% and the alkali activity expansion rate is ≤0.06% significantly improves the comprehensive performance of the concrete. High SiO2 content enhances the hardness and durability of the aggregate, which helps to improve the compressive strength and wear resistance of the concrete. Low alkali activity expansion rate effectively prevents the cracking and damage of the concrete caused by alkali-aggregate reaction, prolongs the service life of the structure. These characteristics enable the concrete to maintain good workability and durability in harsh environments, and are suitable for various engineering structures that require high strength and durability, such as bridges, tunnels and high-rise buildings.

[0009] Preferably, the mineral micro-powder is a mixture of fly ash and slag powder with a mass ratio of 1:1 to 2:1, and a particle size distribution of D50 ≤10 μm. The fly ash and the slag powder are weighed according to a preset mass ratio of 1:1 to 2:1, then are put into a mixing device, the device is started to mix uniformly under low speed rotation, the mixing state is continuously monitored during the process to ensure that the two kinds of micro-powders are fully fused, and the mixing time is not less than 5 minutes to guarantee the compounding quality, and finally the mineral micro-powder satisfying a particle size distribution of D50≤10 μm is obtained; The fly ash and the slag powder can play their respective advantages in the compounding process, through reasonable proportioning, the performance of the cementitious material can be optimized, the overall strength and durability of the concrete can be improved, on the other hand, the particle size distribution of D50≤10 μm can make the mineral micro-powder better fill the voids between the cement particles, improve the compactness of the concrete, reduce internal defects, and then improve the impermeability and other performances of the concrete, thereby providing a strong guarantee for preparing high-quality mixed granitization granite aggregate concrete.

[0010] Preferably, the water reducing agent is a polycarboxylate-based high-efficiency water reducing agent, the dosage of the polycarboxylate-based high-efficiency water reducing agent is 0.8% to 1.2% of the mass of the cementitious material; the alkali inhibitor is a lithium salt compound, and the dosage of the lithium salt compound is 0.2% to 0.5% of the mass of the cementitious material. The polycarboxylate-based high-efficiency water reducing agent should be dissolved in the mixing water in advance, and then is added into the stirrer after being stirred uniformly; the lithium salt alkali inhibitor is also dissolved in the mixing water, and forms an additive solution together with the water reducing agent, and is added synchronously during the mixing of the concrete to ensure that it is uniformly dispersed in the concrete. The dosage of the polycarboxylate-based high-efficiency water reducing agent is controlled to be 0.8% to 1.2% of the mass of the cementitious material, which can effectively reduce the water-cement ratio of the concrete, improve the workability, reduce the water consumption, and enhance the strength and durability of the concrete; the dosage of the lithium salt alkali inhibitor is 0.2% to 0.5% of the mass of the cementitious material, which can effectively inhibit the alkali-aggregate reaction in the concrete, prevent the concrete from cracking due to the alkali-aggregate reaction, and prolong the service life of the concrete; the combination of the two can improve the workability and mechanical properties of the concrete, and enhance the durability of the concrete, thereby ensuring the long-term stability of the concrete in complex environments.

[0011] Preferably, the slump of the concrete mixture is controlled to be 160 to 200 mm, and the spread is ≥450 mm. The slump of the concrete mixture is controlled to be 160 to 200 mm, and the spread is ≥450 mm by precisely controlling the dosage of the water reducing agent (0.8% to 1.2% of the mass of the cementitious material) and the temperature of the mixing water (15 to 25℃). By precisely controlling the proportioning of aggregate, cementitious material, admixture and water, the high strength and durability of the concrete are ensured, especially the pre-wetting treatment of aggregate and the compounding use of mineral micro-powder, which effectively improves the compactness and crack resistance of the concrete. In the preparation process, the steps of pre-treatment of aggregate, mixing of cementitious material, dissolution of admixture and mixing of concrete are carried out step by step, which ensures the stability and reliability of the quality of the concrete. Finally, through strict performance verification and uniformity detection, the application requirements of the concrete under complex engineering environment are met.

[0012] A preparation method of a mixed-migmatized granite aggregate concrete, based on the mixed-migmatized granite aggregate concrete described above, comprising the following steps: Step one, pre-treatment of aggregate: The mixed-migmatized granite aggregate is screened and cleaned to remove surface impurities, and then vacuum water-saturated treatment is performed; Step two, mixing of cementitious material: The Portland cement and mineral micro-powder are mixed in proportion and dry-mixed uniformly; Step three, dissolution of admixture: The water-reducing agent and alkali inhibitor are dissolved in the mixing water and stirred uniformly; Step four, mixing of concrete: The pre-wetted aggregate and cementitious material are added to the mixer in turn, low-speed stirring is performed for 30s, then the mixing water containing admixture is added, and high-speed stirring is performed for 120s; Step five, molding and curing: The mixture is poured into a mold, vibrated to form, then covered with a moisture-retaining film, and cured for 28 days; Step six, performance verification: The micro-mechanical properties of the interface transition zone between the aggregate and the cement paste are verified by a multi-scale analysis method; Step seven, uniformity detection: The uniformity of the aggregate distribution is verified by an image analysis method; The screened and cleaned mixed-migmatized granite aggregate is placed in a vacuum water-saturated device, the water-saturated pressure is set to -0.08 to -0.1 MPa, and the water-saturated time is adjusted according to the particle size of the aggregate, i.e. the larger the particle size, the longer the time, to ensure that the aggregate is fully water-absorbed to a surface moisture content of 3% to 5%, which ensures that the aggregate is uniformly water-absorbed during the mixing of the concrete, avoiding performance instability caused by subsequent water migration; The pre-treatment of the aggregate removes impurities and optimizes the water-absorption performance, improving the workability and durability of the concrete; the precise proportioning of the cementitious material and the admixture effectively enhances the strength and crack resistance of the concrete; the strict control of the mixing and curing processes ensures the uniformity and compactness of the internal structure of the concrete; in addition, the introduction of the performance verification and uniformity detection steps further ensures the quality reliability of the concrete products, meeting the high-standard engineering requirements.

[0013] Preferably, the saturated water pressure of the vacuum saturated treatment in step one is -0.08 to -0.1 MPa, the saturated water time is positively correlated with the aggregate particle size, and the aggregate particle size distribution is optimized by a laser particle size analyzer to ensure that the fineness modulus of fine aggregate is 2.6 to 3.0 and the void ratio of coarse aggregate is ≤40%; In the vacuum saturated treatment step, the mixed granitization granite aggregate is placed in a special vacuum saturated equipment, the vacuum pump is started after sealing, the system pressure is adjusted to the range of -0.08 to -0.1 MPa, and the time is started to be counted. The saturated water time is determined according to the maximum particle size of the aggregate, such as 2 hours for 5 mm particle size aggregate and 4 hours for 10 mm particle size aggregate to ensure that the water is fully penetrated. At the same time, the laser particle size analyzer is used to monitor the aggregate particle size distribution, and the fineness modulus of fine aggregate is adjusted to 2.6 to 3.0 and the void ratio of coarse aggregate is ≤40% through screening to ensure that the aggregate grading is reasonable; By precisely controlling the saturated water pressure and time, the aggregate is fully water-absorbed, the water quantity for mixing is reduced, the concrete density is improved, the application of the laser particle size analyzer realizes the precise control of the aggregate particle size distribution, the optimization of the fineness modulus of fine aggregate and the void ratio of coarse aggregate, the interlocking effect between aggregates is enhanced, and the overall strength and durability of the concrete are improved. This scheme not only simplifies the construction process, but also ensures the stability and reliability of the concrete quality, and provides high-performance building materials for building engineering.

[0014] Preferably, the stirring speed in step four is controlled at low speed 60 to 80 rpm and high speed 120 to 150 rpm, and the mixing water temperature is controlled at 15 to 25°C; During the stirring process, a stirrer with automatic speed regulation function is used to realize the switching of low speed 60 to 80 rpm and high speed 120 to 150 rpm through a preset program; at the same time, a temperature control device is installed in the mixing water storage tank to monitor and adjust the water temperature in real time, so that the mixing water temperature is stably controlled in the range of 15 to 25°C to ensure the quality of the concrete mixing; The appropriate stirring speed ensures the uniform mixing of the aggregate, cementitious materials and admixtures, reduces the segregation phenomenon, improves the compactness and strength of the concrete, and at the same time, the stable mixing water temperature avoids the change of the concrete performance caused by temperature fluctuation, ensuring the stability and durability of the concrete during the hardening process. These measures work together to make the prepared concrete have excellent mechanical properties and durability to meet the needs of various engineering requirements.

[0015] Preferably, the vibration forming frequency in step five is 50 to 60 Hz, the amplitude is 1 to 2 mm, the curing environment humidity is ≥95%, and the temperature is 20±2°C; During the vibration forming process, a high-frequency low-amplitude vibrator is used to ensure that the bubbles inside the concrete are effectively discharged, avoiding the formation of honeycomb and pitted surfaces; the curing environment humidity is maintained through an automatic humidification system, and the temperature is accurately adjusted by a constant temperature control system to ensure that the concrete hardens under optimal conditions and improves the final performance; The high-frequency low-amplitude vibration ensures the compactness of the concrete, effectively reduces internal defects, improves the overall strength and durability of the structure, and at the same time, the high-humidity and constant-temperature curing environment promotes the full progress of the cement hydration reaction, accelerates the strength development, and helps to reduce stress cracks caused by temperature changes, thereby prolonging the service life of the concrete structure. Under the joint action of these measures, the high quality and long-term stability of the concrete product are ensured.

[0016] Preferably, during the concrete mixing process of step four, the uniformity of the mixture is monitored in real time, online near-infrared spectrum analysis technology is used, and spectrum data of the mixture is collected every 30 seconds. When the fluctuation range of the characteristic peak intensity of each component in the spectrum data of the mixture is within ±3%, it is determined that the uniformity of the mixture meets the requirements, so as to ensure that each component of the concrete is fully mixed, and the stability of the performance of the concrete is ensured.

[0017] In summary, compared with the prior art, the present application provides a mixed metamorphic granite aggregate concrete and a preparation method thereof, which has the following beneficial effects: The present application effectively improves the interface transition zone structure of the aggregate and the cementitious material by designing the mass ratio of coarse and fine particles in the mixed metamorphic granite aggregate to be 3:1-4:1 and combining with the pre-wetting treatment technology, significantly reduces the interface damage risk caused by the complex mineral composition, and solves the core problem that the traditional mixed metamorphic granite aggregate easily leads to concrete strength attenuation under temperature alternation and humidity cycle environment. At the same time, by accurately controlling the mineral powder content in the cementitious material to be 15%-25% of the total mass of the cementitious material, and combining with the optimization design of the water-binder ratio of 0.35-0.45, the quantitative correlation between the aggregate particle size, the mineral powder content and the macroscopic mechanical behavior of the concrete is established, breaking through the limitations of the existing technology relying on empirical formula, and realizing the synergistic improvement of the compressive strength, the flexural strength and the durability of the concrete. In addition, by introducing a composite admixture system containing a water reducing agent and an alkali inhibitor, and combining with the systematic optimization of the component ratio, the occurrence of alkali and silicon reaction is systematically inhibited, the chemical stability of the concrete in complex environment is significantly improved, and the problem of insufficient durability caused by the large fluctuation of chemical composition and high alkali activity risk of the granite aggregate is solved. The technical scheme provides a high-adaptability and low-maintenance-cost aggregate solution for bridges and other infrastructure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1This is a diagram of the steps for preparing the mixed rock granite rock aggregate concrete of the invention. DETAILED DESCRIPTION

[0019] Example 1 The present invention provides a technical solution, a mixed rock granite rock aggregate concrete, It is composed of the following components in percentage by mass: Migmatized granite aggregate: 70% (52.5% coarse aggregate, 17.5% fine aggregate, mass ratio 3:1) Cementitious materials: 25% (20% Portland cement, 5% mineral powder, with the fly ash and slag powder in the mineral powder in a mass ratio of 1:1) Admixture: 1% (polycarboxylic acid-based high-efficiency water reducer 0.8%, lithium salt alkali inhibitor 0.2%) Water: balance, water-to-binder ratio 0.4 Aggregate pre-wetting treatment: pre-wetting time 18 hours, surface moisture content 4% Preparation method: 1. Aggregate pretreatment: screening, cleaning, vacuum saturation treatment (-0.09MPa, saturation time adjusted according to particle size).

[0020] 2. Mixing of cementitious materials: dry mix silicate cement and mineral powder evenly.

[0021] 3. Dissolution of admixtures: Water reducer and alkali inhibitor are dissolved in mixing water.

[0022] 4. Concrete mixing: Mix at low speed for 30 seconds, then at high speed for 120 seconds. The mixing water temperature should be 20℃.

[0023] 5. Molding and curing: Vibration molding (55Hz, 1.5mm amplitude), covering with moisturizing film, curing for 28 days (humidity ≥ 95%, temperature 20±2℃).

[0024] 6. Performance verification and uniformity testing; Example 2 The difference between this embodiment and the first embodiment is that: Material composition by weight: Migmatized granite aggregate: 65% (coarse aggregate 48.75%, fine aggregate 16.25%, mass ratio 3:1) Cementitious materials: 28% (22.4% Portland cement, 5.6% mineral powder, with the mass ratio of fly ash to slag powder in the mineral powder being 1.5:1) Admixture: 1.2% (polycarboxylic acid-based high-efficiency water reducer 1%, lithium salt alkali inhibitor 0.2%) Water: balance, water-to-binder ratio 0.38 Aggregate pre-wetting treatment: pre-wetting time 12 hours, surface moisture content 3% Preparation method: same as example one, but adjust the stirring speed (low speed 70 rpm, high speed 130 rpm); Example three The difference between this example and example one and example two is: Material component weight percentage: mixed granitization granite aggregate: 75% (coarse aggregate 56.25%, fine aggregate 18.75%, mass ratio 3:1) Cementitious material: 20% (portland cement 16%, mineral micro powder 4%, mass ratio of fly ash to slag powder in mineral micro powder 2:1) Admixture: 0.8% (polycarboxylic acid high efficiency water reducing agent 0.64%, lithium salt alkali inhibitor 0.16%) Water: the rest, water-binder ratio 0.42 Pre-wetting treatment of aggregate: pre-wetting time 24 hours, surface moisture content 5% Preparation method: same as example one, but adjust the curing environment (humidity 96%, temperature 21℃); The mixed granitization granite aggregate concrete significantly improves the comprehensive performance of the concrete by precisely controlling the aggregate ratio, cementitious material composition and admixture content, combined with the optimized pre-wetting process. The reasonable aggregate ratio ensures the density and strength of the concrete, the addition of mineral micro powder in the cementitious material improves the fluidity and later strength development of the cement paste, the use of admixture effectively reduces the water-binder ratio and improves the workability, the addition of alkali inhibitor effectively inhibits the alkali-aggregate reaction and prolongs the service life of the concrete, and the pre-wetting treatment ensures the good bonding of the aggregate and cement paste, further improves the durability and crack resistance of the concrete, and is suitable for various complex environment engineering construction.

[0025] The SiO2 content in the mixed granitization granite aggregate is ≥70%, and the alkali activity expansion rate is ≤0.06%; In order to ensure that the SiO2 content in the mixed granitization granite aggregate is ≥70% and the alkali activity expansion rate is ≤0.06%, the chemical composition of the rock mass should be analyzed during the aggregate mining stage, and the mine area with high SiO2 content should be preferred. During the processing process, the laser particle size analyzer is used to monitor the aggregate particle size distribution, to ensure that the fineness modulus of the fine aggregate is between 2.6 and 3.0, and the void ratio of the coarse aggregate is ≤40%. At the same time, the alkali activity expansion rate of the aggregate is detected by rapid mortar bar method and other test methods, and the aggregate that does not meet the requirements is removed or taken inhibition measures, such as adding lithium salt alkali inhibitor; The provision that the SiO2 content of the granitic granite aggregate is ≥70% and the alkali activity expansion rate is ≤0.06% significantly improves the comprehensive performance of the concrete, the high SiO2 content enhances the hardness and durability of the aggregate, which helps to improve the compressive strength and wear resistance of the concrete, and the low alkali activity expansion rate effectively prevents the concrete from cracking and damage caused by alkali aggregate reaction, prolongs the service life of the structure, and these characteristics enable the concrete to maintain good working performance and durability in harsh environments, and is suitable for various engineering structures that require high strength and durability, such as bridges, tunnels and high-rise buildings.

[0026] The mineral micro-powder is a mixture of fly ash and slag powder with a mass ratio of 1:1 to 2:1, and the particle size distribution is D50≤10μm. The fly ash and slag powder are weighed according to the predetermined mass ratio of 1:1 to 2:1, then put into the mixing equipment, and the equipment is started to mix uniformly at low speed. The mixing state is continuously monitored during the process to ensure that the two micro-powders are fully integrated, and the mixing time is not less than 5 minutes to ensure the quality of the mixture. Finally, the mineral micro-powder with a particle size distribution of D50≤10μm is obtained. During the compounding process of fly ash and slag powder, their respective advantages can be utilized. By reasonable proportioning, the performance of cementitious materials can be optimized, and the overall strength and durability of concrete can be improved. On the other hand, meeting the particle size distribution of D50≤10μm can make the mineral micro-powder better fill the voids between cement particles, improve the density of concrete, reduce internal defects, and thus improve the impermeability and other properties of concrete, providing a strong guarantee for the preparation of high-quality granitic granite aggregate concrete.

[0027] The water reducing agent is a polycarboxylic acid-based high-efficiency water reducing agent, and the dosage of the polycarboxylic acid-based high-efficiency water reducing agent is 0.8% to 1.2% of the mass of the cementitious materials. The alkali inhibitor is a lithium salt compound, and the dosage of the lithium salt compound is 0.2% to 0.5% of the mass of the cementitious materials. The polycarboxylic acid-based high-efficiency water reducing agent should be dissolved in the mixing water in advance, and then added to the stirrer after uniform stirring. The lithium salt alkali inhibitor is also dissolved in the mixing water, and forms an additive solution together with the water reducing agent. The additive solution is added synchronously during the mixing of the concrete to ensure uniform dispersion in the concrete. The dosage of the polycarboxylic acid-based high-efficiency water reducing agent is controlled at 0.8% to 1.2% of the mass of the cementitious materials, which can effectively reduce the water-cement ratio of the concrete, improve the workability, reduce the water consumption, and enhance the strength and durability of the concrete. The dosage of the lithium salt alkali inhibitor is 0.2% to 0.5% of the mass of the cementitious materials, which can effectively inhibit the alkali aggregate reaction in the concrete, prevent the concrete from cracking due to alkali aggregate reaction, and prolong the service life of the concrete. The combination of the two can not only improve the workability and mechanical properties of the concrete, but also enhance its durability, ensuring the long-term stability of the concrete in complex environments.

[0028] The slump of concrete mixture is controlled between 160 and 200 mm, and the expansion is ≥ 450 mm; By precisely controlling the water-reducing agent dosage (0.8% to 1.2% of the cementitious material mass) and the mixing water temperature (15 to 25°C), the slump of the concrete mixture can be controlled within 160 to 200 mm and the expansion ≥ 450 mm. By precisely controlling the ratio of aggregate, cementitious materials, admixtures and water, the high strength and durability of concrete are ensured. In particular, the pre-wetting of aggregates and the compound use of mineral powders effectively improve the density and crack resistance of concrete. During the preparation process, the steps of aggregate pre-treatment, cementitious material mixing, admixture dissolution and concrete mixing are carried out step by step to ensure the stability and reliability of concrete quality. Finally, through strict performance verification and uniformity testing, it is guaranteed that the concrete meets the application requirements in complex engineering environments.

[0029] In the method for preparing the above-mentioned mixed rock granite aggregate concrete adopted by the present invention, the screened and cleaned mixed rock granite aggregate is placed in a vacuum saturation device, the saturation pressure is set to -0.08 to -0.1 MPa, and the saturation time is adjusted according to the aggregate particle size. The larger the particle size, the longer the saturation time. Ensure that the aggregate fully absorbs water until the surface moisture content reaches 3% to 5%. This treatment ensures that the aggregate absorbs water evenly during the concrete mixing process, avoiding subsequent performance instability due to water migration. Aggregate pretreatment removes impurities and optimizes water absorption, improving the workability and durability of concrete. The precise ratio of cementitious materials and admixtures effectively enhances the strength and crack resistance of concrete. Strict control of the mixing and curing processes ensures the uniformity and density of the concrete's internal structure. In addition, the introduction of performance verification and uniformity testing steps further ensures the reliable quality of concrete products and meets high-standard engineering requirements.

[0030] See also Figure 1 The saturation pressure of the vacuum saturation treatment in step 1 is -0.08 to -0.1 MPa. The saturation time is positively correlated with the aggregate particle size. The aggregate particle size distribution is optimized by a laser particle size analyzer to ensure that the fine aggregate fineness modulus is 2.6 to 3.0 and the coarse aggregate void ratio is ≤40%; In the vacuum saturation treatment step, a dedicated vacuum saturation device is used to place the mixed rock granite aggregate inside the device. After sealing, the vacuum pump is started, the system pressure is adjusted to the range of -0.08 to -0.1 MPa, and the time is started. The saturation time is determined according to the maximum particle size of the aggregate. For example, the saturation time for 5mm particle size aggregate is 2 hours, and the saturation time for 10mm particle size aggregate is extended to 4 hours to ensure sufficient water penetration. At the same time, the aggregate particle size distribution is monitored using a laser particle size analyzer. The fineness modulus of the fine aggregate is adjusted to 2.6 to 3.0 through screening, and the void ratio of the coarse aggregate is ≤40% to ensure a reasonable aggregate gradation. By precisely controlling the water-saturated pressure and time, ensuring that the aggregate is fully water-absorbed, reducing the amount of mixing water, and improving the density of the concrete, the application of the laser particle size analyzer realizes precise control of the particle size distribution of the aggregate, optimization of the fineness modulus of fine aggregate and the void ratio of coarse aggregate, enhances the interlocking action between aggregates, and improves the overall strength and durability of the concrete. This scheme not only simplifies the construction process, but also ensures the stability and reliability of the concrete quality, providing high-performance building materials for construction engineering.

[0031] Please refer to Figure 1 , the stirring speed in step four is controlled at low speed 60-80 rpm and high speed 120-150 rpm, and the mixing water temperature is controlled at 15-25℃; During the stirring process, a stirrer with automatic speed regulation function is used to realize the switching between low speed 60-80 rpm and high speed 120-150 rpm through pre-set program; at the same time, a temperature control device is installed in the mixing water storage tank to monitor and adjust the water temperature in real time, ensuring that the mixing water temperature is stable within the range of 15-25℃, so as to guarantee the quality of concrete mixing; The appropriate stirring speed ensures the uniform mixing of aggregate, cementitious materials and admixtures, reduces segregation, improves the density and strength of concrete, and at the same time, the stable mixing water temperature avoids the change of concrete performance caused by temperature fluctuation, ensuring the stability and durability of concrete during the hardening process. These measures work together to make the prepared concrete have excellent mechanical properties and durability, meeting the needs of various engineering projects.

[0032] Please refer to Figure 1 , the vibration forming frequency in step five is 50-60 Hz, the amplitude is 1-2 mm, the curing environment humidity is ≥95%, and the temperature is 20±2℃; During vibration forming, a high-frequency low-amplitude vibrator is used to ensure that the internal bubbles of concrete are effectively discharged and avoid the production of honeycomb and rough surface; the humidity of the curing environment is maintained by an automatic humidification system, and the temperature is accurately adjusted by a constant temperature control system, to ensure that the concrete hardens under the best conditions and improves the final performance; High-frequency low-amplitude vibration ensures the density of concrete, effectively reduces internal defects, improves the overall strength and durability of the structure, at the same time, the high-humidity and constant-temperature curing environment promotes the full progress of cement hydration reaction, accelerates the development of strength, and helps to reduce stress cracks caused by temperature changes, thereby prolonging the service life of the concrete structure. Under the joint action of these measures, the high quality and long-term stability of the concrete product are ensured.

[0033] Please refer to Figure 1During the fourth step of the concrete mixing process, the uniformity of the mixture is monitored in real time, and online near-infrared spectroscopy analysis technology is used to collect spectral data of the mixture every 30 seconds, and when the fluctuation range of the intensity of the characteristic peaks of each component in the spectral data of the mixture is within ±3%, it is determined that the uniformity of the mixture meets the requirements, so as to ensure that each component of the concrete is fully mixed, thereby ensuring the stability of the performance of the concrete; The online near-infrared spectroscopy analysis technology is used to collect spectral data of the mixture every 30 seconds, which can realize dynamic and accurate control of the mixing process, and when the fluctuation range of the intensity of the characteristic peaks of each component in the spectral data of the mixture is within ±3%, it is determined that the uniformity meets the requirements, and this quantitative standard provides a clear basis for judgment. Through this monitoring method, it can be ensured that each component of the concrete is fully mixed, and if the components are not uniformly mixed, there will be composition differences in the concrete, which will affect the overall performance. Ensuring uniform distribution of each component can make the concrete form a uniform structure during the hardening process, reduce internal defects, and improve the strength, durability and other properties of the concrete. At the same time, stable and uniform mixture helps to ensure the stability of the performance of the concrete, avoid large fluctuations in the performance of the same batch of concrete due to uneven mixing, thereby improving the quality reliability of the concrete products and meeting the high requirements of engineering construction on the stability of the performance of the concrete.

[0034] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0035] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A mixed rock granite aggregate concrete, characterized in that: It is composed of the following components in percentage by mass: Migmatized granite aggregate: 65% to 75%, including coarse aggregate of 5 to 10 mm in size and fine aggregate of 2.36 to 4.75 mm in size, with a mass ratio of 3:1 to 4:1; Cementitious material: 20% to 28%, composed of Portland cement and mineral powder, of which the amount of mineral powder is 15% to 25% of the total mass of the cementitious material; Admixture: 0.5% to 1.5%, including water reducer and alkali inhibitor; Water: balance, water-binder ratio 0.35-0.45; The aggregate is pre-wetted for 12 to 24 hours, and the surface moisture content is controlled at 3% to 5%.

2. The mixed rock granite aggregate concrete according to claim 1, characterized in that: The SiO2 content in the migmatized granite aggregate is ≥70%, and the alkali-active expansion rate is ≤0.06%.

3. The mixed rock granite aggregate concrete according to claim 1, characterized in that: The mineral fine powder is a compound of fly ash and slag powder, with a mass ratio of 1:1 to 2:1 and a particle size distribution of D50≤10μm.

4. The mixed rock granite aggregate concrete according to claim 1, characterized in that: The water reducer is a polycarboxylic acid-based high-efficiency water reducer, and the dosage of the polycarboxylic acid-based high-efficiency water reducer is 0.8% to 1.2% of the mass of the cementitious material; the alkali inhibitor is a lithium salt compound, and the dosage of the lithium salt compound is 0.2% to 0.5% of the mass of the cementitious material.

5. The mixed rock granite aggregate concrete according to claim 1, characterized in that: The slump of the concrete mixture is controlled to be 160-200 mm, and the expansion is ≥450 mm.

6. A method for preparing a mixed rock-aggregate granite concrete, based on the mixed rock-aggregate granite concrete according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Aggregate pretreatment: The migmatized granite aggregate is screened and washed to remove surface impurities, and then vacuum saturated with water; Step 2: Mixing of cementitious materials: Mix silicate cement and mineral powder in proportion and dry mix evenly; Step 3: Dissolving the admixture: Dissolve the water reducer and alkali inhibitor in the mixing water and stir evenly; Step 4: Concrete mixing: Add the pre-wetted aggregate and cementitious material into the mixer in sequence, stir at low speed, then add the mixing water containing admixtures, and then stir at high speed; Step 5: Molding and maintenance: Pour the mixture into the mold, vibrate it into shape, cover it with a moisturizing film, and cure it for 28 days; Step 6: Performance Verification: The micromechanical properties of the interface transition zone between aggregate and cement paste were verified by multi-scale analysis methods; Step 7: Uniformity test: Aggregate distribution uniformity was verified by image analysis.

7. The method for preparing a mixed rock granite aggregate concrete according to claim 6, characterized in that: The saturation pressure of the vacuum saturation treatment in step 1 is -0.08 to -0.1 MPa, the saturation time is positively correlated with the aggregate particle size, and the aggregate particle size distribution is optimized by a laser particle size analyzer.

8. The method for preparing a mixed rock granite aggregate concrete according to claim 6, characterized in that: The stirring speed in the step 4 is controlled to be 60-80 rpm at a low speed and 120-150 rpm at a high speed, and the temperature of the mixing water is controlled to be 15-25°C.

9. The method for preparing a mixed rock granite aggregate concrete according to claim 6, characterized in that: The vibration molding frequency in the step 5 is 50-60 Hz, the amplitude is 1-2 mm, the humidity of the curing environment is ≥95%, and the temperature is 20±2°C.

10. The method for preparing a mixed rock granite aggregate concrete according to claim 6, characterized in that: During the concrete mixing process of step 4, the uniformity of the mixture is monitored in real time, and online near-infrared spectroscopy analysis technology is used to collect spectral data of the mixture every 30 seconds.

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