Preparation process of super-retarded cement stabilized macadam

Abstract

The invention relates to the technical field of building materials, and discloses a preparation process of super-retarded cement stabilized macadam, which comprises the following steps: selection and surface treatment of raw materials: selecting super-retarded cement, graded macadam, fly ash or mineral powder, a retarder and water, and carrying out nanoscale surface treatment on the macadam to improve the binding power of the macadam and cement paste, so as to obtain the super-retarded cement stabilized macadam; the ratio of the raw materials is as follows: the super-retarding cement accounts for 4%-6% of the total weight of the mixed material, and 0.1%-0.3% of a retarder is doped; the particle size range of the graded broken stone is 5-31.5 mm, and the graded broken stone accounts for 55-65% of the total weight of the mixed material; and the fly ash or mineral powder accounts for 8-12% of the total weight of the mixed material. By adopting the super-retarding cement, three-dimensional dynamic stirring and vacuum degassing processes, the problem of unstable structure caused by non-uniform stirring and bubble residue in the construction process of the traditional cement stabilized macadam material is effectively solved. The three-dimensional dynamic stirring device can be used for mixing in multiple directions, so that materials such as cement, macadam and fly ash are more uniformly distributed.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to a process for preparing ultra-slow-setting cement-stabilized crushed stone. Background Art

[0002] With the continuous improvement and innovative development of construction technology, the requirements for the performance of concrete materials are getting higher and higher. As a special new type of concrete, super-slow setting concrete adjusts the initial setting time of concrete by adding retarders, but it will not destroy the performance and safety requirements of concrete. Therefore, it has excellent performance and development prospects. The earliest super-slow setting concrete was mostly used to solve the construction difficulties of bored interlocking piles in deep foundation pit maintenance structures. Later, it was also used as emergency concrete to prevent the problem of cold joint pouring after construction was interrupted due to force majeure.

[0003] Traditional cement-stabilized crushed stone is often mixed in a single horizontal mixing method, and the uniform distribution of the material is difficult to ensure. Especially in large-scale construction, there may be separation or uneven mixing between material particles. At the same time, bubbles remain in the mixture during the construction process, resulting in reduced material density and internal defects, which ultimately affect the compressive strength and flexural properties of the road base layer, resulting in low long-term bearing capacity and prone to local damage.

[0004] Conventional cement-stabilized crushed stone uses ordinary Portland cement. Due to the fast hydration reaction rate, the material sets in a short time after mixing, and the construction operation time is strictly limited. Especially under high temperature and dry environmental conditions, the cement mixture sets faster, resulting in a shortened construction time, which brings difficulties to the construction of large-scale projects or complex terrain.

[0005] In view of the above problems, the present invention provides a process for preparing ultra-slow-setting cement-stabilized crushed stone, which effectively overcomes the shortcomings of the prior art through technological innovation. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a process for preparing super slow-setting cement stabilized gravel, which solves the problem that in the mixing process of traditional cement stabilized gravel, a single horizontal mixing method is often adopted, and the uniform distribution of materials is difficult to ensure, especially in large-scale construction, there may be separation or uneven mixing between material particles.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A process for preparing ultra-slow setting cement-stabilized crushed stone, comprising the following steps: Selection and surface treatment of raw materials: ultra-slow setting cement, graded crushed stone, fly ash or mineral powder, retarder and water are selected, and the crushed stone is subjected to nano-level surface treatment to improve its bonding force with cement paste. The proportion of the raw materials is as follows: ultra-slow setting cement accounts for 4%-6% of the total weight of the mixed material, and 0.1%-0.3% of the retarder is added; the particle size range of the graded crushed stone is 5-31.5mm, accounting for 55%-65% of the total weight of the mixed material; fly ash or mineral powder accounts for 8%-12% of the total weight of the mixed material, and is treated by alkaline activation; the water-cement ratio is 0.38-0.45, and the specific water amount is adjusted according to real-time humidity monitoring; the additives include 1%-3% silica fume and 0.05%-0.2% fiber reinforcement; the nano reinforcement accounts for 0.1%-0.5% of the total material weight, and the nano reinforcement includes silane nanoparticles and graphene nanosheets; Alkaline activation of fly ash: The fly ash is alkaline activated by sodium hydroxide or sodium silicate solution to enhance the activity of the fly ash; Premixing process of retarder and cement: premix the retarder and cement by dry mixing, and then gradually add them to other mixed materials; Two-stage mixing and homogenization: The surface-treated crushed stone, fly ash and pre-mixed cement are mixed dry for the first time, and then a proper amount of water is added for the second wet mixing to ensure the uniform distribution of the materials. A three-dimensional dynamic homogenization device is used during mixing; Vacuum degassing process: The mixed material is subjected to vacuum degassing to remove bubbles and enhance compactness; Intelligent temperature control and water-cement ratio adjustment: Use an intelligent temperature control system during mixing and transportation to ensure that the temperature of the mixture is between 10-30°C, and automatically adjust the water-cement ratio through a humidity sensor; Automated paving and layered compaction: Laser-guided paving equipment is used to automatically spread the mixture and compact it in layers. The thickness of each layer is 10-12 cm, and the compaction degree is monitored in real time by sensors. Self-healing maintenance treatment: After rolling is completed, the surface is treated with self-healing materials to enhance the self-repair ability of cracks, and covered maintenance is carried out.

[0008] Preferably, the nano-scale surface treatment is completed by nano-silane coating equipment, and the surface of the crushed stone is treated using nano-silane coating technology, and the coating thickness is 5 nanometers to 10 nanometers to enhance the bonding force between the crushed stone and the cement slurry.

[0009] Furthermore, the nano-silane coating equipment has an adjustable coating thickness control system, which can automatically adjust the coating thickness according to the ambient temperature, humidity and gravel particle size to ensure that the coating is evenly attached to the gravel surface. Through the computer control system, the coating thickness can be accurately controlled within the range of 5-10 nanometers and can be adjusted in real time according to different working conditions.

[0010] Preferably, the alkaline activation treatment of the fly ash is carried out in an automatic reactor, a 3%-6% concentration of sodium hydroxide solution is added to the reactor, the reaction temperature is controlled at 50° C.-70° C., and the treatment time is 1-2 hours.

[0011] Furthermore, the fly ash alkaline activation reactor is equipped with a built-in stirring device for evenly distributing the sodium hydroxide solution, and the stirring speed can be automatically adjusted according to the particle size of the fly ash, and the stirring speed is 20-40 rpm. The reactor also has a temperature monitoring system that can detect temperature fluctuations in the reactor in real time and automatically adjust it so that the temperature is always maintained between 50°C and 70°C to ensure that the activity of the fly ash is fully stimulated.

[0012] Preferably, the premixing of the retarder and cement is carried out by a high-efficiency spiral mixer, the speed of the mixer is 50-100 rpm, and the stirring time is 3-5 minutes to ensure uniform distribution of the retarder.

[0013] Furthermore, the retarder and cement premixing system is equipped with an automatic feeding device, which can automatically control the feeding amount according to the weight ratio of cement and retarder to ensure uniform incorporation of the retarder. The system is also equipped with an anti-blocking device to ensure that no material accumulation or blockage occurs during the premixing process. After the premixing is completed, the material will be directly fed into the next process through the automatic conveying system.

[0014] Preferably, the two-stage stirring adopts a three-dimensional dynamic stirring device, which has X, Y, and Z three-dimensional rotational motion, a stirring speed of 60-90 rpm, a first dry stirring time of 3-5 minutes, and a second wet stirring time of 5-8 minutes.

[0015] Furthermore, the three-dimensional dynamic stirring device is equipped with an intelligent monitoring system, which can monitor the mixing uniformity during the stirring process in real time and automatically adjust the stirring speed and direction. The device is also equipped with a vibration sensor, which can automatically adjust the frequency and amplitude of the X, Y, and Z three-dimensional movements according to the density and fluidity feedback of the material to ensure uniform mixing without dead ends.

[0016] Preferably, the equipment used in the vacuum degassing process is a vacuum degassing box, the vacuum degree is controlled at 0.08MPa-0.1MPa, and the degassing time is 2-4 minutes to ensure the density and stability of the mixture.

[0017] Furthermore, the vacuum degassing box is equipped with an automatic exhaust monitoring system, which can detect the gas content in the degassing process in real time and automatically adjust the vacuum degree according to the gas content to ensure the best degassing effect. The vacuum pump equipped with this system has a frequency conversion control function, which can adjust the pump speed according to the gas discharge volume to ensure that the vacuum degree is always stable within the range of 0.08MPa-0.1MPa, and the degassing time can be automatically adjusted according to the material density.

[0018] Preferably, the intelligent temperature control system adjusts the temperature during stirring and transportation in real time through a built-in temperature sensor and an automatic heating / cooling device, the temperature control range is 10°C-30°C, and monitors temperature changes in real time through a feedback loop.

[0019] Furthermore, the intelligent temperature control system adopts a modular design and includes multiple temperature adjustment units, which can independently adjust the temperature at different stages of mixing and transportation. Each adjustment unit is equipped with a high-precision temperature sensor that can detect small fluctuations in temperature changes (accuracy ±0.1°C). The temperature change information is transmitted to the central control system in real time through a feedback loop. The central system can automatically select heating or cooling mode according to different ambient temperatures to ensure that the temperature is always maintained within the range of 10°C-30°C.

[0020] Preferably, the water-cement ratio adjustment system is composed of a humidity sensor and an automatic water volume adjustment device, and real-time data feedback is performed every 10 minutes to ensure that the water-cement ratio of the mixture is maintained within the range of 0.38-0.45 by adjusting the water volume.

[0021] Furthermore, the water-cement ratio adjustment system is also equipped with an automatic calibration function, which can accurately and dynamically adjust the water-cement ratio according to the real-time humidity data of the mixture. The system collects data through multi-point humidity sensors, and each sensor is equipped with an independent data transmission channel to ensure accurate humidity feedback every 10 minutes. The adjustment device adjusts the water supply according to the feedback information and automatically calibrates to the optimal water-cement ratio in the range of 0.38-0.45.

[0022] Preferably, the automated paving equipment uses laser guidance and a satellite positioning system, the paving thickness is controlled at 15 cm-20 cm, the paving width is controlled at 6 m-8 m, and the paving flatness is adjusted in real time through a laser height sensor.

[0023] Furthermore, the satellite positioning accuracy of the laser guidance and satellite positioning system can reach the centimeter level, and the stability of the positioning data is ensured by dual-mode positioning technology (GPS and Beidou system). The system also integrates a laser height sensor to monitor the paving thickness in real time. During the paving process, the system can automatically adjust the height and speed of the paving machine to adapt to the changes in the on-site terrain, ensuring that the paving thickness is always between 15 cm and 20 cm.

[0024] Preferably, the self-healing material is cured after rolling is completed. The self-healing material is a polymer coating containing a microcapsule self-healing agent. The coating thickness is 2 mm to 3 mm. The curing period is 7 days and a protective film or straw mat is used for covering and curing.

[0025] Furthermore, the self-healing material coating equipment is equipped with an automatic spraying system, which controls the coating thickness through a computer, and can automatically adjust the coating thickness to 2 mm-3 mm according to the curing time of the mixture and environmental conditions. During the curing process, the system can monitor the humidity and temperature of the coating surface in real time, and automatically adjust the spraying amount and the sealing degree of the covering in combination with environmental data (such as wind speed, sunlight intensity, etc.) to ensure uniform coating coverage and achieve the best self-healing effect. The protective film in the curing process is made of a breathable but waterproof polymer material. The protective film has the characteristics of high temperature resistance, low temperature resistance and UV resistance, and can protect the coating from environmental influences under harsh climatic conditions. The breathable design of the membrane allows moisture to pass through, but prevents rain or dust from entering, maintains a moist environment inside the coating, and promotes the efficient effect of the self-healing material.

[0026] The present invention provides a process for preparing ultra-slow setting cement-stabilized crushed stone, which has the following beneficial effects: 1. The present invention adopts super slow setting cement, three-dimensional dynamic stirring and vacuum degassing process, which effectively solves the problem of structural instability caused by uneven stirring and residual bubbles in the construction process of traditional cement-stabilized gravel materials. The three-dimensional dynamic stirring device can mix in multiple directions, so that cement, gravel, fly ash and other materials are more evenly distributed. At the same time, the vacuum degassing technology can remove bubbles in the mixture, significantly improving the density and overall strength of the material. This technology not only effectively improves the compression and flexural properties, but also enhances the bonding force of the material, making it more stable in long-term load-bearing, and is particularly suitable for high-strength and large-area foundation engineering construction.

[0027] 2. The present invention uses super slow-setting cement and intelligent temperature control system to effectively delay the setting time of the material, overcoming the limitations of traditional cement that it is easy to solidify quickly and shorten the operating time under complex environments such as high temperature and humidity. By adjusting the water-cement ratio in real time, it ensures that the material maintains a stable working state during mixing, transportation and construction, extending the operating time of construction personnel and providing a more flexible operating window for construction of large areas or complex terrain. This advantage is particularly suitable for multi-stage construction or projects that require long-term operations, reducing material waste during the construction process and improving overall construction efficiency.

[0028] 3. The present invention uses self-healing material coatings and nano-enhancers to give cement-stabilized gravel materials the ability to automatically repair after cracks are formed. This feature effectively reduces the expansion of microcracks and avoids structural failure caused by crack expansion during long-term loads or environmental changes. In addition, the alkaline activation treatment of fly ash and the protective film maintenance technology further improve the material's anti-freeze and thaw properties, allowing it to maintain excellent durability in harsh environments such as low temperature and humidity. This design not only extends the service life of roads or infrastructure, but also reduces the frequency and cost of later maintenance, significantly improving the economic benefits of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a stereogram of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Please see attached Figure 1 : Example 1: Preparation process of ultra-slow setting cement-stabilized crushed stone at room temperature step: Selection and processing of raw materials: Super slow setting cement (5%), graded crushed stone (60%), fly ash (10%), water (25%), and 0.15% sodium citrate as a retarder were selected. The graded crushed stone was subjected to nano-level surface treatment by silane nano-coating equipment to ensure that the adhesion of the crushed stone surface was enhanced. The coating thickness was 5 nanometers.

[0032] Alkaline activation treatment of fly ash: Place the fly ash in an automatic reactor, add 5% sodium hydroxide solution, set the reaction temperature at 60°C, and activate for 1.5 hours to ensure that the activity of the fly ash is significantly improved.

[0033] Premixing of cement and retarder: Sodium citrate was premixed with super retarder cement by dry mixing and stirred at 80 rpm for 4 minutes using a spiral high efficiency mixer to ensure uniform distribution of the retarder.

[0034] Two-stage mixing and homogenization: dry mix the surface treated gravel, activated fly ash and premixed cement for 5 minutes. Then add appropriate amount of water and wet mix for 7 minutes. Use three-dimensional dynamic mixing equipment to ensure that the mixture is evenly distributed in the three directions of X, Y and Z.

[0035] Vacuum degassing treatment: The mixture after stirring is degassed by a vacuum degassing device with the vacuum degree set to 0.09 MPa for 3 minutes to ensure the compactness of the mixture.

[0036] Temperature control and water-cement ratio adjustment: Use an intelligent temperature control system to control the mixture temperature at 20°C during mixing and transportation, and use a humidity sensor to monitor and adjust the water-cement ratio to 0.40 in real time.

[0037] Automated paving and rolling: The mixture is spread by laser-guided paving equipment with a thickness of 18 cm. A vibratory roller is used for layered rolling with each layer being 10 cm thick. Compaction monitoring ensures that each layer meets the design requirements.

[0038] Self-healing curing treatment: After the rolling is completed, the surface is evenly coated with microcapsule self-healing agent polymer material with a coating thickness of 2 mm. The curing time is 7 days and covered with straw mats.

[0039] Changes compared to existing technologies: In this embodiment, the surface of the crushed stone was treated by introducing a silane nano-coating device, which significantly improved the bonding strength between the crushed stone and the cement paste. The alkaline activation treatment of fly ash also enhanced its activity and optimized the physical properties of the mixture. The three-dimensional dynamic stirring and vacuum degassing process ensured the uniformity and density of the material, and the introduction of the intelligent temperature control system and automation equipment effectively controlled the construction environment conditions.

[0040] New effects: This embodiment improves the compressive strength and bonding properties of cement-stabilized crushed stone at room temperature, prolongs the construction operation time, reduces material segregation and bubbles, improves the density of the mixture, and ultimately enhances the durability of the pavement structure.

[0041] Example 2: Preparation process of ultra-slow setting cement-stabilized crushed stone under high temperature environment step: Selection and processing of raw materials: Super slow setting cement (4%), graded crushed stone (58%), mineral powder (12%), water (26%), and 0.2% sugar retarder were added. The crushed stone was surface treated by silane nano coating equipment, and the coating thickness was 8 nanometers.

[0042] Alkaline activation treatment of mineral powder: Use an automatic reactor to treat the mineral powder, use 4% sodium silicate solution, the reaction temperature is 70°C, and the activation time is 2 hours.

[0043] Premixing of cement and retarder: Sugar retarder and cement were dry mixed in a high-efficiency spiral mixer at a speed of 60 rpm for 5 minutes.

[0044] Two-stage mixing and homogenization: dry mix the crushed stone, mineral powder and cement for 4 minutes, then add water for wet mixing for 6 minutes, and use three-dimensional dynamic homogenization equipment to ensure uniformity.

[0045] Vacuum degassing treatment: The mixture passes through a vacuum degassing box with a vacuum degree of 0.08 MPa for 4 minutes to ensure that the bubbles in the mixture are completely discharged.

[0046] Temperature control in high temperature environment: Use intelligent temperature control system to ensure that the mixture temperature does not exceed 25℃ at high temperature, monitor in real time and adjust the temperature through cooling device.

[0047] Automated paving and rolling: Using laser-guided paving equipment, the paving thickness is controlled at 15 cm, and the rolling thickness of each layer is 12 cm, ensuring the compaction quality under high temperature conditions.

[0048] Self-healing maintenance treatment: Use a self-healing material coating with a thickness of 3 mm during maintenance. Perform moist maintenance within 7 days and cover with a sunshade cloth to prevent high temperature effects.

[0049] Changes compared to existing technologies: This embodiment is particularly aimed at the construction requirements in high temperature environment, and adopts intelligent temperature control system and cooling device to maintain appropriate material temperature to avoid premature hydration of materials in high temperature environment. Alkaline activation treatment of mineral powder is introduced to enhance the heat resistance of materials.

[0050] New effects: Through temperature control and cooling technology, this process effectively slows down the solidification speed of materials under high temperature, prolongs the construction operation time, and significantly improves the durability and strength of materials. At the same time, the moistening and shading treatment during the curing process effectively prevents the negative impact of high temperature on the materials.

[0051] Example 3: Preparation process of ultra-slow setting cement-stabilized crushed stone in low temperature environment step: Selection and processing of raw materials: Super slow setting cement (5.5%), graded crushed stone (60%), fly ash (9%), water (25%), and 0.12% sodium gluconate as a retarder were selected. The crushed stone was treated with a silane nano coating device, and the coating thickness was 6 nanometers.

[0052] Alkaline activation treatment of fly ash: Use a reactor to add 4% sodium hydroxide solution to treat fly ash at 50°C, and the activation time is 1 hour.

[0053] Premixing of retarder and cement: Dry mixing was performed by high-speed mixer at 90 rpm for 5 minutes.

[0054] Two-stage mixing and homogenization: dry mixing for 3 minutes followed by wet mixing for 5 minutes, using a three-dimensional homogenizer to ensure uniformity.

[0055] Vacuum degassing treatment: Use a vacuum degassing box with a vacuum degree of 0.09 MPa for 2 minutes.

[0056] Temperature control in low temperature environment: Use a heating device to keep the mixture above 15°C, and control the temperature change through an intelligent temperature control system.

[0057] Automated paving and rolling: Laser-guided paving equipment is used, with a thickness of 20 cm and a rolling thickness of 10 cm per layer to ensure material density in low-temperature environments.

[0058] Self-healing curing treatment: During the curing period, microcapsule self-healing material is used with a coating thickness of 3 mm and covered with thermal insulation material. The curing time is 10 days.

[0059] Changes compared to existing technologies: In this embodiment, a heating device and an intelligent temperature control system are introduced to ensure that the material does not freeze or condense too quickly in a low temperature environment. By adding insulation material coverage, the performance of the self-healing material can be fully exerted at low temperatures.

[0060] New effects: This process significantly improves the frost resistance and construction efficiency of cement-stabilized crushed stone in low-temperature environments. The application of heating and insulation devices ensures normal construction operations under low temperatures, prolongs the setting time of the material, and ensures the final density and durability of the material.

[0061] Example 4: Preparation process of ultra-slow setting cement-stabilized crushed stone under rapid hardening requirements step: Selection and processing of raw materials: Select super slow setting cement (6%), graded crushed stone (62%), mineral powder (8%), water (24%), and add 0.3% of quick setting agent. The crushed stone surface is treated by nano coating equipment, and the coating thickness is 7 nanometers.

[0062] Alkaline activation treatment of mineral powder: Use 3% sodium silicate solution for treatment in a reactor, the reaction temperature is 60°C, and the activation time is 1 hour.

[0063] Premix cement and accelerator: Mix in a high-speed mixer at 120 rpm for 3 minutes to ensure uniform distribution of the accelerator.

[0064] Two-stage mixing: dry mix the mineral powder and crushed stone for 3 minutes, then add water and wet mix for 4 minutes, using dynamic homogenization equipment.

[0065] Vacuum degassing treatment: vacuum degree is 0.1 MPa, time is 2 minutes, to ensure the rapid molding of the material.

[0066] Temperature control and paving: Normal temperature control is adopted, the paving thickness is 16 cm, and each layer is rolled 12 cm.

[0067] Rolling and forming: Use vibratory rollers for layered rolling, and monitor compaction to ensure rapid forming.

[0068] Rapid self-healing maintenance: The maintenance time is shortened to 5 days, and a quick-setting coating is used to protect the surface.

[0069] Changes compared to existing technologies: In view of the rapid hardening requirements of emergency construction, this embodiment adopts a quick-setting agent and a normal temperature control device, which can significantly shorten the construction time. The curing period is shortened by using a quick-setting coating.

[0070] New effects: This process can quickly harden under urgent construction needs, and ensures the density and crack resistance of the material through vacuum degassing and quick-setting coating. It shortens the construction period while ensuring the strength and durability of the structure.

[0071] Example 5: Preparation process of ultra-slow setting cement-stabilized crushed stone in complex geological environment step: Selection and processing of raw materials: Super slow setting cement (4.5%), graded crushed stone (59%), fly ash (9%), water (27%), and 0.18% sodium citrate were added. The crushed stone was treated with silane nano coating equipment, and the coating thickness was 6 nanometers.

[0072] Alkaline activation treatment of fly ash: Treat with 4% sodium hydroxide solution at 55°C for 1.5 hours.

[0073] Premixing process: Cement and retarder are dry mixed in a high-speed mixer at a speed of 90 rpm for 5 minutes.

[0074] Two-stage mixing and homogenization: dry mixing for 5 minutes, then wet mixing for 7 minutes, using three-dimensional dynamic mixing equipment for uniform mixing.

[0075] Vacuum degassing treatment: Use a vacuum box for degassing with a vacuum degree of 0.09 MPa for 4 minutes.

[0076] Intelligent temperature control system: ensure that the temperature is controlled at 18°C ​​during construction, and the humidity sensor monitors the water-cement ratio in real time and adjusts it to 0.42.

[0077] Paving and rolling: The laser paving equipment controls the thickness to 18 cm, and the roller is used for layered rolling with a thickness of 12 cm.

[0078] Self-healing maintenance for complex geology: The thickness of the self-healing coating is 3 mm, and the maintenance period is 7 days. A covering film is used for maintenance to prevent the impact of complex geological conditions on construction.

[0079] Changes compared to existing technologies: This embodiment is particularly suitable for construction under complex geological conditions. It adopts a more accurate temperature control system and humidity sensor control to ensure that the material can still maintain excellent performance under complex geological conditions.

[0080] New effects: Through temperature control, humidity control and vacuum degassing, this process ensures the stability and compactness of materials in complex geological environments, and further improves the durability and deformation resistance of the construction.

[0081] Summary: The above five embodiments adopt different technical means according to different construction environments (normal temperature, high temperature, low temperature, complex geology, and rapid hardening requirements), such as nano-level coating treatment, alkaline activation, intelligent temperature control system, vacuum degassing process, etc., which significantly improve the construction quality and durability of cement-stabilized crushed stone in various environments. Each embodiment is optimized for its specific working conditions, ensuring the uniformity, density and durability of the material, and achieving multiple effects such as extending the construction operation time, improving the compressive strength, and accelerating the hardening time.

[0082] Comprehensive test experiment: comparison of five embodiments Experimental background: In order to compare the performance of the five embodiments (Embodiment 1: normal temperature environment, Embodiment 2: high temperature environment, Embodiment 3: low temperature environment, Embodiment 4: rapid hardening requirement, Embodiment 5: complex geological environment) in different application scenarios, a comprehensive test experiment was designed. The test included the comparison of multiple important performance indicators: compressive strength, flexural strength, material density, adhesion, operable time, self-healing performance, freeze-thaw resistance and crack development.

[0083] Experimental process: Sample preparation: According to the raw material ratios and process requirements of the five embodiments, standard cubic test blocks with a size of 100 mm x 100 mm x 100 mm were prepared, 10 groups of test blocks were prepared for each embodiment, and all performance indicators were tested for each group of test blocks.

[0084] Test items: Compressive strength: An automatic pressure tester was used to test the compressive strength of each embodiment.

[0085] Flexural strength: The flexural strength of the mixed material was measured using a four-point flexural test method.

[0086] Compactness: The bulk density of the material is calculated by vacuum compaction measurement.

[0087] Bond strength: Pull-out test is used to test the bond strength between cement paste and crushed stone.

[0088] Operable time: The initial setting time is tested by Vicat instrument to determine the operable time during the construction process.

[0089] Self-healing performance: artificial cracks were treated and maintained for 7 days to test the degree of crack healing.

[0090] Freeze-thaw resistance: The mass loss and crack changes of the test specimen after 100 freeze-thaw cycles.

[0091] Experimental data table:

[0092] Description and analysis: Compressive strength: Example 4 (fast hardening requirement) performs best in terms of compressive strength, reaching 65.2 MPa, and is suitable for projects that require rapid prototyping and fast strength development.

[0093] Example 3 (low temperature environment) performs relatively slowly, and its compressive strength is low due to the low temperature, but it still has a certain degree of stability.

[0094] Flexural strength: The flexural strength of Example 4 also performed best, reaching 8.2 MPa, showing its advantages in bending resistance and crack resistance.

[0095] Density: The density of Example 4 is the highest, reaching 2.41 g / cm³, which shows that the vacuum degassing process and dynamic stirring technology in this example ensure the high density and uniformity of the material.

[0096] Adhesion: The bonding strength between the cement paste and the crushed stone in Example 4 is the strongest, which is 2.45 N / mm², and is suitable for projects that require stronger bonding strength.

[0097] The bonding force of Example 3 is the lowest, only 1.95 N / mm², which indicates that the low temperature environment has a negative impact on the bonding effect between cement and aggregate.

[0098] Operation time: The operable time of Example 4 is the shortest, only 1.7 hours, and is suitable for fast construction projects.

[0099] Example 3 has the longest operable time (3.6 hours) under low temperature environment, which is related to the slowdown of hydration reaction at low temperature.

[0100] Self-healing properties: The crack healing effect of Example 4 is the best, and the crack healing width is only 0.25 mm, indicating that its self-healing material still has a good effect under the condition of rapid hardening.

[0101] In Example 3, due to the low temperature environment, the self-healing performance is slightly weaker, but it still has a certain healing effect.

[0102] Freeze-thaw resistance: Example 4 has the best freeze-thaw resistance, with a mass loss of only 1.3% and minimal crack development, indicating that it has high stability in cold and complex climates.

[0103] Example 2 (high temperature environment) Due to the adverse effect of high temperature on material hydration, the freeze-thaw resistance is poor and the mass loss reaches 2.0%.

[0104] Crack Development: The crack development of Example 4 is the smallest, which is 0.16 mm, which shows that it has strong self-healing performance and can effectively resist crack expansion caused by environmental stress.

[0105] Summarize: Example 4 (rapid hardening requirement) performed well in all tests and is particularly suitable for construction projects that require rapid hardening and early strength development.

[0106] Example 1 (normal temperature) and Example 5 (complex geology) have relatively balanced performance and are suitable for construction projects in general environments.

[0107] Example 3 (low temperature environment) Although the early strength development is slow, the self-healing performance and freeze-thaw resistance are relatively excellent, which is suitable for projects in cold areas.

[0108] Example 2 (high temperature environment) The hydration reaction is accelerated under high temperature conditions, resulting in slightly lower compression resistance and freeze-thaw resistance, but it can still meet the construction requirements of high temperature environment.

[0109] Through this experiment, the specific performance of the five embodiments in different performance indicators was obtained, which is convenient for engineering projects to select appropriate process solutions according to actual needs.

[0110] Comparative experiment 1: Comparison of compressive strength, flexural strength and bonding strength Purpose: The differences between the prior art and the present invention in terms of compressive strength, flexural strength and the bonding force between cement paste and crushed stone are compared.

[0111] Existing technical solutions: Ordinary Portland cement and conventional mixing process are used, without retarder and vacuum degassing process, and the gravel surface is not treated, resulting in relatively ordinary material properties.

[0112] The scheme of the present invention: The material properties are improved by using ultra-slow setting cement, three-dimensional dynamic mixing, vacuum degassing technology and crushed stone with nano-scale surface treatment, combined with fly ash alkaline activation treatment.

[0113] Testing process: Sample preparation: Prepare 100mm x 100mm standard test blocks to test the compressive strength, flexural strength and adhesion. Test 5 groups of test blocks in each group.

[0114] Compression strength test: tested by pressure testing machine, the unit is MPa.

[0115] Flexural strength test: Four-point flexural strength test method is adopted, the unit is MPa.

[0116] Bond test: The bond strength between cement paste and crushed stone is measured by pull-out test, in N / mm².

[0117] Experimental data table 1:

[0118] Analysis and conclusion: The compressive strength and flexural strength of the present invention are increased by about 11 MPa and 1.3 MPa, respectively, indicating that the use of ultra-slow setting cement, vacuum degassing and other technologies significantly improves the strength of the material.

[0119] The bonding strength increased by about 0.48 N / mm², and the fly ash alkaline activation treatment and nano-scale surface treatment enhanced the adhesion between the cement paste and the crushed stone.

[0120] Comparative experiment 2: Comparison of density and operable time Purpose: The performance of the prior art and the present invention in terms of material density and construction operability time were compared to evaluate the differences between the two in terms of material density and construction flexibility.

[0121] Existing technical solutions: Ordinary mixing technology is used without adopting vacuum degassing and intelligent temperature control system, the density is low, and due to the short setting time, the construction operation time is relatively limited.

[0122] The scheme of the present invention: The use of super slow-setting cement, three-dimensional dynamic mixing and vacuum degassing technology, combined with intelligent temperature control and humidity sensor control, ensures the high density of the material and extends the construction operating time.

[0123] Testing process: Density test: Use the bulk density method to test the density of the material, with 5 groups of test pieces in each test, and the unit is g / cm³.

[0124] Operable time test: The time from the completion of mixing to the initial setting of the material is tested by Vicat instrument, and the unit is hours.

[0125] Experimental data table 2:

[0126] Analysis and conclusion: Density: The average density of the present invention is 2.34 g / cm³, which is significantly improved compared with 2.19 g / cm³ of the prior art, indicating that the vacuum degassing process has a significant effect on improving the density of the material.

[0127] Operation time: The average operation time of the present invention is extended to 2.8 hours, which is much higher than 1.5 hours in the prior art. The use of super slow setting cement makes the construction more flexible.

[0128] Comparative experiment 3: Comparison of self-healing performance and anti-freeze-thaw performance Purpose: The performance of the prior art and the present invention in terms of self-healing performance and freeze-thaw resistance was compared to verify the durability and self-repairing ability of the material of the present invention in harsh environments.

[0129] Existing technical solutions: The existing technology does not use self-healing materials, the materials perform poorly during crack expansion and freeze-thaw cycles, the cracks cannot be automatically repaired, and the material quality loss is large.

[0130] The scheme of the present invention: The present invention adopts a self-healing material coating, combined with protective film maintenance, to significantly improve the material's self-healing ability and freeze-thaw resistance.

[0131] Testing process: Self-healing performance test: After crack treatment, apply self-healing material and measure the crack healing status after 7 days.

[0132] Freeze-thaw resistance test: After the test block has undergone 100 freeze-thaw cycles, the mass loss and crack extension are measured.

[0133] Experimental data table 3:

[0134] Analysis and conclusion: Self-healing performance: The average crack healing width of the present invention is 0.31 mm, while the prior art has no self-healing ability, indicating that the self-healing material of the present invention is effective in repairing cracks.

[0135] Freeze-thaw resistance: The mass loss of the present invention is only 1.6%, and the crack expansion is 0.18 mm, while the mass loss rate of the prior art is 3.5%, indicating that the freeze-thaw resistance of the present invention in cold environments is significantly enhanced.

[0136] Summarize: Comparative experiment 1: The present invention is significantly superior to the prior art in terms of compression resistance, flexural strength and bonding strength, especially in terms of bonding strength.

[0137] Comparative experiment 2: The present invention performs better in terms of material density and operable time, and is suitable for more complex construction environments.

[0138] Comparative Experiment 3: The self-healing material of the present invention has remarkable anti-freeze-thaw performance and is suitable for engineering applications in cold and harsh environments.

[0139] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing ultra-slow setting cement-stabilized crushed stone, characterized in that: The following steps are involved: Selection and surface treatment of raw materials: ultra-slow setting cement, graded crushed stone, fly ash or mineral powder, retarder and water are selected, and the crushed stone is subjected to nano-level surface treatment to improve its bonding force with cement paste. The proportion of the raw materials is as follows: ultra-slow setting cement accounts for 4%-6% of the total weight of the mixed material, and 0.1%-0.3% of the retarder is added; the particle size range of the graded crushed stone is 5-31.5mm, accounting for 55%-65% of the total weight of the mixed material; fly ash or mineral powder accounts for 8%-12% of the total weight of the mixed material, and is treated by alkaline activation; the water-cement ratio is 0.38-0.45, and the specific water amount is adjusted according to real-time humidity monitoring; the additives include 1%-3% silica fume and 0.05%-0.2% fiber reinforcement; the nano reinforcement accounts for 0.1%-0.5% of the total material weight, and the nano reinforcement includes silane nanoparticles and graphene nanosheets; Alkaline activation of fly ash: The fly ash is alkaline activated by sodium hydroxide or sodium silicate solution to enhance the activity of the fly ash; Premixing process of retarder and cement: premix the retarder and cement by dry mixing, and then gradually add them to other mixed materials; Two-stage mixing and homogenization: The surface-treated crushed stone, fly ash and pre-mixed cement are mixed dry for the first time, and then a proper amount of water is added for the second wet mixing to ensure the uniform distribution of the materials. A three-dimensional dynamic homogenization device is used during mixing; Vacuum degassing process: The mixed material is subjected to vacuum degassing to remove bubbles and enhance compactness; Intelligent temperature control and water-cement ratio adjustment: Use an intelligent temperature control system during mixing and transportation to ensure that the temperature of the mixture is between 10-30°C, and automatically adjust the water-cement ratio through a humidity sensor; Automated paving and layered compaction: Laser-guided paving equipment is used to automatically spread the mixture and compact it in layers. The thickness of each layer is 10-12 cm, and the compaction degree is monitored in real time by sensors. Self-healing maintenance treatment: After rolling is completed, the surface is treated with self-healing materials to enhance the self-repair ability of cracks, and covered maintenance is carried out.

2. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The nano-scale surface treatment is completed by nano-silane coating equipment, and the surface of the crushed stone is treated using nano-silane coating technology. The coating thickness is 5 nanometers to 10 nanometers to enhance the bonding force between the crushed stone and the cement slurry.

3. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The alkaline activation treatment of the fly ash is carried out in an automatic reactor, a sodium hydroxide solution with a concentration of 3%-6% is added into the reactor, the reaction temperature is controlled at 50° C.-70° C., and the treatment time is 1-2 hours.

4. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The retarder and cement are premixed by a high-efficiency spiral mixer, the speed of the mixer is 50-100 rpm, and the stirring time is 3-5 minutes to ensure uniform distribution of the retarder.

5. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The two-stage stirring adopts a three-dimensional dynamic stirring device, which has X, Y, and Z three-dimensional rotational motion, a stirring speed of 60-90 rpm, a first dry stirring time of 3-5 minutes, and a second wet stirring time of 5-8 minutes.

6. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The equipment used in the vacuum degassing process is a vacuum degassing box, the vacuum degree is controlled at 0.08MPa-0.1MPa, and the degassing time is 2-4 minutes to ensure the density and stability of the mixture.

7. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The intelligent temperature control system adjusts the temperature during mixing and transportation in real time through built-in temperature sensors and automatic heating / cooling devices. The temperature control range is 10°C-30°C, and the temperature changes are monitored in real time through a feedback loop.

8. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The water-cement ratio adjustment system is composed of a humidity sensor and an automatic water volume adjustment device, which provides real-time data feedback every 10 minutes and ensures that the water-cement ratio of the mixture is maintained within the range of 0.38-0.45 by adjusting the water volume.

9. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The automated paving equipment uses laser guidance and satellite positioning systems to control the paving thickness between 15 cm and 20 cm, the paving width between 6 m and 8 m, and adjusts the paving flatness in real time through a laser height sensor.

10. The process for preparing ultra-slow setting cement-stabilized crushed stone according to claim 1, characterized in that: The self-healing material is cured after rolling. The self-healing material is a polymer coating containing a microcapsule self-healing agent. The coating thickness is 2 mm to 3 mm. The curing period is 7 days and a protective film or straw mat is used for covering and curing.

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