A method for controlling uniform distribution precision of uhpc aggregate in mass concrete construction

Abstract

This invention discloses a method for controlling the uniform distribution accuracy of aggregates in UHPC (Ultra-High Volume Concrete) construction, belonging to the field of concrete construction technology. It includes: S1, aggregate pretreatment; S2, mixture preparation; S3, transportation and placement; S4, vibration and leveling; and S5, monitoring of the pouring process. This invention ensures uniform distribution of aggregates in concrete through multi-level classification and screening, pre-wetting treatment, and precise mix proportion control. This reduces segregation and accumulation, resulting in a denser internal structure and lower porosity. The uniformly distributed aggregates fully bond with the cement paste, forming a high-strength skeletal structure, achieving a compressive strength of over 180 MPa, and significantly improving the load-bearing capacity and durability of the concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete construction technology, specifically a method for controlling the uniform distribution accuracy of UHPC aggregates in large-volume concrete construction. Background Technology

[0002] Ultra-high performance concrete (UHPC), as a new type of high-performance concrete material, has shown great application potential in large-volume concrete projects due to its excellent properties such as ultra-high strength, high durability, and low permeability. With the continuous improvement of the structural performance requirements of modern buildings, the application of UHPC in large-volume concrete projects is increasing. Building structures have put forward extremely high requirements for the strength, durability, and workability of concrete.

[0003] However, ensuring the uniform distribution of UHPC aggregates during large-volume concrete construction has always been a challenge. Traditional UHPC construction methods often employ conventional concrete mixing, transportation, and pouring processes. However, due to the unique composition of UHPC—its small aggregate size, large specific surface area, and the presence of a large amount of fine powder and admixtures—aggregate segregation and uneven accumulation are prone to occur during mixing, transportation, and pouring. These problems not only affect the workability of UHPC but also lead to defects within the concrete structure, such as voids and honeycombing, thereby reducing the strength and durability of the concrete. This limits the full utilization of UHPC in large-scale engineering structures. Therefore, a method for controlling the uniform distribution accuracy of UHPC aggregates in large-volume concrete construction is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the uniform distribution accuracy of UHPC aggregates in large-volume concrete construction, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution, including: S1. Aggregate pretreatment, wherein S1. Aggregate pretreatment includes multi-level classification and screening of UHPC aggregates to remove particles that do not meet the particle size requirements, surface cleaning treatment of aggregates using high-pressure water guns or special cleaning agents to remove mud, powder, oil and impurities, and pre-wetting treatment of aggregates before mixing. S2, Mixture Preparation, wherein S2, Mixture Preparation includes adding the pretreated aggregate and other constituent materials of UHPC into a forced mixer according to the design ratio for dry mixing, slowly adding water and additives, continuing mixing, and performing wet mixing. During the mixing process, the temperature of the mixture is controlled by the cooling device built into the mixer or the external circulating water system. S3, Transportation and Placement, wherein S3, Transportation and Placement includes using a concrete mixing truck with spiral mixing blades, and using a concrete placing machine or distributor with adjustable flow rate to evenly distribute the concrete mixture within the large-volume concrete foundation formwork. S4. Vibration and leveling: In S4, vibration and leveling, an immersion vibrator with a frequency of 40-60Hz and a power of 1.5-2.5kW is used to vibrate the concrete at a low frequency and high power. Laser leveling technology is used to level the concrete surface. During vibration and leveling, manual adjustments are made and the distribution of aggregates is closely observed. S5. Monitoring of the pouring process: During the pouring of large-volume concrete, multiple monitoring points are set up for multi-technology monitoring. Ultrasonic detection technology, resistivity detection technology or optical imaging technology are used to monitor the distribution of UHPC aggregate inside the concrete in real time, and data feedback and adjustment are carried out. Based on the monitoring data, the construction process parameters are adjusted in a timely manner. As a further preferred embodiment of this technical solution: in the classification and screening, crushed stone aggregates with particle sizes of 2.36-4.75mm, 3-5mm, and 5-8mm are selected and mixed in a weight ratio of 30:40:30 to ensure optimized aggregate gradation; in the surface cleaning, it is ensured that there are no substances on the aggregate surface that affect its bonding with cement paste, and the mud powder content is controlled within 0.5%; in the pre-wetting treatment, the moisture content is controlled at 2%-3% to reduce the absorption of water by the aggregate during the mixing process and avoid a decrease in the fluidity of the paste. As a further preferred embodiment of this technical solution: in the dry mixing process, the mixer speed is controlled at 40-60 rpm, and the dry mixing time is not less than 3 minutes to ensure that the aggregate and solid powder are fully and evenly mixed. In the wet mixing process, the total mixing time is controlled at 5-7 minutes, of which the wet mixing stage is not less than 2 minutes to ensure that the mixture is uniform and has good workability, and that the slurry can fully coat the aggregate. As a further preferred embodiment of this technical solution: the special transport vehicle maintains a uniform rotation speed during transportation, with the rotation speed controlled at 2-4 r / min to prevent aggregate settling and segregation; the moving speed and distribution range of the concrete placing machine are adjusted according to the slump of the concrete and the size of the pouring area to ensure that each part is evenly covered. As a further preferred embodiment of this technical solution: the vibration points in the low-frequency high-power vibration are evenly arranged in a quincunx pattern with a spacing of no more than 500mm. The vibration time is appropriate when the concrete surface is covered with slurry and no more large amounts of air bubbles emerge. Generally, the vibration time for each vibration point is 20 to 30 seconds to avoid over-vibration or under-vibration. In the laser leveling technology, the laser leveling machine controls the leveling accuracy by emitting a laser beam to ensure that the flatness of the concrete surface meets the requirements. In the manual adjustment, if there is local accumulation or missing aggregate, special tools are used for manual adjustment in a timely manner, such as using a rake to remove the accumulated aggregate or replenish the missing parts. As a further preferred embodiment of this technical solution: the ultrasonic detection technology in the multi-technology monitoring transmits and receives ultrasonic signals, analyzes the propagation speed and attenuation of the signals in concrete, and judges the uniformity of aggregate distribution. The data feedback and adjustment adjust the vibration time, material placement speed, concrete slump, etc. As a further preferred embodiment of this technical solution: other constituent materials in the dry mixing process include cement, mineral admixtures, and additives; As a further preferred embodiment of this technical solution: the slump of the fabric laid by the fabric laying machine is controlled at 220-260mm; As a further preferred embodiment of this technical solution: the flatness of the laser leveling technology meets the requirement of error ≤2mm / 2m.

[0006] As a further preferred embodiment of this technical solution: when a large amount of aggregate is detected in a certain area during the data feedback and adjustment, the vibration time in that area can be appropriately extended or the amount of material laid can be reduced.

[0007] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention ensures that aggregates are evenly distributed in concrete through multi-level classification and screening, pre-wetting treatment, and precise proportion control, reducing segregation and accumulation, making the internal structure of concrete more compact, reducing porosity, and ensuring that the evenly distributed aggregates are fully bonded to the cement paste to form a high-strength skeleton structure, enabling the compressive strength to reach more than 180MPa, and significantly improving the load-bearing capacity and durability of concrete.

[0008] 2. This invention uses a forced mixer and a special transport vehicle to shorten the mixing time and reduce the aggregate settlement rate during transportation, ensuring stable concrete quality and reducing on-site waiting time. The combination of an adjustable flow rate concrete placing machine and a low-frequency high-power vibrator increases the placing speed and vibration efficiency, significantly shortening the construction cycle. The multi-technology monitoring system provides real-time feedback on aggregate distribution, allowing for timely adjustment of construction parameters, reducing rework and repairs, and improving construction continuity and overall efficiency. Attached Figure Description

[0009] Figure 1This is a flowchart of a method for controlling the uniform distribution accuracy of aggregates in UHPC (Ultra-High-Volume Concrete) construction according to the present invention. Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Example: Please see Figure 1 As shown, the present invention provides a technical solution including: S1, aggregate pretreatment, S1, aggregate pretreatment includes multi-level classification and screening of UHPC aggregates to remove particles that do not meet the particle size requirements, surface cleaning treatment of the aggregates using a high-pressure water gun or special cleaning agent to remove mud, powder, oil and impurities, drying treatment of the washed aggregates to remove surface moisture and avoid affecting the fluidity of the slurry during subsequent mixing, and pre-wetting treatment of the aggregates before mixing; S2. Mixture preparation: S2. Mixture preparation includes adding the pretreated aggregate and other components of UHPC to a forced mixer according to the design ratio for dry mixing, slowly adding water and additives, and continuing to mix for wet mixing. During the mixing process, the temperature of the mixture is controlled by the cooling device built into the mixer or the external circulating water system. S3. Transport and placement: S3. Transport and placement includes using a concrete mixer truck with spiral mixing blades, and using a concrete placing machine or distributor with adjustable flow rate to evenly distribute the concrete mixture within the large-volume concrete foundation formwork. S4. Vibration and leveling: In S4. Vibration and leveling, an immersion vibrator with a frequency of 40-60Hz and a power of 1.5-2.5kW is used to vibrate the concrete at a low frequency and high power. Laser leveling technology is used to level the concrete surface. During vibration and leveling, manual adjustments are made and the distribution of aggregates is closely observed. S5. Monitoring of the pouring process: During the pouring of large-volume concrete, multiple monitoring points are set up for multi-technology monitoring. Ultrasonic detection technology, resistivity detection technology or optical imaging technology are used to monitor the distribution of UHPC aggregate inside the concrete in real time, and data feedback and adjustment are carried out. Based on the monitoring data, the construction process parameters are adjusted in a timely manner. In this embodiment, specifically: during the classification and screening, crushed stone aggregates with particle sizes of 2.36–4.75 mm, 3–5 mm, and 5–8 mm are selected and mixed in a weight ratio of 30:40:30. This can form the densest packing structure, reduce porosity, improve the density and strength of concrete, and ensure optimized aggregate gradation. During surface cleaning, it is ensured that there are no substances on the surface of the aggregates that affect their adhesion to the cement paste, and the mud powder content is controlled within 0.5%. During the pre-wetting treatment, the moisture content is controlled at 2%–3% to reduce the absorption of water by the aggregates during the mixing process and avoid a decrease in paste fluidity. This not only reduces the absorption of water by the aggregates during the mixing process and avoids a decrease in paste fluidity, but also prevents segregation of the aggregates during transportation and placement due to excessive moisture content. In this embodiment, specifically: in the dry mixing process, the mixer speed is controlled at 40-60 rpm, and the dry mixing time is not less than 3 minutes to ensure that the aggregate and solid powder are fully and evenly mixed, while avoiding aggregate breakage or powder flying due to excessive speed. In the wet mixing process, the total mixing time is controlled at 5-7 minutes, of which the wet mixing stage is not less than 2 minutes to ensure that the mixture is uniform and has good workability, and that the slurry can fully coat the aggregate. In this embodiment, specifically: during the transportation process, the special transport vehicle maintains a uniform rotation speed, controlled at 2-4 r / min, to prevent aggregate settling and segregation. During the concrete placement process, the moving speed and placement range of the concrete placing machine are adjusted according to the slump of the concrete and the size of the pouring area to ensure that each part is evenly covered. By adjusting the moving speed and placement range of the concrete placing machine, it is ensured that each part is evenly covered with the concrete mixture, avoiding local accumulation or missing parts. In this embodiment, specifically: the vibration points in the low-frequency high-power vibration are evenly arranged in a quincunx pattern with a spacing of no more than 500mm, which can ensure that the air bubbles in the concrete are fully discharged, improving the density and strength of the concrete. The vibration time is appropriate when the concrete surface is covered with slurry and no more large number of air bubbles emerge. Generally, the vibration time for each vibration point is 20 to 30 seconds to avoid over-vibration or under-vibration. In the laser leveling technology, the laser leveling machine controls the leveling accuracy by emitting a laser beam to ensure that the flatness of the concrete surface meets the requirements. If there is local accumulation or missing aggregate during manual adjustment, special tools are used in time for manual adjustment, such as using a rake to remove the accumulated aggregate or replenish the missing parts. In this embodiment, specifically: in multi-technology monitoring, ultrasonic detection technology transmits and receives ultrasonic signals, analyzes the propagation speed and attenuation of the signals in concrete, judges the uniformity of aggregate distribution, and adjusts vibration time, material placement speed, concrete slump, etc. in data feedback and adjustment. Optical imaging technology uses a high-definition camera to photograph the concrete surface and analyzes the distribution of aggregate through image processing technology. In this embodiment, specifically: other components in the dry mixing process include cement, mineral admixtures, and additives; In this embodiment, specifically: the slump of the fabric during the fabric placement process is controlled at 220-260mm; In this embodiment, specifically: the flatness of the laser leveling technology meets the requirement of error ≤2mm / 2m; In this embodiment, specifically: when a large amount of aggregate is detected in a certain area during data feedback and adjustment, the vibration time of that area can be appropriately extended or the amount of material can be reduced; when a lack of aggregate is detected in a certain area, the amount of material in that area can be appropriately increased or the position of the vibration point can be adjusted.

[0011] Working principle or structural principle: First, select standard raw materials: 450 kg / m³ cement, 1200 kg / m³ quartz sand (0.15-0.6 mm), 2% steel fiber (13 mm diameter, 0.2 mm diameter) by volume, 3% water-reducing agent, and 180 kg / m³ water. After precise measurement, these raw materials are mixed according to the design ratio. Then, crushed stone aggregates with particle sizes of 2.36-4.75 mm, 3-5 mm, and 5-8 mm are selected and mixed in a ratio of 30:40:30. After mixing, the aggregates undergo surface cleaning and pre-wetting treatment to remove mud and powder. Impurities such as oil and dirt are removed, and the moisture content is controlled between 2% and 3%. The pretreated aggregates are then mixed with other components of UHPC using both dry and wet mixing processes. During dry mixing, the mixer speed is controlled at 50 rpm for 3 minutes to ensure thorough and uniform mixing of the aggregates and solid powders. During wet mixing, water and additives are slowly added, and mixing continues for 4 minutes to achieve a homogeneous mixture with good workability. Simultaneously, the temperature of the mixture is controlled below 30°C using the mixer's built-in cooling device or an external circulating water system to prevent excessive temperature from reducing the fluidity of the slurry. If the aggregates expand unevenly due to thermal expansion, after mixing, the concrete mixture is transported to the construction site using a transport vehicle equipped with spiral mixing blades. During transportation, the transport vehicle is kept at a constant speed of 3 r / min to prevent aggregate settlement and segregation. Upon arrival at the site, a placing boom is used to evenly distribute the concrete within the foundation formwork. The placing boom moves at a speed of 1.5 m / min, and the flow rate is adjustable to ensure that each area is evenly covered with the concrete mixture. A 50Hz, 2.0kW immersion vibrator is used to compact the concrete. The vibration points are evenly arranged in a quincunx pattern. Vibrate at 500mm intervals for 25 seconds at each point. During vibration, closely observe the distribution of aggregates. If there is local accumulation or missing aggregates, manually adjust them using specialized tools. Subsequently, use a laser screed to level the concrete surface, ensuring that the surface flatness error is ≤2mm / 2m. During concrete construction, set up 8 monitoring points and use ultrasonic testing technology to monitor the aggregate distribution in real time. Based on the monitoring results, adjust the vibration time, material placement speed, and other construction process parameters in a timely manner to ensure the uniform distribution of aggregates throughout the large-volume concrete structure.

[0012] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A UHPC aggregate uniform distribution precision control method for mass concrete construction, characterized in that, The application relates to a UHPC construction method, which comprises the following steps: S1, aggregate pretreatment, which comprises the following steps: performing multi-stage classification screening on UHPC aggregate, removing particles not meeting the particle size requirement, performing surface cleaning treatment on the aggregate by using a high-pressure water gun or a special cleaning agent to remove mud, oil stains and impurities, and performing pre-wetting treatment on the aggregate before stirring; S2, mixture preparation, which comprises the following steps: adding the pretreated aggregate and other component materials of UHPC into a forced stirrer according to the design ratio to perform a dry mixing process, slowly adding water and an additive, continuously stirring, and performing a wet mixing process; and controlling the mixture temperature by using a cooling device built in the stirrer or an external circulating water system during the stirring process; S3, transportation and distribution, which comprises the following steps: using a concrete stirring special transport vehicle with spiral stirring blades, and uniformly distributing the concrete mixture in a mass concrete foundation template by using a distributor or a distributor with adjustable flow to perform distributor distribution; S4, vibration and leveling, which comprises the following steps: using an inserted vibrator with a frequency of 40-60 Hz and a power of 1.5-2.5 kW to perform low-frequency high-power vibration on the concrete, and using laser leveling technology to perform leveling treatment on the concrete surface; and manually adjusting and closely observing the distribution of the aggregate during the vibration and leveling process; S5, pouring process monitoring, which comprises the following steps: setting multiple monitoring points to perform multi-technology monitoring during the pouring process of the mass concrete, using ultrasonic detection technology, resistivity detection technology or optical imaging technology to monitor the distribution of the UHPC aggregate in the concrete in real time, feeding back and adjusting data, and timely adjusting construction process parameters according to the monitoring data.

2. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 1, characterized in that: In the classification screening, gravel aggregate with particle sizes of 2.36-4.75 mm, 3-5 mm and 5-8 mm is selected, and the gravel aggregate is mixed according to a weight ratio of 30:40:30, so that the aggregate gradation is optimized; in the surface cleaning, the surface of the aggregate is ensured to be free of substances affecting the adhesion of the aggregate and the cement paste, and the mud content is controlled to be less than 0.5%; and in the pre-wetting treatment, the water content is controlled to be 2%-3%, so that the water absorption of the aggregate during the stirring process is reduced, and the paste fluidity is prevented from being reduced.

3. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 2, characterized in that: In the dry mixing process, the stirring speed of the stirrer is controlled to be 40-60 rpm, and the dry mixing time is not less than 3 minutes, so that the aggregate and the solid powder are fully and uniformly mixed; in the wet mixing process, the total stirring time is controlled to be 5-7 minutes, and the wet mixing stage is not less than 2 minutes, so that the mixture is uniformly consistent and has good workability, and the paste can fully wrap the aggregate.

4. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 3, characterized in that: In the transportation process of the special transport vehicle, the transport vehicle is kept rotating at a uniform speed, and the rotating speed is controlled to be 2-4 r / min, so that the aggregate is prevented from being precipitated and separated; and in the distributor distribution, the moving speed and the distribution range of the distributor are adjusted according to the concrete slump and the pouring area size, so that each part can be uniformly covered.

5. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 4, characterized in that: In the low-frequency high-power vibration, the vibration points are evenly arranged in a quincunx pattern with a spacing of no more than 500mm. The vibration time should be until the concrete surface is covered with slurry and no more large amounts of air bubbles emerge. Generally, the vibration time for each vibration point is 20-30 seconds to avoid over-vibration or under-vibration. In the laser leveling technology, the laser leveling machine controls the leveling accuracy by emitting a laser beam to ensure that the flatness of the concrete surface meets the requirements. In the manual adjustment, if there is local accumulation or missing aggregate, special tools should be used for manual adjustment in a timely manner, such as using a rake to remove the accumulated aggregate or replenish the missing parts.

6. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 5, characterized in that: In the multi-technology monitoring, ultrasonic testing technology transmits and receives ultrasonic signals, analyzes the propagation speed and attenuation of the signals in concrete, and judges the uniformity of aggregate distribution. The data feedback and adjustment include adjusting the vibration time, material placement speed, concrete slump, etc.

7. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 6, characterized in that: Other components in the dry mixing process include cement, mineral admixtures, and additives.

8. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 7, characterized in that: The slump of the fabric laid by the cloth-laying machine is controlled at 220-260 mm.

9. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 8, characterized in that: The flatness of the laser leveling technology meets the requirement of an error ≤2mm / 2m.

10. The UHPC aggregate uniform distribution precision control method for mass concrete construction according to claim 9, characterized in that: In the data feedback and adjustment process, when a large amount of aggregate is detected in a certain area, the vibration time in that area can be appropriately extended or the amount of material laid can be reduced.

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