Rockfill concrete filling evaluation method

Abstract

The invention belongs to the field of concrete construction quality detection, and particularly provides a rockfill concrete filling evaluation method which comprises the following steps: determining particle size and particle size distribution according to rockfill to be detected and evaluated, performing particle size reduced scale adjustment according to the particle size distribution of the rockfill, and naturally stacking the rockfill subjected to the reduced scale in a mold; the self-compacting concrete is mixed according to the mixing ratio, and the self-compacting performance and the apparent density of the self-compacting concrete are detected; pouring self-compacting concrete to be detected and evaluated from the top of the mold until the self-compacting concrete horizontally penetrates through the rock-fill gap and fills the rock-fill gap; removing the mold after the concrete is coagulated and hardened, observing the pouring condition of the test piece, and calculating the defect rate; and providing a control standard for the defects, if the defects are not qualified, adjusting the self-compacting performance of the self-compacting concrete, and repeating the operation until the self-compacting concrete is qualified. According to the method, rock-fill concrete pouring is simulated for detection and evaluation, reliable parameters are provided for actual construction of the small-particle-size rock-fill concrete, and therefore the quality of the small-particle-size rock-fill concrete is effectively controlled.

Description

Technical Field

[0001] The present invention belongs to the field of concrete construction quality detection, and in particular relates to a rockfill concrete filling evaluation method. Background Art

[0002] Rockfill concrete dams, a new dam-building technology invented in my country and internationally recognized, have seen rapid development both domestically and internationally in recent years. As of July 2023, over 160 rockfill concrete dams were under construction. Rockfill concrete involves stacking large-sized rocks directly into a silo. Highly self-compacting concrete is then poured onto the surface of the rockfill. Leveraging the high fluidity and filling properties of self-compacting concrete, the concrete's weight completely fills the voids within the rockfill, creating a complete, dense concrete material that meets strength requirements. To ensure the density of rockfill concrete, and based on the self-compacting properties of existing self-compacting concrete, current hydropower and water conservancy industry standards require a minimum rockfill particle size of no less than 300mm. However, the handling and utilization of large amounts of excavation slag generated by pumped-storage power stations is currently a major challenge during construction. The greatest advantage of rockfill concrete technology is its ability to utilize large quantities of natural rock as a dam construction material. Therefore, using slag as rockfill concrete can significantly reduce the amount of rockfill concrete used in dams while also maximizing the use of difficult-to-treat slag, resulting in significant economic and environmental benefits. However, in actual projects, there remains a lack of specific methods for determining whether slag can be used in rockfill concrete, and once this is confirmed, how to design an optimal mix ratio. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a rockfill concrete filling evaluation method, which simulates the pouring of rockfill concrete to perform detection and evaluation, judge whether the slag material can be used for rockfill concrete pouring, and provide reliable parameters for the actual construction of small-particle rockfill concrete, thereby achieving effective control of its quality.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a method for evaluating rockfill concrete filling, comprising the following steps: Step 1: Determine the particle size and particle size distribution of the rockfill to be tested and evaluated, and adjust the particle size scale according to the particle size distribution of the rockfill; Step 2: Mix the self-compacting concrete according to the mix ratio, test the self-compacting performance and apparent density of the self-compacting concrete, and determine the aggregate ratio, which is the ratio of the rockfill particle size to the maximum aggregate particle size in the self-compacting concrete; Step 3: The scaled rockfill is naturally piled in the mold, and the self-compacting concrete to be tested and evaluated is continuously poured at a uniform speed from the top of the mold until the self-compacting concrete horizontally penetrates and fills the gaps between the rockfill, and the top of the mold is smoothed; Step 4: After the concrete solidifies and hardens, remove the formwork, observe the pouring conditions of the specimens, and calculate the defect rate; Step 5: Propose control standards for defects. If the defects are unqualified, adjust the self-compacting performance of the self-compacting concrete and repeat steps 2 to 4 until they are qualified. After passing, determine whether the rockfill particle size can be applied to actual projects and determine the corresponding self-compacting concrete mix ratio.

[0005] In a preferred solution, in step 2, the mold is an "L"-shaped structure, including a vertical section and a horizontal section. The top of the vertical section is open and serves as a pouring port, and the top of the horizontal section is open and serves as an observation port.

[0006] In a preferred solution, the cross-sectional side length of the mold is greater than three times the particle size of the scaled-down rockfill, and the horizontal length of the mold is not less than 2 m.

[0007] In a preferred solution, in step 2, the self-compacting performance of the self-compacting concrete is detected, including detecting the expansion degree and detecting the V-funnel passing time.

[0008] In a preferred solution, in step 2, the rockfill concrete has a rockfill-brick ratio of 6:1 to 10:1.

[0009] In a preferred solution, the performance range of the self-compacting concrete is: VF=0-19s, SF=700-950, wherein VF represents the V funnel passage time and SF represents the expansion degree.

[0010] In a preferred solution, in step 4, the defect rate of rockfill concrete is calculated as follows: ; Where: P —Defect rate of rockfill concrete; m 0—mold weight; m 1—Total weight of mold and rockfill material; m 2—Total weight of mold, rockfill, and self-compacting concrete; ρ c —apparent density of self-compacting concrete; ρ R —Apparent density of rockfill materials; V —Mold volume.

[0011] In a preferred solution, in step five, the defect control standard is: defect rate is less than or equal to 4%, which is qualified.

[0012] In a preferred embodiment, in step 5, the method for adjusting the self-compacting performance of the self-compacting concrete is: 1) If the expansion of the self-compacting concrete is too large, reduce the admixture dosage; if the expansion is too small, increase the admixture dosage; if the expansion is good but the surface oozes and sinks to the bottom, reduce the water-cement ratio; if the expansion meets the requirements, test the V-funnel passage time; if it is ineffective or oozing occurs, observe the workability: if the encapsulation is poor and the coarse aggregate is obviously exposed, reduce the aggregate dosage; if the viscosity is high and there is no obvious aggregate exposure, adjust the water-cement ratio; 2) Check the V-funnel passage time. If it is good, check the plasticity retention performance. If the time is too short, reduce the water-powder ratio. If the time is too long, observe the workability: if the slurry has high dryness and good encapsulation, increase the water-powder ratio; if the aggregate sinks and the slurry has low viscosity, reduce the water-powder ratio; if the aggregate sinks and the slurry has good viscosity, reduce the amount of aggregate; if the flow is discontinuous and the slurry has good viscosity, reduce the amount of aggregate.

[0013] The present invention also provides a mold used in the above-mentioned rockfill concrete filling evaluation method. The mold is an "L"-shaped structure, including a vertical section and a horizontal section. The top opening of the vertical section is a pouring port, and the top opening of the horizontal section is an observation port.

[0014] The present invention provides a method for evaluating rockfill concrete filling, which has the following beneficial effects: 1. Simulated pouring tests of small-grained rockfill concrete were conducted using self-compacting concrete with varying self-compacting properties and small-grained rockfill (simulating slag). The proposed defect rate calculation method was used to determine the defect rate of small-grained rockfill concrete. This comprehensive evaluation of the compactness of small-grained rockfill concrete allowed for a comprehensive assessment of the suitability of slag for rockfill concrete pouring. This simple and low-cost test method, based on the simulated pouring test results, can provide reliable parameters for the actual construction of small-grained rockfill concrete, bringing significant economic benefits to the project.

[0015] 2. A test method is proposed to systematically evaluate the feasibility of rockfill concrete technology at a realistic engineering scale, especially for evaluating the feasibility of small-size rockfill concrete technology, including but not limited to slag. The method can evaluate and analyze the combination of different rockfill particle sizes and self-compacting concrete mix ratios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings and examples: Figure 1 It is the technical roadmap of the present invention; Figure 2 This is the structural diagram of the mold; Figure 3 A roadmap for regulating the expansion of self-compacting concrete; Figure 4 It is the V-funnel time adjustment roadmap for self-compacting concrete; Figure 5 This is the result of pouring small-size rockfill concrete; In the figure: vertical section 1, horizontal section 2, pouring port 101, observation port 201. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] like Figure 1 As shown, a rockfill concrete filling evaluation method includes the following steps: Step 1: Determine the particle size and particle size distribution of the rockfill to be tested and evaluated after screening, as shown in Table 1.

[0019] Table 1 Particle size and gradation of rockfill tested and evaluated

[0020] The particle size scale was adjusted according to the particle size distribution of the rockfill, and the scale was scaled at a ratio of 1:3. The adjusted results are shown in Table 2.

[0021] Table 2 Scaled particle size for rockfill testing and evaluation

[0022] The scaled-down rocks are naturally piled up in the mold, such as Figure 2 As shown, the mold is an "L"-shaped structure, including a vertical section and a horizontal section. The top of the vertical section is open and serves as a pouring port, and the top of the horizontal section is open and serves as an observation port.

[0023] The cross-sectional side length of the mold is greater than three times the particle size of the scaled-down rockfill, and the horizontal length of the mold is not less than 2m.

[0024] Step 2: Mix self-compacting concrete according to the mix ratio, with the mortar containing zero stone volume. Test the self-compacting concrete's self-compacting properties and apparent density. The apparent density of the rockfill is measured according to Section 7.13, "Apparent Density," of the national standard "Pebbles and Crushed Stone for Construction," GBT 14685-2022. If the rockfill particle size is too large, manually crush it into smaller particles for measurement.

[0025] The mix parameters of concrete and mortar are shown in Table 3.

[0026] Table 3 Mix ratio parameters of concrete and mortar

[0027] 1) Determine the aggregate-to-rock ratio, which is the ratio of the rockfill particle size to the maximum aggregate size in the self-compacting concrete. Set the aggregate-to-rock ratio to 6:1 to 10:1. Form pure self-compacting concrete test blocks and measure their compressive strength. Blocks with a strength assurance ratio greater than 90% are considered densely packed. Experimentation and calculations indicate a defect rate of 4.0% at this point, so a 4% defect rate is defined as the acceptable limit for self-compacting concrete.

[0028] 2) Self-compacting concrete pouring experiments were carried out according to Table 2, and the experimental results are shown in Table 4.

[0029] Table 4 Performance range of small rockfill casting and filling

[0030] 3) Based on the above data, the appropriate performance range of pure self-compacting concrete is obtained: VF=0-19s, SF=700-950, where VF represents the V funnel passage time and SF represents the expansion.

[0031] The aggregate ratio was increased to 12:1, that is, the particle size of the stones in the self-compacting concrete was reduced. A set of comparative experiments with aggregate ratios of 6:1 and 12:1 were conducted to determine whether the aggregate ratio was a factor affecting the final performance.

[0032] After the experiment, the experimental results were obtained, as shown in Table 5. It can be seen that the increase in the ratio did not expand the working performance range, especially the expansion range, which was still within the range of SF=700-950. Therefore, the main factor affecting the density of this rockfill filling is the viscosity of the self-compacting concrete.

[0033] Table 5 Working performance range of different ratios of rockfill particle size to maximum particle size of pouring aggregate

[0034] Step 3: Based on the experiment in step 2, the working range of self-compacting concrete in small-size rockfill concrete is obtained: VF = 0-19s, SF = 700-950, and the rockfill concrete pouring experiment is carried out accordingly.

[0035] The self-compacting concrete to be tested and evaluated is poured continuously at a uniform speed from the top of the mold until the self-compacting concrete horizontally penetrates the gaps between the rockfill and fills it, and the top of the mold is smoothed.

[0036] Pour the self-compacting concrete to be tested and evaluated continuously at a uniform rate from the top of the vertical section of the mold until the self-compacting concrete horizontally penetrates and fills the rockfill voids. Smooth the top of the mold and wipe clean any concrete adhering to the outside of the mold. During the pouring process, do not use vibration or knocking to help the self-compacting concrete flow into the rockfill voids.

[0037] Step 4: After the concrete solidifies and hardens, remove the formwork, observe the pouring conditions of the specimens, and calculate the defect rate.

[0038] The defect rate of rockfill concrete is calculated as follows: ; Where: P —Defect rate of rockfill concrete; m 0—mold weight; m 1—Total weight of mold and rockfill material; m 2—Total weight of mold, rockfill, and self-compacting concrete; ρ c —apparent density of self-compacting concrete; ρ R - The apparent density of the rockfill is measured according to the national standard "Pebbles and Crushed Stones for Construction" GBT14685-2022, Section 7.13 "Apparent Density". If the rockfill particle size is too large, the rockfill can be manually crushed into small-sized crushed stones for measurement; V —Mold volume.

[0039] Step 5: Propose control standards for defects. If they fail to meet the standards, adjust the self-compacting properties of the self-compacting concrete and repeat steps 2 to 4 until they meet the standards.

[0040] The method for adjusting the self-compacting properties of self-compacting concrete is: 1) If the expansion of self-compacting concrete is too large, reduce the admixture dosage; if the expansion is too small, increase the admixture dosage; if the expansion is good but the surface oozes and sinks to the bottom, reduce the water-cement ratio; if the expansion meets the requirements, test the V-funnel passage time; if the V-funnel passage time is greater than 1 minute, it is judged to be invalid; if it is invalid or oozing occurs, observe the workability: if the encapsulation is poor and the coarse aggregate is obviously exposed, reduce the aggregate dosage; if the viscosity is high and there is no obvious aggregate exposure, adjust the water-cement ratio.

[0041] Expansion judgment standard: objectively determined based on the self-compacting concrete performance indicators in Section 4.2 "Configuration Performance Indicators" of the industry standard "Construction Specifications for Hydropower and Water Conservancy Rockfill Concrete" DL / T5806-2020. 2) Check the V-funnel passage time. If it is good, check the plasticity retention performance. If the time is too short, reduce the water-powder ratio. If the time is too long, observe the workability: if the slurry has high dryness and good encapsulation, increase the water-powder ratio; if the aggregate sinks and the slurry has low viscosity, reduce the water-powder ratio; if the aggregate sinks and the slurry has good viscosity, reduce the amount of aggregate; if the flow is discontinuous and the slurry has good viscosity, reduce the amount of aggregate.

[0042] V-funnel passing time judgment standard: objectively determined based on the self-compacting concrete performance indicators in Section 4.2 "Configuration Performance Indicators" of the industry standard "Construction Specifications for Hydropower and Water Conservancy Rockfill Concrete" DL / T 5806-2020. After the test is qualified, it is determined that the rockfill particle size can be used in actual engineering and has a corresponding self-compacting concrete mix ratio. The self-compacting performance of the self-compacting concrete corresponding to different rockfill particle sizes is also proposed.

[0043] The experimental results and the process of mix optimization are shown in Table 6. The pouring photos are compared with Figure 5 It can be seen that in the fifth experiment, the self-compacting concrete has been fully adapted, and it is determined that this particle size can be used as rockfill concrete for pouring in actual engineering, and the corresponding self-compacting concrete mix ratio is obtained.

[0044] Table 6 Small-size rockfill concrete pouring data

[0045] After passing the test, it is determined that the rockfill particle size can be applied to actual projects, and the corresponding self-compacting concrete mix ratio is determined.

[0046] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating rockfill concrete filling, characterized in that: The following steps are involved: Step 1: Determine the particle size and particle size distribution of the rockfill to be tested and evaluated, and adjust the particle size scale according to the particle size distribution of the rockfill; Step 2: Mix the self-compacting concrete according to the mix ratio, test the self-compacting performance and apparent density of the self-compacting concrete, and determine the aggregate ratio, which is the ratio of the rockfill particle size to the maximum aggregate particle size in the self-compacting concrete; Step 3: The scaled rockfill is naturally piled in the mold, and the self-compacting concrete to be tested and evaluated is continuously poured at a uniform speed from the top of the mold until the self-compacting concrete horizontally penetrates and fills the gaps between the rockfill, and the top of the mold is smoothed; Step 4: After the concrete solidifies and hardens, remove the formwork, observe the pouring conditions of the specimens, and calculate the defect rate; Step 5: Propose control standards for defects. If the defects are unqualified, adjust the self-compacting performance of the self-compacting concrete and repeat steps 2 to 4 until they are qualified. After passing, determine whether the rockfill particle size can be applied to actual projects and determine the corresponding self-compacting concrete mix ratio.

2. A rockfill concrete filling evaluation method according to claim 1, characterized in that: In the step 2, the mold is an "L"-shaped structure, including a vertical section and a horizontal section. The top of the vertical section is open and serves as a pouring port, and the top of the horizontal section is open and serves as an observation port.

3. The method for evaluating rockfill concrete filling according to claim 2, wherein: The cross-sectional side length of the mold is greater than three times the particle size of the scaled-down rockfill, and the horizontal length of the mold is not less than 2m.

4. The method for evaluating rockfill concrete filling according to claim 1, wherein: In the second step, the self-compacting performance of the self-compacting concrete is tested, including testing the expansion degree and testing the V-funnel passing time.

5. The method for evaluating rockfill concrete filling according to claim 1, wherein: In the step 2, the rockfill concrete has a rockfill ratio of 6:1 to 10:

1.

6. The method for evaluating rockfill concrete filling according to claim 4, characterized in that: The performance range of the self-compacting concrete is: VF=0~19s, SF=700~950, where VF represents the V funnel passage time and SF represents the expansion degree.

7. The method for evaluating rockfill concrete filling according to claim 1, characterized in that: In step 4, the defect rate of rockfill concrete is calculated as follows: ； Where: P —Defect rate of rockfill concrete; m 0—mold weight; m 1—Total weight of mold and rockfill material; m 2—Total weight of mold, rockfill, and self-compacting concrete; ρ c —apparent density of self-compacting concrete; ρ R —Apparent density of rockfill materials; V —Mold volume.

8. The method for evaluating rockfill concrete filling according to claim 1, wherein: In step 5, the defect control standard is: the defect rate is less than or equal to 4%, which is qualified.

9. The method for evaluating rockfill concrete filling according to claim 4, wherein: In step 5, the method for adjusting the self-compacting performance of the self-compacting concrete is: 1) If the expansion of the self-compacting concrete is too large, reduce the admixture dosage; if the expansion is too small, increase the admixture dosage; if the expansion is good but the surface oozes and sinks to the bottom, reduce the water-cement ratio; if the expansion meets the requirements, test the V-funnel passage time; if it is ineffective or oozing occurs, observe the workability: if the encapsulation is poor and the coarse aggregate is obviously exposed, reduce the aggregate dosage; if the viscosity is high and there is no obvious aggregate exposure, adjust the water-cement ratio; 2) Check the V-funnel passage time. If it is good, check the plasticity retention performance. If the time is too short, reduce the water-powder ratio. If the time is too long, observe the workability: if the slurry has high dryness and good encapsulation, increase the water-powder ratio; if the aggregate sinks and the slurry has low viscosity, reduce the water-powder ratio; if the aggregate sinks and the slurry has good viscosity, reduce the amount of aggregate; if the flow is discontinuous and the slurry has good viscosity, reduce the amount of aggregate.

10. A mold used in the rockfill concrete filling evaluation method according to any one of claims 1 to 9, characterized in that: The mold is an "L"-shaped structure, including a vertical section and a horizontal section. The top of the vertical section is open and serves as a pouring port, and the top of the horizontal section is open and serves as an observation port.

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