Design preparation and construction method of machine-made sand high-throwing self-compacting concrete

Abstract

The invention relates to the technical field of concrete preparation, and discloses a machine-made sand high-throwing self-compacting concrete design and a preparation method thereof, and the machine-made sand high-throwing self-compacting concrete comprises the following components in parts by weight: 500-600 parts of a cementing material, 300-500 parts of cement, 50-150 parts of slag powder, 100-150 parts of fly ash, 20-30 parts of an expanding agent, 200-300 parts of natural sand, 500-600 parts of machine-made sand, 550-600 parts of gravel, and 180-190 parts of water. And 5-10 parts of an additive. According to the concrete mix proportion design method, the machine-made sand with the flaky content smaller than or equal to 4% and the natural sand are innovatively and preferably selected to be compounded as the fine aggregate, the selected coarse aggregate is 5-10 mm in particle size, the absolute volume method is adopted for design, the blank of preparing the high-strength self-compacting concrete from the machine-made sand is filled, and the high-strength self-compacting concrete is prepared. Meanwhile, the Wuhan three-source expanding agent is doped on the original basis, so that the shrinkage of the concrete is reduced, the flowability of the concrete is improved, and the performance of the concrete is improved. The 28d compressive strength of the high-throwing self-compacting concrete prepared by the method is 59.6 MPa, the working performance and strength requirements of the same concrete are ensured, and the problems of the traditional high-throwing high-strength self-compacting concrete in the aspects of bleeding segregation and mixture gap trafficability are solved.

Description

Technical Field

[0001] The invention relates to the field of concrete preparation technology and construction, and specifically to a design, preparation and construction method of machine-made sand high-throw self-compacting concrete. Background Art

[0002] For a long time, ready-mixed concrete enterprises have used natural sand as fine aggregate for concrete. With the continuous development of my country's economy, the volume of construction projects is increasing day by day. The large-scale use of concrete consumes a large amount of natural sand resources. However, as a non-renewable energy, natural sand is a valuable environmental resource that has the function of conserving water and protecting the environment. If it is used endlessly, it will eventually be exhausted, which will not only cause geological disasters such as river bank collapse, but also cause great damage to the ecological resources of rivers and coastal areas. Machine-made sand is rock particles with a particle size of less than 4.75mm made by mechanical crushing and screening after rock mining. Compared with natural sand, it has the characteristics of hard texture, rough and porous surface, sharp edges and corners, and good bonding performance in concrete. Its various physical performance indicators such as fineness modulus, apparent density, bulk density, porosity, etc. are similar to those of natural sand. It is a more suitable material to replace part of natural sand, and its cost is much lower than that of natural sand, and it has a good application prospect. At present, artificial sand has been used in large quantities in concrete to replace part of natural sand, which not only delays the process of resource depletion, but also protects the environment. As a substitute for natural sand, artificial sand is a major trend in social development.

[0003] According to the previous data query, high-throw self-compacting concrete is mainly made by selecting excellent performance machine-made sand and natural sand as fine aggregates, and reasonably designing the mix ratio to enhance the fluidity of concrete, so that it will not have water seepage, segregation and other phenomena in the process of high-altitude throwing, and it can achieve self-leveling and quickly fill the steel pipe column without vibration or less vibration, and only use the kinetic energy generated in the process of high-altitude throwing. When machine-made sand and natural sand are compounded to configure self-compacting concrete, compared with the use of natural sand to configure self-compacting concrete, more slurry is required, that is, the amount of cementitious materials needs to be increased, so that the slurry wraps the surface of the machine-made sand and improves the fluidity of the concrete mixture. Therefore, in the mix ratio design, the strength is improved by the slurry, and the slurry phase is used as the main load-bearing system, that is, the amount of slurry is increased, and the limitation of aggregate strength on concrete strength is reduced. Aggregates are mainly used to fill the void ratio of concrete. Cement, fly ash, mineral powder, etc. are used to improve strength, expansion agent is used to enhance the shrinkage resistance of concrete, machine-made sand with a flaky particle content of less than 4% is used as fine aggregate and natural sand is used as coarse aggregate, and ordinary 5-10mm crushed stone is used as coarse aggregate to configure high-throw self-compacting concrete. Overall, the absolute volume method is used for mix design, trial mixing and testing based on the "Technical Specifications for the Application of Self-Compacting Concrete". Summary of the invention

[0004] The purpose of the present invention is to provide a method for designing and constructing machine-made sand high-throw self-compacting concrete.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a design, preparation and construction method of machine-made sand high-cast self-compacting concrete, comprising the following steps.

[0006] S1. Obtain raw materials: 500-600 parts of cementitious materials, 300-500 parts of cement, 50-150 parts of slag powder, 100-150 parts of fly ash, 10-50 parts of expansion agent, 200-300 parts of natural sand, 500-600 parts of machine-made sand, 550-600 parts of 5-10 mm crushed stone, 180-190 parts of water, and 5-10 parts of admixture.

[0007] S2. Add all powders and expanders first, and dry mix for 5 minutes to allow all powders to fully open and stir well.

[0008] S2. Add all powders and expanders first, and dry mix for 5 minutes to allow all powders to fully open and stir well.

[0009] S4. Finally, add water and admixtures and stir for 5 minutes.

[0010] Preferably, PO 42.5 cement is selected, and its core indicators are: 3-day strength 30.4 MPa, 28-day strength 55.1 MPa.

[0011] Preferably, S95 grade slag powder is selected, and its core indicators are: 7-day activity index 75%, 28-day activity index 98%.

[0012] Preferably, Class F II fly ash is selected, and its core indicators are: fineness 25.6%, loss on ignition 3.5%, and water requirement ratio 95%.

[0013] Preferably, Wuhan Sanyuan expansion agent is selected, and its core indicators are: fineness 220m 2 / kg, the limited expansion rate in water for 7 days is 0.650%, and the limited expansion rate in air for 21 days is -0.002%.

[0014] The preferred fine aggregate (limestone crushing and sand making) has the following core indicators: fineness modulus 2.8, stone powder content 4.2%, MB value 0.75, crushing value 23.2%, and flake content 4%.

[0015] The preferred fine aggregate (natural sand) has the following core indicators: fineness modulus 2.0 and mud content 5.9%.

[0016] The preferred coarse aggregate (crushed stone) has the following core indicators: particle size 5-10mm, mud content 0.2%, mud block content 0.1%, and apparent density 2670kg / m³.

[0017] The present invention provides a design, preparation and construction method of machine-made sand high-throw self-compacting concrete, which has the following beneficial effects.

[0018] In the present invention, in terms of the preferred raw materials, machine-made sand with a flaky particle content of less than 4% is openly selected to be compounded with natural sand to form the medium sand in zone II. Different from other methods of selecting materials for high-cast self-compacting concrete, the absolute volume method is adopted for design to reduce the amount of natural sand, thus breaking through the difficult problem of high cost of preparing high-strength high-cast self-compacting concrete with machine-made sand. At the same time, selecting flaky particles of less than 4% can ensure that the concrete has good fluidity and compactness, which is beneficial to improving the strength of the concrete and solving the problems of water segregation and interstitial permeability of the traditional high-cast self-compacting concrete.

[0019] In the present invention, Wuhan Sanyuan expansion agent is introduced to limit the shrinkage of concrete under the premise that the strength meets the requirements, so that the strength and shrinkage deformation of concrete are developed in a coordinated manner. Secondly, starting from the mix ratio, it is ensured that the high-throw self-compacting concrete has excellent workability, and there is no segregation or bleeding after being thrown from a height of 13 meters, forming a complete set of design, configuration and production of machine-made sand high-throw self-compacting concrete, so that the high-throw self-compacting concrete is successfully applied.

[0020] Figure 1 This is a graph showing the influence of water-cement ratio on the 28d compressive strength of machine-made sand high-cast self-compacting concrete in the comparative test of the present invention.

[0021] Figure 2 This is a graph showing the influence of the needle-like content of machine-made sand on the 28d compressive strength of machine-made sand high-cast self-compacting concrete in the comparative test of the present invention.

[0022] Figure 3 This is a graph showing the influence of the amount of cement replaced by the three-source expansion agent on the 28d compressive strength of the machine-made sand high-cast self-compacting concrete in the comparative test of the present invention.

[0023] Figure 4 This is a construction site diagram of the solid structure of the machine-made sand high-throw self-compacting concrete test column of the present invention.

[0024] Experimental example.

[0025] A design, preparation and construction method of machine-made sand high-throw self-compacting concrete comprises the following steps.

[0026] S1. Obtain raw materials: 500-600 parts of cementitious materials, 300-500 parts of cement, 50-150 parts of slag powder, 100-150 parts of fly ash, 10-50 parts of expansion agent, 200-300 parts of natural sand, 500-600 parts of machine-made sand, 550-600 parts of 5-10 mm crushed stone, 180-190 parts of water, and 5-10 parts of admixture.

[0027] S2. Add all powders and expanders first, and dry mix for 5 minutes to allow all materials to fully open and mix well.

[0028] S3. Then add fine aggregate and coarse aggregate and stir for 5 minutes.

[0029] S4. Finally, add water and admixtures and stir for 5 minutes.

[0030] The water-binder ratio in high-strength self-compacting concrete has a great influence on the performance of concrete. The expansion, slump and strength of concrete are closely related to the water-binder ratio. Therefore, choosing a reasonable water-binder ratio is the guarantee of strength and working performance. On the basis of a certain cementitious material, the smaller the water-binder ratio, the smaller the fluidity of the concrete, and it cannot achieve self-leveling, and the compactness of the self-compacting concrete cannot be guaranteed; if the water-binder ratio is too large, the cohesion and water retention of the concrete will be reduced, thereby reducing the strength of the concrete. Therefore, the determination of the water-binder ratio is a key point in the design of high-strength self-compacting concrete. In order to determine the water-binder ratio, it was determined by designing multiple groups of comparative tests, so the water-binder ratios of 0.29, 0.31, 0.33 and 0.35 were selected for trial mixing, and the influence of different water-binder ratios on the performance of high-strength self-compacting concrete was studied.

[0031] The particle shape of the raw material fine aggregate in high-cast self-compacting concrete has a great influence on the fluidity of concrete. Therefore, the flaky particle content of fine aggregate-mechanical sand in concrete is in accordance with the highest requirements in "Aggregates for High Performance Concrete" (JG / T 568-2019) and "Standard for Quality and Test Methods of Sand and Stone for Ordinary Concrete" (JGJ52-2006). Artificial sand with flaky particle contents of 2%, 4%, 6% and 8% are selected and compounded with natural sand, respectively. The influence of different flaky particle contents on the performance of high-cast self-compacting concrete is studied.

[0032] In order to overcome the defect of large concrete shrinkage, high-cast self-compacting concrete is added with a certain amount of Wuhan Sanyuan expansion agent to compensate for the shrinkage of concrete. In the present invention, the internal mixing method of replacing the cement dosage is selected, and the expansion agent dosage of 4%, 6%, 8%, and 10% is selected to replace the cement dosage, and the influence of different expansion agent dosages on the performance of high-cast self-compacting concrete is studied.

[0033] Through on-site trial mixing and adjustment, the final mix ratio was determined as: 320 parts of cement, 100 parts of slag powder, 120 parts of fly ash, 20 parts of expansion agent, 590 parts of machine-made sand with flaky particle content less than 4%, 250 parts of natural sand, 800 parts of 5-10mm particle size gravel, 185 parts of water, and 7.9 parts of admixture.

[0034] The basic properties of the obtained high-strength and high-polished self-compacting concrete are as follows: concrete expansion 755mm, T500 passing time is 3.5s, the difference between slump expansion and J-ring expansion is 10mm, segregation rate is 7%, slump loss in 1h is 20mm, and 28d strength is 59.6MPa.

[0035] In order to ensure that the concrete is fully filled without leaving any voids or air compression during the pouring process, a strict control procedure is specified for this pouring.

[0036] When concrete falls along the pipe wall, it will hang on the pipe wall. When the concrete reaches the bottom, its fluidity will deteriorate. Before pouring, the pipe wall should be fully moistened with water to ensure that the pipe wall is not dry. The moistening water should not be too much. The inner wall area of ​​the steel pipe and the required moistening water consumption should be calculated. The actual moistening water consumption is half or less of the calculated consumption. Tests should be conducted before pouring to confirm that the excess water from moistening is removed by pouring concrete. After the final pouring, ensure that some of the water can be reversed.

[0037] During pouring, the pumping volume should not be too large to ensure that the concrete pouring surface out of the pump is not larger than half of the cross-sectional area of ​​the steel pipe, the concrete slump is controlled between 240mm-260mm, T500 is controlled within 4s, and the expansion is greater than 700mm. If the slump, T500, and expansion are not satisfied, it should be stopped immediately and the admixtures should be used on site to adjust the concrete workability to meet the requirements before pouring. The concrete should be controlled within 3 hours from leaving the factory to completion of pouring, and the frequency and volume of concrete transportation should be determined according to the on-site pouring conditions.

[0038] When pouring, the concrete should be allowed to slide along one side of the pipe wall. Since there is no vent hole at the bottom of the steel pipe, the concrete must not fall directly from the top to the bottom to prevent air compression or collapse during the fall.

[0039] Ensure that the same volume of steel columns are poured at the same time. Record the time from the start of pouring to the completion of each steel pipe, and use the pouring time to verify whether there is collapse. If the same volume of steel pipes are poured in the same time period, it means that there is no collapse.

[0040] During the pouring process, the steel columns should be hit with a rubber hammer or a wooden hammer to use the sound to determine whether the concrete is poured densely.

[0041] After pouring, confirm the volume of concrete to see if it is densely poured. If the required volume of concrete is calculated based on the volume of the steel pipe and is greater than the poured volume, it means there is a collapse; if it is less than the poured volume, it means it can be filled densely.

[0042] Precautions: Prepare exhaust steel pipes and vibrators. If there is collapse or air compression, insert the exhaust pipe into the collapsed position, and after the concrete is filled densely, use a vibrator to vibrate to ensure that the concrete is filled densely.

[0043] In order to control concrete segregation and enhance the adhesion between the new and old concrete structures, the pouring height of the first section of steel tube concrete should be controlled at about 1m. After the bottom layer of concrete is poured, the pouring height will be increased to 5m.

[0044] In order to ensure the self-compacting effect of the concrete throwing process and ensure that the bubbles in the concrete are completely overflowed, the next section of construction will be carried out after the concrete thrown into the steel pipe column no longer bubbles obviously and basically reaches the same level.

[0045] The inner wall of the poured steel pipe column is bound to be contaminated by concrete. It must be cleaned before the initial setting of the concrete. The concrete surface should be artificially roughened to remove concrete debris before the final setting and the next pouring. A wooden box should be customized with a template to cover the top of the steel pipe column to prevent debris from falling in. For the floating slurry that is not cleaned in time before the initial setting of the concrete, all the floating slurry section concrete should be chiseled out before the next pouring.

[0046] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A design, preparation and construction method of machine-made sand high-throw self-compacting concrete, characterized in that: The mix ratio of the machine-made sand high-throw self-compacting concrete is: 300-400 parts of cement, 50-150 parts of slag powder, 100-150 parts of fly ash, 10-50 parts of expansion agent, 800-900 parts of fine aggregate, 750-850 parts of coarse aggregate, 180-190 parts of water, and 5-10 parts of admixture.

2. The design, preparation and construction method of a machine-made sand high-cast self-compacting concrete according to claim 1 is characterized in that: The mix ratio of the machine-made sand high-throw self-compacting concrete is: 320 parts of cement, 100 parts of slag powder, 120 parts of fly ash, 20 parts of expansion agent, 590 parts of machine-made sand with a flaky particle content of less than 4%, 250 parts of natural sand, 800 parts of crushed stone with a particle size of 5-10mm, 185 parts of water, and 7.9 parts of admixture.

3. The design, preparation and construction method of a machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: The cementitious material selected is P·0 42.5 cement, and its core indicators are: 3-day strength 30.4MPa, 28-day strength 55.1MPa; the S95 grade slag powder is selected, and its core indicators are: 7-day activity index 75%, 28-day activity index 98%; the F-class II grade fly ash is selected, and its core indicators are: fineness 25.6%, ignition loss 3.5%, water demand ratio 95%; Wuhan Sanyuan expansion agent, its core indicators are: fineness 220m 2 / kg, the limited expansion rate in water for 7 days is 0.650%, and the limited expansion rate in air for 21 days is -0.002%.

4. The design, preparation and construction method of a machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: The core indicators of fine aggregate (made from waste materials, slag, stone powder and other waste resources such as limestone quarries, through mechanical crushing, washing and screening) are: fineness modulus 2.8, stone powder content 4.2%, MB value 0.75, crushing value 23.2%, flake content 4%; the core indicators of fine aggregate (natural sand) are: fineness modulus 2.0, mud content 5.9%.

5. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: The core indicators of coarse aggregate (crushed stone) are: particle size 5-10mm, mud content 0.2%, mud block content 0.1%, and apparent density 2670kg / m³.

6. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: When concrete falls along the pipe wall, it will hang on the pipe wall. When the concrete reaches the bottom, its fluidity will deteriorate. Before pouring, the pipe wall should be fully moistened with water to ensure that the pipe wall is not dry. The moistening water should not be too much. The inner wall area of ​​the steel pipe and the required moistening water consumption should be calculated. The actual moistening water consumption is half or less of the calculated consumption. Tests should be conducted before pouring to confirm that the excess water from moistening is removed by pouring concrete. After the final pouring, ensure that some of the water can be reversed.

7. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: During pouring, the pumping volume should not be too large to ensure that the concrete pouring surface out of the pump is no larger than half of the cross-sectional area of ​​the steel pipe, the concrete slump is controlled between 240mm-260mm, T500 is controlled within 4s, and the expansion is greater than 700mm. If the slump, T500 and expansion are not satisfied, the work should be stopped immediately and the admixture should be used on site to adjust the concrete workability to meet the requirements before pouring. The time from the concrete leaving the factory to the completion of pouring should be controlled within 3 hours, and the frequency and volume of concrete transportation should be determined according to the on-site pouring conditions.

8. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: When pouring, the concrete should be allowed to slide along one side of the pipe wall. Since there is no vent hole at the bottom of the steel pipe, the concrete must not fall directly from the top to the bottom to prevent air compression or collapse during the fall.

9. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: Ensure that the same volume of steel columns are poured at the same time. Record the time from the start of pouring to the completion of each steel pipe, and use the pouring time to verify whether there is collapse. If the same volume of steel pipes are poured in the same time period, it means that there is no collapse.

10. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: During the pouring process, the steel columns should be hit with a rubber hammer or a wooden hammer to use the sound to determine whether the concrete is poured densely.

11. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: After pouring, confirm the volume of concrete to see if it is densely poured. If the required volume of concrete is calculated based on the volume of the steel pipe and is greater than the poured volume, it means there is a collapse; if it is less than the poured volume, it means it can be filled densely.

12. The design, preparation and construction method of machine-made sand high-cast self-compacting concrete according to claim 1 is characterized by: Precautions: Prepare exhaust steel pipes and vibrators. If there is collapse or air compression, insert the exhaust pipe into the collapsed position, and after the concrete is filled densely, use a vibrator to vibrate to ensure that the concrete is filled densely.

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