CN111811934A - Quantitative evaluation method and device for analyzing concrete workability based on bottom resistance - Google Patents
Quantitative evaluation method and device for analyzing concrete workability based on bottom resistance Download PDFInfo
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- CN111811934A CN111811934A CN202010519067.1A CN202010519067A CN111811934A CN 111811934 A CN111811934 A CN 111811934A CN 202010519067 A CN202010519067 A CN 202010519067A CN 111811934 A CN111811934 A CN 111811934A
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- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000011158 quantitative evaluation Methods 0.000 title claims abstract description 12
- 238000012360 testing method Methods 0.000 claims abstract description 65
- 238000006073 displacement reaction Methods 0.000 claims abstract description 36
- 229920003023 plastic Polymers 0.000 claims abstract description 21
- 238000003780 insertion Methods 0.000 claims abstract description 13
- 230000037431 insertion Effects 0.000 claims abstract description 13
- 230000000740 bleeding effect Effects 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 9
- 238000004458 analytical method Methods 0.000 claims description 8
- 206010016807 Fluid retention Diseases 0.000 claims description 5
- 239000002002 slurry Substances 0.000 claims description 4
- 239000004575 stone Substances 0.000 claims description 4
- 238000012512 characterization method Methods 0.000 claims description 3
- 239000000758 substrate Substances 0.000 claims description 3
- 230000000903 blocking effect Effects 0.000 claims 1
- 238000002955 isolation Methods 0.000 claims 1
- 238000005204 segregation Methods 0.000 abstract description 9
- 230000007547 defect Effects 0.000 abstract description 2
- 238000011156 evaluation Methods 0.000 abstract description 2
- 238000010276 construction Methods 0.000 description 8
- 239000003638 chemical reducing agent Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 4
- 239000004568 cement Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000004576 sand Substances 0.000 description 2
- 238000011179 visual inspection Methods 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0641—Indicating or recording means; Sensing means using optical, X-ray, ultraviolet, infrared or similar detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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Abstract
The invention relates to a quantitative evaluation method and a device for analyzing concrete workability based on bottom resistance, wherein the evaluation method comprises the following steps: (1) developing a resistance test of the bottom of the fresh concrete; (2) drawing a curve of the displacement and speed of the resistance test piece along with the change of time; (3) quantitatively evaluating the workability of the concrete based on the bottom resistance condition; the device comprises a transparent plastic box, a resistance test piece, a sliding guide rail and a laser displacement sensor. By adopting the method and the device, the time for inserting the resistance test piece into the bottom of the concrete and the displacement can be accurately measured, then the insertion speed is calculated, a displacement and speed time-varying curve is drawn, and the sinking condition of the fresh concrete aggregate is quantitatively represented through the concrete workability comprehensive coefficient, so that the quantitative evaluation of the concrete workability is realized, and the defect that the concrete segregation degree is difficult to quantitatively represent by the traditional method is overcome.
Description
Technical Field
The invention relates to an experimental method and a device for civil engineering, in particular to a quantitative evaluation method and a device for analyzing concrete workability based on bottom resistance.
Background
In civil engineering construction, in order to obtain a dense and uniform concrete structure and facilitate construction operations (processes of mixing, transporting, pouring, vibrating, etc.), it is required that fresh concrete must have good workability, called workability of concrete. The fresh concrete has the typical poor workability phenomena of layering, segregation, bleeding and the like. The construction quality of the concrete is a key foundation of engineering quality, so the workability evaluation of the concrete is particularly important to the engineering quality and the engineering safety.
The content of the workability of the concrete mixture is complex, and the concrete mixture is difficult to be comprehensively and properly expressed by a simple measuring method and indexes. At present, the fluidity can be quantitatively measured through experiments, the fluidity of concrete is generally expressed by consistency, and the determination method comprises slump and Veeberg consistency methods. The cohesiveness can also be measured indirectly by measuring the plastic viscosity and yield stress of fresh concrete by using a rotary rheometer. However, the conditions for measuring the rheological property of the concrete by the concrete rheometer are harsh, the expensive price and the huge equipment volume of the concrete rheometer limit the application range of the concrete rheometer in a laboratory, and the concrete rheometer is difficult to economically and rapidly carry out on a construction site. Therefore, the cohesiveness and the water retention of fresh concrete are basically evaluated on a construction site by visual inspection and construction experience at present, the currently used visual inspection experience method is not accurate, and the test result often fluctuates greatly along with the difference of testers.
The concrete with poor cohesiveness is easy to bleed and separate, generally, the bleeding of the concrete occurs simultaneously, water and slurry float upwards, and the sunken stones are tightly bonded with the substrate, so that the resistance inserted into the bottom of the concrete is greatly increased. Therefore, the quality of the cohesiveness and the water retention of the concrete can be quantitatively judged by quantifying the segregation degree of the concrete.
Therefore, aiming at the occasion with harsh site conditions, in order to quantitatively evaluate the comprehensive workability of the concrete, the invention develops a method and a device for quantitatively evaluating the workability of the concrete based on bottom resistance analysis. By adopting the method to analyze the fresh concrete, the real-time insertion displacement and speed of the concrete bottom in different states can be obtained through a bottom resistance test, the sinking condition of the aggregate of the fresh concrete is quantified, and the comprehensive working performance of the fresh concrete is further quantitatively analyzed. The method has important academic significance and engineering application value for comprehensively and rapidly analyzing and evaluating the workability of the concrete under the conditions of a construction site, a mixing plant and the like.
Disclosure of Invention
In order to quickly evaluate the cohesiveness and the water-retaining property of fresh concrete, the invention provides a quantitative evaluation method and a quantitative evaluation device for analyzing the workability of concrete based on bottom resistance. The cohesiveness and the water retention of the fresh concrete can be quantitatively evaluated by quantifying the sinking condition of the aggregate of the fresh concrete, and the comprehensive working performance of the concrete is further evaluated by combining slump. The method can measure the insertion displacement and the speed of the concrete bottom in different states through a bottom resistance test under the harsh condition of a site environment, analyze and obtain the concrete workability characterization quantity, and conveniently, quickly and quantitatively evaluate the workability of the fresh concrete.
The invention realizes the aim through the following technical scheme: a quantitative evaluation method for analyzing concrete workability based on bottom resistance comprises the following steps
1. Developing a resistance test of the bottom of the fresh concrete: placing a transparent plastic box on a horizontal table, filling the uniformly stirred fresh concrete, removing the redundant concrete on the surface of the box body, fully vibrating, and placing a resistance testing device for a bottom resistance testing test.
2. Drawing a resistance test piece speed change curve along with time: recording the displacement of the resistance test piece and the corresponding time of the displacement, drawing a curve of the displacement of the resistance test piece changing with time, and further drawing a curve of the speed of the resistance test piece changing with time by carrying out derivation analysis on the curve.
3. Quantitatively evaluating concrete workability based on bottom resistance conditions: and based on a resistance test piece displacement time-varying curve determined by a bottom resistance test, solving a concrete workability comprehensive coefficient by using a concrete workability comprehensive coefficient calculation model, and evaluating the workability of the concrete.
The concrete workability comprehensive coefficient calculation model is that the interval with v more than 100mm/s is taken for integral calculation:
wherein W is the concrete workability comprehensive coefficient, n is the interval number, ti1Is the starting point of the interval, ti2An interval end point, i ═ 1, 2.., n; .
The water and the slurry for separating the bleeding concrete float upwards, the settled stones are tightly bonded with the substrate, the bottom of the stone can generate the barrier effect of the aggregate, and the separation degree of the concrete is judged according to the settlement degree of the aggregate, so that the cohesiveness and the water-retaining property of the workability of the concrete are quantitatively evaluated.
A device suitable for the concrete workability quantitative evaluation method based on bottom resistance analysis comprises a transparent plastic box, a resistance test piece, a sliding guide rail and a laser displacement sensor, wherein the sliding guide rail consists of a guide rail and a fixed handle, the fixed handle at the tail part of the resistance test piece is connected with a pulling handle through a spring, the top part of the resistance test piece is connected with the pulling handle through the guide rail, the laser displacement sensor is arranged on a sensor base, the laser of the sensor returns after being emitted to a reflecting screen, the sensor is connected into a computer through a data line and a USB interface, an analog signal is converted into a digital signal, experimental data is obtained through the computer, then a speed change curve of the resistance test piece along with time is drawn, and concrete workability characterization quantity can be obtained through calculation.
The device on be equipped with laser displacement sensor, can the displacement change between accurate survey laser displacement sensor and the reflecting screen, the precision is 1mm, and the frequency is 10 ~ 30hz, can gather displacement change under the instantaneous insertion condition, laser displacement sensor links to each other with the computer, borrows to realize inserting the real-time data record of overall process by the computer.
The invention has the outstanding advantages that:
the quantitative evaluation method and the experimental device thereof for the workability of the concrete without being limited by a use place are provided, the bottom sinking condition of the fresh concrete aggregate can be quantified, and the cohesiveness and the water retention of the concrete can be quantitatively evaluated; the instantaneous insertion displacement and speed of the bottom of the fresh concrete can be accurately obtained, and the sinking condition of the aggregate of the fresh concrete can be accurately quantified; the invention has simple and rapid experimental process and accurate and convenient data recording. The defect that the segregation and bleeding of the concrete cannot be quantitatively evaluated by a traditional slump method is overcome, the segregation and bleeding condition of the concrete is quantitatively represented by a concrete workability comprehensive coefficient calculation model, and the method has important academic significance and engineering application value for comprehensively evaluating and judging the workability of the fresh concrete under the conditions of field test and the like in engineering construction.
Drawings
Table 1 shows the mix ratios and the test results of a plurality of concrete in different workability states.
FIG. 1 is a schematic view showing a state before insertion of the resistance testing device in example 1.
FIG. 2 is a schematic view showing the resistance testing device of example 1 after insertion.
FIG. 3 is a graph showing the displacement of the group A resistive force test pieces in example 1 as a function of time.
FIG. 4 is a graph showing the displacement of the group B resistance test pieces in example 1 as a function of time.
FIG. 5 is a graph showing the velocity profile of the A group of resistance test pieces in example 1 with respect to time.
FIG. 6 is a graph showing the velocity of the B-group resistance test pieces in example 1 as a function of time.
Reference numerals: the device comprises fresh concrete to be tested 1, a transparent plastic box 2, a flat plate 3, a resistance test piece 4, a box bottom opening 5, a spring 6, a pulling handle 7, a sensor module plate 8, a USB interface 9, a data line 10, a waterproof shell 11, a sensor laser emitting head 12, a sliding guide rail 13, a spring hook 14, a fixed handle and a laser reflection screen 15.
Detailed Description
The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and examples.
Example 1
The embodiment is a quantitative assessment method for concrete workability based on bottom resistance analysis, which comprises the following steps:
(1) developing a resistance test of the bottom of the fresh concrete:
mixing water, cement, sand, gravel and a water reducing agent in proportion to prepare fresh concrete for later use, wherein the compounding ratio is shown in table 1.
TABLE 1 concrete mix proportion
The water-cement ratio of the group A is 0.45, the water-cement ratio of the group B is 0.49, the sand rates of the two groups are 44%, the biggest difference is that the mixing amount of the water reducing agent of the group A is far larger than that of the water reducing agent of the group B, and the excessive water reducing agent can cause serious segregation and bleeding of concrete.
And (3) placing the transparent plastic box on a horizontal table, pouring a proper amount of fresh concrete into the transparent plastic box until the transparent plastic box is filled, and wiping the side surface of the transparent plastic box. And (3) vibrating the transparent plastic box on a vibrating table until the volume of the concrete is not changed any more, discharging air bubbles on the surface, scraping the top concrete and cleaning the redundant slurry on the surface of the transparent plastic box. And (3) putting the transparent plastic box on the horizontal table again, wiping the side surface of the transparent plastic box, and observing the distribution condition of the concrete aggregate in the transparent plastic box through the transparent panel again, wherein the filling state is good. The resistance testing device is used for unfolding a bottom resistance testing test: placing the resistance test piece at the bottom opening of the transparent plastic box, taking off the plug at the opening, pressing the head of the resistance test piece close to the bottom of the concrete and inserting the head of the resistance test piece into the concrete for 2mm, keeping the ruler body horizontal with the bottom of the transparent plastic box, and pulling the spring on the device to the bottom of the guide rail, as shown in figure 1. The hand was then quickly released and the insertion test was performed as shown in fig. 2.
(2) Drawing a resistance test piece speed change curve along with time:
the sensor collects the displacement change value of the resistance test piece along with time, and calculates the insertion real-time speed. And (3) drawing a curve graph of the relationship between the displacement and the speed of the resistance test piece and the time in the test process, as shown in fig. 3 and 4.
(3) Quantitatively evaluating concrete workability based on bottom resistance conditions:
according to the speed variation curve with time of the test result of the bottom resistance test, the following is calculated: the concrete workability complex factor W of group a was 45mm, corresponding to a slump of 200mm, an extension of 640 x 520, and it was observed that the concrete had developed severe segregation bleeding. The overall concrete workability factor W for group B was 71mm, corresponding slump was 200mm, and spread was 450mm 470mm, and good concrete workability was observed.
Multiple sets of experiments were performed in the same procedure and the results are shown in the following table:
TABLE 1
The experimental result shows that the workability state of the concrete is changed by changing the form of the dosage of the water reducing agent under the condition of the same mixing proportion. Along with the increase of the mixing amount of the water reducing agent, the concrete state is changed from poor fluidity to good workability, and then serious segregation and bleeding occur. The test result value of the method is continuously reduced along with the aggravation of the concrete segregation and bleeding condition, and the method has good discrimination and can better quantitatively evaluate the workability of the concrete.
Example 2
Referring to fig. 1 and fig. 2, the apparatus for quantitatively evaluating the workability of concrete based on the bottom resistance analysis according to the present invention is composed of fresh concrete to be measured 1, a transparent plastic box 2, a flat plate 3, a resistance test piece 4, a box bottom opening 5, a spring 6, a pulling handle 7, a sensor module plate 8, a USB interface 9, a data line 10, a waterproof case 11, a sensor laser emitting head 12, a sliding guide rail 13, a spring hook 14, a fixed handle, and a laser reflection screen 15, and has a specific structure and a connection mode:
the flat plate 3 is laid on a horizontal ground or a table top, the transparent plastic box 2 filled with the fully vibrated and static concrete is placed in the cavity of the flat plate after the laying is finished, and the inner bottom surface of the box body is flush with the surface of the flat plate 3. The resistance test piece 4, the fixed handle and the laser reflecting screen 15 are connected to the sensor module plate 8 through the spring 6 and the sliding guide rail 13, the resistance test piece 4, the sensor module plate 8 and the pulling handle 7 form a whole, and two ends of the spring 6 are respectively hung on the spring hook 14. Pulling handle 7 to the bottom, will fix handle and laser-beam reflecting screen 15 and hug closely transparent plastic case 2, loosen the handle, the spring can promote resistance test piece 4 and insert the concrete bottom, and sensor laser emission head 12 will record displacement information, is connected the computer with USB interface 9 via data line 10, and the computer will record experimental overall process data.
The device is provided with a laser displacement sensor, can accurately measure the displacement change between the resistance test piece 4 and the fixed end, has the precision of +/-1 mm and the frequency of 10-30 hz, and can collect data under the condition of instantaneous insertion; the sensor is connected with the computer, and the computer can be used for realizing the real-time data recording of the whole insertion process.
Claims (4)
1. A quantitative assessment method of concrete workability based on bottom resistance analysis is characterized by comprising the following steps:
(1) developing a resistance test of the bottom of the fresh concrete: placing a transparent plastic box on a horizontal table, filling the uniformly stirred fresh concrete, removing the redundant concrete on the surface of the box body, fully vibrating, and placing a resistance testing device for a bottom resistance testing test;
(2) drawing a resistance test piece speed change curve along with time: recording the displacement of the resistance test piece and the corresponding time of the displacement, drawing a curve of the displacement of the resistance test piece along with the change of time, and analyzing the speed and the time of the resistance test piece by deriving the curve so as to draw a curve of the speed of the resistance test piece along with the change of time;
(3) quantitatively evaluating concrete workability based on bottom resistance conditions: based on the resistance test piece displacement time-varying curve determined by the bottom resistance test, the concrete workability comprehensive coefficient is calculated by utilizing the concrete workability comprehensive coefficient calculation model to evaluate the workability of the concrete,
the concrete workability comprehensive coefficient calculation model is that the interval with v more than 100mm/s is taken for integral calculation:
wherein W is the concrete workability comprehensive coefficient, n is the interval number, ti1Is the starting point of the interval, ti2An end point of the interval, i ═ 1, 2.
2. The method for quantitatively evaluating the workability of concrete based on the bottom resistance analysis according to claim 1, wherein the water and slurry for isolating the bleeding concrete float up, the sinking stones are tightly adhered to the substrate, the bottom part generates the blocking effect of the aggregate, and the isolation degree of the concrete can be judged by the sinking degree of the aggregate, thereby quantitatively evaluating the cohesiveness and water retention of the workability of concrete.
3. The device is suitable for the quantitative evaluation method for analyzing the concrete workability based on the bottom resistance according to claim 1, and comprises a transparent plastic box, a resistance test piece, a sliding guide rail and a laser displacement sensor, wherein the sliding guide rail is connected with a fixed handle and a laser reflection screen, the fixed handle at the tail part of the resistance test piece is connected with a pulling handle through a spring, the top part of the resistance test piece is connected with the pulling handle through the guide rail, the laser displacement sensor is arranged on a sensor base, the sensor is connected into a computer through a data line and a USB interface, an analog signal is converted into a digital signal, experimental data is obtained through the computer, then a speed change curve of the resistance test piece along with time is drawn, and the concrete workability characterization quantity can be obtained through calculation.
4. The device for the quantitative evaluation method based on the bottom resistance analysis concrete workability according to claim 3, characterized in that a laser displacement sensor is arranged on the device, the displacement change between the laser displacement sensor and the reflecting screen can be accurately measured, the precision is +/-1 mm, the frequency is 10-30 hz, the displacement change under the condition of instantaneous insertion can be collected, the laser displacement sensor is connected with a computer, and the real-time data recording of the whole insertion process can be realized by the computer.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111912746A (en) * | 2020-06-09 | 2020-11-10 | 广西大学 | Quantitative evaluation method for analyzing concrete workability based on bottom resistance |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111912746A (en) * | 2020-06-09 | 2020-11-10 | 广西大学 | Quantitative evaluation method for analyzing concrete workability based on bottom resistance |
| WO2021248881A1 (en) * | 2020-06-09 | 2021-12-16 | 广西大学 | Quantitative evaluation method for analyzing concrete workability on basis of bottom resistance |
| US11630097B2 (en) | 2020-06-09 | 2023-04-18 | Guangxi University | Quantitative evaluation method for workability of concrete based on bottom resistance analysis |
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