Method for detecting comprehensive working performance of fresh concrete

Abstract

The method for detecting the comprehensive working performance of the fresh concrete provided by the invention comprises the following steps: pouring the fresh concrete into a certain channel in a detection container which is provided with a plurality of channels and the bottoms of which are communicated with one another, and detecting the comprehensive working performance of the fresh concrete when the liquid level height of the fresh concrete in each channel is kept unchanged, measuring the liquid level height of the concrete in each channel and detecting the quality of the concrete in the container; a discharging opening in the bottom of the detection container is opened, the concrete in the detection container is discharged by means of self weight, in the discharging process, the mass of the discharged concrete or the discharging flow speed of the concrete is measured, and after discharging is completed, a concrete discharging mass-time curve or a concrete discharging flow speed-time curve is obtained; according to a measurement result, a series of indexes including the fluidity, viscosity, uniformity and apparent density of the concrete are obtained through arrangement and conversion and serve as a comprehensive evaluation result of the working performance of the fresh concrete. According to the method, multiple working performance indexes of the concrete can be given at a time, and mutual complementary interpretation can be carried out.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete working performance detection, and in particular relates to a method for detecting the comprehensive working performance of fresh concrete. Background Art

[0002] The working performance of fresh concrete is the most important factor affecting the quality of pouring. It not only directly affects the uniformity and density of concrete molding, but also has an important impact on the quality and service life of engineering construction. The test methods related to the working performance of concrete can be roughly divided into three categories: the first category includes slump test, expansion test, Vebe consistency test and other methods, which are used to evaluate the plasticity and fluidity of concrete working performance, which are mainly closely related to the yield limit of concrete; the second category includes inverted slump cone emptying test, expansion time test, anti-segregation test and other methods, which are used to evaluate the cohesiveness and anti-segregation performance of concrete, which are mainly related to the viscosity coefficient of concrete, and will also be affected to a certain extent by the aggregate particle size and gradation; the third category includes gap passability test and funnel test, which examine the comprehensive state of concrete working performance. Both are based on the performance of concrete flowing through a narrow space to evaluate its working performance. The performance that affects the results of these two tests is relatively comprehensive, usually related to fluidity, viscosity, and aggregate particle size and gradation.

[0003] The working performance of concrete includes its fluidity (plasticity), viscosity, uniformity, anti-segregation and gap permeability. The shortcomings of existing technical means can be summarized as follows:

[0004] (1) Lack of integrated rapid testing methods for various working properties of concrete

[0005] The existing detection methods can only effectively and quantitatively reflect one or two performance indicators in a single test; if an overall evaluation is to be given, it is usually necessary to conduct a variety of different types of detection tests, which will lead to cumbersome operations, inability to strictly control variables due to sampling differences, and incomplete reflection of working performance. There is a lack of simple, fast, comprehensive and quantitative evaluation methods for concrete working performance indicators.

[0006] (2) Lack of description and detection methods for concrete flow process

[0007] Existing detection methods all test and analyze the state of concrete before or after it flows. As concrete is a complex multiphase non-Newtonian fluid, the description of its flow properties is very complex. Therefore, evaluation based solely on indicators before and after the flow often cannot accurately describe its true state. For example, in the concrete V-funnel test, when the passing time is greater than the specified value, it may be due to excessive viscosity, excessive aggregates, or severe segregation. Therefore, only by monitoring and analyzing the entire flow process can the state of concrete be fully and truly described. Summary of the invention

[0008] The present disclosure aims to solve at least one of the technical problems in the related art.

[0009] To this end, the present invention provides a method for detecting the comprehensive performance of fresh concrete, which can solve the problem of one-time rapid detection of multiple working performances of fresh concrete.

[0010] In order to achieve the above objectives, the present disclosure adopts the following technical solutions:

[0011] The present disclosure provides a method for detecting the comprehensive working performance of fresh concrete, comprising the following steps:

[0012] Step S1, pouring fresh concrete into a channel of a detection container having multiple channels and interconnected at the bottom, wherein the fresh concrete flows in the detection container by its own weight and gradually fills each channel; standing for a period of time until the liquid level of the fresh concrete in each channel remains unchanged, taking this as the initial state before unloading, and measuring the liquid level of the fresh concrete in each channel and the mass of the fresh concrete in the detection container;

[0013] Step S2, opening the discharge port at the bottom of the detection container, so that the fresh concrete in the detection container is discharged through the discharge port by its own weight; during the discharge process, measuring the mass of the fresh concrete discharged from the detection container or measuring the discharge flow rate of the fresh concrete, and after the discharge is completed, obtaining a fresh concrete discharge mass-time curve or a fresh concrete discharge flow rate-time curve;

[0014] Step S3, according to the measurement results of step S1 and step S2, a series of indicators of fresh concrete are sorted and converted as a comprehensive evaluation result of the working performance of fresh concrete, wherein the series of indicators include a combination of any multiple indicators of fluidity, viscosity, uniformity and apparent density of fresh concrete.

[0015] In some embodiments, the channel in the detection container is a vertical channel, the minimum side length of the cross section of any channel is not less than 5 times the maximum aggregate particle size of concrete, and the height is not less than 10 times the maximum aggregate particle size of fresh concrete; the channel into which fresh concrete is poured is used as a feeding channel, and the cross-sectional area of ​​the feeding channel is not less than 1.5 times the average cross-sectional area of ​​other connecting channels; the discharge port is composed of a gradually narrowing inclined section and a parallel extension section connected to its lower part, the side length of the discharge port at the smallest diameter is not less than 5 times the maximum aggregate particle size of fresh concrete, and the length of the parallel extension section is not less than 3 times the maximum aggregate particle size of fresh concrete.

[0016] In some embodiments, the liquid level of the fresh concrete in each channel is measured manually, by a sensor, or by image recognition;

[0017] The manual measurement is to manually measure the liquid level of the fresh concrete in the channel using a ruler or scale lines; the sensor measurement is to measure the liquid level of the fresh concrete in the channel using a laser ranging sensor, an ultrasonic ranging sensor or an infrared ranging sensor fixed directly above the channel; the image recognition measurement is to measure the liquid level of the fresh concrete in the channel using a camera and an image recognition method for the detection container made of a transparent material.

[0018] In some embodiments, the mass of the freshly mixed concrete in the detection container is measured by manually recording the reading of an electronic scale placed at the bottom of the receiving container below the discharge port; or by measuring data of a weight sensor fixed at the bottom of the detection container.

[0019] In some embodiments, during the unloading process, the mass of fresh concrete in the detection container or the unloading flow rate of fresh concrete is measured at intervals, and the measurement interval does not exceed 1 / 10 of the total unloading time.

[0020] In some embodiments, the fluidity index and apparent density of the fresh concrete are calculated based on the liquid level height of the fresh concrete in each channel in the initial state before unloading; the viscosity index and uniformity index of the fresh concrete are calculated based on the fresh concrete unloading mass-time curve or the fresh concrete unloading flow rate-time curve during the unloading process.

[0021] In some embodiments, the fluidity index of fresh concrete is 1 f , which is the height of the liquid level of fresh concrete in each channel at the initial state measured before unloading The flowability index I is established by combining theoretical calculation and indoor test. fThe quantitative relationship between the liquid level of each channel and f() is as follows: Reverse deduction to get liquidity index I f :

[0022]

[0023] Assume that the apparent density of fresh concrete is ρ c0 , according to the mass m of fresh concrete in the container measured in the initial state before unloading c0 and the volume of fresh concrete V c0 Perform the calculation:

[0024]

[0025] Among them, V equ is the internal volume of the detection container, S k is the cross-sectional area of ​​the kth channel, is the upper edge height of the kth channel, It is the distance from the liquid surface of the freshly mixed concrete in each channel to the upper edge of each channel.

[0026] In some embodiments, the viscosity index of fresh concrete is 1 v , which is the average unloading rate during the uniform unloading period Based on theoretical calculations and indoor tests, the viscosity index I is established. v With average discharge rate The quantitative relationship between g(), then according to the average unloading rate Reverse the stickiness index I v :

[0027]

[0028] According to the fresh concrete unloading mass-time curve measured during the unloading process, the average unloading rate of fresh concrete is calculated using the following formula:

[0029]

[0030] Among them, t1 and m1 are the initial time of the uniform unloading period and the initial unloading mass, respectively. n and m n They are the final time of the uniform unloading period and the final unloading mass;

[0031] According to the fresh concrete discharge flow rate-time curve measured during the discharge process, the average discharge flow rate of fresh concrete is calculated using the following formula:

[0032]

[0033] in, For uniform unloading period The discharge flow rate of fresh concrete at the recorded value is is the total number of data points of the fresh concrete discharge flow rate during the uniform discharge period.

[0034] In some embodiments, let the uniformity index of fresh concrete be UI c , which is evaluated based on the fluctuation and uniformity of the discharge rate of fresh concrete;

[0035] According to the fresh concrete discharge mass-time curve measured during the discharge process, the uniformity index UI of the fresh concrete is calculated by any of the following methods: c :

[0036] Method 1: Calculate the uniformity index UI of fresh concrete according to the following formula: c :

[0037]

[0038] Among them, m i and m i+1 are the concrete discharge masses at the i-th and i+1-th record values ​​in the uniform discharge period, t i and t i+1 are the time of the i-th and i+1-th record values ​​in the uniform unloading period, respectively; t1 and m1 are the initial time and initial unloading mass of the uniform unloading period, respectively; t n and m n They are the final time of the uniform unloading period and the final unloading mass;

[0039] Method 2: Calculation method based on the root mean square of the residual

[0040] First, a linear fit is performed on the data of the uniform unloading period in the fresh concrete unloading mass-time curve to obtain the fitting formula:

[0041]

[0042] in, is the estimated value of the discharge mass of fresh concrete, t is any moment in the uniform discharge period, a and b are the coefficient and constant term of the linear fit respectively;

[0043] Then, the discharge uniformity UI of fresh concrete is calculated according to the following formula: c :

[0044]

[0045] in, is the estimated value of the fresh concrete discharge mass at the time corresponding to the i-th record value;

[0046] Method 3: Calculation method based on discriminant coefficient

[0047] According to the fitting formula and the following formula, the discharge uniformity UI of fresh concrete is calculated: c :

[0048]

[0049] in, It is the mean value of the discharge mass of fresh concrete during the uniform discharge period;

[0050] According to the fresh concrete flow rate-time curve measured during the unloading process, the uniformity index UI of the fresh concrete is calculated according to the following formula: c :

[0051]

[0052]

[0053] in, For uniform unloading period Fresh concrete discharge flow rate at 1 recorded value; is the average discharge rate of fresh concrete; is the total number of data points of the fresh concrete discharge flow rate during the uniform discharge period.

[0054] In some embodiments, an obstacle steel bar is provided in the detection container near the connecting part of each channel for checking the gap passability of fresh concrete. The diameter of the obstacle steel bar does not exceed 0.5 times the maximum aggregate particle size of the fresh concrete. The distance between two adjacent obstacle steel bars is set to 2 to 3 times the maximum aggregate particle size of the fresh concrete. The gap passability of the fresh concrete is detected by whether the fresh concrete is blocked at the obstacle steel bar:

[0055]

[0056] Among them, δ pass It is an index of the gap passability of fresh concrete.

[0057] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0058] (1) The present invention discloses a method for testing the comprehensive working performance of fresh concrete. In one feeding and unloading process, various working performance indicators such as fluidity (plasticity), viscosity, uniformity, anti-segregation, gap passability and apparent density of concrete can be measured. The method is applicable to different types of concrete, including normal concrete and self-compacting concrete.

[0059] (2) The present invention discloses a method for testing the comprehensive working performance of fresh concrete, which has a fast testing speed, a reliable testing principle, and a simple analysis method. A single test takes 2 to 3 minutes, saving manpower and material resources.

[0060] (3) The present invention discloses a method for testing the comprehensive working performance of fresh concrete, which can provide various working performance indicators of concrete, such as fluidity (plasticity), cohesion, anti-segregation, gap passability and uniformity, at one time. These indicators can complement each other and comprehensively evaluate the working performance of fresh concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is an overall flow chart of a method for detecting comprehensive working performance of fresh concrete provided by an embodiment of the present disclosure;

[0062] Figure 2 It is a schematic diagram of force analysis of fresh concrete filling and flowing in a channel of a detection container in a detection method provided by an embodiment of the present disclosure;

[0063] Figure 3 is a schematic diagram of the results of fluidity testing of fresh concrete using the detection method provided by an embodiment of the present disclosure;

[0064] Figure 4 is a quantitative relationship between the channel height difference and the slump spread as a fluidity indicator provided by the embodiments of the present disclosure;

[0065] Figure 5 The embodiment of the present disclosure provides a quantitative relationship between the hopper discharge time as a viscosity index and the average discharge rate;

[0066] Figure 6 (a) and (b) are respectively schematic diagrams of concrete discharge mass-time curves and uniformity calculation results measured for self-compacting concrete used in a dam construction according to an embodiment of the present disclosure, Figure 6 The uniformity of concrete corresponding to (a) is better than Figure 6 (b) corresponds to the uniformity of the concrete. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is 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 application and are not used to limit the present application.

[0068] On the contrary, the present application covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present application as defined by the claims. Further, in order to make the public have a better understanding of the present application, some specific details are described in detail in the detailed description of the present application below. Those skilled in the art can fully understand the present application without the description of these details.

[0069] See also Figure 1 The present disclosure provides a method for detecting the comprehensive performance of fresh concrete, comprising the following steps:

[0070] Step S1, pouring an appropriate amount of fresh concrete into a channel of a detection container having multiple channels and interconnected at the bottom, and allowing the fresh concrete to flow in the detection container by its own weight and gradually fill each channel; then standing for a period of time until the liquid level of the fresh concrete in each channel remains substantially unchanged, taking this as the initial state before unloading, and measuring the liquid level of the fresh concrete in each channel and the mass of the fresh concrete in the detection container;

[0071] Step S2, opening the discharge port at the bottom of the detection container, so that the fresh concrete in the detection container is discharged through the discharge port at the bottom by its own weight; during the discharge process, the mass of the fresh concrete discharged from the detection container or the discharge flow rate of the fresh concrete at the discharge port is measured at intervals, and after the discharge is completed, a fresh concrete discharge mass-time curve or a fresh concrete discharge flow rate-time curve is obtained;

[0072] Step S3, according to the measurement results of step S1 and step S2, a series of indicators of fresh concrete are sorted and converted as a comprehensive evaluation result of the working performance of fresh concrete, and the series of indicators include a combination of any multiple indicators of fluidity, viscosity, uniformity and apparent density of fresh concrete.

[0073] In some embodiments, the main body of the detection container is made of an alloy material that is rust-proof, strong, and easy to clean; or the main body of the detection container is made of a transparent material, such as a transparent acrylic plate, to facilitate visualization of the detection process. Stainless steel is preferably used for outdoor applications, and can be directly cleaned with a high-pressure water gun, which is strong and reliable; organic glass or high-strength glass is preferably used for indoor applications, which is convenient for observing and recording the flow state of concrete. The inner wall of the detection container needs to be moistened with clean water before the detection begins. The interior of the detection container is divided into a plurality of vertical channels whose bottoms are interconnected by a plurality of partitions. A plurality of slots that cooperate with the partitions are formed on the inner side wall of the detection container. By inserting the partitions into different slots, the channel width can be adjusted to adapt to different types of fresh concrete. The minimum side length of the cross section of any channel in the detection container shall not be less than 5 times the maximum aggregate particle size of the concrete, and the height shall not be less than 10 times the maximum aggregate particle size of the freshly mixed concrete; the channel for pouring freshly mixed concrete shall be used as the feeding channel, and the cross-sectional area of ​​the feeding channel shall not be less than 1.5 times the average cross-sectional area of ​​other channels; the discharge port at the bottom of the detection container shall consist of a gradually narrowing inclined section and a parallel extension section connected to its lower part, and the side length of the discharge port at the smallest diameter shall not be less than 5 times the maximum aggregate particle size of the freshly mixed concrete, and can be set to 5 to 8 times the maximum aggregate particle size of the freshly mixed concrete; the length of the parallel extension section shall not be less than 3 times the maximum aggregate particle size of the freshly mixed concrete, which plays a role in controlling the concrete discharge flow rate.

[0074] Furthermore, for self-compacting concrete with good fluidity, the partition arrangement can be adjusted to set the channel into a narrow and long form, the number of channels is 4 to 8, and the cross-sectional size of the channel is 5 to 8 times the maximum aggregate particle size of the concrete to be tested, generally 10 cm to 16 cm; for ordinary concrete with poor fluidity, the partition arrangement can be adjusted to set a wider channel, the number of channels is 3 to 5, and the cross-sectional size of the channel is 5 to 10 times the maximum aggregate particle size of the concrete to be tested, generally 10 cm to 20 cm. The discharge section of the detection container should be set in a gradually narrowing form, and its inclination angle α (i.e., the angle between the side wall of the discharge section and the horizontal plane) should be between 50° and 70°. If it is too small, it will easily cause concrete blockage, and if it is too large, the detection container will be too high, which is not conducive to on-site installation and implementation.

[0075] Furthermore, a number of obstacle steel bars can be set in the channel of the test container to check the gap passability of the concrete to be tested. Preferably, the obstacle steel bars are steel bars with a circular cross-section and are set near the bottom end of the feed channel. The spacing between two adjacent obstacle steel bars is generally set to 2 to 3 times the maximum aggregate particle size of the concrete to be tested, usually 4 cm to 6 cm, to simulate a narrow filling or flow channel. With the help of the obstacle steel bars, the intermittent passability of the fresh concrete is evaluated according to whether there is a blockage phenomenon during the loading and unloading process.

[0076] Furthermore, the selection of the feed channel in the detection container can be determined according to the type of concrete to be tested and the on-site deployment conditions. The length of the partition serving as the side wall of the feed channel is shorter than that of the partition of the detection channel to facilitate the placement of obstacle steel bars.

[0077] In some embodiments, the liquid level of fresh concrete in each channel is measured manually, by a sensor, or by image recognition; wherein:

[0078] Manual measurement is to manually measure the liquid level of fresh concrete in the channel using a ruler or scale lines;

[0079] The sensor measurement is to use a laser distance sensor, an ultrasonic distance sensor or an infrared distance sensor fixed just above the channel to measure the liquid level of the freshly mixed concrete in the channel;

[0080] Image recognition measurement is a method of measuring the liquid level of fresh concrete in a channel of a detection container made of transparent material using a camera and image recognition method. In addition, the image recognition measurement method can also record the liquid level of fresh concrete in the detection container at different times, that is, the filling process.

[0081] In some embodiments, the mass of freshly mixed concrete in the detection container is measured by manually recording the reading of an electronic scale placed at the bottom of the receiving container below the discharge port; or by measuring data of a weight sensor fixed at the bottom of the detection container.

[0082] Furthermore, during the unloading process, the quality of fresh concrete in the detection container or the unloading flow rate of fresh concrete is measured at intervals, and the measurement interval time does not exceed 1 / 10 of the total unloading time.

[0083] In some embodiments, when it is inconvenient to measure the discharge quality of fresh concrete during the discharge process, the discharge flow rate of fresh concrete at the discharge port measured by the concrete flow rate detection equipment can also be used to calculate the viscosity index and uniformity index of the fresh concrete.

[0084] Combination Figure 2 The detection principle of the detection method provided by the embodiment of the present disclosure is described as follows:

[0085] The fluidity (plasticity) of fresh concrete is directly related to its yield stress τ0. Under the action of gravity, friction of the side walls (including the side walls of the test container and the surface of the partition) and viscous resistance of motion, the filling height in different connecting channels is different. Specifically: when the pressure P on the concrete is equal to the gravity G and the shear yield resistance F τ0 When the sum of the concrete and the shear yield resistance F is equal, the concrete will stop rising in the channel. τ0It is positively correlated with the yield stress τ0 and the contact area between the concrete and the side wall. It can be seen that the better the concrete fluidity, the smaller the yield stress τ0, and the higher the filling height of the concrete in the channel. The worse the concrete fluidity, the greater the yield stress, and the lower the filling height of the concrete in the channel. Therefore, the filling height difference of concrete in different channels directly reflects the size of the yield stress τ0, that is, the size of the concrete fluidity (plasticity), see Figure 3 , the higher the fluidity of concrete, the smaller the yield stress τ0 that needs to be overcome by its own weight flow, and the smaller the filling height difference of each liquid surface. Conversely, the larger the filling height difference of each liquid surface. Considering the complex influence and randomness brought by the multiphase nature of concrete itself (aggregate, mortar, air), the quantitative relationship between the concrete fluidity index and the channel liquid level difference can be determined by combining theoretical calculation and indoor experiments; it should be pointed out that the purpose of setting up multiple connecting channels in the embodiment of the present disclosure is: 1) to make the difference of the test results more significant, that is, to increase the filling height difference; 2) to eliminate the influence of the speed or kinetic energy of the concrete itself on the results.

[0086] Furthermore, the volume of the fresh concrete can be calculated based on the height of the fresh concrete in the channel, and the apparent density of the fresh concrete can be deduced in combination with its mass.

[0087] Furthermore, the viscosity and segregation resistance of fresh concrete can be evaluated based on the discharge time or discharge rate of fresh concrete; the quantitative relationship between the discharge time of the concrete V-funnel and the discharge rate of the test container can be determined by indoor tests;

[0088] Furthermore, the uniformity of fresh concrete is evaluated according to the fluctuation and uniformity of the discharge rate of fresh concrete. The smaller the fluctuation of the discharge rate during the discharge process, the smoother the discharge mass-time curve or the discharge flow rate-time curve, indicating that the discharge process is more uniform, that is, it can be considered that the uniformity and workability of fresh concrete are better; conversely, the more complex and tortuous the discharge mass-time curve or the discharge flow rate-time curve is, the worse the uniformity of the fresh concrete mixture is;

[0089] Furthermore, the gap passability is determined based on whether the fresh concrete can pass through the detection container and its built-in obstacle steel bars smoothly.

[0090] Based on the above detection principle, the embodiment of the present disclosure uses the liquid level in each channel after stabilization before unloading, that is, the liquid level of fresh concrete in each channel in the initial state before unloading, to detect the fluidity and apparent density of fresh concrete. The process is as follows:

[0091] First, based on theoretical calculations and indoor tests, the fluidity index I was established. f The quantitative relationship between the liquid level of each channel is f(), and the measured fluidity index I is obtained by inferring the liquid level of each channel.f :

[0092]

[0093] in, is the liquid level of fresh concrete in each channel in the initial state measured before unloading, k is the channel number, k=1~K, K is the number of channels in the detection container.

[0094] Assume that the apparent density of fresh concrete is ρ c0 , according to the initial state measured before unloading, the mass m of fresh concrete in the container is detected c0 And the volume of fresh concrete Vc0 is calculated:

[0095]

[0096] Among them, V equ To detect the internal volume of the container, S k is the cross-sectional area of ​​the kth channel, is the upper edge height of the kth channel, It is the distance from the liquid surface of the freshly mixed concrete in each channel to the upper edge of each channel.

[0097] In a specific embodiment of the present application, see Figure 4 The fluidity index of fresh concrete is specifically the slump expansion I slumpflow , the slump expansion I established based on theoretical calculations and indoor tests slumpflow and the apparent density ρ c0 The height of the liquid level in each channel of fresh concrete The quantitative relationship between them is:

[0098]

[0099] in, and are the maximum and minimum values ​​of the fresh concrete liquid level in each channel of the detection container under the initial state, The maximum liquid level difference of fresh concrete in the detection container under the initial state; m c0 The unit is g, The unit is cm, ρ c0 The unit is kg / m 3 .

[0100] In some embodiments, the viscosity index of fresh concrete is 1 v , which is the average unloading rate during the uniform unloading period Based on theoretical calculations and indoor tests, the viscosity index I is established. v With average discharge rate The quantitative relationship between g() is as follows: Inversely calculate the viscosity index I of fresh concrete v :

[0101]

[0102] It should be noted that when calculating the average unloading rate The unloading start section and unloading end section should be removed to eliminate the influence of the accelerated flow of fresh concrete in the unloading port opening section and the adhesion of the side wall in the unloading end section on the unloading process. The middle section of the unloading process is preferably used as the uniform unloading period, and the average unloading rate is calculated using the data of the uniform unloading period. The average unloading rate is calculated by using the fresh concrete unloading flow rate-time curve. In addition, the uniformity indicator UI c Poor data points are selected to eliminate the interference and influence of concrete segregation, blocking and other phenomena on the quantitative relationship g().

[0103] Furthermore, when the measured data is the discharge mass of fresh concrete, the average discharge rate of fresh concrete is calculated according to the following formula:

[0104]

[0105] Among them, t1 and m1 are the initial time of the uniform unloading period and the initial unloading mass, respectively. n and m n They are the final time of the uniform unloading period and the final unloading mass;

[0106] When the measured data is the discharge flow rate of fresh concrete, the average discharge rate of fresh concrete is calculated according to the following formula:

[0107]

[0108] in, For uniform unloading period The discharge flow rate of fresh concrete at the recorded value is is the total number of data points of the fresh concrete discharge flow rate during the uniform discharge period.

[0109] In a specific embodiment of the present application, see Figure 5 , viscosity index of fresh concrete I v Specific use of V hopper unloading time I vfunnel Characterization, which is related to the average discharge rate The quantitative relationship between them is:

[0110]

[0111] Among them, m 95 and m5 are the initial mass m of fresh concrete in the test container. c0 95% and 5%; t m95 and t m5 They are the moments when the concrete in the detection container is unloaded to 95% and 5% of its mass respectively.

[0112] In some embodiments, when calculating the fresh concrete uniformity index UI c The uniform unloading period data is also used. For the measured unloading quality and unloading flow rate, the present disclosure provides the uniformity index UI c The calculation methods are described as follows.

[0113] When the measured data is the discharge mass of fresh concrete, the uniformity index UI of fresh concrete is calculated by any of the following three methods: c :

[0114] Method 1: Calculate the uniformity index UI of fresh concrete according to the following formula: c :

[0115]

[0116] Among them, m i and m i+1 are the discharge masses of fresh concrete at the i-th and i+1-th record values ​​in the uniform discharge period, t i and t i+1 are the time of the i-th and i+1-th record values ​​in the uniform unloading period, respectively; t1 and m1 are the initial time and initial unloading mass of the uniform unloading period, respectively; t n and m n They are the final time of the uniform unloading period and the final unloading mass;

[0117] It should be noted that the advantage of method 1 is that it does not require fitting calculations, and the uniformity index UI can be obtained based on simple calculations. c When the fitting calculation capability is available, method 2 or method 3 can also be used for calculation.

[0118] Method 2: Calculation method based on the root mean square (RMS) of the residual

[0119] First, a linear fit is performed on the data of the uniform unloading period in the unloading mass-time curve of fresh concrete to obtain the fitting formula:

[0120]

[0121] in, is the estimated value of the discharge mass of fresh concrete, t is any moment in the uniform discharge period, a and b are the coefficient and constant term of the linear fit respectively;

[0122] Then, the uniformity index UI of fresh concrete is calculated according to the following formula: c :

[0123]

[0124] in, is the estimated value of the fresh concrete discharge mass at the time corresponding to the i-th record value;

[0125] Method 3: Calculation method based on the discriminant coefficient (R square)

[0126] According to the above fitting formula and the following formula, the uniformity index UI of fresh concrete is calculated: c :

[0127]

[0128] in, It is the average value of the discharge mass of fresh concrete during the uniform unloading period.

[0129] When the measured data is the discharge flow rate of fresh concrete, the uniformity index UI of fresh concrete is calculated according to the following formula: c :

[0130]

[0131] in, For uniform unloading period Fresh concrete discharge flow rate at 1 recorded value; is the average discharge rate of fresh concrete; is the total number of data points of the fresh concrete discharge flow rate during the uniform discharge period.

[0132] In a specific embodiment of the present application, the measured data is the discharge mass of fresh concrete, and the uniformity index UI of fresh concrete is calculated by method 1. c :

[0133]

[0134] The physical meanings of the parameters in the above formula are as mentioned above and will not be repeated here.

[0135] Furthermore, according to the batch test results of different types of concrete, this embodiment sets: c>0.85, the concrete uniformity is considered good; when 0.75 <UI c When ≤0.85, the concrete is considered slightly uneven; when 0.60 <UI c When UI is ≤0.75, the concrete uniformity is considered poor; c When ≤0.60, the concrete is considered to be seriously non-uniform. Figure 6 In (a) and (b), the UI of the self-compacting concrete used in the construction of a dam is measured for the concrete with good uniformity. c =0.96, UI measured for concrete with poor uniformity c =0.67. It should be noted that when establishing When the uniformity index UI is removed c <0.85 to eliminate the interference and influence of concrete segregation, blocking and other phenomena on the above relationship.

[0136] In some embodiments, the gap passability of fresh concrete can be determined by whether there is blockage at the obstacle reinforcement:

[0137]

[0138] Among them, δ pass It is the gap passability index of fresh concrete. When the liquid level of fresh concrete in the feed channel is The liquid level threshold is not exceeded When pass =1, indicating that the gap passability of fresh concrete is better; when the liquid level of fresh concrete in the feed channel is Exceeding the liquid level threshold When pass =0, indicating that the gap permeability of fresh concrete is poor; the liquid level height threshold It needs to be calculated based on the geometric dimensions of the test container.

[0139] It can be understood that the method for detecting the comprehensive working performance of fresh concrete provided in the embodiment of the present disclosure has the following advantages:

[0140] (1) The present invention discloses a method for testing the comprehensive working performance of fresh concrete. In a single feeding and unloading process, various working performance indicators such as fluidity (plasticity), viscosity, uniformity, anti-segregation, gap passability and density of concrete can be measured. The method is applicable to different types of concrete, including normal concrete and self-compacting concrete.

[0141] (2) The present invention discloses a method for testing the comprehensive working performance of freshly mixed concrete, which has a fast testing speed, a reliable testing principle, a simple analysis method, and a testing container with a simple and easy-to-process structure. A single test takes 2 to 3 minutes, saving manpower and material resources.

[0142] (3) The present invention discloses a method for testing the comprehensive working performance of fresh concrete, which can provide various working performance indicators of concrete, such as fluidity (plasticity), cohesion, anti-segregation, gap passability and uniformity, at one time. These indicators can be supplemented with each other to comprehensively evaluate the working performance of concrete.

[0143] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0144] Although embodiments of the present disclosure have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for detecting the comprehensive working performance of fresh concrete, characterized in that: The following steps are involved: Step S1, pouring fresh concrete into a channel of a detection container having multiple channels and interconnected at the bottom, wherein the fresh concrete flows in the detection container by its own weight and gradually fills each channel; standing for a period of time until the liquid level of the fresh concrete in each channel remains unchanged, taking this as the initial state before unloading, and measuring the liquid level of the fresh concrete in each channel and the mass of the fresh concrete in the detection container; Step S2, opening the discharge port at the bottom of the detection container, so that the fresh concrete in the detection container is discharged through the discharge port by its own weight; during the discharge process, measuring the mass of the fresh concrete discharged from the detection container or measuring the discharge flow rate of the fresh concrete, and after the discharge is completed, obtaining a fresh concrete discharge mass-time curve or a fresh concrete discharge flow rate-time curve; Step S3, according to the measurement results of step S1 and step S2, a series of indicators of fresh concrete are sorted and converted as a comprehensive evaluation result of the working performance of fresh concrete, wherein the series of indicators include a combination of any multiple indicators of fluidity, viscosity, uniformity and apparent density of fresh concrete.

2. The detection method according to claim 1, characterized in that: The channel in the detection container is a vertical channel, the minimum side length of the cross section of any channel is not less than 5 times the maximum aggregate particle size of the concrete, and the height is not less than 10 times the maximum aggregate particle size of the fresh concrete; the channel into which the fresh concrete is poured is used as a feed channel, and the cross-sectional area of ​​the feed channel is not less than 1.5 times the average cross-sectional area of ​​other connected channels; The discharge port consists of a gradually narrowing inclined section and a parallel extension section connected to its lower part. The side length of the discharge port at the smallest diameter is not less than 5 times the maximum aggregate particle size of the fresh concrete, and the length of the parallel extension section is not less than 3 times the maximum aggregate particle size of the fresh concrete.

3. The detection method according to claim 1, characterized in that: The liquid level of the fresh concrete in each channel is measured manually, by a sensor or by image recognition; The manual measurement is to manually measure the liquid level of the fresh concrete in the channel using a ruler or scale lines; the sensor measurement is to measure the liquid level of the fresh concrete in the channel using a laser ranging sensor, an ultrasonic ranging sensor or an infrared ranging sensor fixed directly above the channel; the image recognition measurement is to measure the liquid level of the fresh concrete in the channel using a camera and an image recognition method for the detection container made of a transparent material.

4. The detection method according to claim 1, characterized in that: The mass of the freshly mixed concrete in the detection container is measured by manually recording the reading of an electronic scale placed at the bottom of the receiving container below the discharge port; or by measuring data of a weight sensor fixed at the bottom of the detection container.

5. The detection method according to claim 1, characterized in that: During the unloading process, the mass of fresh concrete in the detection container or the unloading flow rate of fresh concrete is measured at intervals, and the measurement interval time does not exceed 1 / 10 of the total unloading time.

6. The detection method according to claim 1, characterized in that: The fluidity index and apparent density of the fresh concrete are calculated according to the liquid level height of the fresh concrete in each channel under the initial state before unloading; the viscosity index and uniformity index of the fresh concrete are calculated according to the fresh concrete unloading mass-time curve or the fresh concrete unloading flow rate-time curve during the unloading process.

7. The detection method according to claim 1, characterized in that: Assume that the fluidity index of fresh concrete is I f , which is the height of the liquid level of fresh concrete in each channel at the initial state measured before unloading The flowability index I is established by combining theoretical calculation and indoor test. f The quantitative relationship between the liquid level of each channel and f() is as follows: Reverse deduction to get liquidity index I f : Assume that the apparent density of fresh concrete is ρ c0 , according to the mass m of fresh concrete in the container measured in the initial state before unloading c0 and the volume of fresh concrete V c0 Perform the calculation: Among them, V equ is the inner volume of the detection container, S k is the cross-sectional area of ​​the kth channel, is the upper edge height of the kth channel, It is the distance from the liquid surface of the freshly mixed concrete in each channel to the upper edge of each channel.

8. The detection method according to claim 1, characterized in that The viscosity index of fresh concrete is I v , which is the average unloading rate during the uniform unloading period Based on theoretical calculations and indoor tests, the viscosity index I is established. v With average discharge rate The quantitative relationship between g(), then according to the average unloading rate Reverse the stickiness index I v : According to the fresh concrete unloading mass-time curve measured during the unloading process, the average unloading rate of fresh concrete is calculated using the following formula: Among them, t1 and m1 are the initial time of the uniform unloading period and the initial unloading mass, respectively. n and m n They are the final time of the uniform unloading period and the final unloading mass; According to the fresh concrete discharge flow rate-time curve measured during the discharge process, the average discharge flow rate of fresh concrete is calculated using the following formula: in, For uniform unloading period The discharge flow rate of fresh concrete at the recorded value is is the total number of data points of fresh concrete discharge flow rate during the uniform discharge period.

9. The detection method according to claim 1, characterized in that: Assume that the uniformity index of fresh concrete is UI c , which is evaluated based on the fluctuation and uniformity of the discharge rate of fresh concrete; According to the fresh concrete discharge mass-time curve measured during the discharge process, the uniformity index UI of the fresh concrete is calculated by any of the following methods: c : Method 1: Calculate the uniformity index UI of fresh concrete according to the following formula: c : Among them, m i and m i+1 are the concrete discharge masses at the i-th and i+1-th record values ​​in the uniform discharge period, t i and t i+1 are the time of the i-th and i+1-th record values ​​in the uniform unloading period, respectively; t1 and m1 are the initial time and initial unloading mass of the uniform unloading period, respectively; t n and m n They are the final time of the uniform unloading period and the final unloading mass; Method 2: Calculation method based on the root mean square of the residual First, a linear fit is performed on the data of the uniform unloading period in the fresh concrete unloading mass-time curve to obtain the fitting formula: in, is the estimated value of the discharge mass of fresh concrete, t is any time in the uniform discharge period, a and b are the coefficient and constant term of the linear fit respectively; Then, the discharge uniformity UI of fresh concrete is calculated according to the following formula: c : in, is the estimated value of the fresh concrete discharge mass at the time corresponding to the i-th record value; Method 3: Calculation method based on discriminant coefficient According to the fitting formula and the following formula, the discharge uniformity UI of fresh concrete is calculated: c : in, It is the mean value of the discharge mass of fresh concrete during the uniform discharge period; According to the fresh concrete flow rate-time curve measured during the unloading process, the uniformity index UI of the fresh concrete is calculated according to the following formula: c : in, For uniform unloading period Fresh concrete discharge flow rate at 1 recorded value; is the average discharge rate of fresh concrete; is the total number of data points of fresh concrete discharge flow rate during the uniform discharge period.

10. The detection method according to any one of claims 1 to 9, characterized in that: In the detection container, an obstacle steel bar is provided near the connecting part of each channel for checking the gap passability of fresh concrete. The diameter of the obstacle steel bar does not exceed 0.5 times the maximum aggregate particle size of the fresh concrete. The distance between two adjacent obstacle steel bars is set to 2 to 3 times the maximum aggregate particle size of the fresh concrete. The gap passability of the fresh concrete is detected by whether the fresh concrete is blocked at the obstacle steel bar: Among them, δ pass It is an index of the gap passability of fresh concrete.

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