Method for detecting working performance of concrete in mixer truck tank in real time

Abstract

The invention discloses a method for detecting the working performance of concrete in a mixer truck tank in real time, and the method is used for monitoring the flowability of the concrete in real time. The dynamic yield stress of concrete is calculated by measuring data such as the inclination angle between the concrete liquid level in the concrete tank car and the horizontal plane, the contact area of the concrete in contact with the tank body and the cross section area of the tank body in the transportation process, and the roughness of the concrete surface is measured through a laser scanner. And judging whether the concrete is in a qualified or segregated or dry and thick state by comparing the dynamic yield stress with the corresponding threshold value or comparing the roughness with the corresponding threshold value. The monitoring method provided by the invention has the following advantages: after qualified concrete is discharged, the performance change condition of the concrete in the tank of the concrete tank truck can be detected in real time in the transportation process; when the concrete performance is not good, early warning can be sent to quality control personnel, and guarantee is provided for efficient construction.

Description

Technical Field

[0001] The invention relates to a fresh concrete performance detection technology, in particular to a method for real-time detection of the working performance of concrete in a mixer tank. Background Art

[0002] Concrete is one of the materials widely used in the construction industry. The development of modern construction technology has placed higher and higher requirements on the stability of concrete's working performance in the flow plastic state. The fluidity of concrete directly affects its operability during the construction process and the final project quality. Traditional concrete fluidity detection methods usually rely on laboratory tests and are limited to the concrete before it leaves the factory. The concrete performance changes over time during transportation after leaving the factory, but there is no effective means to detect the changes in the concrete performance in the tank during transportation. Therefore, it is of great practical significance to develop a method that can monitor the fluidity of concrete in a concrete tank truck in real time. Summary of the invention

[0003] The purpose of the present invention is to provide a method for detecting the working performance of concrete in a mixing tank, which can monitor the fluidity of concrete in real time and provide data through a wireless transmission system so as to issue an early warning to quality control personnel or institutions when the concrete performance is poor.

[0004] The technical solution of the present invention is as follows: a laser scanner group is arranged in a feed hopper device of a concrete tank truck, the feed hopper device comprises a perfectly circular guide barrel 1 and a feed hopper 2, a lower rib 1-1 is arranged on the upper edge of the guide barrel 1, a feed hopper back plate 2-1 is arranged between the upper edge of the guide barrel 1 and the lower rib 1-1 on the side close to the feed hopper 2, the feed hopper back plate 2-1 is integrated with the feed hopper 2, the laser scanner is a laser scanner group 1-2, and the laser scanner group 1-2 is fixedly connected in a semi-enclosed space formed by the lower rib 1-1, the feed hopper back plate 2-1 and the guide barrel 1. Concrete is added into the tank truck through this feed hopper, and the tank body of the concrete tank truck rotates clockwise at a low and uniform speed (the speed is within the range of 2-4rad / min) during the driving process. At this time, the barrel wall in contact with the concrete generates a certain adhesion force on the concrete, and the adhesion force is the dynamic yield stress of the concrete. τ (N / m 2 ), so the concrete liquid surface tilts steadily under the rotation, causing the concrete center of mass to shift, such as Figure 3 , the torque generated by the mass center offset and the torque generated by the adhesion force form a dynamic equilibrium state. The equilibrium formula is: g Formula (2); like Figure 5 , take a cross section perpendicular to the tank's rotation centerline (see Figure 5 The blue part), the part of the cross section occupied by the concrete inside the tank is recorded as C (see Figure 5 (red part).

[0005] like Figure 2 When the tank is stationary, the concrete mass center is at point A. When the tank rotates at a constant speed, the concrete mass center shifts to point B. Figure 3 , the horizontal displacement of the two points is recorded as 。 Horizontal displacement of center of mass change The inclination angle θ of the concrete liquid surface has the following relationship: Formula (1); Laser scanner is a device that uses laser technology to scan and image, which can quickly build a three-dimensional image model of an object. Figure 3 After combining the concrete surface shown in the figure with the cross-sectional view of the tank body, the perfect circular cross-section of the cylindrical tank body rotating along the axis, the radius R of the tank body cross-section, the contact area S of the concrete contacting the tank body, etc. can be obtained. The position of the concrete mass center B can be calculated by computer, thereby obtaining the inclination angle θ. Substituting the above data into the following formula, the dynamic yield stress can be obtained τ value: Formula (3); in, τ is the dynamic yield stress of concrete, in N / m 2 ; y c It is the distance between the center point of the concrete liquid surface and the centroid of the geometric area occupied by the concrete in the cross section, in meters; θ is the inclination angle between the concrete liquid surface and the horizontal plane, in degrees; S is the contact area of ​​the concrete contacting the tank, in m 2 ; is the radius of the tank cross section, in m; is the horizontal displacement of the concrete center of mass when the tank is static and when it rotates at a uniform speed, in m; m is the mass of concrete, in kg; g is the acceleration due to gravity, which is a known constant with the unit of N / kg.

[0006] When θ≠0, it means that the dynamic yield stress of concrete is not equal to 0. At this time, the dynamic yield stress can be calculated by the above formula. The larger the dynamic yield stress, the worse the fluidity of the concrete, and the smaller the dynamic yield stress, the better the fluidity of the concrete. Because the segregation state indicates that the concrete is too thin, the slurry and aggregate are separated, and the surface is slurry water, and the slurry water yield stress is very small, almost horizontal, so the situation of concrete segregation can be ruled out at this time. Therefore, a dynamic yield stress threshold Z can be set according to the technical needs of the project site.

[0007] When τ≤Z, it means the concrete is qualified; when τ>Z, it means the concrete is dry and thick.

[0008] When θ=0, it is impossible to directly judge whether the concrete is in a qualified fluidity or segregated state, so it is necessary to judge from the appearance of the concrete liquid surface: for segregated concrete, the aggregate sinks, the surface is a slurry layer, the roughness is small, and the dynamic yield stress is 0, but for concrete with qualified cohesion, the aggregate is evenly distributed on the surface and the roughness is large. Therefore, when θ=0, the roughness Ra can be used to distinguish whether the concrete is in a qualified or segregated state (the roughness Ra can be measured by a laser scanner). A roughness threshold T is set according to the technical needs of the project site.

[0009] When Ra>T, it means the concrete is qualified; when Ra≤T, it indicates that the concrete is segregated.

[0010] The precision of θ is ≤0.5 degrees, and when it is less than 0.1 degrees, θ is recorded as 0 degrees.

[0011] The beneficial effects of the present invention are as follows: after qualified concrete is delivered, during transportation, the performance changes of the concrete in the tank of the concrete tank truck can be detected in real time, and real-time data can be provided to quality control personnel or institutions. When the concrete performance is poor, an early warning can be issued to ensure the stability of the concrete quality in the construction project, guarantee construction, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart of a method for real-time detection of the working performance of concrete in a mixer tank; Figure 2 It is a schematic diagram of the force balance of concrete in the tank body when it is stationary; Figure 3 It is a schematic diagram of the force balance of concrete in a tank body rotating at a low and uniform speed; Figure 4 It is a schematic diagram of the contact area of ​​the concrete contacting the tank body; Figure 5 It is a schematic diagram of a cross section perpendicular to the rotation centerline of the tank; Figure 6 It is a structural schematic diagram of a concrete tank truck feed hopper device; Figure 7It is a front view of a feed hopper device of a concrete tank truck; Figure 8 This is a physical picture of the dry-consistent concrete of Example 1 of the present invention; Fig. 9 This is a physical picture of qualified concrete according to Example 2 of the present invention; Fig.10 This is a physical picture of the segregated concrete of Example 3 of the present invention.

[0013] In the figure: 1, material guide cylinder, 1-1, lower rib plate, 1-2, laser scanner group, 2-feed hopper, 2-1, feed hopper back plate. DETAILED DESCRIPTION

[0014] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0015] The present invention provides a concrete tanker feed hopper device, comprising a guide barrel and a feed hopper. A lower rib plate 1-1 is installed at the upper edge of the circular guide barrel to form a semi-enclosed cabin with the upper edge of the guide barrel and the back plate of the feed hopper 2-1. A laser scanner group is arranged inside the cabin to scan the surface of concrete in the mixing tank. The structural diagram is shown in FIG. Figure 4-Figure 7 .

[0016] If the quality inspector sets the roughness threshold T=2.5mm and the yield stress threshold Z=80N / m 2 .

[0017] Embodiment 1: Step 1: Use a concrete tank with a length of 5.27m and a cross-sectional radius of 2.2m, add 23,600kg of concrete, and make the concrete tank rotate at a constant speed of 2-4rad / min. The laser scanner scans the concrete surface and measures the inclination angle θ=5.5° between the concrete liquid surface and the horizontal plane under the rotating condition of the tank. At the same time, the laser scanner scans the contact point between the concrete surface and the cylinder wall and measures the contact area S=18.2m between the concrete and the tank. 2 , the centroid of the geometric area occupied by the concrete is calculated by computer. At this time, the distance y between the center point of the concrete liquid surface and the centroid of the concrete of the cross section C is obtained by the computer. c =0.47m.

[0018] Step 2: The laser scanner scans the liquid surface of the concrete and obtains the roughness Ra=15.8mm.

[0019] Step 3: Substitute the above data into formula (3) to calculate the dynamic yield stress of concrete =258.6N / m 2 .

[0020] at this time, >Z, indicating that the concrete is dry and thick, see Figure 8 .

[0021] Embodiment 2: Step 1: Use a concrete tank with a length of 5.27m and a cross-sectional radius of 2.2m, add 23,600kg of concrete, and make the concrete tank rotate at a constant speed of 2-4rad / min. The laser scanner scans the concrete surface and measures the inclination angle θ=1.0° between the concrete liquid surface and the horizontal plane under the rotating condition of the tank. At the same time, the laser scanner scans the contact point between the concrete surface and the cylinder wall and measures the contact area S=18.2m between the concrete and the tank. 2 , the centroid of the geometric area occupied by the concrete is calculated by computer. At this time, the distance y between the center point of the concrete liquid surface and the centroid of the concrete in the cross section is obtained by computer. c =0.47m.

[0022] Step 2: The laser scanner scans the liquid surface of the concrete and obtains the roughness Ra=5.8mm.

[0023] Step 3: Substitute the above data into formula 3 to calculate the dynamic yield stress of concrete =47.1N / m 2 .

[0024] At this time, τ≤Z, indicating that the concrete is qualified. Fig. 9 .

[0025] Embodiment 3: Step 1: Use a concrete tank with a length of 5.1m and a cross-sectional radius of 2m, add 18,880kg of concrete, and rotate the concrete tank at a constant speed of 2-4rad / min. The laser scanner scans the concrete surface and measures the inclination angle θ=0° between the concrete liquid surface and the horizontal plane under the rotating condition of the tank. At the same time, the laser scanner scans the contact point between the concrete surface and the cylinder wall and measures the contact area S=16.0m 2 , the centroid of the geometric area occupied by the concrete is calculated by computer. At this time, the distance y between the center point of the concrete liquid surface and the centroid of the concrete in the cross section is obtained by computer. c =0.42m.

[0026] Step 2: The laser scanner scans the liquid surface of the concrete and obtains the roughness Ra=0.5mm.

[0027] Step 3: When θ=0, it indicates that the dynamic yield stress is 0. There are two situations at this time. One is that the concrete is normal and has very high fluidity; the other is that the concrete is in a segregated state, and the liquid surface is close to the state of water. When Ra≤T, it can be determined that the concrete is segregated, see Fig.10 .

[0028] Embodiment 4: Step 1: Use a concrete tank with a length of 5.1m and a cross-sectional radius of 2m, add 18,880kg of concrete, and rotate the concrete tank at a constant speed of 2-4rad / min. The laser scanner scans the concrete surface and measures the inclination angle θ=0° between the concrete liquid surface and the horizontal plane under the rotating condition of the tank. At the same time, the laser scanner scans the contact point between the concrete surface and the cylinder wall and measures the contact area S=16.0m 2 , the centroid of the geometric area occupied by the concrete is calculated by computer. At this time, the distance y between the center point of the concrete liquid surface and the centroid of the concrete in the cross section is obtained by computer. c =0.42m.

[0029] Step 2: The laser scanner scans the liquid surface of the concrete and obtains the roughness Ra=4.2mm.

[0030] Step 3: When θ=0, it indicates that the dynamic yield stress is 0. There are two situations at this time. One is that the concrete is normal and has very high fluidity; the other is that the concrete is in a segregated state and the liquid surface is close to that of water. When Ra>T, the concrete can be judged to be qualified.

[0031] The data of the above four embodiments are as follows:

[0032] It should be noted that although embodiments of the present invention have been shown and described herein, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for real-time detection of the working performance of concrete in a mixer tank, characterized in that: The following steps are involved: S01, the concrete tank body is rotated at a constant speed at any speed limited to 2-4rad / min. The laser scanner scans the concrete surface and measures the inclination angle between the concrete liquid surface and the horizontal plane under the condition of tank body rotation, which is recorded as θ. At the same time, the contact point between the concrete surface and the cylinder wall is scanned to measure the contact area between the concrete and the tank body, which is recorded as S, unit: m 2 , take a cross section perpendicular to the centerline of rotation of the tank, the portion of the cross section occupied by the concrete in the tank is recorded as C, determine the distance from the center point O of the concrete liquid surface to the centroid of the geometric area occupied by the concrete in the cross section C, recorded as y c ; S02, horizontal displacement of center of mass change The inclination angle θ of the concrete liquid surface has the following relationship: Formula (1); When the tank rotates at a low and uniform speed, the cylinder wall of the tank in contact with the concrete produces an adhesive force on the concrete. This adhesive force is the dynamic yield stress of the concrete. τ A collection of τ The unit is N / m 2 Under the action of rotation, the concrete liquid surface tilts steadily, causing the concrete center of mass to shift. The torque generated by the center of mass shift and the torque generated by the adhesion force form a dynamic equilibrium state. The equilibrium formula is: g Formula (2); in, is the radius of the tank cross section, in m; is the horizontal displacement of the concrete center of mass when the tank is static and when it rotates at a uniform speed, in m; m is the mass of concrete, in kg; g is the acceleration due to gravity, in N / kg; Substituting formula (1) into formula (2), we get: Formula (3); S03, when θ≠0, a threshold value Z of dynamic yield stress is set according to the technical requirements of the site. When τ≤Z, it indicates that the concrete is qualified, and when τ>Z, it indicates that the concrete is dry and thick; When θ=0, the roughness Ra is used to distinguish whether the concrete is qualified or segregated; a roughness threshold T is set according to the technical needs of the site. When Ra>T, it means that the concrete is qualified, and when Ra≤T, it indicates that the concrete is segregated.

2. The method according to claim 1, characterized in that The precision of θ is ≤0.5 degrees, and when it is less than 0.1 degrees, θ is recorded as 0 degrees.

3. The method according to claim 1 or 2, characterized in that: The laser scanner is arranged on a feed hopper device of a concrete tank truck, the feed hopper device comprising a circular guide barrel (1) and a feed hopper (2), a lower rib plate (1-1) being arranged on the upper edge of the guide barrel (1), a feed hopper back plate (2-1) being provided between the upper edge of the guide barrel (1) and the lower rib plate (1-1) on the side close to the feed hopper (2), the feed hopper back plate (2-1) being integrated with the feed hopper (2), the laser scanner being a laser scanner group (1-2), the laser scanner group (1-2) being fixedly connected in a semi-enclosed space formed by the lower rib plate (1-1), the feed hopper back plate (2-1) and the guide barrel (1).

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