Device and method for testing water absorption and release performance of recycled aggregate

Abstract

The invention provides a testing device and a testing method for water absorption and release performance of recycled aggregate. The testing device comprises a detection head, a chuck, a plastic pipe, a U-shaped pressure pipe, a pressure sensor and a data collector; wherein one end of the plastic pipe is connected with the U-shaped pressure pipe, and the other end of the plastic pipe is connected with the detection head through the chuck; the pressure sensor is located on the pipe wall of the U-shaped pressure pipe and connected with the data collector through a conversion line. By adopting the testing device, the microscopic pressure intensity measured by the U-shaped pipe is visually represented as the macroscopic water-containing state of the recycled aggregate through the function relationship between the internal pore pressure and the water-containing state of the recycled aggregate, and a data basis is provided for the practical application of the recycled aggregate.

Description

Technical Field

[0001] The present invention relates to the technical field of building material research, and particularly to a test device and a test method for the water absorption and desorption performance of recycled aggregates. Background Art

[0003] As is well known, waste concrete blocks are usually the largest component of construction waste, 80% of which are aggregate components. The waste concrete blocks after crushing and screening can be used to replace natural aggregates in concrete. This type of recycled material is called recycled aggregate, which can better solve the problem of shortage of natural aggregates, reduce the trouble caused by the stacking of construction waste, and is of great significance for realizing the sustainable development of the construction industry. Compared with natural aggregates, recycled aggregates are wrapped with hardened cement mortar on the outside, with rough surfaces and many corners, and a large number of microcracks will be generated, resulting in significant differences in their performance from natural aggregates. Compared with natural aggregates, recycled aggregates have a large water absorption and desorption rate and a fast water absorption rate, which affect the workability, mechanical properties and durability of the concrete prepared from them. By testing the water absorption and desorption performance of recycled aggregates, the moisture distribution of aggregates in different media can be accurately grasped, and the performance of recycled concrete can be better controlled.

[0004] The traditional method for testing the water absorption performance of recycled aggregates is mainly the hydrostatic balance. By monitoring the mass change of recycled aggregates immersed in water at each time point, its water content state is calculated to obtain the time-varying water absorption. This method can only test the water absorption performance of recycled aggregates in water, and cannot test their water absorption performance in cement paste. Moreover, this method requires manual real-time monitoring, which is time-consuming and laborious. The principle of the water absorption and desorption performance of recycled aggregates is mainly the change of capillary tension on the surface and inside the aggregates. Many scholars have proposed using a U-shaped tube to test the water absorption and desorption performance of recycled aggregates. The change between the internal capillary pressure and the external atmospheric pressure during the water absorption and desorption process of aggregates is characterized by the liquid level difference of the U-shaped tube. This method is greatly affected by the environment. Changes in the external atmospheric pressure, wind force, etc. will all affect the liquid level change of the U-shaped tube. At the same time, real-time monitoring is required, which takes a long time, and the data obtained is the microscopic pressure of the aggregates, which is difficult to intuitively represent the water content state of the recycled aggregates and is difficult to provide a reference basis for the performance research of the recycled concrete prepared later. Therefore, it is of great significance to adopt an optimized method that can effectively solve the above problems. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a test device and a test method for the water absorption and desorption performance of recycled aggregates. By using a high-precision test device, a functional relationship between the microscopic pressure of the aggregates and the macroscopic water content state is established, and digital real-time monitoring can be realized, solving the problems raised in the above background art.

[0007] (2) Technical Solution

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] According to the first aspect of the present invention, a test device for the water absorption and release performance of recycled aggregates is provided, including a probe head, a chuck, a plastic pipe, a U-shaped pressure pipe, a pressure sensor and a data collector;

[0010] Wherein, one end of the plastic pipe is connected to the U-shaped pressure pipe, and the other end is connected to the probe head through the chuck; the pressure sensor is located on the pipe wall of the U-shaped pressure pipe, and the pressure sensor is connected to the data collector through a conversion line.

[0011] Preferably, the aperture of the probe head is selected from any one of 1mm, 3mm, 6mm, and 8mm.

[0012] Preferably, the liquid in the U-shaped pressure pipe is water, and liquid paraffin with a height of 5mm is injected on both sides of the water.

[0013] According to the second aspect of the present invention, a test method for the water absorption and release performance of recycled aggregates based on the above test device is provided, including the following steps:

[0014] S1. Calculate the water absorption rate and initial moisture content of the recycled aggregates;

[0015] S2. Drill a hole in the recycled aggregates to the center, insert the probe head into the hole and hold it, keep the liquid in the U-shaped pressure pipe balanced, and seal it;

[0016] S3. Place the recycled aggregates in air, water or slurry, measure the real-time change of the pore pressure inside the recycled aggregates through the pressure sensor, and read it through the data collector;

[0017] S4. Utilize the fitting relationship between the pore pressure inside the recycled aggregates and water absorption and release, and obtain the water-containing state corresponding to different pore pressures inside the recycled aggregates through Equation I. Equation I is Where, W is the water-containing state, m is the absolute dry mass of the recycled aggregates, U is the moisture content of the recycled aggregates, S is the water absorption rate of the recycled aggregates, and P is the pore pressure inside the aggregates.

[0018] Preferably, in step S1, the moisture content and water absorption rate of the recycled aggregates are measured according to GB / T 17431.2 "Lightweight Aggregates and Their Test Methods" and JGJ52-2006 "Standard for Quality and Inspection Methods of Sands and Gravels for Ordinary Concrete".

[0019] Preferably, in step S4, the fitting relationship between the pore pressure inside the recycled aggregates and water absorption and release is Q = 0.62 * P, where Q is the water absorption and release amount and P is the internal pore pressure.

[0020] (3) Beneficial effects

[0021] The present invention provides a test device and a test method for the water absorption and release performance of recycled aggregates, having the following beneficial effects:

[0022] (1) For the test device for the water absorption and release performance of recycled aggregates provided by this solution, since the traditional U-shaped tube is easily affected by environmental factors such as wind force and air pressure, resulting in large fluctuations in the measured pressure, the present invention reduces errors by using a rigid plastic tube and is equipped with detection heads of different apertures, and can select the pore pressure range to be tested according to requirements, with accurate measurement. Combined with digital acquisition, real-time monitoring of recycled aggregates is achieved.

[0023] (2) For the test method for the water absorption and release performance of recycled aggregates provided by this solution, through the functional relationship between the internal pore pressure and the water content state of recycled aggregates, the microscopic pressure measured by the U-shaped tube is intuitively manifested as the macroscopic water content state of recycled aggregates, having high social and economic benefits. Description of the drawings

[0024] Figure 1 is a test device for the water absorption and release performance of recycled aggregates provided in Embodiment 1 of the present invention;

[0025] Figure 2 is a time-varying diagram of the water content state of recycled aggregates at different time points in Embodiment 1 of the present invention;

[0026] Figure 3 is a curve of the change in the pore pressure inside recycled aggregates at different time points in Embodiment 1 of the present invention;

[0027] Figure 4 is a comparison of curve fitting of two different test schemes for recycled aggregates in Embodiment 1 of the present invention;

[0028] Figure 5 is a fitting relationship curve between the internal pore pressure and the water absorption and release amount of recycled aggregates in Embodiment 1 of the present invention;

[0029] Among them, 1. Detection head; 2. Chuck; 3. Plastic tube; 4. U-shaped pressure tube; 5. Pressure sensor; 6. Data collector; 7. Conversion line. Detailed implementation manners

[0030] To better illustrate and elaborate the content of the present invention, the following will be described in detail with reference to specific embodiments.

[0031] Embodiment 1

[0032] A test device for the water absorption and release performance of recycled aggregates, as Figure 1As shown, it includes a detection head 1, a chuck 2, a plastic pipe 3, a U-shaped pressure pipe 4, a pressure sensor 5, and a data collector 6. One end of the plastic pipe 3 is connected to the U-shaped pressure pipe 4, and the other end is connected to the detection head 1 through the chuck 2. The pressure sensor 5 is located on the pipe wall of the U-shaped pressure pipe 4. The pressure sensor 5 is connected to the data collector 6 through a converter 7. Among them, the aperture of the detection head 1 can be selected from any one of 1 mm, 3 mm, 6 mm, and 8 mm. According to the particle size of different recycled aggregates, a suitable detection head 1 is selected. The liquid in the U-shaped pressure pipe 4 is water, and liquid paraffin with a height of 5 mm is injected on both sides of the water. The density of the liquid paraffin is 860 kg / m 3 , By injecting liquid paraffin on both sides of the water, the evaporation of water can be prevented.

[0033] To test the feasibility of the test device for detecting the water absorption and release performance of recycled aggregates in this application, the following tests are carried out:

[0034] Weigh 2 kg of recycled aggregates. According to GB / T 17431.2 "Lightweight Aggregates and Their Test Methods" and JGJ52-2006 "Standard for Quality and Test Methods of Sand and Gravel for Ordinary Concrete", its water absorption rate is measured to be 6.8%. Place it in an oven and dry it at 105°C until it reaches a constant weight. Then immerse the recycled aggregates in water, use a hydrostatic balance to measure the mass change of the recycled aggregates within 2 hours, and calculate the water content state of the recycled aggregates at each time point to draw a water absorption time-varying diagram, as Figure 2 shown; Take the recycled aggregates and place them in an oven to dry at 105°C until they reach a constant weight. Select a detection head 1 with an aperture of 6 mm and fix it with a chuck 2. Drill a hole in the recycled aggregates to the center, insert the fixed detection head 1 into the hole and seal it. Check whether the plastic pipe 3 is tightly connected to the chuck 2 and the U-shaped pressure pipe 4. Check whether the liquids at both ends of the U-shaped pressure pipe are balanced. Place the recycled aggregates in water and read the capillary tension of the recycled aggregates within 2 hours to draw a curve of pressure change over time, as Figure 3 shown. Compare the fitting curves of the above two methods. For the same batch of aggregates, the fitting curves of the two methods are highly consistent, as Figure 4 shown. Therefore, the improved U-shaped pressure pipe can be used to detect the water absorption and release performance of recycled aggregates.

[0035] The following is a measurement using the test device for detecting the water absorption and release performance of recycled aggregates provided in this embodiment. The specific steps are as follows:

[0036] S1. Weigh 2 kg of recycled aggregates. According to GB / T 17431.2 "Lightweight Aggregates and Their Test Methods" and JGJ52-2006 "Standard for Quality and Test Methods of Sand and Gravel for Ordinary Concrete", test the water absorption rate of the recycled aggregates to be 6.8%, and the initial moisture content is 0%.

[0037] S2. Drill a hole in the recycled aggregate to the center, insert the fixed probe 1 into the hole to keep the liquid in the U-shaped pressure pipe balanced, and seal it;

[0038] S3. Place the recycled aggregate in water, measure the real-time changes inside the recycled aggregate through the pressure sensor, read through the data collector, and draw the fitting relationship curve of the pore pressure and water absorption / discharge in the recycled aggregate, as Figure 5 shown, and obtain the fitting relationship between the pore pressure and water absorption / discharge in the recycled aggregate, Q = 0.62 * P, where Q is the water absorption / discharge amount and P is the internal pore pressure;

[0039] S4. Utilize the fitting relationship between the pore pressure and water absorption / discharge in the recycled aggregate to obtain the water content states corresponding to different internal pore pressures of the recycled aggregate through Equation I. Equation I is where W is the water content state, m is the absolutely dry mass of the recycled aggregate, U is the water content of the recycled aggregate, and S is the water absorption rate of the recycled aggregate.

[0040] Through the above method, the present invention can detect the water content states of recycled aggregates at different times, with simple operation and accurate measurement, providing a data basis for the use of recycled aggregates.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A testing device for the water absorption and release performance of recycled aggregate, characterized in that: It comprises a detection head (1), a clamp (2), a plastic tube (3), a U-shaped pressure tube (4), a pressure sensor (5) and a data acquisition device (6); One end of the plastic tube (3) is connected to the U-shaped pressure tube (4), and the other end is connected to the detection head (1) via the clamp (2); the pressure sensor (5) is located on the tube wall of the U-shaped pressure tube (4), and the pressure sensor (5) is connected to the data acquisition device (6) via a conversion line (7).

2. A testing device for the water absorption and release performance of recycled aggregate according to claim 1, characterized in that: The aperture of the detection head (1) is selected from any one of 1 mm, 3 mm, 6 mm, and 8 mm.

3. The testing device for the water absorption and release performance of recycled aggregate according to claim 1, characterized in that: The liquid in the U-shaped pressure tube (4) is water, and liquid paraffin is injected at a height of 5 mm on both sides of the water.

4. A method for testing the water absorption and release properties of recycled aggregate, characterized in that: The measurement is performed using the test device according to any one of claims 1 to 3, comprising the following steps: S1. Calculate the water absorption rate and initial moisture content of recycled aggregate; S2. Drill a hole to the center of the recycled aggregate, insert the probe into the hole to keep the liquid balance in the U-shaped pressure tube, and seal it; S3, placing the recycled aggregate in air, water or slurry, measuring the real-time change of the pore pressure inside the recycled aggregate through a pressure sensor, and reading it through a data collector; S4. Using the fitting relationship between the internal pore pressure of recycled aggregate and the absorbed and released water, the water content corresponding to the internal pore pressure of different recycled aggregates is obtained by formula I. Formula I is: Among them, W is the moisture state, m is the absolute dry mass of recycled aggregate, U is the moisture content of recycled aggregate, S is the water absorption rate of recycled aggregate, and P is the pore pressure inside aggregate.

5. The method for testing the water absorption and release performance of recycled aggregate according to claim 4, characterized in that: In step S1, the moisture content and water absorption of the recycled aggregate are tested according to GB / T 17431.2 "Lightweight Aggregate and Its Test Methods" and JGJ52-2006 "Standard for Quality and Test Methods of Sand and Stone for Ordinary Concrete".

6. The method for testing the water absorption and release performance of recycled aggregate according to claim 4, characterized in that: In step S4, the fitting relationship between the internal pore pressure and the absorbed and released water of the recycled aggregate is Q=0.62*P, wherein Q is the amount of absorbed and released water, and P is the internal pore pressure.

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