CN102590061A - Device and method for evaluating concrete permeability simply and quickly - Google Patents

Abstract

The invention provides a device and method for simply and quickly evaluating the permeability of concrete, which relates to a device and a method for evaluating the permeability of concrete. The present invention aims at the problems of complex devices for detecting the permeability of concrete, complicated operation of the detection method and limited application range. Device scheme: the cylindrical concrete test block is set on the turntable, the cylindrical box body filled with water is set in the cylindrical through hole, the top of the cylindrical box body filled with water is provided with a box cover, and the microwave oven is equipped with a steel plate, a steel plate There is a rectangular opening on the top; the method scheme: put the cylindrical concrete test block on the turntable of the microwave oven for the first heating; put the cylindrical concrete test block into a container filled with water for immersion, the soaking time is t, and the cylinder The cylindrical concrete test block is placed on the turntable of the microwave oven for the second heating; the heat difference Q absorbed by the cylindrical concrete test block after two heatings is calculated, and the permeability of the concrete is evaluated by the ratio of Q/t. The invention detects the permeability of concrete.

Description

Device and method for simple and rapid evaluation of concrete permeability

technical field

The invention relates to a device and method for evaluating the permeability of concrete.

Background technique

Permeability in concrete is a comprehensive index, which refers to the ease of penetration, diffusion or migration of gases, liquids or ions in concrete under the action of pressure, chemical potential or electric field. The permeability of concrete is closely related to the durability of concrete, and it is one of the most important indicators for evaluating the quality of concrete. Concrete with good impermeability can resist the influence of all external erosive media and greatly improve the durability of concrete. In my country, the test method of concrete permeability is mainly permeable method at first, which is characterized by impermeability grade, permeability coefficient and water seepage height. In recent years, more and more electrical parameter evaluation methods such as chloride ion flux method (ASTM C1202), rapid chloride ion transfer coefficient method (RCM method) and salt-saturated concrete conductivity method (NEL method) have been applied to evaluate high strength and high performance. concrete. The operating equipment of the permeable method is relatively complicated, the test piece needs to be sealed, the operation is cumbersome, and the test time is long. For high-strength and high-performance concrete, only the penetration height can be used to evaluate, but the measurement value of the penetration height is not easy to be accurate. The chloride ion electric flux method is easy to cause electrode heating due to the long test time. In addition, the electrical parameter evaluation method is not suitable for steel fiber concrete and concrete mixed with salt admixtures, and its scope of application is limited to a certain extent. Therefore, it is necessary to design a simple measuring device and a rapid and widely applicable evaluation method for the comparative test of the permeability of large quantities of concrete and the evaluation of the permeability of concrete at the construction site.

Contents of the invention

The object of the present invention is to provide a simple and fast device and method for evaluating the permeability of concrete, so as to solve the problems of complicated devices for detecting the permeability of concrete, complex operation of the detection method and limited application range.

The technical solution adopted by the present invention to solve the above technical problems is: device solution: the device includes a microwave oven and a turntable, the bottom of the microwave oven is provided with a turntable, and the device also includes a cylindrical box body filled with water, a lid and a steel plate , the cylindrical concrete test block is set on the turntable, the cylindrical concrete test block is provided with a cylindrical through hole along the axial direction, the cylindrical box body filled with water is set in the cylindrical through hole, and the cylindrical box body filled with water A box cover is provided on the top, a steel plate is provided inside the microwave oven, and a rectangular opening is provided on the steel plate, and the height of the rectangular opening is consistent with the height of the cylindrical concrete test block;

Method scheme: the method includes the following steps: Step 1. First, fill the cylindrical box with water and put it into the cylindrical through hole, then put the cylindrical concrete test block on the turntable of the microwave oven for the first heating, After heating, take out the cylindrical concrete test block, and immediately measure the temperature T ₁ of the water in the cylindrical box filled with water. The selection of heating power and heating time should ensure that T ₁ ≤ 80°C;

Step 2, after taking out the cylindrical concrete test block, after the temperature drops to room temperature, put the cylindrical concrete test block into a container filled with water for soaking, and the soaking time is t;

Step 3. After taking out the cylindrical concrete test block, make the cylindrical concrete test block reach the dry state, put the cylindrical concrete test block on the turntable of the microwave oven for the second heating, the heating power and heating time are the same as the first heating same;

Step 4: Take out the cylindrical concrete test block after heating and measure the temperature T ₂ of the water in the cylindrical box, and calculate the heat difference absorbed by the cylindrical concrete test block after two heatings according to the heat calculation formula Q=cm·ΔT, where ΔT =T ₂ -T ₁ , use the ratio of Q/t to evaluate the concrete permeability.

The present invention has the following beneficial effects: 1. The device of the present invention has a simple structure and only needs to be improved on the microwave oven used in daily life; it is convenient and easy to obtain and low in cost. 2. The evaluation method of the present invention only needs to monitor the change of water temperature and soaking time in a specific container before and after soaking the concrete sample, and calculate the Q/t to characterize the permeability of the concrete. It is simple and easy, and the test time only needs a few minutes. Compared with other evaluation methods, the test time is greatly shortened. At present, the electric flux method needs 6 hours, and the water pressure method is uncertain, especially for high-strength concrete. The test time is very long. Considering the pretreatment time of concrete samples required by these methods, such as Drying, vacuum saturation, etc. need at least 24 hours. However, the present invention considers microwave heating and drying to constant weight, greatly shortens the test cycle again, and is easy to operate.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention.

Detailed ways

Specific embodiment one: illustrate this embodiment in conjunction with Fig. 1, the device of this embodiment comprises microwave oven 5 and turntable 6, and the bottom in microwave oven 5 is provided with turntable 6, and described device also comprises cylindrical box body 2 that water is housed, The box cover 4 and the steel plate 7, the cylindrical concrete test block 1 is arranged on the turntable 6, the cylindrical concrete test block 1 is provided with a cylindrical through hole 1-1 along the axial direction, and the cylindrical box body 2 with water is arranged on the cylindrical In the shaped through hole 1-1, the top of the cylindrical box body 2 that is equipped with water is provided with a lid 4, and the microwave oven 5 is provided with a steel plate 7, and the steel plate 7 is provided with a rectangular opening 8, and the height of the rectangular opening 8 is the same as that of the cylindrical concrete. Test block 1 has the same height.

Specific embodiment two: the method of the present embodiment comprises the following steps: step one, at first put into the cylindrical through hole 1-1 after being filled with water in the cylindrical box body 2, then put the cylindrical concrete test block 1 Carry out the first heating on the turntable 6 of the microwave oven 5, take out the cylindrical concrete test block 1 after heating, and immediately measure the temperature T ₁ of the water in the cylindrical box body 2 filled with water, and the selection of heating power and heating time should ensure that T ₁ ≤80°C;

Step 2, after taking out the cylindrical concrete test block 1, after the temperature drops to room temperature, wherein the temperature of the room temperature is 18-25 degrees Celsius, put the cylindrical concrete test block 1 into a container filled with water for soaking, and the soaking time is t, t is determined according to the type of concrete;

Step 3: After taking out the cylindrical concrete test block 1, make the cylindrical concrete test block reach a dry state, put the cylindrical concrete test block 1 on the turntable 6 of the microwave oven 5 for the second heating, the heating power and heating time are the same as Same as the first heating;

Step 4: Take out the cylindrical concrete test block 1 after heating and measure the temperature T ₂ of the water in the cylindrical box body 2, and calculate the heat difference absorbed by the cylindrical concrete test block 1 after two heatings according to the heat calculation formula Q=cm·ΔT Value, where ΔT = T ₂ -T ₁ , the ratio of Q/t is used to evaluate the permeability of concrete.

The above steps are performed on samples taken from various actual concrete working conditions without considering the initial moisture content of concrete samples, and can be used for comparative evaluation and analysis of concrete permeability in different areas and parts in actual engineering. In addition, if it is necessary to consider that the concrete samples have the same benchmark and remove the influence of the initial moisture content of the concrete samples, the routine practice in the laboratory is to dry the concrete samples in an oven at 105°C for 24 hours to constant weight. In the present invention, the concrete sample Put it in a microwave oven and select a low-power gear to dry until it reaches a constant weight, and then continue to repeat the test from step 1 to step 4. The drying time of the concrete sample is greatly shortened by using the microwave heating method.

Specific embodiment three: the heating power in step one of this embodiment is 750W-1500W, and the heating time is 45 seconds-180 seconds. This power is the power commonly used in microwave ovens, and the operation is simple and convenient. Other steps are the same as in the second embodiment.

Embodiment 4: The soaking time of cylindrical concrete test block 1 in step 2 in step 2 of this embodiment is 2-24 hours, and the soaking time is selected according to the variety of concrete. Other steps are the same as those in Embodiment 2 or 3.

Specific embodiment five: cylindrical concrete test block 1 diameter is 150mm, and height is 80mm, and center hole diameter is 50mm, and packs plastic cylindrical box body 2 in center hole, and box outer diameter is 50mm, and inner diameter is 44mm, and height is 80mm, The height of the rectangular window 8 is 80mm, the width is 20mm, and the thickness of the steel plate is 3mm. Inject 100ml of water into the plastic cylindrical box body 2, cover the box lid 4, put the cylindrical concrete test block 1 into the center of the turntable 6 in the microwave oven 5, and the microwave oven 5 has functions of power adjustment, power digital display, and heating time setting Function, adjust the output power of the microwave oven to 1000W, the microwave emitted by the microwave oven 5 passes through the rectangular window 8 of the steel plate 7, and radially shoots on the cylindrical concrete test block 1, the heating time is 120 seconds, take out the cylindrical concrete test block 1 after heating, Open the lid 4 to measure the temperature of the water in the cylindrical box body 2, immerse the cylindrical concrete test block 1 in a container filled with water, take out the cylindrical concrete test block 1 after soaking for 2 hours, wipe off its surface moisture with a damp cloth When it reaches the surface-dry state, put the cylindrical concrete test block 1 on the turntable 6 of the microwave oven 5 again, and reheat the cylindrical concrete test block 1 with the microwave oven 5. The heating time and heating power are the same as the first time, and take it out after heating. For the cylindrical concrete test block 1, measure the temperature inside the plastic cylindrical box 2 again, use the secondary temperature difference to calculate the heat absorbed by the concrete after immersion, and use the ratio of Q/t as an index to evaluate the permeability of the concrete.

Water molecules are polar molecules. When microwaves pass through water, water has a strong ability to absorb microwave energy. The amount of moisture contained in the concrete is related to the value of the reduction of the microwave intensity of the microwave passing through the concrete. Heating the cylindrical concrete test block for the first time, the temperature of the water in the plastic cylindrical box body 2 rises, and the microwave passes through the unsoaked cylindrical concrete test block 1, and the cylindrical concrete test block 1 absorbs part of the energy of the microwave, and its value is the same as that of the concrete The components are related; the second heating of the cylindrical concrete test block 1, the microwave passes through the cylindrical concrete test block 1 that has penetrated into the water, and because the cylindrical concrete test block 1 contains water, the test block absorbs more microwave energy, and the microwave intensity reduce, the temperature rise of the water in the plastic cylindrical box body 2 is small, and the temperature difference after the water in the plastic cylindrical box body 2 is heated twice is related to the amount of moisture infiltrated into the concrete test block. The ratio of Q/t obtained in the method can be used as An indicator for evaluating the permeability of concrete.

The concrete structure is loose and porous, and the permeability is high. When soaking, more water enters the interior of the concrete, and the heat value absorbed by the concrete when heated is larger. The larger the ratio of Q/t under the same test conditions, the higher the permeability of the concrete.

Claims (4)

1. the device of a simple and easy quick evaluation concrete permeability; Said device comprises micro-wave oven (5) and rotating disk (6); Bottom in the micro-wave oven (5) is provided with rotating disk (6), it is characterized in that said device also comprises cylindrical box body (2), lid (4) and the steel plate (7) that water is housed, and cylindrical concrete test block (1) is located on the rotating disk (6); Cylindrical concrete test block (1) is provided with cylindrical hole (1-1) vertically; The cylindrical box body (2) that water is housed is located in the cylindrical hole (1-1), and cylindrical box body (2) top that water is housed is provided with lid (4), is provided with steel plate (7) in the micro-wave oven (5); Steel plate (7) is provided with oblong openings (8), and the height of oblong openings (8) is consistent with the height of cylindrical concrete test block (1).

2. method that adopts the simple and easy quick evaluation concrete permeability of the said device of claim 1; It is characterized in that said method comprising the steps of: step 1, at first after filling water in the cylindrical box body (2), put into cylindrical hole (1-1); Then cylindrical concrete test block (1) is placed on and carries out the heating first time on the rotating disk (6) of micro-wave oven (5); Cylindrical concrete test block (1) is taken out in the heating back, measures the temperature T of the interior water of cylindrical box body (2) that water is housed immediately ₁, choosing of heating power and heat time heating time will be guaranteed T ₁≤80 ℃;

Step 2, take out cylindrical concrete test block (1) after, treat that temperature is reduced to room temperature after, the container of cylindrical concrete test block (1) being put into filled with water soaks, soak time is t;

Step 3, take out cylindrical concrete test block (1) after; Make cylindrical concrete test block reach the surface drying state; Cylindrical concrete test block (1) is placed on and carries out the heating second time on the rotating disk (6) of micro-wave oven (5), and heating power all heats identical with the first time with heat time heating time;

The temperature T that cylindrical concrete test block (1) is measured the interior water of cylindrical box body (2) is taken out in step 4, heating back ₂, calculate the heat difference that cylindrical concrete test block (1) absorbs after twice heating, wherein Δ T=T according to heat Calculation formula Q=cm Δ T ₂-T ₁, concrete permeability is estimated with the ratio of Q/t.

According to the said simple and easy quick evaluation concrete permeability of claim 4 method, it is characterized in that heating power is 750W-1500W in the step 1, be 45 seconds-180 seconds heat time heating time.

According to the said simple and easy quick evaluation concrete permeability of claim 5 method, it is characterized in that the time that cylindrical concrete test block (1) in the step 2 soaks is 2-24 hour.

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