Instrument and method for measuring high-temperature thermal expansion of concrete
阅读说明：本技术 一种测定混凝土高温热膨胀的仪器及方法 (Instrument and method for measuring high-temperature thermal expansion of concrete ) 是由 赵杰 王孟奇 王明月 曾笛波 蒋玉川 任之东 康锐 王阳 杨娟 于 2021-08-11 设计创作，主要内容包括：本申请公开了一种测定混凝土高温热膨胀的仪器及方法,涉及测量仪器技术领域。包括测量系统、传导系统、测温部件、控温部件和数据处理系统,测量系统包括位移传感器和第一循环水冷套,第一循环水冷套与炉体之间具有间隙；位移传导系统包括顶杆、置物柱,顶杆的一端与位移传感器的探针抵接,另一端依次穿过第一支架、第一循环水冷套、炉壁后延伸至炉膛内；置物柱的一端穿过炉门并通过第二循环水冷套放置在第二支架上,第二支架与炉门连接；数据处理系统被配置为：根据实测温度、试样膨胀值、试样原始高度和膨胀补偿值,计算得到试样在不同温度下的热膨胀百分率及热膨胀系数。本申请用于精确测量具有大尺寸范围的试样的热膨胀百分率及热膨胀系数。(The application discloses an instrument and a method for measuring high-temperature thermal expansion of concrete, and relates to the technical field of measuring instruments. The device comprises a measuring system, a conduction system, a temperature measuring component, a temperature control component and a data processing system, wherein the measuring system comprises a displacement sensor and a first circulating water cooling jacket, and a gap is formed between the first circulating water cooling jacket and a furnace body; the displacement conduction system comprises an ejector rod and an object placing column, one end of the ejector rod is abutted against a probe of the displacement sensor, and the other end of the ejector rod sequentially penetrates through the first support, the first circulating water cooling jacket and the furnace wall and then extends into the furnace chamber; one end of the object placing column penetrates through the furnace door and is placed on a second bracket through a second circulating water cooling jacket, and the second bracket is connected with the furnace door; the data processing system is configured to: and calculating the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the measured temperature, the sample expansion value, the original height of the sample and the expansion compensation value. The present application is used for accurately measuring the thermal expansion percentage and the thermal expansion coefficient of a sample having a large size range.)
1. The utility model provides an instrument of survey concrete high temperature thermal energy which characterized in that, includes measurement system, furnace body, displacement conduction system, temperature measurement part, accuse temperature part and data processing system, wherein:
the measuring system comprises a displacement sensor, a first bracket and a first circulating water cooling jacket which are sequentially arranged, and a gap is formed between the first circulating water cooling jacket and the furnace body;
the furnace body is positioned below the measuring system and used for providing required temperature for the thermal expansion of the sample;
the displacement transmission system comprises an ejector rod, a storage column and a second support, wherein one end of the ejector rod is abutted against a probe of the displacement sensor, and the other end of the ejector rod sequentially penetrates through the first support, the first circulating water cooling jacket and the furnace wall and then extends into a furnace chamber of the furnace body; the article placing column is positioned below the ejector rod, one end of the article placing column penetrates through a furnace door at the bottom of the furnace body and is placed on a second support through a second circulating water cooling jacket, and the second support is connected with the furnace door;
the temperature measuring component is used for measuring the temperature of the hearth;
the temperature control component is used for controlling the temperature inside the hearth according to the hearth temperature measured by the temperature measurement component and a preset temperature rise system;
the data processing system is configured to: acquiring the hearth temperature measured by the temperature measuring component and the sample expansion value measured by the displacement sensor in real time;
and calculating to obtain the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the real-time acquired furnace temperature, the sample expansion value, the preset original size of the sample and the expansion compensation value, wherein the expansion compensation value is the difference value between the thermal expansion value of the standard sample and the real thermal expansion value of the standard sample measured by adopting the same temperature rise system as the sample, the height of the standard sample is the same as that of the sample, and the standard sample is made of fused quartz.
2. The apparatus as claimed in claim 1, wherein the distance between the first circulating water cooling jacket and the furnace body is greater than 10 mm.
3. The instrument for measuring the high-temperature thermal expansion of concrete according to claim 1, wherein the furnace body comprises a shell and an insulating layer, a spiral groove is formed in the inner wall of the insulating layer, a bare resistance wire is wound in the spiral groove, and the resistance wire is connected with the temperature control component.
4. The apparatus according to claim 1, wherein the second bracket comprises a circular hole plate and a supporting plate, the circular hole plate is connected with the furnace door through a connecting piece, the supporting plate is used for supporting the second water cooling jacket and the object placing column, and a first lifting device for controlling the opening and closing of the furnace door is arranged at the bottom of the supporting plate;
one end of the second circulating water cooling jacket is fixed on the supporting plate, the other end of the second circulating water cooling jacket penetrates through the round hole plate, and the bottom of the storage column is arranged in the second water cooling jacket; the outer diameter of the second circulating water cooling jacket is smaller than the diameter of a circular hole of the circular hole plate, and a gap is formed between the second circulating water cooling jacket and the furnace door.
5. The apparatus for measuring high temperature thermal expansion of concrete according to claim 1, further comprising a second elevating means for adjusting the height of the displacement sensor, said second elevating means being fixed to the upper surface of the first bracket.
6. The apparatus according to claim 1, wherein a backing plate for placing the sample is disposed on the top of the placing column, and the backing plate, the ejector rod, and the placing column are made of fused quartz.
7. The apparatus according to claim 1, wherein the holding pillar is provided with a heat insulating block on at least a portion of an outer wall of the holding pillar located in the cavity.
8. A method for measuring high temperature thermal expansion of concrete, which is based on the apparatus for measuring high temperature thermal expansion of concrete as claimed in any one of claims 1 to 7, comprising the steps of:
step 1: inputting an expansion compensation value and the original size of the sample into a data processing system, wherein the expansion compensation value is the difference value between the thermal expansion value of a standard sample measured by adopting the same temperature rise system as that of the sample and the real thermal expansion value of the standard sample, the height of the standard sample is the same as that of the sample, and the standard sample is made of fused quartz;
step 2: opening the furnace door, placing the sample on the object placing column, closing the furnace door, and starting a temperature rise test after the readings of the displacement sensor are unchanged;
and step 3: the temperature measuring component measures the temperature of the hearth in real time; the temperature control component controls the temperature inside the hearth according to the measured hearth temperature and a preset temperature rise system;
the data processing system acquires the furnace temperature measured by the temperature measuring component and the sample expansion value measured by the displacement sensor in real time, and calculates the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the original size of the sample, the sample expansion value, the furnace temperature and the expansion compensation value.
9. The method for measuring the high-temperature thermal expansion of concrete according to claim 8, wherein the original size of the sample is determined according to one of the methods that the minimum section side length of the sample is longer than the maximum aggregate grain diameter, and the longest fiber length is 3 times;
the temperature-raising system is determined by carrying out an auxiliary test or pre-analysis;
the step 2 specifically comprises: raising the displacement sensor, opening the furnace door, placing the sample on the object placing column, closing the furnace door, lowering the displacement sensor, and starting a temperature rise test after the reading of the displacement sensor is unchanged;
the calculation formulas of the thermal expansion percentage and the thermal expansion coefficient in the step 3 are respectively as follows:
in the formula: t is t0Is the initial temperature; t is t1Is the test temperature; l is0For the sample at t0Height at temperature; l is1For the sample at t1Temperature considerations the height of the expansion compensation value.
10. The method for determining high temperature thermal expansion of concrete according to claim 9, wherein step 2 further comprises: if the sample is high-strength and ultrahigh-strength concrete, the sample needs to be dried before being placed on the storage column.
Technical Field
The application relates to the technical field of measuring instruments, in particular to an instrument and a method for measuring high-temperature thermal expansion of concrete.
Background
The high-temperature thermal expansion performance of concrete is related to the safety of a concrete structure or a member under high-temperature conditions such as fire and the like, and is also one of important parameters for designing high-temperature resistance and fire resistance of concrete materials and structures, however, an instrument and a method suitable for measuring the high-temperature thermal expansion performance of concrete are not available at present.
The national standard GB/T7320 and 2018, refractory material thermal expansion test method, gives two refractory material test methods, namely a differential method and a mandril method, but the methods are not suitable for high-temperature thermal expansion measurement of concrete. The reason is that aggregates exist in concrete, if fiber concrete also exists, the differential method requires a through hole to be reserved in the center of a small sample, the operability for concrete is poor, and the ejector rod method requires the sample size to be too small, so that the sample cannot represent the concrete. The existing high-temperature thermal expansion measuring instruments are manufactured according to GB/T7320-2018 'method for testing thermal expansion of refractory materials', so that the instruments are not suitable for measuring the thermal expansion of concrete.
The prior high temperature thermal expansion patents which can measure larger size samples: both CN 205982147U, CN 106226347A, CN 208568645U and CN 111044556A have design defects, and are not suitable for measuring the high-temperature thermal expansion of concrete.
Disclosure of Invention
The application provides an instrument and a method for measuring high-temperature thermal expansion of concrete, wherein a displacement sensor and a furnace body are separately arranged on a first support and the deformation of a displacement conduction system is compensated, so that the defect that the displacement sensor is easily affected by high temperature is avoided, and meanwhile, the thermal expansion percentage and the thermal expansion coefficient of a large-size sample are accurately measured.
On the one hand, the application provides an instrument of survey concrete high temperature thermal energy, including measurement system, furnace body, displacement conduction system, temperature measurement part, accuse temperature part and data processing system, wherein:
the measuring system comprises a displacement sensor, a first bracket and a first circulating water cooling jacket which are sequentially arranged, and a gap is formed between the first circulating water cooling jacket and the furnace body;
the furnace body is positioned below the measuring system and used for providing required temperature for the thermal expansion of the sample;
the displacement transmission system comprises an ejector rod, a storage column and a second support, wherein one end of the ejector rod is abutted against a probe of the displacement sensor, and the other end of the ejector rod sequentially penetrates through the first support, the first circulating water cooling jacket and the furnace wall and then extends into a furnace chamber of the furnace body; the article placing column is positioned below the ejector rod, one end of the article placing column penetrates through a furnace door at the bottom of the furnace body and is placed on a second support through a second circulating water cooling jacket, and the second support is connected with the furnace door;
the temperature measuring component is used for measuring the temperature of the hearth;
the temperature control component is used for controlling the temperature inside the hearth according to the hearth temperature measured by the temperature measurement component and a preset temperature rise system;
the data processing system is configured to: acquiring the hearth temperature measured by the temperature measuring component and the sample expansion value measured by the displacement sensor in real time;
and calculating to obtain the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the real-time acquired furnace temperature, the sample expansion value, the preset original size of the sample and the expansion compensation value, wherein the expansion compensation value is the difference value between the thermal expansion value of the standard sample and the real thermal expansion value of the standard sample measured by adopting the same temperature rise system as the sample, the height of the standard sample is the same as that of the sample, and the standard sample is made of fused quartz.
Further, the distance between the first circulating water cooling jacket and the furnace body is larger than 10 mm.
The furnace body further comprises a shell and a heat preservation layer, wherein a spiral groove is formed in the inner wall of the heat preservation layer, an exposed resistance wire is coiled in the spiral groove, and the resistance wire is connected with a temperature control component.
The second bracket comprises a round hole plate and a support plate, the round hole plate is connected with the furnace door through a connecting piece, the support plate is used for supporting the second water cooling jacket and the object placing column, and the bottom of the support plate is provided with a first lifting device used for controlling the opening and closing of the furnace door;
one end of the second circulating water cooling jacket is fixed on the supporting plate, the other end of the second circulating water cooling jacket penetrates through the round hole plate, and the bottom of the storage column is arranged in the second water cooling jacket; the outer diameter of the second circulating water cooling jacket is smaller than the diameter of a circular hole of the circular hole plate, and a gap is formed between the second circulating water cooling jacket and the furnace door.
Further, the lifting device comprises a second lifting device for adjusting the height of the displacement sensor, and the second lifting device is fixed on the upper surface of the first support.
Furthermore, a base plate for placing a sample is arranged at the top end of the object placing column, and the base plate, the ejector rod and the object placing column are all made of fused quartz.
Furthermore, the outer wall of at least one part of the storage column in the hearth is sleeved with a heat insulation block.
In another aspect, the present invention further provides a method for measuring the high temperature thermal expansion of concrete, which is based on an apparatus for measuring the high temperature thermal expansion of concrete, and comprises the following steps:
step 1: inputting an expansion compensation value and the original size of the sample into a data processing system, wherein the expansion compensation value is the difference value between the thermal expansion value of a standard sample measured by adopting the same temperature rise system as that of the sample and the real thermal expansion value of the standard sample, the height of the standard sample is the same as that of the sample, and the standard sample is made of fused quartz;
step 2: opening the furnace door, placing the sample on the object placing column, closing the furnace door, and starting a temperature rise test after the readings of the displacement sensor are unchanged;
and step 3: the temperature measuring component measures the temperature of the hearth in real time; the temperature control component controls the temperature inside the hearth according to the measured hearth temperature and a preset temperature rise system;
the data processing system acquires the furnace temperature measured by the temperature measuring component and the sample expansion value measured by the displacement sensor in real time, and calculates the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the original size of the sample, the sample expansion value, the furnace temperature and the expansion compensation value.
Further, the original size of the sample is determined according to one of methods that the minimum section side length and the diameter of the sample are larger than the maximum aggregate grain diameter and the longest fiber length is 3 times;
the temperature-raising system is determined by carrying out an auxiliary test or pre-analysis;
the step 2 specifically comprises: raising the displacement sensor, opening the furnace door, placing the sample on the object placing column, closing the furnace door, lowering the displacement sensor, and starting a temperature rise test after the reading of the displacement sensor is unchanged;
the calculation formulas of the thermal expansion percentage and the thermal expansion coefficient in the step 3 are respectively as follows:
in the formula: t is t0Is the initial temperature; t is t1Is the test temperature; l is0For the sample at t0Height at temperature; l is1For the sample at t1Temperature considerations the height of the expansion compensation value.
Further, step 2 further comprises: if the sample is high-strength and ultrahigh-strength concrete, the sample needs to be dried before being placed on the storage column.
Compared with the prior art, the application has the following beneficial effects:
1) the thermal expansion of the sample in the temperature range of 20-1000 ℃ can be measured, and the thermal expansion percentage and the thermal expansion coefficient can be automatically calculated; simple operation and long-time continuous measurement.
2) The size and the temperature raising system of the sample to be tested can be flexibly selected and used, and the precision is high.
The method is suitable for the prism or cylinder with the sample size of 40-100 mm bottom side length or diameter and 50-160 mm height, the heating rate is 0.1-20 ℃/min, the temperature control precision is +/-1 ℃, and the instrument measurement precision is 1 micron.
3) The sample is positioned in the displacement transmission system, and the displacement transmission system passes through the hearth and is not influenced by hearth deformation, so that the error is extremely small.
4) Displacement sensor and furnace body separation lay alone on first support to carry out circulating water cooling through first circulation water-cooling jacket, realize the effective cooling of quartz rod top and first support, make displacement sensor not receive the influence of high temperature, guarantee displacement sensor normal work and survey the precision of displacement.
5) The quartz storage column supporting plate at the lower part is effectively cooled through the second circulating water cooling jacket, the displacement conduction system is not affected by high-temperature deformation of the supporting plate, and the testing precision and the service life of an instrument are guaranteed.
6) The hearth is heated by exposed resistance wires wound in the groove of the furnace wall, and temperature control is carried out by a temperature measuring part inside the hearth and a temperature control part connected with the temperature measuring part. Because the resistance wire is exposed, accurate temperature control can be realized, and temperature control delay and temperature fluctuation are eliminated.
7) The quartz standard sample with known thermal expansion coefficient is adopted for calibration, the deformation of a displacement conduction system is compensated, the high precision is ensured, and the system error is eliminated.
8) The test method fully considers the characteristics of the concrete material. Determining the size of a sample according to the particle size of aggregate or the length of fiber in the concrete, so that the size of the sample meets the representative requirement of a concrete material; the temperature rise system of the thermal expansion test is determined through auxiliary test or pre-analysis to ensure that the internal and external temperatures of the sample are consistent and the test precision is ensured; and the concrete with low water-cement ratio needs to be subjected to anti-cracking drying treatment.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an apparatus for measuring high temperature thermal expansion of concrete according to the present application;
FIG. 2 is a graph of percent thermal expansion and coefficient of thermal expansion versus temperature for the first embodiment;
FIG. 3 is a graph of percent thermal expansion and coefficient of thermal expansion versus temperature for the second example.
In the figure, 1-a stepping motor, 2-a displacement sensor, 3-a first circulating water cooling jacket, 4-a first bracket, 5-a mandril, 6-a thermocouple, 7-a sample, 8-a backing plate, 9-a storage column, 10-a shell, 11-a heat insulation layer, 12-a resistance wire, 13-a heat insulation block, 14-a furnace door, 15-a second circulating water cooling jacket, 16-a round hole plate, 17-a support plate and 18-a connecting piece.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referred device or element must have a specific orientation, and that the configuration and operation of the specific orientation, and therefore, should not be taken as limiting the present application.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.
The application provides an instrument and a method for measuring high-temperature thermal expansion of concrete.
The instrument adopts a vertical ejector rod method, the thermal expansion temperature range of a measured sample is 20-1000 ℃, and the instrument is suitable for a prism or a cylinder with the sample size of bottom surface side length or diameter of 40-100 mm and the height of 50-160 mm. The instrument comprises a measuring system, a furnace body, a displacement conduction system, a temperature measuring component, a temperature control component and a data processing system.
Referring to fig. 1, the measuring system includes a displacement sensor 2, a first support 4 and a first circulating water cooling jacket 3 which are arranged in sequence, the displacement sensor 2 is connected with a second lifting device, the second lifting device can be but is not limited to a stepping motor 1, the stepping motor 1 is arranged on the upper surface of the first support 4, the displacement sensor 2 is controlled to lift through the stepping motor 1, and the height is adjusted to adapt to the height size of a sample 7. The first circulating water cooling jacket 3 is fixed on the lower surface of the first support 4 and has a gap with the furnace body, the first support 4 and the displacement sensor 2 are prevented from being affected by high temperature through circulating cold water, and the testing precision and the service life of an instrument are guaranteed. The distance between the first circulating water cooling jacket 3 and the furnace body is more than 10 mm.
The furnace body is located measurement system's below, and the furnace body includes shell 10 and heat preservation 11, and the inner wall of heat preservation 11 is formed with the spiral groove, and it has naked resistance wire 12 to coil in the recess, and when the test, provides required temperature for sample 7 thermal expansion through heating resistance wire 12. The hearth of the furnace body is insulated by an insulating layer 11 so as to reduce the heat loss of the hearth and the influence of heat radiation on instruments. And because the resistance wire 12 is exposed, accurate temperature control can be realized, and temperature control delay and temperature fluctuation are eliminated. The resistance wire 12 is connected with a temperature control component.
The displacement conduction system comprises an ejector rod 5, an object placing column 9 and a second support, wherein a base plate 8 used for placing a sample 7 is further arranged at the top end of the object placing column 9, the ejector rod 5, the base plate 8 and the object placing column 9 are made of high-purity fused quartz, the fused quartz has a very small thermal expansion coefficient, the object placing column 9 and the ejector rod 5 penetrate through a hearth and are not influenced by hearth deformation. One end of the ejector rod 5 is abutted to a probe of the displacement sensor 2, and the other end of the ejector rod penetrates through the first support 4, the first circulating water cooling jacket 3 and the furnace wall in sequence and then extends into a furnace chamber of the furnace body. The object placing column 9 is located below the backing plate 8, one end of the object placing column 9 penetrates through a furnace door 14 at the bottom of the furnace body and is supported on a second support through a second circulating water cooling jacket 15, the second support is connected with the furnace door 14 through a connecting piece 18, effective cooling of the bottom of the object placing column 9 is achieved through circulating water cooling, and it is ensured that the supporting plate 17 does not generate temperature deformation. The outer wall of at least one part of the placing column 9 in the hearth is sleeved with a high-temperature resistant heat-insulating block 13.
The second bracket comprises a round hole plate 16 and a support plate 17, the round hole plate 16 is connected with the oven door 14 through a connecting piece 18, and the bottom of the support plate 17 is provided with a first lifting device for controlling the oven door 14 to open and close. One end of the second circulating water cooling jacket 15 is fixed on the supporting plate 17, the other end of the second circulating water cooling jacket passes through the round hole plate 16, the bottom of the storage column 9 is arranged in the second circulating water cooling jacket 15, and the temperature of the bottom of the storage column 9 is reduced through cooling of circulating cold water so as to ensure that the supporting plate 17 is not influenced by high temperature. The outer diameter of the second circulating water cooling jacket 15 is smaller than the diameter of the round hole plate 16, and the second circulating water cooling jacket 15 is not contacted with the round hole steel plate 16, so that the heat directly transferred by the lower furnace door 14 can be effectively isolated.
The temperature measuring part is used for measuring the temperature of the hearth and can be not limited to the thermocouple 6.
The temperature control component is used for controlling the temperature inside the hearth according to the hearth temperature measured by the temperature measurement component and a preset temperature rise system.
The data processing system is configured to: acquiring the hearth temperature measured by the temperature measuring component and the sample expansion value measured by the displacement sensor in real time;
and calculating the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the real-time acquired furnace temperature, the sample expansion value, the preset original size of the sample and the expansion compensation value, wherein the expansion compensation value is the difference value between the thermal expansion value of the quartz standard sample and the real thermal expansion value of the quartz standard sample measured by adopting the same temperature rise system as the sample, and the height of the quartz standard sample is the same as that of the sample.
The working principle of the instrument is as follows: the hearth is heated by the exposed resistance wires 12 wound in the groove of the furnace wall, the temperature is measured in real time by the thermocouple 6 in the hearth, and the temperature in the hearth is controlled by the temperature control part according to a preset temperature rise system. The tested sample 7 is erected on a backing plate 8 in a hearth, a top rod 5 above the tested sample is jacked up, the top rod 5 is connected with a displacement sensor 2, temperature deformation generated by heating of the tested sample 7 is conducted through the top rod 5, the temperature deformation is captured by the displacement sensor 2, and expansion data are recorded in real time through a data processing system. And calculating the thermal expansion percentage and the thermal expansion coefficient of the sample 7 at different temperatures by the data processing system according to the measured thermal expansion value and by considering the expansion compensation value, wherein the specific calculation formula is as follows:
percent thermal expansion:
coefficient of thermal expansion:
in the formula:
t0-an initial temperature;
t1-the test temperature;
L0sample at t0Height at temperature;
L1sample at t1Temperature considerations the height of the expansion compensation value.
The method for measuring the high-temperature thermal expansion of the concrete by using the thermal expansion tester shown in FIG. 1 comprises the following steps:
s1: sample 7 sizing
In the determination of the size, one of methods in which the minimum cross-sectional side length of the sample, the diameter is larger than the maximum aggregate particle diameter, and the longest fiber length is 3 times can be selected to determine the size of the sample. Ensure the representativeness of the sample.
S2: determination of temperature rising system
The temperature rise system for measuring the thermal expansion of the concrete sample is determined by carrying out an auxiliary test or pre-analysis, wherein the temperature rise system comprises the temperature rise rate and the constant temperature time of a constant temperature point, so that the consistency of the internal temperature and the external temperature of the sample is ensured, and the test precision is ensured.
S3: determination of expansion compensation values
Selecting a quartz sample with the same height as the sample 7, placing the quartz sample in a measuring instrument shown in figure 1, performing thermal expansion test by adopting a temperature rise system same as that of thermal expansion measurement, calculating the difference value between the real thermal expansion value and the test value of the quartz sample at each temperature point, and obtaining an expansion value generated by heating the ejector rod 5, the object placing column 9 and the base plate 8 as a compensation value for calibrating the test result of the instrument and eliminating system errors.
S4: the expansion compensation value and the original size of the specimen are input into a data processing system.
S5: and (3) raising the displacement sensor 2, opening the furnace door 14, placing the sample 7 on the backing plate 8 on the storage column 9, closing the furnace door 14, lowering the displacement sensor 2, standing for a plurality of minutes, and starting a temperature rise test after the readings of the displacement sensor 2 are unchanged. For high-strength and ultrahigh-strength concrete with low water gel, drying treatment is needed before thermal expansion test so as to prevent the test result from being influenced and the instrument from being damaged due to bursting of the sample in the thermal expansion test process.
S6: during the temperature rise test, the thermocouple 6 is used for measuring the temperature and transmitting the measured temperature to the temperature control part and the data processing system. The temperature control part judges whether the measured temperature meets the requirement according to a preset temperature rising system, and if not, the current intensity of the resistance wire is adjusted to enable the measured temperature to be consistent with the preset temperature.
The data processing system acquires the measured hearth temperature and the sample expansion value measured by the displacement sensor in real time, calculates the thermal expansion percentage and the thermal expansion coefficient of the sample at different temperatures according to the original size of the sample, the sample expansion value, the hearth temperature and the expansion compensation value, and can display a test curve in real time in a computer. The percentage of thermal expansion and the coefficient of thermal expansion are calculated as follows:
percent thermal expansion:
coefficient of thermal expansion:
in the formula:
t0-an initial temperature;
t1-the test temperature;
L0sample at t0Height at temperature;
L1sample at t1Temperature considerations the height of the expansion compensation value.
The first embodiment is as follows: by adopting the high-temperature thermal expansion measuring instrument and the measuring method for the concrete, the high-temperature thermal expansion of the concrete with the water-cement ratio of 0.4 and the maximum aggregate particle size of 16mm at the temperature of 30-810 ℃ is measured.
The concrete sample is a prism sample with the bottom surface side length of 50mm (more than 3 times of the maximum aggregate grain diameter of 48mm) and the height of 100 mm; the temperature rise rate of the sample is determined to be 2 ℃/min by adopting an auxiliary test, and the constant temperature time of each constant temperature point is shown in table 1; measuring an expansion compensation value by adopting a quartz standard sample with the height of 100 mm; the results of the thermal expansion percentage and the thermal expansion coefficient are shown in FIG. 2.
TABLE 1 constant temperature time at each constant temperature point
Example two: by adopting the high-temperature thermal expansion measuring instrument and the measuring method for the concrete, the high-temperature thermal expansion of 30-825 ℃ of the steel fiber ultrahigh-strength concrete with the water-cement ratio of 0.2, the maximum aggregate particle size of 5mm and the doped steel fiber length of 13mm is measured.
The concrete sample is a prism sample with the bottom surface side length of 50mm (more than 3 times of the length of the steel fiber of 39mm) and the height of 100 mm; the temperature rise rate of the sample is determined to be 2 ℃/min by adopting an auxiliary test, and the constant temperature time of each constant temperature point is shown in table 2; measuring a compensation value by adopting a quartz standard sample with the height of 100 mm; because the water-gel ratio is low, the anti-burst treatment is carried out by adopting a method of drying for 3 days at 105 ℃; the results of the thermal expansion percentage and the thermal expansion coefficient are shown in FIG. 3.
TABLE 2 thermostating time at each thermostating point
The above is only an embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions within the technical scope of the present disclosure should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
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