CN108303327B - Device and method for evaluating precast shield segment concrete steam curing critical strength - Google Patents
Device and method for evaluating precast shield segment concrete steam curing critical strength Download PDFInfo
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- CN108303327B CN108303327B CN201810138390.7A CN201810138390A CN108303327B CN 108303327 B CN108303327 B CN 108303327B CN 201810138390 A CN201810138390 A CN 201810138390A CN 108303327 B CN108303327 B CN 108303327B
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- 238000000034 method Methods 0.000 title claims description 28
- 238000001514 detection method Methods 0.000 claims abstract description 107
- 230000003068 static effect Effects 0.000 claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 claims abstract description 39
- 230000035515 penetration Effects 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 24
- 238000003825 pressing Methods 0.000 claims abstract description 17
- 230000001360 synchronised effect Effects 0.000 claims abstract description 15
- 238000002360 preparation method Methods 0.000 claims abstract description 13
- 238000010025 steaming Methods 0.000 claims abstract description 10
- 238000010923 batch production Methods 0.000 claims abstract description 5
- 239000000523 sample Substances 0.000 claims description 83
- 238000012360 testing method Methods 0.000 claims description 20
- 229910000831 Steel Inorganic materials 0.000 claims description 11
- 239000010959 steel Substances 0.000 claims description 11
- 238000005056 compaction Methods 0.000 claims description 6
- 238000002474 experimental method Methods 0.000 claims description 6
- 230000000284 resting effect Effects 0.000 claims description 6
- 230000000740 bleeding effect Effects 0.000 claims description 3
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 abstract description 3
- 238000001723 curing Methods 0.000 description 48
- 238000013461 design Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 4
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- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
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- 241001330002 Bambuseae Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 238000009435 building construction Methods 0.000 description 1
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- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000009958 sewing Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
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Abstract
The invention discloses a device for evaluating the concrete steam curing critical strength for prefabricated shield segments, which is characterized in that: the concrete mixing device comprises a detection bracket, a hydraulic jack arranged above the detection bracket and used for applying pressure, a detection barrel which is arranged below the hydraulic jack and is used for detecting concrete mixture filled in the upper surface of a bottom plate of the detection bracket, and a detection device arranged at the lower end of the hydraulic jack and used for detecting concrete penetration strength; the invention also discloses a detection method for evaluating the concrete steam curing critical strength for the prefabricated shield segment, which comprises the following steps: setting a static stop parameter, setting a synchronous point, setting the same batch production, simulating a preparation stage before entering the static stop of the concrete pipe sheet in a laboratory synchronous production field, simulating the static stop stage before entering each steam curing in the laboratory synchronous production field, and evaluating a detection result to obtain the critical strength of the concrete steam curing. The invention fills the domestic blank in the technical field of concrete steaming critical strength, and provides a new concrete strength concept.
Description
Technical Field
The invention belongs to the technical field of prefabricated shield segment building construction, and particularly relates to a device and a method for evaluating concrete steam curing critical strength for prefabricated shield segments.
Background
The prefabricated shield segments are generally used for manufacturing concrete subway tunnels, and each section of the concrete subway tunnel is formed by assembling 6 arc-shaped prefabricated shield segments, as shown in fig. 1 and 2.
In the shield segment production process, in order to shorten the period and accelerate the turnover of the mould, a steam curing method is generally adopted. The steam curing method is divided into two stages, wherein the first stage is a dead time (pre-curing time) before entering a steam curing room, and the second stage is a temperature-adjusting curing time after entering the steam curing room; the construction content of the dead time (pre-curing time) is not only the preparation work of the concrete before entering the steam curing room, the preparation work comprises the steps of casting the concrete into a model and vibrating and compacting, as shown in fig. 4 and 5, but also comprises the steps of plastering the concrete cast into a mould for a plurality of times to make the surface smooth and attractive, and then staying for a period of time, wherein the period of time after staying is called as the dead time. The residence time of the concrete in the "dead time" often determines the ability of the concrete to resist steam curing failure; the temperature-adjusting curing period is that the pipe piece enters a steam curing room, steam is led into a pipeline at the top of the steam curing room, the steam curing room is divided into a heating room area, a constant temperature room area and a cooling room area by changing steam supply quantity, the pipe piece sequentially passes through the three room areas, the heating room area gradually rises to 55 ℃ from room temperature for 1 hour, the constant temperature room area keeps unchanged at 55 ℃ for 2 hours, the cooling area is reduced to room temperature from 55 ℃ again for 1 hour (different unit constant temperature temperatures and time can be different). When the concrete enters the three room areas for steam curing, the high temperature can damage the concrete, so that the steamed duct pieces have quality defects such as cracks and the like.
The reason for causing quality defects such as cracks and the like of the segments after steam curing is that the initial structural strength of the concrete is not enough and the compactness is not enough before the concrete enters a steam curing room, namely after the rest period is finished, so that the critical strength of the concrete for steam curing (namely, how long the strength after the rest period can just resist steam curing damage) is particularly important to find out.
The prior art for measuring the concrete strength generally refers to measuring the compressive strength of concrete, the method adopted by the method is that a concrete test block is crushed by a press, and the concrete strength refers to the strength of the concrete which does not generate cracks after steam curing, and the concrete steam curing strength is measured or is blank in China at present.
Disclosure of Invention
The invention provides a method for evaluating the steam curing temporary of precast shield segments, which is used for solving the problems of insufficient initial structural strength and insufficient compactness of concrete before entering a steam curing room.
The utility model provides a device of evaluation prefabricated shield constructs section of jurisdiction with concrete steam maintenance critical strength which characterized in that: the concrete mixing device comprises a detection support, a hydraulic jack, a detection barrel and a detection device, wherein the hydraulic jack is arranged above the detection support and used for applying pressure, the detection barrel is arranged below the hydraulic jack and used for detecting concrete mixture filled in the upper surface of a bottom plate of the detection support, and the detection device is arranged at the lower end of the hydraulic jack and used for detecting concrete penetration intensity.
The detection support comprises a bottom plate, upright posts around the bottom plate, a plurality of cross bars which are positioned on the same horizontal plane at the top ends of the upright posts and are supported in a staggered manner, and annular screw sleeves for erecting the hydraulic jack are arranged between the plurality of cross bars.
The detection bracket bottom plate is a square steel plate, and the upright posts around the bottom plate are a plurality of upright posts which are respectively arranged on a group of opposite sides of the square steel plate and have the same height and are spaced at certain distance; the plurality of cross bars are arranged vertically between every two groups of cross bars along the top of the bracket from outside to inside, and each group of cross bars consists of two cross bars with equal length, which are parallel to each other and are spaced at a certain distance; two cross bars of one group of cross bars respectively form a vertical plane with one group of opposite sides of the square steel plate and the upright posts on the opposite sides; the annular threaded sleeve is arranged between a square frame formed by two groups of cross bars of the innermost layer and the middle layer and fixedly connected with a frame around the square frame.
The hydraulic jack is a hydraulic jack used in a national standard JC473-92 concrete pressure bleeding instrument, and comprises 1 jack at one end and 1 oil pump at the other end, an oil pipe is arranged between the jack and the oil pump, one end of the oil pipe is connected with a hydraulic tee joint through a quick connector, the hydraulic tee joint is respectively connected with the jack and the pressure gauge, and the other end of the oil pipe is connected with the oil pump through a quick connector; the oil pump comprises a tubular oil cylinder and a tubular compression bar; the detection device comprises a probe screw sleeve with external threads and internal threads and a probe with external threads, wherein the probe screw sleeve is connected with a jack at the upper end of the probe screw sleeve through the external threads, and is connected with a probe at the lower end of the probe screw sleeve through the internal threads; the total height of the probe is 80MM, the probe comprises an upper part and a lower part, the upper part of the probe is provided with external threads, the diameter and the height of the probe are matched with those of a probe screw sleeve, the height of the upper part of the probe is 10MM, and the diameter of the upper part of the probe is 13.5MM; the height of the lower part of the probe is 70MM, the diameter of the lower part of the probe is 40MM, the lower part of the probe is divided into a graduated zone and a non-graduated zone, the graduated zone is a probe zone which is 50MM upwards from the bottom of the probe, and each 5MM is a graduated zone.
A detection method of a device for evaluating the concrete steam curing critical strength for prefabricated shield segments is characterized by comprising the following steps: the method comprises the following steps:
step one, setting a static stop parameter: presetting a plurality of concrete steam curing static stop time periods with a certain time interval, and analyzing how long the concrete is stopped, wherein the concrete strength can just resist steam curing damage;
step two, setting a synchronization point: the synchronization points are that the static time length of each laboratory detection critical strength corresponds to or is equal to the static time length of each corresponding concrete segment produced on the production site; the synchronization point also comprises concrete and concrete mixtures of the same batch number adopted by a laboratory and a production site;
step three, setting the same batch production: the production process comprises a preparation stage before static stop, a static stop stage and a steam curing stage;
step four, a laboratory synchronous production site is simulated to enter a preparation stage before the static stop of the concrete pipe sheet;
step five, a laboratory synchronous production site is simulated to enter a static stop stage before each steam curing, detection cylinders corresponding to different static stop time lengths are respectively adopted, and the penetration strength of the detection cylinders is detected by the same method;
step six, evaluating the detection result to obtain the concrete steam curing critical strength;
presetting a plurality of static stopping time periods with certain time intervals, wherein the time intervals of different static stopping time periods are generally 20 minutes or 30 minutes;
the laboratory synchronous production field of the fourth step simulates a preparation stage before entering a concrete pipe sheet to stop, and the concrete process comprises the following steps:
setting the number of detection cylinders corresponding to each type of static time length of concrete segments as 3;
secondly, filling the concrete mixture of the concrete segments corresponding to each type of static stop time with 3 detection barrels respectively, and vibrating and compacting the concrete mixture in the 3 detection barrels simultaneously;
and thirdly, enabling the concrete mixture after compaction to enter respective static stop stages.
The fifth step is to detect the penetration strength by the same method, and the specific process is as follows:
the method comprises the steps that in the static stop time period of a synchronous production site of a laboratory, concrete which corresponds to different static stop time periods and is subjected to compaction by vibration enters respective static stop time periods;
sequentially placing 3 concrete detection cylinders which finish the current static stop time on a detection support bottom plate;
screwing a check valve of the hydraulic jack before the jack probe penetrates into the concrete;
fourthly, repeatedly pressing a hydraulic jack pressing rod to enable a probe of the jack to extend downwards and be flush with the surface of concrete in the detection barrel on the bottom plate of the bracket;
repeatedly pressing the jack pressing rod again until the probe penetrates into the concrete for 20mm;
the reading of the pressure gauge is recorded, the accuracy is 0.5MPa, and the concrete penetration strength of the detection barrel corresponding to the static stopping time length is recorded.
Repeating the step until the concrete strength of the 3 concrete detection barrels with the current rest time is detected;
and sequentially selecting 3 concrete detection cylinders for finishing the next rest time period, and repeating the steps. And step six, evaluating the detection result to obtain the concrete steam curing critical strength, wherein the concrete steam curing critical strength is specifically as follows:
taking an average value of penetration intensities detected by 3 detection barrels corresponding to each static stop duration as the penetration intensity of each test;
secondly, when the difference between one of the maximum value or the minimum value of the penetration intensities of the 3 detection barrels and the intermediate value exceeds 10% of the intermediate value, the intermediate value is used as the penetration intensity of each test;
thirdly, when the maximum value and the minimum value are both 10% higher than the intermediate value, the experiment should be carried out again;
fourthly, comparing penetration strength corresponding to different resting time periods with critical points at which cracks do not appear on the outer cambered surface of the tube piece after steaming on the production site corresponding to different resting time periods to obtain steaming critical strength; the critical point without cracks is a pressure gauge strength value corresponding to the dead time when the outer cambered surface of the tube piece is not cracked after steaming, and the pressure gauge strength unit is megapascals.
Advantageous effects of the invention
1. The invention fills the domestic blank in the technical field of concrete steam curing critical strength, and provides a new concrete strength concept, namely a concrete steam curing critical strength concept aiming at easy crack generation after concrete steam curing. The method solves the technical problem that the original structural strength of the concrete pipe piece is not large enough and the compactness is not large enough for a long time, so that cracks are generated after the concrete pipe piece is steamed and cured, and the steam curing critical strength of the concrete pipe piece is accurately evaluated by adopting the device and the method for testing the steam curing critical strength of the prefabricated shield pipe piece.
2. The invention adopts a method of combining laboratory test and production field test: the laboratory is responsible for measuring the strength of each static stop stage of the concrete, and the production site is responsible for providing the judgment basis of the critical strength of the steamed concrete, and the production process is skillfully borrowed, so that the production process is the product production service and is also the test service, the purpose of one stone and two birds is achieved, meanwhile, the experimental steps of experiments in the laboratory are reduced, and the detection period of the laboratory is shortened.
3. The invention provides a device for testing the critical strength of concrete steam curing, which is used for detecting the special design on a support structure, so that the detection effect is not influenced by upward or downward deformation of the pressure when the detection support is subjected to the pressure with certain strength; the pressure gauge is convenient for reading pressure by the special design of the structure of the detection probe.
Drawings
FIG. 1 is a graph of the application effect of a prefabricated shield segment;
FIG. 2 is a diagram showing the appearance and effect of prefabricated shield segments;
FIG. 3 is a schematic view of a prefabricated shield segment making mold;
FIG. 4 is a perspective view of the detection device of the present invention;
FIG. 5 is a perspective view of a test rack of the present invention;
FIG. 6 is a perspective view of a hydraulic jack;
FIG. 7 is a top dimensional view of a test rack of the present invention;
FIG. 8 is a front view of a test rack of the present invention;
FIG. 9 is a left side view of the test stand of the present invention;
FIG. 10 is a front view and top view of a test rack ring nut;
FIG. 11 is a perspective view and a front dimensional view of a probe according to the present invention;
FIG. 12 is a perspective view of a probe insert of the present invention;
FIG. 13 is a front dimensional view of a probe insert of the present invention;
in the figure, 1: detecting a bracket; 1-1: detecting a bracket bottom plate; 1-2: detecting a support stand column; 1-3-1: a set of crossbars; 1-3-2: two groups of cross bars; 1-3-3: three groups of cross bars; 1-4: an annular screw sleeve; 2: a hydraulic jack; 2-1: a jack; 2-2: a tee joint; 2-3: a quick connector; 2-4: passing through an oil pipe; 2-5-1: an oil pump pressing rod; 2-5-2: an oil drum; 3: a detection cylinder; 4. and a detection device.
Detailed Description
The summary is further explained below with reference to the drawings:
the design principle of the invention is as follows:
1. design principle of the detection device: the detection device has two very important points in design, firstly, the detection bracket is not deformed under the condition that the jack acts on the concrete to generate enough strength, and the non-deformation means that the top and the bottom of the detection bracket are not arched upwards or sunken downwards due to strong pressure; secondly, when the concrete probe is inserted into the concrete, the pressure gauge can generate the required reading. For the first design key point, the invention adopts a steel plate with the thickness of 12MM for the bottom plate of the detection bracket, and the detection bracket is made of steel materials. In order to prevent the top of the support from arching, two sides of the support are respectively provided with an upright post, and the traditional four upright posts are improved into six upright posts. For the second design key point, the diameter of the probe is designed to be 40MM, which is data obtained through repeated experiments, the probe is too thin, for example, a sewing needle is exaggeratedly inserted into concrete, and the reading of the pressure gauge cannot be changed due to the fact that the resistance of the pressure gauge through the insertion of the concrete is too small; in contrast, if the probe is too thick, for example, if a probe of a large diameter of a washbasin is placed in the concrete, the probe is too thick to be inserted into the concrete because of the high resistance, and at this time the manometer is also inconvenient to produce a pressure reading, so the thickness of the probe is critical to the test pressure.
2. The design principle of the detection method is as follows:
A. certain external conditions are required to produce the critical strength of concrete. The external condition is that the probe is made to be resistant by inserting the probe into the concrete, so that the pressure gauge to which the probe is connected produces a reading of the pressure intensity.
B. The laboratory and the production site are synchronous, namely, a batch of concrete mixture is adopted and the same static stop time is adopted.
C. Since the probe is inserted into the concrete to damage the concrete structure, the damaged concrete itself has cracks, so the damaged concrete cannot be sent to a steam curing room for testing whether cracks exist on the surface after curing.
Based on the design principle, the invention provides a device for evaluating the concrete steam curing critical strength for prefabricated shield segments.
As shown in fig. 4, a device for evaluating the concrete steam curing critical strength for prefabricated shield segments is characterized in that: the concrete mix filling device comprises a detection support 1, a hydraulic jack 2 which is arranged above the detection support and used for applying pressure, a detection barrel 3 which is arranged below the hydraulic jack and used for detecting concrete mix filled in the upper surface of a bottom plate of the detection support, and a detection device 4 which is arranged at the lower end of the hydraulic jack and used for detecting concrete penetration intensity.
As shown in fig. 5, the detection bracket comprises a bottom plate 1-1, upright posts 1-2 around the bottom plate, a plurality of cross bars (1-3-1, 1-3-2, 1-3-3) which are positioned on the same horizontal plane at the top ends of the upright posts and are supported in a staggered manner, and an annular screw sleeve 1-4 for erecting a hydraulic jack is arranged among the plurality of cross bars (1-3-1, 1-3-2, 1-3-3).
As shown in fig. 5, the bottom plate of the detection bracket is a square steel plate, and the upright posts around the bottom plate are a plurality of upright posts 1-2 which are respectively arranged on a group of opposite sides of the square steel plate and have the same height and are spaced at a certain distance; the plurality of cross bars are arranged vertically between every two groups of cross bars, and each group of cross bars consists of two cross bars with equal length, which are parallel to each other and are spaced at a certain distance; two cross bars of one group of cross bars respectively form a vertical plane with one group of opposite sides of the square steel plate and the upright posts on the opposite sides; the annular threaded sleeve 1-4 is arranged in the middle of a square frame formed by two groups of transverse rods of the innermost layer and the middle layer and fixedly connected with a frame around the square frame.
As shown in fig. 6, the hydraulic jack is a hydraulic jack used in a national standard JC473-92 concrete pressure bleeding machine, and comprises 1 jack 2-1 at one end and 1 oil pump (2-5-1, 2-5-2) at the other end, wherein an oil pipe 2-4 is arranged between the jack 2-1 and the oil pump (2-5-1, 2-5-2), one end of the oil pipe 2-4 is connected with a hydraulic tee joint through a quick connector 2-3, the hydraulic tee joint is respectively connected with the jack 2-1 and a pressure gauge 2-6, and the other end of the oil pipe 2-4 is connected with the oil pump through the quick connector 2-3; the oil pump comprises a tubular oil cylinder 2-5-2 and a tubular compression bar 2-5-1; as shown in fig. 11, 12 and 13, the detecting device 4 comprises a probe screw sleeve 4-1 with external threads and internal threads and a probe 4-2 with external threads, wherein the probe screw sleeve 4-1 is connected with a jack 2-1 at the upper end of the probe screw sleeve through the external threads, and the probe 4-2 is connected with the lower end of the probe screw sleeve through the internal threads; the total height of the probe 4-2 is 80MM, the probe comprises an upper part and a lower part, the upper part of the probe is provided with external threads, the diameter and the height of the probe are matched with those of a probe screw sleeve, the height of the upper part of the probe is 10MM, and the diameter of the upper part of the probe is 13.5MM; the height of the lower part of the probe is 70MM, the diameter of the lower part of the probe is 40MM, the lower part of the probe is divided into a graduated zone and a non-graduated zone, the graduated zone is a probe zone which is 50MM upwards from the bottom of the probe, and each 5MM is a graduated zone.
A detection method of a device for evaluating the concrete steam curing critical strength for prefabricated shield segments is characterized by comprising the following steps: the method comprises the following steps:
step one, setting a static stop parameter: presetting a plurality of concrete steam curing static stop time periods with a certain time interval, and analyzing how long the concrete is stopped, wherein the concrete strength can just resist steam curing damage;
presetting a plurality of static stopping time periods with certain time intervals, wherein the time intervals of different static stopping time periods are generally 20 minutes or 30 minutes;
supplementary explanation: the concrete rest time length in the common production is set to be 2.5 hours, and different rest time lengths are generally set to be 20 minutes to half an hour at intervals, which is determined according to the speed of the hydration reaction of the concrete, and the embodiment can assume that 3 rest times are set to be 2.5 hours, 3 hours and 3.5 hours respectively;
step two, setting a synchronization point: the synchronization points are that the static time length of each laboratory detection critical strength corresponds to or is equal to the static time length of each corresponding concrete segment produced on the production site; the synchronization point also comprises concrete and concrete mixtures of the same batch number adopted by a laboratory and a production site;
step three, setting the same batch production: the production process comprises a preparation stage before static stop, a static stop stage and a steam curing stage;
supplementary explanation: the invention sets the same batch production, in order to macroscopically detect different static time length, the detection period of two adjacent time length in the first, second and third static time length is only half an hour different, and the detection period is greatly shortened compared with the static time length adopting serial operation.
Step four, a laboratory synchronous production site is simulated to enter a preparation stage before the static stop of the concrete pipe sheet;
the specific process is as follows:
setting the number of detection cylinders corresponding to each type of static time length of concrete segments as 3;
supplementary explanation: here, 3 test cartridges are provided to find the average value to reduce the error.
Secondly, filling the concrete mixture of the concrete segments corresponding to each type of static stop time with 3 detection barrels respectively, and vibrating and compacting the concrete mixture in the 3 detection barrels simultaneously;
supplementary explanation: the preparation stage before static stop in the actual concrete pipe sheet production comprises the steps of freshly mixing concrete, placing concrete mixture into a mould (shown as a mould in figure 3), vibrating the concrete after being placed into the mould to compact and plastering for a plurality of times so as to lead the surface to be smooth and beautiful; the preparation stage before the static stop in the experiment of the invention comprises the following steps: firstly, put into the concrete mixture that uses in the production and detect the section of thick bamboo in the correspondence, and secondly, vibrate closely knit the concrete of every detection barrel, two steps are the same with the production scene in the front, and need this link in laboratory to the multiple plastering of production scene, because the concrete of test barrel is only used for inserting the probe, does not have pleasing to the eye demand.
And thirdly, enabling the concrete mixture after compaction to enter respective static stop stages.
Supplementary explanation: assuming that three static stopping time periods are set, 3 detection barrels are needed for each time period, 9 detection barrels are needed after compacting by vibration at the moment, concrete in the 9 barrels is compacted by vibration at the same time, and then static stopping stages are respectively carried out according to 2.5 hours, 3 hours and 3.5 hours.
Step five, a laboratory synchronous production site is simulated to enter a static stop stage before each steam curing, detection cylinders corresponding to different static stop time lengths are respectively adopted, and the penetration strength of the detection cylinders is detected by the same method;
the specific process of the fifth step is as follows:
the method comprises the steps that in the static stop time period of a synchronous production site of a laboratory, concrete which corresponds to different static stop time periods and is subjected to compaction by vibration enters respective static stop time periods;
sequentially placing 3 concrete detection cylinders which finish the current static stop time on a detection support bottom plate;
screwing a check valve of the hydraulic jack before the jack probe penetrates into the concrete;
fourthly, repeatedly pressing a hydraulic jack pressing rod to enable a probe of the jack to extend downwards and be flush with the surface of concrete in the detection barrel on the bottom plate of the bracket;
supplementary explanation: as shown in FIG. 4, under the static condition, the distance from the probe of the hydraulic jack to the detection barrel is about 3-4 cm, the limit of the up-down extension of the jack is 10 cm, and if the upper opening of the detection barrel is too far from the bottom of the probe of the jack, the probe cannot be penetrated into the barrel by 20MM, so the initial distance from the lower end part of the probe of the jack to the upper opening of the detection barrel should be between 3-4 cm.
Repeatedly pressing the jack pressing rod again until the probe penetrates into the concrete for 20mm;
the reading of the pressure gauge is recorded, the accuracy is 0.5MPa, and the concrete penetration strength of the detection barrel corresponding to the static stopping time length is recorded.
Repeating the step until the concrete strength of the 3 concrete detection barrels with the current rest time is detected;
and sequentially selecting 3 concrete detection cylinders for finishing the next rest time period, and repeating the steps.
Step six, evaluating the detection result to obtain the concrete steam curing critical strength;
the sixth step is as follows:
taking an average value of penetration intensities detected by 3 detection barrels corresponding to each static stop duration as the penetration intensity of each test;
secondly, when the difference between one of the maximum value or the minimum value of the penetration intensities of the 3 detection barrels and the intermediate value exceeds 10% of the intermediate value, the intermediate value is used as the penetration intensity of each test;
thirdly, when the maximum value and the minimum value are both 10% higher than the intermediate value, the experiment should be carried out again;
fourthly, comparing penetration strength corresponding to different resting time periods with critical points at which cracks do not appear on the outer cambered surface of the tube piece after steaming on the production site corresponding to different resting time periods to obtain steaming critical strength; the critical point without cracks is a pressure gauge strength value of a dead time period corresponding to the condition that the outer cambered surface of the tube piece is not cracked after steaming, and the pressure gauge strength unit is megapascals.
Supplementary explanation: the rest time corresponding to one strength value may be different due to different slumps of the concrete mixture, so the rest time cannot be used as the basis for measuring the critical strength, for example, the appearance of the corresponding segment has no crack when the rest time is 2.5 hours, the strength value of the pressure gauge is measured to be 10 megapascals, but the next production is that the slumps of the concrete mixture are different from the last time, even if the concrete mixture is 2.5 hours, the strength value of the concrete mixture still does not reach 10 megapascals, and the strength value of the pressure gauge can reach 10 megapascals after more than half an hour, so the basis for measuring the critical strength value for the second time is 10 megapascals instead of 2.5 hours.
It should be emphasized that the embodiments described herein are illustrative rather than limiting and that this invention encompasses embodiments not limited to the specific implementations.
Claims (4)
1. A detection method of a device for evaluating the critical strength of concrete steam curing for prefabricated shield segments,
the detection method is based on a device for evaluating the concrete steam curing critical strength for the prefabricated shield segment, and the device comprises a detection bracket, a hydraulic jack arranged above the detection bracket and used for applying pressure, a detection barrel which is arranged below the hydraulic jack and is used for loading concrete mixture on the upper surface of a detection bracket bottom plate, and a detection device arranged at the lower end of the hydraulic jack and used for detecting the concrete penetration strength;
the detection support comprises a bottom plate, upright posts around the bottom plate, a plurality of cross bars which are positioned on the same horizontal plane at the top ends of the upright posts and are supported in a staggered manner, and annular screw sleeves for erecting the hydraulic jack are arranged between the cross bars;
the detection bracket bottom plate is a square steel plate, and the upright posts around the bottom plate are a plurality of upright posts which are respectively arranged on a group of opposite sides of the square steel plate and have the same height and are spaced at certain distance; the plurality of cross bars are respectively arranged in a first cross bar group, a second cross bar group and a third cross bar group from outside to inside along the top of the bracket, the first cross bar group and the second cross bar group are mutually vertical, the second cross bar group and the third cross bar group are mutually vertical, and each group of cross bars consists of two cross bars which are equal in length and are mutually parallel and are spaced at a certain distance; two cross bars of one group of cross bars respectively form a vertical plane with one group of opposite sides of the square steel plate and the upright posts on the opposite sides; the annular threaded sleeve is arranged between a square frame formed by two groups of cross bars of the innermost layer and the middle layer and fixedly connected with a frame around the square frame;
the hydraulic jack is a hydraulic jack used in a national standard JC473-92 concrete pressure bleeding instrument, and comprises 1 jack at one end and 1 oil pump at the other end, an oil pipe is arranged between the jack and the oil pump, one end of the oil pipe is connected with a hydraulic tee joint through a quick connector, the hydraulic tee joint is respectively connected with the jack and the pressure gauge, and the other end of the oil pipe is connected with the oil pump through a quick connector; the oil pump comprises a tubular oil cylinder and a tubular compression bar; the detection device comprises a probe screw sleeve with external threads and internal threads and a probe with external threads, wherein the probe screw sleeve is connected with a jack at the upper end of the probe screw sleeve through the external threads, and is connected with a probe at the lower end of the probe screw sleeve through the internal threads; the total height of the probe is 80MM, the probe comprises an upper part and a lower part, the upper part of the probe is provided with external threads, the diameter and the height of the probe are matched with those of a probe screw sleeve, the height of the upper part of the probe is 10MM, and the diameter of the upper part of the probe is 13.5MM; the height of the lower part of the probe is 70MM, the diameter of the lower part of the probe is 40MM, the lower part of the probe is divided into a graduated zone and a non-graduated zone, the graduated zone is a probe zone which is 50MM upwards from the bottom of the probe, and each 5MM is a graduated zone;
the method is characterized in that: the method comprises the following steps:
step one, setting a static stop parameter: presetting a plurality of concrete steam curing static stop time periods with a certain time interval, and analyzing how long the concrete is stopped, wherein the concrete strength can just resist steam curing damage;
step two, setting a synchronization point: the synchronization points are that the static time length of each laboratory detection critical strength corresponds to or is equal to the static time length of each corresponding concrete segment produced on the production site; the synchronization point also comprises concrete and concrete mixtures of the same batch number adopted by a laboratory and a production site;
step three, setting the same batch production: the production process comprises a preparation stage before static stop, a static stop stage and a steam curing stage;
step four, a laboratory synchronous production site is simulated to enter a preparation stage before the static stop of the concrete pipe sheet;
step five, a laboratory synchronous production site is simulated to enter a static stop stage before each steam curing, detection barrels corresponding to different static stop time lengths are respectively adopted, and the penetration strength of the detection barrels is detected by the same method;
step six, evaluating the detection result to obtain the concrete steam curing critical strength;
the method comprises the following steps:
taking an average value of penetration intensities detected by 3 detection barrels corresponding to each static stop duration as the penetration intensity of each test;
secondly, when the difference between one of the maximum value or the minimum value of the penetration intensities of the 3 detection barrels and the intermediate value exceeds 10% of the intermediate value, the intermediate value is used as the penetration intensity of each test;
thirdly, when the maximum value and the minimum value are both 10% higher than the intermediate value, the experiment should be carried out again;
fourthly, comparing penetration strength corresponding to different resting time periods with critical points at which cracks do not appear on the outer cambered surface of the tube piece after steaming on the production site corresponding to different resting time periods to obtain steaming critical strength; the critical point without cracks is a pressure gauge strength value corresponding to the dead time when the outer cambered surface of the tube piece is not cracked after steaming, and the pressure gauge strength unit is megapascals.
2. The detection method of the device for evaluating the concrete steam curing critical strength for the prefabricated shield segments, which is disclosed in claim 1, is characterized by comprising the following steps: the first step is to preset a plurality of rest time periods with certain time intervals, and generally takes 20 minutes or 30 minutes as the time intervals of different rest time periods.
3. The detection method of the device for evaluating the concrete steam curing critical strength for the prefabricated shield segments, which is disclosed in claim 1, is characterized by comprising the following steps: the laboratory synchronous production field of the fourth step simulates a preparation stage before entering a concrete pipe sheet to stop, and the concrete process comprises the following steps:
setting the number of detection barrels corresponding to each type of static stop time length of concrete segments as 3;
secondly, filling the concrete mixture of the concrete segments corresponding to each type of static stop time with 3 detection barrels respectively, and vibrating and compacting the concrete mixture in the 3 detection barrels simultaneously;
and thirdly, enabling the concrete mixture after compaction to enter respective static stop stages.
4. The detection method of the device for evaluating the concrete steam curing critical strength for the prefabricated shield segments, which is disclosed in claim 1, is characterized by comprising the following steps: the fifth step is to detect the penetration strength by the same method,
the specific process is as follows:
the method comprises the steps that in the static stop time period of a synchronous production site of a laboratory, concrete which corresponds to different static stop time periods and is subjected to compaction by vibration enters respective static stop time periods;
sequentially placing 3 concrete detection barrels which finish the current static stop time on a detection support bottom plate;
screwing a check valve of the hydraulic jack before the jack probe penetrates into the concrete;
fourthly, repeatedly pressing a hydraulic jack pressing rod to enable a probe of the jack to extend downwards and be flush with the surface of concrete in the detection barrel on the bottom plate of the bracket;
repeatedly pressing the jack pressing rod again until the probe penetrates into the concrete for 20mm;
recording the reading of the pressure gauge until the accuracy reaches 0.5MPa, and recording the reading as the concrete penetration strength of the detection barrel corresponding to the static stopping time;
repeating the step until the concrete strength of the 3 concrete detection barrels with the current rest time is detected;
and sequentially selecting 3 concrete detection barrels for finishing the next rest time period, and repeating the steps.
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| CN109100213B (en) * | 2018-09-17 | 2020-12-04 | 广东华坤建设集团有限公司 | Concrete strength detection device of assembled stair |
| CN110361262A (en) * | 2019-06-28 | 2019-10-22 | 广东建准检测技术有限公司 | It is a kind of based on the concrete of identification technology from dynamic compression strength detection system |
| CN110483098A (en) * | 2019-09-27 | 2019-11-22 | 中铁十六局集团北京轨道交通工程建设有限公司 | A kind of method of type concrete steam maintenance in subway work |
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