FI20205958A1 - A method and apparatus for monitoring the continuous drying of concrete - Google Patents
A method and apparatus for monitoring the continuous drying of concrete Download PDFInfo
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- FI20205958A1 FI20205958A1 FI20205958A FI20205958A FI20205958A1 FI 20205958 A1 FI20205958 A1 FI 20205958A1 FI 20205958 A FI20205958 A FI 20205958A FI 20205958 A FI20205958 A FI 20205958A FI 20205958 A1 FI20205958 A1 FI 20205958A1
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- humidity
- concrete
- humidity sensor
- measuring
- sensor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/38—Concrete; ceramics; glass; bricks
- G01N33/383—Concrete, cement
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
Abstract
According to an example aspect of the present invention, there is provided a method for measuring humidity of concrete (4) comprising the following steps: measuring periodically the humidity and temperature by a first, long term humidity sensor (5) inside the concrete such that the first humidity sensor (5) is positioned inside a ventilated measurement cavity (16) inside the concrete (4) and the ventilation is performed by a ventilation channel (3), heating the first humidity sensor (5) periodically between the measurements, measuring the humidity and temperature of the concrete (4) by a second humidity sensor (12) positioned in an unventilated measurement cavity (20) inside the concrete (4), measuring the humidity and temperature of the outside space of the concrete (4) by a third humidity sensor (13), adjusting the humidity value measured by the first humidity sensor (5) by the information of the second (12) and third humidity sensors (13), and calibrating the first humidity sensor (5) between the measurements with a second (12) and third humidity sensors (13) positioned in the same space with the first humidity sensor (12).
Description
A method and apparatus for monitoring the continuous drying of concrete
[0001] The invention relates to monitoring the continuous drying of concrete.
[0002] Concrete drying has traditionally been measured by drilling a hole in the concrete and measuring the relative humidity of the air in the hole. During the test, the hole 1s blocked so that the damp air in the hole cannot be exchanged with the outside air, and also so that the concrete at the bottom of the hole cannot dry through the gap between the hole and the sleeve inserted into the hole. The measurement takes an hour and there are claims that the measurement period should be longer than this in order to obtain the correct result. One of these standard measurements is described in web page: https://www.slideshare.net/Wagner-Meters/rapid-rh-astm-f2170-steps
[0003] In practice, it has also been found that sensors may not last, especially if used to measure very wet concrete. This is most likely due to the fact that the concrete is very alkaline. Humidity sensors are typically made of polymer (metal oxides are also used) that can be damaged when exposed to an alkaline environment. It is also well known that — metals such as aluminum are etched in a basic solution. Whatever the reason, the sensor o manufacturers put a filter in front of the sensor, which in some cases is a porous metal
N S film. The filter, which effectively prevents dust, impurities and alkaline water droplets O from entering the sensor surface, also makes the sensor extremely slow. 9 [0004] In practice, it has been found that the sensor cannot be left in the hole and the
I i 25 — results can be monitored remotely. Measurements made in this way have shown that the S sensor gives a higher humidity reading than is actually the case. There are two obvious
O S reasons for this. First, the humidity sensors own hysteresis and thus the result is always at the upper limit of the hysteresis, since the concrete moisture decreases with time. Another reason is that the concrete dries at the bottom of the hole more slowly than the point at the — same depth of concrete elsewhere. This is because the sensor and its sealing prevents the concrete from drying out. The hole also naturally drifts under overpressure. Due to these problems, the drying of the concrete is not monitored continuously. For this reason, accurate prediction on the date when the construction work can be continued cannot be made. This also prevents the concrete from being optimized for drying, for example by heating and ventilating the space, while taking into account the current price of electricity. In other words, in practice, the drying of concrete is monitored by visiting the site several times. In addition, sensors need to be calibrated regularly to ensure the results are reliable.
[0005] Some of the known solutions for measuring humidity of concrete are described in W0200223158, where no cavity in concrete is formed and in FI-108891, in — which a sealed measurement cavity inside concrete is used.
[0006] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
— [0007] According to a first aspect of the present invention, there is provided method and apparatus for measuring humidity of concrete comprising the following steps: measuring periodically the humidity and temperature by a first, long term humidity sensor inside the concrete such that the first humidity sensor is positioned inside a ventilated measurement cavity inside the concrete and the ventilation is performed by a ventilation — channel, heating the first humidity sensor periodically between the measurements, measuring the humidity and temperature of the concrete by a second humidity sensor > positioned in an unventilated measurement cavity inside the concrete, measuring the N humidity and temperature of the outside space of the concrete by a third humidity sensor, 2 adjusting the humidity value measured by the first humidity sensor by the information of o 25 — the second and third humidity sensors, calibrating the first humidity sensor between the E measurements with a second and third humidity sensors positioned in the same space with o the first humidity sensor.
D N [0008] According to a second aspect of the present invention, there is provided N method and apparatus for measuring humidity of concrete such that the heating of the first — humidity sensor is done 2-3 times in 24 hours and the humidity and temperature is measured both before and after these heatings.
[0009] According to a third aspect of the present invention, there is provided a method for measuring humidity of concrete such that the heating of the first humidity sensor is done in 1-3 hours intervals and the concrete is heated during this time with — external heaters.
[0010] According to a fourth aspect of the present invention, there is provided a method and apparatus for measuring humidity of concrete such that the heating of the first humidity sensor is done for 30 seconds - some minutes.
[0011] According to a fifth aspect of the present invention, there is provided a method and apparatus for measuring humidity of concrete such that the heating of the first humidity sensor is done such that the temperature rises during the heating around 1-5 degrees.
[0012] According to a sixth aspect of the present invention, there is provided a method and apparatus such that the first humidity sensor has more tight filter than the second humidity sensor.
— [0013] According to a seventh aspect of the present invention, there is provided a method and apparatus such that the ventilation channel typically has an inner diameter in the range of 0.5-1 mm and the length of the channel is in the range of 5- 25 cm.
o BRIEF DESCRIPTION OF THE DRAWINGS O 25 — [0014] FIGURE la illustrates a sensor intended for long-term monitoring in O accordance with at least some embodiments of the present invention; O [0015] FIGURE 1b illustrates a sensor intended for short-term monitoring in E accordance with prior art; co 3 [0016] FIGURE 2 illustrates schematically a view of the carrying case in accordance N 30 — with the invention;
[0017] FIGURE 3 illustrates graphically the humidity results measured in the same site using all three sensors in accordance with the invention, and
[0018] FIGURE 4 illustrates a description of the entire system in accordance with the invention.
[0019] The present invention provides a method for measuring concrete humidity in real time and in such a way that the measurement results are reliable and can predict a day when the concrete is sufficiently dry to continue the construction process. In addition, the solution enables to optimize drying process e.g., heating the place.
[0020] The measuring device consists of at least two humidity sensors 5, 12 at the end of the cable and a central unit 7, which also contains both a humidity sensor 12 and a — temperature sensor. Figure 2 is a schematic view of the carrying case 2 including a sensor 5 for long-term drying monitoring (LT sensor) and a sensor 12 for ordinary short-term moisture measurement (ST sensor) and a battery operated central unit 7 (CU) including humidity and temperature sensor 13, electronics, wireless radio 11 and one or more outputs for controlling heaters 14.
— [0021] LT Sensor intended for long-term monitoring is illustrated in Fig. 1. Essential to this sensor is that the sensor 5 is protected by a powerful metal filter, it has a thin and long breathing tube 3, and it includes a heater enabling to warming up the sensor head. The idea of the breathing tube 3 is to simulate a situation where the concrete would freely dry into the room air. All the data is taken so that the first both temperature and Rh is measured and the sensor head 5 is somewhat heated. After the heating the measurements are freguently made until the value are stabilized. The purpose of the process is to eliminate the hysteresis of the humidity sensor. Heating is typically made 2-3 times in 24 hours and N the humidity and temperature is measured both before and after these heatings. Heating 3 takes about from 30 seconds - some minutes and the temperature rises during the heating 7 25 around 1-5 degrees and the used heating power is typically 20-200 mW. The heating 2 interval may be decreased if the heaters 14 above the concrete are used. Then the interval N of heatings may be only some hours, like 1-3 hours.
O LQ [0022] ST sensor 13 is almost identical to LT sensor 12, but has no breathing hole 3 O and the filter is not as tight as in LT sensor. As LT sensor 12 may have a rather tight — porousfilter, LT typically has a well breathing metal or plastic filter. The long term sensor 12 is used to measure moisture of the concrete according to the invention. Measurements are made for example every minute and the central unit indicates, for example, with an audible signal that the measurement results have been stabilized. The measurement interval may vary in the range of from 30 seconds to 10 minutes, for example.
[0023] When using sensors, the carrying case 6 has a larger hole, so the humidity 5 and temperature inside the carrying case 6 are very close to the humidity level in the room. In other words, the humidity and temperature of the room where the concrete is located are always monitored during the measurements. After the measurements, the sensors 5, 12, 13 are attached to a transport box, whereby the carrying case 6 forms a relatively tight closed space. As a result, all three sensors 5, 12, 13 detect the same temperature and humidity, allowing the sensor results to be compared against each other. At the same time, information is obtained about the time constant of the LT sensor. Based on this information, possible clogging of the filter can be determined. Even if the sensor system is not in use, the measurement results of the sensors are transferred to the cloud at least once a day, for example. This ensures that users are constantly aware that the batteries of the CU are full and that the sensors are working properly. Figure 3 two shows the humidity results measured in the same site using all three sensors 5, 12, and 13. The results obtained from LT 5 and ST 12 sensors differ from each other markedly due to the different filters and breathing tube 3 used in LT sensor. In this experiment, the breathing tube 3 is somewhat too wide, but it predicted the time of dehydration (e.g., 70%) significantly better than the ST sensor 12. It is completely impossible to simulate the drying of the sensor cavity with the help of a breathing hole completely correctly. Because we also constantly measure the humidity and temperature of the room, as well as the correct humidity level of the concrete after each measurement S event, we can refine the forecast repeatedly. In Figure 3, the red curve 21 depicts the O 25 corrected humidity curve, which is used to predict the time when the concrete is dry = enough. The curve 20 in figure 3 depicts measurement with breathing tube and curve 22 I the measurement without breathing tube. a Q A description of the entire system is shown in Figure 4. Each time before each 3 measurement, the employee fills in the basic data on a mobile phone or tablet and takes a O 30 picture of the central unit 7, whereby the service automatically links the user, customer (location) and sensor unit. The worker then drills a hole in the concrete and installs an LT sensor 5 in that hole. It is also possible that, for sure, a hole will also be drilled for the ST sensor 12 and the current moisture content of the concrete will be ensured using an official procedure. After installation, the system remains to monitor the drying of the concrete 4 and cloud service 15 starts to predict the date when the moisture level reaches the setup value. Dryers/heaters 14 can also be connected to the room to speed up the drying of the — concrete 4. The dryers/heaters 14 can be controlled either from the central unit 7 or directly via the cloud service using a separate wireless switch. Heaters/dryers/ 14 and ventilation can speed up the drying of concrete 4, but the process costs money. If a contractor gives information to the cloudy service how much they could potentially save, if they can start work on the site then and then, the company carrying out the measurements can offer drainage optimization as a service. In the tested prototype the ventilation channel 3 is formed by a tube having inner diameter
0.7 mm and the length of the tube is 20 cm. Typically, the inner diameter of the tube may vary in the range of 0.5-1 mm and the length of the tube in the range of 5- 25 cm. In accordance with the invention the dimensions if the ventilation channel 3 are not very — critical, because the method adaptively estimates the time when the concrete is dry enough for further processes and the method can be made accurate enough for these purposes by adaptation and calibration measurements with wide range of ventilation channel dimensions. The ventilation channel 3 makes it possible that the measurement cavity 16 follows the — ambient pressure and therefore the measurements at different times are equal. In addition the heating between the measurements makes it possible to take into consideration the hysteresis of the of the sensor and surrounding structures. Measuring the ambient humidity and temperature makes it possible to correct the nonlinearity and results such that the S estimation of the target time for desired humidity and temperature (=relative humidity at O 25 — given temperature) is more accurate. In addition, measuring the humidity in the beginning = and in the end of the measurement period with a standard measurement (e.g. the standard I described in https://www.slideshare.net/Wagner-Meters/rapid-rh-astm-f2170-steps) gives N more information to adapt the parameters of the estimation algorithm.
O O As a practical matter, with present cost structure it might be advantageous that the sensor 5 O 30 is simply replaced instead of calibration if the measurement results are not accurate enough.
[0024] DEFINITIONS
[0025] In the present context, the term “LT sensor” comprises both humidity and temperature sensors and the filter used is tight, typically porous in order to protect the sensor more efficiently.
[0026] In the present context, the term “ST sensor” also comprises both humidity and temperature sensors and the filter used is more breathing in order to obtain shorter time constant than the LT sensor.
[0027] The terms first humidity sensor and second humidity sensor in the present context mean sensors including both humidity and temperature sensors.
[0028] In the present context, periodical heating means heating of the LT sensor typically every 8-12 hours, and during external heating every 1-5 hours
[0029] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
[0030] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same N embodiment. & O [0031] As used herein, a plurality of items, structural elements, compositional = elements, and/or materials may be presented in a common list for convenience. However, z 25 — these lists should be construed as though each member of the list is individually identified N as a separate and unigue member. Thus, no individual member of such list should be 3 construed as a de facto equivalent of any other member of the same list solely based on N their presentation in a common group without indications to the contrary. In addition, N various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
[0032] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or — described in detail to avoid obscuring aspects of the invention.
[0033] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the — principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.
[0034] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor reguire the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.
O O [0035] The invention is industrially applicable.
O I 25 LT Long term a O ST Short term
N 1 PVC Pipe 2 Epoxy
3 Breathing/ventilation hole, tube or channel 4 Concrete First sensor head & Heater 6 Carrying case 5 7 Central unit 8 Power cable 9 Cable roll Batteries 11 Electronics & Wireless radio 10 12 Second sensor unit 13 Third sensor unit 14 Heater Cloud 16 Long term measurement cavity 15 20 Curve of measurement with breathing tube 21 Curve of estimated drying process N 22 Curve of measurement without breathing tube
I a a © 20 CITATION LIST 2 = Patent Literature
N WO200223158 FI-108891
Claims (16)
1. A method for measuring humidity of concrete (4) comprising the following steps: — measuring periodically the humidity and temperature by a first, long term humidity sensor (5) inside the concrete such that the first humidity sensor (5) is positioned inside a ventilated measurement cavity (16) inside the concrete (4) and the ventilation is performed by a ventilation channel (3), — heating the first humidity sensor (5) periodically between the measurements, — measuring the humidity and temperature of the concrete (4) by a second humidity sensor (12) positioned in an unventilated measurement cavity (20) inside the concrete (4), — measuring the humidity and temperature of the outside space of the concrete (4) by a third humidity sensor (13), — adjusting the humidity value measured by the first humidity sensor (5) by the information of the second (12) and third humidity sensors (13), and — calibrating the first humidity sensor (5) between the measurements with a second (12) and third humidity sensors (13) positioned in the same space with the first humidity sensor (12).
2. A method for measuring humidity of concrete (4) in accordance with claim 1, characterized in that the heating of the first humidity sensor (5) is done 2-3 times in 24 hours and the humidity and temperature is measured both before and after these heatings.
S S 25 3. A method for measuring humidity of concrete (4) in accordance with claim 1, 2 characterized in that the heating of the first humidity sensor (5) is done in 1-3 hours D intervals and the concrete (4) is heated during this time with external heaters (14). x a 00 4. A method for measuring humidity of concrete (4) in accordance with claim 1 - 3, 3 30 characterized in that the heating of the first humidity sensor (5) is done for 30 seconds - N some minutes.
N
5. A method for measuring humidity of concrete (4) in accordance with claim 1 - 4, characterized in that the heating of the first humidity sensor (5) is done such that the temperature rises during the heating around 1-5 degrees.
6. A method for measuring humidity of concrete (4) in accordance with claim 1 - 5, characterized in that the first humidity sensor (5) has more tight filter than the second humidity sensor (12).
7. A method for measuring humidity of concrete (4) in accordance with claim 1 - 6, characterized in that the ventilation channel (3) typically has an inner diameter in the range of 0.5-1 mm and the length of the channel is in the range of 5- 25 cm.
8. An apparatus for measuring humidity of concrete (4) comprising the following means: — means for measuring periodically the humidity and temperature by a first, long term humidity sensor (5) inside the concrete such that the first humidity sensor (5) is positioned inside a ventilated measurement cavity (16) inside the concrete (4) and the ventilation is performed by a ventilation channel (3), — means for heating the first humidity sensor (5) periodically between the measurements, — means for measuring the humidity and temperature of the concrete (4) by a second humidity sensor (12) positioned in an unventilated measurement cavity (20) inside the concrete (4), o — means for measuring the humidity and temperature of the outside space of the O 25 concrete (4) by a third humidity sensor (13), 2 — means for adjusting the humidity value measured by the first humidity sensor (5) 5 by the information of the second (12) and third humidity sensors (13), E — means for calibrating the first humidity sensor (5) between the measurements with 00 a second (12) and third humidity sensors (13) positioned in the same space with the 3 30 first humidity sensor (12).
S
9. An apparatus for measuring humidity of concrete (4) in accordance with claim 8, characterized in that it has means for heating the first humidity sensor (5) 2-3 times in 24 hours and the humidity and temperature is measured both before and after these heatings.
10. An apparatus for measuring humidity of concrete (4) in accordance with claim 8, characterized in that it has means for heating of the first humidity sensor (5) in 1-3 hours intervals and the concrete (4) is heated during this time with external heaters (14).
11. An apparatus for measuring humidity of concrete (4) in accordance with claim 8 - 10, characterized in that it has means for heating the first humidity sensor (5) for 30 seconds - some minutes.
12. An apparatus for measuring humidity of concrete (4) in accordance with claim 8 - 11, characterized in that it has means for heating of the first humidity sensor (5) such that the — temperature rises during the heating around 1-5 degrees.
13. An apparatus for measuring humidity of concrete (4) in accordance with claim 8 - 12, characterized in that the first humidity sensor (5) has more tight filter than the second humidity sensor (12).
14. An apparatus for measuring humidity of concrete (4) in accordance with claim 8 - 13, characterized in that the ventilation channel (3) typically has an inner diameter in the range of 0.5-1 mm and the length of the channel is in the range of 5- 25 cm.
O O 25
15. A non-transitory computer readable medium having stored thereon a set of computer O readable instructions that, when executed by at least one processor, cause an apparatus to at = least: I — measure periodically the humidity and temperature by a first, long term humidity N sensor (5) inside the concrete such that the first humidity sensor (5) is positioned 3 30 inside a ventilated measurement cavity (16) inside the concrete (4) and the N ventilation is performed by a ventilation channel (3), N — heat the first humidity sensor (5) periodically between the measurements,
— measure the humidity and temperature of the concrete (4) by a second humidity sensor (12) positioned in an unventilated measurement cavity (20) inside the concrete (4), — measure the humidity and temperature of the outside space of the concrete (4) by a third humidity sensor (13), — adjust the humidity value measured by the first humidity sensor (5) by the information of the second (12) and third humidity sensors (13), and — calibrate the first humidity sensor (5) between the measurements with a second (12) and third humidity sensors (13) positioned in the same space with the first humidity sensor (12).
16. A computer program configured to cause a method in accordance with at least one of claims 1-7 and 15 to be performed.
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Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20205958A FI20205958A1 (en) | 2020-10-01 | 2020-10-01 | A method and apparatus for monitoring the continuous drying of concrete |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20205958A FI20205958A1 (en) | 2020-10-01 | 2020-10-01 | A method and apparatus for monitoring the continuous drying of concrete |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| FI20205958A1 true FI20205958A1 (en) | 2022-04-02 |
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ID=81579278
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| FI20205958A FI20205958A1 (en) | 2020-10-01 | 2020-10-01 | A method and apparatus for monitoring the continuous drying of concrete |
Country Status (1)
| Country | Link |
|---|---|
| FI (1) | FI20205958A1 (en) |
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2020
- 2020-10-01 FI FI20205958A patent/FI20205958A1/en unknown
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