Device and method for measuring the gas permeability of a porous building material

0001The invention relates to a method and an arrangement for measuring the Gas permeability of a porous building material in a structure with a Surface delimiting the porous building materials from the environment.

0002The gas permeability of porous building materials is interesting in several respects. So they are an indication of the current state of this building material from existing building structure, allows conclusions to be possibly or aging load caused cracks formed or decomposition processes, are an indication of intrusion of foreign substances, such as water or moisture, or through long-term chemical reactions occurring Bonds of porosities. The gas permeability of a building material is therefore an essential feature for the quality and durability as well as the state and building structures.

0003In particular, in certain buildings is at certain intervals or at indicates damage to the gas permeability tested. Obviously, it is for example, bridges or other supporting parts quite important determine if perhaps resulting from actual state changes Sustainability is compromised.

0004Due to the importance of periodically or intermittently carried out Checks are already various methods for the measurement of Gas permeability have been developed, for example, also from the Federal Institute for Materials Research and Testing (BAM) in a compendium being represented. One example is the Torrent method. Until now, the Gas permeability determined either to the surface on the building or Samples were analyzed in the laboratory.

0005In these and other known method, a positive pressure or Under pressure artificially applied. The pass through the porous building materials entering pressure equalization or the resultant pressure is then a measure of the gas permeability of the building material evaluated. If a gas permeability test also in deeper layers of the structure be made, it is necessary to take core samples and then To test disks of cores in the laboratory.

0006An example of a measuring device for determining the porosity with a such a process is described in DE 41 06 923 A1, in which a Fluid is injected into the building material to be tested.

0007A disadvantage of this method is among other things that the respective Measurements, for example, also unfavorably located parts of a Building must be made, for example in bridges easily imaginable. Wafting Baukernen leads to damage of buildings and therefore is not or at least not indefinitely possible. Performing each of these tests is also quite expensive, which means that you need to be trying for this reason, the distances between the to keep individual tests as large as possible. This naturally leads that , changes may have already set in a larger scale, when the next measurement is performed, so that might already irreparable damage has been done.

0008The object of the invention is in contrast, a method and arrangement propose, in which the measurement of the gas permeability of a porous Building material with less effort.

0009This object is achieved in an arrangement in that a closed cavity in the interior of the building with distance to Surface of the building material is provided that an air pressure sensor in the Cavity is arranged so that an air pressure sensor in the environment outside of the building is disposed, and that an evaluation unit is provided, which has at least temporarily data connection with the two air pressure sensors having.

0010This object is achieved in a method in that inside the Structural body is a closed hollow space is formed which is opposite to the Environment is completed, that is measured in the cavity of the air pressure is that in the vicinity of the air pressure is measured, that the measured values for the air pressure in the cavity and in the surrounding area continuously or in discrete time intervals to an evaluation unit are added, and that the Evaluation of the variable air pressure values ​​in the area and the dependent variable air pressures in the cavity on the Close the gas permeability of the porous building material.

0011With the invention, the object is achieved, surprisingly. In addition, for the first time, continuous monitoring of the change in Gas permeability possible a so-called monitoring. In continuous or periodic measurements of the internal pressure and the external pressure it can be determined very quickly from the resultant time profiles, whether to changes in the gas permeability result. Doing so is the Natural Atmospheric air pressure change exploited to determine. It is no longer necessary, as previously customary, vacuum pumps, or use compressors to artificially produce a differential pressure and this balance and to draw from the clearing procedure conclusions.

0012The invention is based instead on that in at an air pressure change the atmosphere is provided for in the building with a cavity certain delay precisely this change in air pressure reproduces. If the rise in atmospheric pressure, is of a precisely specific time frames and the air pressure to be increased in the cavity. The dependence between the course of the external atmospheric pressure and the course of the internal pressure is a measure of the gas permeability of the porous building material.

0013It must be used not only for the time delay, although this course also provides for an evaluation. From the Gradient of pressure trajectories can be namely draw conclusions, just from comparing a curve with the gradient of the other.

0014This is of particular advantage to easily weather-related influences to eliminate, such as a during the equalization process additionally occurring difference in humidity, temperature fluctuations etc .. It is interesting not so the actual variation in the respective measured values, but an observation of the entire course. To consider is that changes in gas permeability due are material changes, long-term processes, while the weather and the air pressure changes in relation to short-term changes represent.

0015Examples of such long-term processes such as the addition of Kapillargängen and pores by the formation of chemical compounds with a larger volume than the starting compounds, such as the alkali, sulfate or Ettringittreiben which act as a "bonding porosity". But also other material changes result in a long-term processes to changes the gas permeability.

0016For this very reason, the inventive method is also the conventional methods consider: Exactly the influences that are very far were disturbing and complicated by additional measurements, are compensation calculations and the like are eliminated or considered had, now play virtually no role: Since the measurement continuously can be carried out over an extended period of several years, does not have to be considered whether the measure as the summer and winter, low or high temperatures, at low or high humidities has taken place. It must instead only values ​​are compared, the words, for example, simplifies the case of similar outer Conditions were taken, which during the same period randomly repeated in intervals. Since only the changes occurred are interested and for example, lead to warnings or must, has recognized only the exceeding or falling below certain limits be or continuously exceed or fall below certain Thresholds for certain periods.

0017After a single installation of the device according to the invention can for an arbitrary length of the measurement cycle the change in gas permeability to be observed. This therefore is an on-line monitoring of a building possible in terms of the gas permeability property. damage processes can be recognized as extremely early

0018The air pressure sensor which detects the air pressure in the environment, can Of course, an existing sensor about from a weather station be; he can also be quite a distance from the building are, if it is still possible mathematically to the air pressure in close very close to the surface of the building. must be remembered thing is that the atmospheric pressure is also dependent on the height and the Pressure equalization through the porous building materials through the air pressure just interesting outside of the building.

0019The evaluation must not be placed on the building, but can be provided by this at a substantial distance. This makes it possible, for example, for a larger building, such as a power plant, or also a section of motorway with several bridges, a common set up monitoring. As a rule, the measuring results of Pressure sensors yes only becomes relevant during the measurements by clicking on suggest deviations from a certain prescribed standard.

0020The data connection to the evaluation unit with the air pressure sensors also must not necessarily take place physically. constructed in a particularly simple Embodiments can also be dispensed with a remote data transmission will. There is then a floppy disk or other data carrier having the recorded pressure data, so to speak manually for evaluation transported to a (in this case not simultaneous but reproducible) establish data connection, wherein the recording of the print data on the Volume representing the first part of the data connection.

0021In addition, through a deeply staggered assembly of several sensors yet in addition to create a continuous depth profile with respect to the Gas permeability possible. Even the detection of changes in different parts or layers of a building to be made possible. The process is therefore a depth-selective leakage measurement and also for a time-dependent monitoring of the tightness of the building material suitable. It can be information about the quality and durability as well as the achieve environment-related change of the building material.

0022Especially easy it is of course possible, just in the preparation of Building provide the corresponding devices, so that the The method can then be carried out permanently. It is also an suitable retrofitting in interest structures.

0023In one embodiment of the method, in the building structure by means of a Bore created a void and then gas-tight with a Body reclosed, for example, with a closing cylinder. It the result is a defined cavity in the building material. The internal pressure in this Cavity is measured with the pressure sensor. By the atmospheric Change in pressure is also formed in this process, a differential pressure between internal pressure and atmospheric air pressure outside the cavity. The speed of adjustment between internal pressure and external pressure is again evaluated and is a measure of the tightness of the building material of the Building structure.

0024In a preferred embodiment the bore is formed by a Lock cylinder in turn equipped so that the resulting cavity is isolated from the external atmospheric pressure. Of the Lock cylinder having a bore, in turn, by a Helical element can be closed. This helical Element can at both ends with in each case the air pressure sensor for the Cavity or be provided for the outdoor area, so that a particularly simple exchange of all measuring instruments by the easy replacement of this item is possible.

0025The invention with reference to some embodiments is under Explained in more detail with reference to the drawings. Show it:<dl tsize="7"><dt><b>figure 1</b></dt><dd>a schematic section through a structure with a Embodiment of the inventive measuring device;</dd><dt><b>figure 2</b></dt><dd>a schematic section through a structure with a another embodiment of the inventive measuring device;</dd><dt><b>figure 3</b></dt><dd>a schematic section through a structure with a further alternative embodiment of the invention Measurement apparatus;</dd><dt><b>figure 4</b></dt><dd>a schematic section through a building while a first phase of a method according to the invention;</dd><dt><b>figure 5</b></dt><dd>a schematic section through a building during second phase of an inventive method; and</dd><dt><b>figure 6</b></dt><dd>a schematic section through a building during third phase of an inventive method.</dd></dl>

0026In the figure 1 a structure 10 is illustrated having a surface eleventh He consists of a porous construction material 12, and is broken away in the Figure 1 represented, that is, it continues outside the figure area. Of the Structure may, for example a building or part of a building, For example, a bridge, a skyscraper, a power plant, a Tunnels or other, more interesting for a review of building 10th

0027In the preparation of the structure 10 of the building material 12 is already sealed cavity 20 has been recessed. This cavity has 20 defined dimensions and a defined position, in particular a defined Volume and a defined distance from the surface eleventh

0028Outside of the building 10 is located in the illustrated embodiment, the external environment 30 in which the ambient air pressure <b>P_u</b>prevails. The air pressure within the cavity is as<b>P_i</b> designated.

0029The air pressure <b>P_i</b> by means of an air pressure sensor 42 inside the Cavity 20 determines the air pressure <b>P_u</b> Near 30 is a Air pressure sensor 43 measured. The two air pressure sensors 42 and 43 are each connected to an evaluation unit 45, the these measurement results <b>P_i</b>and <b>P_u</b> are fed and which evaluates the changes. The Evaluation unit 45 is usually outside of the structure 10, For example, at this, or even at a distance from the building 10 lying location. In the latter case are different ways conceivable, the measured values ​​of air pressure sensors 42 and 43 to the evaluation unit 45 transferred.

0030In an absolutely tight building material 12, the internal pressure would <b>P_i</b> within the Cavity 20 to be constant, since no replacement in the cavity 20 contained gas molecules with the outside environment 30 takes place.

0031If the building material but porous, so an exchange of the gas atoms by the Pore ​​system of the building material 12 and the internal pressure <b>P_i</b> sought in the cavity 20 a balance with the external atmospheric pressure <b>P_i</b> Near 30 to.

0032The more porous the building material, the faster this compensation. Changes Now the external atmospheric pressure <b>P_u</b>, So it follows the internal pressure <b>P_i</b> with a certain delay, which depends on the porosity of the building material 12th The corresponding values ​​in the evaluation unit 45 with each other compared and it appropriate inferences about the porosity of Building material 12 are taken. The result of the automatic with the Evaluation unit 45 evaluated pressure equalization function is the Measure of the tightness of the building 10th

0033In the <b>figure 2</b> there is shown an embodiment in which in an already the structure standing 10 of a building material 12 initially still no cavity was 20 provided, this will however be subsequently introduced. This is the Example necessary when in existing bridges or tunnels subsequently on-line monitoring is to be integrated.

0034Here, a bore 21 is subsequently carried from the outside of the area 30 the building material introduced 12, thus creating a cavity 20th This initially with around 30 in contact cavity 20 is from the Area 30 is separated again by a closing cylinder 22, so that the remaining cavity 20 as in the example of Figure 1, a defined position and has a defined volume. The cavity 20 is then between the 30 remote from the environment side, ie the base point the shutter cylinder 22 and the outermost point of the bore 21st

0035Also in this example is again a cavity 20 in the thus formed Air pressure sensor 42 for the internal pressure <b>P_i</b> and outside in the environment further air pressure sensor 43 for the ambient pressure <b>P_u</b> provided. Both Air pressure sensors 42 and 43 are provided with an evaluation unit 45 in Compound, said here this connection a line or even a can be long-distance transmission ability.

0036The embodiment of <b>figure 3</b> also shows a cavity 20 in a Building 10, which cavity 20 subsequently through a bore 21 is created. Again, a shutter cylinder 22 is provided, then the Cavity 20 is separated from the surrounding 30th In contrast to However, embodiment of Figure 2 is an air channel 23 centrally in Lock cylinder 22nd

0037By this air passage 23, it becomes possible, the air pressure sensor 42 for the internal pressure <b>P_i</b> in the cavity 20 after insertion of the closure cylinder 22 still later to install and remove, such as to Repair, maintenance or replacement. The air channel 23 is a proper screw 24 closed in order to influence the internal Surface of the cavity 20 to be prevented by external influences.

0038With such a measure it is possible not only in any to control time intervals, the change in one and the same measuring point and changes can be seen, but also the sensor 42 remove for calibration or the measurement volume in the cavity 20 below the lock cylinder 22 by means of a short-term surge measurement catching to the general gas laws.

0039The methods presented are not only concrete, but also for building materials 12 suitable natural stone and other materials. They allow in not illustrated embodiments also deeply selective leakage measurements.

0040In the <b>Figures 4 to 6</b> are three phases of a method according to the invention exemplified.

0041In the figure 4 is again initially a structure 10 of a building material 12 shown. The surface 11 is from around 30 a bore 21 in the structure 10 is introduced. On the outside of the surface 11 is a plastic or Metal ring 51 placed around the edge of bore 21 around and there provisionally fixed. The ring 51 is adapted to the surface 11 of the Structural body 10 to protect against adhesive to in another, yet discussed process steps is used and, if necessary, a seal and / or contamination of the surface 11 may contribute to a Corruption of the measurement results for the entire building with the building could cause 10th

0042In the bore 21, a base cone 25 is to reduce in the bore 21 incurred balancing volume used in the later cavity 20th

0043A lock cylinder 22 with an air channel 23, in the first test Hole 21 is inserted. Thereafter, by Justiernuten, optionally Adjusting washers and appropriate measurements and tests the depth of Closing cylinder 22 carefully determined and these then again withdrawn.

0044Thereafter, the shutter cylinder 22 to a sealing ring 26 is in the Hole 21 is inserted and above the sealing ring 26 fed epoxy glue applied. Then the lock cylinder 22 is slowly into the hole 21 inserted, with the air channel 23 is not closed, so that no Failure of insertion occurs.

0045When the shutter cylinder 22 rests at the base, the air channel 23 is with a screw 24 is sealed.

0046The Klebkragen with excess epoxide is prior to curing of the adhesive carefully removed so that the surface 11 of the building material 12 not is soiled or wetted with adhesive. The Klebkragen is also the mentioned plastic or metal ring 51 which is now no longer required.

0047The adhesive in the rest now holds the lock cylinder 22 in the bore 21 firmly. When cured, the screw 24 is unscrewed and the air pressure sensor 42 through the air passage 23 into the formed cavity 20 introduced. This introduction is carried out slowly to a training to avoid excess pressure in the test volume as possible.

0048After performing this procedure and structure of the not shown Elements (second air pressure sensor 43 and unit 45), the Processes are carried out in practice.

LIST OF REFERENCE NUMBERS

0049<dl tsize="2" compact="compact"><dt>10</dt><dd>structure</dd><dt>11</dt><dd>surface</dd><dt>12</dt><dd>porous building materials</dd></dl><dl tsize="2" compact="compact"><dt>20</dt><dd>cavity</dd><dt>21</dt><dd>drilling</dd><dt>22</dt><dd>lock cylinders</dd><dt>23</dt><dd>air duct</dd><dt>24</dt><dd>screw</dd><dt>25</dt><dd>root cone</dd><dt>26</dt><dd>sealing ring</dd></dl><dl tsize="2" compact="compact"><dt>30</dt><dd>Surroundings</dd></dl><dl tsize="2" compact="compact"><dt>42</dt><dd>Air pressure sensor</dd><dt>43</dt><dd>Air pressure sensor</dd><dt>45</dt><dd>evaluation</dd></dl><dl tsize="2" compact="compact"><dt>51</dt><dd>Plastic or metal ring</dd></dl>