US 3895472 A
Method and apparatus for measuring and filling cavities in concrete structures. In the method aspect of the invention air is withdrawn from the cavity to a preselected pressure. Gas, preferably air, is introduced into the cavity and the volume thereof measured. The gas in the cavity is then withdrawn, up to a small residual pressure and a corresponding volume of filling material then injected. The apparatus aspect of the invention provides both a measuring device and a filling device. The measuring device utilizes a vacuum pump and a gas meter applicable to means effecting communication with said cavity for first evacuating same and then measuring the volume of gas, as air, required to refill it. The filling means comprises a storage device, vacuum pump and pressure means together with a switching valve and means for connecting same to the cavity whereby the cavity may again be evacuated to a desired value of pressure and the filling material then injected thereinto.
Description (OCR text may contain errors)
United States Patent [1 1 Steinhauer et al.
[451 July 22, 1975  Inventors: Ernst Wilhelm Steinhauer, Halver;
Klaus Fischer; Oskar Lower, both of Wetzlar, all of Germany  Assignee: Ernst Wilhelm Steinhauer,
Langenscheid, Germany  Filed: Nov. 15, 1973  Appl. No.: 416,289
 US. Cl. 52/743  Int. Cl. E04C H40  Field of Search 52/743, 744, 741, 742
 References Cited UNITED STATES PATENTS 1,219,272 3/1917 Edison 52/743 X 2,128,336 8/1938 Torstensson.... 52/744 X 2,930,199 3/1960 Jarund 52/744 X 3,307,310 3/1967 Kourkene 52/744 X Primary ExaminerPrice C. Faw, Jr. Attorney, Agent, or Firm-Woodhams, Blanchard and Flynn  ABSTRACT Method and apparatus for measuring and filling cavities in concrete structures. In the method aspect of the invention air is withdrawn from the cavity to a preselected pressure. Gas, preferably air, is introduced into the cavity and the volume thereof measured. The gas in the cavity is then withdrawn, up to a small residual pressure and a corresponding volume of filling material then injected. The apparatus aspect of the invention providesboth a measuring device and a filling device. The measuring device utilizes a vacuum pump and a gas meter applicable to means effecting communication with said cavity for first evacuating same and then measuring the volume of gas, as air, required to refill it. The filling means comprises a storage device, vacuum pump and pressure means together with a switching valve and means for connecting same to the cavity whereby the cavity may again be evacuated to a desired value of pressure and the filling material then injected thereinto.
3 Claims, 7 Drawing Figures PATENTED JUL 2 2 1975 SHEET QOI PATENTEDJUL22 ms 3,895Q472 SHEET 2 PATENTEDJUL 22 ms SHEET PATENTEDJUL 22 ms SHEET FIG.7
METHOD FOR COMPLETELY FlLLING A CAVITY IN A CONCRETE STRUCTURE FIELD OF THE INVENTION The invention relates to a method for completely filling a cavity in a concrete structure, particularly an only partly filled cable duct of a stressed member of a prestressed concrete structure, and wherein the cavity is evacuated prior to the introducing of the filling compound.
BACKGROUND OF THE INVENTION In prestressed concrete structures. for example bridges, the stressed elements are arranged within cable ducts which have a substantially larger diameter than the stressed elements so that in the cable ducts a relatively large space remains empty. After tensioning the stressed members, the cavity must by filled with a relatively thin filling compound, usually a cement slurry. It is by this means that the stressed member is fixedly embedded into the entire structure and only then does it become fully effective for the solidity of the structure.
Even where the greatest care is taken blockages will repeatedly occur during injecting of the filling compound into the cable duct, which blockages interfere with the smooth accomplishment of these operations. Only at a great expense in time and money it is possible to localize in a so-called stressed member the blocked areas. For this purpose, drilling of the concrete is required and in so doing it is necessary also to drill through the cable duct. This presents considerable danger of injury to the prestressing wires. Further, those ducts which because of their inaccessible position within the structure cannot be reached with a drill must remain filled incompletely and the stressed members associated therewith are considered during static calculation as not existing. The structure thus indicates a smaller load-carrying capacity than called for the original design. By checking the static calculation one must, if desired, provide proof that in spite of this deficiency the required safety still exists.
In refilling the cavities which because of blockages were left, there exists the problem that the filling com-.
pound must be introduced into a blind bore. Since the filling compound when advancing in the cable duct fills out its entire cross section, an air pocket is created. The air between the blocked point and the advancing liquid filling compound is compressed and can prevent the filling compound from advancing to the blocked point so that in spite of a reinjecting operation a complete filling of the cable duct can often not be achieved.
In order to remedy this difficulty, the art has already used the evacuating of the empty space prior to filling with filling compound (German Auslegeschrift 1 684 437 published January 5, 1972 This has the advantage of avoiding the air inclusions which can lead to cavities even after the injecting of the filling compound. If for example there is an evacuation to 1/15 of the ambient pressure and the filling pressure is atu, only 1/150 of the cavity of the empty space would remain if the air could not escape or would not dissolve, if one assumes that during injection the access thereto of air is wholly prevented. However, experience has shown that at a value of evacuation which easily is achievable as a practical matter, a complete filling of the empty space is still possible because any likely small air inclusion can be absorbed into the pores of the concrete or is dissolved into the filling compound. However, there remains the difficulty of the proving that the emtpy space is indeed completely filled with filling compound. This proof, however, must be provided if the respective stressed member is to be considered during the calculation as effective.
The problem of a complete filling of a cavity exists not only in the case of stressed members of prestressed concrete structures. There may also exist at various points in a concrete structure tears of cavities (socalled shrink holes) which must be filled, wherein it is also often important that the filling be complete.
Thus, the basic purpose of the invention is to provide a method which permits one without drilling of the structure to obtain proof that a cavity is filled completely with filling compound. The invention is furthermore to provide apparatus for carrying out the method.
SUMMARY OF THE INVENTION The method of the invention is characterized by the following method steps:
a. withdrawing air from the cavity to a predetermined pressure,
b. introducing of gas, preferably air, into the cavity and mearsuring the volume of the in-fiowing gas,
c. determining the volume of the cavity from the amount of gas which entered during the method step d. the gas contained in the cavity up to a small residual pressure,
e. introducing the filling compound into the cavity and measuring the volume of the entering filling compound.
In this method first the volume of the cavity to be filled is measured. If one now introduces filling compound under vacuum and finds that as much filling compound has entered as can be accommodated in the empty space at a complete filling thereof, one can be certain that the cable duct (or other cavity) is completely filled. One may then during the static calculation of the structure include the stressed member into the calculation as actually existing. Thus, use of the method of the invention will avoid drilling into the structure, which in turn avoids, on the one hand, a great amount of work and, on the other hand, the danger of injuring a prestressing wire. The invention method also permits one to carry out a reliable and provably complete filling where drilling into the cable duct is not possible.
In an advantageous embodiment of the method, there is carried out for the purpose of the volume measurement an evacuation to half of the ambient pressure, thus for example, to 380 torr. Thus evacuation to half of the ambient pressure is advantageous for finding the actually existing cavity for the reason that the later entering amount of gas needs then only to be doubled. Of course the known volumes of the lines must then still be subtracted from the calculated value in order to find the actual content of the empty space which must be filled. Prior to the injecting of the concrete a reduction of the pressure to approximately 1/10 to l/l5 of the ambient pressure is sufficient.
An inventive measuring device for use in the abovedescribed method is characterized by a vacuum pump or a connection for a vacuum pump and a gas meter, both being connected to a suction connection, and by a first valve between the vacuum pump or vacuum pump connection and the suction connection and a second valve between gas meter and the suction connection. A reliable volume measurement can be carried out with these basic elements, wherein the amount of gas entering after the partial evacuation is measured with the gas meter.
The measuring device can be improved by various additional devices like a manostat, a pressure gauge and a programming device. Details herefor are defined in the subclaims and will be described in connection with the drawings. The measuring device is advantageously portable so that it can easily be moved on a building site. The weight of the measuring device is not great so that it can be readily carried.
An evacuating and filling device for use in the aforementioned method is characterized by a vacuum pump, a storage tank for the filling compound, a pressure pump which is connected to the storage tank and a multi-way valve arranged between the pressure pump and the vacuum pump. Said valve has a connection which can be connected to the empty space and in one position connects the connection to the vacuum pump and in a further position connects the connection to the pressure pump. A device so constructed permits the transistion from the evacuation to the filling by a simple change in position of the multi-way valve, namely by one single manipulation thereof.
Embodiments and improvements of such a device are defined in the subclaims and will be described also in connection with the drawings.
A multi-way valve according to the invention is characterized in that it has a first chamber and a second chamber, wherein the chambers are connected with one another through a suitable opening and the first chamber has a connection for the supply pipe of the pressure pump and a further connection for the return pipe of the pressure pump and the second chamber has a connection for a line leading to the empty space and a connection for the vacuum pump. Further a slide is so arranged in each chamber that the slide in the first chamber in one position closes the opening for the return of the pressure pump and in the other position closes the connecting opening between the chambers, while the slide in the second chamber in one position closes the connection for the vacuum pump and opens this connection in the other position. Advantageously the slides are coupled with one another in such a manner that the slide in the first chamber closes the connecting opening between the chambers simultaneously with the slide in the second chamber opening the connection to the vacuum pump.
Such a two-chamber construction of a multi-way valve can be manufactured with the sturdiness which is desirous for the special purpose. The multi-way valve will be particularly strong if the slides have domeshaped seals which cooperate with circular openings in the chambers. After removing a cover the nonsensitive parts can be easily cleaned with water. This is required to avoid an incrustation by the cement slurry which flows through the multi-way valve.
Further details of the invention are defined in the subclaims. Illustrative embodiments of apparatus for carrying out the method will be described hereinafter in connection with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a prestressed concrete structure and a schematical illustration of a volume measuring device connected thereto, v FIG. 2 is a cross-sectional view of a prestressed concrete structure and an evacuating and filling device connected thereto, also in a schematic illustration,
FIG. 3 is a perspective illustration of the evacuating and filling device according to FIG. 2,
FIGS. 4 to 6 are schematic vertical cross-sectional views of a multi-way valve and FIG. 7 schematically illustrates the evacuating device and illustrates the washing cycle.
DETAILED DESCRIPTION FIG. 1 illustrates in a cross-sectional view a prestressed concrete structure 1, for example a bridge beam. This prestressed concrete structure contains several stressed members 2 which are arranged within the concrete mass 3. The stressed members consist of a corrugated cable duct 4 in which several prestressing wires or rods 5 are arranged which are stressed with a selected tensile force. After tensioning the prestressing wires 5 to a predetermined value, the cavity between the prestressing wires 5 and the inside of the cable duct 4 is filled with a filling compound, as a rule a cement slurry. For this purpose the filling compound is injected into the cavity. According to FIG. 1 filling compound 6 has advanced from the left to a point 7 at which point blockage developed. Thus an empty space 8 remained in the right half of the cable duct 4 which must yet be filled. With the inventive method described above, the complete filling of the cavity 8 is possible and same can be verified. For this purpose, however, according to the invention first the volume of the empty space 8 is measured which is done with the measuring device illustrated at the right in FIG. 1.
The measuring device has a connection 9 for a vacuum pump 27, a gas meter 10, a first solenoid valve 11, a second solenoid valve 12, a manostat l3 and a manometer 14. The device has also a connecting branch 15 from which a line 16 leads to an intersection 17. From the intersection 17 a line 18 leads to the gas meter 10. The solenoid valve 11 is installed in the line 18. A further line 19 leads from the intersection to the connection 9. The valve 12 is installed into the line 19. The manostat 13 is connected to the line 16 and the manometer 14 is connected to the intersection 17. However, the manometer 14 could also be connected to one of the lines 16, 18 and 19. The vacuum pump 27 is in the illustrated case not considered as a fixed part of the measuring device but is also used in the evacuating and filling device which will yet be described. An independent measuring device could, however, be equipped with a fixedly installed vacuum pump.
The operative connection between the manostat l3 and the solenoid valves 11 and 12 is only schematically indicated. If in the line 16 a predetermined underpressure is reached, the manostat 13 closes a contact and thereby closes the valve 12 and opens the valve 11.
The measuring device operates as follows.
A line 20 is connected to the connecting branch 15, which line 20 leads to a bell 21, the cavity of which communicates with the empty space 8 and which rests closely against the wall 22 of the structure. The vacuum pump 27 is started with the valve 11 closed and the valve 12 opens. When a preselected pressure is reached, for example half of the ambient pressure, thus at sea level approximately 380 torr, the manostat 13 acts to close the valve 12 and open the valve 11. Atmospheric air will now enter through the inlet line 23, flow through the gas meter and reach through the valve 11 the lines 18, 16, 20 and the bell 21 into the empty space 8. The amount of in-flowing air is measured by the gas meter 10. If prior to the entry of the air a pressure reduction of half of the atmospheric pressure took place, the multiplication of the indication of the gas meter with the factor 2 results in the volume of the empty space 8, the bell 21 and the after-connected lines. If one now subtracts from this value the volume of the bell 21 and the lines, then one obtains the volume of the cavity 8. If now, following the inventive method, sufficient filling compound is introduced under vacuum into the empty space 8 that the introduced volume equals the previously measured volume of the empty space 8, one can be sure that the space 8 is completely filled. The device according to FIGS. 2 to 7 is used for filling. This device may be considered first in connection with the schematic illustration in FIG. 2. The device has a pump 24 which is combined with a mixer and can be supplied with the filling compound. The device further has a mulit-way valve 25, a collecting tank 26, a vacuum pump 27 and aline 28 into which a pressurerelief tap 29 is installed.
The multi-way valve 25 has four connections 30, 31, 32 and 33. A return pipe 34 to the pump 24 is connected to the connection 30, a supply pipe 35 from the pump is connected to the connection 31, the alreadymentioned line 28 is connected to the connection 32 and the line 36 to the connection 33, into which line 36 the collecting tank 26 is installed. The multi-way valve is adjusted by rotating eccentric cams which will be described below in more detail. FIG. 2 illustrates the shafts 45 and 46 of the eccentric cams. Levers 47, 48 are connected rotationally fixed to said shafts. The levers 47, 48 are connected through a link 49 to one another in such a manner that during an adjustment of the handcrank 47 the shaft 46 is also rotated. A tap 50 is connected laterally to the multi-way valve 25, on which tap 50 the already-mentioned connection 33 is provided. The connections on the multi-way valve, as also the further hose connections which will need to be disconnected, can be parts of hose quick couplings as they are used for compressed air lines.
The vacuum pump 27 has two connections 37 and 38 to the outside whereby the line 36 is connected to the connection 37 and a washing line 39 can be connected to the connection 38. The vacuum pump 27 is stored in a box 40 in which valves are provided, the operating levers of which are identified with reference numerals 41, 42 and 43 and the operation of which will be described below. A manometer 44 is also arranged in the box, which manometer indicates the pressure in the intake line 36.
The evacuating and filling device which is schematically illustrated in FIG. 2 is perspectively illustrated in FIG. 3. FIG. 3 uses the corresponding reference numerals which also appear in FIG. 2. In addition to the material illustrated in FIG. 2, FIG. 3 illustrates the following.
A mixing container 51 is arranged above the pump 24, in which mixing container 51 the return pipe 34 ends. Besides the mixing container 51 there is arranged a premixer 52 into which the components of the filling compound are introduced and are mixed by stirring. A calibrated measuring rod 51a is provided on the mixing container 51, on which measuring rod one can read how much filling compound was withdrawn from the mixing container during one injection operation. The multi-way valve 25 has feet 25a for installation on the floor. A transparent container 53 is arranged in the box 40 which also contains the vacuum pump, which container 53 has a drain cock 54. Switches 55, 56 are arranged laterally on the box 40 for turning on and off of the device. The arrangement of the container 53 into the cycle is explained in connection with the schematic FIG. 7.
A spray device 58 is provided on the top 57 of the container 53, which spray device can receive washing water through a line 59 into which a cut-off cock 60 can be installed. The cock 60 has an operating handle 41. A line 61 is connected to the lower end of the container 53 and the already-mentioned drain cock 54 is provided therein. Two further lines 62 and 63 are connected to the container 53 at the top thereof. The line 62 leads to a dust collector 64 which is connected in front of the vacuum pump 27. The manometer 44 is connected to this dust collector. A cut-off cock 65 is installed into the line 62. The line 63 leads to the collecting tank 26 and contains a cut-off cock 66. The cutoff cock 65 is associated with the control handle 42 and the cock 66 with the control handle 43.
The multi-way valve 25 will be discussed more in detail hereinafter in connection with the schematic illustration according to FIGS. 4 to 6.
The multi-way valve 25 has a box-shaped housing 65 which is divided by a partition wall 68 into a first chamber 69 and a second chamber 70. The connection 30 for the return pipe 34 to the pressure pump and the connection 31 for the supply line of the pump are provided on the first chamber 69. The connection 32 for the line 28 and the connection 33 for the vacuum pump end in the second chamber 70. An opening is provided in the partition wall 68 of the multi-way valve.
A first slide 71 is arranged in the first chamber 69 and a second slide 72 is arranged in the second chamber 70. The slide 71 has at its both ends domelike seals 73 and 74. The second slide 70, however, has only on its left end a domelike seal 75. Two guide bars 76 are arranged in each of both slides.
The above-mentioned eccentric cams are supported in the housing top 77 (see FIG. 6). FIG. 6 shows in dashed lines an eccentric cam 78, the shaft of which is identified, in correspondence with FIG. 2, with reference numeral 45. The shaft 45 is supported in the lid 77. The coupling of the two eccentric cam 78 and 79 at their shafts 45 and 46 is so arranged that in one position the slides 71, 72 take on the position according to FIG. 4 and upon moving the control lever 47 the position according to FIG. 5.
The filling device operates as follows.
As in the case of the volume measuring, a bell 21, or other connection as desired, is associated with the structure 1 to create the connection with the empty space 8. At the start of the evacuation the multi-way valve 25 is in the position according to FIG. 4, whereby the line 28 is connected to the line 36 so that the vacuum pump 27 can withdraw the air from the space 8. The suction is continued until a sufficiently low pressure is reached. Naturally, in the evacuation of a cavity in a concrete structure a complete vacuum cannot be reached but for the present case is not required. A pressure reduction to approximately 1/10 of the ambient pressure is sufficient. During the evacuation filling compound is continuously recirculated by the pump 24 as indicated by the arrows in FIG. 3. The filling compound flows then through the line 35 through the connection 31 into the first chamber 69 of the multi-way valve 25 and from there through the connection 30 through the line 34 back into the mixing container 51. This prevents the hardening of the filling compound in the line 35 during interruptions in the injection procedure. If the evacuation has sufficiently far advanced and a sufficiently long time was maintained, the hand lever 47 is readjusted so that the multi-way valve is placed as shown in FIG. 5. The vacuum pump 27 is now disconnected from the line 28 and the line 28 is connected to the supply pipe 35 of the pump, namely through the connection 31 in the multi-way valve, the opening 80 in the partition wall 68 and the connection 32 which ends in the second chamber 70. In order to prevent filling compound from reaching the vacuum pump during the repositioning of the multi-way valve, the cock 50 is closed prior to the repositioning.
Filling compound is now injected until the chamber 8 is completely filled. The filling is continued until the pressure noticeably increases in the fill lines, for example to approximately atu. The pressure increase is then an indication of the completeness of the filling and effects also a substantial compression of any residual amount of air. The complete filling is then checked by means of the measuring rod 51a to determine the level difference in the mixer 51 prior to and after the injection and from this the volume taken from the mixer is indicated. In place of a measuring by means of the measuring rod 51a, a special volume device, not illustrated in the drawing, may be provided which is suitable for the through-flow with a relatively thick filling com pound.
After the filling, the bell is first closed and then the line 28 is relieved from pressure by opening the cock 29.
Prior to a new evacuation the hose 28 is flushed. However, residues of filling compound cannot be avoided in the multi-way valve 25 and in the hose 28. During a renewed evacuation these residues are partly forced along. In order to prevent their reaching the sensitive vacuum pump, the interconnected containers 26 and 53 are provided. The container 26 has a notillustrated removable insert which should, as far as possible, be emptied prior to being completely full so that filling of the container 53 is avoided. Should, however, concrete material or other dirt penetrate into the containers 53, then this is still not yet damaging for the vacuum pump. However, after such a contamination the container 53 must be cleaned for which purpose the washing cycle according to FIG. 7 is provided.
For washing, a hose 39 is connected to the connection 38 (see FIG. 3). The valve 60 (FIG. 7) which is connected to follow the connection 38 is now opened. The spray device 58 vigorously sprays the inside walls of the container 53. The washing water flows off through the line 61 and the now-opened drain cock 54.
During this washing operation, the cock 65 is closed to prevent penetration of the washing water and dirt to the vacuum pump 27. A not-illustrated mechanical washing lock is provided which causes the cock 65 to be closed before the cock can be opened and vice versa.
To flush the multi-way valve 25 and the tube lines 36, 28, 34, 35 the cock 66 is opened and the cock 54 is closed. The closing of the cock is assured by the washing lock. The container 53 is now filled and the washing water reaches the multi-way valve 25 through the line 63 and the cock 66. The hoses 28, 34, 35 are disconnected. Through a repeated repositioning of the multi-way valve 25, washing water flows through the hoses 28 or 34, 35 and thus cleans same.
The invention was described in connection with the example of filling of an only partly filled stressed member. It can, however, be used with the same advantages for filling of tears or shrink holes. In this case the tear or the shrink hole is first sealed off from outside and only one suction of injection connection is left open. The method is then carried out with the same apparatus as described. In filling stressed members, the method can also be advantageous if the cable ducts are relatively narrow and therefore their filling is difficult. In such cases the filling can take place according to the inventive method from the beginning and not necessarily only after the occurrence of blockages.
Although a particular preferred embodiment of the invention has been disclosed for illustrative purposes, it will be understood that variations or modifications thereof which lie within the scope of the appended claims are fully contemplated.
The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:
1. Method for completely filling of a cavity in a con- Crete structure with a filling compound, wherein prior to introducing the filling compound the cavity is evacuated, comprising the following method steps:
a. withdrawing air from the cavity to a preselected pressure,
b. introducing gas, into the cavity and measuring the volume of the in-flowing gas,
c. determining the volume of the cavity from the amount of gas which entered during the method step b),
d. withdrawing the gas contained in the cavity up to a small residual pressure,
e. introducing the filling compound into the cavity and measuring the volume of the entering filling compound.
2. Method according to claim 1, in which during the method step a) the evacuation is carried out to half of the ambient pressure.
3. Method according to claim 1, in which during the method step d) the evacuation is carried out to approximately 1/10 to 1/15 of the ambient pressure.