Device for detecting delaminations and methods of use thereof

A device for detecting hidden delaminations in a structure subject to hidden delaminations comprising a rotary percussion tool head adapted at an end thereof to connect to an extension pole, wherein said head comprises at least one circular member, each circular member having on the periphery thereof projections extending in the radial direction and spaced apart in the circumferential direction, and a method of using same.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a device for detecting hidden flaws, such as
 delaminated areas, in a structure such as a concrete slab, and methods of
 using the device.
 2. Discussion of the Background
 Methods of and devices for detecting the presence of hidden flaws within
 steel reinforced suspended concrete slabs have been suggested in the prior
 art. The flaw to be detected is a separation, or delamination, of the
 layers of concrete within the slab. The delamination is caused by
 corrosion of the reinforcing steel within the slab. Corrosion of the steel
 within the suspended concrete slab is caused when moisture and chlorides
 make contact with the reinforcing steel. Once the steel begins to corrode,
 oxidation occurs and the cross-sectional dimension increases which causes
 areas within the concrete slab to debond and separate into two or more
 layers. This condition occurs in areas where there are freeze-thaw cycles
 as well as in areas where there is a preponderance of chlorides, either
 air-born or where de-icing salts are used for roadways and bridge decks.
 Once the oxidation and the resultant delamination starts, the rate of
 deterioration accelerates until a condition exists where large concrete
 fragments break loose and fall, or, in severe cases, a serious compromise
 in structural soundness of the slab occurs. Early detection, therefore, of
 the unseen delamination is important to keep repair costs to a minimum.
 In the past, detection of delaminations in the bottom exposed surface of a
 suspended concrete slab, or soffit, has been to repeatedly tap the
 surface, usually with a hand held hammer producing the sound which has
 been found to occur when the slab is delaminated. This method of initially
 detecting the presence of delamination is regarded as a reliable means to
 find problem areas which are not visually apparent. Most soffits are out
 of reach, so a ladder or scaffolding is usually required to reach the
 surface.
 The prior art has employed measurement of sound or vibration variables in
 order to ascertain changes in a mechanical element, such as a bridge, such
 as disclosed in U.S. Pat. No. 1,871,756 to Spath. Other prior art
 references have disclosed various rotary devices for obtaining acoustical
 data in the inspection of structures, workpieces, etc. for hidden defects,
 such as U.S. Pat. No. 3,714,817 and U.S. Pat. No. 3,771,354, both to
 Miller, and U.S. Pat. No. 4,856,334 to Shearer et al. U.S. Pat. No.
 3,999,626 to Adams discloses a seismic method and apparatus for generating
 seismic signals which can be detected at great distances either on the
 surface or underground. None of the above references are concerned with
 defects in concrete structures, and all are drawn to relatively complex
 apparatus.
 A method and device in the prior art disclosed for detecting delaminations
 is the relatively complex apparatus disclosed in U.S. Pat. No. 3,937,065
 to Milberger et al. The Milberger et al apparatus is drawn to detecting
 delaminations beneath a surface and involves the receiving and measuring
 of acoustical responses with an acoustic receiving transducer, and other
 sophisticated components. Milberger et al's apparatus is not well adapted
 for detecting delaminations in areas other than the underside of floors
 and decks.
 Another prior art delamination device is that disclosed in U.S. Pat. No.
 3,361,225 to Nichols. Nichols' device comprises in combination an
 externally-toothed wheel, and means comprising a hand-held handle and
 means for pivotally mounting the wheel on the handle, for walking the
 wheel across a member to be tested, for causing the individual teeth of
 the wheel to sequentially strike the member, for producing individual
 sequential acoustical sounds indicative of the internal structure of the
 member, an abnormal acoustical sound being indicative of an abnormal
 internal structure. As an externally-toothed wheel, Nichols employs a disk
 and a single substantially coplanar set of radially outwardly-extending
 pegs mounted on the periphery of the disk. For extremely large panels,
 Nichols discloses ganging a plurality of such devices, whereby the ganged
 test devices may be simultaneously rolled across a panel to be tested,
 wherein each device detects independently of the other. Nichols discloses
 further the use of an electrical pickup device, such as a microphone, to
 detect the acoustical sounds in lieu of the use of the human ear and human
 judgment. The only environment disclosed for use of the Nichols' device,
 however, is in the detecting of abnormalities in structural elements known
 as honeycomb panels. A honeycomb panel is defined therein as a three-part
 sandwich, wherein a central core section is sandwiched between a top and
 bottom sheet or skin portion. The Nichols' device is intended to detect
 abnormalities in the bonding of the core to either the top or bottom
 portion. Nichols suggests nothing with regard to other structures, such as
 suspended concrete slabs or soffits and other generally inaccessible areas
 subject to delaminations.
 A need thus still exists in the art for a relatively simple and inexpensive
 device for measuring delaminations in structures subject to such
 delaminations, and particularly such structures, such as suspended
 concrete slabs or soffits, that have previously not been tested for
 delaminations without great effort.
 SUMMARY OF THE INVENTION
 It is therefore an object of the present invention to provide an improved
 device which is simple and inexpensive for detecting delaminations in
 structures subject to such delaminations that heretofore were not easily
 subject to detection, such as suspended concrete slabs or soffits.
 It is another object of the present invention to provide a method for using
 such a device.
 The device is a rotary percussion tool head adapted at an end thereof to
 connect to an extension pole of any length, thus allowing contact of the
 tool head with a surface to be detected located at various distances from
 the testing location, such as the ground.

DETAILED DESCRIPTION OF THE INVENTION
 The device is a rotary percussion tool head adapted at an end thereof to
 receive an extension pole of any length, thus allowing contact of the tool
 head with a surface to be detected located at various distances from the
 testing location, such as the ground.
 The preferred use of the device is to conduct sounding analysis to
 determine the extent of delaminated and spalled concrete in the under side
 of overhead slabs or soffits. The design of the tool includes a preferably
 telescopic extension pole and a preferably machined tool head, which
 allows the work to be done from the slab below, excluding the need for
 ladders in most applications. The tool-head can be removed and hand held
 for close work. This significantly speeds the entire process and with
 considerably less fatigue, while the traditional process of using a hammer
 is tedious and time consuming.
 The tool head comprises at least one, and preferably two, circular members,
 such as wheels or discs, of equal size and generally parallel to each
 other, each circular member having on the periphery thereof projections,
 preferably coplanar, extending in the radial direction and spaced apart,
 preferably equidistantly, in the circumferential direction. Preferably,
 each circular member-projections combination is a ball bearing idler
 sprocket, preferably made out of hardened steel, press-fit mounted and
 spaced apart from each other to cover an area, preferably about 5 inches,
 wide. Preferably, the tool head is snap-fit on a telescopic extension pole
 long enough to reach the exposed surface of the under side or soffit of a
 suspended steel reinforced concrete slab.
 In use, the tool head is rolled along the surface so that the projections
 each contact the surface sequentially to produce the percussive force to
 effect the sound necessary to distinguish solid concrete from delaminated
 or spalled concrete.
 The device and method relies on detection by the human ear, as each
 projection strikes the surface, and the differences in sound between
 flawed sections and unflawed sections, which are known to persons skilled
 in the art of detecting delaminations, are easily determined by the human
 ear alone, and do not need the addition of any acoustical or other
 enhancements, such as those of Milberger et al or Nichols, supra. While
 such enhancements are not necessary, the device may contain such
 enhancements, such as the microphone of Nichols.
 In a most preferred embodiment, as shown in FIG. 1, the device comprises a
 "T" shaped chassis with a 45.degree. angle in a plane generally parallel
 to the plane of each of the sprockets. The material used is round aluminum
 rod at a diameter of 0.75 inches. One inch on each side of the top portion
 of the chassis is machined down to a smaller diameter of 0.640 inches to
 allow the ball bearing idler sprocket to slip onto the chassis and stop
 against the shoulder of the chassis where the outside diameter is greater.
 The machined ends of the chassis where the sprockets fit must be machined
 to a tolerance tight enough to engage the ball bearing and still allow the
 sprocket to spin. This is referred to as a press-fit bearing. The chassis
 is angled at 45.degree. to allow easy contact with the surface of the
 soffit slab. Early prototypes of the tool, which did not have the angle,
 and thus represents a less preferred embodiment of the present invention,
 proved to be difficult to maintain constant contact with the surface due
 to the angle at which the extension pole must be held. That is, the more
 vertical the extension pole must be held (because the soffit is higher),
 the more difficult it becomes to maintain constant force. With the angle,
 however, the tool head is offset and can be rolled along the surface while
 applying minimum upward force.
 At the outside end of the tool chassis, the 0.75 inch round aluminum rod is
 machined down to 0.640 inch to allow the attachment of an aluminum
 hollow-tube adapter. This adapter then snaps into a telescopic extension
 pole to allow a reach of on the order of 12 feet.
 FIG. 2 shows a method of using the device on various surfaces, e.g., the
 ground, a wall, and a soffit.
 Materials other than aluminum can be used for the device, including other
 metals or non-metal natural materials such as wood, or synthetic materials
 such as plastics. Other angles can be used, depending upon relative
 locations of tester and surface to be tested. The device can also be made
 smaller or larger, with concomitant change in rod and pole diameters,
 depending on the size of the areas to be tested. When more than one
 circular member is present, the distance between respective members can be
 set at any distance. While FIG. 1 shows a preferred telescopic extension
 pole, the present device includes all other means for extending the length
 of a device, such as smaller sections which can be piggy-backed to each
 other by connections well-known in the art, such as threaded or
 press-fitted connections and the like. Additionally, the tool head and any
 extensions can be fashioned as a unitary article, i.e., wherein the tool
 head and extensions are constructed as one piece.
 Having generally described this invention, a further understanding can be
 obtained by reference to certain specific examples which are provided
 herein for purposes of illustration only and are not intended to be
 limiting unless otherwise specified.
 EXAMPLE 1
 Field Test Results
 The field tests were conducted on concrete structures in the Northeastern
 U.S. During a typical building evaluation in Washington, D.C., the device
 shown in FIG. 1 was used to test the extent of delaminated concrete in the
 soffit slab of a 20,000 square foot parking garage. The evaluation found
 1.36% delamination and was completed within 1 hour. Manually, the same
 process took 5 hours and found only 1.09% delamination. Using the device
 increased work productivity by 500%. In addition to the significant test
 results, it became evident that it is equally effective for use on beams,
 columns and floor slabs. In a parking garage in Baltimore, Md., two beams
 at a height of 11 feet were analyzed and found to have extensive
 delaminated concrete on the under side of the beam and on both vertical
 surfaces. All work was completed without the need for ladders.
 Obviously, numerous modifications and variations of the present invention
 are possible in light of the above teachings. It is therefore to be
 understood that within the scope of the appended claims, the invention may
 be practiced otherwise than as specifically described herein.