METHOD OF IOTA NU SIGMA IOTA TAU THETA TESTING CONCRETE FOR QUALITY, AND MEANS FOR IMPLEMENTING THE METHOD

Abstract: The method consists of introducing into concrete to be tested (1) a metal expansion plug (5) which is caused to expand inside a previously drilled hole (2) formed with an inside taper (4) that enlarges its cross-section. After tightening, a jack is positioned with an abutment disk (11) having its axis aligned to the plug axis (13) and thereafter a tensile force is applied to the protruding shank of the plug up to the point a breaking of a concrete cone occurs, which cone has a taper angle within the range of 60<o> to 70<o>. The value of the tensile load, when read against appropriate tables, enables evaluation of the compressive strength of the concrete being tested.

Description: "METHOD OP IN SITU TESTING CONCRETE FOR QUALITY, AND MEANS FOR IMPLEMENTING THE METHOD" Technical field This invention relates to a method of in situ testing concrete for quality, and to means for implementing the method. Background Art Several methods of testing concrete for quality are known which may be classed as "destructive" and "non destructive" methods. The method of this invention belongs to the broad class of the "non destructive" testing methods. From the latter, a method is known which provides for a single in situ operation consisting of first drilling a hole, and then enlarging the hole interior with a special cutter until the hole can accommodate a suitable tool bit which will anchor itself within the hole. After the tool bit has been anchored securely, it is withdrawn by pulling on it with a jack until the concrete breaks * Such known method, while affording the checking of any part of a structure at any time after its emplacement, shows to be highly expensive in that it requires the availability of special equipment to prepare a hollow seat for a special anchor element. DISCLOSURE OF THE INTENTION It is the technical task of this invention to provide a method which is at one time simple and accurate. A consequent primary object is to provide a sequence of operative steps which can be ' readily implemented without any special difficulties. Another object is to provide a method which can be used at any time after the concrete has been allowed to cure. A further object is to provide a method employing for its operative steps, as far as possible,customary equipment for this field. Still another object is to arrange for the use, wherever feasible, of readily available components on the market. These and other objects, such as will become apparent herein below, are all achieved by a method of in situ testing concrete for quality, characterized in that it comprises the following steps: (a) drilling concrete to be tested with a perpendicular hole to the concrete surface where the test is to be made; (b) enlarging the hole interior to provide a frusto-conical area; (c) introducing an expansion plug into said frusto-conical hole area; (d) expanding the plug within the hole; (e) positioning a hydraulic jack equipped with an abutment ring and a swivel means of engagement with said expansion plug, whereafter a pull is applied to the shank of said expansion plug until the concrete breaks and the ultimate tensile strength thereof can be measured. The means for implementing said method comprises a plug arranged to only expand at the deepest portion thereof, and a pulling jack having a swivel device for connection to the .plug and an abutment ring whose inside dimensions are selected so as to provide a breaking cone with an angle within the range of about 60° to 70°' * BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will be more clearly undentsood from the following detailed description of a preferred embodiment thereof, given herein by way of illustration and not of limitation with reference to the accompanying drawing sheets, where: Figure 1 is a sectional view of an a3rea where a hole according to this invention has been drilled, which view points out the shape of the hole made in the concrete; Figure 2 illustrates the introduction and the shape of the expansion plug; Figure 3 illustrates the expansion of the plug within the hole; Figure 4 shows how the abutment ring is positioned and the shape of the breaking cone determined thereby; and Figure 5 is a sectional view through the jack employed for the plug withdrawing step. WAYS OF CARRYING OUT THE INVENTION With reference to the cited drawing figures, n orde to carry out the method of this invention with a concret structure 1 to be tested for quality, a cylindrical hole 2 is first drilled which, at its innermost area indicated at 3 » is enlarged to provide a conical surface, indicated at 4. This operation is performed by means of a tool which allows the drill bit, that has just formed the cylindrical hole 2 and is suitably designed to only work on the wall of the area 3 of the hole,to be in¬ clined so as to generate an inside taper. Then, a plug 5 is inserted into the hole 2 which comprises a cylindrical sleeve 6 associated, at its most inwardly located portion with respect to the hole, with a plurality of expansion segments 7. The cylindrical sleeve 6 contains a threaded shank 8 the innermost portion whereof is shaped to form an expandingbody 9 leaving all around a gap 10 for the insertion of the expanding segments 7. Expansion takes place on striking the cylindrical sleeve 6 so that the expansion segments 7 are driven into the gap 10 and made to spread over the cone 3 , as shown in Figure 3» Thereupon, the plug will be anchored securely inside the hole 2. By applying then a pull to the threaded shank 8, the -segments 7 will be urged further against the conical surface 4 following a possible short initial sliding movement. On completion of this operation, a metal abutment ring 11 is positioned which has a middle hole 12 with its center coinciding with the axis 13 of the threaded shank. The size of the hole 12 is selected so that the angle of the ideal cone to be obtained by joining the cone 9 to the inside circumference 14 of the hole 12 can have an amplitude of 60° to 70 β . At this point, using a jack not shown in Figure 4 which may be of any type so long as it can optically display the force it applies, a pull is exerted on the threaded shank 8 in the direction of the arrow 14 by reaction against the metal abutment ring 11. • This pull force is maintained until a concrete cone breaks off which has for its base a circle of the same size as the hole 12 in the abutment ring 11 • The height of the cone is instead substantially equal to the length of the plug that had been inserted into the hole. The value which has been ascertained of the breaking stress on the concrete, when compared to appropriate tables, enables the characteristics of the concrete to be evaluated. A suitable jack for implementing the method in com¬ bination with the plug described above, is shown in Figure 5. As may be seen, the jack comprises a cylinder 1β accommodating a piston 17 which is driven upward by pressurized oil supplied into the inner chamber 18 of the cylinder through a line 19 from a pump, not shown, to which line 19 a pressure gauge 20 is connected to measure the internal pressure * The piston 17 extends so as to form a rod 21 which, i turn, extends to form a universal joint 22 to which a connector 23 is fitted which is then locked on - β - application of a cross pin 24. Said connector 23 has a threaded hole 25 in which the threaded shank 8 of the plug, previously driven into the concrete, is screwed in. The universal joint and the connector are both contained within a metal bell-like .casing 26 which is secured at the top to the cylinder 16 as by screwing, and at the bottom to- the abutment ring 11. At the upper portion between the shank 21 and cylinder 16, there is mounted a comparator 27 serving the function of optically displaying any slipping of the plug, which would be indicative of ineffective grip on the concrete and of an improperly made hole. The universal joint connected between the plug and the jackpiston rod prevents, within limits, the occurrence of an offcenter tensile condition which would alter the readings and make the method unreliable, Such a situation would occur where either the bearing surface of the abutment ring is uneven, or the plug has been inserted into a hole which is not truly perpendicular to the surface of the work. The inventive method described in the foregoing is specially simple in that, with the sole exception of the dynamometric jack, it utilizes standard low cost equipment that is easily operated. The plug may conveniently be of a throw away type, since it is quite simple construction-wise and hence inexpensive to replace. For these reasons, the concrete test may be repeated at several locations without incurring excessive cost. Evidently, the test may be carried out on any structure types whenever their quality must be checked. This is specially advantageous both with new structures and with structures that for a reason whatever have undergone exceptional stresses, such as earthquake vibrations, the effects of which may create a potentially dangerous situation and command, therefore, an accurate checkup. The plugs, while requiring the particular features specified herein before, can be made by using the same equipment and technologies which are used in the manufacture of hardware for concrete. The novel aspect of the invention is, therefore, to be seen in the combination of a simple non destructive method that may be applied at any time, ith a low cost plug, that may be used once for each test. It may be appreciated from the foregoing description that all of the invention objects have been achieved, and in particular that a specially simple and economically convenient- method has been provided which employs low cost materials and components. From experimental tests, it appears that the angle which yields the best direct correlation of compressive strength to extraction force is in the 60° to 70° range. Based on this angle range, charts and graphs have been prepared which make the interpretation of the test results an easy task. Of course, this inventive concept may be implemented by means which are different from the • ones described, so long the method remains the same»

Claims: CLAIMS 1. A method of in -situ testing concrete for quality, characterized in that it comprises the following steps: a) drilling concrete to be tested with a perpendic- ular hole to the concrete surface; b) enlarging the innermost portion of the hole to provide a frusto-conical cavity; c) introducing an expansion plug into said frusto-conical hole area; d) expanding the plug within the hole; e) positioning a jack equipped with an abutment ring and a swivel means of engagement with said expansion lug, whereafter a pull is applied to the shank of said expansion plug until the concrete breaks and the ultimate tensile strength thereof can be measured. 2. A method according to claim 1, characterized in that said innermost portion of the hole is enlarged with a suitable drill bit guided by a tool which allows for a wobbling movement thereof to only enlarge the hole at its innermost portion. 3. A method according to claim 1, characterized in that the expansion of the plug is conveniently brought about by striking its body to drive expansion segments into the gap between the plug and hole wall. 4. A means for implementing the method according to claim 1 which comprises a plug arranged to only expand at the deepest portion thereof, and a pulling jack having a swivel device for connection to the plug and an abutment ring whose • inside dimensions are selected to provide a breaking cone with an angle within the range of about 60° to 70°. 5. A means according to claim 4, characterized in that said expansion plug comprises substantially a cylindrical sleeve associated with a plurality of expansion segments, there being inserted into said sleeve a-threaded shank which has, on the side of said expansion segments, a conical enlargement. 6. A means according to claim 4, characterized in that said abutment ring has a central hole of a size such as to form a breaking cone with an angle of 60° to 70°, and with a height being equal to the inserted plug length. 7. A means according to claim 4, characterized in that said jack has a mechanical swivel joint to connect the movable rod thereof under oil pressure to the plug shank, said swivel joint being adapted to make the plug and the jack piston rod axially in— dependent during the pull operations. 8. A means according to claim 4, characterized in tha ' said swivel joint is a universal joint. 9 * A means according to one or more of the claims 4 to 8, characterized in that it comprises experimental charts adapted to allow the concrete characteristics to be determined according to the extraction force which breaks off a concrete cone. 10. A method of in situ testing concrete for quality and means for implementing said method, character- ized in that they comprise one or more of the features herein illustrated and described.

Inventors: MENEGHETTI FIORENZO, MENEGHETTI TIZIANO, MENEGHETTI, FIORENZO, MENEGHETTI, TIZIANO
Applicants: MENEGHETTI FIORENZO, MENEGHETTI TIZIANO, MENEGHETTI, FIORENZO, MENEGHETTI, TIZIANO
Application year: 1985
Main classification: G01N3
IPC codes: G01N3, G01N33