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ST9302-SY011008�Tg302 ENGINEERS P�-to l wjE ARCHITECTS (( h1ATERIAISSCIENTISTS Wald -e �. ?- 0�u�erR >�1 � ?V IC 3 Executive Summary Investigation to Detect Mud Balls in Sandy Lake Road Pavement for Alpha Testing, Inc. 8 October 2001 W)E No. 2000.3576.2 Wj ENGINEERS ARCHITECTS MATERIALS SCIENTISTS Douglas W. Deno, PE Senior Consultant Wiss, Janney, Elstner Associates, Inc. 3050 Regent Boulevard, Suite 100 tel 972.550.7777 Irving, Texas 75063 fax 972.373.9403 www.wje.com ddenoc4je.com WISS, JANNEY, ELSTNER ASSOCIATES, INC. 3050 Regent Boulevard, Suite 100 Irving, Texas 75063 -3107 (972) 550 -7777 WJ E f \l,I \LII,� IIITfLI� \IAI F 1\1 \1 f I I ti Fti We proposed that this work be performed in a phased manner, the initial phase being a trial program to determine the reliability of the method and determine the required spacing of the impact readings. The results would be used to establish statistically reliable test program with proper confidence limits. The work was to be limited to a few selected panels in the westbound lanes, and was to be performed following construction of the east bound lanes. INVESTIGATION The initial test program was performed during the week of August 13 -17, 2001, at six selected pavement panels (between control joints and two lanes wide) in the westbound lanes. The approximate locations, from east to west,and extent of visible surface voiding were: Panel 1 — Sixth panel west of Nash Street. "Good" panel with only a few small surface voids. Panel 2 — Fourth panel east of Holly Street. `Bad" panel with many visible surface voids, some of which are large. Panel 3 — Third panel east of Holly Street. "Bad" panel with many visible surface voids, some of which are large. Panel 4 — Sixth panel east of Lodge Road. "Moderate" panel with a few small surface voids and one large surface void. Panel 5 — Fourth panel west of Trailwood Lane. "Moderate" to "Poor" panel with several small to medium surface voids and one large surface void. Panel 6 — Seventh panel west of Dobecka Drive. "Good" panel with only a few small surface voids. The proposed investigation was based on utilization of the NDT technique called Pulse Echo, in which a mechanically produced energy wave is transmitted downward through the pavement. A surface mounted transducer then measures the signals resulting from the reflection of the energy wave off of either the bottom surface of the pavement or the surfaces of internal discontinuities within the pavement, such as large voids or mud balls. These signals, which may be many at any given location, are recorded by computer and then are interpreted by a Fast Fourier Transform analyzer program. This program separates typical background signals from the more predominant signals indicative of the suspected internal anomalies. A second technique, ground penetrating radar, was also attempted, but it was determined that the Pulse Echo technique was more effective in this application. At some locations, a 2 ft x 2 ft grid was used and at others a 1 ft x 1 ft grid. As the NDT work progressed, locations of indicated anomalies were temporarily marked on the pavement. At some locations where a mud ball was indicated, a closer grid was used to more precisely define the location and extent of the mud ball. Upon completion of the Impact Echo tests, full depth cores were removed, by a coring company retained by Alpha Testing, at several locations where the Impact Echo tests reveal an internal discontinuity and from locations where no internal discontinuity was indicated. The purpose of these cores was to calibrate the NDT equipment and to verify the reliability of the test procedure. Additionally, the coring technician was instructed to select one random location in test panels 1, 2, 4, 5, and 6 and remove a core at those locations. The purpose of the random cores was to determine mud balls could or would be located by random core removal. 2 WJE ��E.cli ri l_C r� V \T I K I\ I� q I I )TN October 8, 2001 Executive Summary Investigation to Detect Mud Balls in Sandy Lake Road Pavement for Alpha Testing, Inc. As requested, Wiss, Janney, Elstner Associates, Inc. has completed the authorized initial phase of nondestructive testing at selected locations of the westbound lanes of Sandy Lake Road, Coppell, Texas. The purpose of the initial phase of this proposed nondestructive testing was to attempt to determine if mud balls, not visible at the surface of the pavement, exist deeper within the pavement, and if nondestructive testing (NDT) techniques are a viable method of detecting them. BACKGROUND AND SCOPE When extensive visible surface voids were noted on the recently constructed westbound lanes of Sandy Lake Road between MacArthur Boulevard and Denton Tap Road, a limited coring program was conducted. The cores, taken at the locations of both large and small visible surface voids, verified that the voids were due to large mud balls within the pavement concrete. In fact, at some instances the size of the mud ball was much larger than anticipated based on the size of the existing visible surface voids. Due to this, there was concern as to whether more large mud balls, not visible at the surface, were present in the pavement. As discussed in our 11 January 2001 proposal for this phase of the investigation, the detection of internal discontinuities in concrete is possible with various NDT techniques. For structural members, the use of Ultrasonic Pulse Velocity is commonplace when the concrete member can be accessed from two sides. Pavements, where only one -sided access is possible, require a different procedure, the Impact -Echo technique. When relatively small discontinuities are present, their detection is more difficult and requires that the impact -echo readings be made at a fairly close spacing. In fact, it must be noted that neither this method, nor any other that we are aware of, will detect very small subsurface mud balls. Attached to this Executive Summary is a WJE Capability Profile, describing the Impact -Echo technique and a WJE Project Profile describing how the Impact -Echo technique was used to locate internal discontinuities in taxiways at the Seattle - Tacoma Airport. ING IN[ ER> WJE i \RCI Ill - ELI1 N1;AI1MAIC )CIENTI�Tti DISCUSSION The Impact Echo technique was successful in locating several mud balls that were not visible at the surface. At nine of twelve locations for verification cores, the presence of large mud balls below the surface was confirmed. At three locations where there was an indication of a below - surface anomaly, no mud balls were noted on the core surface. Two of these were selected for vertical sectioning, and were cut into three vertical segments. One of these had a small (1/2 to 3/8 in.) mud ball approximately 1/2 in. below the surface. (It should be noted that these three core locations were in Panels 5 and 6, and the tests were conducted on Friday, 17 August 2001, during time periods between frequent intermittent rainfall. It is possible that the wet pavement may have adversely affected the operation of the pulse echo equipment.) At the six coring locations selected where there was no indication of a below- surface anomaly, no mud balls were noted on the core surfaces. Two of these were vertically sectioned, and no mud balls were detected in the sections. At the five randomly selected coring locations, no visible mud balls were noted on the core surfaces. Two of these were selected for vertical sectioning, and no mud balls were noted in the sections. Where detected most of the mud balls were quite large. At one location, the mud ball started about 1/2 to 3/4 in. below the pavement surface and extended full depth for the entire diameter of the core. There was no visible evidence of the existence of that mud ball at the surface of the pavement. CONCLUSIONS From a technical point of view, the results of the NDT program were judged to be successful in that the presence of mud balls not visible at the surface could be detected. Unfortunately, the tests, and confirmation cores, also show that many mud balls exist within the pavement cross - section, some of which are very large. However, it is our opinion that the use of this technique may not be cost - effective. Five cores at randomly selected locations did not reveal the presence of mud balls, thus indicating that the use of random coring locations is not a reliable method of detecting the presence of mud balls. RECOMMENDATIONS It is our opinion that performing Impact Echo tests at the close interval necessary to detect all (or most) of the significant sub - surface mud balls in this length of pavement would be cost - prohibitive. Thus, an alternative approach to this problem is suggested. It is possible that significant mud balls near the surface could be detected by some form of infrared equipment during certain times of the day, or during certain weather conditions. This procedure may also be cost - prohibitive. It is possible that large near- surface mud balls will absorb and retain moisture after a lengthy period of wet weather. Visible "wet spots" on the pavement surface following such a weather period would be LV(II,�I_Cl;i RBIIIIlk JT ,�1:AI LI�I:U���IC�ll�fti indicative of the presence of such mud balls near the surface. However, deeper mud balls would not be readily detectable by this technique. It is also our opinion that significant near - surface mud balls will eventually result in surface failure of the pavement at those locations. A periodic visual survey would allow detection and documentation of such occurrences. The scope of our work did not include observations or testing of the east bound lanes or various turning lanes. However, during initial main -line paving of the east bound lanes a few months after completion of the westbound lanes, we were requested to visit the project. At that time, we observed mud ball contamination in the coarse aggregate stockpile at the concrete batch plant. Consequently, we suspect that mud balls may also exist in the eastbound pavement lanes. Thus, at the least, it would be prudent to conduct a detailed visual survey of the eastbound lanes to determine if any surface voids, possibly attributable to mud ball contamination, are present. GA2000 PROP,3576.21Executive Summary 08 Oct 01.doc 4 Wiss, Janney, ElstnerAssociates, Inc. Capability Profile Impact -Echo Method Nondestructive Evaluation Method to Detect Internal Flaws in Concrete � 1 FFT ANALYZER f 3 \ SIGNAL TRANSDUCER SHEAR WAVE REFLECTED / WAVE IMPACT SOURCE LONGITUDINAL WAVE : a SURFACE WAVE DISCONTINUITY C CONCRETE MEDIUM Nondestructive evaluation (NDE) methods for the detection of defects in civil structures have recently been receiving increasing attention. In concrete structures, defects that appear on the surface can be visually observed. However, internal defects cannot be detected reliably with most available methods such as pulse velocity, radar and infrared thermography. Success has been particularly limited when both sides of a concrete element were not accessible. An ongoing research program has developed a technique called "Impact - Echo", which is based on transient stress wave propagation. The Impact -Echo Method can detect the size and location of significant concrete flaws such as honeycombing, debonding, delaminations, cracks (pla- nar or otherwise), mud pockets, and cold joints. Because impact echo only requires access to one concrete surface, it can be used to measure the thickness of concrete pavements and slabs -on- grade. It can also be used to verify grout continuity in post- tensioning tendon ducts and flaws in concrete piles and caissons. Principle of The Method The impact -echo is a nondestructive method for concrete evaluation that involves introducing mechanical energy, in the form of a short pulse, into a structure. A transducer mounted on the surface of the structure receives the reflected input waves or echoes from the discontinuities (flaws) within the material. By determining a propa- gation velocity, reflected waves can be analyzed with a Fast Fourier Transform (FFT) analyzer to determine internal characteristics of the concrete. Applications For Inspection and Analysis WJE has tested many structures such as large foundations for turbine /gen- erators, pumping stations and boilers; caissons and concrete piles; cooling towers; tank walls; pipes; and floor slabs, columns and beams in buildings and bridges. The method has been used to detect internal voids, cracks, freeze - thaw damage, ungrouted tendons and honeycombing in concrete. 901.8.93 Erlin, Hime Associates Project Profile Sea Tac Runway Improvements Petrographic Studies of Concrete A close -up view of sand particles is visible in the above photo. No cement paste was detected in the sand concentration, which is petrographically identical to the sand contained in the body of the concrete. Client SCI Engineers and Constructors A Division of Wiss, Janney, Elstner Associates, Inc. A concentration of sand contained com- pletely within the body of the core is visible in the center of the above photo. Location Seattle, Washington Impact -echo studies of taxiways at the Seattle- Tacoma Airport indicated the pres- ence of numerous defects in the concrete. A number of cores were extracted from the areas that contained defects. Most of the cores extracted from these areas broke into several fragments during removal. Examination of the samples suggested that the fragmentation may have been due to relatively large voids in the concrete. Some of these voids appeared to approxi- mate the diameter of the core. One of the submitted cores was largely intact but contained a smaller defect. Epoxy was injected into the defect and allowed to cure. The sample was then prepared for petrographic studies in the normal man- ner. The interior of the core was found to contain an intact concentration of sand. These studies suggested that the other cores contained similar but larger concen- trations of sand that had become dis- lodged and lost during the coring opera- tion. The sand contained in the concen- trations was petrographically similar to that in the concrete. This indicated that the sand concentrations were the result of incomplete mixing of the concrete 704.6.95 Se ,91Nha Testing Inc.; 972 241 5835• Oct -8 -01 4 :47PM; Page i 2209 Wiscons Suite 100 Dallas, Texas 75229 Ken of Fax hone: 972/304 -7041 RE: Executive Sutmn Mud Balls in San Lake Road Pavement Coppell, Texas ALPHA Prolect N1 00723 -1 Date: October 8, 2001 Number of pages including cover sheet: From: Jim L. Hillhouse, P.E. ALPHA TESTING, INC. 2209 Wisconsin, Suite 100 Dallas, Texas 75229 i Email jimhilthouse@alphatesting.com Phone: 972/620- 8011,_F„xt. 124 Fax phone: 9721241 -5835 or 972/406 -6023 I REMARKS: ❑ Urgent I ❑ For your review ❑ Reply ASAP ® Please comment :bed is a copy of the Executive S ary for the project referenced above. Due to extensive assignments by Wiss, Janney, .er Associates (our subconsWtant) New York City with the World Trade Center, preparation of the final report has been , ed. A more detailed report, which: ill include the backup data and more extensive photo - documentation of the pavement itions and cores, will be submitted the near future. your review of the information pr#ided in this Executive Summary, we would like to schedule a time to visit with you in office and address any questions y u might have. Also, we can discuss the plan of action from this point. be out of town for the remainder 4 this week, but would like to plan on visiting in your office on either, Wednesday or r of next. Please let me know whio day is best and what time you would be available. 3� 5� �.0-2.