1、CECW-ED W 3515789 00252Ll3 LOO DEPARTMENT OF THE ARMY US Army Corps of Engineers Washington, DC 20314-1000 Engineer Technical Letter NO. 1110-8-2 (FR) L-3 7-17 ETL 1110-8-2(FR) 28 June 1991 Engineering and Design ANCHOR EMBEDMENT IN HARDENED CONCRETE 1. Purpose This engineer technical letter (ETL) p
2、rovides guidance on materials and tech- niques for anchor embedment in hardened concrete. 2. Applicability This ETL applies to HQUSACE/OCE elements, major subordinate commands, dis- tricts, laboratories, and other field operating activities (FOA) having Civil Works activities. 3. References a. Avery
3、, T. 1989 (Feb). “Performance of Polyester Resin Grouted Rockbo- Its Installed Under Wet Conditions,“ The REMR Bulletin, Vol 6, No. 1, US Army Engineer Waterways Experiment Station, Vicksburg, MS. b. Best, J. F., and McDonald, J. E. 1990 (Jan). “Evaluation of Polyester Resin, Epoxy, and Cement Grout
4、s for Embedding Reinforcing Steel Bars in Hard- ened Concrete,“ Technical Report REMR-CS-23, US Army Engineer Waterways Exper- iment Station, Vicksburg, MS. c. Krysa, A. 1982 (Sep). “Experience and Problems in the Pittsburgh Dis- trict Installing Rock Anchors at Lock 3, Monongahela River,“ Concrete
5、Struc- tures: Repair and Rehabilitation, Vol C-82-1, US Army Engineer Waterways Ex- periment Station, Vicksburg, MS. d. McDonald, J. E. 1980 (Apr). “Maintenance and Preservation of Concrete Structures; Report 2, Repair of Erosion-Damaged Structures,“ Technical Report C-78-4, US Army Engineer Waterwa
6、ys Experiment Station, Vicksburg, MS. e. McDonald, J. E. 1989 (Feb). “Evaluation of Vinylester Resin for An- chor Embedment in Concrete,“ Technical Report REMR-CS-20, US Army Engineer Waterways Experiment Station, Vicksburg, MS. f. McDonald, J. E. 1990 (Oct). “Anchor Embedment in Hardened Concrete U
7、nder Submerged Conditions,“ Technical Report REMR-CS-33, US Army Engineer Waterways Experiment Station, Vicksburg, MS. 4. Background Rehabilitation of hydraulic structures usually requires removal of deteriorat- ed concrete and replacement with new ee Supersedes ETL 1110-8-2(FR) dated 15 February 19
8、91. Steps 1 and 2 of Figure 1 of the 15 February 1991 ETL were interchanged. 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-= 3535789 0025244 047 concrete. Steel dowels are normally used to anchor the replacement material to the existing concrete.
9、 Typically, anchors are installed by (a) drilling a small-diameter hole into the remaining sound concrete, (b) cleaning the hole, (c) inserting a capsule containing either polyester resin or vinylester resin, and (d) spinning the anchor into the hole. Early-age field pullout tests on anchors install
10、ed in this manner under dry conditions indicate this to be a satisfactory procedure. polyester-resin grout under wet conditions have been reported (“Experience and Problems in the Pittsburgh District Installing Rock Anchors at Lock 3, Monong- ahela River,“ Concrete Structures: Repair and Rehabilitat
11、ion; “Maintenance and Preservation of Concrete Structures; Report 2, Repair of Erosion-Damaged Structures“). Consequently, a study was initiated as part of the Repair, Evaluation, Maintenance, and Rehabilitation (REMR) Research Program to evalu- ate the effectiveness of selected grout systems for em
12、bedment of anchors in concrete. However, a number of failures of anchors embedded in 5. REMR Research Findings a. The effectiveness of neat portland-cement grout, epoxy resin, and pre- packaged polyester resin in embedding anchors in hardened concrete was evalu- ated under a variety of wet and dry i
13、nstallation and curing conditions (“Eval- uation of Polyester Resin, Epoxy, and Cement Grouts for Embedding Reinforcing Steel Bars in Hardened Concrete“). Pullout test specimens consisted of 6- by 18-in. concrete cylinders into which 3/4-in.-diam reinforcing bars were embed- ded to a depth of 15 in.
14、 in nominal l-1/8-in.-diam percussion drilled holes. Pullout tests were conducted at eight different ages ranging from 1 day to 32 months. Beyond 1 day, all pullout strengths were approximately equal to the ultimate strength of the reinforcing-bar anchor when the anchors were in- stalled under dry c
15、onditions, regardless of the type of embedment material or curing conditions. resin under submerged conditions, pullout strengths were essentially equal to the ultimate strength of the anchor when the anchors were installed under wet or submerged conditions. The overall average pullout strength of a
16、nchors embedded in polyester resin under submerged conditions was 35 percent less than the strength of similar anchors installed and cured under dry conditions. The largest reductions in pullout strength, approximately 50 percent, occurred at ages of 6 and 16 months. Also, the overall average pullou
17、t strength of anchors embedded in polyester resin under submerged conditions was approxi- mately one-third less than the strength of anchors embedded in epoxy resin and portland-cement grout under wet and submerged conditions, respectively, and cured under submerged conditions. Although the epoxy re
18、sin performed well in these tests when placed in wet holes, it should be noted that the manufacturer does not recommend placement under submerged conditions. With the exception of the anchors embedded in polyester b. Creep tests were conducted by subjecting pullout specimens to a sus- tained load of
19、 60 percent of the anchor-yield strength and periodically mea- suring anchor slippage at the end of the specimen opposite the loaded end. After 6 months under load, anchors embedded in portland-cement grout and epoxy resin, that were installed and tested under dry conditions, exhibited very low anch
20、or slippage, averaging 0,0013 and 0.0008 in., respectively. Under similar conditions, slippage of anchors embedded in polyester resin was approximately 30 times higher. under wet conditions followed a similar trend. The average slippage for an- chors embedded in portland-cement grout and epoxy resin
21、 was 0.0028 and 0.0033 in., respectively, or two to four times higher than results under dry condi- tions. Anchors embedded in polyester resin, installed and cured under sub- merged conditions, exhibited significant slippage; in fact, in one case the anchor pulled completely out of the concrete afte
22、r 14 days under load. 6 months under load, the two remaining specimens exhibited an average anchor slippage of 0.0822 in., approximately 30 times higher than anchors embedded in portland-cement grout under the same conditions. Results of creep tests on specimens fabricated and tested After 260 7 c.
23、Long-term durability of the embedment materials was evaluated by peri- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-W 3515787 0025245 T83 odic compressive strength tests on 2-in. cubes stored both submerged and in laboratory air. ter-resin and epo
24、xy-resin specimens stored in water was 37 and 26 percent less, respectively, than that of companion specimens stored in air. The strength of portland-cement grout cubes stored in water averaged 5 percent higher than that of companion specimens stored in air during the same period. After 32 months, t
25、he average compressive strength of polyes- d. A 1987 review of available manufacturers literature on concrete anchor grouting systems revealed that a vinylester resin, prepackaged in glass cap- sules, was being promoted for use under submerged conditions. According to the manufacturers representativ
26、es, the performance of anchors embedded in vinylester resin under submerged conditions was similar to that of comparable anchors installed in the dry. Since no test data were furnished to substanti- ate this claim, the US Army Engineer District, New Orleans, initiated testing 2 Provided by IHSNot fo
27、r ResaleNo reproduction or networking permitted without license from IHS-,-,-3515789 002524b 9LT m by the US Army Engineer Waterways Experiment Station (WES) to evaluate the performance of anchors embedded in vinylester resin under dry and submerged conditions (“Evaluation of Vinylester Resin for An
28、chor Embedment in Concrete“ ) . e. Anchors were 1-1/4-in.-diam threaded rods installed in holes drilled to depths of 12 and 15 in. with a 1-1/2-in.-outside-diameter core barrel. Pull- out tests were conducted at four different ages ranging from 1 to 28 days. Results of pull-out tests on anchors inst
29、alled in dry holes (15-in. embedment length) were remarkably consistent with an overall average tensile capacity of 105 kips at 0.1-in. displacement and an average ultimate load of approximately 125 kips. This load is near the yield load of the anchors. In comparison, results of pullout tests on anc
30、hors installed under submerged conditions were relatively erratic, with an overall tensile capacity of 36 kips at 0.1-in. displacement and an average ultimate load of 48 kips. Obviously, the tensile load capacity of anchors embedded in concrete with vinylester-resin capsules is significantly reduced
31、 when the anchors are installed under submerged condi- tions. At a displacement of 0.1 in., the tensile capacity of anchors embedded under submerged conditions was approximately one-third that of similar anchors embedded in dry holes. f. The reduced tensile capacity of anchors embedded in concrete u
32、nder sub- merged conditions with prepackaged polyester-resin and vinylester-resin car- tridges is primarily attributed to the anchor installation procedure. Resin extruded from dry holes during anchor installation was very cohesive, and a significant effort was required to obtain the full embedment
33、depth. In com- parison, anchor installation required significantly less effort under submer- ged conditions. Also, the extruded resin was much more fluid under wet condi- tions, and the creamy color contrasted with the black resin extruded under dry conditions. Although insertion of the adhesive cap
34、sule or cartridge into the drill hole displaces the majority of the water in the hole, water will remain between the walls of the adhesive container and the drill hole. Insertion of the anchor traps this water in the drill hole and causes it to become mixed with the adhesive, resulting in an anchor
35、with reduced tensile capacity. g. These findings generated concern in the geotechnical community regard- ing the ultimate performance of rock bolts previously installed under similar conditions. Because of this concern, the Geotechnical Laboratory at WES con- tracted with the US Bureau of Mines, Den
36、ver Research Center, to determine what effect water present during installation would have on longer anchors instal- led with polyester resin. Anchors were headed bolts (No. 6, Grade 60 steel) with embedment lengths ranging from 17 to 38 in. Anchor holes were drilled in concrete blocks with a masonr
37、y diamond-core bit that had a nominal 1-in. out- side diam. Pullout tests were conducted on anchors installed under “dry, damp, displaced, and submerged“ conditions. As a result of these tests, Avery (“Performance of Polyester Resin Grouted Rockbolts Installed Under Wet Condi- tions“) concluded that
38、 in a submerged borehole, water appears to affect the resin by mixing with the top 12 to 14 in. to form an emulsion which may be too dilute to catalyze effectively. He also concluded that water is detrimental to the successful curing of polyester resins only in situations involving very short anchor
39、s (less than 2 ft). To solve this problem, Avery recommended drilling the anchor hole 1 ft deeper than desired and adding an additional cartridge of resin. h. In subsequent tests on anchors embedded in vinylester under submerged conditions, McDonald “Anchor Embedment in Hardened Concrete Under Subme
40、rged Conditions,“ found that increasing the embedment length from 12 to 24 in. resulted in a 60-percent increase in tensile capacity at 0.1-in. displacement. However, this increased tensile capacity of anchors installed under submerged conditions was still only about one-half the load capacity of an
41、chors with 12- in. embedment lengths installed in dry holes. While it may be possible to improve anchor performance under submerged conditions by further increasing embedment lengths, significant additional material and labor costs are associ- ated with increasing embedment lengths of anchors in con
42、crete. Therefore, the 2609 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3535789 0025247 856 development of improved anchor installation procedures which do not require excessive embedment lengths was necessary. i. An anchor installation procedure
43、that eliminates the problem of resin and water mixing in the drill hole is described by McDonald “Anchor Embedment in Hardened Concrete Under Submerged Conditions.“ procedure (Figure l), a small volume of adhesive was injected into the bottom of the drill hole in bulk form prior to insertion of the
44、adhesive capsule. This injection was easily accomplished with recently developed paired plastic cartridges (Figure 2) which contained the vinylester resin and a hardener. The In the revised installation 3 Z6O Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I
45、HS-,-,-D 3535789 0025248 792 D - a- =Er- = Lml I *. . . .*&.-. 4. ,: a Skpl b. Slap2 Figure 1. Revised Inchor inataiinlim procedure Figure 2: Paired plastic cartridges and static mixing tube. PHOTO NOT INCLUDED. 4 2611 Provided by IHSNot for ResaleNo reproduction or networking permitted without lice
46、nse from IHS-,-,-W 3515789 0025249 b2 = cartridges were inserted into a tool similar to a caulking gun which automati- cally dispensed the proper material proportions through a static mixing tube directly into the drill hole. Once the injection was completed, insertion of a prepackaged vinylester-re
47、sin capsule displaced the remainder of the water in the drill hole prior to anchor insertion and spinning. j. Anchors with 15-in. embedment lengths and installed with the revised procedure exhibited essentially the same tensile capacity under dry and sub- merged conditions. At 0.1-in. displacement,
48、the tensile capacity of vertical anchors installed with the revised procedure under submerged conditions aver- aged more than three times greater than that of similar anchors installed with the original procedure. Also, the ultimate tensile capacity of anchors in- stalled under submerged conditions
49、with the revised procedure averaged more than 130 kips compared to an average ultimate capacity of less than 50 kips for similar anchors installed with the original procedure. k. Horizontal anchors installed with the revised procedure under both dry and submerged conditions also exhibited excellent tensile load capacities. Overall, the difference in tensile capacity between horizontal anchor
