1. Overhead installation of bonded anchors
Report on activities of ACI 355 TG 5 “Overhead installation methods of bonded anchors”
Rolf Eligehausen
Meeting of ACI 355 on Oct. 23, 2016

2. Overhead installation of bonded anchors
The Task Group was formed by ACI 355 during the meeting in April 2016
TG Chairman: R. Eligehausen
TG Membership: J. Dorst , W. Fuchs , A. Hoermann-Gast , A. Kolczak , J. Olsen J. Pearson, P. Schillinger, H. Silverman, J. Silva, C. La Vine, N. Westin
Webex meeting on October 14, 2016
11 participants
Main topics discussed
Mission and goal
Evaluation of effectiveness of different methods to install bonded anchors overhead
Modifications to ACI test procedures and assessment criteria
- Review of the ACI/CRSI Adhesive Anchor Installer certification
program

3. Overhead installation of bonded anchors
Mission and goal as published on the ACI web site
TG Mission: Review qualification methods for overhead installation considering concerns about repeatability of the end cap method for providing acceptable installations in actual use
TG Goal: Make recommendations to the main committee for revisions to overhead qualification methods to insure repeatability of actual field installations

4. Overhead installation of bonded anchors
Modifications proposed by TG 5
Mission: Review qualification methods for overhead installation considering concerns about repeatability of the end cap method different installation methods for providing acceptable installations in actual use.
Goal: Make recommendations to the main committee for revisions improvements to overhead* qualification methods to insure repeatability of actual field acceptable installations under field conditions.
*overhead = horizontal and upwardly inclined
Furthermore it was proposed to review the ACI/CRSI Adhesive Anchor Installer (AAI) certification program.

5. Overhead installation of bonded anchors
The effectiveness of the end cap-cap and piston plug methods for installing bonded anchors overhead was discussed based on the paper by J. Silva in Concrete International, July 2016
“Overhead installation of Injection-Type Adhesive Anchors”
The results of the performed tests showed, that installations with a piston plug were performed without significant voids in the adhesive (0-2%) because of back pressure created during injection which drives the piston plug with tube automatically out of the hole.
Because such pressure is not created with the end cap method, for the tested hole diameter and embedment depths injections without significant voids (>10%) were rarely (d0 = 7/8 in.) or not achieved at all ((d0 = 1 3/8 in.)
Based on the results of the performed tests and additional
considerations John Silva proposed to exclude the assessment of
overhead installations with the end- cap method from ACI and
to allow overhead installations with back pressure devices only. He
proposed the following modification to ACI 355.4, 3.2 -

6. Overhead installation of bonded anchors
The members of the TG were split on this topic. A straw poll showed, that 5 participants agreed with the proposal, while 5 did not accept it. They argued that not acceptance of an injection method should be based on the results of the required tests only. 1 participant was undecided.
The final decision on this topic was postponed until the discussion of the
modification of the test procedure and assessment criteria.

7. Overhead installation of bonded anchors
The discussion of modifications to the test procedures and assessment criteria was based on a power point presentation of Eligehausen/Asmus.
It is partly repeated here with inclusion of the results of the discussion of TG 5

8. Overhead installation of bonded anchors
Purpose—These optional reliability tests are performed to evaluate the performance of adhesive anchors installed horizontally and overhead, that is, vertically up.
General test conditions—Perform confined tension tests in uncracked concrete. Conduct tests on all-thread anchors that have been installed in accordance with the MPII.
Perform separate test series with anchors installed horizontally and overhead. Perform tension tests to failure with continuous measurement of load and displacement. Install and cure anchors at the minimum and maximum installation temperatures for concrete and adhesive included in the MPII for downhole installation. Perform tension tests at standard temperature.
The value of req for the tension capacity shall be 0.90.
ACI : Pullout tests

9. ACI 355.4-11: Pullout tests – discussion (1)
Overhead installation of bonded anchors
It is not stated if the anchor installation should be performed according to Fig. 4.3 with stacked blocks or not.
Tests should be performed with stacked blocks arranged overhead to ensure bond failure. Add the following tests to
Conduct tests on all-thread anchors that have been installed in accordance with the MPII using stacked blocks arranged overhead (compare and Fig. 4.3).
Some members of TG 5 argued, that this modification is not needed, because it is already covered in Section 4.7.
This will be checked until the next meeting of TG 5 in December 2016
ACI : Pullout tests – discussion (1)

10. ACI 355.4-11: Pullout tests - discussion (2)
Overhead installation of bonded anchors
To avoid anchor steel failure, the embedment depth of the inserted threaded rod is usually reduced to hef  6do to 8do. With this embedment depth it may be easier to force air out of the hole that may be entrapped during adhesive injection than at maximum embedment depth. Therefore the worst case is not tested.
To take this into account, it is proposed to increase req to req = 0.95 or statistical equivalence should be shown between the bond strength valid for downhole and overhead installations.
Modify as follows:
The value of req for the tension capacity shall be or statistical equivalence between the bond strength valid for downhole and overhead applications shall be demonstrated.
TG 5 was of the opinion, that statistical equivalence should be demonstrated.
ACI : Pullout tests - discussion (2)

11. ACI 355.4-11: Installation tests (1)
Overhead installation of bonded anchors
Anchor installation used for testing shall be reviewed for effectiveness. A procedure for verifying the effectiveness of overhead installation procedures using blind injection into a clear tube of equivalent diameter and length is shown in Fig The procedure used shall enable the evaluation of the installation procedure as described in
Fig. 7.3—Procedure to verify effectiveness of adhesive injection method
ACI : Installation tests (1)

12. ACI 355.4-11: Installation tests (2)
Overhead installation of bonded anchors
When installed horizontally and overhead in accordance with the MPII, the annular gap around the anchor element shall remain completely filled with adhesive and the anchor element shall not displace downward more than da /20 or 0.1 in. during the cure time. Include the following criteria in the assessment:
1. The adequacy of the MPII for the installation orientation being evaluated.
2. For overhead installations, the adequacy of measures, as required, to prevent sag of the anchor element prior to adhesive cure (Fig. 10.2(a)).
3. For overhead and horizontal installations, the adequacy of measures, as required, to capture excess adhesive during installation of the anchor element, to protect the unbonded portion of the anchor element from adhesive, and to ensure that the annular gap around the anchor element is completely filled with adhesive over the bonded length (Fig. 10.2(b) and (c)).
4. The adequacy of installation procedures to prevent formation of gaps and/or trapped air in the adhesive along bonded length of the anchor (Fig. 10.2(d)).
ACI : Installation tests (2)

13. ACI 355.4-11: Installation tests - discussion (1)
Overhead installation of bonded anchors
a) According to in combination with a threaded rod must be inserted into the acrylic tube.
To ensure the same condition in the tube tests as in applications in concrete, an air-tight seal is required at the upper end of the tube. The air-tightness should be verified for 6 bar (≈90 psi) under water.
Accepted by TG 5, however the requirement should be put on the commentary side with more explanatory text.
ACI : Installation tests - discussion (1)

14. ACI 355.4-11: Installation tests - discussion (2)
Overhead installation of bonded anchors
According to the annular gap around the anchor element shall remain completely filled with mortar. According to AC308 voids with a total area of 10% of the bond surface are allowed. This value is much too liberal because:
b1) Injection tests have shown that if no voids are observed from the outside of the tube, the sectioned area may contain up to about 20% of voids because a thin layer of mortar may be applied at the inner side of the tube during injection, which mask voids in the adhesive. Therefore, if a void area of 10% is observed from the outside, the area of voids in the adhesive may be much larger.
b2) Voids in the adhesive will negatively influence the creep behavior of bonded anchors
b3) The results of the installation tests are valid for bonded anchors and post-installed reinforcing bars. In case of post-installed reinforcing bars, the adhesive must ensure the corrosion protection of the bar. If the adhesive contains a significant amount of voids, corrosion of the reinforcement must be expected, which is not acceptable.
ACI : Installation tests - discussion (2)

15. Overhead installation of bonded anchors
For these reasons, the requirement in ACI (no voids in the adhesive) should be maintained. However, to account for scatter of test results, a tolerance value (e.g. 1% voids) might be given.
TG 5 agreed, that after insertion of the rod no voids should be in the adhesive. The question of a tolerance limit will be discussed again.
ACI : Installation tests - discussion (2)

16. ACI 355.4-11: Installation tests - discussion (3)
Overhead Installation of bonded anchors
c) Insertion of a rod into a hermitically sealed tube may cause explosive ejection of air and adhesive. This may be dangerous to the installer. Therefore it should not occur.
The requirement, that explosive ejection of adhesive during rod insertion is not allowed, should be added in Section with a corresponding sketch in Fig
Accepted by TG 5
ACI : Installation tests - discussion (3)

17. ACI 355.4-11: Installation tests – discusssion (4)
Overhead Installation of bonded anchors
d) Blind injection tests with acrylic tubes where voids are not installed are very effective for revealing hidden voids. The tube should be filled 2/3 with mortar (as required by most MPIIs) and the area of voids should be measured on saw-cut sections. It may also be possible to evaluate the amount of voids by weighing the tube with mortar.
Blind injection tests without rod insertion should be added to ACI as section
Accepted by TG 5
ACI : Installation tests – discusssion (4)

18. ACI 355.4-11: Installation tests – discussion (5)
Overhead installation of bonded anchors
e) Currently, no tests are available to evaluate the allowable amount of voids in the adhesive after injection which ensures, that after rod insertion the annular gap around the anchor is completely filled with adhesive. According to the ACI/CRSI Adhesive Anchor Installer Certification Program a total area of voids AV ≤
 k1 ∙ d1 ∙ l
(1)
with Av =
total area of voids in the sectioned adhesive k1
0.1 di
inner diameter of clear tube l
length of clear tube required to be filled with adhesive
is allowed. This condition seams much too liberal to ensure a void free mortar after rod insertion.
It is proposed to reduce the allowable area of voids in the sectioned adhesive to 5% (k1=0,05 in Eq. (1)). Then the probability that the adhesive may contain voids is significantly reduced.
This topic will be discussed further.
ACI : Installation tests – discussion (5)

19. ACI 355.4-11: Installation tests – discussion (6)
Overhead installation of bonded anchors
f) In injection tests the area of voids in the adhesive may significantly depend on the temperature of the adhesive.
It is proposed, to perform injection tests with mortar at room temperature as well as at minimum and maximum installation temperature.
TG 5 accepted to perform tests at minimum and maximum installation temperature. If tests are needed also at room temperature will be discussed after reviewing the results of injection tests with the end cap method.
ACI : Installation tests – discussion (6)

20. ACI 355.4-11: Assessment criteria
Overhead installation of bonded anchors
It should be clarified in that in all tests the requirements must be met: - pullout tests - installation tests in clear tubes with rod insertion injection tests without rod insertion to recognize a bonded anchor system for overhead installation. Accepted by TG 5.
ACI : Assessment criteria

21. Overhead installation of bonded anchors
a) Pullout tests according to (modified) b) Installation tests with rod insertion according to (modified) c) Injection tests without rod insertion according to new section
Tests according to a) shall be performed with the largest diameter and embedment depth for which recognition is sought.
Tests according to b) and c) shall be performed for each combination of adhesive and delivery system sought for recognition, including accessories for installation.
Test according to b) shall be performed with the largest anchor element diameter and embedment depth
Tests according to c) shall be performed with all hole diameters associated with the range of anchor element diameters and maximum embedment depth sought for recognition.
Accepted by TG 5. It was not discussed, if for installation methods using a back pressure device the test program may be reduced.
Proposed tests to verify effectiveness of procedures given in the MPII for overhead installations

22. ACI 355.4-11: Assessment criteria
Overhead installation of bonded anchors
The ACI/CRSI Adhesive Anchor Installer certification program was briefly discussed. The following remarks were made. No decisions were taken. - For overhead installations either the maximum diameter should be tested (1 1/4 in.) or the certification should be limited to the tested diameter (3/4 in.). - At least 3 (better 5) injections should be required. All injections must be successful. - Injection tests should be performed at low and high installation temperature and not only at room temperature.
ACI : Assessment criteria

23. Overhead installation of bonded anchors
Next webex-meeting will be in December Detailed text proposals will be worked out until this meeting.
Goal: Present recommendations to ACI 355 at the meeting in Spring 2017

24. Overhead installation of bonded anchors
Define piston plug by its intended mechanism. Furthermore a geometrical condi-tion should be given (Eq. (2)). d =
di ∙ dp
(2)
with di
inner diameter of acrylic tube or nominal hole diameter dp
outer diameter of piston plug
The value d according to Eq. (2) for the smaller diameter should be equal to the value valid for the largest diameter. Than the tests a) to c) should only be performed with anchors with the largest diameter and maximum embedment for which recognition is sought. The tests according to b) and c) shall be performed for each combination of adhesive and delivery system sought for recognition including accessories for installation, including piston plugs, extension tubes etc.
Proposed tests to verify effectiveness of procedures given in the MPII for overhead installations with well defined piston plugs