6.12 Corrosion protection testing for permanent anchors with system tests
All corrosion protection systems shall have been subjected to at least one system test to verify the competence of the system. The results of all tests shall be documented.
The type of system test carried out for each anchor system shall be approved, in accordance with the principles stated herein, by the Client's Technical Representative who shall assess the documented results of the corrosion protection system tests in order to verify that the protection offered by each barrier in the system has been achieved.
The loading sequence shall comply with one of the three types of suitability tests in clause 9.
The confinement conditions in the test bond length shall simulate those encountered in the ground, be it rock or soil.
NOTE Either in situ tests or simulated laboratory tests are performed. Laboratory tests may include uniform stressing of encapsulated tendons as well as simulating the load transfer in the bond length.
Where an in situ test is undertaken the installation procedure shall simulate the procedure used with production anchors.
After loading the test anchors shall be uncovered with care in order to observe the effect of the stressed condition on the corrosion protection system.
The following properties of the corrosion protection system shall be assessed by inspection or measurement, - where appropriate:
- wall thickness and integrity of plastic ducts;
- integrity of joints and seals;
- grout cover and performance of spacers and centralizers;
- location and spacing of cracks in the cement grout where it serves as a corrosion protection barrier;
- degree of filling of grout, resin and corrosion protection compound in ducts and volumes of containment;
- damage to coatings;
- degree of bond or debonding along interfaces;
- dislocation of components during installation and loading.
It should be noted that in certain systems the integrity of the inner protective barrier depends on the maintenance of the integrity of the outer barrier.
Where plastic duct(s) are used as a protection barrier in the bond length of a permanent anchor the system test should demonstrate the integrity of the pregrouted encapsulation. The test should simulate the loading condition by preloading in an environment which approximates the ground conditions. The inspection of the plastic after the loading should prove that protection has not been impaired. A single documented test for a tendon arrangement in each particular duct size is sufficient in the simulated load condition. (An example of a test is described in annex B.)
Where a single plastic duct protection is supplemented by a crack controlled grout a system test should establish the crack spacing (in terms of cracks per metre) within the encapsulation. From the elastic properties of the tendon and the observed spacing of the cracks it should be shown that the crack width does not exceed 0,1 mm under service loading in the test undertaken. The inspection of the plastic after the loading should prove that protection has not been impaired. A single documented test for a tendon arrangement in each particular duct size should be sufficient in the simulated load condition (an example of such a test is described in annex B).
Where a single 3 mm thick steel or corrugated plastic tube-a-manchette duct is supplemented by a crack controlled grout and a minimum external grout cover of 20 mm, a system test should establish the crack spacing (in terms of cracks per metre) within the encapsulation. From the elastic properties of the tendon and the observed spacing of the cracks it should be shown that the crack width does not exceed 0,2 mm under service loading in the test undertaken. A single documented test for a tendon arrangement in each particular duct size should be sufficient in the simulated load condition.
