Our specialist Rope Access surveyors were tasked to undertake an assessment to Newton Road Bridge which spans the Tame Valley in Sandwell.
The Bridge Piers had recently had Cathodic Protection installed to prevent further corrosion of steel reinforcement by harmful chloride ions.
Our Tasks were primarily to undertake a Delamination survey which consisted of a hammer tap test and hammer drag to determine hollow sounding areas where there is potential for delamination. A defect survey was also carried out by our Team of x2 IRATA Level 3’s and a Level 1 technician.
Prior to any works being undertaken, we had to carry out a pull out test to over 300 existing eyebolts. A Hydrajaws Model 2000 pull tester was used to pull test the eyebolts to 6Kn in order for our Team to safely carry out the works.
How does Delamination happen?
When fresh concrete is placed and compacted, the solids (cement and aggregate) settle.
This natural settlement causes excess mix water and entrapped air to be displaced (called bleeding), and the lighter materials migrate toward the surface.
If finishing operations start prematurely and close or seal the surface before bleeding is completed, air and/or water are trapped under the densified surface mortar.
As concrete hardens, subsurface voids develop where the water or air is trapped.
These voids create weakened zones right below the surface that can eventually detach and spall. Very thin mortar layers over delamination may even detach when tapped with a hammer as you try to sound out the extent of the delaminated area.
During this survey, minimal hollow areas and defects were found, the inspection works have now been put on an annual schedule.
