Bridge Inspections For A Safer Infrastructure
Testing Concrete Crack WidthsMay 18th, 2016 Author: Doug Thaler
Reinforced concrete in all types of construction has one element in common across the board and that is the certainty that there will be cracks that need to
be checked over time. Concrete cracking occurs for many reasons including settlement cracking, drying shrinkage,weathering, thermal stress, corrosion of reinforcement, poor construction practices, errors in design and detailing, construction overloads and externally applied load cracking to name a few.
Whatever the reason an NDE (Non destructive evaluation) utilizing NDT (Non destructive testing) methodologies would be best to employ on a regularly scheduled basis in order to assess the severity of the cracking and take steps to make early repairs to ensure the health of the concrete going forward.
For our purposes Infrastructure Preservation Corporation (IPC) is tasked with testing concrete cracks in critical infrastructures
like Bridges, Roadways and Dams. These are mission critical components of our everyday lives and economy and need to be thoroughly tested and assessed in order to keep the public safe and to extend the life of our critical infrastructure assets in order to preserve state and federal funds and to better manage our infrastructure assets on an ongoing basis.
To this end, IPC has developed a highly sophisticated means of testing crack widths, crack lengths and the crack position on concrete that is less subjective and over 100 times more accurate than conventional manual methods.
Concrete cracks themselves can be classified based on 4 factors: 1:) Crack Length, 2:) Crack Width, 3:) Crack position on an asset, 4:) Crack depth-which typically relates to the width. The types of concrete cracking that are of most concern are structural cracking and Load Bearing Cracking.
Structural cracking is almost always due to corrosion of the reinforcing steel, void formations, delamination, air and water intrusion. The can be a result of inadequate reinforcement cover, delamination of the concrete or the rebar being exposed to air or water due to other cracks, age or changes in the load that the bridge or structure was designed to hold.
Load bearing cracks result from a bridge or roadway load changing over time. Structures not built to carry additional loads will cause structural cracking. As new housing goes up and traffic increases, bridge loads that once only carries a small amount of traffic are all of a sudden stressed trying to carry heavier loads. This can cause load bearing cracks. All cracking exposes the concrete and rebar reinforcement to air and water which further compromise the structure over time.
The importance of concrete testing especially for Bridge Inspections becomes more apparent over time. By recording all of the concrete cracks widths and lengths on a bridge for example, we have a basis for future tests. Future test results can be overlaid to see the crack progression over time. Cracks that are increasing in length and width over time can be better monitored and assessed to scheduled needed repairs before those areas become a cause for concern
One of the only methods available today to conduct proper concrete crack width testing and concrete crack inspections is with IPC’s concrete crack testing system. IPC’s concrete crack testing is able to test for crack widths of .003 from over 100 feet away. The advantage of this is that the old way of testing bridges, having the department of transportation close the roadways, the asset manager hire boom trucks that lift an inspector up to manually search the concrete for cracks is no longer necessary. IPC can conduct a concrete crack testing or assessment of a concrete asset including crack widths, crack length and position on the asset from hundreds of feet away, without lane closures. This saves both the asset manager and the D.O.T. both time and money while increasing the accuracy of the crack inspection
Once the crack assessment is complete an asset manager can make the required repairs to the concrete early enough to seal the intrusion of air and water. Further decay is postponed, the asset life is extended and public safety is improved.
For more information contact Doug Thaler at [email protected]