Bridge Inspections For A Safer Infrastructure
Concrete Crack Testing & Crack TypesJune 1st, 2016 Author: Doug Thaler
There are a variety of types of cracks in concrete and as many causes for those cracks. Some of those cracks are merely settling and curing cracks and if there is no progression in those cracks over time, may not be harmful to the structure. Other cracks or cracks increasing in size over time can become serious health issues to the asset and the sooner they are discovered, monitored and tended to the better.
TYPES OF CRACKS IN CONCRETE AND TYPICAL CAUSES
Cracks can be broadly classified as either active or dormant.
If cracks are active, they may show movement in either direction, the width or depth over a certain period of time. If the cracks do not change over time much or remain completely unchanged, they may not pose any danger. If any crack is left untented to and not repaired they provide channels for moisture and air to enter which can lead to damage in the future. We all know that water and air are corrosive and can accelerate an assets decay.
The main 3 factors that concrete cracks tend to be classified are : 1) The direction of the crack, 2) The width of the crack, and 3) The depth of the crack. The crack may run along a longitudinal plane, transverse, vertical, on a diagonal plane or randomly zigzagging. Cracks will range in size from .001inches, very small, to .005 where we should start to monitor a cracks progression and even larger where cracks should be immediately tended to .
A brief description of various types of cracks are typically named as follows:
1. Settlement Cracking – Settlement cracking is typically caused by local restraining of the unhardened concrete around reinforcement such as rebar or some other type of obstruction.
2. D Cracking. – A type of cracking that is fine in nature and typically has numerous fine cracks occurring in a progressive pattern.
3. Pattern Cracking – Pattern Cracking are fine openings that occur in a regular pattern and is due to inconsistent volume of concrete. Typically with a lower concrete volume towards the surface.
4. Structural Cracking – Typically a result of corrosion of the reinforcing steel or structure being overstressed from outside forces. This includes Rust Cracking which is caused by inadequate reinforcement cover or other types of cracks that are left untreated. Air and water intrusion speeds the advancement of rust and corrosion.
5. Shrinkage Cracking – This type of crack only occurs in unhardened concrete. It is usually a crack that forms in a straight line that runs parallel with the floor.
6. Tension Cracking – Tension cracks form in reinforced concrete. Caused by elongation of the reinforcement in tension areas. Most common around the columns and in flat slabs and on beam soffits near the middle of a span.
7. Thermally Induced – Cracks caused by changes in temperature.
8. Plastic Cracking – This is visualized by diagonal lines in the top of a slab. It is often caused by rapid drying of the surface due to improper or delays in applying a curing membrane.
There are numerous other types of cracks, too numerous to go into here but in every case early detection can help extend the life and safety of the concrete structure. IPC’s concrete crack testing system was developed just for that purpose. IPC can locate cracks from 1000 feet with no lane closures or boom trucks. They can map the cracks with an X,Y and Z axis and show progression over time with future inspections. This will not only save time and money but advances the inspection of concrete structures to be 12-40% more accurate than current methods. See the video below for more information.
IPC is a non destructive testing (NDT) company that conducts (NDE) (Non Destructive Evaluations) of concrete and steel structures that are vital to our nations infrastructure.
Find out more at www.infrastructurepc.com..