Almost all construction projects use concrete as a primary component from the foundation up and has been this way for a long time except for a few exceptions.
fischer receives many design and load calculation requests every day for anchor fixings with concrete as the base material, but most of the time it isn’t mentioned if the request is for cracked or non-cracked concrete, in which case it is typically assumed as cracked.
But this is a very crucial piece of information when proposing an anchor fixing solution or performing design calculations to ensure compliance of a certain fixing solution.
Now…. why is it so important and what is the difference between cracked and non-cracked concrete you ask?
Concrete in general is very brittle and can fall apart easily under stress. To make it more durable, steel bars known as “rebars” are commonly used to reinforce the concrete to handle the various stresses through the duration of its life.
Cracks are formed when the tensile stresses exceed the tensile strength of the concrete, simply put where there is stress or load; it becomes inevitable for concrete to develop cracks.
General causes for concrete to crack can occur due to a variety of reasons with the most common being thermal expansion and contraction and day to day service loads leading to more cracks.
These cracks are not large and are quite normal, typically categorized as hairline cracks considered no thicker than 0.3 mm under normal conditions and 0.5 mm under seismic conditions.
You may think these cracks are tiny and insignificant, but they matter when it comes to fixing. For example, when installing an anchor that is approved only for non-cracked concrete ETA (Options 7 – 12) in cracked concrete, the load bearing capacity of the anchor drops significantly due to the expansion caused by cracks.
These cracks that are formed over the course of its life expand and contract under random conditions which in turn directly affect the efficiency of the anchor used.
When it comes to non-cracked concrete, it is mandatory to provide supporting data and proof validating the durability of the concrete and proving its structural integrity against cracks in its service life.
If not validated, then the engineer in question is automatically required to consider the concrete to be cracked or crack in the future and has to consider fixing solutions that are approved under ETA (Options 1 – 6).
Solutions for Cracked Concrete
Fixing solutions that are approved under ETA (Options 1 – 6) such as FAZ II, FBZ, FIS V, FIS EM, etc work both ways. Meaning, they can be proposed for both cracked and non-cracked concrete.
In fact, they are generally able to perform up to 40% better in non-cracked concrete due to the increased structural integrity of the concrete. Also in-terms of cost, though they are generally more expensive than their counter parts individually, when looked at from another angle the over-all costing comes down significantly due to the decreased quantity of anchors utilized in comparison to anchors such as FBN II and FXA which are specifically for non-cracked concrete.
fischer has always been at the forefront of the international fixing solutions industry. With over 70 years of innovation, research and development fischer has developed a multitude of solutions over the years with over 1500 patents and still continues to introduce new and innovative products to the market. fischer has grown tremendously over the years with over 46 subsidiaries worldwide with fischer Middle East and Africa being one our fastest growing subsidiaries.
fischer MEA headquartered in Dubai, UAE caters to the entire Middle East and Africa through its local branches across the region and strives to support all your queries.
If you have any queries or enquire on fischer’s range of products and services, do get in touch with us through email@example.com.
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