SHRINKAGE CALCULATION OF CONCRETE 1

[Tstruct]

Hello,
I have to provide a plain concrete mass to make a trench for cables. Length of this trench is 15'. Sectional dimensions can be seen below.

What I am concerned about is whether there be enough shrinkage in this 15' long mass of concrete to develop cracks?
How can I check it? What would be the permissible limits and precautions?

 

[DTS419]

I wouldn't bother trying to calculate that. Re-entrant corners are crack magnets. You can chamfer the corners to eliminate the 90-degree angles and/or add a diagonal rebar behind each corner like is commonly found around openings in walls.

 

[bones206]

Is there anything restraining it from shrinking? If it’s a 15 ft long chunk of concrete free to shrink without restraint, cracking should be minimal.

 

[Tomfh]

Whether it cracks depends on the degree of restraint.

You might get away with it.

I don’t think it warrants being fully reinforced but a layer of mesh 6” off the bottom wouldn’t be a bad idea.