How to avoid carcks in Reiforced concrete ribraft 4

[steelnz2003]

Hi
I have done a ribraft foundation on groud the soil is a clay soil the ribs are 110mm at 1200mm spacing 300mmm deeo they have 2HD12 at teh bottom and a SE
mesh on top with mm cover to the top and cover to the bottom

 

[MotorCity]

The cracks in the photo do not look significant to me. As for avoiding cracks in concrete, cracks will happen. Its usually not a concern that the concrete is cracked, but rather the width and nature of the crack.

 

[Structural_WIZ]

I agree, the cracking in the foundation appears to be cosmetic and likely due to normal contraction/shrinkage during concrete curing or due to temperature changes. See ACI 360R-10: Guide to Design of Slabs-on-Ground for additional information. In general, steel reinforcement in concrete foundations and slabs on grade does not prevent cracking, rather it is used to minimize crack widths (this is not true for pre or post tensioned slabs). Owners typically do not understand this, and will see normal concrete cracking as a flaw. Therefore, it is important to educate the owner regarding the design or minimize/prevent random cracking with carefully placed control/contraction/construction joints.

 

[hokie66]

Ribs create restraint, therefore cracking, which is unavoidable. Reinforcement controls the crack size. The more reinforcement, the smaller the cracks.

 

[steelnz2003]

Thanks gentlemen