Crack Control in Exposed Concrete Roof Slabs
Crack Control in Exposed Concrete Roof Slabs
(OP)
Hi,
I am designing a roof slab of 17 x 25m. It is in an area where temperatures will routinely be 35C in the day and drop -5 degrees Celcius at night. I am concerned that such temperature fluctuations will lead to cracks developing. It is a 250mm thick suspended slab with minimal imposed loading so very little reinforcement is required to resist the Imposed Live Loads. I am not sure how to determine what amount of reinforcement to place in the slab to control temperature cracking as a result of the daily heating and cooling of the slab. Does anyone have a simple way of calculating the percentage of reinforcement to use in such instances?
Thanks
I am designing a roof slab of 17 x 25m. It is in an area where temperatures will routinely be 35C in the day and drop -5 degrees Celcius at night. I am concerned that such temperature fluctuations will lead to cracks developing. It is a 250mm thick suspended slab with minimal imposed loading so very little reinforcement is required to resist the Imposed Live Loads. I am not sure how to determine what amount of reinforcement to place in the slab to control temperature cracking as a result of the daily heating and cooling of the slab. Does anyone have a simple way of calculating the percentage of reinforcement to use in such instances?
Thanks






RE: Crack Control in Exposed Concrete Roof Slabs
The slab has to be designed for (shrinkage + temperature difference) and crack control for waterproofing. Reinforcement need to be minimum to control crack and shrinkage in to direction (or maybe expnasion joint can be used).
Where and What is the support condition of the slab of 17m x 25m (supported by external and internal walls and columns)?
RE: Crack Control in Exposed Concrete Roof Slabs
RE: Crack Control in Exposed Concrete Roof Slabs
RE: Crack Control in Exposed Concrete Roof Slabs
RE: Crack Control in Exposed Concrete Roof Slabs
In this case we have 17m precast beams at 1.5m spacings. We have a prosuct called bond lok which is a steel shutter (permanent shutter) spanning the 1.5metres with a 250mm slab over. I was thinking of using a 10mm @ 200mm centres mesh at 50mm from the top surface. This amounts to 0.15% reinforcement. I am not sure to what extent the beams will restrain the slab (there will be reinforcement sticking out the top of the precast beams that will help to tie the cover slab to the beams)
RE: Crack Control in Exposed Concrete Roof Slabs
Add a nominal slope and some kind of roofing.
RE: Crack Control in Exposed Concrete Roof Slabs
There will be a waterproofing membrane, so my feeling is therefore that I should not be too concerned about some cracking, I therefore think Y10's @ 200 c/c will be okay.
Regards,
Sybrand
RE: Crack Control in Exposed Concrete Roof Slabs
Kieran
RE: Crack Control in Exposed Concrete Roof Slabs
I use Euclid tuff stand structural fibers plus micro fiber to control shrinkage cracks
Use normal amount of steel for the span.
mollerich@ats-sd.com 40 years PE