Cracks in concrete
Cracks in concrete
(OP)
I have some crack issue on site. The concrete was poured between June and September 2009. The concrete used was 40 MPa concrete, the slump measured was 40mm and 50mm at the time of pour. The concrete cylinders strength results were ranging between 35 to 60 MPa. The slab poured at 45 angle for channels. The cracks were noticed in slab in July 2010 (see attached photo). I am just wondering what causes slab to cracks so quickly. The slab was poured on granular base.





RE: Cracks in concrete
RE: Cracks in concrete
About 70% of the shrinkage occurs in the first 12 months after pouring the concrete. As your time period is about 9-10 months, you would be expecting shrinkage cracks by July.
RE: Cracks in concrete
RE: Cracks in concrete
If you have a high slump that was caused by a high water-cement ratio, then you will have a lot of shrinkage. If your high slump was a result of admixtures, shrinkage is not usually an issue from the slump indication. A 40-50mm slump is not much, so I wouldn't consider that to be a contributing factor. It is more likely just drying and autogenous shrinkage, coupled with some physical restrain conditions from the pipe and variable thickness.
RE: Cracks in concrete
RE: Cracks in concrete
RE: Cracks in concrete
There is no plastic placed between granular base and concrete. As per sub contractor wet curing was carried out for 7 days by placing wet burlap on top.
Kikflip,
It is not Milton, Brisbane, Aus this one is in America
Thanks for all your help