cracks in concrete SOG
cracks in concrete SOG
(OP)
Getting lots of cracks in a SOG. Size of slab was 85' x 65' control joint were sawed in after set same day the joints were 1/4" by 1" deep. and done at the column block outs in 20x20 panels. We are told that that we conrol joint were to far apart and the saw cuts were to small. That why it crack so much. slab was poured on was poured on rock and 8" of stone. Is ther eany other reason why so many cracks. We can not belive it was the control joint placement and size





RE: cracks in concrete SOG
Any other reasons
RE: cracks in concrete SOG
Another thought may be to check your rebar quantities (if you have reinforced the slab)
Regards
Andy Machon
RE: cracks in concrete SOG
RE: cracks in concrete SOG
The need for expansion joint depends more on temperature ranges to which slab will be exposed. For an indoor or covered slab, an expansion joint is probably not reqd.
Reinforcement quantity should be checked against recommendations from several authorities.
Note also that the slip membrane, which is necessary, will become ineffective if the compacted stone was not levelled with a blinding layer of sand before laying the membrane. An uneven stone surface will give mechanical keyed interlock through the membrane, and defeat the usefulness of the slip layer.
RE: cracks in concrete SOG
If reinforcing steel was continuous through joints, they wouldn't work. Joints should have been 1 1/2" deep. 20' was a standard spacing for a long time, but now 30x the thickness for plain slabs has been found to work better. With the heavy reinforcing in this slab, the spacing of the joints could be very wide, but some of the steel should have been cut at the joints. Some people don't like t he drag formula for calculating joint spacings any more, but it has worked. Expansion joints are unnecessary and a maintenance problem. Slip sheets are unneccessary.