huangyhg

concrete slab crack repairs
we have been asked to review the design of a post tensioned concrete slab. the slab has cracks in excess of 2mm wide!! a repair methodology has been suggested by others, a cementitious grout will be injected under into the cracks.
normally i would have thought they'd use a low viscosity expoxy which is much more effective in reaching the full depth of the crack as it relies on gravity.
if anyone has any experience in pressure grouting of cracks, i would appreciate if you could offer some advice.
thanks
cementitious grouts are ineffective in repairing such cracks. in my opinion, you need to have a clear understanding of why the cracks occurred before the repair is made. having said that, depending on material thickness and width of cracks top to bottom, epoxy material produce more effective and stronger repairs than do cementitious grouts. as you mentioned, getting material into all of the crack is important.
one reason higher viscosity materials such a cementitious grouts are chosen is the belief that the cracks are so wide that the "thinner" material will just run out. proper procedures of placement and experience with the material can control this so that proper repairs are made.
check the international concrete repair institute for additional information
i agree with ron. cementitious grout is not the answer.
it would be helpful to know your opinion of the reason for the cracking. are they direct tension cracks extending through the slab or some other type of crack? how thick is the slab? how much tensioned steel? how much untensioned? bonded or unbonded?

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