I visited a site this week. It`s a fair size job, about 1200 sq. m in 3 areas, plus a staircase. I had been told, the sub floor was in good condition, but that was not the case. It turns out, about 700sq had 20mm asphalt covering the slab. The building is 40-50 years old, and it`s on the first floor, with several columns running through it. The asphalt was poor, and cracked, and chipped up easily. This has now been removed, but the stress cracks run through the concrete slab beneath, mostly between the columns. I have moisture tested, and its dry. So, what would you do to sort out the cracks ? Ive been in this situation a few times, with large areas, but i`m interested to know how others would deal with this.
Csn remeber the name of it but there is a uzin product that is used to fill cracks that you chuck fibres in with to stop it getting any worse, then screed as normal ott.
Is the concrete moving when you walk on it. So like a blown 2nd layer of concrete? If its moving then you need a epoxy product. If its stable and is stress cracks from drying then a repair compound can be used. Does it have expansion gaps? it might need expansion gaps cutting if the cracking is due to expansion stress
I think its stress, as its mostly between columns. Where the cracks have formed, over time, some of the concrete has debonded. Some areas, have lifted, so the slab on either side of the crack is up to 10mm higher/lower. There is a total of 150lin m of these, and no expansion joints in the screed. As these cracks appear to be historical, I have proposed to cut back 150mm each side of the crack to leave a 300mm void @ 75mm depth Fill with Topcem, 1/4 mix Cover with 500mm Uzin webbing, with fibre screed 1m wide, over the affected area. The rest of the floor will have a normal 3mm coat of latex.
sounds like a plan. But i think i would introduce a expansion strip where you cut out. No sure how teh uzin webbing would work over a expansion strip or if you would need to leave uncovered. End of the day the subfloor has moved for a reason, if its debonded then i would guess due to expansion. Dont know tho, only guessing.
