I modified an existing pool and had a new 20 ft (6 m) wall built that was subsequently back filled. The rebar was epoxied and tied into existing pool wall/floor. The wall is 4.5 ft to 6 ft (1.3 to 1.8 m) tall. 60 days later we have two vertical hairline cracks that run top to bottom. I watered the wall properly and there are no cracks in the other sections we shot (spa, etc). We backfilled 12 days after the wall was shot with hand equipment only. The sample test taken when shooting came back at 6500 psi (4.1 MPa). The original pool bottom is below the wall and has no issues. The wall appears to be 12 to 14 in. (300 to 350 mm) thick from top to bottom. My question is if the wall was shot too thick would the lack of additional rebar cause the wall to fail? And is the necessary course of action to demo the entire wall and reinforce the rebar, then shotcrete again?
There are many variables that can cause cracking. Vertical cracking is often the result of drying shrinkage of the concrete. You said you cured (watered) the wall properly, but don’t give any specifics. ASA recommends a minimum of 7 days of curing, with a wet cure preferred over a spray-applied membrane. You should have a licensed engineer evaluate the structural sections, and determine if there were any problems with the amount or placement of reinforcing in your wall section.
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