Retaining Walls 1

[JEB777]

I have a 6' high retaining wall supporting a concrete slab for storage rated at 150psf. The retaining wall will be 8" cmu block fully filled with grout 3000psi. No. 5 vertical bar will be every 8"oc. The wall will be verically braced with timber during the backfill process.

My belief is no compacted backfill should occur until the wall is fully in place, with rebar and fully grouted. I also believe the grout should cure 7 days prior to any backfilling. Your thoughts?

My other question is - with a poured in place concrete retaining wall 6' high - how long should the concrete cure before backfilling is allowed.

Many thanks,
Joel

 

[dcarr82775]

I would wait until the wall is built before starting backfill. As for how long, it is a matter of strength. You will not have the 150 psf surcharge, but depending on how they backfill/compact there will be a construction surcharge, but less than 150psf.

 

[DST148]

@JEB777 - Your second question regarding CIP walls - Formwork for slabs is typically removed at a compressive strength of 75% f'c. Formwork for retaining wall can be removed earlier, however, the wall should not be loaded until concrete has attained strength of about 75% f'c. Also see thread507-322251.

 

[asixth]

I don't allow backfilling until the wall has achieved the 28 day strength. If they must backfill and compact then I will allow sufficient time for the grout to cure to some extent and maintain backpropping until 28 days.