Building a wheelchair ramp. How to set J hooks if putting concrete in dry
EdmanEP
| Posted in Construction Techniques on
Title pretty much says it all. I’m building a handicap wheelchair ramp, dug footers and now wonder how to set the j-hooks for the tie platform base.
not sure what more info may be helpful to help you help me haha
Replies
Even dry-laid concrete will harden up pretty good.
Here is a quote I found, (have not verified the citation)
(Paper number 034003, 2003 ASAE Annual Meeting; authors David R Bohnhoff, Zachary D. Hartjes, David W. Kammel, Nathan P. Ryan) that says this:
Hydration of a dry concrete mix after the mix has been covered with soil is herein referred to as in-situ hydration. In this study, a series of dry concrete mix footings were hydrated in-situ by burying them in sand and subjecting them to different water treatments. Footings were removed and cored at 4, 12 and 24 weeks. Compression tests on these cores showed that in-situ hydration could produce concrete with strength comparable to a normally hydrated mix. Additional research is needed to determine how in-situ hydrated concrete strength is affected by aggregate properties, initial compaction, confinement pressure, dry mix uniformity after placement, as well as conditions related to water movement into the confined mix.
If you mixed and set the concrete, you would have to wait to put a load on those hooks.
If you are concerned, lay some rebar across the bottom of the J to further spread the load.
I would set the bottom board right away, and use an extra nut and washer under the bottoms side of your sill to hold the J bolts in place.
Thank you for that, UncleMike42!
Part of my question is the actual “how”. I’ve only ever worked with pre mixed wet concrete.
Will it be the same consistency as soon as I add the water? Seems unlikely.
Do I have to stir to use the J-hooks? I would likely wait until the next day or considerably later in the day to set the lists with Simpson ties or the equivalent.
(Note I’m setting posts for a handicap ramp, as I would for a deck, not sills atop a foundation or wall-type footer)
Why are you placing the concrete dry?
Alternate solution - Mix each batch of concrete in a 5 gallon bucket. Transfer to hole. Set J-hook. Done.
Frankie