I’m pouring a new foundation/basement wall under my house. Since it goes all the way up to the joists, there’s no way to rod it as it’s poured to eliminate voids.
I’m sure someone knows a technique to improve results in such situations, which I hope you’ll share. What’s the best way to deal with such a pour to minimize voids?
Thanks.
Replies
it needs to be vibrated, remember fast in, slow out.
if there is access for a hose to pump in concrete there is access for a vibrator.
rent a concrete vibrator
you can add super plastisizer to the mix, this will make the concrete wet for about an hour and after it wears off the concrete will set as if it were never in there. this will not effect the strength of the concrete. this will ease the placment of the mix. be careful, wet concrete = more preasure on forms. if you use a plastisizer, don't let readi mix add it at the plant. it sould be added at the time of placment. you get a small window of time to work with the suff, when its done it's done. adding water once the plastisizer has worn off is a big no no. another option is to use a smaller aggergate in the mix. 1/2" stone with some extra sand will help with honey comb. becareful not to over vibrate, you may end up with bug holes.
Interesting point, since I've been looking all day for a point-of-use SuperP that comes in something smaller than a 55 gallon drum (!)
The concrete countertop supply people have it:http://www.concretecountertopsupply.com/store/ccp0-catshow/AdmixturesPozzolans.html
Jeff
That's some excellent advice.
"Preach the Gospel at all times; if necessary, use words." - St. Francis of Assisi
No, I didn't vote for him; but he IS my president. I pray for the his safety, and the safety of his family every day. And I pray that he makes wise decisions.
If the issue is access through the top of the forms to get the vibrator in look at vibrators that attach to the exterior of the forms. It will cost more than renting a normal vibrator since they need to be attached before the pour and can't be moved but in some cases that's all you can do.
If you can't get the vibrator in how will you get the concrete in is what I want to know.
Some pours have limited access. The vibrators that are affixed to the forms besides consolidating the pour are used to move the material to areas not accessible.
First off, how high is the forms we are talking about? If it is under 3', then use your hammer on the outside of the forms as a "vibrator". Just "whale the hell out of 'em", , and be sure you do it equally to all the forms. One other "trick" you might try, use a "palm sander" held against the outside of the forms. As for the concrete itself, use a #6 or high slump to let the concrete "flow" into the forms. Hope this helps out.
use your hammer on the outside of the forms as a "vibrator".
That reminded me: Have used SawZalls w/o blades as outside vibrators.SamTA Pragmatic Classical Liberal, aka Libertarian.
I'm always right! Except when I'm not.
I have a palm nailer with an attachment for vibrating the outside of a form. If i recall just a metal block that replaces the barrel. Used it one time on small pedestals under a crawl space.
mike
Yeah, for short walls I never use a vibrator. Someone with a bit of experience and an estwing means no honeycombing. Young, enthusiastic kid doing the same usually means wrecked forms though.
A rubber hammer is less likely to bust things up.
Jeff
Just rent a vibrator it like $25 a day. Even Home Depot has them
"A rubber hammer is less likely to bust things up."
I form all short walls out of 1"x8"s. It's easy to see when you have bashed them enough as they begin to seep through the cracks. A rubber hammer is a good idea, although I'm not sure what the rest of the guys might think...
When using a hammer as a vibrator, don't hit the forms like you were trying to drive a spike. Half-swings, and get a nice, steady tapping going. You can tell by the sound of the forms being hit, how well you are doing. A rubber hammer would be an idea, but the mallet wouldn't last very long. Just start "tapping" at the bottom of the form, work a circle pattern up towards the top of the pour. " Although I have the right to remain stupid, I try not to abuse that right"
you never met some of the helpers out there...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Actually I have ;o) (seriously)
View Image
Helper? That looks like one of my old foremans! Usually just to scare the "new-to-this-kind-of-work people." Although I have the right to remain stupid, I try not to abuse that right"
I mention earlier about using a vibrator in pouring a wall, As a rental, vibrator are cheap, about $25. Everybody here keep saying, oh just hit it with a hammer. well that is fine but a hammer does nothing to remove air pocket interior of the wall. These air pockets are a structual issue with freeze cycle.
With the type of wall the OP was talking about ( short, narrow) a hammer will be just fine. Anything under 8" wide and 36" tall will hammer-vibrate just fine. Now, IF the was a LOT of "stuff" in the wall pour (too much rebar, pipes, conduits, and the like) then a regular vibrator is needed. Also, with the "hammer-vibrator", there is less chance of over vibrating and cause a blow-out. Vibrators tend to "loosen up forms as well as concrete. In a wall the size the OP wants, use a 7-8" slump concrete and the hammer. Pour it thin and let it flow. " Although I have the right to remain stupid, I try not to abuse that right"
Hilti TE-75 with a bush head. Have used it many times in no access pours. In these tight pours where blow out from vibration are balanced with heavy need for vibration, we'll often start to pop relief holes in the bottoms of the form ply. Most times just a couple 16's pounded and pulled to just let the juice out.
I<M NOT TALKING ABOUT HONEYCOMB but the entrained air and entrapped air of wall placement
SIGH" Although I have the right to remain stupid, I try not to abuse that right"