foundation problems caught early

[bobbixler]

The foundation has been backfilled now so I'm glad I've got photos at least. No repairs were done even after complaining. Thanks again to all for taking time to respond.

[worthy]

Anyone know whether it's correct that vibration is too much for regular residential formwork? or are my concrete guys just blowing smoke?

About as correct as when they tell you that the concrete will flow into the forms better with some added water.

[Dick Hackbarth]

Worthy:
The fact that the guy’s forms can’t take a little concrete vibration just means he’s building cheap, inferior forms, and he aught to step up his game or go home. On the other hand, you can shake commercial bldg. conc. forms apart if you don’t use the vibrators properly and carefully. Form construction and preparation for pouring is an important part of the job whatever the bldg. type.

Yes water will make the conc. flow a little better, and make the effort required by the placers and finishers a little easier (again, cheap lazy conc. sub) but it significantly reduces the strength and durability of the conc. too. And, we normally don’t want that just to save the conc. sub a little effort. Look up water/cement ratio vs. compressive strength and durability. But then, what does he care, except at the moment he saves some time and labor and effort, in not doing it right. After all, he is long gone by the time the inferior conc. starts showing it true colors. Talk with a few local ready-mix suppliers, they usually proportion their mix in the truck so that a little water can be added at the site, during the final mixing and just before being discharged, and their drivers know how much this should be. The conc. sub wants more water because it makes his work a bit easier. But, you end up with inferior conc. Tell the drivers you will not allow that much water added.

[parkwest]

Worthy:
The fact that the guy’s forms can’t take a little concrete vibration just means he’s building cheap, inferior forms, and he aught to step up his game or go home. On the other hand, you can shake commercial bldg. conc. forms apart if you don’t use the vibrators properly and carefully. Form construction and preparation for pouring is an important part of the job whatever the bldg. type.

Yes water will make the conc. flow a little better, and make the effort required by the placers and finishers a little easier (again, cheap lazy conc. sub) but it significantly reduces the strength and durability of the conc. too. And, we normally don’t want that just to save the conc. sub a little effort. Look up water/cement ratio vs. compressive strength and durability. But then, what does he care, except at the moment he saves some time and labor and effort, in not doing it right. After all, he is long gone by the time the inferior conc. starts showing it true colors. Talk with a few local ready-mix suppliers, they usually proportion their mix in the truck so that a little water can be added at the site, during the final mixing and just before being discharged, and their drivers know how much this should be. The conc. sub wants more water because it makes his work a bit easier. But, you end up with inferior conc. Tell the drivers you will not allow that much water added.

Check the delivery tickets and check the slump on each batch poured if that is your concern, or in this case, peace of mind.

Do they still use plasticizer?

[Ted S.]

The moral of the story is always hire a good builder who has a good set of subs. I think Dick covered the concrete issues pretty well, I'll note that even after the question was raised by presumably the homeowner, the contractor disregarded the question and moved on.

[Allan Edwards]

The conc. sub wants more water because it makes his work a bit easier. But, you end up with inferior conc. Tell the drivers you will not allow that much water added.

This is important, especially when pouring (placing) concrete in hot weather. The guys on the ground working the concrete want is a wet as possible, it makes their job easier. But as stated too much water weakens the concrete. That is why one of my 1st questions to my foundation contractor is how many men will be on the job the day of the pour. If I deem it to be too few, I ask for more. I also watch and limit how much water is added to each truck. 5-10 gallons is ok. Finally, we often have geotech people on the job doing slump test and testing psi of concrete, not every truck but every 4th-5th truck.

Allan

[Ted S.]

This is important, especially when pouring (placing) concrete in hot weather. The guys on the ground working the concrete want is a wet as possible, it makes their job easier. But as stated too much water weakens the concrete. That is why one of my 1st questions to my foundation contractor is how many men will be on the job the day of the pour. If I deem it to be too few, I ask for more. I also watch and limit how much water is added to each truck. 5-10 gallons is ok. Finally, we often have geotech people on the job doing slump test and testing psi of concrete, not every truck but every 4th-5th truck.

Allan

You see, that's a good builder.

[worthy]

Tell the drivers you will not allow that much water added.

For more than three decades now!

(Sometimes I must be too cryptic here.)
***
A few years ago, the former had three trucks lined up waiting to pour and more on the way. But no vibrator in sight, even though it was in the contract. Yours truly had to race off to rent a vibrator and the generator to operate it. You're made to feel that you're holding up the whole job due to pickiness.

Finally, we often have geotech people on the job doing slump test and testing psi of concrete, not every truck but every 4th-5th truck.

Wow!

[kfc510]

Worthy:
The fact that the guy’s forms can’t take a little concrete vibration just means he’s building cheap, inferior forms, and he aught to step up his game or go home. On the other hand, you can shake commercial bldg. conc. forms apart if you don’t use the vibrators properly and carefully. Form construction and preparation for pouring is an important part of the job whatever the bldg. type.

The only thing I'd add to that is that you have to take more care to tie the steel well if you're going to be vibing a lot.

kevin

[kfc510]

http://forums.jlconline.com/forums/a...6&d=1363033761

What is that that says *void*

http://www.surevoid.com/

kevin

[parkwest]

You see, that's a good builder.

Texas, especially around Houston has some interesting soil to build on...

[dgbldr]

The moral of the story is always hire a good builder who has a good set of subs.

I'll have all of my potentials call you for an opinion on that. How much per call?

[Ted S.]

I'll have all of my potentials call you for an opinion on that. How much per call?

It's so true isn't it?

A good quality GC is cheaper then a homowner trying to build their own house when you factor in premium costs for subs, mistakes, etc.

I'd be glad to field calls for good builders on this forum.

[parkwest]

It's so true isn't it?

A good quality GC is cheaper that a homowner trying to build their own house when you factor in premium costs for subs, mistakes, etc.

I'd be glad to field calls for good builders on this forum.

LOL Over 25 years ago my FIL proved that anyone can build their own home when he told me that, "No way in hell would he pay me $187K to build him a house in 90 days" and then proceeded to spend three years and over $330K to prove his point. LOL

Years ago, my ex-wife's sister's husband told me I was nothing but a con artist and a crook to try to sell him a house for $150K when he could turn around and hire a bunch of guys to do the work without a builder... he was over the $150K mark by the time he had a shell. LOL

[ThingOfBeauty]

Agree with the general sentiments.
We normally:
1. specify 28-day strength (for walls, we use 3500 PSI) and control over some ingredients (no fly ash), and get a copy of the mix design
2. Tell every driver not to exceed the mix design water proportion. It is normal for the loads to be 10 gallons below design when they arrive and to add the 10 gallons on site.
3. Check slump and pour test cylinders for a sampling of pours. Although slump is not as useful if you are doing 1 and 2, it can tell you if something is wrong. We found a defect in a huge footing with test cylinders on a job two years ago.
4. Specify wall design per ACI 318 or 332
5. Send back any truck after 90 minutes since leaving the plant. (An engineer wrote a protocol we can use on cold days when 90 minutes can sometimes be exceeded safely).
6. Limit calcium to a ratio of 2% of cement and don't use in exterior work.

We haven't required vibrating walls on ordinary residential pours, and only rarely see honeycombing. Like once per 10 pours. Maybe we should start though. As I said we always require it on critical pours. Stuff like this.
Concrete formwork.JPG
But that is not the standard aluminum 8' x 2' formwork.

Here's what our good subs say: concrete walls are vastly superior to the other options even at imperfect quality. Honeycombs are easy to fix. Aluminum forms with wedge anchors can be vibrated apart. You don't get much from vibrating a typical wall with typical reinforcing, just a risk of blowout. So far they've been right as far as I know.
One thing that's for certain is that concrete practices vary significantly by region. I wonder what role that plays. For all I know our standard formwork is not used elsewhere, or our bluestone gravel flows better or something, and the way we do things won't work for you.