Mixer Truck Question

Rick Rowlands

Whats the maximum height that a truck can chute concrete to? I have two piers to pour, the tops of the forms are from five to six feet above grade. I can get the truck to about ten feet away from the forms. Any idea if this is doable?

I never really paid much attention to how high the discharge on the trucks were, I was always paying attention to what was going on at the other end of the chute.

user50444

you'd be better off calling the redi-mix plant where you are getting the concrete from + tell them the situation. Rear end trucks I have no idea on. front discharge,.... i had a similar situation on a mudslab this summer, 6 foot plus for the chute to hit my chute extension through a window. we had to pour pretty loose to make it flow + had to make ramps out of stone to get it up to accomplish that.

bwalley

Use a concrete pump.

cleveman

round point shovel.

May as well build a set of scaffolding up near it and put a tub on it and mix your concrete up there.

wrightconst

Its about 6 ft high ,and being 10 ft away your slump is going to be at least a 8 in just to get it down the chute .Ask for a front loader he can get closer so you can pour a 6-7 in slump

Rick Rowlands

I have a crane on site and can use a bucket. I'm not going to spend the $1600 extra for a pumper truck so thats out of the question.

The only other problem is how to place the concrete at the start of the pours without dropping it eight feet. The piers will be 2' x 3'6" x 8' high, and of course dropping redi mix over 3 or 4 feet will cause segregation of the mix.

bwalley

Where can you get a pump for $1600?

Around here we just hire a sub to pump the concrete, a lot of the concrete guys have their own pumps.

Rick Rowlands

Local concrete pumper outfit wants a minimum of $800 just to come out with their equipment. I plan on doing the piers in two pours so I don't have to build twice as many forms. I don't know of any subs around here with smaller concrete pumps. We're not exactly in a part of the country where there has been a plethora of construction activity.

rustyjames

I would plan on using the crane/bucket, 6' is going to be a stretch to get it to come down the chute, even with a front discharge truck.

I've been on jobs where we've built fill ramps to increase height.

As for dropping the mix you need some kind of an elephant trunk or tremie for your bucket.

jomama

I agree with all of this & will add:

- IMO, 4' high + 10' of chute = 8"+ slump.
- 6' high + 10' of chute = you need a ramp to get the truck higher.
- When in these situations on the past, we've called the supplier to send a truck out (usually returning from another job empty) at their leisure to do a trial fit. An experienced driver can usually tell you right away if it's going to work or not. This is obviously easier to do when you have a good working relationship with the supplier. It also let's the dispatcher know from the driver how long they may be tied up on a strange pour.
- Avoid a rear discharge at all cost. It's been years since I poured with one, but as I recall, there discharge height is quite a bit lower.
- If these columns have any amount of steel in them, your going to have some segregation no matter how far you drop the crete.
- Use a vibrator to consolidate when worried about segregation.

concretemasonry

Some R/M companies have truck mounted pumps or conveyors in addition to using there own pumps or hireing and coordinating a pumping sub.

6" or 8" slump is too much and you will have a lot of consolidation that forces the water up and out. - That may not be a problem depending on the quality required. You never want to dump it full and go to the next if it is important and that is why many contractors place some and let is sit while they move on to the first half of the next pour. - that is why many contractor choose to use pumps and save some labor in the end.

Your pour height is probably not too much, but it is best to split it up. You could never get away with that on a bridge or critical job.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Rick Rowlands

After talking to the local concrete supply house I'm going to rig up a hopper and elephant snout to reduce the freefall of the concrete. I'm going to pour probably the first three feet of each form, let them set up a bit then pour the rest.

Thanks for the help guys.

concretemasonry

Just make sure you drop the vibrator through the top layer into the lower layer to make it look and act like a continuous pour and act that way without the possible problems that someone may find later - just good practice.

Even a guy making cylinders will do it in layer for a 12" high cylinder to get the uniformity and maximum strength for the tests (also required by ASTM procedures).

An elephany truck or snout is always a good idea because it also reduces the segregation and splash on the rebars about that can coat and dry on them, reducing the bond. Not a big problem on a relatively short column, but you never know. When I worked as a bridge inspector in the "dark ages" we had to time, mark and log the lift heights for 30' high piers (in the specs). It also kept the delivery trucks on time because the supplier knew it was important, so little labor was wasted on "breaks" in the shade.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

jomama

I think this is what you were talking about Dick.

concretemasonry

That is the idea. Not too fast and just right. A good hauler that can get in and is good for masonry grout or controlled (not fast) dumping.

I don't think County has those, but it could be a company they control if it is in WI. They have failed miserably in MN, except for precast.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

jomama

Dick, A good driver is definately the key in a situation like this. Not the case on this given day. Young kid, had never seen him before. I usually have the upmost of confidence in CMU walls, but this job was extemely "freestanding". I had little faith in it until the the concrete cured. BTW, they're 12" Ivany at 14' high in the middle wall & 8" Ivany at 12' high on both outside walls, all tied together by 4" dia. pipes with anchorments. Before we got to anchorment height on the 8" walls, we could have easily pushed the walls over by hand. My fear was an un-experienced concrete driver could easily just touch a wall and trogger a dominoe effect. I was glad when that day was over!

As for County, this is definatly no affiliation. For ready-mix concrete in our area, there's a few local family owned companies & a few N. Illinois owned companies. As far as I know, County holds no stake in any ready mix companies in our area. When it comes to CMU, they have moved in big time in the last 5 or so years. I rarely use County though (except for a brick match on this very project), & usually deal with Bend/Oldcastle/Northfield/whatever there name is this year. County has a far stronger hold on the Northern & Western regions of WI, at least for now.

CJKarl

Now THAT is a sweet set up, never seen that here in the east. Unions would never allow that on a big job though.

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