Raft foundations

[Erie Fred]

Precast is not available ?
Or no crane access ?

 

[8ob]

Yes, the joints would have projecting rebar, actually the top of the horizontal foundation beam cage.

Not being a concrete pro, I have never heard the term "laitance", so thanks for that ! I was aware of the existence of it though, and when we cast a retaining wall at the top of the garden, scraped it off before it had set, although at the time, my thinking was to roughen the surface for the next pour to bond to !
Now I am aware of it as a problem, I can remove it.

What is HAVS ?

If pumped from road, distance would be about 40 metres. I have a pump man coming Tuesday to discuss the job and go through the options.

BiL has an ancient 3 ton dumper, and like the vulture he is, the pipe washout can go in there, and he will "helpfully and at no charge" take the excess away for one of his projects.

Most of the decent concrete suppliers have their own pumps or at the very least a sub contractor they can recommend. If you are casting in two parts you will need to leave the starter bars long enough to bend over @90 degrees to join/wire tie to the rest of the cages, overlap is normally 600mm, a small kango will suffice to rough up the mating surface.

Bob

 

[gaz1]

I know this would be the preferred option, and it will be needing to be pumped anyway, but this involves the lane being blocked for several hours, and will need at least three mixers worth.

The excavation was done years ago and never finished. It was also overdug, so I need to raise the level somewhat. It is on pure chalk, so I thought maybe I could cast the understructure more or less on the surface of existing surface, then do some infill and then pour the slab over this.

Structural engineer has massively overspecified because of this, but am hoping for some input before I go to building control with it.

that reference is used with high rise buildings with piles/columns into the ground and then a slab poured on top and then repeated all the way up the high rise building

you could also use center support columns as well to support the slab

however the top slab is pored as one mold continuos

im also curious are you going up or down as you dont say in the post down is easy enough but up is pumped

 

[Dapph2]

They can pump that far I think. They ban also pump vertically. If you want much more than a cubic metre, is in not worth the hassle of wheelbarrowing it, even less mixing it yourself. Ready mix costs just over half what it would cost to buy the materials to mix yourself, with no effort. Its a no brainer.

Thanks for that...there is no way I want to mix or barrow 11cubic mtrs of fibre glass reinforced mud.. even if I was fit and able .

 

[Agroshield]

What is HAVS?

Hand Arm Vibration Syndrome (vibration white finger). Sorry.

 

[Smallfry]

that reference is used with high rise buildings with piles/columns into the ground and then a slab poured on top and then repeated all the way up the high rise building

you could also use center support columns as well to support the slab

however the top slab is pored as one mold continuos

im also curious are you going up or down as you dont say in the post down is easy enough but up is pumped

If pumped from the lane, would have to be pumped over a hump of about four feet, then down about two feet

The base outside is 7.5 m X 9 m. The is a cruciform inside too. One part of this is titled as a shear key, to stop the building sliding apparently. This is .5 of a metre deeper than the rest. As the foundations are deeper than the surrounding ground level, I cannot see that it would slide anywhere. All overkill IMO

 

[cocker]

Speak to your local concrete suppliers .
One of the concrete firms we use to use had trucks with tele-belts on them , truck rolls up unfolds tele-belt (20 meters ish) sends conny . Quick rinse and gone .

 

[gaz1]

If pumped from the lane, would have to be pumped over a hump of about four feet, then down about two feet

The base outside is 7.5 m X 9 m. The is a cruciform inside too. One part of this is titled as a shear key, to stop the building sliding apparently. This is .5 of a metre deeper than the rest. As the foundations are deeper than the surrounding ground level, I cannot see that it would slide anywhere. All overkill IMO

so why cant delivery trucks just deliver as is ?

the trucks exit port is over 4ft high and the chute tends to be extendable about 6-8ft in a swingable arc you just got to wear gloves wellies or your hands get coated swinging the chute where you want the cement

i still cant see why you need the pump system when a truck is actually enough as is unless the lane is much lower than your house then id agree that you need a pump or another alternative to get the cement up to the property to get it unloaded

its the material your forming on thats an issue clay is one thing soil is another and chalk no comment to that material

 

[Erie Fred]

so why cant delivery trucks just deliver as is ?

the trucks exit port is over 4ft high and the chute tends to be extendable about 6-8ft in a swingable arc you just got to wear gloves wellies or your hands get coated swinging the chute where you want the cement

i still cant see why you need the pump system when a truck is actually enough as is unless the lane is much lower than your house then id agree that you need a pump or another alternative to get the cement up to the property to get it unloaded

its the material your forming on thats an issue clay is one thing soil is another and chalk no comment to that material

Do you have a TeleBelt truck available ?
Not much more than standard delivery, and can reach out about 40'.

 

[Smallfry]

so why cant delivery trucks just deliver as is ?

the trucks exit port is over 4ft high and the chute tends to be extendable about 6-8ft in a swingable arc you just got to wear gloves wellies or your hands get coated swinging the chute where you want the cement

i still cant see why you need the pump system when a truck is actually enough as is unless the lane is much lower than your house then id agree that you need a pump or another alternative to get the cement up to the property to get it unloaded

its the material your forming on thats an issue clay is one thing soil is another and chalk no comment to that material

Not a case of can't, but won't

None of them want to operate in the lane therefore blocking it for a few hours, OR make a mess on the surface.

The lane is narrow, and the entrance is not wide either, so they can't make the turn.

 

[Smallfry]

Do you have a TeleBelt truck available ?
Not much more than standard delivery, and can reach out about 40'.

Speak to your local concrete suppliers .
One of the concrete firms we use to use had trucks with tele-belts on them , truck rolls up unfolds tele-belt (20 meters ish) sends conny . Quick rinse and gone .

Distance of 45 metres, I measured it yesterday, so would not be far enough.

None of the local big names claim to have them.

Any pumping would have to be via pipe too. Can't use a boom type because of overhead power and phone poles, just to make it even more difficult.

 

[KaneH]

Dont know if you can figure this out.

Any" joints" in the slab would be horizontal. Between the edge thickening, sheer key and centre web, and the 250mm top slab

Again, still not an issue. You should have shear links in the reinforcement design tying the thickenings (whether shear key, edge thickenings or internal thickenings) into the main 250mm slab.

Say your thickenings are 400mm deeper than the underside of the slab, you’d set your cages on the thickenings to the full depth (650mm in the above example less cover) then pour your thickenings as part of the first stage. Then return, lay your slab reinforcement with adequate laps to your cages which are partially set in the thickenings and pour your slab. If the area of the slab is too large for a single pour then you introduce a shutter with starter bars extending into the next pour zone and cast the first section. Rinse and repeat until the full floor is done.

Depending on how you intend on installing the form work for your retaining walls you may also want to cast a small kicker off the raft for locating the base of the shutter.

Waterbars are critical to all construction joints to ensure the water proofing arrangement is maintained.

The above is obviously an assumption made on the description you’ve provided so if I’ve misunderstood a quick photo of the drawing would be helpful.

 

[gaz1]

Not a case of can't, but won't

None of them want to operate in the lane therefore blocking it for a few hours, OR make a mess on the surface.

The lane is narrow, and the entrance is not wide either, so they can't make the turn.

so will only drop off at a main lane as refusal to block a rd off

Distance of 45 metres, I measured it yesterday, so would not be far enough.

None of the local big names claim to have them.

Any pumping would have to be via pipe too. Can't use a boom type because of overhead power and phone poles, just to make it even more difficult.

is the main lane higher than your dwelling ?

is there a field between your property and the lane

 

[Erie Fred]

Any pumping would have to be via pipe too. Can't use a boom type because of overhead power and phone poles, just to make it even more difficult.

Actually....just pipe concrete pumping is easier IMHO.
The pump is a small trailer unit pulled behind a simple pickup truck or similar sized van.
Pipe is laid on the ground with quick couplers. (Vitaulics or other system)

 

[gaz1]

Actually....just pipe concrete pumping is easier IMHO.
The pump is a small trailer unit pulled behind a simple pickup truck or similar sized van.
Pipe is laid on the ground with quick couplers. (Vitaulics or other system)

if you got height you can chute it rather well
chutes can be made out of scaffold planks in a v shape and scafolding with strengtheners between them

5m wet mix

cliff face more solid mix high fall

 

[Erie Fred]

if you got height you can chute it rather well
chutes can be made out of scaffold planks in a v shape and scafolding with strengtheners between them

5m wet mix

cliff face more solid mix high fall

Looks like an awful lot of work & labor for such a small job.

BTW that was used around here in the early 1900's, we've gone away from it for a multitude
of reasons, the biggest one being segregation of the mix.
A very bad thing for concrete.

 

[Agroshield]

Any pumping would have to be via pipe too.

Standard steel pipes are usually 3m long and the delivery pipe is normally rubber so you can waggle it to and fro to distribute the stuff. If you have a vibrating poker, that can also help move the concrete about and level it.

If everything is laid to the same top level, ask the concrete company for a slightly higher workability (150-200mm slump) and that will also help you. They achieve this with plasticiser rather than excess water so the strength is maintained.

You would pipe up to the furthest point and start filling. Once it is full local to the end of the pipe, remove a steel pipe, drag the rubber back and reconnect. Assess how many bends you would need to achieve an optimum route and let the pump company know so they bring enough.

Forgot to say above that the pumping company might expect you to provide a couple of bags of cement to grout the line.

 

[cocker]

Camfauds can't help ?

 

[Smallfry]

if you got height you can chute it rather well
chutes can be made out of scaffold planks in a v shape and scafolding with strengtheners between them

5m wet mix

cliff face more solid mix high fall

I can see this might work for a small amount of concrete if there is height, but here it will have to go over a hump, and the lane is lower.

The mix they are using looks like there is too much water in it.

 

[Smallfry]

Camfauds can't help ?

Not local to here, and looking at their website, it looks like they would only do larger commercial projects

I have to keep the costs down too. Don't have the budget. Wish I did, would just pay someone do do it.