How does the cement get out of the road going transport when delivering to building sites?
Answers:
The truck has a rotating drum which stops it from setting.
Once they arrive on site, it is poured down a chute to wherever it is required, raked out and left to set.
As long as the drum on the truck is moving round, the cement will not set, but if it were to stop for too long, you'd have a permanently heavy goods vehicle.
it tips the back of the truck up and pours down a chute.
ramp on truck
If I understand your question, you want to know how they get cement to building sites. Usually a cement truck is driven to the site and it is poured directly from the truck. It can also be mixed by hand for smaller jobs.
Some are poured directly from the truck via a chute. Sometimes, particularly if the concrete is to be laid on upper floors of a multi-storey building, the concrete is pumped up via a large hose.
Guess you are referring to "mixer trucks" These carry the premixed concrete or mortar to the site in a drum on the back of the truck. Whilst in transit the drum is slowly rotated in one direction to keep the contents mixing. To unload, the rotation of the drum is reversed and the mix comes out. This is achieved by a spiral plate welded to the inside of the drum, similar principle to a screw thread; turn one way -the mixture is "wound in"; turn the other way, and the mixture is "wound out". Chutes are used to get the mixture nearer to the place the stuff is needed, (often a truck can't get to the exact spot)
Two ways..
If standard 'cement truck': It has 'vanes' in the barrel that mix the cement during transport - the barrel direction is reversed and this 'internal screw' arrangement feeds it towards the opening and down the chute at a fairly steady rate..
If the giant 'boom' cement cranes they either use an archimedes screw to feed the cement up the pipe (limited to about 60feet), for REALLY big booms then a pump (piston feed) is used.
Once at the building site, the cement is delivered from the lorry from a chute at the bag of the wagon. The rotating drum on the lorry, which is tilted, rotates and the fins inside force the cement out to the chute. At this point there is two ways I have seen on the building site opposite me. The site extends quite deeply back from the road, so there is no way the cement lorry can drive in.
The cement lorry delivers the concrete into the hopper on the back of a pumping lorry which pumps the concrete up through a large pipe that extends to the back of the building site. This method is used when they are laying down one of the floors.
The other method they use, when smaller quantities are needed is to deliver the concrete into a large, sealable funnel shaped device, with a flexible pipe underneath. When this is full, they use the site crane to lift the load over to the appropriate part of the site and open the valve on the end of the pipe, and let gravity do its thing.
Hope that explains it reasonably well for you.
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