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Anatelostaxus's avatar

What cementing techniques should I apply?

Asked by Anatelostaxus (1428points) August 17th, 2012

I’ve started to build a small sized monolithic dome.
It needs to withstand -20 -ish Celsius, rain, draught and heat.
I’ve applied a sheet of tar onto the cemented layer at the foundation and have covered it with another thin layer of cement. (I intended this to be a bit of Isolation from the bare soil underneath).
I am using only materials immediately available in the surrounding environment, much of which are leftovers from previous building activities. It will be about 150 centimetres high and circa 2 wide.
Up to now I’ve only been using tiles (fragmented and whole), rocks and cement mixture.
Are there any suggestions you might offer ? Advice?
cheers all.

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9 Answers

_Whitetigress's avatar

Hm, perhaps researching old grand churches pre gothic period would help you get some sort of ideas.

CWOTUS's avatar

There’s too much omitted detail here.

What is the purpose of the dome? What will be inside? At a meter-and-a-half high and two meters in diameter, it sounds like a doghouse.

You don’t really “withstand” 20°C, do you? That’s just about room temperature. (Edit: Oh, minus-20. So, kind of chilly, I get that. How hot will it be there?) What kind of rains are we talking about? Northern temperate rains aren’t generally the as tropical storms (except once in a while when they are).

Are you saying that you want to make this dome out of concrete? It’s not very clear. (No, not the concrete, as an opaque material, that’s patently “unclear”.) It’s your entire project that’s unclear to the reader.

LuckyGuy's avatar

Where are you located? What is the weather and wind like. Sun loading? Snow load?
There are too many unknowns here to answer your question well.

Tropical_Willie's avatar

Ventilation, entry and egress means a planned structure is needed. What is going into the dome?

woodcutter's avatar

Steel reinforcement will be needed with any masonry structure. Without this, the weather won’t be what brings it down. I wouldn’t put any dog I cared about in there.

susanc's avatar

Igloos and Roman domes are/were made out of a) snow and b) stone and didn’t need steel reinforcement. Why would concrete? (scratches head)

woodcutter's avatar

How many Roman domes are there now?

CWOTUS's avatar

If the concrete were to be poured and formed into nearly-but-not-quite cubical blocks of the shape required for Roman arches / domes or igloos and the dome built in that way, then reinforcement would not be a requirement (except that the footings at the ground would have to be much different than “a thin layer of concrete” or anything else). The forces built up in the arch would be transmitted through the walls and then outward into the foundation. Without a strong enough foundation to handle the outward vector of force built up, the dome would collapse. (If you ever get to see the base of the Eiffel Tower, you’ll get a sense of the enormous “outward” forces generated and why the foundation for this structure would need lateral bracing. Unfortunately I can’t find what I want to show in a quick online search. Maybe if I go again I’ll take a photo for you.)

Concrete as it is used in modern construction is not shaped into igloo-type blocks, and arches built block-by-block, and the small structure envisioned by the OP (a hemispherical structure of radius 1 meter) would use an inordinate amount of concrete to be so constructed. Not to say that it couldn’t, but it wouldn’t.

woodcutter's avatar

Rock and concrete are totally different materials when considering them for construction. Can’t really get re-bar inside stone. Stone masons have become a lost art replaced by more practical modern concrete that speeds up the building process. If a stone structure loses integrity in just one place, it could mean the end of the entire structure, depending on the structure because the thing is held together by structure, essentially by its own weight. Modern re-enforced concrete structures are tough and have the ability to withstand pressures. It stays together even if it suffers damage. Is the Hoover dam stone or re-enforced concrete? Whatever they built it with it has been there holding back a lot of pressures for decades. I hope they did it with concrete.

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