Mold for square plinth?

[estwing]

When it comes to concrete casting and the formwork thereof, I know nada...

But physics, I know that!

Therefore, I can tell you that the pressure at the bottom of your form will be 1.5 * 9.81 * 2400 / 10000 = 0.35 kg/cm². This is regardless of whether you make the form 100x100mm or 2x2 meters!
(Here, I have used Fasting65's density figure, which seems reasonable).

This pressure acts both against the ground and the form's walls at the bottom.

It might be best to convert the pressure to 35kg / square decimeter to make it a bit more understandable which forces we need to manage.

If you place a crossbar according to the picture in post #6 with cc400mm, the force trying to pull off the bar will be
2 * 4 * 35 = 280 kg.
With cc200 = half = 140 kg.
(Approximately, as the force decreases higher up...)

If you make crossbars of, for example, standing 45x120-145 and attach them to each other with two M12 bolt connections at each joint, it should hold quite well.

But the question remains, how much will the board bulge between each crossbar, what is the minimum cc applicable?

If only I had your knowledge of calculating this stuff....:wow:d^_^bd^_^b

Then, the image by Fasting he made is completely correct with locking bars.
40cc is enough for this small form if you use locking bars.

Best regards,
estwing

 

[Nybyggarn]

We cast 10 round pillars with a diameter of 600 about 1 meter high with a plate 1x1 meter at the bottom. Initially, we considered casting in two stages, but the concrete guys pumped (had a concrete pump truck) a little "thicker" mix at the bottom of each pillar before filling up the rest, so we avoided the cost of bringing them back again. It worked well, very little was pressed out at the bottom, and it doesn't show anyway.
Make sure to brace the form properly sideways as there will be a relatively high center of gravity, and it won't be pleasant if it tips over. Be careful not to vibrate too much; the concrete guys said that it's often when you vibrate too much and hit the form that they can collapse.

 

[Suhagg]

Did it go well?

 

[karlmb]

I am pleased to report that the above-mentioned square molds work excellently (25x25 cm)
I cast about 190 cm high and had about 25 cm c-c on the cross braces at the bottom and up to 45 cm higher up.
Only supplemented with a couple of tension straps in the two lower sections.
Saw no signs of bulging or leakage.
Soon I can dismantle the molds, it will be exciting...

 

[Astrakanvägen]

I am pleased to announce that the above-mentioned square molds work excellently (25x25 cm)
I cast about 190 cm high and had about 25 cm c-c on the crossbars at the bottom and up to 45 cm higher up.
Only supplemented with a couple of tension straps in the two lower compartments.
Saw no sign of bulging or leakage.
Soon I can remove the molds, it will be exciting..

Glad to hear that these constructions seem to work. How long would you say one should wait before removing/taking off the molds?

 

[alexander___]

I am pleased to report that the above square molds work excellently (25x25 cm)
I cast about 190 cm high and had about 25 cm c-c on the crossbars at the bottom and up to 45 cm higher up.
I only complemented with a couple of tension straps in the two lower compartments.
Saw no sign of bulging or leakage.
Soon I can dismantle the molds, it will be exciting..

Any pictures of the final result?

 

[karlmb]

Fun that it seems to work with these constructions. How long would you say one should wait before dismantling/removing the molds?

Sorry for the late reply....
I seem to remember I waited 3 days. But it might have been 4.

 

[karlmb]

Any pictures of the final result?

I'll look them up. This is how the molds looked anyway.