Spawling Concrete

[marc_reusser]

A correction re. one of the previous posts...the barrel is actually 1/45 or 1/48 scale.

Marc

[Scratchman]

Here is two pics I took today.






Gordon Birrell

http://www.flickr.com/photos/77318580@N00/

[marc_reusser]

Cool! Thanks.

That thin layer/spawl like in the first pics is what I wanted to strive for.....and I like the color in the second pic.

Marc

[chester]

I believe that much of the spall seen in horizontal concrete surfaces is from over floating. That is, bringing a lot of water to the surface when the pour is being troweled. It makes for a top layer of cement and water only, with the heavier sand and aggregate staying and holding in the mix. This is top layer is much more porous and weather penetrates it and lifts it off.
   So I like the idea of the second and different mix being used over the initial pour you made Marc. Perhaps as you say, if only the initial pour was more even. You might even try some kind of resist method to achieve the flaking. Much like peeling paint but......
And has anyone tried mixing plain old cement into their pours to maybe give the proper coloring? I use it as a weathering powder on occasion.
   And lastly, if a softer more malleable wire was used like copper for the re rod, couldn't one crimp a ribbed pattern on it with a pair of pliers?

[Ken Hamilton]

if a softer more malleable wire was used like copper for the re rod, couldn't one crimp a ribbed pattern on it with a pair of pliers?

That was my thought, too.  You'd just have to be careful not to flatten the wire.  Sounds like it's worth a try.

[lab-dad]

Marc,
I think the idea of two pours is the way to go.
pour the initial aggregate laden layer first.
Then pour a thin, thinned layer over that and vibrate the hell out of it.
I think some petroleum jelly or something would work as a "resist".
May be even the air eraser to weather it a bit.
I wish I could try this out but alas there is brass and measuring tools all over the bench right now.
Keep up the good work!
-Marty

[jacq01]

   The vocabulair of my english is again enlarged. Now I understand "spalwing concrete"  

 

That thin layer/spawl like in the first pics is what I wanted to strive for.

  A possibility, try on some spots gesso and when this is still wet, sprinkle cement/sand mix over it and smooth it.  When the gesso is just dry, modify/enhance/correct sides with a X-acto or small screwdriver.

 Jacq

[shropshire lad]

Marc,
I think some petroleum jelly or something would work as a "resist"
Keep up the good work!
-Marty

   If you haven't got any petroleum jelly I'm sure you have got a suitable alternative in the medicine cabinet !

    Nick

[PuckHog]

As is the norm, learning good stuff from your posts,  Thanks Marc

                                                                    Randy

[RoughboyModelworks]

Interest experiment as usual Marc...

For the rebar, why not try using some of PSC's brass wrapped pipe in the small size. It as a spiral pattern, a little flatter than rebar, but subtle enough it could be convincing when rusted up. Or run some brass rod through a 1 mm or appropriate size die. Set the die with just enough pressure to cut a spiral but not actually cut a thread, just enough to show a spiral texture.

Paul

[eTraxx]

When I went to reply to this thread I got the "Warning: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic." .. ummm .. ok

Anyhoo. I found this thread yesterday though a search. I was interested in modeling spalling in concrete .. followed the thread (pics are all gone :/) .. and noticed the part where Marc is creating rebar. Got interested in that and found some information on calculating size and spacing. I posted my findings on my blog if anyone is interested - Rebar Calculations