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1:32 Viaduct pattern for concrete


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I poured the first half of the column mold with urethane rubber. It was my first time using urethane, but it was just like silicone except for the mixing ratio. It almost poured like water, a little thicker, so I am glad that I sealed all of the seams with clay or it would have ran out. Unless there is some void in the mold, it should come out fine. Here is a picture. post-547-0-36507900-1428445208.jpgpost-547-0-07436000-1428445220.jpg

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If you are talking about concrete, about 10 yards, not including the foundation, about another six. If you are talking about urethane, about 160 lbs., about 1200 dollars, well it's only money, but it will sure to be good looking.

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Here is the finished mold for the column for the viaduct.  No bubbles, came out perfect even though I have never poured urethane before.  No degassing necessary. mixed easily, did everything by the directions and it worked out well. Here are some pics, next I will have to try out some concrete and the vibrating table. Bob.post-547-0-07882100-1428582043.jpgpost-547-0-01331500-1428582064.jpgpost-547-0-98416200-1428582089.jpgpost-547-0-29586300-1428582109.jpgpost-547-0-83576500-1428582123.jpg

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I am preparing the mold right now and maybe pour tonight or tomorrow. Just went down and bought some white cement, sand, p gravel, and some Perlite. I will make several combinations to see which is the best as far as weight and resolution is concerned, so I will post pics. soon. Bob.

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I am preparing the mold right now and maybe pour tonight or tomorrow. Just went down and bought some white cement, sand, p gravel, and some Perlite. I will make several combinations to see which is the best as far as weight and resolution is concerned, so I will post pics. soon. Bob.

You probably know much better than I do about how to make strong (lightweight?) concrete. I don't know what white cement is but I hope it's just Portland? Is the P gravel then just for the surface?

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Lightweight concrete is weaker than concrete made with the proper sand and gravel mix. A regular mix is about 3000 psi. strength.  The mix that I will use is only about 1800 psi, but it doesn't have to be very strong, it just has to hold up 1/3 of the top piece.  P gravel is 3/8 in. rock or gravel.  White cement is white Portland.  The lightweight concrete recipe that I will use has no rock, just one cement, 2 sand and 2.2 Perlite ratio by volume.  I got the P gravel to make one column to compare the weight to the lightweight version.  The gravel or rock in concrete is for strength.  P.S. the above picture of the column is just the pattern from the mold that I painted white, I haven't poured the column yet. Just joking since you wanted to see the end product, I will be pouring it tomorrow.  Bob.

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The top piece, if made with rock would weigh 172 lbs. If I can make it with Perlite, it will weigh about 90., again, it doesn't have to be very strong. If I can't get the looks, detail, than I will make it with rock, and have to use dollies to haul around, but I hope the lightweight stuff works out.

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I only said that (about P gravel) because I don't believe it will add strength. IMO, the round edged P gravel will serve as a crack starter. Unless you're describing regular shaped rock.

I believe you probably know more about concrete than I do. I had no way to know that originally. Please forgive my interruptions.

The reason I'm going for strength up here, is the deep frost we get will crack just about anything. I'm hoping to try a new waterproof additive to a mix to help with discoloring and staining.

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Thanks for you input.  Down here in Florida, very little freezing threat.   When I say P gravel, the rock is at varying sizes, can't use 3/4 rock, just too big. I have poured large column bases for my house with great results, no cracks. You can view them on my channel on YouTube---omiateeful,  There are about 53 videos.  Just scroll down.

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I just poured the, quote, lightweight version of the mix and I don't like it. I had to use much more water than the recipe called for just to get it in the mold. I will pull it out of the mold in 2 days. I am afraid I will have to use the regular concrete mix to get the detail and strength, we shall see. Bob.

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post-547-0-95563700-1428747547.jpgpost-547-0-60846900-1428747559.jpgI just demolded the column and while it is OK, I think I will use not the lightweight mix, I will use the regular mix, less porosity.  There are some small bubbles, not noticeable  from a distance, but close up, you can see them.  It demolded easily, no problems. Bob.

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Tomorrow I will demold the one made with regular concrete and see how that one looks. I vibrated both, but still some small bubbles, can't really see them from 3 feet, so maybe I won't worry about them. I will weigh both of the columns to get an idea of the weight difference and I will post them tomorrow. The vibrator that I made worked well, lots of bubbles came out except for the small ones. Bob.

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Here are the results of the column poured with cement sand and gravel.  Very few bubbles, after vibrating for 2 minutes, it weighs 16 pounds as compared to the lightweight version of 10.5 pounds.  I will go with the, 16 lb. version.  There was a 35 per cent weight reduction in the lightweight version, so that means on the large section, it would weigh 110 lbs., still have to use a cherry picker for large moves, so I will probably use the all concrete version rather the one with Perlite. Also the Perlite version is impossible to finish properly the top, the perlite rolls and you can't get a smooth finish.  I had to add some soup after it had dried to smooth out the top.post-547-0-22675000-1428843250.jpgpost-547-0-45782300-1428843381.jpg  Here is a pic.  Help with painting please. Bob.

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