Advice On Concrete Slab

Discussion in 'FAQs' started by msh, Jul 24, 2002.

  1. msh

    msh Member

    This is my first attempt ever of building a concrete slab...
    Overall, I'm not displeased, but two things happened. 1) I used plaster of paris to do the initial build pouring, using cork roadbed pieces as a shaper for the outside edges. My miscalculation was the roadbed allowed for a slope from the track and the outer edges, preventing my engine house from sitting properly. BAD! So, I used some sculptimold to shape them higher. After a lot of sanding, I ended up with a flatter plane, but also defects that I cannot sand down any further to remove or the slope will return, not to mention several edges that got chipped off. Sloppy! What can I do to repair them in the easiest way? Will the difference in the plaster and sculptimold materials yield different results when washed with the alcohol/india ink stain? You can see different colors already.

    I'd rather not start over, but... :(
  2. Tyson Rayles

    Tyson Rayles Active Member

    PICKY, PICKY, PICKY :D :D :D As far as the color goes every concrete slab I've seen that's been around awhile (especially when it has been exposed to oils and grease) has a lot of stains and discoloration. If the differences are too gross I would suggest using pastel chalks to even it up. I would add some more sculptamold and sand down again, but I would put the sandpaper on a block so it sands evenly (if you are already doing this please disregard that part :p ). Good luck!
  3. Tysons Got A Good Point

    I like Tyson's idea, Celebrate the discoloration for an extra touch of realism, and who ever saw a concrete slab without some edge chiping?? Looks good in the pictures.... AT&SF Duey;) :cool:
  4. marty w.

    marty w. Member

    I agree with Tyson.
    Even new concrete is not the same color or even color.
    Try spackling compound to fix the defects.
    I would just leave the defects alone and go for it.
    Look great in pic's.
  5. Vic

    Vic Active Member

    MSH, It looks just fine to me. Like the others have said leave it alone. I think you'll be very happy with it after is colored.:) :)

    I can understand your frustration with here's just a little tip for the next time....:)

    Plaster of Paris is really not a good medium for modeling for two reasons: 1. It shrinks terribly when drying and 2. It has little strength after its dry. Its ok for "artsy-crafty" things but for modeling building we need something just a bit better.

    My prefference is Hydrocal Plaster. Sometimes you can find it at hobby shops in 5 or 10 pound bags. Ceramic supply places usually have it in 100# bags. Much cheaper that way but you must store it after its opened in a airtight container. I use 2 old plastic buckets that sheet rock compound came in.

    If you can't find Hydrocal check you building suppy place for Moulding works well to.

    To avoid the plaster cracking while its drying it must be "retarded". (Just like me:D ) Add a tablespoon of white vinegar to the plaster mix and it will slow down the drying time.
  6. msh

    msh Member


    Yeah - good old reliable spackle! Fills little holes and is EASY to handle. WOW! I wish I had thought of that, but glad you did, Marty. Thanks to all of you for your input.

    And you're right... I am picky. My poor wife deals with me every day. She's the best.
  7. farmer ron

    farmer ron Member

    MSH, we are our own worst critics !!! I agree with the others, there is nothing wrong with your workmanship, it looks good. As far as the low spots fill them in with spackling compound and samd them down as required. As far as color goes, it is a concrete pad where your engine house is going, right ?? I have never yet seen an unstained discolored area that is around an engine shed where there is lots of grease and oil are abound, have you ?? With a few additions of chalks, grease and oil marks, etc it will look just fine. As far as the cracks and chips, look around, the only ones that are near perfect are the ones that have just been poured and even they have flaws.
    No there is nothing wrong with what you have done, just keep going and it will turn out great. Ron..
  8. pcentral

    pcentral Member

    Hi All,
    Here is another product to use. Durham's Rock Hard Putty, it comes in a powder form. Just add water and your ready to go. I have used this for paved areas, road easements, row crops and small hills. It is tan in color when dry but can be painted easily. I use spray paints, but I think you could prime it with artist gesso and use artists paints dilluted with water. I use the later method on my mountains. This method requires no artistic thought, just brush it on and let it dry. If you don't like it go over it again or put the gesso over it and start over.
  9. Drew1125

    Drew1125 Active Member

    If you're having problems with gaps around the base of the building, just pile some junk, &/or foliage to hide the gaps.
    This building had numerous gaps around the bottom, so I just kept adding stuff until I hid them all.

    Attached Files:

  10. shamus

    shamus Registered Member

    msh, leave it as it is, it looks fine to me. Use some chaulks to weather it down a little, and as Tyson stated, use a block of wood for the sandpaper.


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