Cast a Concrete Loading Dock
by Bruce Petty
Modern concrete loading docks replace many of the railroads freight station's aging wooden loading docks.
For a little modeling fun, I used the same prototype method pouring real concrete, Dap Concrete Patch.
The size of the concrete loading dock is 15 feet wide and 30 feet long. The ramp is 15 feet long. The prototype concrete docks used wood boards. Evergreen styrene V-Groove sheet of .040 thick were cut to be 5 scale feet wide, this includes an extra 1/8" for the height of the flex track. On the inside of the form will be the mortar lines of the V-Grooved sheet having simulated boards 9-10 inches wide. This will be seen in the finished concrete model with the concrete forming extended joint lines in the boards. Smooth sheet styrene is used to make the deck and the ramp.
A left over piece of styrene from cutting the ramp sides was cemented to the bottom of the mold for support and to keep it level.
The styrene mold was designed to open so the finished concrete casting can be removed easily.
Blue Painters tape is used to hold the styrene mold parts together and is easily removable.
For a mold release, a little bar soap and an a stiff brush used to coat the inside mold surfaces. Make sure the corners and grooves are soap coated too.
I had experimented with mixtures of Dap Concrete Patch and Hydrocal and found that a 50/50 mix seemed to work best. I liked the color and the finish of concrete when cured. Measure out the materials using a measuring cup. Mix the two together dry crushing any clumps. If this is not done, clumps of white hydrocal may appear on the concrete. Add very little water at a time, it does not take much. The concrete should have viscosity of thick gravy when the mixture is poured into the form.
NOTE: Dap Concrete Patch is a finely granulated concrete material, when used by itself,
it does not fill in fine mold details and has a little darker or green concrete look.
The fifty percent mixture with Hydrocal allows filling of small mold corners
the mixture also lightens up the color of the concrete to a more lighter natural aged tone.
After the pour, use some sort of an electric vibrator tool to remove air bubbles. I used the point electric engraving tool on the outside mold styrene. Make sure the mold is setting level and don't poke at it for the next 48 hours. I mean it, don't open even when it looks dry, or heat up the mold trying to speed curing time. It needs 48 hours to cure!
Now forty eight hours later; remove the blue tape from the styrene mold and carefully work the concrete casting out of the mold. Use rough emery paper face up on a flat surface to flatten the base of the loading dock. Be careful while sanding not to put too much pressure on the ramp causing the tapered edge to chip.
Look close and see how the mold lines are formed and some broken out looking like its prototype.
Make realistic concrete tunnel portals, retaining walls, bridge abutments and more with this simple reusable styrene molding method.
These two cast docks are setting to see how thy fit in with the scene. To finish the dock scene, brush fine dirt around the concrete base as seen in the first picture of this article. I have made five concrete docks so far using this styrene mold method without damage.
During the casting process you might end up with some poor quality castings, however don't throw them away.
Have extra concrete leftover after the pour? Then pour the extra on wax paper and let cure.
Break up the casting in what railroads call Rip-Rap used along the right-of-way for extra embankment stability.
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