How I extended the platform at Bulkeley with moulded concrete

Having remodelled the track layout at Bulkeley Station (see How I changed the track plan at Bulkeley), I found the new arrangement allowed me to extend the island platform by the length of an LGB R3 point.

The original platform had been cast in sections using a wooden mould and stone slips for texture (see How I cast a curved platform in concrete).

Having just cast some sheep loads for a couple of wagons in plaster with a PlayDoh mould (see How I cast plaster sheep loads), I thought I'd experiment with Plasticine to create a stonework mould for the new bit of platform.

The first thing in needed was a decent supply of plasticine. I duly ordered three reasonably priced half kilo blocks from eBay. I think they were probably cheaper than normal owing to their lurid colour!

Once they arrived, I then rolled out a sausage around 2.5cm in diameter, and then squashed it flat on an old bathroom tile. I'd measured the required height of the platform to be 3cm so felt the sausage would flatten down to about this width.

NOTE: I placed the blocks of plasticine in from of a fan heater to soften them before making the sausages.

I then cut various widths and lengths of stone blocks into the ends of softwood offcuts to act as stamps.

These were then pressed into the plasticine to represent irregular dressed stonework.

The process was repeated until I had sufficient pieces of plasticine to stretch the length of both sides of the platform. The site was brushed clean and the plasticine pieces were laid out, using blobs of plasticine to hold them in place.

A 3:1 mix of sand and cement was then made, ......

.......... slowly adding water until it had the consistency of thick cream. This was then trowelled into the mould.

I had decided to incorporate some twin core wire so I could later add lighting to the platform (see How I created some gas lights for my platforms - pending).

The surface was left slightly uneven as the irregular edges of the mould made smoothing off difficult. From experience, I know these sorts of inconsistencies can be rectified later ( see below).

I left the concrete for two  days to set to its 'green' state; ie not fully hardened. I then carefully removed the sides of the mould by peeling them away from the concrete, starting with the topmost edges.

I then smoothed off the top surface of the concrete by scraping the surface with the edge of the trowel.

With a flat-bladed screwdriver, I then carved mortar courses in the surface of the platform.

To mirror the existing platform finish, I carved stones only at the edge of the platform.

The new extension was then left for a couple more days to fully harden off.

The stonework edges were the painted with a mix of red and brown cement dyes to simulate the red sandstone of the locality.

I left the centre of the platform concrete coloured. I did speculate on painting it with black concrete dye to represent bitumen, but felt the impecunious PLR would have gone for a cheaper option!

I am quite pleased with the outcome. The main difficulty seems to be keeping the plasticine from bowing. I tried to ensure there was a consistent curve on both sides before pouring in the concrete, but there were a couple of places I missed. Because the mortar courses are quite deep, I was able to slice off the protrusions with the trowel when tidying up the platform surface. I need to tidy up the edge where the old joins the new, but will probably do this with a squidge of concrete applied with the trowel and then textured with the blade of the screwdriver when green.

It has occurred to me that I could use the same technique to create dry stone walling. The plasticine was a bit gritty, but a quick wash in warm soapy water was enough to get rid of most of it before the plasticine was pummelled back into a couple of blobs, ready for the next project.