Concrete Viaduct from castings on Stoneycombe

[Granitechops]

I was asked how I built the viaduct that appeared in this thread in pics forum
http://www.gscalecentral.net/tm?m=27045

It was covered in the thread I did on the track extension started last year, but that has now dissapeared.
So I will start a new thread with details of the viaduct

I was first struck with the castings like these that appeared on Mike's Lazy Grange Bay 2

They also were used by Netty on his canal wharf

 

[Granitechops]

After enquires were made, a mould winged its way south to me, courtesy of Mikes generosity.

the mould looks like its made from Latex rubber, & sits in a wood box to impart stability whilst setting

 

[Granitechops]

I did not have a specific site to use it for, so initially I made some retaining walls with it as it was designed for

 

[Granitechops]

I also made some shorter versions, by making a clip in addition to the mould, without in any way altering it, as it had to be returned on my finishing with it

The addition was basically a dam to stop the concrete infil reaching the bottom of the mould

 

[Granitechops]

And mould filled

bricks & block used to save 'stop' from moving
and bits of hardboard added around the edges to give a thicker casting

Short casting removed from mould

with top coping having stone detail added while still 'green', that was missing in original mould

 

[Granitechops]

I had however had in mind from the start to use it also to make bridge like arches
so I cut some hardboard strips, soaked them in hot water for a while so as to be able to bend them

 

[Granitechops]

Following a similar method, I made a more durable stop board, to limit the height, as I thought that long cast arch piers might fracture.
But added hardboard dams to keep the concrete from entering the archway recesses, thus forming a bridge section, or at least a front

 

[Granitechops]

And mould filled

And hard board extensions removed on curing

 

[Granitechops]

As removed from mould

 

[Granitechops]

However, using hardboard to give a thicker casting resulted in a lip forming at the arch front vis

 

[Granitechops]

As I wanted to add stone work detail on the INNER faces of the arches & follow it around the corner to match up with the FRONT stonework, while the casting was still 'green' or not fully cured, I scraped off the ridge ,till the corner was flush, & then lined up the course work using an old screwdriver, finishing off using an old hard bristle brush

the visual enhancement was well worth the effort

 

[Granitechops]

The first bridge sectionI made had a square top edge, but I thought it might strengthen the joint by adding a recess along top of casting, or even two

 

[Granitechops]

The hardest part of this whole project was having the patience to wait until the castings were set off enough to remove from mould without cracking!!!
AND
then leaving long enough, once tidied up to cure properly before use

 

[Granitechops]

Then, when cured, one could have a try out as to suitable locations

A bridge leading a road up to the yard?

A bridge hiding in the woodlands?

or a causeway with bridge sections striding accross marsh lands or water meadows

 

[Granitechops]

In the event, 6 months later, these castings slotted nicely into an extention I was building, connecting two high planters across a water feature, consisting of a high level creek crossed by the railway before tumbling down a weir into a canal basin

mock up trying out levels, working from track level down.

in this pic you can just see the concrete sub base that the bridge would stand on, which would be underneath the pond liner, so as to try & reduce any settlement of the stucture, which by its nature would be heavy, base reinforced by steel the length of the casting

 

[Granitechops]

Top base added over pond liner

 

[Granitechops]

Cut risers for arches out of paving slab with anglegrider. ( A diamond cutting wheel is much more economical)

dry run, just to check

 

[Granitechops]

And mortar into place

 

[Granitechops]

Mortar bridge section into place & clean up course work across joints

 

[Granitechops]

End on it now looks like this