4mm Podimore: Brutalist Vernacular - modelling poured concrete: colouring?

Discussion in 'Layout Progress' started by AJC, 20 July 2018.

  1. AJC

    AJC Western Thunderer

    I quite agree - there's something nicely brutal about them. I was basing the angles on the structures on the Fawley branch which I've seen quite a bit of cycling around that area and they seem in line - the pour follows the shuttering of course . You can see this here: Google Maps and here: Google Maps (New Road, Hythe).

    This bridge at Ketton is slightly different (it's all concrete for a start) but again, the angles aren't so different: Ketton Fowler

    Adam
     
  2. Pencarrow

    Pencarrow Western Thunderer

    Hi Adam,

    Liking the bridge and agree with others that concrete is an under-modelled medium.

    Just be sure to add a bit of texture and horizontal lines to take away the flatness of the plasticard...

    iMarkup_20201023_073110.jpg

    Note that the bridge wouldn't have been poured in one hit but in a series of 'lifts'. The red lines are the construction joints marking the level of each individual pour which would have been left to set between pours.

    Note how, in this case, the joints weren't prepared very well before the next pour (or there's been post construction movement or a lack of compaction during the pour) - there's a nice amount of seepage and staining showing.

    You can also introduce a slight colour variation between pours, particularly if it was mixed on site, as the control of ratios of cement and aggregate could vary in each mix.

    The green lines are the impressions left from the planking used to form the shuttering. No staining as it's a surface flaw rather than a joint, but there is a mismatch in levels.

    Looking forward to see how this progresses.
     
  3. AJC

    AJC Western Thunderer

    Thanks Chris, that's really helpful. Modelling the Southern, concrete is a medium that is quite hard to avoid!

    Thank you too for the observations on texture; I think that in 4mm it's quite easy to overdo this but I am keen to replicate the lines between pours and apparent from the shuttering; back when commuting was a regular feature of my life walking past the various Lasdun buildings on the South Bank showed this very clearly (and as a graduate of University of East Anglia, I've spent years of my life around similar buildings!).

    These bridges aren't quite as refined, of course but my thoughts at this point revolve around a mixture of scribing and induced texture using layers of paint. The bridge will be assembled in situ. So the plan is a bit of base texture, followed by primer. Then I'll mask some horizontal - or nearly horizontal - lines and add a coat or two of filler primer before final painting which can introduce all the interesting colour variations. I'd go and look at some of the local pillboxes for a guide, but most of the accessible examples round here used brick shuttering...

    All food for thought, thank you.

    Adam
     
    Last edited: 23 October 2020
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  4. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    It's probably one of those things which is not generally realised is that concrete has been around for some time and not a just a 'modern' 1960's thing - when it became more widespread and therefore noticable.

    I was recently looking at WWI pillboxes and realised some of these were built from concrete.
     
  5. AJC

    AJC Western Thunderer

    Yes - not that many First World War examples left of course which adds to their obscurity. But there are lots of early (modern) concrete structures. The Calstock viaduct (1908) was first listed just over 50 years ago: CALSTOCK VIADUCT, Calstock - 1138329 | Historic England but that’s later than Glenfinnan (1897). There was quite a craze for the stuff at the turn of the 19th century and those are just the big obvious ones: lots of smaller structures were made from the same thing. The Romans got there first (Ok a different sort of thing but still).

    Adam
     
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  6. adrian

    adrian Flying Squad

    Why is it little innocuous remarks like this send me down the various t'internet rabbit holes. The obvious well known mass concrete structure is the Glenfinnian Viaduct - which led me to this little publication - Short Guide: Historic Concrete in Scotland Parts 1-3

    Publication | The Engine Shed | Part of Historic Environment Scotland

    Apparently Glenfinnian Viaduct is predated by the Falls of Cruachan Railway Viaduct built in 1880 with concrete arches.
     
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  7. JimG

    JimG Western Thunderer

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  8. Pencarrow

    Pencarrow Western Thunderer

    Two very different uses of concrete there.

    Calstock used concrete blocks, which were cast on site, in lieu of but, in the same way as stonework.

    Glenfinnan used concrete mixed on site and poured into shuttering to form the pier and arch shapes.

    The Bude branch also had 2 concrete block viaducts. Derriton and Holsworthy. Info about the former here:

    Derriton Viaduct.

    I did find these structures interesting and different so, when we started building Treneglos 18 years ago, I used them for inspiration:

    Treneglos_Feature_18.jpg.d9cae0b6f214b78341e014aaa07bce6e.jpg

    Treneglos_Feature_05.jpg.d6dd815de867fade360ba33182ba4fb0.jpg

    Treneglos_Feature_01.jpg.ae9d9cb2d46a6374e47f9b867e7c9065.jpg
    All taken by Andy York for BRM.
     
    Last edited: 24 October 2020
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  9. AJC

    AJC Western Thunderer

    Thanks Chris for reminding me of the images of the construction of Calstock, blocks and all, that I'm all to well aware of, had seen and should have remembered... Lovely viaduct by the way.

    Anyway, here's my first efforts at adding a bit of texture to my bridge abutments. I had to fill one or two of the joins and, as is always the case there was Milliput left over, the masking tape was on the desk and...

    Bridge_003.jpg

    Obviously, they'll be evidence of more pours which I'll add by scoring and if it looks terrible, it'll sand off. The technique - if that's what it is - involves adding a bit of tape and then slavering a bit of watered down Milliput over the edge. Remove the tape and repeat. I had the presence of mind to vary the application of putty over the upper or lower edge and we'll see what it looks like under a coat of primer. Here's a close-up.

    Bridge_004.jpg

    The few random splodges are deliberate and should replicate a bit of flaked out aggregate or settling. Fingers crossed.

    Adam
     
  10. Pencarrow

    Pencarrow Western Thunderer

    I think thank will turn out nicely Adam. A bit of talc sprinkled on the wet paint and then lightly brushed off also adds texture.

    IMAG7608.jpg

    IMAG7610.jpg

    I find concrete quite difficult to get the colour and texture right.
     
  11. Osgood

    Osgood Western Thunderer

    You simply cannot discuss the use of concrete without acknowledging the contribution of William Marriott, a true pioneer of the use of concrete in all things railway.
    His concrete works at Melton Constable, powerhouse of the M&GN, turned out all manner of civil and architectural items some considerable time before the Southern went all Art Deco and porridge.
    3320BF2C-97F4-41FE-A004-31CA1F020F40.gif
     
  12. John Duffy

    John Duffy Western Thunderer

    There was of course the legend of the horse and cart falling into and ultimately forming an integral part of the viaduct. This was disproven in 2001 when it was confirmed that the incident had indeed happened but not at Glenfinnan. It had instead occurred at Loch nan Uamh Viaduct, also a mass concrete structure on the line. It is commemorated by a plaque.
     
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  13. garethashenden

    garethashenden Active Member

    Not modelling specifically, but do you have a copy of Southern Nouveau - And the Lineside? I recommend it strongly to anyone modelling the Southern. Lots of prototype drawings and pictures of all the lineside features one would need.
     
  14. AJC

    AJC Western Thunderer

    Right, a bit further on. Here's the left hand abutment after a coat of primer:

    Bridge_005.jpg

    I think the effect of the layering is best described as 'subtle'!

    Bridge_006.jpg

    And here with everything painted and prior to final assembly and weathering. The additional colouring allied to the texture looks pretty good at this stage, I think. Obviously it's all a bit clean and tidy but that will change...

    Adam
     
  15. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Looks good. The weathering - water stains, algae, lichens, leeching salts and even rust if the concrete has been cracked or a reinforcing bar exposed - will enhance it.

    I visited the Leeds Dental Institute (next to the LGI) earlier in the year and photographed this piece of weathered concrete wall for my files. And noticed the rust stains being carries across the path.

    LGI 02.jpg

    LGI 03.jpg

    LGI 01.jpg
     
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  16. AJC

    AJC Western Thunderer

    Thanks Dave. I hope so - getting the basic concrete colour I was after took several goes with acrylics and enamels... I've been studying pictures and refreshing my memories from seven years around the University of East Anglia (including a very interesting presentation on the conservation of concrete structures that was part of my induction as a member of staff!). The important thing is to think about how a structure of the relevant age would weather. I don't imagine this as an old bridge, perhaps 15 years old, but they'll be a fair amount of rust streaking from the girders and evidence of lichens, algae, etc., and the galvanised parapet will be starting to get a bit tired.

    Adam
     
  17. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Of course, I remember how stark the original M1 bridges on the southern section were when new. A nice design - a few really deserve a listing status, if they have not already, otherwise they will all be lost due to carriageway widening.
    I'll be looking forward to seeing the weathering progress.
     
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  18. ChrisM

    ChrisM Active Member

    Very nice!

    What’s the intention for the parapet walls? Shuttered concrete or corrugated metal sides (which will look very industrial!)

    Chris
     
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  19. AJC

    AJC Western Thunderer

    Corrugated metal - the bridge over the throat of Yeovil Town was like that, decades after the railway closed and the accompanying footbridge was taken down (which is, obviously, the only way I ever knew it!). For quite understandable reasons when they replaced the bridge deck a few years ago they redid the parapet in box section steel. I've modelled it as unpainted galvanised sheet on creosoted timber with a little rust and soot. The Yeovil Town example was painted green, of course, but they'll be a lot of green about so the contrast is deliberate.

    Adam
     
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  20. AJC

    AJC Western Thunderer

    That observation has sent me checking the National Heritage List for England which reveals a marked lack of listed motorway structures (barring a few of the more interesting service station buildings). That might seem odd - and given the age of, say the original Preston bypass structures - is a bit surprising but reflects the way Historic England works: with the Great Western Mainline for example, they tackled the whole route as a project when bits were under threat and needed to be better understood and protected prior to electrification. If that's come to public attention at all it's down to the Sydney Gardens in Bath and that otherwise unremarkable bridge at Steventon in Oxfordshire.

    Something similar happened with Cold War structures round about 2000 and interwar and post-war public houses more recently (my colleague, Matt, was involved in the latter and has since moved on to gas industry infrastructure). A major change like that is less likely on the motorway network but will happen eventually - it may be on the horizon on the M1, I have no idea - and it's then that HE will step in. If you check the sheer quantity of listed buildings and scheduled monuments it's not surprising that HE is a bit reactive.

    Adam