David,
There's a number of them on the DLS. I just did a search for concrete slab and found this plus more below which may be useful.
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Description
Put this under the big sheds[/TD]
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[TD="align: left"]Type: Buildings / Structures   |   Version: TRS2004   |   KUID2: <KUID2:50587:11556:2>   |   Filesize: 98.89 kb   |   File Type: .cdp   |   Downloads: 2254[/TD]
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Download Page [/TD]
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Concrete Slab Edge - 
dricketts
9th January 2015
Description
Use this spline as a concrete slab underneath track with concrete abutment and concrete bridge support .
 This is a reskin. Original model by Chris Whiting.[/TD]
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[TD="align: left"]Type: Road   |   Version: TS2009   |   KUID2: <KUID2:135229:100500:1>   |   Filesize: 1.23 MB   |   File Type: .cdp   |   Downloads: 263[/TD]
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Download Page [/TD]
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SAM P - Concrete slabs old TS - 
samplaire
13th July 2014
Description
A stack of old used concrete slabs.[/TD]
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