Duncan wrote:Gareth Thomas wrote:Was concrete ever used on single carriageway A/B roads? I can't think of any locally (East Kent) but perhaps elsewhere?
Ilminster bypass? I don't think many West Country sabristi have posted yet. RichardA35? David Brown? I certainly can't think of any in Sussex. Water authority roads were often concrete for some reason though, and usually heavily jointed. Whether cost was the main consideration, or it was thought to be harder wearing should the reservoir or whatever flood over I don't know.
OK, OK, quick notes on concrete roads as I remember them.
Most older concrete roads were jointed unreinforced (URC) built with fixed form trains with dowel bars inserted automatically and the joints initially sawn at 5 or 6m centres after the initial setting of the concrete (about 8 hours). This accounts for most of the older motorway sections which have now been overlaid M25 SW quadrant, M20, M42 Southern section, Ilminster bypass.
A different set of URC roads was laid by slipforming where the dowel bars were pre installed on small cages and plastic crack inducer was forced into the wet concrete and the concrete revibrated around it. The joint could then be sawn to full depth at a later date. The concrete displaced by this insertion was said by many to cause a small rise in the surface at the joint and that the ride quality was worse than the fixed form trains. This method was pioneered by Alfred McAlpine on the M27/M271, Hawarden Bypass, M54, M42 Kingsbury, A483 Gresford, A27 Havant Chichester.
Continuously Reinforced Roadbase was used on the M40 northern extension - this is CRCP with less reinforcement and little texture.
Continuously Reinforced Pavement was used on DBFO sections such as A35 Tolpuddle, A30 Honiton, Cirencester Bypass, A1-M1 link Leeds, A50 Doveridge without joints and generally maintenance free apart from the occasional burst out. In capital cost the rates per sq. m were generally comparable at the end of the 90's between CRCP and blacktop. As traffic noise became more of an issue whisper concrete was trialled on the A50 Hilton and A13 Wennington. This is a subset of CRCP which has high PSV aggregate in the concrete or upper layer depending on technique. CRCP can now only be used with an asphalt overlay such as on the M6 Toll.
For single carriageway roads, the delivery of concrete to the paver is done from the side so the road needs to be sufficient width to allow a truck alongside his the paver. I have seen it done one lane at once on the dual carriageway A40 Raglan Usk but the Ilminster bypass is probably the narrowest practical width to be done in this way. I have seen a narrower road slipformed but this was fed from the end and was logistically very difficult.
Hope this helps.