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[SEAOC] Re: [SEAOC] Durability of Lightweight concrete

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>The question is, how durable is lightweight concrete to tire traffic? 

The durability of a concrete surface is somewhat coplex. It contains of 
durability against chemical and physical enviroment. To produse a 
lightweight concrete you exchange the coarse aggregate (maid of solid rock) 
with special aggregate (normaly extruded clay - burned clay with airbubbles 
inside) The clay-based aggregates have significant less durability then 
ordinarry aggregates - both against physical and chemical enviroment. This 
is then transfered to the concrete. Due to this it is not recomended to use 
lightweight concrete on surfaces exposed to significant physical/chemical 
enviroment (road-pavement, industrial floors, harbours etc.) without 
        a: treate the surface with some special admictures etc.
        b: put a stronger material on the surface

>When durability of lightweight concrete is discussed, resistance 
>to freeze/thaw cycles is usually all that is addressed.   

This is normal in the research community, cause you seldom use lightweight 
concrete on "industrial" surfaces (see prev. chapter) What you has left is 
normal weather exposing, and there freeze/thaw is the major problem (at 
least in some parts of the world)

>Any thoughts out there on the
>durability of lightweight concrete to tire traffic?  

Poor!

>The vehicle is comparable to a car or truck.  Is it a common practice for 
bridges that
>use lightweight concrete to use it for the wearing surface?  

NO. I have newer heard of any lightweight concrete bridge that uses 
lightweight concrete as pavement. They either use normal aggregated HPC 
(High Performance Concrete) or bitumen-based pavement (asphalt). 
If the wersicle traffic is not to high, it may be considered to use wood as 
pavement.

PS! If you use concrete-pavement on top - are You sertain that the bridge is 
constructed to bear the force of concrete-pavement and vercicle?

Regards:
OEyvind Saeter
____________________________________________________________________________

Mr. Øyvind Sæter    (Alternative: OEyvind Saeter)
M. Sc. in Civil Engineering - Structural Analysis and Concrete Technology.

Email: oes(--nospam--at)pvv.ntnu.no
WWW  : http:\\www.pvv.ntnu.no\~oes

Disclaimer:
  Information in this EMail has nothing to do with NTNU, PVV or my employer.
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