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

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I was able to attend the symposium mentioned below.  It was extremely 
informative. The suggested report is an excellent reference, well worth 
the effort to obtain.  One of the speakers in particular had extensive  
first hand experience with L/W 
concrete in bridge/traffic wear situations. He is

Thomas Holms, PE
Richmond, VA

(no he's not my father-in-law)        
Additionally if you can get a copy the symposium notes, do it.
just  my $.02
R. Kazanjy
On Mon, 9 Sep 
1996, Powers, Tony wrote:

> Our experience in researching lightweight concrete durability was similar to 
> yours.  The literature on tire-wear durability is inconclusive.  However, 
> there appear to have been many successes using lightweight concrete for 
> exposed bridge decks, even though many others were built with AC or normal 
> weight wearing surfaces.  We were convinced enough to specify lightweight 
> concrete with no additional wearing surface (there is a 15 mm integral 
> wearing surface assumed for design) for a 690 meter cast-in-place concrete 
> box girder bridge over the American River (Folsom, CA) to be bid next March. 
>  Caltrans is also planning on using lightweight for the new Benicia- 
> Martinez bridge, although I'm not sure if they are using it exposed.
> Some questions come to  mind for your case:
> 1.   Do you know the concrete strength, type of lightweight aggregate 
> (natural or manufactured), and if the fine aggregate was also lightweight? 
>  These may give some indication of the wear-resistance to be expected.
> 2.   What is the current condition of the beamway after 30 years?
> 3.   How much would it cost if it was necessary to overlay it later?
> Not knowing the answer to these questions, my feeling from reading the 
> literature is that there is no reason to assume that the performance would 
> be worse than for a normal weight overlay. It seems to depend heavily on the 
> type of aggregate used.
> A good place to start if you don't already have it:
> FHWA Report No. FHWA/RD-85/045, "Criteria for Designing Lightweight Concrete 
> Bridges", August, 1985.
> Finally, if you happen to be in Sacramento tomorrow (Sept. 10) there is an 
> "International Symposium on Lightweight Concrete Bridges" sponsored by 
> Caltrans and Pacific Custom Materials (a lightweight aggregate 
> manufacturer).  You could probably get a set of proceedings from:
> 715 N. Central Ave., Suite 101
> Glendale, CA
> 818-240-5160 
> Tony P.

> From: seaoc
> To: 'seaoc(--nospam--at)'
> Subject: [SEAOC] Durability of Lightweight concrete
> Date: Thursday, September 05, 1996 3:56PM
> I have a 30 year old lightweight concrete beamway in an amusement park
> that was never intended to bear direct vehicle traffic.  The ride that
> has now been removed ran on a steel rail bolted to the beamway.  The
> proposed vehicle will ride tires directly on the lightweight concrete.
> The question is, how durable is lightweight concrete to tire traffic?
> The prevailing wisdom from the literature that I have investigated (ACI,
> PCA, etc.) is muddled at best.  When durability of lightweight concrete
> is discussed, resistance to freeze/thaw cycles is usually all that is
> addressed.   At present, I have specified a cement-based overlay on the
> wear surface, but this is no small cost.  Any thoughts out there on the
> durability of lightweight concrete to tire traffic?  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?  Any good
> references that address this question?
> ...
> ...