[MassHistPres] Pea gravel paving

[Dennis De Witt]

Michael

Perhaps the chip seal is technically superior but what I've seen of  
it looks like a different version of macadam -- maybe I'm visualizing  
the wrong thing.

What was special about this was the generally rich honey tan color of  
the pea gravel.  This was in the midwest where, no doubt there were  
vast quantities of glacial outwash from which it was mined, but I'm  
not convinced it was done for cost.  The town was Winnetka --  
comparable, say, to Wellesley.

Incidentally, the steam roller really was one -- coal fired, it  
looked like a slightly smaller version of the steam engines that then  
still ran thru town.

The next town over had (and still has) yellow brick streets.  And in  
those days the bricks were periodically (once a decade?) turned for  
uniform wear -- much as one used to see the pavers in European cities  
being turned.

Dennis

As you are a highway person, another midwestern memory is rural "slab  
roads".  The road was the one lane width of a concrete paving machine  
and you approached oncoming traffic head on, with each driver at the  
last moment getting one set of wheels onto the shoulder to pass.


On Jan 26, 2007, at 10:31 AM, Ruderman, AMichael wrote:

> Asphaltic alluvial gravel pavement (pea gravel paving) used to be  
> popular for low-volume roads because it was so cheap. The stones  
> themselves were too small for efficient crushing in the maws of  
> standard equipment, and too uniformly smooth to "resist deformation  
> within binder"; that's highway engineer-speak for the tendency of  
> marbles to roll, even when embedded in a layer of solidified  
> asphalt. Post-war quarries in the building boom considered pea  
> gravel almost as a waste product, nearly more expensive to move  
> than it was worth. Of course, it works great for drainage, and it's  
> getting a new life in minimal-runoff road edge design (as it loses  
> popularity as a playground base, because you can't navigate it  
> without two able legs).
>
> "Chip seal' is the modern equivalent. The "chips" are the stone  
> aggregate, relatively small and uniform, so that they will "lay  
> down" smoothly in a very thin layer of asphaltic binder, but with  
> enough sharp edges to lock up and resist deformation under traffic  
> load. It renews the surface of a road when the road base and  
> subbase are still performing adequately. The paving contractors can  
> customize the formula of aggregates, binders, admixtures, as well  
> as the manner of "the pour" (that's what they call it) to give the  
> customer a variety of surface appearances.
>
> Michael Ruderman
> Arlington Historical Commission
> (day job: Mass. Highway Department)