Thursday, October 24, 2013

Steel-reinforced Concrete Highway Construction, Iowa Street, Lawrence, Kansas, 10/22/2013

Building a Steel-reinforced Concrete Road

Project: Replacement of pavement along Iowa St Between University Ave and 15th St in Lawrence, Kansas.

Reinforcing steel and its use today in highway construction: a photographic sampler.

Images from October 22, 2013.


Carpenter and Concrete Worker for 9/11 Truth
(There's only one of us so far)
Post #1

As a lifetime construction worker who has had many occasions to cut or demolish concrete, masonry, steel, and steel-reinforced concrete, using hand and light power tools I've long held an intense interest in the mechanism by which thousands of tons of such materials could be turned to a fine dust and grit at all, let alone how they could be turned to dust and grit in a matter of fifteen seconds, as the actually werein New York City's Twin Towers on September 11, 2001.  

Such a process can be seen happening in the archival video records of the destruction of the World Trade Center Twin Towers on September 11, 2001. 
These photos are of essentially the same kind of Portland Cement concrete as was destroyed so quickly on 9/11.  This concrete is slighly denser as it is not designated lightweight as the floors were. This concrete is likely air-entrained; I don't know if such a process was also used on the WTC floors or if their mix contained vermiculite or other additive to cut down density, and therefore weight, a few percent. 
This concrete is not as thoroughly reinforced by steel as the world Trade center Twin Towers floors were. 
However, it is about twice as thick, but without the supporting corrugated steel pans and bar trusses and other steel members  which reinforced and supported the WTC floors.
Thus, while a comparison may be useful for visulaization and general knowledge, ny comparisons  between this highway concrete and the WTC concrete must be limited by these considerations others not listed here.

The photo with the car mirror in the way shows a row of green bars, (which you can also see, in some of the other photos, held by a wire frames or "chairs" in their relative positions) at an expansion joint. 

As is evident in the photograph with the mirror in the way, the pins comprise a mechanical key at seams between adjoining slabs of the approximately 8" thick concrete pavement.  

The green rods emerging from the longitudinal edges of the pavements are of different surface pattern, a smaller diameter, and a greater length than the transverse smooth pins,  

 The smooth pins are about  1 1/4 inch in diameter, while the transverse bars are about 5/8". 
These 5/8" tensile members are corrugated, and meant to hold fast withing the concrete, unlike the pins, which must be allowed to slip under sufficient force in order to provide relief due to possible frost heave, settling of the road as a whole, sideways pressure trying to move the pavement laterally (a hillside, for example, against a road exerts a lot of pressure and will sometimes try to flow and push a road downhill), or any other forces threatening to mis-align the individual large panels or slabs of concrete. 

The 5/8" corrugated reinforcing bars comprise a similar key along the other axis of the slabs at the edges, as can be seen below. 

The longitudinal joint is not meant to slip.  The corrugations will not allow it.

The transverse joint is meant to slip. The smooth surface and parallel alignment of the pins allow it.

I had never seen this particular keying method before , and thought it interesting, so here it is for anyone who wants to learn about this method. 

The photos showing black plastic are of completed, but still "green" or not fully set, pavement sections. 

The plastic keeps the necessary water from evaporating, and results in a harder and well set concrete. 

On the homeowner driveway scale, this used to be done just by sprinkling with a wet broom or other device,to keep the surface damp without washing it off, during the set-up time demanded by conditions. If the surface dries out at all before the whole mass sets, the surface will be weak and powdery - so the plastic is used for both total strength and for surface wear resistance and durability.


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