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A circa 1900 building has a cast cement porch with heavy slab railings about 6" wide. A tenant put county road salt on this one year to melt ice and the result is a slow and steady erosion of the top and now the sides of the cement railing slabs. The chemical reaction comes and goes according to the season but shows up as a black moldy surface in general appearance. This has to be an NaCl (or whatever) reaction with the original chemistry. Now the sides are showing erosion ripples. This process was stoppoed with powerblasting with a soap on one occasion and can be slowed with other stronger bases. I need something more powerful for the type of chemical reaction. With a bit of lapping I should be able to restore the sides to a solid finish.

Incidentally I spend a lot of time lusting after old cast concrete stairs, walls, and rail platforms when I can find them. I note there is a yellowish color to the material used around 1900 or so and a different component mix is visible when some of the surface finish wears off heavier structural mixes. A lot more river bed stone seems to show up as opposed to sharper edged gravel found in supply yards today. The only thing more rewarding than analyzing old historic concrete survivors is maybe finding some old wagon docks still in place. Are there any writings on old concrete mixes and their strengths or long term suvivability?
 
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