Long Lasting Concrete
Long lasting concrete is very easy to make. The best part is it's not that expensive to do.
Long Lasting Concrete Examples All Around
There's a great chance that within fifty miles of your home there's long lasting concrete that's close to one hundred years old. I'll bet it's in great shape. All you need to do to locate some is to find a railroad bridge near you.
Look at the concrete abutments and see if there isn't a date cast into the concrete. It was a common practice to put the date in the concrete.
Yet roadways, sidewalks, driveways etc. near you that may be less than twenty years old are spalling, cracking and generally in bad shape.
What's the difference? Why is newer concrete falling apart so fast?
Waterfall Bridge Concrete Footer Acadia National Park
I hiked to the stunning Waterfall Bridge on the morning of January 28, 2018 while in Acadia National Park.
Two months prior, I had read Ann Rockefeller Roberts book about her grandfather's exploits of building the breathtaking carriage trails in Acadia National Park.
In her book Mr. Rockefeller's Roads, there's a rare photo of the construction of one of the bridges and it shows the giant cast concrete steps or footers that lie beneath the seventeen bridges in Acadia NP.
It's important to realize I had no idea that I'd be able to see any exposed concrete from the construction work. But there it was. The concrete you see in the above photo that supports the first row of granite stones was mixed and cast in 1925, ninety-three years ago!
It's in excellent shape.
The Secret to Long-Lasting Concrete - More Cement
I don't have access to the construction specifications for the concrete in Mr. Rockefeller's bridges. I suspect though that it was an eight or nine-bag mix.
Currently the Portland Cement Association suggests a six-bag mix, or 564 pounds, of cement in each cubic yard of concrete for exterior use. They say this will create a compressive strength of 4,000 pounds per square inch (PSI).
If you're mixing a small amount of concrete and using your own raw materials, here's an ancient formula that you'll see in many publications:
- 3 parts gravel
- 2 parts sand
- 1 part Portland cement
This recipe makes the standard mix that won't hold up like the concrete holding up the Waterfall Bridge above.
I recommend this recipe for long-lasting concrete:
- 3 parts gravel
- 2 parts sand (silica sand or volcanic sand if you can get it)
- 1.5 parts Portland cement
- 0.5 parts hydrated lime
I maintain that you just need to boost the amount of cement in concrete to increase its strength.
It's my opinion that the PCA has a dog in the fight. Their members may want you to replace your concrete more often than needed. After all, this could start a long-term trend that concrete is really a disposable product.
Perhaps it's not in their best interest for concrete to last 40, 60 or 100 years? This is all conjecture on my part, but Mr. Rockefeller's Waterfall Bridge footer is prima facie evidence that concrete can be made that lasts a very long time.
Hydrated Lime Is The Secret Additive
It would also help to add hydrated lime to the mix and use volcanic sand that has a high silica content.
The Romans made mortar and concrete well over 1,000 years ago that's extremely durable. They didn't have Portland cement. All they had was hydrated lime and they must have figured out on their own that mixing it with volcanic sand made for a very durable compound.
Silica is a primary component of granite and you already know how durable it is!
If you want to know how much hydrated lime to add to your concrete, just get this amazing book: