The concrete Roman arch concrete bridges are fascinating structures. When Henry Flagler was queried about how he was to build so many bridges over the ocean, he replied to the effect, "Well, I will build them one arch at a time." For the purpose of this web site I have separated the construction into two pages. Henry Flagler in effect did the same. The support piers were built first and the arched structure built on top of the piers.

     This was far more complex than the following five photos will explain. To begin with, anything can be built of concrete for which forms can be built. The concrete hardening process is a chemical process - not air drying - therefore will harden under water. Forms, called cofferdams, were built and anchored to the ocean floor. The mud and loose residue were pumped out and wooden piles driven to anchor the mass to the ocean floor. A special strong mixture of "Alsen" cement was poured through a funnel like apparatus to form a seal around the bottom of the cofferdam. Then the water was pumped out and the form filled with a regular mixture of the Alsen concrete mixture with the steel rebar held in place. When hardened, the forms were removed and reused. This process was repeated many times. Alsen cement was a Belgium cement similar to our Portland cement. Tests revealed that Alsen was better for under salt water use. The mixing process was the same as with any concrete. The aggregate rock was shipped in form New England states, that is coral rock was not used in the concrete mixture.  Now to the images.