Reading about Alcatraz Federal Penitentiary I realised that it had a short service life. Built in 1910–12 and closed in 1963.

The most common explanation states that the the high salinity caused by the sea sprays corroded the concrete*. Which looks more like an excuse than a good reason. I know that there are different types of concrete with different chemical responses to the surrounding environment. I know that at the time the qualities of Roman concrete were not known. But how to build with concrete in marine environments was well known. If you look around the world you can find thousands of old harbours whose concrete sea walls and docks are still standing and in decent conditions.

There could be two possible reasons why Alcatraz buildings were rotting less than 50 years from the construction date. An utterly wrong composition of the concrete or a mixture with too much sand and too little cement. I suspect that the second hypothesis is the most probable. Given the overall cost of the whole story and the loss of a valuable location I am wondering if there ever was an investigation into the quality of the construction.

[*] Source is the linked Wikipedia article:

A 1959 report indicated that the facility was over three times more expensive to run than the average American prison; $10 per prisoner per day compared to $3 in most other prisons.[18] The problem was made worse by the buildings' structural deterioration from exposure to salt spray, which would require $5 million to fix.

Major repairs began in 1958, but by 1961 engineers considered the prison a lost cause.

  • Could you cite the source for the most common explanation? I thought that it closed for a mixture of political and economic reasons: the brutality of the regime became notorious, while the high numbers of high-profile inmates, of AL-Capone level have never materialized.
    – Roger V.
    Commented Oct 12, 2023 at 10:58
  • 1
    @RogerVadim It is already cited. It is in the linked Wikipedia article. It mention the quick erosion of the concrete and it also cites as a reason to close the prison the high maintenance cost.
    – FluidCode
    Commented Oct 12, 2023 at 11:00
  • 1
    Government work in the US is typically awarded to the lowest bidder, so it would be neither surprising nor unique if this job ended up being done with suboptimal concrete for the environment.
    – T.E.D.
    Commented Oct 12, 2023 at 13:21
  • "structural deterioration" could also mean deterioration of steel reinforcement (and other metal parts) - the concrete itself might be sound, just allowing leaks to reach steel
    – Chris H
    Commented Oct 17, 2023 at 14:04
  • @ChrisH Did you see the film Escape from Alcatraz? It portrays three inmates digging into the decaying concrete. AFAIK that was also what was in the official report that described the real events that inspired the film. The same is told in other reports about the structural integrity. So, it really refers to the concrete.
    – FluidCode
    Commented Oct 18, 2023 at 15:55


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