Rebuilding a Lighthouse Foundation
By Sue Clark on Aug 7, 2008 in News 
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How To Get Cement To Middle of Gulf?
Last December, Lighthouse News featured a story about Sand Island Lighthouse, Alabama, and how the island had washed away, leaving the light surrounded by the ocean. Between that and Hurricanes Katrina and Ivan, the foundation was crumbling. Work was to start this year, and it has. But the challenge was, how do you get concrete out to the island? Well, between the Alabama Lighthouse Association and the company undertaking the repairs, Remedial Services, Inc., they came up with an unusual way to do so. Haul the concrete trucks out to the island on a barge. Run the concrete from the barge to a wooden “mold” filled with a “metal skeleton” around the base of the tower.
According to the president of the company, John Cain, “We knew coming it was going to be a challenge and we kind of enjoy that. It’s a very tricky project. First of all you’ve got a barge twice the size of Sand Island, and then you’ve got to get the trucks out here before the cement hardens. It’s all an issue of timing. We’ve been working on it for two weeks on the (cement) mix design and hopefully today we got it right.”
Time to set is very important in creating a cement mix to add the the concrete. The addition of sulfur to the mix is what controls setting. Too little sulfur and the cement hardens immediately. Too much and it won’t set properly. It’s thanks to John Smeaton, though, who redid the Eddystone Lighthouse back in the 1800s, that hydraulic cement works as well as it does. He’s credited with coming up with the formula for cement (the part of concrete that holds it together) that will set properly underwater.
The video above is from WKRG.Com News 5. It’s worth watching. Newsletter subscribers, you’ll need to click through to view the video.
Photo Credit: Sand Island Lighthouse by Quiksilver1850 on Flickr.
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1 Comment(s)
By Ken Uracius on Aug 8, 2008 | Reply
The material that Smeaton used at Eddystone lighthouse has nothing in common with the material used at the Sand Island light except the word hydraulic. Smeaton used Blue Lias Hydraulic Lime mixed with volcanic ash when he built the Eddystone light he did not repaired it. The previous light was completely destroyed. His work lead to the discovery that limestone with high clay content heated to the correct temperature would set under water. This contradicted the belief at the time that pure limestone made the best mortar. Most light houses in the late 18th early 19th century were built from this material. The person who should be given credit for the lighthouses in this country was Joseph Totten. Totten’s designs, equipment, and materials were used to build most of the lighthouses built in the US From the middle of the 19th century until the early 20th century. His binder of chose was Rosendale natural cement from Rosendale NY. Again this material has some basic elements that are the same as the Portland mix above and the word hydraulic associated wit it but nothing else.
After 1886 there were some lighthouses built using Portland cement and I guess you could relate them to a modern modified Portland but even that is a stretch. It is amazing to me that our engineers and architects working on these historic structures justify replacing historic material that has performed well for over 100 years with modern materials that has no proven track record.