Living on an island is a constant reminder that almost everything here had to be brought to the island in some form and usually on a boat. The vast majority of the houses, for example, were made from materials from the mainland. Steel beams, lumber, and appliances all arrived here on ferries and barges. It’s kind of incredible.
Thankfully one of the heaviest and most used materials is made right on the island: concrete. And lately, we have seen our share of concrete trucks and pumps as the foundation of our house has finally taken shape. Starting the construction process, I knew very little about it and now, I think concrete is fascinating.
On the podcast 99% Invisible, a guest appeared recently, named Vance Beiser, who had written a book about one of the main ingredients in concrete: sand. The book is called The World in a Grain
and he shared a few of its stories in the show
Concrete goes back to Roman times, or perhaps before. People somehow figured out that heating limestone creates lime, which could be mixed with water to create cement that hardened like rock. When mixed with gravel and sand, it formed concrete. This discovery meant Romans could build structures like aqueducts and multistory buildings. Today, these are still the basic ingredients of concrete.
But then, the Roman Empire fell and concrete seemed to be forgotten. The invention was lost for the next 1,500 years. What brought it roaring back was the great San Francisco fire.
Ernest Ransome, in the mid-1800s, figured out that you could add rebar to concrete to create a very strong and fireproof building material. He built a few buildings around San Francisco with reinforced concrete, but the idea never caught on. Then, the city burned to the ground in 1851 and guess what was left standing? Ransome’s concrete buildings. From that point on, concrete became the building material of the future.
Here on Orcas Island
, we have no shortage of gravel and I’ve heard that our concrete company has its own source of sand. What must come from the mainland is lime, which is ironic, as lime has played a significant role in the history of the San Juan Islands.
After the San Francisco fire sparked more demand for concrete, limestone was discovered in the San Juan Islands and local entrepreneurs went to work. Fortuitously, the limestone was often found near the shore, which made it easy to load the processed lime onto boats for shipment to the mainland.
Like today, the process of creating lime and cement is energy-intensive and involves heating limestone up to 2000(f). To do this, they built lime kilns fueled with wood that burned 24 hours a day. For a while, the San Juan Islands were the biggest producer of lime in the state.