Could be. Per the article swehner linked to (https://news.ycombinator.com/item?id=10140279), they're making their own concrete as well, which makes sense when they need to pour that much and it has to be of such quality, to keep salt water away from the rebar for 100 years. Also mentions that the mix has to be kept in a very narrow temperature range, "7.7 degrees C (14 degrees F)", which has to be difficult in Panama.