Tweet from Businessweek (@BW)

Businessweek (@BW) tweeted at 11:35 AM on Sat, Jun 29, 2013: It took 2,000 years, but scientists have finally discovered the secret behind Roman concrete | http://t.co/AITPEo3hy6 (https://twitter.com/BW/status/351016064693444611) Get the official Twitter app at https://twitter.com/download