ローマ帝国のコンクリート技術
Ancient Romans had a special technique to make very strong concrete. In fact, their concrete is more durable than modern concrete, and some buildings have lasted for over 2000 years. Their secret was mixing "volcanic ash" into the concrete. This made it stronger over time. For example, parts of the Pantheon and the Colosseum still stand today because of this special Roman concrete.
