Modern civilisation is built on concrete and steel. Put the two together, though, and you can generate a problem.
现代文明是建立在钢筋混凝土基础上的。然而，将两者结合起来，就会产生一个问题。
Reinforcing concrete with steel rods called rebars is the basis of modern construction.
钢筋混凝土是现代建筑的基础。
But because water gets in through tiny cracks, the rebars rust. This causes them to expand, widening the cracks and weakening the concrete.
但是因为水会从细小的裂缝里渗透进来，所以钢筋会生锈了。这会导致裂缝扩大，混凝土变软。
Hence such structures require constant attention and often have design lives of only 60-100 years.
因此这样的结构需要持续的关注，并且其设计寿命仅有60到100年。
That is pitiful compared with, say, the concrete dome of the Pantheon in Rome—which was completed in 125ad and still stands.
这与罗马万神殿的圆顶相比，简直是小巫见大巫，罗马万神殿建成于公元125年，至今仍屹立不倒。
Various ways of delaying or preventing concrete cancer, as this corrosion is known colloquially, have been tried.
人们已经尝试了各种延迟或预防混凝土癌症（腐蚀的通俗说法）的方法。
These include recipes for concrete that is less permeable to water,
其中包括不透水混凝土的配方，
and rebars made from rust-resistant materials such as stainless steel or composites.
以及由不锈钢或复合材料等防锈材料制成的钢筋。
Such approaches work, but they can be expensive. This may be about to change.
这种方法确实有效，但成本可能很高。这种情况可能即将改变。