The gas is fed back over the calcium oxide.

气体被氧化反作用。

Heating this chemical compound drives off carbon dioxide gas leaving calcium oxide.

加热种化合物会驱除二氧化碳气体，留下氧化。

The essential ingredient in cement is calcium oxide, CaO.

中的基本成分是氧化， CaO。

When water enters these tiny cracks, it hydrates the concrete’s calcium oxide.

当进入些微小的裂缝时，它会合混凝土中的氧化。

The heat is applied to limestone, to break up its principal constituent, calcium carbonate, into calcium oxide (cement's crucial ingredient) and CO2.

对石灰石施加热量，将其主要成分碳酸分解成氧化（的关键成分）和二氧化碳。

The essential ingredient in cement is calcium oxide, CaO. We get that calcium oxide from limestone, which is mostly made of calcium carbonate: CaCO3.

中的基本成分是氧化，CaO。 我们从石灰石中得到氧化， 它主要由碳酸构成：CaCO3。

Over time, some CO2 from the atmosphere drifts into all that cement in buildings and bridges, and reacts with the calcium oxide to form calcium carbonate again.

随着时间的推移，大气中的一些二氧化碳漂移到建筑物和桥梁的所有中， 并与氧化反应再次形成碳酸。

Limestone is refined to produce calcium oxide, or quicklime, for cement, in a reaction known as calcination, which releases a lot of carbon in the form of CO2.

石灰石被提炼以生产用于的氧化或生石灰， 在称为煅烧的反应中，该反应以 CO2 的形式释放大量碳。

But in fact, most of the CO2 emissions come not from the heating, but from the breakdown of limestone, which is calcium carbonate, into calcium oxide and carbon dioxide, or CO2.

但事实上，大部分的二氧化碳排放不是来自加热，而是来自石灰石， 也就是碳酸， 分解成氧化和二氧化碳， 即二氧化碳。