The gas is fed back over the calcium oxide.

气体被氧反作用。

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

加热这种合物会驱除二氧碳气体，留下氧。

The essential ingredient in cement is calcium oxide, CaO.

水泥中的基本成分是氧， CaO。

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

当水进入这些微小的裂时，它会水合混凝土中的氧。

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（水泥的关键成分）和二氧碳。

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

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

The researchers suspected the key was something called " hot mixing." It uses dry bits of calcium oxide, a mineral that's also called quicklime.

研究人员怀疑关键在于所谓的“热混合”。它使用干燥的氧，一种也称为生石灰的矿物质。

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，大气中的一些二氧碳漂移到建筑物和桥梁的所有水泥中， 并与氧反应再次形成碳酸。

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水泥的氧或生石灰， 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， 分解成氧和二氧碳， 即二氧碳。