The gas is fed back over the calcium oxide.

气体被氧化钙反作用。

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

加热这种化合除二氧化碳气体，留下氧化钙。

The essential ingredient in cement is calcium oxide, CaO.

中基本成分是氧化钙， CaO。

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

当进入这些微小裂时，它合混凝土中氧化钙。

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，将其主要成分碳酸钙分解成氧化钙（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.

中基本成分是氧化钙，CaO。 我们从石灰石中得到氧化钙， 它主要由碳酸钙构成：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“热混合”。它使用干燥氧化钙，一种也称为生石灰矿质。

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.

随着时间推移，大气中一些二氧化碳漂移到建筑和桥梁所有中， 并与氧化钙反应再次形成碳酸钙。

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氧化钙或生石灰， 在称为煅烧反应中，该反应以 CO2 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，大部分二氧化碳排放不是来自加热，而是来自石灰石， 也就是碳酸钙， 分解成氧化钙和二氧化碳， 即二氧化碳。