Whilst cement and concrete are often used interchangeably the two words are not synonyms. Both cement and concrete each distinct materials; the common confusion likely stems from the fact that not only do the two words sound very similar, both are building materials.
Cement is a granular binding powder, made by mixing limestone, calcium, silicon, iron and aluminium which is then heated to around 2,700°F (1,482°C) to form ‘clinkers’ that are then ground and mixed with gypsum which in turn forms the gray-sandy form of cement-proper. Portland cement is the most commonly used type of construction cement as it was developed in England in the 1800s by the mason Joseph Aspdin who, by the tincture, was reminded of the quarries of the English Channel’s Isle of Portland.
Concrete – in distinction – is a mixture of cement and sand and stone into a composition called aggregate. Cement only makes up (typically) a small portion of the total aggregate. The aggregate is then mixed with water, triggering a chemical reaction that makes the cement admixture harden and set, after it sets it assumes the shape of the mold into which it was poured and generally is crafted in heavy blocks or slabs.
Hopefully this will help the aspiring writer avoid mixing up these two similar, but distinct, words.