Cement vs concrete: the difference, explained properly

Cement is a powder binder; concrete is the composite material that results once it is mixed with water, aggregates (sand and gravel) and, most often, steel reinforcement. Saying "we're pouring cement" about a slab is loose talk: you pour concrete, made with cement. The distinction is not just vocabulary — it determines what you buy, what you calculate and what you control on site.

Cement: the binder that hardens with water

Portland cement (and its composite variants, like CPJ) is produced by very fine grinding of clinker — itself obtained by firing limestone and clay at very high temperature — with gypsum added to regulate setting. On contact with water, the powder hydrates, sets and then hardens, including under water: it is a hydraulic binder. Put simply, cement plays the role of the glue that binds aggregates together in concrete.

Concrete: a calculated assembly

Concrete typically combines 300 to 400 kg of cement per cubic metre with sand, gravel, water (a water/cement ratio generally between 0.45 and 0.55 for structural uses) and sometimes admixtures. Every component has a function: aggregates form the skeleton, the cement paste coats and glues, water triggers hydration. Final strength depends on dosage, aggregate quality, the water/cement ratio and above all on placing care — vibration and moist curing of at least 7 days.

Why the confusion is expensive

Mixing the two up leads to concrete mistakes. Buying "cement" without computing the required concrete volume means risking a stock-out mid-pour — or the opposite, dormant bags losing activity after a few months. Overlooking the aggregates' share of the cost means believing concrete prices follow cement prices tonne for tonne. And forgetting that concrete strength is decided as much by workmanship as by the binder leads to cracked structures even with excellent cement.

In practice on your site

First compute the concrete volume (length × width × thickness), then apply the dosage suited to the work — 350 kg/m³ for standard reinforced concrete, more for demanding uses — then convert to tonnes of cement with a 5-10% margin for losses. Our online calculator performs those conversions in seconds, and the article on calculating quantities walks through the full method.