What is a Concrete made of?
What is a Concrete made of?
Stone and sand glued by cement paste — and it hardens by a chemical reaction with water, not by drying.
Concrete cures rather than dries, and the difference is practical: it will set perfectly well underwater, and keeping a fresh slab damp for a week makes it substantially stronger than letting it dry in the sun. It keeps gaining strength for years, with the 28-day figure being a convention rather than an endpoint. It is also enormously strong in compression and weak in tension, which is why steel reinforcement exists and why cracks appear where a slab is bent. Cement manufacture releases carbon dioxide twice over — from the fuel and from the limestone itself — and accounts for a widely cited 7-8% of global emissions, which is why blended cements using slag and fly ash are now standard.
Component by component
| Part | Material | Why that material |
|---|---|---|
| coarse aggregate | crushed rock or gravel, typically 10-20 mm | Stone is the cheapest, stiffest and most dimensionally stable part; the goal is to use as much of it as the mix will carry. |
| fine aggregate | sharp sand | It fills the spaces between the stones so the expensive cement paste only has to fill what is left. |
| cement | Portland cement — limestone and clay burnt to clinker at about 1450 °C, ground with gypsum | Its calcium silicates react with water to grow interlocking crystals, which is the glue; the gypsum is there to stop it flash-setting. |
| water | clean water, ideally at a water-to-cement ratio near 0.45 | Water is a reactant, and any water beyond what the reaction needs leaves pores behind — which is why a sloppy mix is a weak mix. |
| admixtures | plasticisers, air-entrainers, retarders, accelerators | A plasticiser buys workability without adding water, which is the only way to get a pourable mix that is also strong. |
Other building materials objects
- Glass Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
- MDF Wood pulled apart into individual fibres, mixed with resin and wax, and pressed hot into a board.
- Road asphalt About 95% crushed stone and sand, glued together by roughly 5% bitumen from the bottom of an oil refinery.
- Brick Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
- Mirror A sheet of ordinary glass with a microscopically thin silver layer on the back, sealed under paint.
- Plywood Thin wood veneers glued in alternating grain directions — the cross-lamination is the entire idea.
Common questions
- What is a Concrete made of?
- Stone and sand glued by cement paste — and it hardens by a chemical reaction with water, not by drying.
- What is the coarse aggregate of a Concrete made of?
- Crushed rock or gravel, typically 10-20 mm. Stone is the cheapest, stiffest and most dimensionally stable part; the goal is to use as much of it as the mix will carry.
- What is the fine aggregate of a Concrete made of?
- Sharp sand. It fills the spaces between the stones so the expensive cement paste only has to fill what is left.
Related pages
- Glass Sand melted with soda ash and limestone — three cheap minerals, floated flat on molten tin.
- MDF Wood pulled apart into individual fibres, mixed with resin and wax, and pressed hot into a board.
- Road asphalt About 95% crushed stone and sand, glued together by roughly 5% bitumen from the bottom of an oil refinery.
- Brick Clay and shale moulded and fired until the particles partly fuse — a manufactured rock.
- Mirror A sheet of ordinary glass with a microscopically thin silver layer on the back, sealed under paint.
- Plywood Thin wood veneers glued in alternating grain directions — the cross-lamination is the entire idea.
- Pencil Stationery and paper
- Tennis ball Sport and games
- Banknote Around the house
- Golf ball Sport and games
- Paper Stationery and paper
- Soccer ball Sport and games
Sources
- Typical range compiled from manufacturer specifications — At One Place