The cement industry is the largest industrial manufacturing sector in the United States, producing nearly 100 million metric tons of cement in 2012. The U.S. is not alone; other countries produce cement as well.
By far the largest user of cement is construction, building housing and office buildings. The second largest user is agriculture. Cement is used to hold soil together, to stabilize ground, to prevent erosion, and to control water flow so that plants can grow where they otherwise wouldn’t be able to. Cement is also used in road building, concrete production, and it’s important to pipeline construction because pipe must be able to withstand high temperatures without fracturing or collapsing.
Cement produces a number of byproducts that are used for a variety of purposes (e.g., concrete aggregate, fly ash). Cement products are an important part of any home builder’s arsenal because they are widely used in construction for their strength and durability properties.
Cement has been around since about 3000 BC when it was first discovered by accident when a hardened mud was mixed with lime mortar at Pompeii (and elsewhere).
Cement is a material that hardens when it gets wet. There are all sorts of different cement products; the easiest way to think about them is by dividing them into construction-use cements and building-use cements. Construction-use cements are the kind you use to build things, and building-use cements are the ones you use to hold things together. If you’re thinking of buying a new house, you want to buy building-use cements; if you’re thinking of doing some remodeling in your own home, you want construction-use cements.
Cement is a very old product. It was first used for construction in China around 2000 BC. By AD 300 it had spread through India and Europe, and by AD 400 it had reached England and the rest of Europe.
Portland cement is a combination of clay and limestone that gives strength to concrete. It has been made for at least 3000 years, and there are several other types of cement–some good, some terrible.
While any good building material will make the house stronger and last longer, cement is the best. The reason is that cement can be mixed easily with water, so it can be produced anywhere in the world and made into concrete almost as soon as it arrives. That makes it easy to build a home anywhere.
The uses for Portland cement are very broad. Cement is used for concrete–the kind that holds buildings up–and for mortar–the stuff you use to do most of your masonry work like build walls, partitions, stairs, walkways, foundations and patios. Cement is also used to mix with sand and gravel to make concrete for sidewalks or driveways; mixing it with sand gives concrete more strength. “Concrete” is the generic name for all these things.
Americans use about 2 billion tons of cement a year, mostly for concrete. Some of it is used in making bricks and blocks, some for road-building, and some for just about anything else that needs building up.
Cement is the most important ingredient at the bottom of the pile. When you first start building a house, you don’t think much about it: it’s a utilitarian substance that gets its job done. But as you get into carpentry and start to build things like staircases and floors and foundations, you realize that there are lots of choices here: boards versus beams; nails versus screws; glass versus plastic; even whether to use wood or steel. You’ll find out pretty soon that each of these choices has its own set of trade-offs and compromises.
Cement is a combination of clay and sand, bound together with water. The process is called cementation. The resulting mix of ingredients, and the procedures used to make it, differ from place to place.
Cement is used in concrete, where the ingredients are mixed together into a paste and pressed into shape. The paste hardens into concrete when it is exposed to water for a while, usually for about 28 days.
Concrete isn’t just one thing; it’s many things put together. Concrete has strength, flexibility, durability and so on; these qualities depend on the type of cement used, its chemical composition, how it’s mixed and what kind of stone it’s mixed with.
Cement is used for more than just concrete; other products include mortar (mortar is used in masonry), stucco (for walling), plaster (for interior decoration) and asphalt (for roads).
Portland cement was invented in the 19 th century, but it took a long time to establish itself as a staple. It’s still not widely used. Why? Because it’s hard to work with. The result is that building materials stores have a lot of cement, and most people don’t understand what they are buying.
Portland cement is made by reacting limestone and clay with heat (not strictly true – the reaction also releases carbon dioxide and oxygen, which burn off when the mixture is mixed into water). This reaction is called calcination; the resulting product is calcium silicates. The name we call it “cement” comes from another word, meaning “set.” A building material is one that sets as you build it. Portland cement doesn’t set well; you have to mix it with water, sand, or some other additive to make something like concrete.
But why didn’t Portland cement take off? It’s hard to mix right; you have to get the proportions right or your mix will fail. And it costs about $6 a bag of cement for regular Portland cement (which makes about 50 bags per ton), compared to about $1 for ordinary portland cement (about 30 bags per ton).
Cement is a natural mineral that has been used in various forms for thousands of years, but it was the nineteenth-century Englishman Joseph Aspdin who developed modern cementitious materials. Aspdin was particularly interested in the properties of Portland cement, which he first produced in 1840.
Portland cement consists of sand and limestone which have been mixed with a hydraulic binder. Cement’s binding strength is due to hydration (chemical bonding) between the calcium, magnesium and carbonate ions in the lime, along with the silica and alumina (silicon dioxide) in the sand and limestone. The calcium carbonate reacts with water to form calcium hydroxide and carbonic acid, a weak acid. These reactions are exothermic, so mild heat is required to activate them.
The composition of Portland cement may vary considerably depending on what is available locally. The clinker comes from local quarries, where the proportions of sand to limestone are determined by the demand for aggregate products such as concrete blocks or bricks. In many countries, including Australia and Canada, aggregate is produced by grinding up rock at crushing plants into 20-cm-long ribbon-shaped slabs called fines with diameters ranging from 2 mm to 5 cm.
The size of fines used