Concrete is a plastic liquid, made of aggregate, water and cement. This substance is used in nearly every structure today, but not everyone knows exactly what goes into the common mixture. Even thousands of years ago, the Romans were familiar with the process and used concrete often in their construction. Use of concrete was infrequent after the Roman Empire fell until it was rediscovered in the 18th century. Many people these days often confuse concrete with cement. The truth is that cement is one of the ingredients in concrete. There are many different recipes for concrete, but the basics do not change much.
Aggregate means sand, gravel or other hard materials. These ingredients are essentially glued together with cement. A good mix will use aggregate whose particles are clean, strong and hard. These particles should come in a wide variety of sizes and should not have coatings of fine materials, like clay or dust. The aggregate also should not have any chemicals absorbed into it as the chemicals could potentially cause the concrete to break down faster.
The kind of cement used most often in concrete is Portland cement because it is a hydraulic cement, which means it hardens by reacting with water and forms a water resistant product. This type of cement can even harden underwater regardless of the water content of the concrete mixture. Other non-hydraulic types of cement need to be kept moisture-free to retain their structure as they air-dry and remain water-soluble.
Of course, there are many kinds of additives that can change the texture of your concrete mixture. Innovative recipes can help contractors pour and finish concrete, even in extreme weather conditions. Fly ash, plasticizers and accelerators can influence the mix by forcing it to harden faster. There is simply no substitute for the right climate conditions, though, so if you are planning to work with concrete, you should cooperate with the weather.