History of

• Concrete was first seen in ancient Rome. Romans used a type of concrete that was made up of quicklime, pozzolanic ash, and pumice. It was used in many Roman buildings, but after the fall of Rome, the art of making concrete was lost until 1756. At this time, the engineer John Smeaton used hydraulic lime in concrete, along with loose pebbles and powdered brick to create cement. Today, concrete is made with added chemical properties that increase the strength, elasticity, or other properties that specific concrete may need.
  
  

Type

• There are many types of concrete and each one is made up of different components. Some types are named by their function, such as high-performance concrete, high-strength concrete, or self-consolidating concrete, which eliminates the need to be compacted to fit a space it's poured into. Other types of concrete are named because they have a unique material in its composition, usually as an aggregate. Examples of these are glass concrete, cork concrete, and rubberized concrete.
  
  

Time Frame

• The time it takes for concrete to set, dry, and harden depends on the type of concrete used and other factors, such as the amount of water that has been added to it and the percentage of cement in the mixture. For the most part, concrete will begin to set between 2 and 7 hours after adding water to it, at which time it should have already been poured and smoothed. After a couple days, the concrete will be safe enough to start to build on, but the concrete will continue to strengthen and harden over the next month or so.
  
  

Benefits

• Concrete is extremely beneficial as a construction material, because it greatly reduces the risk of harm in a building that is made of it. Concrete does not break down quickly over time, which is why so many ancient Roman structures are still standing in very good condition today. While materials such as wood are plentiful and have been used to make buildings in the past, they tend to break down, rot, and fall into disrepair overtime. Concrete is also much stronger than wood and most other building materials, and it is very cost-effective for the strength it offers. While metal is stronger than concrete, it is much more expensive to use for construction purposes.
  
  

Risk Factors

• While concrete is certainly a very strong material, it can be harmed and broken if in some ways. If exposed to fire or seawater, concrete is likely to corrode, though seawater is a much more likely culprit. Unless concrete is protected by this with a special coating, it will be ruined. Carbonation, chlorides, and other chemicals will also damage concrete. It is important to understand just what can damage concrete by in order to be able to keep it from these corrosive entities.