Patología en estructura de hormigón
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[EN]Despite being thought of as a modern material, concrete has been in use for thousands of years. Lime-based hydraulic cements (those set by chemical reaction with water) have been in use since Roman times, and examples of ancient mortars (cement and aggregate) still survive today. The word concrete comes from the Latin concretus, which means mixed together or compounded. The use of concrete has changed dramatically over the last 100 years as our understanding about the material and how it is made has improved. The industry continues to evolve today as experience grows and its versatility and cost-effectiveness is exploited. Concrete is made up of aggregates of various sizes, broadly categorised as fine (commonly sand) and coarse (typically crushed stone or gravel), combined with a cement paste (a mixture of cement and water) which acts as binder. Concrete is very strong in compression at relatively weak in tension. To overcome this deficiency when concrete is used as a structural building material, and to combat early shrinkage and control subsequent diurnal thermal expansion and contraction, reinforcement (historically iron and later steel) is included in areas where tension occurs to create reinforced concrete. Steel and concrete have similar coefficients of thermal expansion and form effective composite section. Reinforced concrete is a manufactured material, produced either in a casting yard (in the case of precast concrete) or, more commonly for buildings, it is site-made (when it is known as in situ concrete). Building pathology is a term used to describe the holistic approach to understanding buildings. It is based on the principle that to repair and maintain a building effectively, a detailed understanding is required of how it was designed, constructed, used and changed, and how the particular environmental, material and structural conditions have affected it.