Concrete is a construction material composed of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate, water, and chemical admixtures. The word concrete comes from the Latin word “concretus”, which means “hardened” or “hard”.
More concrete is used than any other man-made material in the world. As of 2006, about seven billion cubic meters of concrete are made each year‚Äîmore than one cubic meter for every person on Earth.
Espionage or spying involves an individual obtaining (i.e., using human intelligence HUMINT methods) information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, as the legitimate holder of the information may change plans or take other countermeasures once it is known that the information is in unauthorized hands.
Unlike other forms of intelligence collection disciplines, espionage usually involves accessing the place where the desired information is stored, or accessing the people who know the information and will divulge it through some kind of subterfuge. There are exceptions to physical meetings, such as localised low-frequency broadcasts under the moniker¬†OK:Kana!