Concrete

=__**//Concrete. //**__= = = 

It is a manufactured mixture of cement and water, with aggregates of sand and stones, which hardens rapidly by chemical combination to a stonelike, water-and-fire-resisting solid of great compressive but low tensile strength.
 * - Definition of concrete:**

· Cheap · Not too heavy · Fireproof · Weatherproof · Mold to any shape · Strong in compression · Crack with temperature changes · Weak in tension · Used for early arch bridges and domes
 * - Some characteristics of concrete are:**

· Concrete shell construction: is a structure composed of a relatively thin shell of concrete, usually with no interior columns or exterior buttresses. The shells are most commonly flat plates and domes, but may also take the form of ellipsoids or cylindrical sections, or some combination thereof. · Precast concrete construction: is a form of construction, where concrete is cast in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. · Reinforced or Prestressed concrete: is Portland cement concrete in which steel reinforcement bars, plates or fibers have been incorporated to strengthen the concrete in tension. Portland cement Concrete is very strong in compression, but weak in tension, thus adding such steel reinforcement bars, plates or plastic fiber increases the strength in tension.
 * - Meaning of the highlighted expressions found in the text posted in moodle:**

Croncrete shell
 * - Some images:**

Reinforced or Prestressed concrete

Precast concrete

Tilt-up and tiltwall are two terms used to describe the same process. For a tilt-up concrete building, the walls are created by assembling forms and pouring large slabs of cement called panels directly at the job site. The precast concrete building process is similar to tilt-up construction, but for precast concrete buildings, work crews do not set up forms at the job site to create the panels. Instead, workers pre cast concrete panels at a large manufacturing facility. The precast concrete forms are poured indoors.
 * - The difference between tiltwall construction, tilt-up panel construction and pre-cast concrete construction:**