Concrete

**//Post-reading activity No. 2

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Concrete: ****// 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.



//**//Reinforced concrete: **The metal is embedded by being set as a mesh into the forms before pouring, and in the hardened material the two act uniformly. The combination is much more versatile than either product. It serve not only for constructing rigid frames but also for foundations, columns, walls, floors, etc. and it does not require the addition of other structural materials.

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Concrete-shell construction: **Permits the erection of vast vaults and domes with a concrete and steel content so reduced that the thickness is comparatively less than that of an eggshell.

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Precast-concrete construction: **Employs bricks, slabs, and supports made under optimal factory conditions to increase waterproofing and solidity, to decrease time and cost in erection, and to reduce expansion and contractions.

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Prestressed concrete: **Provides bearing members into which reinforcements is set under tension to produce a live force to resist a particular load. Since the member acts like a spring, it can carry a greater load than an unstressed member of the same size.**//