Concrete







**Concrete Properties**  Type: Fine-grain concrete Ingredients: Cement, water, small stones **Concrete Pros+Cons** Strengths: Cheap, fireproof and weatherproof, molds to any shape, strong in compression Weaknesses: Cracks with temperature changes, weak in tension **Concrete Applications**  Early arch bridges and domes Example: Pantheon - Rome, Italy

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__1. 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.

__2. Reinforced concrete:__ Was developed to add the tensile strength of steel to the compressive strength of mass concrete.

__3. 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.

__4. 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 contraction

__5. Prestressed concrete:__ Provides bearing members into which reinforcement 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.



__Precast Concrete, Tilt-up Construction and Tiltwall Diference __

Tilt-up concrete have a great deal of flexibility to create buildings. It is submitted by the climatic conditions. When temperatures drop below freezing, curing the concrete panels becomes more difficult and expensive. Tiltwall panels can sometimes be extremely wide and/or tall. The precast concrete addresses the challenges presented by weather. Clearly, tilt-up or tiltwall construction and precast concrete are similar processes. Because tilt-up affords more flexibility, it is the method of choice in locations where the weather allows it. Precast concrete is a suitable choice in circumstances where environmental factors and the construction schedule preclude tiltwall as a viable option.