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Unformatted text preview: C E M 6 2 C o n s t r u c t i o n M e t h o d s CEM 602 Construction Methods Lecture 14 Concrete Construction 1 L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Background 2 L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s History of Concrete • Predecessor of Portland cement was discovered by the Romans in ancient times. • Knowledge was lost after the fall of the Roman Empire. • Concrete was rediscovered in 1700’s in England with the patent of Portland cement. • Reinforced concrete developed in 1850’s. • Prestressed concrete science developed in 1920’s. L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n 3 C E M 6 2 C o n s t r u c t i o n M e t h o d s Cement and Concrete • Concrete consists of – Portland cement – Aggregates: fine and coarse – Water • Concrete chemically hardens through a process called hydration. • Hydration creates heat as a byproduct. • Concrete does NOT “dry”– concrete “cures”! L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n 4 C E M 6 2 C o n s t r u c t i o n M e t h o d s Types of Cement • I Normal (common) • IA Normal, airentraining (air) • II Moderate resistance to sulfate attack (water) • IIA Type II with air • III High early strength (precast or fast construction) • IIIA Type III with air • IV Low heat of hydration (used in dams) L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n 5 C E M 6 2 C o n s t r u c t i o n M e t h o d s Airentrainment • Microscopic bubbles in concrete • Enhances resistance to freezethaw action • Used in pavements • Used in foundations • Used where concrete will be exposed to the weather L e c t u r e 1 4 C o n c r e t e C o n s t r u c t i o n 6 C E M 6 2 C o n s t r u c t i o n M e t h o d s Aggregate and Water • Must not contain dirt or chemicals hazardous to the hydration process or reinforcing. • Must be small enough to fit between reinforcing. • Should be wellgraded. • Strength of concrete is affected by aggregate strength....
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 Spring '10
 AmrKandile
 Concrete Construction

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