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30 Cards in this Set
- Front
- Back
concrete
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ingredients
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hydration
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chemical reaction when water is added to the dry mixture of aggregate and cement
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1850
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development of reinforced concrete |
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1918
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(Duff A Abrams) |
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1867 |
iron mesh reinforcing |
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1928 |
(Eugene Freynninet used high-strength steel wire to counter the effects of creep in concrete) |
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Portland cement
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manufactured from lime, silica, iron oxide, and alumina. proportioned, ground, and burned to form clinkers - then pulverized to produce cement |
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aggregates
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aggregates sizes (3)
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2. coarse aggregate: 1/4" dia - 1-1/2" dia. 3. economy: up to 6" dia. |
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mix
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the proportioning of the ingredients that comprise concrete |
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1:3:5 mix
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1 part cement; 3 parts fine aggregate; 5 parts coarse aggregate |
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water-cement ratio |
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laitance |
a chalky surface deposit of low strength that comes from excess water (must be removed before any new concrete is poured) |
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strength |
usual range 3,000psi - 6,000psi |
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ready-mix concrete
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mixed completely at a central mixing plant and transported to the site in an agitator truck. must be placed within 1-1/2 hours after water is added to the mix |
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transit-mix concrete
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mixed completely in truck mixer. dry materials are picked up and placed in mixer truck that carries a water tank. once arrived at site the water is added and then thoroughly mixed |
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reinforcing
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designated by numbers representing the diameter in eights of an inch: #3 (3/8" dia.) - #11 (1-3/8" dia.) and #18 (2-1/2" dia.) |
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ASTM A615 ASTM A616 ASTM A617 ASTM A706 |
A615 - billet steel A616 - rail steel A617 - axle steel A706 - low-alloy steel (most common ASTM A615 grade 60) |
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lightweight concrete
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its weight 90-115 pounds per cubic foot. - max. size of aggregate 3/" dia. - modulus of elasticity is lower - thus deflection greater - drying shrinkage is slightly greater - thermal insulation better - cost always greater |
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honeycomb effect
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when air bubbles are trapped in the body of the mixture and allowed to remain. they cause a substantial reduction in concrete strength and watertightness |
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slump test
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measures consistency and workability of the concrete mix, performed in the field
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cylinder test
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measures the compressive strength of concrete and utilizes standard test cylinders 6" in diameter and 12 inches long. laboratory cured for 7 - 28 days and tested in a crushing machine
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curing
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2. using a wet covering, moist sand, burlap 3. covering with a membrane or curing compound that prevents evaporation 4. leaving wood forms in place and keeping them moist |
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length of curing period
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3 - 14 days (should be as long as possible) |
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curing temperature |
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joints
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2. control joints - tooled, sawed, or premolded. create weakened sections that induce cracking 3. isolation joints - provide a separation between a slab on grade and columns or walls so that each can move independently |
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prestressed concrete
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stiffer (because the entire section is effective) and have greater shear strength |
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apply prestress
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2. posttensioning |
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precast concrete
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1. better quality control of concrete 2. better control over curing 3. members castable in all weather 4. members erectable in all weather 5. faster actual construction time |