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Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
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Concrete

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  • 1. Concrete
  • 2. <ul><li>Reinforcing – concrete can withstand </li></ul><ul><li>thousands of pounds of vertical pressure </li></ul><ul><li>but is very weak for horizontal pressure. </li></ul><ul><li>- we use steel to reinforce because it has </li></ul><ul><li>the same coefficient of expansion and </li></ul><ul><li>contraction. </li></ul>
  • 3. <ul><li>Ordering concrete: </li></ul><ul><li>Specify: </li></ul><ul><li>1) amount needed or structure size </li></ul><ul><li>2) cement content </li></ul><ul><li>3) water content </li></ul><ul><li>4) type of aggregate </li></ul><ul><li>5) size of aggregate </li></ul><ul><li>6) slump </li></ul><ul><li>7) admixtures </li></ul><ul><li>8) time of delivery </li></ul>
  • 4. <ul><li>Subgrade preperation: </li></ul><ul><li>1) layout boundries </li></ul><ul><li>2) remove soft spots and fill back </li></ul><ul><li>3) grade to needed slope </li></ul><ul><li>4) firm subgrade </li></ul><ul><li>5) dig footings, foundation or edge. </li></ul><ul><li>6) construct forms </li></ul><ul><li>7) fill over clay loam soils with sand </li></ul><ul><li>8) oil forms </li></ul><ul><li>9) sprinkle subgrade with water </li></ul>
  • 5. <ul><li>Tips for hot weather concreting </li></ul><ul><li>1) cool ingredients </li></ul><ul><li>2) avoid excess mixing </li></ul><ul><li>3) sprinkle forms, subgrade and reinforcing </li></ul><ul><li>4) place concrete promptly </li></ul><ul><li>5) finish promptly </li></ul><ul><li>6) shade and windbreaks </li></ul><ul><li>7) apply curing compound </li></ul>
  • 6. <ul><li>Cold weather curing: </li></ul><ul><li>1) thaw ingredients and subgrade </li></ul><ul><li>2) use accelerators or high early strength </li></ul><ul><li>3) low slump mix </li></ul><ul><li>4) forms and reinforcing above 32 F </li></ul><ul><li>5) cure concrete above 32 F </li></ul><ul><li>6) leave forms in place while curing </li></ul><ul><li>7) allow concrete to dry before exposing </li></ul><ul><li>to freezing </li></ul>
  • 7. <ul><li>A mixture of : </li></ul><ul><li>portland cement </li></ul><ul><li>water </li></ul><ul><li>aggregates </li></ul>
  • 8. <ul><li>Plastic when freshly mixed </li></ul><ul><li>workable </li></ul><ul><li>uniform </li></ul><ul><li>consistent </li></ul><ul><li>Hard as a rock when set </li></ul><ul><li>strong </li></ul><ul><li>durable </li></ul><ul><li>water tight </li></ul><ul><li>resistant to abrasion </li></ul>
  • 9. <ul><li>1 sack of cement = 94 pounds </li></ul><ul><li>(1 cubic foot) </li></ul><ul><li>1 gallon of water = 8.3 pounds </li></ul><ul><li>7.5 gallons of water = 1 cubic foot </li></ul><ul><li>1 cubic yard = 27 cubic feet </li></ul><ul><li>1 cubic foot of sand = 100 pounds </li></ul>
  • 10. <ul><li>Cement – </li></ul><ul><li>a finely ground mixture of: </li></ul><ul><li>lime </li></ul><ul><li>silica </li></ul><ul><li>alumina </li></ul><ul><li>iron oxide </li></ul><ul><li>gypsum </li></ul>
  • 11. <ul><li>Manufacture of portland cement </li></ul><ul><li>limestone + silica sand </li></ul><ul><li>rock iron ore & oxides </li></ul><ul><li>+ </li></ul><ul><li>clay and shale </li></ul><ul><li>* heat to 2600 degrees F. to </li></ul><ul><li>form a “clinker” </li></ul><ul><li>+ </li></ul><ul><li>gypsum </li></ul><ul><li>* grind up the mixture to fine dust </li></ul><ul><li>called portland cement. </li></ul>
  • 12. <ul><li>Types of portland cement </li></ul><ul><li>1) normal </li></ul><ul><li>2) modified </li></ul><ul><li>3) high-early-strength </li></ul><ul><li>4) low heat </li></ul><ul><li>5) sulfate-resistant </li></ul>
  • 13. <ul><li>Water for concrete must be clean enough </li></ul><ul><li>to drink. </li></ul>
  • 14. <ul><li>Aggregate should be: </li></ul><ul><li>1) clean </li></ul><ul><li>2) strong </li></ul><ul><li>3) hard </li></ul><ul><li>4) cubical </li></ul>
  • 15. <ul><li>Things to test aggregate for: </li></ul><ul><li>1) organic matter </li></ul><ul><li>2) silt </li></ul><ul><li>3) voids </li></ul><ul><li>4) moisture </li></ul><ul><li>5) graduation </li></ul><ul><li>6) bulking </li></ul>
  • 16. <ul><li>Aggregate size: </li></ul><ul><li>gravel -- coarse - anything that will not </li></ul><ul><li>pass through a “4” </li></ul><ul><li>sieve. </li></ul><ul><li>snad -- fine – anything that will pass </li></ul><ul><li>through a “4” sieve. </li></ul><ul><li>( “4” sieve is ¼ x ¼ mesh) </li></ul>
  • 17. <ul><li>Concrete mix: </li></ul><ul><li>1 part cement </li></ul><ul><li>2 parts sand </li></ul><ul><li>3 parts gravel </li></ul><ul><li>* water to make the mix plastic </li></ul><ul><li>* example: 1 sack cement </li></ul><ul><li>2 cubic feet of sand </li></ul><ul><li>3 cubic feet of gravel </li></ul><ul><li>6 gallons of water </li></ul>
  • 18. <ul><li>Air Entrained concrete: </li></ul><ul><li>* concrete with air bubbles forced into it. </li></ul><ul><li>* 1 cubic yard will have 400-600 billion </li></ul><ul><li>bubbles in it. </li></ul><ul><li>* made by adding a air entraining agent </li></ul><ul><li>at the mixer. </li></ul>
  • 19. <ul><li>Advantages of air entrained: </li></ul><ul><li>1) reduces water and sand needed </li></ul><ul><li>2) improved workability </li></ul><ul><li>3) may finish sooner </li></ul><ul><li>4) increased water tightness </li></ul><ul><li>5) more resistance to freezing and </li></ul><ul><li>thawing </li></ul><ul><li>6) more resistance to scaling (deicers) </li></ul>

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