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FUNDAMENTALS OF CONCRETE

FUNDAMENTALS OF CONCRETE. Presented By: Kevin J. Brigandi Construction Services Department Manager kjbrigandi@terracon.com Debra A. Nunes Construction Services Department Manager danunes@terracon.com. CONCRETE BASICS. Uses of Concrete:

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FUNDAMENTALS OF CONCRETE

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  1. FUNDAMENTALS OF CONCRETE Presented By: Kevin J. Brigandi Construction Services Department Manager kjbrigandi@terracon.com Debra A. Nunes Construction Services Department Manager danunes@terracon.com

  2. CONCRETE BASICS • Uses of Concrete: • Concrete can be formed in almost any color, shape and texture, while serving as an acoustic and thermal barrier • Concrete can be placed in all environments and conditions • Concrete is resistant to fire, chemical exposure and weather • Concrete is environmentally safe and recyclable • Concrete is efficient to construction and can be produced with a variety of durability characteristics and strengths

  3. Dams, Roads, Bridges and Parking structures

  4. Buildings

  5. Retaining Walls, Foundations and Flatwork

  6. Driveways and Sidewalks

  7. Interior Flooring & Countertops

  8. Controlled Low Strength Material (CLSM)

  9. Insulated Concrete Forms (ICF’s)

  10. What is Concrete?

  11. Chemical Admixtures

  12. Mineral Admixtures

  13. How Should Concrete Be Specified? • Strength • Water / Cement Ratio • Air % • Minimum Cement Factor • Slump / Durability

  14. Water / Cement Ratio Calculations 30 Gal 8.33 lb. 250 lb. ----------- X ------------ = ---------- = .44 W/C 6 Sack 94 lb. 564 lb.

  15. Adding Water to Concrete

  16. Nominal max size of aggregate, in. Severe Exposure Moderate Exposure Mild Exposure 5 Less than 3/8 9 7 3/8 7.5 6 4.5 1/2 7 5.5 4 3/4 6 5 3.5 1 6 4.5 3 1-1/2 5.5 4.5 2.5 2 5 4 2 Entraining Air in Concrete

  17. Concrete Quality Control • All Field Technicians should be certified • And have a working knowledge of the following ASTM standards: • C31 • C1064 • C143 • C172 • C173 • C231 • C138

  18. ASTM C 172:Standard Method for Sampling Freshly Mixed Concrete • Sample from middle portion of the batch • Sample at two or more regularly spaced intervals, not to exceed 15 min • Combine and remix sample thoroughly • Cover Sample to protect from drying

  19. ASTM C 143:Standard Test Method for Slump of Portland Cement Concrete

  20. ASTM C 231: Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method

  21. ASTM C 173:Standard Test method for Air Content of Freshly Mixed Concrete by the Volumetric Method

  22. Basic Techniques for Finishing Flatwork • Strike-off • Bull Floating • Darbying • Floating • Troweling • Brooming • Jointing • Edging • Curing

  23. Finishing

  24. Curing • Performed as soon as possible after final finishing is completed • Performed to prevent the loss of moisture from concrete • Helps in maintaining a favorable concrete temperature for a definite period of time • Will make concrete stronger • More impermeable • More resistant to stress • More resistant to abrasion • More resistant to freezing and thawing conditions

  25. Curing Methods and Materials • Ponding or immersion • Spraying or Fogging • Wet Coverings • Impervious Paper • Plastic Sheets* • Membrane-Forming Curing Compounds • Steam • Insulating Blankets or Covers *discoloration can occur if not used properly

  26. Common Concrete Problems Discoloration Dusting Cracking Plastic shrinkage cracking Crazing Scaling Curling Blisters Delamination Pop Outs

  27. Discoloration

  28. Prevention of Discoloration • Do not Use Calcium Chloride • Type, kind and condition of formwork • can influence color • Eliminate “Burning” of concrete • Proper curing - Caution with Plastic • Uniform sub-grade moisture

  29. What is Dusting? Powders under any type of traffic Easily scratched with a nail or even by sweeping Very weak wearing surface

  30. What Causes Dusting? • Finishing operation performed while bleed water is on the surface or before bleeding has finished • Insufficient curing • Placement of non-absorptive sub grade or polyethylene vapor barrier • Floating/Troweling after the condensation of moisture from warm humid air is on cold concrete

  31. Prevention of Dusting • Do not place concrete directly on polyethylene vapor barriers or non-absorptive sub grades • Proper curing • Cold weather concrete practices • Vent exhaust to the outside to provide adequate ventilation

  32. Cracking The one thing I can guarantee is that your concrete will crack!

  33. Crazing

  34. How To Prevent Crazing

  35. How To Prevent Scaling

  36. Repairing Scaled Concrete • Clean surface thoroughly • Resurface • Repair mortar • Portland Cement concrete

  37. What Is Curling? Slab Curling The distortion of a slab into a curved shape due to temperature gradients throughout the depth of the concrete

  38. Why Do Slabs Curl? Other Factors That Cause Curling: Bleeding / Poor curing / Joint spacing Shrinkage of the top relative to the bottom of the slab Moisture gradients in slab Temperature gradients within the slab

  39. Minimization of Curling • Lowest practical slump • Largest practical aggregate size • Largest practical aggregate content • Avoid excessive bleeding • Avoid vapor barriers • Avoid higher than needed cement contents • Proper Curing • Adequate Joint spacing • Increase Slab Thickness

  40. Blisters An irregular hollow bump that appears on the surface during or right after finishing operations

  41. Why Does Concrete Blister?

  42. How Do You Prevent Blisters? • Delay final finish as long as possible • Avoid surface drying • Initial float done with flat blades

  43. Delaminations • The top 1/8 inch of the surface is densified and separated from the base slab by a thin layer of air or water • Forms during final troweling • Most frequent in early spring and late fall

  44. What Are Pop Outs? A Conical Fragment that breaks out of the surface

  45. Green Concrete Technology Benefits of Pervious Concrete • Environmental Benefits • Economic Benefits • Structural Benefits

  46. Pervious Concrete Design

  47. Mix Designs of Pervious Concrete • Supplementary cementitious materials (SCMs) • Coarse Aggregates • Water • Admixtures

  48. Testing and Inspection of Pervious Concrete • Density Testing (ASTM C29) • No Slump • No Air

  49. Self Consolidating Concrete • The use of self-consolidating concrete (SCC) has grown tremendously since its inception in the 1980s. • Because of the material performance in its fresh state, the existing testing methods for conventional concrete are no longer suitable for SCC.

  50. Mix Designs for SCC • SCC mixtures can be designed to provide the required hardened concrete properties for an application, similar to regular concrete.

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