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  1. WELCOME N.C. DEPARTMENT OF TRANSPORTATION MATERIALS AND TESTS UNIT CONCRETE CERTIFICATION SCHOOL

  2. CONCRETE MIX DESIGN TECHNICIAN SCHOOL

  3. M& T CONTACTS • WALTON JONES(RALEIGH)919-733-7091 • MARIA LONG (WILLIAMSTON) 252-792-7627 • DAN ALLEN (WILMINGTON) 910-371-6964 • DARRELL LUMLEY(RALEIGH) 919-556-7606 • HENRY TRAYWICK (FAYETTEVILLE) 910-486-1732 • ROBERT FOSQUE(GREENSBORO) 336-334-3611 • SANDRA POTTS(SALISBURY) 336-993-2300 • MARK THOMAS (MATTHEWS) 704-847-1314 • TRACH CHURCH(WILKESBORO) 336-903-9107 • CHARLES BULLOCK(ASHEVILLE) 828-298-1516

  4. AME’s • HENRY TRAYWICK DIV 1,2,3,6 • JESSICA SMITH DIV 4,5,7 • PAM CARRIKER DIV 8,9,10 • KEN HAMBY DIV 11,12,13,14

  5. INSTRUCTOR • WALTON JONES 919-733-7091

  6. PLEASETELEPHONES OFF OR ON VIBRATE

  7. BATHROOMS MENS WOMEN

  8. CLASS HOURS 8:30 - 4:30

  9. SCHEDULE • DAY 1&2 Review Schools, Agg. Gradation, Wt.-Vol. Relationships • DAY 3 Admixtures, Placing Conc., ACI Mix Design • DAY 4 Fly Ash, Mix Design Variations, Hot & Cold Weather Conc. & Curing, Exam, Review • DAY 5 Math Exam

  10. PREREQUISITES FOR CLASS

  11. NCDOT BATCH TECHNICIAN CERTIFICATION MUST BE CURRENT, OR MUST HAVE SUCESSFULLY COMPLETED BATCH SCHOOL CLASSROOM PORTION

  12. QUESTIONS

  13. REVIEWConcrete Field & Batch Technician School

  14. Review Topics • Components Of Concrete • Moisture Calculations and Batch Weight Adjustments • Field Tests

  15. Components Of Concrete • Cement - The bonding agent. • Sand - Gives workability to the mix. • Stone - Filler material, aids in strengthening the mix. • Water - Causes a chemical reaction called hydration. • Air Agent - For freeze/thaw, durability • Retarder - Slows setting time.

  16. Components Cont. • Water and Cementitious Materials - Portland cements, fly ash, slag. • Fine and Coarse Aggregates - Sands and stones (60-80% of mix). • Chemical Admixtures - Air entrainers, retarders, water reducers, super-plastizers.

  17. Components Cont. • Paste - A combination of cement, water, and entrained air. • Setting Time - The time that it takes for a cement paste to begin hardening. • Mortar - Paste and fine aggregates. • Concrete - Mortar and coarse aggregate.

  18. Aggregates • 60% to 80% of the volume of the mix is aggregates. • Sand may be natural or manufactured and it’s texture will be from fine to coarse. • Stone may be angular from a quarry, or rounded from a pit. • Standard stone sizes for structural concrete from Table 1005-1: #57, #67, and #78.

  19. Moisture Calculations & Batch Weight Adjustments • Calculate Total Moisture in fine and coarse aggregate stockpiles. • Calculate Free Moisture Total Moisture - Absorbed Moisture • Use Free Moisture to calculate batch weight adjustments. • Mix designs are based on SSD weights.

  20. TOTAL MOISTURE • Moisture on the surface and the moisture in the pours and capillaries of an aggregate. • Total Moisture is calculated by: Wet Wt. - Dry Wt. ---------------------- X100 Dry Wt.

  21. Determine Total Moisture • Given the following weights, determine the total moisture: Wet Weight 555.4 grams Dry Weight 523.2 grams • Is this a Fine or Coarse Aggregate sample?

  22. Answer 555.4 - 523.2 ------------------ X 100 = 6.2% 523.2 This is a Fine Aggregate sample

  23. Determine Total Moisture • Given the following weights, determine the total moisture: Wet Weight 1534.2 grams Dry Weight 1505.0 grams • Is this a Fine or Coarse Aggregate sample?

  24. ANSWER 1534.2 - 1505.0 ---------------------- X 100 = 1.9% 1505.0 This is a Coarse Aggregate Sample

  25. Determine Free Moisture • Given the following moistures, determine the Free Moisture: Fine Agg. Total Moisture 6.2% Absorbed Moisture 0.4% Coarse Agg. Total Moisture 1.9% Absorbed Moisture 0.7%

  26. ANSWER Fine Aggregate: 6.2% - 0.4% = 5.8% FREE MOISTURE Coarse Aggregate: 1.9% - 0.7% = 1.2% FREE MOISTURE

  27. Batch Weight Adjustment Problem • Mix design weights are as follows: Cement 555 lbs Sand 1222 lbs Stone 1865 lbs Water 290 lbs

  28. Sand Adjustment • Using the FREE MOISTURE 5.2%, adjust sand weight. • 5.2 / 100 = 0.052 • 1222 X 0.052 = 63.5 lbs. (Water) • 1222 + 64 = 1286 lbs. Adjusted Sand Weight = 1286 lbs

  29. Stone Adjustment • Using the FREE MOISTURE 3.6%, adjust the stone weight. • 3.6 / 100 = 0.036 • 1865 X 0.036 = 67.1 lbs. (Water) • 1865 + 67 = 1932 lbs. Adjusted Stone Wt. = 1932 lbs

  30. Water Adjustment • Total additional water from sand and stone. • 64 lbs. + 67 lbs. = 131 lbs. • 290 lbs. (design water) - 131 lbs. = 159 lbs. Adjusted Water Wt. = 159 lbs.

  31. Corrected Batch Weight • Corrected weights for ONE cubic yard: Cement 555 lbs. Sand 1286 lbs. Stone 1932 lbs. Water 159 lbs. • What are the weights for a 9 cubic yard load?

  32. Pull Weights • For a 9 yard load - multiply batch weights for one yard load times 9. • Corrected weights for 9 cubic yard load: Cement 4995 lbs. Sand 11,574 lbs. Stone 17,388 lbs. Water 1431 lbs.

  33. BATCH TOLERANCES • CEMENT MUST BE BATCH WITHIN ± 1% OF MIX DESIGN WEIGHT • FLY ASH MUST BE BATCHED WITHIN ± 1% OF MIX DESIGN WEIGHT • SAND MUST BE BATCHED WITHIN ± 2% OF THE MOISTURED CORRECTED MIX DESIGN WEIGHT

  34. STONE MUST BE BATCHED WITHIN ± 2% OF THE MOISTURE ADJUSTED MIX DESIGN WEIGHT. • WATER MUST BE BATCHED WITHIN ± 1% OF THE MOISTURE ADJUSTED MIX DESIGN AMOUNT.

  35. BATCHING TOLERANCES • CEMENT- ± 1% • FLY ASH - ± 1% • SAND- ± 2% • STONE- ± 2% • WATER - ± 1%

  36. NCDOT Certification • Concrete Field Technician: Qualified to perform concrete acceptance tests on NCDOT projects. Certified as a “Grade 1 Field Test Technician” by ACI. • Concrete Batch Technician: Certified to batch Ready Mixed, Precast, or Prestressed Concrete for NCDOT projects.

  37. What Does This Mean? • Anyone testing or batching concrete for a NCDOT project shall be certified. • A Field and Batch Technician should be properly trained, knowledgeable, and competent to perform their duties.

  38. Concrete Mix Design Technician • Learn how to perform Sieve Analysis, Fineness Modulus, Design Concrete Mixes using the Absolute Volume Method, and Vary Mixes using the 5% Deviation Method. • Pass this course and become certified to design and vary concrete mixes.

  39. BREAK