2. Concrete Mix Design ACI Variation

3. 5% Variation for Adjusting Mixes n Determine what is to be added or reduced n If it is sand, stone, or cement compute it’s absolute volume by dividing it’s weight by the product of it’s specific gravity and 62.4 n If it is water then compute it’s absolute volume by dividing gallons by 7.5 Pg 116

4. 5% Variation n An equal volume of another component must be added or subtracted to account for the changed weight of the initial component. n Multiply the absolute volume of the component to be added or subtracted by it’s specific gravity and 62.4 (7.5 for water in gallons). Pg 116

5. 5% Variation n Compute the new design quantities by adding to and subtracting from the original design quantities. n The following criteria are recommended for adjusting mix designs.

6. 5% Variation n A workable slump cannot be obtained with design water less than the maximum allowable water by specifications. n Add water as necessary up to the maximum allowed and subtract an equal volume of fine aggregate. Pg 115

7. 5% Variation n A workable slump cannot be obtained using the maximum allowable water. n Reduce the surface area of aggregates by reducing the quantity of fine aggregate by 5% of it’s weight and replace it with an equal volume of coarse aggregate.

8. 5% Variation n A mix is to harsh ( to much coarse aggregate). n Add fine aggregate in the amount of 5% of it’s weight and reduce the coarse aggregate by an equal volume.

9. Examples

10. Example 1 n Mix gives a 2 ½ in slump. Increase the water by 1.5 gal/cu yd and adjust the mix appropriately. n One Cubic YdClass B Non vib n Cement545 Lbs Pg 117

11. Cement545 Lbs F.A.1307 LbsRose PitS.G.2.67FM 2.50 C.A.1466 LbsNew Bern Q S.G. 2.35UW 80.4 Water32.1 gals Air6%

12. Ex 1 Solution n Increase the water by 1.5 gals. Must reduce the sand by an equal volume. n Abs vol of water = 1.5/7.5 =.20 cu ft n Wt of sand removed=.20 x 2.67 x 62.4 =33Lbs n 35.1 gals + 1.5 gals = 36.6 gals n 1307 Lbs sand – 33 Lbs = 1274 Lbs

13. Ex 1 New Design Cement545 Lbs Sand1274 Lbs Stone1466 Lbs Water36.6 Gals Air6%

14. Example 2 n Mix design with the max allowable water does not give the desirable slump. n One Cubic YardClass A-vib Pg 118

15. Cement564 Lbs FA1154 LbsCoefieldSG 2.63FM 2.60 CA1872 LbsFieldaleSG 2.81UW 100.2pcf Water36.0 gal Air 6%

16. Ex 2 Solution n To increase slump, decrease surface area by reducing FA 5% and replacing with an equal amount of CA n 5% x 1154 Lbs of sand = 58 Lbs n 58 / (2.63 x 62.4) =.35 cu ft n Stone =.35 x 2.81 x 62.4 = 61 Lbs n 1154 Lbs sand – 58 = 1096 Lbs Sand n 1872 Lbs stone + 61 = 1933 Lbs Stone

17. Ex 2 New Design Cement564 Lbs Sand1096 Lbs Stone1933 Lbs Water36.0 Gals Air6%

18. Example 3 n Adjust the cement content to a Class AA with 715 Lbs of cement n One Cubic YdClass A vib

19. Ex 3 Cement564 Lbs FA1257 LbsElliott PitSG 2.66FM 2.50 CA1853 Lbs Burlington SG 2.87UW 98.0 pcf Water34.0 Gals Air6%

20. Ex 3 Solution n Difference in Cem = 715 -564 = 151 Lbs n 151 / (3.15 x 62.4) =.77 cu ft n Sand =.77 x 2.66 x 62.4 = 128 Lbs n Sand = 1257 – 128 = 1129 Lbs

21. Ex 3 New Design Cement715 Lbs Sand1129 Lbs Stone1853 Lbs Water34.0 Gals Air6%

22. Example 4 n Harsh Mix. Adjust by the 5% ACI variation method. n One Cubic YardClass AA vib Pg 120

23. Ex 4 Cement715 Lbs FA890 Lbs Cloverfield SG 2.61FM 2.69 CA1853 Lbs Statesville SG 2.79UW 97.1 pcf Water36.5 Gals Air6%

24. Ex 4 Solution n Add sand and reduce stone by equal volume n 5% x 890 Lbs sand = 45 Lbs n Sand added=45/(2.61 x 62.4) =.28 cu ft n Stone removed =.28 cf x 2.79 x 62.4 = 49 Lbs n 890 Lbs sand + 45 Lbs = 935 Lbs sand n 1996 Lbs stone – 49 Lbs = 1947 Lbs stone

25. Ex 4 New Design Cement715 Lbs Sand935 Lbs Stone1947 Lbs Water36.5 Gals Air6%

26. Problem 1

27. P 1 n Mix did not give desired slump. Increase water to the maximum and adjust mix accordingly. n One Cubic YardClass A vib

28. P1 Cement564 Lbs FA1276 LbsBoone QSG 2.73FM 2.46 CA1826 LbsMission Dam Q SG 2.79UW 96.6 pcf Water34.0 Gals Air6% Pg 125

29. P1 Solution n Increase water, Decrease Sand n Table 1000-1 =.532 x 564 = 300 /8.33 = 36.0 gal max water n 36.0 -34.0 = 2.0 gals increase n 2.0 / 7.5 =.27 cu ft n Sand removed =.27 x 2.73 x 62.4 = 46 Lbs n Sand = 1276 – 46 = 1230 Lbs

30. P1 New Mix Design Cement564 Lbs Sand1230 Lbs Stone1826 Lbs Water36.0 Gals Air6%

31. Problem 2

32. P 2 n The mix does not give the desired slump using the maximum water permitted. Adjust the mix using the 5% variation method. n One Cubic YardClass A Vib AE

33. P2 Cement564 Lbs FA1210 LbsWhite PitSG 2.63FM 2.45 CA1916 Lbs Bessemer City Q SG 2.97UW 101.4 pcf Water36.0 Gal Air6%

34. P2 Solution n Decrease sand to reduce surface area, Increase stone n Sand removed = 1210 x.05 = 61 Lbs n 1210 – 61 = 1149 Lbs Sand n 61 / (2.63 x 62.4) =.37 cu ft n Stone added =.37 x 2.97 x 62.4 = 69 Lbs n Stone = 1916 + 69 + 1985 Lbs

35. P2 New Mix Design Cement564 Lbs Sand1149 Lbs Stone1985 Lbs Water36.0 Gals Air6%

36. Problem 3

37. P 3 n Change the Class B mix so that it contains 7 sacks per yard of cement. Adjust other components as necessary. n One Cubic YardClass B non vib

38. P 3 Cement545 Lbs FA1329 LbsWhite PitSG 2.63FM 2.45 CA1688 LbsBakers QSG 2.75UW 89.3 pcf Water35.0 Gal Air6%

39. P3 Solution n The Cement will increase, and the Sand will decrease. n Cement = 94 x 7 = 658 Lbs n 658 – 545 = 113 Lbs increase in cement n 113/(3.15 x 62.4) =.57 cu ft n Sand deducted =.57 x 2.63 x 62.4 = 94 Lbs n Sand = 1329 – 94 = 1235 Lbs

40. P 3 new mix design Cement658 Lbs Sand1235 Lbs Stone1688 Lbs Water35.0 Gals Air6%

41. Problem 4

42. P 4 n Change the Class A mix to a AA mix with 7.6 sacks of cement per yard. Adjust the other components as necessary. n One Cubic YardClass A Vib

43. P 4 Cement564 Lbs FA1105 LbsRose PitSG 2.63FM 2.50 CA1790 LbsTom’s Creek Q SG 2.60UW 94.7 pcf Water35.8 Gals Air6%

44. P 4 Solution n Cement amount increases, Sand amount decreases. n 7.6 x 94 = 714 Lbs of Cement n 714 – 564 = 150 Lb increase in cement n 150 / (3.15 x 62.4) =.76 n Decrease in Sand =.76 x 2.63 x 62.4 = 125 Lbs n Sand = 1105 – 125 = 980 Lbs

45. P 4 new mix design Cement714 Lbs Sand980 Lbs Stone1790 Lbs Water35.8 Gals Air6%

46. Problem 5

47. P 5 n The mix is to harsh. Adjust by using the 5% ACI variation method. n One Cubic YardClass AA vib

48. P 5 Cement714 Lbs FA975 LbsSingleton Pit SG 2.63FM 2.30 CA2037 Lbs Arrowood Q SG 2.93UW 104.8 pcf Water35.0 Gals Air6%

49. P 5 Solution n Sand will increase and Stone will decrease. n Sand increase = 975 x.05 = 49 Lbs n Sand = 975 + 49 = 1024 Lbs n 49 / (2.63 x 62.4) = 0.30 cu ft n Stone decrease =.30 x 2.93 x 62.4 = 55 Lbs n Stone = 2037 -55 = 1982 Lbs

50. P 5 new mix design Cement714 Lbs Sand1024 Lbs Stone1982 Lbs Water35.0 Gals Air6%

51. Problem 6

52. P 6 n Class AA mix did not give desired slump using max water. Increase the water by 2 gallons per yard and increase the cement enough to maintain the same W/C ratio. Adjust the other components as necessary. n One Cubic YdClass AA vib AE

53. P 6 Cement639 Lbs FA1148 LbsCandor Pit SG 2.62FM 2.71 CA1779Crabtree Q SG 2.65UW 96.9 pcf Water32.6 Gals Air6%

54. P 6 Solution n Cement and Water increase, Sand Decreases n Compute original W/C ratio – 32.6 gal x 8.33 = 272 Lbs water – 272 / 639 =.426 = W/C ratio n Compute new cement – New water = 34.6 x 8.33 = 288 Lbs – Water / (W/C ratio) = 288/.426 = 676 Lbs cem

55. P 6 Solution cont n Increase in cement = 676 -639 = 37 Lbs – 37 / (3.15 x 62.4) =.19 cu ft n Increase in water = 2 gal / 7.5 =.27 cu ft n Total increase =.19 +.27 =.46 cu ft n Sand decrease =.46 x 2.62 x 62.4 = 75 Lbs n 1148 – 75 = 1073 Lbs sand

56. P 6 new mix design Cement676 Lbs Sand1073 Lbs Stone1779 Lbs Water34.6 Gals Air6%

57. Filling out Form 312 n The contractor submits his own mix design on M&T form 312 to the NCDOT for acceptance. n The items listed must be completed by the contractor. Pg 121

58. Mix Design Form n Make sure the minimum cement is used for the class of concrete. n Make sure the W/C ratio and maximum water permitted has not been exceeded. n Make sure the correct design air content is used.

59. Mix Design Form n Make sure the materials used are state approved and the correct specific gravities and fineness modulus of the material is used in the design. n Make sure the ACI method of design is used and the mix produces 27.00 cu ft. n Make sure admixtures are on approved list.

60. Problem 7

61. Corrections to P7 n Fine Aggregate is 1372 Lbs n Coarse Aggregate is 1661 Lbs n Water is 32.7 Gals n Slump is 3.5” n Mortar Content is 17.56 cu ft n Max Water is 32.7 Gals

62. P7 Correction n Fine Agg SG is 2.64 n FM is 2.81 n Coarse Agg SG is 2.82 n Unit Weight is 99.2 pcf