1. Prepared by Marcia C. Belcher Construction Engineering Technology
MIX PROPORTIONING
Prepared by Marcia C. Belcher
Construction Engineering Technology

2. Design Consideration: Obtaining Good Workability

3. Design Consideration: Obtaining Good Workability

4. Obtaining Good Workability

5. Obtaining Good Workability

6. Design Consideration: Prevent Segregation & Bleeding

7. Well Graded Aggregates Will Reduce Segregation & Bleeding
Well Graded Poorly Graded

8. Measuring Workability: Slump

9. The Slump Cone

10. Concrete Construction
Approximate Required Slump Values (PCA)
Concrete Construction
Slump (Max.)
Slump (Min.)
Reinforced foundation walls/footings
3 in
1 in
Plain footings and substructure walls
Beams & reinforced walls
4 in
Building columns
Pavement & slabs
Mass concrete
2 in

11. Economics of Mix Design
Goals:
Maximize strength
= minimize water
= control bleeding & segregation
Reduce Cost
= use largest gravel possible for the job
= minimize paste requirement
Provide good durability
= use well graded aggregates
= maximize void packing
= reduced segregation

12. Cost Comparison of Constituents

13. Guidelines We Use For Mix Design
PCA Manual
Tables for w/c ratio based on compressive strength requirement & slump (workability)
Volume of stone required based on max. agg. size and sand fineness.
Water required based on max. agg. size, slump & w/c ratio (compressive strength)

14. Design Method We Will Use: Absolute Volume Method
Assumes no air voids in concrete
Amount of concrete is sum of solid volumes:
1 CUBIC YARD
Cement
Sand
Coarse aggregate
Water
Air

15. WATER CORRECTION
Any water content in aggregates above SSD water content must be subtracted from the water requirements
Any water requirement of aggregates (below the SSD water content) must be added to the water requirements

16. Material Values & Constants Needed For Design:
SSD (Absorption) of Sand
Unit Weight & SG of Sand
SSD (Absorption) of Stone
Unit Weight & SG of Stone
Density of Cement = 195 pcf
SG Cement = 3.15
Density of Water = 62.4 pcf
1 Cubic Foot Water = 7.48 gal
1 Gal. Water = 8.34 lbs

17. ACI Standard Mix Design Method
The standard ACI mix design procedure can be divided up into 8 basic steps:
Choice of slump
Maximum aggregate size selection
Mixing water and air content selection
Water-cement ratio
Cement content
Coarse aggregate content
Fine aggregate content
Adjustments for aggregate moisture

18. Step #1: Select Slump
Table 9.6

19. Step #2: Determine Mixing Water and Air Content
Table 9.5

20. Step #3: Max. Agg. Size Check
DEFINITION: Nominal maximum aggregate size is the largest sieve that retains some of the aggregate particles.
ACI Limits:
1/3 of the slab depth
3/4 of the minimum clear space between bars/form
1/5 minimum dimension of non-reinforced member
Aggregate larger than these dimensions may be difficult to consolidate and compact resulting in a honeycombed structure or large air pockets.

21. Step #4: Select W/C Ratio
Table 9.3

22. Step #5: Cement Content
The calculated cement amount is based on the selected mixing water content and water-cement ratio.
W/C= Wt. of Water
Wt. of Cement

23. Step #6: Coarse Agg. Content
Table 9.4

24. Step #7: Fine Agg. Content

25. Step #8: Batch Weight & Water Adjustment
Aggregate weights. 
Aggregate volumes are calculated based on oven dry unit weights, but aggregate is batched in the field by actual weight. 
Any moisture in the stockpiled aggregate will increase its weight.
Without correcting for this, the batched aggregate volumes will be incorrect.
Amount of mixing water. 
If the batched aggregate is anything but saturated surface dry it will absorb water (if dry) or give up water (if wet) to the cement paste. 
This causes a net change in the amount of water available in the mix and must be compensated for by adjusting the amount of mixing water added.

26. Mix Design Example: 10” Thick Unreinforced Pavement Slab

27. Properties of Concrete Specified By Engineer:
Slump =1.0 inch
28-day strength of 5000 psi
Air content: percent

28. Information About Materials:
Coarse aggregate we are using (ODOT #467):
nominal maximum size = 1.5 inch (see Agg. Size Table)
dry-rodded weight = 100 lb/ft3
specific gravity = 2.68
moisture content = 1.0 percent
absorption = 0.5 percent
Fine aggregate:
fineness modulus = 2.80
specific gravity = 2.64
moisture content = 5 percent
absorption = 0.7 percent

29. WE ARE DESIGNING BATCH WEIGHTS FOR ONE CUBIC YARD
Step #1: Select Slump
Engineer Specified 1” (correlates w/table)
Table 9.6

30. Step #2: Determine Mixing Water and Air Content
1.5” Stone
Table 9.5
1” Slump

31. Step #2: Determine Mixing Water and Air Content
Weight of Water = 250 lbs/yd3
Volume of Water = 250 lbs/yd3 = 4 ft3
62.4 lbs/ft3
Volume of Water = 4 ft3 per cubic yard of concrete

32. Step #3: Max. Agg. Size Check
ACI Limits:
1/3 of the slab depth
10”/3 = 3.33 inches > 1.5” OK

33. Step #4: Select W/C Ratio
Table 9.3

34. Step #5: Cement Content W/C= Wt. of Water Wt. of Cement
Wt. of Cement = 250 lbs/yd3
.40
=625 lbs/yd3
Volume of Cement = 625 lbs/yd3 (Concrete)
3.15 x 62.4 lbs/ft3
Volume of Cement = ft3 per cubic yard of concrete
SG Cement

35. Step #6: Coarse Agg. Content
Table 9.4

36. Dry Rodded Unit Wt of Stone
Step #6: Coarse Agg. Content
Weight (Dry) =.71 x 27 ft3/yd3 x 100 lb/ft3 = 1,917 lbs
Volume = 1,917 lbs = ft3
2.68 x 62.4 lbs/ft3
Dry Rodded Unit Wt of Stone
SG Stone

37. Step #7: Fine Agg. Content
27 ft Cubic Yard of Concrete
4 ft Water
1.49 ft Air (.055 x 27 ft3)
3.18 ft Cement
11.46 ft Stone
6.87 ft Sand
Wt of Sand(Dry) = 6.87 ft3 x 2.64 x 62.4 lbs/ft3 = 1,131.7 lbs.
SG Sand

38. Step #8: Aggregate Batch Weights & Water Adjustment
Since there is moisture in both coarse & fine aggregate,
their batch weights must be adjusted
Wt of Stone(Wet) = 1,917 lbs x 1.01= 1,936.2 lbs
Wt of Sand(Wet) =1,131.7 lbs x 1.05= 1,188.3 lbs
1% Moisture
5% Moisture

39. Step #8: Aggregate Batch Weights & Water Adjustment
Mixing water needs to be adjusted. Both the coarse and fine aggregate are wet of SSD and will contribute water to the cement paste.
Water from Stone = 1,917 lbs. x ( ) = 9.59 lbs
Water from Sand= 1,131.7 lbs x ( ) = lbs
Water = 250 lbs – 9.59 lbs – lbs = lbs
Dry Wt.
Moisture
Absorption
Dry Wt.
Moisture
Absorption

40. Final Batch Wts. (1 Cubic Yard)
Water
lbs = 23 gallons
Cement
625 lbs
Stone
1,936.2 lbs
Sand
1,188.3 lbs