1. The document discusses concrete mix design and redesign, including self-compacting concrete. 2. Key aspects of mix design include determining the water content needed for different slump levels and aggregate sizes/types. Mixes are redesigned as needed. 3. Self-compacting concrete is discussed as an alternative, including reasons for changing to it, mix design principles, and testing methods like slump flow and V-funnel tests. Proper proportioning of admixtures like superplasticizers and viscosity modifying admixtures is also covered.

1. CONCRETE MIX DESIGN AND
REDESIGN
• 1 Mix design
• 2 Mix re-design
• 3 Self-Compacting Concrete

2. Concrete
Batching
Plants

3. Moisture
control in
aggregates

4. Normal Distribution
mean = failure level + z  standard deviation.

5. A table of z (or n) values
for various values of percentage failures
(table 1.10.1 in section 1.10 of the notes)
Percentage failure
permitted
z value
16 1.00
10 1.28
5 1.64
2.5 1.96
2 2.05
1 2.33

6. Figure 3

7. Table 2 Approximate compressive strengths (Mpa) of concrete
mixes made with a free w/c ratio of 0.5
Age (days)
Type of Cement Type of Coarse
Aggregate
3 7 28 90
Ordinary Portland
(OPC) or Sulphate
Resisting (SRPC)
EN Class 42.5
Uncrushed 22 30 42 49
Crushed 27 36 49 56
Rapid Hardening
(RHPC)
EN Class 52.5
Uncrushed 29 37 48 54
Crushed 34 43 55 61
Table 2

8. Figure 4

9. Table 3
Table 3 Approx water contents (kg/m3) required to give workability
Slump (mm) 0-10 10-30 30-60 60-180
Vebe time (s) more
than 12
6-12 3-6 0-3
Maximum
aggregate
size (mm)
Type of
aggregate
10 Uncrushed 150 180 205 225
Crushed 180 205 230 250
20 Uncrushed 135 160 180 195
Crushed 170 190 210 225
40 Uncrushed 115 140 160 175
Crushed 155 175 190 205

10. Figure 5

11. Figure 6 (10mm)

12. Figure 6 (20mm)

13. 2.5 CONCRETE MIX DESIGN
AND REDESIGN
• 1 Mix design
• 2 Mix re-design
• 3 Self-Compacting Concrete

14. Self Compacting Concrete
1. Why change to SCC?
2. Mix Design
3. Testing

15. Why change to SCC?
• Lower labour cost (no vibration needed)
• Better finish
• Faster placing
• No risk of white-finger
• Less noise
• Can be placed with congested
reinforcement.

16. Self Compacting Concrete
1. Why change to SCC?
2. Mix Design
3. Testing

17. Principles of mix design for SCC
• Design the concrete mix to achieve the required strength and
a slump of 100mm.
• If the cement content is less than 500kg/m3, add PFA so
that:
– The total cementitious (cement + PFA) is 500kg/m3
– The equivalent cement content (= Cement + 0.3  PFA)
is the same as the cement content from the original mix
design.
• Check that the PFA is less than 40% of the total
cementitious content. If it is more than 40% some of it will
not react, so it will not contribute to the strength.
• Add superplasticiser and VMA in the amounts specified by
the manufacturers.

18. Proportioning the admixtures
• Add a superplasticiser to get the flow
• Add a VMA to prevent segregation
• Use the manufacturers’ data on W drive
• Note that some VMAs are used in very
small quantities.

19. Self Compacting Concrete
1. Why change to SCC?
2. Mix Design
3. Testing

20. Test Methods
• Slump Flow
• V Funnel
• L box
Slump Flow Test
The standards are on W drive