Mix design - Concrete Mix Design, Quality Control and Specification - page 213

changes resulting from the concrete formulation. The value of k can be
greatly reduced when the w/c increases from 0.5 to 0.6.

Example 8.1: Application 1

Calculate of the resistance target at 28 days for plastic concrete dosed
at 300 kg/m³ of CPA-CEM I 42.5, 66 kg/m³ fly ash (characteristic
values of the activity index above 0.82 at 28 days and 0.93 at 90 days)
and that have natural aggregates with Dmax equal to 20 mm.

Solution
For activity index above 0.82 at 28 days and 0.93 at 90 days, the value
of k given by the standards is equal to 0.5.

C + kA = 300 + 0.5 × 66 = 333 kg/m³

Bolomey equation

E + V = 210 l

FM = 55 MPa

kb = 0.55

fc28 = 55 × 0.55 (333/210 - 0.5) = 33 MPa

Example 8.2: Application 2

Design a C25-30, workability S4 and natural aggregates (D =
20 mm), superplasticiser, and fly ash. In order to focus the calcu-
lation on cement and fly ash dosage, we are going to consider the
following data:

• Water content = 185 l (we consider that the superplasticiser
reduces the water demand by 12%)
• Choice of cement = CPA-CEM 42.5
• w/c = 0.6

1. Calculate cement without addition.

185
0.6

308 kg/m 3 C = =

2. Calculate cement and fly ash dosage in the context of substitu-
tion of cement.