There are three important definitions about strength

Cubic compressive strength of concrete

Assurance factor of concrete

Standard cubic compressive strength of concrete

§4.4.3 Definition of strength

The compressive strength of 150150150mm cube cured in standard age of 28days.

Tep=20 ±3℃ ℃ ， RH 90% cured in standard ﹥condition

Instruments of strength test are shown in Fig. 4.4.4.

Cubic compressive strength of concrete － fcu

Fig. 4.4.4 Instruments of strength test

Assurance factor of concrete-P%

Assurance factor of concrete-P% refers to the probability of the strength beyond the designed strength in strength ensemble.

Fig. 4.4.5 Sketch Map of Assurance Factor of Concrete -P%

P（ t）＝ 90%

t0t

ψ(l )

Standard cubic compressive strength of concrete refers to cubic compressive

strength of concrete with 95% assurance factor.

ffcucuffcucu

P=95%P=95%P=95%P=95%

ffcu,kcu,kffcu,kcu,k

Standard cubic compressive strength of concrete － ffcu,kcu,k

fcu,k is the strength to design structures

fcu,k is used in quality control

fcu,k is used in engineering acceptance check

For example 　

≥1.15 fcu,k , fcu,min ≥0.95 fcu,k

is average value of strength

NotesNotes

Standard cubic compressive strength of concrete － ffcu,kcu,k