1. §4.4.6 Influencing factors Strength grade of cement W/C
Strength formula of the concrete
Factors of aggregate
Curing condition
Testing condition

2. Curing condition
The concrete strength is influenced by the degree and speed of cement hydration, which is affected by the humidity and temperature.
Higher the temperature, faster the speed of cement hydration, higher the concrete strength.
Larger the humidity, higher degree of cement hydration.
Cement
hydration
speed
Temperature
Concrete
strength
Cement
hydration
speed
Temperature
Concrete
strength

3. Curing condition
Humidity
Cement
hydration
degree
Concrete
strength

4. Curing condition
Relationship among strength, temperature and damping age of concrete are shown in flash, Fig and Fig.4.4.9

5. Influence of Temperature To Strength
fcu
non-frozen 40 30
frozen after 7 days 20
frozen after 1 day 10
age
Influence of Temperature To Strength

6. Fig.4.4.9 Relationship between strength and damping age of concrete
365
Age (d) 20 40 60 80
100
120
140
Damped for a long time
Damped for 14 days
Damped for 7 days
Damped for 3 days
Damped for 1 day
Fig Relationship between strength and damping age of concrete
f28(%)

7. Curing A． Natural cure B． Steam cure C. Autoclaved cure
The fixed temperature and relative humility in a certain time will guarantee the normal development of strength and other performances of concrete after the formation of concrete. This process is called curing.
There are three types of curing: Natural cure, steam cure and autoclaved cure. A．
Natural cure B．
Steam cure C.
Autoclaved cure

8. A．
Natural cure
Cured at the natural temperature and in the natural condition
P.Ⅰ, P.Ⅱ, P.O, P.S should be cured in more than 7 days;
P.P and P.F should be cured in more than 14 days;
The aluminous cement should be cured in more than 3 days.

9. B．
Steam cure
Steam cure
Pressure =1 standard atmospheric pressure
Temperature >100 ℃
The steam cure can improve the Portland cement with mineral admixture for % in the age of 28 days
P.ⅠP.Ⅱand P·O may reduce 10～15%

10. Autoclaved cure C.
Pressure ≮ 8 standard atmospheric
pressure
Temperature > ℃
Place: autoclave

11. Fig. 4.4.10 The relations between compressive strength and age

12. f28=fn ×(lg28/lgn) Logarithm formula: Application range
fn—n days strength of concrete
f28—28 days strength of concrete
Application range
Cured in standard condition
32.5—42.5 grade P.O (n>3)