,

τ

el

pl

shr

where ε - elastic deformation; ε - plastic deformation;

el

pl

ε - deformation of shrinkage.

shr

88

On the idealized chart of

compression of cement stone it

is possible to select three basic

areas: a-b-absence of cracks in

the structure of cement stone; bc-appearance of microscopic

cracks;

с-ddestruction of

cement stone as a result of

spontaneous formation of

growing cracks.

For description of cement stone

and concrete deformation under

loading a number of rheological

models are offered.

Fig. 5.1. The idealized chart of

deformations in cement stone at the

axial compression (at rapid loading)

ε - deformation; σ - stress

89

There is a large number of

formulas describing elastic

s

properties of concrete. Their

c.

kind depends on the accepted

or E

Ec.s

model of stresses distributing,

sc.

character of location of

f R

aggregates particles and other

oge

reasons.

n

R

a

c.s

Ch

1.5

C/W

4.0

Fig. 5.2. Typical relationship between

modulus of elasticity Ec.s , strength of

cement stone Rc.s and cement-water

ratio (C/W)

90

Modulus of concrete elasticity (E) depends on concrete strength. For

calculation of the modulus of elasticity at loading of concrete at age of

hardening (τ) following equations are using:

E R

E

m

τ

=