,

(9

.1)

c

a



100

m



where ρ and ρ – density of porous aggregate grains and cement-sand

a

m

mortar, V – volume of voids between grains, ϕ - volume concentration of

v

porous aggregate.

Strength of lightweight concrete is correlated with their density (Fig. 9.1).

Great influence makes volume of voids between aggregate grains not filled

with cement paste.

Most of the formulas for lightweight concrete strength are based on the

hypothesis of stresses distribution between components of lightweight

concrete under their destruction.

172

Their application for concrete design is

3

impossible or difficult as if they are not

g/m

connected single-valued with certain definite

te, k

cre

mix parameter.

con

lay

Mix parameter single-valued with strength for

d cend

lightweight concrete is “modified cementpa

water ratio (Z)”:

f dry exo

V

sity

Z

с

=