,

(9.

2)

Den

W + P V + V

a a

air

Where V , W, V , V

are

c

a

air

Com pressive strength of

expanded clay concrete, M Pa

correspondingly absolute volumes of

Fig. 9.1 Effect of bulk density of aggregate

cement, water, porous aggregate and air

on density and strength of expanded-clay

per 1 m3 of concrete mix, P is aggregate

concrete on porous and quartz sand.

a

O n expanded clay sand at bulk density of

porosity.

expanded clay gravel, kg/m 3:

1 – 300; 2 – 400; 3 – 500; 4 – 600; 5 – 700; 6 –

800;

O n quartz sand at bulk density of expanded clay

gravel, kg/m 3:

7 – 300; 8 – 400; 9 – 5--; 10 – 600; 11 – 700;

12 - 800

173

Z

Reference books and

0.5

experimental data

processing (Fig. 9.2)

0.4

has shown that

0.3

strength of lightweight

concrete on porous

0.2

aggregates is

0.1

connected with Z

R

parameter by linear

C/W

c, MPa

dependence.

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Fig.9.2. Strength (Rc) dependences of structural expanded clay

concrete on cement-water ratio (C/W) and modified cement-water

ratio (Z):

1 – porosity of expanded clay = 0.4; 2 – 0.55; 3 – 0.7

174

9.2. Design of lightweight concrete with porous aggregates

Design of lightweight concrete is oriented on preliminary determination of

components content that provides obtaining specified parameters at given

conditions. In all cases design of lightweight concrete with compressive

strength must provide specified density.

Design of lightweight concrete can be done:

- at specified types of coarse and fine aggregates with given values of their

density;

- at specified type and density of coarse porous aggregate with possible

selection of sand type;

- at selection both coarse and fine aggregates.

Selection of coarse porous aggregate is conducted on the basis of empirical

data that link their bulk density with density (ρ ) and strength of concrete

c

(R ).

c

175

Statistical treatment of known experimental data shows the possibility of

connection equation application:

R

= 0.008 b

ρ −1