Question

Which size of particles do you think are better for civil engineering structures?

Answer 1

Genrally aggregates are classified as -

I) Rounded aggregates

ii) Irregular aggregates

iii) Angular aggregates

iv) Flaky aggregates

ROUNDED AGGREGATES THOUGH HAVE LEAST AMOUNT OF VOIDS ARE GENERALLY NOT CONSIDERED FOR CIVIL ENGINEERING STRUCTURES BECAUSE THEY SHOW POOR INTERLOCKING AND WEAK BOND STRENGTH.

GENERALLY

40mm SIZE FOR NORMAL STRENGTH CONCRETE.

20mm SIZE FOR HIGH STRENGTH CONCRETE.

Constraint to the nominal maximum size of aggregates are due to

i) Clear distance between R/F

ii) Cover requirements

Generally 20 mm size aggregates are used but using 40mm may prove to be economical in some cases like substructures.

If the space is less even 12.5 mm size aggregates are used to satisfy minimum spacing requirements.

FOR MASS CONCRETING DAMS- 150mm Size is often used.

FOR SHOTCRETE- 8mm size aggregates are used.