Building Materials, Third Edition

QH f2w—

—

v——X These are caused by the entrapped air in the voids of clay. Laminations produce
thin lamina on the brick faces which weather out on exposure. Such bricks are weak in
structure.

PIQ rie†‰2h…„‰2f…‚x„2gve‰2f‚sguƒ2@sƒX2PIVHA

These are similar to burnt clay bricks and of the same size but with high compressive strength.

g—™—



Class 400: compressive strength not less than 40.0 N/mm^2 but less than 45.0 N/mm^2.

Class 450: compressive strength not less than 45.0 N/mm^2.

These are further subdivided as subclasses A and B based on tolerance.

„—™

Dimensions (cm) Tolerances (mm)

Subclass A Subclass B

9± 3± 7

19 ± 6 ± 15

‡— —˜#X should not be more than 10 per cent after 24 hours immersion in water.

i™™X should be nil.

f X should be less than 2500 kg/m^3.

PIR f…‚x„2gve‰2€i‚py‚e„ih2f‚sguƒ2@sƒ2X2PPPPA

Perforated Bricks contain cylindrical holes throughout thier thickness, have high compressive
strength and less water absorption. These bricks are light in weight, require less quantity of
clay and drying and burning of these bricks is easy and economical. The direction of perforations
can be vertical or horizontal. These are used in building walls and partitions. The area of
perforations should not exceed 30 to 45% of the area of face. In case of rectangular perforations,
larger dimensions should be parallel to longer side of the brick.

h

These are available in the following sizes.
(i) 19 × 9 × 9 cm.
(ii) 29 × 9 × 9 cm.

„—™

Dimensions Tolerances

(cm) (mm)

9± 4

19 ± 7

29 ± 10