Building Materials, Third Edition

‡2—2‡2€

™ IQQ

„—˜2R

W ‡

 2—2v 22r—˜—

„

 ‡   w—- v  2@A w—-

@A     #—™2     #—™

‡ 2@A 2#  2@A

w

2—˜— I*P I*PDI*VDP*R

ƒ——2—˜— IDP C2Q Q*HDQ*TDR*V C2S

„ 2—˜— I*P —2S*S

…XThey are widely used for wall and ceiling cladding, partitions, doors, perforated acoustic
tiles, railway carriages, bus bodies, etc.

€—™ 2f—22g02f—2@sƒX2QIPWD2IPRHTD2QRUVA•

They are manufactured from particles of wood or other ligno cellulose materials which are
agglomerated, formed and pressed together by the use of an organic binder together in the
presence of heat, pressure or moisture. They are manufactured from small timber pieces and
wood wastes. The latter is first converted into small chips. The moisture content of chips is
reduced to a certain percentage and then some gluing material, usually phenol formaldehyde,
is sprayed. The chips are then spread to form a mat and then pressed in a hydraulic press in
presence of heat and moisture. Particle boards avoid wastage of timber as in its making the
entire volume of the fallen tree can be utilized. The trees used for making particle boards are
eucolyptus, subabool, and rubber wood, and waste of saw mill. These boards provide
dimensional stability, smooth uniform surface, and no difficulty in nailing.

g —™—

Depending on density these are classified as given in Table 4.10.

Uses: These are widely used in buildings, partitions, ceilings, floor slabs, doors, furniture, etc.

f ™+2f—2@sƒX2ITSWA

The core of black boards is made up of
strips of wood each not exceeding 25 mm
in width, forming a slab, glued between
at least two surface veneers (Fig. 4.26).
Veneers used for cross bands and faces
are either rotary cut or sliced and should
be reasonably smooth. Cross band
thickness varies between 1–3 mm and
face veneers between 0.5 to 1.5 mm in
thicknesses. These are available in
thicknesses of 12, 15, 19, 25, 30, 35, 40 and
50 mm. The directions of the grains of the core blocks run at right angles to that of the adjacent
outer veneers.
Block Boards are available in sizes 2400 × 1200, 2100 × 1200, 1200 × 900, 1800 × 1200, 1800 ×
900 mm. Following toleraness are permitted.

p



2R

PT2f™12f—