Building Materials, Third Edition

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™ IRI

18. Match List-I with List-II and select the correct answer using the codes given below the
    lists :
    List-I List-II
    (Terms) (Brief definition)
    A. Sap Wood 1. Separation between adjacent layers of
    tissues
    B. Knot 2. Disintegration caused by fungi
    C. Shake 3. A branch base embedded in timber by
    natural growth
    D. Rot 4. Outer layers of a log of wood
    Codes:
    (a)ABCD (b)ABCD
    1234 3421
    (c)ABCD (d)ABCD
    1324 4312


19. Which of the following in timber is caused by fungus?
    (a) Upsets (b) Foxiness (c) Dry rot (d) Wet rot


20. The moisture content recommended for doors is
    (a) 4 – 8% (b) 8 – 14% (c) 12 – 20% (d) 2 – 4 %


21. Decay of wood is caused in acid medium if pH is
    (a) < 2 (b) < 3 (c) < 4 (d) < 6


22. Tensile strength of wood parallel to grains is about
    (a) 2 (b) 3 (c) 4 (d) 5
    times its compressive strength, parallel to the grains.


23. On application of external stress on timbers, it behaves like
    (a) an elastic material (b) non-elastic material
    (c) viscoelastic material (d) non-viscoelastic material


24. The ratio of tangential shrinkage to radial shrinkage of wood due to reduction in moisture
    content is
    (a) in the range from 3.1 to 5.1 (b) in the range from 2 to 3
    (c) in the range from 1 to 2 (d) less than or equal to 1


25. Which one of the following statements is the correct description of the structure of fibre
    board?
    (a) The slices of superior quality of wood are glued and pressed on the surface of inferior
    wood
    (b) Steamed mass of wood dusts, wood wool and other vegetables fibres are pressed hard
    to a thickness varying from 3 mm to 12 mm
    (c) Thin and narrow wood shavings are soaked in a refractory binder material and
    pressed hard
    (d) Wood veneer backed by fabric mat


26. Knots reduce the tensile strength of wood
    (a) along the grain (b) across the grain
    (c) tangential to the grain (d) none of the above