This set of Basic Civil Engineering test focuses on “Defects and Preservation of Timber”.
1. Which of the below is a natural defect occurring in timber?
Explanation: The other options are those defects that occur after the felling of tree.
2. How many types of shakes are there?
Explanation: The 5 types of shakes are star, heart, cup, ring and radial shakes.
Explanation: Upsets indicates wood fibres that are injured by crushing or compression. It is due to improper felling of trees.
4. __________ defects is indicated by red/yellow tinge in wood.
Explanation: Druxiness is indicated by white spots. Callus is soft tissue that covers wound of tree. Burls are swelling on the surface of tree.
5. A crack which separates wood fibres is called:
Explanation: Check is crack that does not extend from one end to another. A check that extends from one end to other is called split.
6. Diagonal grain is a defect formed due to improper:
Explanation: Diagonal grain is caused due to improper sawing of timber. It is indicated by diagonal marks on straight grained surface of timber.
7. Which of the following is not a cause of decay of timber?
a) Lack of ventilation
b) Alternate dry and wet conditions
c) Absence of moisture
d) Moisture accompanied by heat
Explanation: Presence of moisture and sap accelerate the decay of timber.
8. What causes dry rot in timber?
c) White ants
Explanation: A fungi called Meruliam Lechrymans causes the dry rot. It reduces wood to fine powdery substance. It first sets in the sap wood and advances. It makes timber brittle, cohesion is lost and finally powdered.
9. A good preservative should:
a) Be poisonous
b) Be unaffected by heat and moisture
c) Have pleasant odour
d) Have white colour
Explanation: A good preservative should be poisonous to fungi, insects, etc. It should odourless and colourless.
10. Which of the below preservative, with their examples correctly match?
a) Type 1 – DDT
b) Type 2 – Coal
c) Type 3 – Boric acid
d) Type 4 – Benzene
Explanation: There are only 3 types of preservative as per IS 401. Type 1 is oil type and coal, tar are examples of it. Type 2 is organic solvent type with benzene, DDT as examples. Type 3 is water borne type and boric acid, zinc chloride are examples of it.
11. Ascue is a:
a) Defect by insects
c) Natural defect
d) Type of marine borer
Explanation: Ascue – copper chrome arsenic composition, is a type 3 preservative developed by Forest Research Institute. It is available in powdered form. Ascue solution is prepared by mixing 6 parts powder to 100 parts water, by weight.
12. Which method of application of preservative is suitable for moist timber?
a) Pressure application
b) Brushing and spraying
d) Hot and cold tank treatment
Explanation: Timber is placed in air tight cylinder, vacuum is created and maintained till air bubbles are destroyed. Preservative is then pumped into the air tight cylinder.
13. Which of the following makes the timber look sound but might fail it without pre-warning?
a) Marine borers
c) White ants
Explanation: Beetles make thousands of deep small holes while the white ants or termites develop tunnels inside the timber in various directions.
14. The defect indicated by curvature formed in transverse direction is:
Explanation: Bow is curvature in direction of length. Spring is curvature in its own plane. Twist occurs when timber plank has spirally distorted along its length.
Sanfoundry Global Education & Learning Series – Basic Civil Engineering.
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