Q. Bank for Civil Engineer LDCE Exam - Write note on:- Detailed Specifications of Ballast.

Que Write note on:- Detailed Specifications of Ballast.

Ans :-

1. Ballast should be hard,durable and as far as possible angular along edges/corners,free from weathered portions of parent rock,organic impurities and inorganic residues.

2. Ballast should be cubical in shape as far as possible. Individual pieces should not be flaky and should have generally flat faces with not more than two rounded/sub rounded faces.

3. Preferably machine crushed ballast should be used on B.G. lines. Hand broken Ballast may be used in exceptional cases with approval of CTE/CAO/C.

4. Water absorption should not be more than 1%. But as per CS no. 3 now CAO/CTE can permit relaxation upto 2.5% water absorption for specified areas.

5. Max. values of abrasion and impact should not be more than 30% and 20% respectively.

6. The gradation of ballast on sieve analysis should be as per reqd values as under:- Retained on 65 mm sq. mesh sieve- 5% Maximum Retained on 40 mm sq mesh sieve-40% to 60%Retained on 20 mm sq mesh sieve- not less than 98%