Specification Part 3 - Road & Bridge Works - Urban Administration ...

2. Remove all vegetation and other extraneous material etc. from the sub grade already prepared, lightly
sprinkle with water, if necessary, and roll with two passes of 80-100 KN road roller or any other suitable
compactor/ vibratory other
3. The sub base material should be spread in layers not exceeding 100 mm compacted thicknesses. If suitable
vibratory rollers are available, the compacted thickness of layer can be up to a maximum of 225 mm.
4. Each layer shall be uniformly spread and thoroughly compacted. Spreading and compaction shall be carried
out as per clause surface finish and quality control of work shall be as per clause 401.5.
5. Approval of the site engineer should be obtained for each layer. such an approval would require surface level
and compaction control tests.
6. PRECAUTIONS:-
1. Ensure uniform mixing of GSB material and water by mechanical means like tractor towed implements.
2. Ensure that on clayey sub grades, the percent fines passing 75 micron in the GSB material do not exceed
5%.
3. Do provide aggregate plugs at the exposed edges of GSB where extended over the full formation width.
4. Look for soft patches, if any, and rectify ‘them by removing or adding fresh material and compacting the same
thoroughly.
404. WATER BOUND MACADAM SUB -BASE/BASE5
404.1. Scope
404.1.1. water bound macadam sub -base/base5 work shall consist of clean, crushed aggregates me chemically
interlocked by roiling and bonding together with screening, binding material where necessary and water laid on
a properly prepared sub grade/ sub-base/ base or existing pavement, and finished in accordance with the
requirements of these Specifications and in close conformity with the lines, grades, cross-sections and thickness
as per approved plans or as directed by the Engineer in charge.
404.1.2. To lay water bound macadam on an existing thin black topped surface is not desirable without
providing adequate drainage facility for water that would get accumulated at the interface of existing bituminous
surface and water bound macadam.
404.2, Materials - following material are required for water bound macadam:-
(i) Coarse aggregates,(ii) Screenings, (iii) Binding material.
404.2.1. Coarse aggregates: - materials which are used as coarse aggregates and physical requirement of
coarse aggregates are given below:-
(a)Coarse aggregates shall be either crushed or broken stone, crushed slag, over burnt over burnt brick
aggregates or any other naturally occurring aggregates such as kankar and laterite of suitable quality.
(b)Materials other than crushed or broken’ stone and crushed slag shall be used in sub-base courses only.
(c)If crushed gravel/ shingle are used, not more than 10 per cent by weight of the gravel/ shingle pieces .passed
through 4.75 mm sieve shall have at least two fractured faces.
(d)If the water absorption value of the coarse aggregate is greater than 2 per cent, the soundness test shall be
carried out on the material delivered to site as per IS: 2386 (Part 5).
(e)The aggregates shall conform to the physical requirements set forth in Table 400-6.