Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

3. Section-1500
1503: RECTANGULAR CONCRETE BLOCK PAVEMENT
A. Methodology
1. The rectangular concrete blocks should preferably be cast using block manufacturing machine or
semi mechanized means as per clause 1503.6 of MoRD specifications.
2. Ensure a trial length of 30 m is laid for demonstrating the procedure and equipment for laying the
main pavement.
3. Prepare the subgrade to the specified grades, lines and cross-sections and uniformly compact to
the design strength. Subgrade shall have a camber of 3 percent and the soaked CBR not less than
4 percent.
4. Lay cement concrete pavement over a 75 mm thick WBM (Gr.2 or 3) base layer, extended by at
least 150 mm beyond the edge blocks. The subbase layer below the WBM base shall be a GSB layer
or WBM Gr.1 100 mm compacted thickness.
5. Lay 25 mm thick (compacted) bedding sand conforming to grading requirements indicated in
Table No. 1503.1 uniformly over the base course. The bedding sand shall have about 6 percent
moisture content to facilitate its spreading and compaction and shall be compacted with a hand
rammer, preferably plate compactor and the surface levelled using a screed.
6. The pattern for paving blocks shall be herringbone or stretcher. The joints between stretcher bond
shall be staggered by about half the length of stretcher.
7. The concrete blocks for pavement shall be 450 mm x 300 mm x 150 mm size and Restraint blocks
shall be of 300 mm x 300 mm x 200 mm size. The cement content shall be between 310 and 425 kg/
cum unless specified otherwise in the contract. Extra blocks to the extent of 5 percent should be
manufactured and properly stored for subsequent use for maintenance purposes.
8. The width of joint shall be between 2 mm and 4 mm. On curves non-uniform joint width may
have to be resorted to. When space does not permit the use of cut piece of blocks, the use of
premixed or dry packed concrete is recommended.
9. After a section has been paved, start compaction with a suitable vibratory plate compactor in the
following sequence of operations.
(i) Apply three passes of a standard vibrating plate compactor of weight 0.9 kN, with plate
area not less than 0.3 m 2
(ii) Spread a thin layer of joint filling sand on the top of paved blocks and sweep into joints
using suitable brooms. The sand shall be vibrated into the joints by moving the vibrating
plate compactor and more sand shall be applied till the joints are well packed.
(iii) Clean excess sand from the top of block pavement.
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