Grameen Sampark Final April 0... - pmgsy
Grameen Sampark Final April 0... - pmgsy Grameen Sampark Final April 0... - pmgsy
10 Construction of Sub grade This is the foundation layer over which the block pavement is constructed. Like in conventional pavements, the depth of water table should not be at a level of 600 mm or higher, below the subgrade level. It should be compacted in layers of 150 mm thickness. The prepared subgrade should be graded and surface dressed to a tolerance of ± 20 mm of the design levels, and its surface evenness should have a tolerance of within 15 mm under a 3 m straight edge [7]. Construction of Base and Sub-base Layers Base course and Sub-base course are constructed in accordance with the standard procedures contained in relevant IRC specifications like IRC:37-2001; IRC:50- 1973; IRC:51-1993; IRC:63-1976; IRC:19-1997. When cement treated bound base is proposed it may be constructed using rolled dry lean concrete as IRC:SP- 49-1998. The quality control methods, as specified in IRC: SP-11-1988 shall apply. Constructing these layers to the proper level and grade is very much essential to maintain the top surface level and surface regularity of the block pavement surface. Grameen Sampark Edge Restraint Blocks and Kerbs Concrete blocks subjected to traffic tend to move sideways and forward due to braking and maneuvering of vehicles. The tendency to move sideways has to be counteracted at edges by provisions of special edge blocks and kerbs. The edge blocks should be designed and anchored to the base such that the rotation or displacement of blocks is resisted [7]. These blocks are to be made of high strength concrete for withstanding the traffic wheel-loads without getting damaged. These members should be manufactured or constructed in-situ in order to have at least a 28-days characteristic compressive strength of 30 MPa or flexural strength of 3.8 MPa. As far as possible, the edge blocks should have vertical face towards the inside blocks. Where the space does not easily permit the use of plate vibrators, dhurmut or manual compactor using small size plate rammer may be used. The road kerbs provided on edges of roads also serve the purpose of edge blocks. In case the kerbs are not provided, it has to be replaced by the edge strips. In case of heavy traffic, 150 mm x 150 mm (height x width) plain cement concrete (M-25) may also be provided over dry lean concrete to give further confinement to the blocks. In-between the edgerestraint blocks, cement mortar (1: 6, cement: coarse sand) may be used in place of sand for sealing of blocks. Placing and Screeding of Bedding Sand The thickness of sand bedding after compaction should be in the range of 20-40 mm, whereas, in the loose form, it should be 25 to 50 mm. It is preferable to restrict the compacted thickness to about 20-25 mm to reduce the risk of any localized over-compaction, which would affect the final block surface level. Bedding sand should not be used to fill-up local depressions on the surface of base or sub-base layers. The depressions, if any, should be repaired with same base or sub-base material in advance before placing the sand. The sand of specified gradation, should be uniformly in loose condition, and should have uniform moisture content. Optimum moisture content is when sand is neither too wet nor too dry and has moisture of about 6 to 8 percent.
Requirement of sand for a day's work should be prepared and stored in advance and covered with tarpaulin or polythene sheets. The processed sand so obtained is spread with the help of screed boards to the specified thickness and levels. The screed boards are provided with nails at 2-3 m apart which when dragged gives the required thickness. The length of nail should take into account the surcharge to be provided in the uncompacted thickness. Alternatively, the screed can be dragged on edge strips kept on both sides as guides [7]. Laying of Paving Blocks Blocks can be laid generally by manual labour but mechanical aids like hand-pushed trolleys can expedite the work. Normally, laying should commence from the edge strips and proceed towards the central line. When dentated blocks are used, the laying done at two fronts will create problem for matching joints in the middle. Hence, as far as possible, laying should proceed in one direction only, along the entire width or area to be paved [8]. Pradhan Mantri Gram Sadak Yojana While locating the starting line, the following should be considered: On a sloping site, start from the lowest point and proceed to up-slope on a continuous basis, to avoid down-slope creep in incomplete areas. In case of irregular shaped edge restraints or strips, it is better to start from straight string line. Influence of alignment of edge restraints on achieving and maintaining the laying bond. Laying Patterns The blocks can be placed in different bonds or patterns depending upon the specific requirements. Some popular bonds commonly adopted for block paving are: (i) Stretcher or running bond (ii) Herringbone bond and (iii) Basket weave or parquet bond etc. The typical layouts of these bonds are given in Figure 3. O (a) Stretcher or Running Bond (b) Parquet or Basket Weave (c) 45 Herringbone Bond O (d) 90 Herringbone Bond (e) Parquet Derivative (f) Double - V (g) Double Herringbone (h) Herringbone (i) Herringbone Bond Figure 3: Laying Patterns of Paving Blocks Grameen Sampark 11
- Page 2 and 3: In this Issue Editorial 3 Potential
- Page 4 and 5: 4 Potential Applications of Interlo
- Page 6 and 7: 6 Interlocking Concrete Block Pavem
- Page 8 and 9: 8 materials used for production of
- Page 12 and 13: 12 Typical Pavement Compositions Ty
- Page 14 and 15: 14 Guidelines for the use of In
- Page 16 and 17: 16 layers due to repeated applicati
- Page 18 and 19: 18 Subgrade Failure Criterion The b
- Page 20 and 21: 20 A maximum of 50mm rut depth was
- Page 22 and 23: 22 Stabilization of Soil Subgrade w
- Page 24 and 25: 24 Changes in Cohesion and Direct
- Page 26 and 27: 26 Increase in the C.B.R. value is
- Page 28 and 29: 28 Laboratory Test (Under Vertical
- Page 30 and 31: 30 Apart from the above, both faces
- Page 32: News in Brief General Body Meeting
Requirement of sand for a day's work should be<br />
prepared and stored in advance and covered with<br />
tarpaulin or polythene sheets. The processed sand so<br />
obtained is spread with the help of screed boards to the<br />
specified thickness and levels. The screed boards are<br />
provided with nails at 2-3 m apart which when dragged<br />
gives the required thickness. The length of nail should<br />
take into account the surcharge to be provided in the<br />
uncompacted thickness. Alternatively, the screed can<br />
be dragged on edge strips kept on both sides as guides<br />
[7].<br />
Laying of Paving Blocks<br />
Blocks can be laid generally by manual labour but<br />
mechanical aids like hand-pushed trolleys can expedite<br />
the work. Normally, laying should commence from the<br />
edge strips and proceed towards the central line. When<br />
dentated blocks are used, the laying done at two fronts<br />
will create problem for matching joints in the middle.<br />
Hence, as far as possible, laying should proceed in one<br />
direction only, along the entire width or area to be<br />
paved [8].<br />
Pradhan Mantri Gram Sadak Yojana<br />
While locating the starting line, the following should be<br />
considered:<br />
<br />
<br />
<br />
On a sloping site, start from the lowest point and<br />
proceed to up-slope on a continuous basis, to<br />
avoid down-slope creep in incomplete areas.<br />
In case of irregular shaped edge restraints or strips,<br />
it is better to start from straight string line.<br />
Influence of alignment of edge restraints on<br />
achieving and maintaining the laying bond.<br />
Laying Patterns<br />
The blocks can be placed in different bonds or patterns<br />
depending upon the specific requirements. Some<br />
popular bonds commonly adopted for block paving are:<br />
(i) Stretcher or running bond (ii) Herringbone bond and<br />
(iii) Basket weave or parquet bond etc. The typical<br />
layouts of these bonds are given in Figure 3.<br />
O<br />
(a) Stretcher or Running Bond (b) Parquet or Basket Weave (c) 45 Herringbone Bond<br />
O<br />
(d) 90 Herringbone Bond<br />
(e) Parquet Derivative (f) Double - V<br />
(g) Double Herringbone (h) Herringbone (i) Herringbone Bond<br />
Figure 3: Laying Patterns of Paving Blocks<br />
<strong>Grameen</strong> <strong>Sampark</strong> 11
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