Grameen Sampark Final April 0... - pmgsy
Grameen Sampark Final April 0... - pmgsy Grameen Sampark Final April 0... - pmgsy
8 materials used for production of blocks; physical requirement, test methods, sampling and acceptance criteria etc., have already been presented in BIS Code [8]. Bedding Sand and Joint Filling Sand It is a well established fact that if proper attention is not paid to the quality of bedding sand, and if the thickness of bedding sand layer is not kept uniform, serious irregularities in surface profile can occur result and consequently excessive differential deformations and rutting can early in the service life of block pavement. The gaps in between the two adjacent paving blocks (typically about 3 mm wide) need to be filled in with sand which should relatively be finer than the bedding sand. The gradations of bedding sand and joint filling sand are given in Table 1. It is necessary to restrict the fines (silt and/ or clay, passing 75 micron sieve) to about 10 percent, since excessive fines make joint filling very difficult. Similarly, it is not advisable to use cement in the joint filling sand, which would not only make difficult to completely fill the joints, but may also adversely affect the desired flexibility characteristics of the paving block layer. The joint filling sand should preferably be as dry as possible; otherwise complete filling of joints will be difficult [7]. Table 1: Gradations of Bedding Sand and Joint Filling Sand IS Sieve Size Bedding Sand Joint Filling Sand Percent Passing by Weight 9.52 mm 100 - 4.75 mm 95-100 - 2.36 mm 80-100 100 1.18 mm 50-95 90-100 600 micron 25-60 60-90 300 micron 10-30 30-60 150 micron 0-15 15-30 75 micron 0-10 0-10 Grameen Sampark Base and Sub Base Materials The main purpose of providing base materials are the load spreading properties to disperse stresses to the subgrade level and to provide the desired drainage characteristics, which would have significant bearing on performance of a block pavement. Although, local availability and economics generally dictate the choice of base materials at the design stage, yet the commonly used materials considered suitable for base courses are unbound crushed rock, water-bound macadam, wet mix macadam, cement bound crushed rock/ granular materials, and lean cement concrete/ dry lean concrete etc. In broad terms, wherever the subgrade is weak (CBR value below 5), the use of bound granular materials, like, cement treated crushed rock, should be preferred
while for high strength subgrade, unbound crushed rocks may be used. The climatic and environmental factors also need to be considered during the choice of base materials. Sub-base is essential where commercial traffic is expected. The quality of sub-base materials is inferior to the base materials and may include natural gravels, cement treated gravels, sands and stabilized subgrade materials etc. The quality of sub-base materials should be in conformance with IRC: 37-2001. Construction of Interlocking Concrete Block Pavement Sequencing of Laying Operations The sequencing of laying operations (Figure-2) for construction of block pavement should be as follows [8]: (i) Installation of sub-surface drainage structures Basecourse compacted and inspected Beddind sand slockpited ahead of screeding Edge restraint constructed on basecourse Figure 2: Sequencing of Laying Operations Sand bedding course screeded Laying face Paving Units laid Pradhan Mantri Gram Sadak Yojana (ii) Leveling and compaction of subgrade (iii) Provision and compaction of sub-base course (where needed) (iv) Provision and compaction of base-course and checking for the correct profile (v) Installation of edge restraints (vi) Provision and compaction of bedding sand (vii) Laying of blocks and interlocking (viii) Application of joint sealing sand and compaction (ix) Cleaning of surface (x) Filling any remaining empty portions in the block layer, especially near edge restraint blocks with in situ concrete. Cut infill units Paving Joint-filling Units sand compacted placed Pavement completed allowing access Pallets of paving units placed as close as possible to work-lace Site access and starting point Grameen Sampark 9
- 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 10 and 11: 10 Construction of Sub grade This i
- 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
while for high strength subgrade, unbound crushed<br />
rocks may be used. The climatic and environmental<br />
factors also need to be considered during the choice of<br />
base materials. Sub-base is essential where commercial<br />
traffic is expected. The quality of sub-base materials is<br />
inferior to the base materials and may include natural<br />
gravels, cement treated gravels, sands and stabilized<br />
subgrade materials etc. The quality of sub-base<br />
materials should be in conformance with IRC: 37-2001.<br />
Construction of Interlocking Concrete Block<br />
Pavement<br />
Sequencing of Laying Operations<br />
The sequencing of laying operations (Figure-2) for<br />
construction of block pavement should be as follows<br />
[8]:<br />
(i) Installation of sub-surface drainage structures<br />
Basecourse<br />
compacted<br />
and inspected<br />
Beddind sand<br />
slockpited ahead<br />
of screeding<br />
Edge restraint constructed on<br />
basecourse<br />
Figure 2: Sequencing of Laying Operations<br />
Sand bedding<br />
course<br />
screeded<br />
Laying face<br />
Paving<br />
Units<br />
laid<br />
Pradhan Mantri Gram Sadak Yojana<br />
(ii) Leveling and compaction of subgrade<br />
(iii) Provision and compaction of sub-base course<br />
(where needed)<br />
(iv) Provision and compaction of base-course and<br />
checking for the correct profile<br />
(v) Installation of edge restraints<br />
(vi) Provision and compaction of bedding sand<br />
(vii) Laying of blocks and interlocking<br />
(viii) Application of joint sealing sand and compaction<br />
(ix) Cleaning of surface<br />
(x) Filling any remaining empty portions in the block<br />
layer, especially near edge restraint blocks with in<br />
situ concrete.<br />
Cut infill<br />
units<br />
Paving Joint-filling<br />
Units sand<br />
compacted placed<br />
Pavement<br />
completed<br />
allowing access<br />
Pallets of paving units placed as<br />
close as possible to work-lace<br />
Site access and starting point<br />
<strong>Grameen</strong> <strong>Sampark</strong> 9
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