Quality Assurance Handbook for Rural Roads Volume-I - pmgsy
Quality Assurance Handbook for Rural Roads Volume-I - pmgsy
Quality Assurance Handbook for Rural Roads Volume-I - pmgsy
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3. Section-400<br />
B. <strong>Quality</strong> control requirements<br />
1. Materials<br />
The quality requirements of local materials when used as (a) WBM (b) granular layer <strong>for</strong> subbase/<br />
base (c) soil-gravel <strong>for</strong> sub-base/base are given in Table 408.2, column (3).<br />
2. Horizontal Alignment<br />
The edges of subbase and base courses constructed with maximised use of local materials should<br />
be correct within a tolerance limit of (±) 30 mm in plain and rolling terrains and (±) 50 mm in hilly<br />
terrain.<br />
3. Surface Levels<br />
The tolerance in surface levels of sub-base courses constructed with local materials will be restricted<br />
to (+) 10 mm and (–)20 mm. For base courses constructed with local materials, the tolerance in<br />
surface levels will be restricted to (±) 10 mm. A grid of 10 m x 2.5 m may be <strong>for</strong>med to check the<br />
surface levels.<br />
4. Surface Regularity<br />
For sub-base courses constructed with local materials, the maximum permitted difference between<br />
the sub-base and a 3 m straight edge shall be 12 mm <strong>for</strong> longitudinal profile and 10 mm <strong>for</strong> cross<br />
profile. For WBM base constructed with local materials, the maximum permitted difference between<br />
the base and a 3 m straight edge shall be 12 mm <strong>for</strong> longitudinal profile and 8 mm <strong>for</strong> cross profile.<br />
5. <strong>Quality</strong> Control Tests and their Frequency<br />
For the quality control tests and their frequency during construction of sub-base/base courses<br />
built with local materials as such or after appropriate processing, please refer to the relevant Subsection<br />
of this <strong>Handbook</strong>.<br />
C. Do’s and Don’ts<br />
Do’s Don’ts<br />
1. A comprehensive field survey <strong>for</strong> the locally available<br />
materials, industrial wastes, locally available lime etc.<br />
as detailed in Annex 408.1 should be considered an<br />
essential requirement <strong>for</strong> any rural road project.<br />
2. Look <strong>for</strong> any difficult and problematic materials and<br />
local experience on their use in the past.<br />
3. Choose the most appropriate soil stabilization technique<br />
based on the properties of locally available soils and<br />
materials.<br />
4. In case of an expansive clay, if a particular unconfined<br />
compressive strength is aimed at, a two-stage<br />
stabilization with pretreatment of lime in the first stage<br />
and cement in the second stage should be resorted to.<br />
5. Ensure prior testing <strong>for</strong> satisfying the various<br />
requirements be<strong>for</strong>e using industrial wastes like flyash<br />
and slag.<br />
68<br />
1. Do not immediately arrive at the use of hard stone<br />
metal in sub-base or even base course without<br />
considering the results of soil and materials survey<br />
especially when hard stone has to be brought from<br />
long distances.<br />
2. Do not decide on the percentage of stabilizer <strong>for</strong><br />
use in base course without working out<br />
scientifically, the design of mixes.<br />
3. Do not use lime treated soil in the base course<br />
considering the durability aspects of soil-lime<br />
mixes.<br />
4. Do not adopt mechanical stabilization without<br />
ascertaining the available quantities of materials<br />
to be combined.
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