pmgsy annexure 5.1

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5/24/13 Annexure 5.4

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National Rural Roads Development Agency

Annexure 5.4

(See para 5.7

PRADHAN MANTRI GRAM SADAK YOJANA (PMGSY)

GUIDELINES ON USE OF LOCAL MATERIALS

1. Use of Better Granular Soil

Well-graded soils with low plasticity index values have better engineering properties and should be reserved for use as

improved subgrade/ sub-base or surfacing in the case of earth roads. Such soils can be identified by their high Procto

density and low PI values.

2. Stabilisation of Local Soils

A variety of techniques are available for stabilising local soils for improving their engineering properties, but not all th

techniques are applicable to all types of soils. A brief description of the stabilisation mechanism and applicability of the

individual techniques are given in Table 1. This may be referred to for choosing the most appropriate technique for stabilising

the soil at site. The mix proportions are generally worked out in the laboratory based on soaked CBR value.

Table 1

Mechanism and Requirements of Soil Stabilisation Techniques

Sl. No. Technique Mechanism Application

1. Mechanical stabilisation Blending missing fractions (e.g.,

clay with sand and sand with

clay) so as to produce a mass ofmaximum possible density with

plasticity within limits. A smooth

grading similar to that given by

Fullers grading rule* is adopted

to work out the proportion of the

missing fractions to be blended.

Sands, moorum/ gravel having

missing fractions and clayey

soils can be stabilised by thistechnique.

2. Lime stabilisation Lime in hydrated form reacts

with the clay minerals in the soil

to cause (i) immediate reduction

in plasticity and increase in CBR

because of cationic exchange,

flocculation and agglomeration,

which may be reversible under

certain conditions, and (ii) long

term chemical reaction with the

clay minerals to produce

cementitious products which

bind the soil for increased

strength and stability.

Medium and heavy clays having

a PI of at least 10 and containing

at least 15% of materials finer

than 425 micron are suitable.

However, some soils though

containing clay fractions may

not produce the long-term

chemical reaction because of

the presence of organic matter

(> 2%), or soluble

sulphate/carbonate (> 0.2%) etc.

For lime stabilisation to be

successful, it will be desirable to

test the soil for lime reactivity. A

soil whose 7-day unconfined

compression strength increases

by at least 3 kg/cm2 with lime

treatment can be considered
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lime reactive.

3. Cement stabilisation The hydrated products of cement

binds the soil particles, the

strength developed depending on

the concentration of cement and

the intimacy with which the soil

particles are mixed with cement.

A high cement content of the

order of 7-10% can produce a

hard mass having a 7-day

compressive strength of 20

kg/cm2 or more, and this usually

goes by the term soil-cement.

However, a smaller proportion of

2-3% cement can improve the

CBR value to more than 25, and

the material going by the term

cement-modified soil can be

advantageously used as sub-

base/base for rural roads.

Generally, granular soils free of

high concentration of organic

matter 2% deleterious salts

(sulphate and carbonate


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4. Use of Bricks and Overburnt Brick Metal

In alluvial plains where hard stone aggregates are normally not available within economical leads, the general specification

adopted for sub-base and base courses is to provide brick soling. Either flat bricks or bricks on edge or broken brick ballast

can be used depending on the thickness requirements. The bricks should be of good quality and well burnt. Before laying

flat bricks or brick-on-edge, it is desirable to provide a cushion of sand above the earth subgrade.

5. Other Waste Materials

Many other waste materials like quarry waste, marble slurry dust, other metallic slags are available in many parts of the

country. Laboratory and field studies conducted on some of these materials have indicated that such materials can be

utilised for construction of lower layers of pavement and/ or embankment. However, before embarking on use of such

materials, detailed characterisation and design of mix through a reputed laboratory would be needed.

Operations Manual for Rural Roads
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pmgsy annexure 5.1

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