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Performance Evaluation Report on Rural Roads Constructed Using CRRI-Bitchem Cold Mix in Different District of Assam during 2008-2009 1

PERFORMANCE EVALUATION REPORT ON RURAL ROADS
CONSTRUCTED USING CRRI-BITCHEM COLD MIX IN
DIFFERENT DISTRICT OF ASSAM

1.0 Introduction

Bitumen in different forms has been in use in construction and maintenance of bituminous pavements. Bitumen,
being a thermoplastic material and semi solid with high viscosity at ambient is not workable. It can be
transformed into workable form in three ways (a) by heating, (b) by blending with petroleum solvents to form
cutbacks, and (c) by emulsifying in water to form bitumen emulsion.

Bitumen is heated to elevated temperature around 150-160 degree centigrade to make it workable state which is
accompanied by the emission of hydrocarbon and other pollutants resulting in degradation of environment. The
conventional method of hot mix and hot laid type bituminous road construction is some time not feasible and even
not desirable in areas such as heavy rainfall area where intermittent rains throughout the year affect production
and laying of hot mix and also in areas of cold climate where hot bitumen gets solidified quickly and losses its
binding property as soon as it comes in contact with the existing cold pavement surface at altitude. Cut back
bitumens were, therefore specified to overcome such problems but these too require little heating and are
accompanied by emission of solvent oil used as cutter which also creates environment problem. Two major issues
namely environment problem and energy conservation have focused the attention of researchers and road
builders towards new technologies which are environment friendly and energy efficient. The use of bitumen
emulsion for road construction can in a big way bring about both energy saving and pollution control by
eliminating heating of both bitumen and aggregate.

1.1 Bitumen Emulsion

Bitumen emulsion is a liquid form of bitumen in which a substantial amount of bitumen is suspended in a finely
divided condition in an aqueous medium. Bitumen is the dispersed phase and water is the continuous phase.
Stability of an emulsion is achieved by the use of an emulsifying agent contained in the aqueous phase. Based on
the type of the emulsifier used, Bitumen emulsions can be:

Anionic: Bitumen globules being electro-negatively charged and the aqueous phase,
alkaline.
Cationic: Bitumen globules being electro-positively charged and the aqueous phase,
acidic.
Non-ionic: In these Bitumen globules are neutral.

QSP/MR/19/ ACED/BTCM/214/2013 CSIR-NEIST/CNP-462