Storage stability of bitumen emulsion

Further flocculation of bitumen globules, attributed to the weight of the mass of globules formed and the dominant hydrostatic pressure, causes fusion of the globules and the formation of a unified bituminous mass. This phenomenon is called coalescence. Coalescence is an irreversible process. Thus, after coalescence begins, the bitumen content of the emulsion is drastically reduced and the emulsion is unsuitable for use. 

The size of bitumen globules, which should normally be between 0.5 and 0.015 mm for at least 85% of the globules, is mainly affected by the distance of the gap between the rotor and the stator. If for some reason (mainly metal wear) the gap becomes bigger, the emulsion produced will be more coarse . The size of the globules can also be affected by the low temperature of the bitumen or the aqueous solution during the emulsification process. 

The storage stability of the emulsion may also be affected by the viscosity of the emulsion, the specific gravity of the bitumen and the emulsifier content of the emulsion. 

Emulsions with relatively low viscosity and emulsions produced by bitumen with relatively high specific gravity are more prone to settlement than emulsions with high viscosity and bitumen of lower specific gravity. The use of an increased emulsifier quantity in the system decelerates the settlement rate. However, this solution should not be preferred, since the emulsifier constitutes the most expensive ingredient and it will have further effects, such as increase, mainly, of the emulsion break time. 

Emulsion storage stability is quickly determined by the 24 h settlement test (see Section 4.20.13). The size of bitumen globules, as well as their size distribution, can be determined using electronic microscopes or electronic apparatuses for sieve analysis. A quick and far less costly method to determine the suitability of the bitumen emulsion in road 

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