CO129-525-5 Colfix road surfacing materials 21-2-1930 - 26-5-1930 — Page 14

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presence in the road surface is not always an advantage, and,

unless the soap is carefully chosen, may be the reverse.

7. No bituminous emulsion can be stored indefinitely;

probably six to eight weeks would be the limit of safe

storage in Hong Kong. After that period the asphalt

mass to the

gradually separates out and falls in a viscous

bottom of the containing drums; the soap in the emulsion also

deteriorates and no amount of "rolling" the drums will re-mix

it. If hard water were used in making the emulsion and the

Soap a cheap soap, either or both of these circumstances

would lead to still earlier deterioration of the emulsion.

8. Bituminous emulsion freshly made and of good

T

quality may be suitable for surface dressing bitumenised

roads, or used "blinded" with gravel on wood pavement

in certain climates, but as a substitute for "hot-mix" in

road construction, price for price, we are of opinion that

it is not to be considered.

9. If bituminous emulsion is to be used at all we

recommend that it should be made by the Public Works

Department, locally, and in the Fourth Crown Agents' Bulletin

Article VII (acopy of which is attached) the method of

manufacture and also the plant requisite for the process are

described in detail.

It will be seen that the cost of the

plant is not excessive and the saving effected by making the

emulsion on the spot exactly and only when required, compared

with the importation of any of the proprietary brands would

be considerable.

I have the honour to be,

Sir,

Your obedient servant,

Wat wichhart

for Crown Agents.