365
9.
Concrete Substructure I would have been disposed to recommend that the entire dam should have been
a homogenous structure of Portland Cement Concick throughout but that the undue cost of the freight of
sement to Hong Kong, and the great difficulty, experienced in preserving that material for ceny time fit for use in the hot and excessively damp climate of China render it doubtless more prudent to fall back upon a masonry, fabric, the material for which in the shape of execellent building stone, is lying at hand on the spot. It is intended however that the base or substructure of the dam should be of concrete as shown in the Drawings, for the reason that concrete if properly laid and rummed in the touch
compact mass is likely to prove perfectly watertight foundation than a masonry one, the operation of building which, would beattended with considerable inconvenience in consequence of the irregular and broken shape of the
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The concrete substructure, should be carried up always with an uneven & rough surface tat irregular :
levels. Joints between smooth hard surfaces must be carefully avoided and in no case should fresh concrete be laid upon old work that has already set without the top surface of the latter being previously dug into with pick cuces for the purpose of creating a rough
4 broken surface.
The proportions of the concrete must vary according t the state of preservation of the particular shipment of cement in use, but the standard proportions recommended subject to such modifications as the Engineer on the spot
deem necessary, may be 5 park of broken stone &tpart of clean sharp sand toone part of Portland Cement of approved quality the whole to be thoroughly well mixed and punned in sike until the cement mortar wells up to the surface.
Quarry Chippings and stone for the concrete may had in abundance from the kennel mouth close by, while the Tylam stream Sam informed by Mr. Trice will afford
exhaustless supply of excellent send. Forl
be
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