To summarise the information upon this point, it appears that
it is better to use fresh water for all purposes, but if, for
the sake of economy, saline matters are introduced into the
concrete, either by using sea water for mixing or by using sand
and shingle from the beach, the principal effect will be to
delay the time of setting to some extent, but the ultimate
strength of the concrete will probably not be seriously
affected. When the concrete is placed in position the portion
most liable to be destroyed is that between high and low water
mark, which is alternately exposed to the action of the sea and
the air, but if the concrete has a well-graded aggregate, is
densely mixed, and contains not more than two parts of sand to
one part of cement, no ill-effect need be anticipated.




CHAPTER XII

DIVING.


The engineer is not directly concerned with the various methods
employed in constructing a sea outfall, such matters being left
to the discretion of the contractor. It may, however, be
briefly stated that the work frequently involves the erection
of temporary steel gantries, which must be very carefully
designed and solidly built if they are to escape destruction by
the heavy seas. It is amazing to observe the ease with which a