trade has our best wishes for his success.--_The
Engineer._

* * * * *

CONCRETE.[1]

[Footnote 1: Read July 5, 1887, before the Western Society of
Engineers.]

By JOHN LUNDIE.

The subject of cement and concrete has been so well treated of in
engineering literature, that to give an extended paper on the subject
would be but the collection and reiteration of platitudes familiar to
every engineer who has been engaged on foundation works of any
magnitude. It shall therefore be the object of this communication to
place before the society several notes, stated briefly and to the
point, rather as a basis for discussion than as an attempt at an
exhaustive treatment of the subject.

Concrete is simply a low grade of masonry. It is a comparatively
simple matter to trace the line of continuity from heavy squared
ashlar blocks down through coursed and random rubble, to grouted
indiscriminate rubble, and finally to concrete. Improvements in the
manufacture of hydraulic cements have given an impetus to the use of
concrete, but its use is by no means of recent date. It is no uncommon
thing in the taking down of heavy walls several centuries old to find
that the method of building was to carry up face and back with rubble
and stiff mortar, and to fill the interior with bowlders and gravel,
the interstices of which were filled by grouting--the whole mass
becoming virtually a monolith. Modern quick-setting cement
accomplishes this object within a time consistent with the
requirements of modern engineering works; the formation of a
monolithic mass within a reasonable time and with materials requiring
as little handling as possible being the desideratum.

The materials of concrete as used at present are cement, sand, gravel,
broken stone, and, of course, water. It is, perhaps, unnecessary to
say that one of the primary requirements in materials is that they
should be clean. Stone should be angular, gravel well washed, sand
coarse and sharp, cement fine and possessing a fair proportion of the
requirements laid down in the orthodox specification. The addition of
lime water, saccharated or otherwise, has been suggested as an
improvement over water pure and simple, but no satisfactory
experiments are on record justifying the addition of lime water.

Regarding the mixing of cement and lime with saccharated water, the
writer made some experiments several months ago by mixing neat cement