16

Advantages of Lime in Construction
By TYRRELL B. SHERTZER,
Construction Engineer Eastern Bureau Nat. Lime Ass n.
THAT
engineers, architects and constructors rec-
ognize the value of hydrated lime mixtures in
conchete construction is evidenced by the rapidly
increasing number of specifications calling for the
admixture of hydrated lime in all classes of concrete
work, and also by the recent railing of the Board
of Standards and Appeals of New York City, noted
in the American Contractor of May 8, 1920.
Advantages.
Briefly summarizing the advantages to be derived
from the admixture of hydrated lime in concrete the
following may be cited:
Hydrated Lime:
(1) Makes concrete much more plastic and work-
able, thus facilitating chuting and placing.
(2) Reduces the amount of water necessary in
mixing concrete, thus obviating the danger of
drowirng cement, particles, and also overcoming the
difficulties and known detrimental effects of evces-
sive free water.
(3) Causes concrete to lie closer to the forms
and reinforcement, thus giving more uniform and
smoother faces, eliminating segregation and stone
pockets, and reducing finishing costs.
(4) Produces denser and more homogeneous con-
crete.
(5) Acts as a preservative to the reinforcement.
(6) Prevents separat'd! and settlement in carts
and buggies.
(7) Imports more uniform apparance as to sor-
face and color.
(8) Is the most efficient integral watertightening
medium as officially declared
by the 11. S. Bureau of
Standards, and is also the cheapest material avail-
able.
That hydrated lime imparts the above mention-
ed properties to concrete has been observed and
testified to by many
of the leading professional and
practical men of the country, as well as by practical-
ly all of the departments of the IT. S. Government
dealing with construction matters.
Highway Construction.
In view of the rapid development of automobiles
and the breakdown of our rail transportation sys-
tem, good roads are today imperative, or the large
majority of communities a concrete road provides
the most durable and satisfactory type of construc-
tion.
A number of state h’ghwav departments, county
engineers, and municipal authorities have invesei-
gated the advantages to be derived from proper ad-
mixtures of hydrated lime in concrete used for
high-
way and pavement construction, with the result that
many
of them have now standardized such admix-
tures in their specifications.
After careful study and investigation, the affice
of Public Roads, U. S. Department of Agriculture
has approved specifications calling for hydrated lime
admixtures on projects to which government aid is
extended.
Careful and systematic studies conducted by
the Delaware State Highway Department ndicate
that the following advantages are derived from the
proper admixeure of hydrated lime in highway con-
struction.
(1) The compressive strength of the concrete is
increased.
(2) The concrete is placed and finished with less
Work.
(3) The concrete is made more impervious to
moisture, thus protecting the subgrade and reduc-
ing* the internal stresses caused
by alternate
absorp-
tion and evaporation of moisture.
(4) The war seems to be more uniform and de-
creased as compared with plain concrete.
(5) Economy is effected in that 1-2-4 concrete
with hydrated lime admixtures has proved more sat-
isfactory than l-li/2
-3 concrete without hydrated
lime.
(6) Observations indicate that cracks are less
frequent in concrete with
hydrate lime admixtures
than in the plain concrete.
(7) The free water content is reduced and the
surface runs of from the finished surface.
Concrete Products.
One of the rapidly growing uses for concrete is
the
production of concrete products, such as blocks,
bricks, p’pe, battery boxes, etc. In order to facili-
tate the manufacture and to prevent excessive mold
equipment being tied up, such products are general-
ly made of very dry mixtures. Such dry mixtures
are difficult to work, owing to the fact that there
is not
enough water present to provide lubrication
or plasticity. Complete filling of the molds is also
difficult w th the
dry mixtures and requires an ex-
cessive amount of work. The loss due to imperfect
mold filling* and breakage of green specimens on
acount of lack of cohesion, is large.
The admixture of hydrated lime to the mixes
tised for the
manufacture of cancrete products has
in several instances, turned a losing venture into
a paying business. Lime reduced to a paste or putty