Evening star., 1926-04-29
CENTRAL CEMENT
PLANT IDEA GROWS
Shortage of Building Labor
Boon to Contractors in
Unexpected Way.
By j. G.. ROYLE.


Special Dispatch, TO The Star.
NEW YORK. April 29.-rhe ire.
mendous volume Of building now in
progress, which is far greater than at
this time last year, has forced the de.
velopment of new labor and cost sav.
ing devices hitherto unknown in the
building trades
The shortage Of laborers in some sec.
tions. as we'll as the high scale of
wages paid, is leading to the employ.
ment OF machinery to replace man.
power.
The latest development OF this char
acter Is the establishment Of central
concrete. mixing plants. Freshly made
concrete, ready for the forms. unhar.
dened and plastic, may now be ordered
over the telephone much the same
way as lumber, nails or other build
ing materials, and delivered as
promptly.
The business Of making and selling
concrete is a new development. but
already 1t is in successful operation in
80 cities. Construction men say It Is
too early to determine what IL eventu.
ally may mean to the building world.
but indications are that better build
ings will result from more careful
measuring and mixing methods in
use at the commercial plants.
Poor Quality Concrete.
A low quality of concrete sometimes
results from carelessnesS or lack OF
knowledge in mixing. For example.
the addition of a pint too much OF
water is held by experts to be equiva-
lent to taking two or three pounds
Of cement from each sack. Sometimes
too much mixing water Is used be.
cause wet" concrete is easier to
place in forms than dry" or stin
concrete.
Concrete from the central mixing
plants frequently is hauled IA to Is
miles before II Is placed. The mixture
must be stiff to haul it without injury
and il Is believed this tendency to-
ward the dry" mixtures will tend to
create a higher quality Of construc-
ton. The effect OF too much water
was strongly shown in connection
with a Job in one OF the Southern
cities.
In an effort to make the stin con.
crete from central mixing plant
easier to handle. the contractors
added water just before the mixture
was placed. A committee OF engi-
neers found that after four weeks the
concrete to which water had been
pounds to the square inch. while the
concrete used as delivered withstood
a pressure of $500 pounds.
Cuts Contractors Expenses.
Engineers say that the use of the
central mixing plant will obviate the
expense and delay of moving portable
mixers from Job to job and relieve the
contractor Of cost Of maintaining mix
ing machinery at all. Accurate de-
vices for measuring sand. cement,
stone and water are not usually avail.
able on small portable plants. The
central plants are utilizing inundators
which measure the required amount Of
mixing water after taking into consid-
Grafton the moisture in the sand.
Through such equipment the central
plant is able to turn out a uniform
product Of any desired quality day
after day.
The use Of the central mixing plant.
engineers say, is economical up to the
point where trucking costs reach a
high figure. The territory which can
be servel from each central plant is
it is available, but for some highway
projects the trucking costs make its
cost prohibitive.
None Of the plants now in operation
are operated by cement companies.
Some are owned by contractors who
mix their own concrete. as well as sell
1t to outsiders. and some are operated
by building supply dealers.
The cement plants Of the country
are maintaining tremendous output
and stocks are fairly heavy, but the
prospect that the first half OF 1926 will
exceed any other similar period In his
tory in the volume Of building and
road construction has kept prices
stable. The same is true of crushed
stone, Stag. gravel and sand. The
steel mills are feeling the demand for
reinforcing steel. as well as for struc-
tural shapes.