Evening star., 1951-11-10
U. S. Engineers Develop
lightweight Concrete
Bubbles Of Air Take the Place
Of Sund in New Material
E By Thomas R. Henry

By Thomas R. Henry
A lightweight concrete in which bub-
bles of air take the place of sand has
been developed by engineers of the
United States Bureau of Standards.
Such air bubbles may constitute as
much as Is per cent of the new material.
1t was developed at the request of the
Agriculture Department for a suitable
building substance for farm structures.
The thousands of tiny air bubbles in
closed within the concrete not only re-
place the sand used in ordinary mix
lures but also make better insulator
against heat and cold and give more
resistance to water.
Concrete normally contains a coarse
aggregate such as gravel or crushed
stone held together by binder of NOR
tar consisting of sand, cement and water.
In the air-gravel concrete the sand is
replaced by air bubbles which act as a
lubricant This high air content ma
terlal is prepared in conventional mix
ing equipment in the normal way, ex-
cept that Soaplike substance is added
to cause it to foam by trapping finely
divided air cells. Trapped air may con-
stitute more than As per cent of the
volume of the mixture
Amoun. of Air Limited.
The actual amount of air that may
De incorporated practically, however, is
limited by an arbitrary strength re-
qulrement that the concrete withstand
pressure of 500 pounds per square
men. Under this requirement it was not
possible to go above 20 per cent.
The new, concrete was developed by
n. Z. Valore, jr, and w. c. Green of the
structural engineering laboratory. Ad-
mlttedly 1t does not have the strength
OF the old mixtures, but this is not re-
qulfed for farm buildings. It is con-
Sfoeraoly superior in the important
Qualify OF water absorption The mean
absorption on soaking for "a hours was 9
per cent, compared with il and IS per
cent for standard cements.
several types of the new concrete
nave been developed at the Bureau lab
oratorles. All are considered strictly
experimental at present because of the
striking loss OF strength. Efforts now
are being made to produce a mixture
which will combine much higher resist
ance OF compression without sacrificing
the advantages of the lightweight ma
terlal. 1t is hoped to accomplish this
by combining different ratios of air bub-
bles with the other materials.
Shifting regions of extremely hot
gases in the atmosphere of the sun
as we'll as the well-known "sunspots"
which actually are cool areas-haye
pronounced effects on such terrestrial
OlHn0mPnQ M cf4
radlo reception and northern lights
These now are being watched con-
stantly by observatories all over the
world in efforts to predict solar wealth
er" and. by this means, the earth's radio
weather"
This is particular job of the United
states Bureau of Standards. Sometimes
1t IS necessary to follow 10 or Is such
active regions which may exist on the
sun simultaneously. It is known that
there is a tendency for the most active
OF these regions to be associated with
radio disturbances, usually when the re-
gion is nearest the center of the suns
disk.
For accurate forecasts the sun must
be Kept under constant observation This
means that cloudy weather cannot be
allowed to interfere. All observations
must be made simultaneously. There
are relatively few solar observatories
Some are located on mountain peaks to
take advantage of the thinner atmos-
phere. Others are near universities with
special interest in solar physics, but
usually away from dust-filled city at
mospheres. This dispersal permits the
sun to be under continual observation,
for while clouds may obscure the disk
over one observatory the sky usually is
clear over another.
Measurements Reported.
SunSpot measurements. the easiest Of
all to make, now are being reported reg
ularly to the Bureau of Standards from
two obServatories in the United States
and two in Europe. Observations are re-
ported almost as soon as they are COM
pleted from the Naval Observatory at
Washington and the Mount Wilson OBJ
servatory in California. In Germany the
Wendelstein Observatory, located on a
peak south of Munich, makes sunspot
observations many hours before the sun
rises in the United States. The results
are transmitted to Washington imme-
diately. Similar observations are. re-
ported from the Meudon Observatory,
near Paris.
This would be fine if sunspots told
the whole story. Unfortunately, the
other necessary observations are harder
to make and require specialized equip
ment. One job is that of finding and de-
termining the brightness of concentrated
clouds of calcium gas in the suns atrnos-
phere. Most of this is done at the Nc
Math- -Hulburt Observatory near Pontiac,
Mich. The information is Immediately
telegraphed to Washington.