St. Paul daily globe. [volume] (Saint Paul, Minn.) 1884-1896, 1895-06-09
TRINIDAD AND BERMUDEA
HOW THE PITCH ASPHALT II
OBTAINED AND PREPARED
FOR USE.
BAD WORK GUARDED AGAINsT
st. Paul Better Protected ThaH
Any Other City in the
United Statea


the city engineers department yester-
day in search of information about
the asphalt being used so generally
for paving purposes in st. Paul, and
the method of preparing and putting
it down. AS many criticisms have
been made upon the work of the con-
tractors, and the general public is
probably unfamiliar with the details
of pavement making, a complete ac-
count of the business, and of the pre-
cautions against inferior material and
work, was desired to lay before the
readers of the G ODE. In response
to inquiries, City Engineer Rundlett
gave the following interesting info:ma-
ton concerning the asphalt pavement
from start to finish:
The asphalt now being used in the
construction of the Seventh street
pavement comes from what is known
as the pitch Lake In the island of
Trinidad. The Pitch Lake, so-called,
covers an area of about $50 acres at an
elevation Of 100 feet above the level
of the sea. 1t is not, as may be, per-
with the exception of a small area in
the center it is firm enough to be trav-
eled upon with teams and is covered
with vegetation.
The asphalt is taken out in a man
ner somewhat similar to the taking
of peat from peat bog, and the holes
made by excavation gradually fill up
q iG1 ic hxy hn
British government, and the product
of the pitch lake is controlled by a
company which has a concession from
the British government, for whicl a
royalty is paid. Every cargo of Pitch
Lake asphalt shipped to this country
for paving purposes has certificate
from the American consul at Trinidad
stating the fact that such vessel was
loaded with the product and cleared
from that port. This asphalt is afSer-
wards unloaded and refined at vari-
Gus places in the United States
The asphalt used on Seventh street
was refined by the Warren Chemical
company, of New York, and every
shipment made to the contractors at
st. Paul is accompanied by a certifi-
cate that it is Trinidad asphalt and
designates the cargo from which the
asphalt was refined.
The process of manufacturing the
product used for the street covering
can be briefly described as follows:
The refined asphalt, as received from
the mandatory, is first put into large
tanks and melted. The plant of Hen
messy & Cox, which is one of the best
of it's kind in the country, and is
equipped with all the modern appli-
ances, has two large tanks, each hold
ing about sixty barrels, where the ma
terial Is melted, the process of melt
ing going on in one tank while 1t Ia
being drawn off in the other. After the
asphaltum is melted and brought to the
proper temperature the residuum oil
Is added, and is thoroughly mixed
with the asphaltum by agitating the
whole mass by means of compressed
air. The mixture is then drawn off
into large tanks, where Ii Is brought
to a temperature of about 800 degrees
Fahrenheit, and kept constantly i'm mo-
tion by mechanical agitation, and from
these tanks 1t is forced by compressed
air into buckets, where 1t is carefully
measured and weighed before going
into the mixer. The sand used is care
fully selected, screened, and heated to
proper temperature by passing through
a revolving drum, and from this drum
1t is carried by elevators into a bin
where it is stored until needed for the
mixer. In preparing the mixture for
the work on the street the exact
amount of Sand hU Wafoht ie fret oil
lowed to run into the mixer: to this
is added the exact amount by weight
of the asphaltic preparation before de-
scribed. The carbonate of lime, ac-
curately measured is then added, and
the mixer set in motion until, in the
estimation of the expert in charge, the
whole product is thoroughly mixed.
when it is dumped into the cart beneath
and taken to the work Under all thd
Specifications for asphalt paving the
exact proportion of the different parts
of the mixture is left to the contractor,
and it is at this point that the knowI-
edge of the expert comes in. The char
acter and quality of the sand and tha
climatic conditions of the place whera
the paving is to be laid govern him
largely in deciding the proper proper
are determined on the whole mixture
is made exactly alike as far as 1t ia
possible to do so; and, If for any ac-
count the wearing mixture proves bet
ter on one part of the street than on
another, it is due to other causes than
a difference in the proportions of the
materials used. While the exact pro-
portions of the mixture is considered
one of the secrets of the trade, it is in
all cases known to the engineering de-
partment.
The manufactured material is taken
onto the street in carts at tempera-
ture of 300 degrees Fahrenheit. 1t IS
there carefully manipulated with rakes
tampers and smoothers by skilled work
men, and rolled until the roller ceases
to make an impression on the finished
surface, a cement dust being pre-
viously swept over it to give a coloring
to the surface, and to prevent the as
phalt from adhering to the roller. and
after being allowed to harden for about
twenty-four hours the street is opened
for traffic.
In preparing and laying the asphalt
surface on Seventh street. the fol-
lowing experts are employed:
w. w. Robinson, in charge Of the
mixture at the works: John De Mars,
in charge of placing the surface on the
street, and John Merter. in charge Of
the roller, with eight rakers and tamp-
ers and smoothers, all of whom have
had large experience in this class OF
work and are skilled workmen, brought
here from Washington or Detroit. All
other labor is employed in st. Paul. and
all material with the exception of the