:272 KANSAS CITY REVIEW OF SCIENCE. 
ASPHALTUM PAVEMENTS. 
As 'the work of reconstructing Pine Street, St. Louis, with asphaltum has 
commenced, a description of the new pavement may not be without interest. The 
contract under which the work is being done, after providing for a foundation 
of cement, mortar and concrete, provides that the pavement shall be completed 
as follows : 
Upon the concrete foundation thus prepared shall be laid the wearing sur- 
face or pavement proper, the basis of which or paving cement must be pure 
Trinidad asphaltum unmixed with any of the products of coal tar. The wearing 
surface shall be composed of: i. Refined Trinidad asphaltum. 2. Heavy 
petroleum oil. 3. Fine sand, containing not more than i per centum of hydro- 
silicate of alumina. 4. Fine powder of carbonate of lime. 
The Trinidad asphaltum (so-called), whether crude or refined, as found in 
this market, contains from 20 to 35 per cent of impurities, and is especially 
refined and brought to an uniform standard of purity and gravity. 
The heavy petroleum oil, which may be the residuum by distillation of the 
petroleum oils as found in the market, generally contains water, light oils, coke 
and a gummy substance soluble in water. This petroleum oil is freed from all 
impurities and brought to a specific gravity of from 18° to 22° Beaume, and a 
fire test of 250° F. 
By melting and mixing these two hydrocarbons, petroleum oil and asphal- 
tum, the matrix of the pavement, called asphaltic cement, is manufactured, which 
cement has a fire test of 250° F., and at a temperature of 60° F. has a specific 
gravity of 1. 19. 
They are mixed in the following proportions- by weight: Pure asphalt, 100 
,parts; heavy petroleum oil, 15 to 20 parts. 
The asphaltic cement being made in the manner above described, the pave- 
.ment-mixture is formed of the following materials, and in proportion stated : 
Asphaltic cement, from 12 to 15; sand, from 83 to 80; pulverized carbonate of 
lime, from 5 to 15. 
In order to make the pavement homogeneous, the proportion of asphaltic 
•cement must be varied according to the quality and character of the sand. The 
sand and asphaltic cement are heated separately to about 300° F. The pulver- 
ized carbonate of lime, while cold, is mixed with the hot sand in the required pro- 
portions, and is then mixed with the asphaltic cement at the required tempera- 
ture and in the proper proportion, in a suitable apparatus, which will effect a 
perfect mixture. 
The pavement-mixture, prepared in the manner thus indicated, shall be laid 
on the foundation in two coats. The first coat, called cushion-coat, shall contain 
from 2 to 4 per cent more asphaltic cement than given above ; it shall be laid to 
:&uch depth as will give a thickness of half an inch after being consolidated by a roller. 
