t are viscous liquids
at ordinary temperature. These materials are obtained from crude
petroleum or semi-solid native bitumens, in which case they are
usually called malthas. Both coal tars and water gas tars of
semi-solid consistency are also employed for the same class of
construction as the liquid asphalts.

These materials are used for carpeting mediums on macadam roads and as
cementing agents in the construction of hot-mixed macadam.

=Asphalt Cements.=--The solid asphaltic materials used for hot-mixed
types of construction are called asphalt cements. They may be
petroleum residues or native asphalts fluxed with petroleum oils. They
are solids at ordinary temperature and must be heated to a temperature
in excess of two hundred and fifty degrees before they are
sufficiently fluid to use. Asphalt cements are used for sheet asphalt
and asphaltic concrete construction and for hot-mixed bituminous
macadam.

=Fillers.=--Fillers are solid asphalts or tars that are used for
filling expansion joints in rigid pavements and for filling the spaces
between the blocks in brick, wood block and stone block pavements.

=Bitumen.=--Bituminous materials are all soluble to a greater or
lesser extent in carbon disulphide and the soluble portion is called
bitumen. It is the bitumen that gives to the materials the cementing
properties utilized in road construction. Mixtures of mineral
aggregates and bituminous materials for various purposes are
proportioned with bitumen as a basis. Therefore, less of an asphalt
containing one hundred per cent bitumen will be used than of one
containing less than one hundred per cent of bitumen.

TABLE 8

PROPERTIES OF ASPHALTIC ROAD MATERIALS

(A) Material
(B) Specific Gravity
(C) Consistency
(D) Solubility in CS_2, Per Cent
(E) Solubility of Bitumen in CCl_4, Per Cent
(F) Solubility of Bitumen in 86 deg. Naphtha, Per Cent
(G) Fixed Carbon, Per Cent
(H) Flash Point
(I) Ductility
-------------------------+---------+----------+----------+------------
(A) | (B) | (C) | (D) | (E)
-------------------------+---------+----------+----------+------------
Mexican oil asphalts |1.03-1.05|As desired| 99.5-99.9|99.5-99.9
California oil asphalts |1.02-1.04|As desired| 99.9 | 99.9
Texas oil asphalts |1.01-1.03|As desired| 99.9 | 99.9
Bermudez natural asphalt|1.07 | 25 | 95 | 99+
Trini