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SBS Modified Bitumen Specifications |
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7A.7 Roofing Bitumens
7A.7.1 JM modified bitumen products are designed to be installed with hot asphalt or special cold application cements. PermaMop, coal tar
pitch and coal tar asphalt are not permitted.
7A.7.2 Asphalt can come from a variety of crude sources. Many of these sources produce high quality mopping grade asphalts and many do
not. Various physical properties of asphalts can affect the performance of the roofing system. For this reason, JM qualifies asphalt sources
throughout the country and requires that only these asphalts be used to assure good performance and compatibility with the roofing products
being used.
JM requires the use of Trumbull®* or another JM "approved" asphalt within systems which require a JM Roofing Systems Guarantee. These
"approved" asphalts are periodically tested to assure conformance to both ASTM and JM asphalt specifications. The JM Approved Roofing
Contractor must indicate at the time they place their orders that the asphalt required will be used within a JM roofing system. This will ensure
that the asphalt supplied is registered with the asphalt source. The asphalt supplier will provide a "JM" number to the asphalt purchaser which
the Contractor in turn provides to JM as a condition of issuance of the JM Guarantee. For the names of approved asphalt suppliers in your
area, contact a JM sales representative.
7A.8 Asphalt Health and Safety Information
See Section 1.9 for health and safety information.
7A.8.1 Roofing asphalts are available in four grades. In general, they are grade-specified by softening point. JM recommends the use of only
two grades in SBS modified bitumen specifications – Type III and Type IV. The slope of the roof, as well as the climate, governs the grade of
asphalt to be used. The success or failure of a roofing system depends greatly on the use of the proper grade of asphalt, as called for in the
roofing specification.
7A.8.2 Asphalts are susceptible to damage from overheating. Overheating, even for short periods, can "crack" or degrade the asphalt; a drop
in softening point or a slight oiliness is a symptom. Overheating may result in a "fallback" in softening point which can cause slippage of the
roof membrane. As the softening point decreases, the viscosity or "holding power" of the asphalt decreases. This can allow slippage to occur.
If the overheating is more gradual, the asphalt may "age", to the extent that premature failure of the system may result. Application
temperatures must be in the range which permit a continuous layer of asphalt, regardless of the application technique used.
7A.8.3 The JM Research group, in conjunction with the National Roofing Contractors Association and the Asphalt Roofing Manufacturers
Association, has been involved with considerable research into a system for classifying mopping grade asphalts. The system gives guidelines
for proper heating and application.
7A.8.4 With this system, which is used in the Continental United States, the following information is printed on the cartons of asphalt, or on the
bill of lading for asphalt shipments:
1. |
The Softening Point, as determined by ASTM D 312. |
2. |
The Minimum Flash Point (FP) of the asphalt, as determined by ASTM Method D 92. |
3. |
The Equiviscous Temperature (EVT), as currently defined by ASTM, is the temperature at which the asphalt viscosity is 125
centistokes. Asphalt applied within ±25°F (±14°C) of the EVT at the point of application will provide a nominal 23 - 25 pounds of
asphalt per 100 sq. ft. (1.12 - 1.22 kg/m2). |
4. |
The Finished Blowing Temperature (FBT) is occasionally provided. This is the temperature at which the blowing of the asphalt was
completed. |
Note: Work done by the NRCA has shown that different EVT values should be used for mop-applied vs. machine-applied asphalt. The original
EVT is applicable to mop applications. Asphalt installed by machine should be applied using an EVT based on 75 centipoise. Some asphalt
suppliers are now including both EVT values on their products. If only the 125 centipoise (centistokes) EVT value is provided, and a machine
installation is to be used, apply the asphalt at 25°F (14°C) higher temperature.
7A.8.5 JM requires adherence to the following guidelines when the above information is furnished:
1. |
Use the proper softening point asphalt as specified for the roof slope, type of roofing system and climate. |
2. |
For optimum application, the asphalt should be at the Equiviscous Temperature, ±25°F (±14°C), at the point of application.
However, SBS modified bitumen products shall be installed in asphalt with a minimum temperature of 400°F (204°C) or at the EVT,
whichever is higher. |
3. |
Never heat the asphalt to or above the Flash Point, to avoid danger of fire. |
4. |
Heating above the Finished Blowing Temperature shall be strictly regulated, never for longer than 4 hours to preclude excessive
asphalt degradation. |
7A.8.6 If the EVT is not available, heating temperature guidelines of the asphalt recommended for use with modified bitumen systems are as
follows:
Recommended Temperatures
Asphalt Type |
Heating |
Application |
190 Grade (Type III) |
500°F
(260°C) |
400°F to 475°F
(204°C to 246°C) |
220 Grade (Type IV) |
500°F
(260°C) |
400°F to 475°F
(204°C to 246°C) |
7A.8.7 Use of insulated buckets and insulated circulating lines for cold weather application is always desirable. However, if ambient
temperatures are low and the distance from asphalt source to the application point of the SBS membrane is great, their use is imperative.
