Asphalt

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Summary

Asphalt, or bitumen, is a viscous constituent of petroleum, about 80 percent carbon, used as a binder and waterproofing. 🟠About 10 percent of use is roofing (shingles, built-up and modified bitumen roofing), where its temperature sensitivity and aging drive detailing and replacement.

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[!abstract] Contents

Terminology

Bitumen: the petroleum binder; called asphalt or asphalt cement in American English
Asphalt concrete: bitumen mixed with aggregate, about 5 percent bitumen and 95 percent aggregate by weight
Asphaltenes / maltenes: the dispersed and continuous phases of bitumen
RAP / RAS: reclaimed asphalt pavement / reclaimed asphalt shingles
BUR: built-up roofing
Pitch: the class of material bitumen belongs to

History and demand

Discovery and early use

Middle Paleolithic: adhesive on stone tools, one find about 71,000 years old
Ancient Mesopotamians used bitumen for mortar and waterproofing; Egyptians used it in embalming

Use in construction

1830s: first European patents for asphalt paving; 1870s: asphalt reached United States streets

Demand trend

About 102 million tonnes used per year: roughly 85 percent road binder, 10 percent roofing, 5 percent other sealing and insulating; about 164 million tons produced in 2019

Composition and production

Raw materials

About 80 percent carbon, 10 percent hydrogen, up to 6 percent sulfur by weight
5 to 25 percent asphaltenes dispersed in 90 to 65 percent maltenes; classes: naphthene aromatics, polar aromatics, saturates, asphaltenes

Manufacturing process

Material with a boiling point above roughly 500°C is classed as asphalt; stored and transported at about 150°C (300°F)

Properties

Durability

Aged bitumen stiffens over time; recycled material is blended with virgin asphalt or rejuvenating additives

Standards

Material specifications

ASTM D3462: asphalt shingles
ASTM D312, D6083, D1863, D4990: built-up roofing materials
ASTM D6162, D6163, D6164, D6222, D6223, D6298, D6509: modified bitumen sheets

Uses in buildings

Building elements

Asphalt Shingle Roofing, Built-Up Roofing, Modified Bitumen Roofing: saturant, coating, and adhesive binder in shingles and membranes
Site Paving: binder in asphalt pavement, the largest use of bitumen

Pros and cons

Pros

Adhesive since the Paleolithic and waterproofing since ancient Mesopotamia
Recyclable: RAP contains 5 to 6 percent binder, RAS 20 to 40 percent

Cons

Handled hot (about 150°C)
Stiffens with age
Petroleum derived

Sustainability

Recycled content and end of life

RAP typically contains 5 to 6 percent binder; RAS 20 to 40 percent

Manufacturing and cost

Main manufacturers and suppliers

Trade associations: Asphalt Roofing Manufacturers Association; Asphalt Institute.

Sources

Wikipedia: Bitumen, https://en.wikipedia.org/wiki/Bitumen
UpCodes: 2024 IBC Chapter 15 roof assemblies, Chapter 15 Roof Assemblies and Rooftop Structures: Department of Defense Building Code 2024 | UpCodes