Note 21 — PART I SPECIFICATIONS FOR STREET ROADWAY PAVEMENTS

The practical value of the exact determination of the ductility of asphalt paving cements is regarded by the author as not well established. It is customary, however, in most recent specifications to require it. Some asphaltic cements that have been quite successfully used for pavements have not complied with such requirements, while good coal-tar pitches will greatly exceed them. Where this test is used the usual specification requires that a briquette of asphaltic cement having a cross-section of one square centimeter, at penetration 50, shall elongate to the extent of not less than 20 nor more than 85 centimeters at 77° F. If the asphaltic cement varies from 50 penetration an increase or decrease of at least 2 centimeters will be required for each five points above or below 50 penetration (Dow apparatus to be used).