Hard asphalt in the previous formulation necessitates only slight changes in technique. With both grades of asphalt, the water temperatures should be 65-70'C before asphalt addition. With the harder asphalt, however, care must be taken to heat it to a fluid melt, but not overheat it or maximum hard asphalt temperature of 80'C is recommended. It is also very important to maintain the mix temperature at 70-75'C while adding the asphalt. If the temperature falls below 70'C, larger particles are formed and the emulsion is grainy. The 50-60 asphalt emulsion is also very stable to aging. It has a pH of 6.5 and a Brookfield, 20 rpm, viscosity of 5200.
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