by Tony Ng

Phosphoric acid can be used instead of hydrochloric acid to prepare microsurfacing emulsions. The resulting slurries cure by a different mechanism than the conventional ones, which allows the emulsions to be prepared with a wider range of asphalt sources. The pH changes in the phosphoric acid slurry system are much less pronounced than that of the conventional hydrochloric acid system. The paper describes how the phosphoric acid activates the cement mineral filler used in the slurry recipe, and this activated cement adsorbs emulsifier leading to setting of the slurry surfacing.

The paper was presented at the 18th CILA meeting (Congreso Ibero-Latinoamericano del Asfalto) held in Costa Rica December 2005 and appears in the proceedings of the conference, and also (in modified form) at the ISSA (International Slurry Surfacing Association) meeting held earlier in 2005.

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