What performance differences exist between CSS-1 and CSS-1H asphalt emulsions?

CSS 1 and CSS 1H are both cationic slow setting, but the H grade typically has a harder base asphalt residue, which can improve high temperature performance and reduce tracking in some uses. The harder residue may reduce flexibility at low temperatures unless modified, so climate matters. Both are used for slurry seal, certain cold mixes, and applications needing longer work time. In practice, CSS 1H can offer better early strength after cure, while CSS 1 may remain slightly more forgiving in low temperature flexibility. Final selection should be based on spec compliance and field trials with your aggregate and filler system.