How tack coat is applied
First, the area to be patched must be thoroughly cleaned and all loose material removed. Then, tack coat emulsion is sprayed, or painted, over the entire area, including the vertical sides. 0.10.3 kg/m2 is a normal residual bitumen quantity. The bitumen content in emulsions varies depending on type of emulsion. So different applications rate for different types of emulsion. The same goes for cutback. There are many different types of cutback and hence the application rate varies for this also.
Emulsion has many advantages over cutback. First of all cutback is very dangerous because the low flash point and because of the high solvent contents in cut back it is harmful for the environment. When looking at quality emulsions have an advantage that you keep the bitumen properties. When using cut back the bitumen will become a lot softer and large amounts of the solvent will not disappear keeping the bitumen soft.
After spraying the tack coat, enough time must be allowed for complete breaking to occur before the overlay is placed. Traffic should be kept off the tacked area.
The emulsion types used for tack coats are CSSI, and CMS1h. The emulsion be diluted by adding water. To prevent premature breaking, the water is always added to the emulsion, not the emulsion to the water.