By Tony Wight
Tack tanks are typically the most overlooked machine on the paving fleet. While not every paving job requires using tack, best practices demand that tack be used when appropriate. For many commercial applications, a large distributor truck is not practical and a “pour bucket” is not effective. Oftentimes, their correct use is not fully understood as I quite often get asked what can I put in a tack tank.
Let’s first look at the different types of material used in our industry. They are tack (emulsion), AC (cutback), crack fillers (rubberized material) or sealcoat (driveway sealer). All of these products have a use but are used in different ways and applied with different techniques.
Tack or emulsion is nothing more than water and tar mixed together using a chemical called an emulsifier. (You thought water and oil never mixed, right?). Emulsion is used as a glue to help new asphalt adhere to old asphalt. Water is a way to thin the material and help it flow better. Most emulsions can be applied (mostly by spraying) at a temperature of 125 to 175 degrees. No mixing is required other than circulating through a pump from the bottom of the tank to the top. This helps to heat the material evenly and to help keep the water from separating from the oil. Once the emulsion is sprayed the water evaporates (The material breaks is the term you will hear on the job.) it leaves just the tar to bond the two layers of asphalt. A very important thing to remember is AC should never be used in a tack tank. Most of these units will not heat over 200 degrees. Please check with the equipment manufacturer to determine what can be used in there unit.
AC or cutback for the most part is used for the same thing, bonding layers of asphalt but diesel is used to thin the tar to make it flow. Most tanks that can apply AC heat to a very high temperature. Diesel burners are used as large as 500,000 BTU’s to heat AC. Most AC will flow at around 300 degrees. AC also only needs tank circulation to keep it heated and mixed. A tank that can spray AC most likely will also spray emulsion if it has temperature controls that allow it to.
Crack fillers or rubberized material is a highly specialized product used to fill cracks and seal joints. Most of this material comes in solid blocks and require heat around 400 degrees to allow it to flow. Equipment used for this type of material is also are very specialized. These units will have a double walled tank with heating oil in the middle. Once the material is hot enough to flow it is pumped through a wand and injected into the crack. You should never put Rubberized material through an AC or tack tank. Neither type of unit gets hot enough to allow material to flow.
The last of these products is driveway sealer. Driveway sealer does not require any heat but most products have sand added to them for antiskid proposes. This material requires regular agitation and the equipment normally has some kind of wiper paddles to help keep the sand suspended in the material. They normally have a diaphragm pump versus a rotary pump. A diaphragm pump is made to handle the abrasiveness of sand. Of course with no heat you would not put any of the above material through a sealcoat machine. Normally I get the question can I put sealcoat material through one of the above machines. The answer is I would not recommend it.
Bottom line if you have an existing piece of equipment and want to find a way to utilize it in other ways, it would be best to check with the manufacturer.
Tony Wight, LeeBoy Territory Manager and can be contacted at firstname.lastname@example.org