ASPHALT ANSWERS
This “ Corn Row ” method of tack coating will result in failures down the road
Tack Coats :
While a trailer mounted unit is perfect for some jobs , larger sites might require a computer controlled asphalt distributor .
Yes , No or Maybe .
BRIAN HALL
Since the main thrust of our articles have been heavily focused on “ Best Practices ” ( Whatever that is ), I thought we would spend some time discussing one of the items that gets more overlooked , but gets most of the blame for failure . Emulsions , or tack as we like to call it , is the bond that adheres the old asphalt to the new . How much , or how little to use seems to be a topic of debate on the job site . While many requirements call for a bonding coat , rarely do we see anything more specific than that , especially on commercial jobs . Today ’ s asphalt jobs are created in layers ,
much like a strong sheet of plywood . Like plywood , asphalt is built up in layers to create a strong final product and need a layer of “ glue ” between each layer to ensure its strength and durability . Let ’ s start with the makeup of tack . In simple terms , you are looking at two insoluble components , oil and water . The water surrounds the oil and allows the expensive asphalt to sprayed thinner and at a lower temperature than hotter liquid asphalts . As the paving process ensues , the water in the mixture evaporates , leaving only the sticky asphalt that will bond the two surfaces together . You may be familiar with the term “ break ”. Breaking refers to the point where water is evaporating from the mixture . I have heard some experts contend that you need to wait until the emulsion breaks to pave , but I disagree . Take for example the paving machines that spray tack one foot in front of the screed . Now , what kind of equipment do we need ? I have seen everything from pine tops to watering cans to disperse emulsion . Not only is this bad practice , but it is quite unsafe . Either a tack distributor or a truck mounted asphalt distributor will work perfectly . The truck mounted www . callape . com [ 32 ] 1.800.210.5923