We are often asked about the engineering ratings for the SP14 asphalt anchors. The users needs to know how much pull and how much sideways force can the installed anchors withstand.
We have collected data based on a limited number of load tests. Tests on a 30 year old 3" asphalt with compacted fine gravel underneath have yielded pull forces in excess of 700 lbs when using expanding cement as the grout/adhesive. When using a cartridge adhesive used for cementing stones, the pull force was limited to about 250 lbs.
When trying to specify the minimum forces, our concern is the variability in the asphalt surfaces and their foundation. Asphalt contractors vary in the methods they use, as well as in the quality of the asphalt installation that is contracted for. A typical installation starts with a level ground, then a layer of aggregate 3 - 8 inches is applied. Some contractors compact the aggregate, some do not. The size of the aggregate's gravel can vary dramatically. Likewise, the type of asphalt used, its depth and its age, as well as how well it was compressed are all variables that have a significant impact on the strength of the bond between the grout and the roadway.
There is one parameter that can be specified, and that is the breaking point of the bolts that is used to attach the devices to the anchors. We use M8 or 3/8" steel bolts. These are rated to withhold safely 1000 lbs (450 Kg) in a pull direction. They will withstand a higher force in the shear direction. Note that none of the industry standards specifies a shear force rating for bolts. However, the failure mode maybe the softwness fo the surface which will allow the ancor to cut sideways through it.
