IIRC--the petrobond was made by mixing sand with a cut-back asphalt, then allowed to cure-(evaporate the solvent) then ready for use--- today they would probably use a waterbased emulsion (solvent much cheaper)
back when I wuz building county roads, there was a large area in the county that had just the "right" sand for asphalt stabilizing. We'd cut the sand up about 6" deep, windrow it on one side, drive a 5000gal tanker down the road with a 3" valve open, dumping out a cut back asphalt-about 60/40% with grader following and covering the "oil" withabout 2 " of sand---usually took 5 or 6 truckloads of asphalt per mile--Then it was bladed back & forth across the road until it was well mixed and the solvent had evaporated...you could test it by grabbing a handful , squeezing real hard , seeing how well it held its shape. You could toss it into the windrow without it breaking.--Then if you dusted off your hands & nothing stuck to them, it was ready to compact---made an excellent base, which was then oiled & chipped a couple of times.
The reason for the Asphalt was that when dried back out--it was quite rigid, .---some cheeapskates would sell a rural farmer a product called tank bottoms- which was a parrafin like substance with some petroleum left in it...this contimued to stay soft & lubricate the sand particles so that they would never stiffen up--Same thing with used motor oil--it's a lubricant, not a cement.
"course this was back when oil was $3 to $4 a BARREL---10¢ a gallon.