35f is too cold for BT1109 - lowest acceptable is 40f. At 40f it will take quite a bit longer than usual, it could be 12 hours or more depending on humidity etc. Below 40f you risk compromising long term durability and even not fully curing. Wait for a warmer stretch of weather.
BTW this as good a thread as any to point out that a 100% solids epoxy does not "dry", it "cures" by exothermic reaction. In short there are chemicals in the 2 components that when combined generate heat. This heat in turns causes other components to change from their liquid state to a solid state, they get very hard.
The lower that self generated heat, the longer the transformation from fluid to solid will take.
If the slab underneath and surrounding air temperature are too low they will draw heat energy away from the coating, which may leave the coating with not enough heat energy to propel the fluid to solid cure process. The end result may then be a coating which will never fully harden.
If the weather is too cold one can heat the slab and air to acceptable levels (I'd shoot for at least 55f). If you do decide to heat the area do not use kerosene or diesel fueled heaters, they can produce gases which negatively effect the cure process. Use natural gas, propane, in ground, or electric heat sources only. And if you use space heaters avoid having the heat source too close to the coating, you don't want real high temp hot spots either.
