What Loctite product did you buy... They probably make over 100 different adhesives... I use Loctite to secure fastners, sure wouldn't use the same product to hold down a sink....  Sink should mechanically fasten from underneath shouldn't it? Use the Loctite caulk to seal the sink to prevent water from leaching underneath...  http://www.loctiteproducts.com/p/pss_seal_tt/overview/Loctite-Polyseamseal-Tub-&-Tile.htm

Many sinks have the mechanical fasteners Retento spoke about. In those installations, most of the time a continuous ring of sealant is placed on the underside flange of the sink and it is pushed into place. Then the fasteners are tightened to securely hold things down. The extra sealant squeezes out and is cleaned up with paint thinner.

The most commonly used sealant is a clear silicone or bath tub caulking. I would not use a product that is a contact adhesive. Usually when the sink is installed, it has to be slightly moved about to position it into place. Not being able to, might result in an improper placement. There are many brands of polyurethane construction adhesives that could be used if there are no fasteners. They tack up in ten or fifteen minutes, allowing the sink to be moved shortly after it is located. Once it is in place, a large container full of water will hold things down until the adhesive sets. A full paint can also work pretty well.