Pour limeade concentrate, tequila, triple sec and soda into large plastic container and stir to mix. Fill blender with 5 cups crushed ice. Add limeade mixture to ice in blender and blend until slushy.
Squeeze half a lime into a small bowl with a flat bottom. Dip each glass into the lime juice and then into the margarita salt.
Pour drink into salt-rimmed Margarita glasses. Garnish with lime slices.