When you have a large number of slaves lots of things that would normally be impossible suddenly becomes easy.
http://en.wikipedia.org/wiki/Egyptian_pyramid_construction_t...
And from your wiki page: Most Egyptologists acknowledge that ramps are the most tenable of the methods to raise the blocks...
1. http://www.bbc.co.uk/history/ancient/egyptians/great_pyramid...
Egyptians also used the "build an earthen ramp to get the heavy stuff up, then clear the dirt away after you're done" strategy to build their ridiculously awesome temples. Any History Channel fan knows that.