The Hoover dam required more than 3 million cubic yards of concrete. Because of the setting time for concrete and the amount of heat it generates during the setting process, the dam was poured in sections approximately 50 by 50 feet on a side and 5 feet deep. Workers embedded cooling pipes in the concrete as they poured it, and cold water ran through these pipes to help remove the heat during setting. A 5-foot-deep block would set for 36 to 72 hours before another block was poured on top of it. Using this technique, they poured the entire Hoover dam in less than two years.
This same technique would work great for recreating the Great Pyramid. The Great Pyramid is even a little smaller than the Hoover Dam -- only about 2.5 million cubic yards of concrete is needed. But this is still going to be an expensive project. If you're buying it by the truckload, concrete costs about $80 per square yard. For a big job like this, you would build your own concrete plant. Let's say that by doing so you get the cost down to $50 per square yard. That means concrete alone will cost $125 million. By the time you add in labor, design costs, form work and so on, you probably end up doubling that. So your new Great Pyramid might cost something on the order of $250 million to $300 million.