Concrete is porous so you need to erect a concrete slab where drainage is not an issue. Subsurface water can cause the ground the flex, creating stress cracks in the cement. Properly preparing the subsurface helps to limit the potential for cracks in the finished concrete slab. Preparation is the most important aspect of pouring a concrete slab.
While blacktop is nearly identical to asphalt, it is made differently. The crushed stone and bitumen are a different ratio. You’ll notice that in a blacktop road, the surface sparkles more than a thick layer of asphalt. That’s because there is a higher percentage of natural stone crushed into the mix.