[KTL]

The reason wire and fiber mesh is used for flatwork is ease of use in PLACING (pour, place, dump, who cares? enough with the semantics already guys!) the concrete. When you get crazy with too many bars, it's hard to place a nice dense monolithic slab with all those bars, ties and stirrups in the way. Then you end up using a vibratory unit to shake down the mix. Too much vibration? Brings all the moisture to the surface and sends most of the aggregate to the bottom. You then end up with a non-uniform concrete mixture.

Don't forget to tell our friends where to place the bars. The bars should be in the lower section of the slab (beneath the centerline of the cross-section). Why? Because this is where the slab is in tension when loaded. Concrete's strength is in compression. Not tension. Hence the use of the bars. Compression strength is determined by the combined work of all the components of the slab. Certainly bad aggregate is going to hurt your strength.

Sure concrete cures under water. Not a recommended method. Water-cement ratio is a very important parts of the concrete recipe. Too much water spoils the stew. Just try to keep it moist. Here is where a semi-wet mixture is good. And, as was said before, a stiff mix is a PITA to place and finish anyway...... Let's be reasonable here. This is a garage floor for a home. Not industrial use. I'm all for overkill but you gotta make concessions sometimes.

For flatwork, more often than not, the 2 in. base cushion (the subbase is the material beneath the base- usually clay around here) is for levelling purposes. Leveling gets you that uniform, monolithic slab I mentioned before. 2 in. of crushed stone gets you little strength. Sand even less so.