Concrete help - to grind or not to grind, that is the question

[OneWithWood]

When we poured the last sections of the slab for the barn last January we sort of hurried the finishing due to lack of daylight and the cold.  The board I used for a screed was not exactly straight so there is a crown of between an inch and an inch and a half on the sections on either side of the kiln chamber.  The kiln doors will not swing open with the crowns.  I also need to cut channels into the slab for the rails the wood carts will ride on.
I need some advice on the best way to fix the problem.  I could just cut the channels in the slab as it exists and build 2x4 thresholds at the entrance and exit thus lifting the doors enough to gain the necessary clearance.  Or, I could rent a machine and grind the slabs level.  The area of each section that would need to be ground down is 325 sq ft.
I have no experience grinding concrete so I thought I would ask those of you that have some experience for your thoughts.
What would you do?

[WH_Conley]

Seeing it done was enough for me. I would hire it done or go the threshold route.

[Dan_Shade]

i used a hand grinder with a masonry wheel in it once, it cut way faster than I had figured...

with the concrete still being new, it might not be so stupid hard as some of the 50 year old stuff around.  How much is it to rent the grinder thingy? 

if it's not too expensive, just give it a try.  don't forget to wear a dust mask, that dust is nasty.

[pasbuild]

Why don't you just reform the kiln including the channels for the kiln carts and pour a cap over the existing? A 3" thick cap using a 6 bag mix with small aggregate will hold up well.

[isawlogs]

Why don't you just reform the kiln including the channels for the kiln carts and pour a cap over the existing? A 3" thick cap using a 6 bag mix with small aggregate will hold up well.

  Thats what I would do also .. if the head room will alow it . Reform and repour .

[UNCLEBUCK]

I asked my dad the old retired cement guy and tried to explain the question as best I could and I asked what he would do ? He said rubber sweeps on the door bottoms or else to pour over the old slab and use a 50/50 sand and cement slurry mix broomed on the old slab just before the new pour to get it to stick or even just wet down the old slab just before the new pour . Grinding he did not like at all. Use quick bolts to tie down your new rails and then use them for the screed pipes and go ahead and pour .  He said all this to me in 30 seconds and then dissappeared  :D. He likes it when I ask him questions but doesnt show it . :D