Fire Box Floor , Wood Burning Fireplace 1913 Home

Hello All , hoping for some help here , I have been trying to get a straight answer for a couple of weeks now and finally stumbled on your site . I tried searching for something specific to my question , but could not locate it , so here it goes ...

I bought some Rutland products to patch up a few broken bricks in my fire box and then noticed (after cleaning the floor) that it was very severely damaged , with cracks radiating out all over the place .

I very easily removed the cement like material (its about an inch thick or so ) and exposed what I imagine to be the fire brick of the day in 1913 . Its an orange color substrate with some need small sized orange rocks in it , and looks very intact so I dont wish to mess with it of course ... There is no ash clean out on this fireplace of course ...

So , now I need to fill in that removed concrete layer with a suitable material ... can you recommend anything ?

All inputs would be appreciated ...

Thanks so much

Tom

Thanks

Do you think I should post this question somewhere else , maybe I am in a bad spot and folks are not seeing it well ?

Thank you for your comments ..

Tom