| You can buy liquid sealants that you add to the grout mix and i have sealed the final job with a product called Bondcryl 737, it is made by the same company that makes bondcrete. Bondcrete breaks down when it gets wet, bondcryl won't.
another product i'm trying out is panel patch which is lighter then morter and sets very hard, i have found a sponge pattted over the mud mix gives a better look than sand. | 
