Crumbly mud pan - help me mongo-wan-kenobi
I promise I used the search function both here and on the JB forums and must have read through 150 posts about "crumbly" mud pans. What I am confused about is that sometimes the advice was "rip it out" and sometimes the advice was "its fine, maybe put a little thinset on it if you are worried". I guess my inexperience doesn't allow me to understand the difference and/or which advice is appropriate for my particular circumstances.
I read the "how to" in the JB liberry on how to mix deck mud. I mixed it using portland cement from home Depot and "all purpose sand" (also from home depot) With a 5:1 ratio. I mixed the dry ingredients, then added water in small doses until the mix was just as described. It clumped, held its shape and left my hand relatively clean. It went in well, packed great and when I finished I was ecstatic and patting myself on the back. I counted the seconds until it had been 24 hours and found that it was very crumbly.
To be more specific, it has the following characteristics:
It's been curing for 26 hours
I can walk on it, even jump on it and it feels very solid, there is no "give" to it
brushing your finger across it yields "crumbles" down to about 1/4" at which point it starts to hurt your finger to scrape at it
using a sharp blade such as the edge of a trowel I can scrape down seemingly to the bottom (i only went down about an inch or so)
It is less crumbly in the further parts of the pan where I started and more crumbly at the curb edge where I ended up (It took me about 3 hours to lay because I have OCD about things like this)
Obviously I don't want to redo all that back breaking work (I don't see how you mud men do this stuff every day!) but I want it to be right. Do I need to pull it out and start over? Or is this one of the instances where its OK to tile over it? Its a kerdi drain/kerdi membrane shower pan if that impacts the course of action.
Thanks in advance for any advice.
ABOVE - pan immediately after finishing
ABOVE - pan after curing for 26 hours
ABOVE - "crumbling" with my finger
ABOVE - "crumbling" with my finger closest to the exit