Winery trench drains

I’m installing a trench drain in the winery. It’s a no-slope drain, and I anticipate having to pour some fill into the drain channel at points to eliminate low spots and standing water. I’ve gotten a couple recommendations for using grout as the fill material, but I find it hard to believe their isn’t something better – smoother, better adherence to the plastic/nylon channel, better able to stand up to pressure washing. Anybody tackled this before?