Concrete topping specification for lightweight floor joists with plywood sheathing?

[Backcheckrage]

I am working on a multi-family building where we have cold formed joists at floors typical. We have 19mm plywood sheathed over to provide diaphragm action. We are going to pour a concrete topping over the plywood to achieve better STC and IIC values. Just one problem... NOBODY IN NEW ZEALAND HAS EVER DONE THIS (apparently). I have scoured the internet high and low (and these forums) and I cannot find a specific specification for this. Now, I know this is common practice in other countries like USA but surely there is a "drag and drop" specification for this type of topping?

In other words, surely there isn't large aggregate in it, so there is a max aggregate size. Also, to prevent the topping from curling up wouldn't there need to be some sort of fibre reinforcing to it, and if so, to what proportions?

Am I crazy here? I don't want to reinvent the wheel!

 

[Ron]

Most often here in the US, a gypsum concrete topping is used.

Gyp-Crete

Here is a link to one of the commonly used toppings