Qqueen:

You want the wood to be pressure treated to avoid the problem of wood rot occuring in your patio.

However, pressure treatment only addresses the issue of wood rot; it doesn't address the issue of the wood splitting at the end grain due it absorbing rain water there. If you ever look at wood that's been left unprotected outside, the end grain of the wood will be split and the wood will be grey in colour. The grey discolouration comes from UV damage to the wood from the Sun, and the splitting of the end grain is due to the absorbtion and evaporation of liquid water at the end grain of wood. Water is absorbed into the end grain of wood 15 times faster than it is into wood across it's grain, which is one of the reason why wood rot almost always starts at the end grain of wood.

If the end grain of the wood you're using to build your patio isn't treated somehow to prevent water absorbtion, one of the most effective ways to treat it is with a liquid epoxy meant for use on rotted wood. Basically, you paint the end grain of the wood with epoxy to prevent it from absorbing rain water, Then, the only way your wood could absorb water is across it's grain, and it's unlikely that will ever result in the wood ever splitting because absorbtion of water across the grain of wood is very much slower than at the end grain.

So, if your wood is pressure treated, and even if it's not, then my suggestion is to buy some two part liquid epoxy for strengthening rotted wood, and paint that on every end grain of every wooden patio paver to prevent the absorbtion of rain water and snow melt at the end grain of your wood.