Simply placing poles in concrete can create a condition that accelerates rotting at the bottom of the poles. To prevent this, there are three ways to solve the problem. Firstly, concrete should be poured around the pole, with no concrete under the pole. The concrete on top should be tilted from the pole to ground level to prevent water from accumulating around the base.
Secondly, fill the entire hole with cement to the top and dome the top of the concrete so that it tilts away from the pole to divert water from the pole. Finally, use a coarse gravel base of at least several inches on the bottom of the pit or formed area before pouring or placing any concrete or wood in its place. Pressure treatment of wood is a sure way to improve its longevity and prevent it from rotting. The most common fault with concrete poles is neck rot, where the pole rots right at the point where it comes out of concrete at the ground line. This can be easily avoided if the concrete is slightly above ground level and is domed or tapered away from the pole so that water does not fall into the wood.
Drainage is key; keep standing water away from the poles and they will last much longer. A pressure-treated pole will last about 10 years if kept dry. If you use metposts, they will only make it easier to replace & in my opinion, they look awful. However, when placed vertically on a drainless concrete base, pressure-treated wood can last only a few years. I had heard that plastic wrap would prevent lime from concrete from eating into the wood over time. Concrete tends to absorb moisture and wood expands when it gets wet, so these two factors combined will cause wood to break concrete. Finally, step every 15 cm and you will get it as solid as concrete and this would keep your poles as dry as possible.
Submit your peer-reviewed studies to demonstrate that concrete in contact with wood treated with proper pressure preservative causes premature wood decay.
