Help fixing a fence

Factual Questions
1

The previous owner of my Seattle-area house built a fence between his property and the folks behind. Idiot that he was, he apparently dug a trench, filled it with cement, and sank untreated 4x4 uprights directly into it at ground level.

Fast-forward 25 or 30 years.

The wood of the 4x4s has rotted, not just at ground level but especially there. And during a recent windstorm a big branch fell off a tree and landed on part of the fence, snapping off two uprights at ground level. Right now, one 6’x8’ panel is lying flat in the neighbor’s yard, and two sag drunkenly, held up precariously by their sole remaining upright each (also rotten). The holes in the concrete are full of soggy pithy stuff, and I don’t know what else.

My current thought, since I don’t REALLY want to take a sledge hammer to the existing concrete and bash it to smithereens and dig a new hole for the new uprights (although that’s an option) is to clean the rotten wood out of the holes, buy some Quickcrete, dump it in the holes, stick one of these post support thingies in the hole, and wet the Quickcrete. Then put the new upright 4x4 in this, and try to salvage what I can of the existing fence panels? They’re old and falling apart (obviously) but it did take a 10’ long tree branch to knock this part down.

Is there a better, equally frugal solution? I do NOT want to replace the entire fence (which would be about 60’ long) at this time or any time soon.

2

Make that: these post support thingies

3

Hmmm. Adding new Quickrete to existing quick-set concrete is bad.

I rebuilt a fence that way a couple of years ago and while it worked fairly well, the old and new concrete never really bonded to each other. Once summer came around the different mixes expanded different amounts and the new concrete actually pressed into the old enough to make it crack. The old concrete is slowly turning to powder and the fence is getting rickety.

Of course, this is in Florida. I don’t think you have the same temperature extremes out in Seattle, so maybe you won’t have that problem, but I wouldn’t know.

I’d suggest that rather than destroying and removing the existing concrete base, you knock new holes into it and simply shift the fence sections down until you get to where they’re still sturdy. Either that, or use something other than more concrete when you reset the posts.