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hello fellas, just thought I might stick my nose out and see what happens.
1. I knew a rancher who fenced his own property and he used a combination of t-bars and railroad ties. the t-bars were standard but the railroad ties were spaced about 50 feet apart and set vertically in cement so as to “lend stabillity” to the fence. the key ingredient that he shared with me though is that he put a plastic garbage bag (shopped around for non-biodegradable) around the end set in concrete. (dirt/concrete/plastic/post like that)
2. if that is too much trouble then find a supplier for black locust fence post, they don’t seem to rot (I just renovated a 90yr old house with blacklocust foundation post under it), bugs dont eat it , and if you dont plant them upside down they have a tendency to take root (not joking) the only draw back is that blacklocust is fatally poisonous to horses.
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I decided to try a little experiment to see if it's possible to prevent cedar or pressure treated fence posts from eventually rotting in cement. I may have found a solution I just wish I would have come up with it 2 years ago. I painted 2 ft of a red cedar 4 x 4 with 4 coats of epoxy based paint and put in into a mud hole full of water. I left it in there for a year making sure it was always full of water. I pulled it out about a week ago (broke through ice and snow). I cleaned it off and the paint was barely affected. I chipped away the paint to see the condition of the wood underneath. It was bran spankin' new. I thought that maybe because the paint is like a hard plastic shell that it wouldn't let any water through. After one year sitting in water 24 hours a day, it didn't. I'm not saying it's a cure but it's ten times better than anything else I've seen. Preservatives like creosote don't last very long because water eventually soaks through. Not to mention they're just nasty chemicals to begin with. Just thought I'd share this with everyone. Does anyone have any comments or do you guys already know this?
Gaby
*Gaby,I humbly submit that that is a cockamamie idea.Concrete encasement of below grade lumber accelerates rot by holding in moisture. Epoxy paint will probably not prevent below grade wood in a non-arid enviroment from becoming humid enough to rot. I'm assuming you're not going to completely seal all six sides with epoxy and then paint above grade portions to protect them from UV radiation. That method might work if you had some special and obtuse application.Please allow me to temper this critique with praise for your enquiring mind and your experiment. Remember experiments need controls if the effect of something is to be established scientifically.All the cats here are fine. How are yours?joe d
*Gaby,Remember that epoxy is also a very nasty chemical, and expensive.Rick Tuk
*Gaby, yup, been thinking about it for years. I know I have dispensed this info a few times...but here it is again.I found that if you keep the cement in the bottom half of the hole only and back fill with gravel it allows the post to stay dry for much more of the time. It seems that the ground stays much more moist in the top 6 inches. Second part of the equation is that the top of the hole always falls in, making it larger than the bottom. Since frost settles in from ground level and heaves from there the heavy duty concrete footing upto ground level gets yanked out of the ground, and dirt fills in the bottom of the hole, getting a bit higher in elevation every year. I have many more ideas on this subject but for now I will stop here.LIf any editors are interested....I think I am ready to do an article on this subject [email protected]
*I have been reading a lot of posts all over the place about rotting pt posts at ground levelPersonally, I have never had this problem. Beats the heck out of me why I have never had this problem, and so many of you have.I recently dismantled an old shed I built 15 years ago, and I pulled up all 8 of the posts. I busted off the cement at the bottom, and I reused all of the posts on another project. All eight of the posts looked better at the bottom than the part that was above ground.I also have a basketball goal post (cedar) that was buried in the gorund for four years at my childhood home, then pulled and replanted at our new home (That was 26 years ago). The post is still in very good shape.I dig my hole, put in the post and brace and level, then I pour in fast setting cement and water. The hole is usually 8" to 12" in diameter, and about 18" deep. I make sure the concrete exptends above the ground level about 2", and taper it back (like a cone) to allow water runoff.Are you guys really having that much trouble with pt rotting at ground level, or is it basically isolated instances?Just a thought...James DuHamel
*James, if you haven't heard of it...or seen it...you would not believe it. You could plant your footing that way up here and in 5 years it would be laying horizontal. Frost would chew it up and spit it out. The other problem is the poor quality of lumber, (cores in posts), causing cracks for water to get into all 4 sides. If you aren't in a moist climate you would know nothing of it. Soil conditions, ground water and amound of rain all play a part in it. In some parts, posts set into the ground will remain wet 11 months of the year...If your post is only wet for a month in total the numbers make sense. (round here we get 3' of frost, and have to plant the posts 4' deep.
*Like James, I haven't experienced any rot myself. My fence has only been up for 2 years and the post are red cedar. I suppose I'll have to wait to see what happens down the road. Is the rot most likely to occur just above grade where the concrete ends or will the post rot inside the concrete? If the post rots just the above the concrete then I agree that painting the portion in the concrete will not do much. I suppose you would have to paint all six sides like Joe suggestes. I my case it wouldn't be an option because my fence is stained.As far as epoxy being toxic and expensive, it's not. A gallon of epoxy "based" acrylic paint is about $35 cdn. It may be as toxic like all acrylic paints before it's dry. It becomes a hard plastic that doesn't degrade (as long as it's not exposed to UV). It is not nearly as toxic as creosote or other chemicals which never dry out and leach into the ground.I tried this experiment because I heard so much about posts rotting. I assumed it was the portion in the concrete. If it's not that portion then I suppose I'll have to think of something else.Why do you guys suppose that the post I used for the experiment held up so well after being submersed in water 24 hrs a day for over a year? The paint wasn't even affected.The cats are doing fine Joe. Thanks for asking.Gaby
*A very interesting topic. Depends on your local precip, the quality of the soil (clay-loam-sand), the quality of the post, etc... I'd like to hear of clever ideas that are both effective AND fast/cheap/easy to implement AND suited to regional circumstances. Not sure paint meets the second requirement. Gaby, maybe your water is very oxygen-poor and bad for fungal growth?Main thought seems to be to keep it dry. Sealing below-grade makes sense to me ... any small amount of moisture can migrate out through the highly porous above-grade ... I believe the epoxy helped just like leaving the post in a sealed, dry plastic bucket would help -- consider this: soggy wood is NEVER going to release moisture into pure water, so below-grade porosity is here a loser. Someone here has suggested lumber shrinkage allows water between post and concrete overshoe, so it's always full ... also, water of course migrates through concrete easily. Paint would stay with the wood tenaciously.Going to such extremes to seal the post in drier environments would be unnecessary, perhaps even a negative.No wood at all below grade is awful nice, but how to keep a lone post from falling over? THICK rebar dowel + post anchor?I built a 9' tall pergola for a lady who just HATED the look of diagonal bracing. I insisted that if she wanted it that way we would have to bury the posts in her sopping ground. Good cedar, but I still worry...
*An additional thought. The water isn't the only culpret here. Oxygen (or generally air) would be required by the rotting organisms. At or near the surface provides the greatest quantity of oxygen or CO2. I would stipulate that a post submerged in water would take longer to rot than one periodically exposed to air. This could explain the rot band at the surface with the post bottom looking great.So would this mean a "air-tight" covering, like the paint Gaby used, applied in this vulnerable zone could help delay rot even though it could elevate the water content of the wood? What do you think? SWright
*I have never had a problem with pressure treated posts in concrete either. The portion above ground in the sun and rain is usually in worse shape than the part in concrete. This is in a wet gulf coast area so there is plenty of moisture but no frost.(although I did have to wear long pants one day last week). We also get a much better grade of treated lumber here being on the coast. I have run into several jobs lately where epoxy paint was used on wood with very bad results. It was peeling off within months from the movement of the wood. I guess the epoxy was not elastic enough to move with the wood and began to crack off badly. I dont think that wood rots when it is completely submerged in water thats why they are pulling up all of the logs that sank before they got to the sawmills 100 yrs ago and useing them. Maybe you kept your post too wet to rot. Another unpainted post next to it would have helped your experiment as well.
*Many of these points make sense. It seems to be that it's a combination of wetting and drying that causes wood rot. This would happen more at the point just above the cement. I have some more things to think about now. Thanks for your input guys.Gaby
*A company is pulling submerged logs [perfectly preserved] from Lake Superior that are well over 75- 100 years old. I think you are tooting the wrong horn.. It takes bacteria and moisture to rot wood. Put concrete well above ground level and taper it away from the post like a previous post suggests.. L. Siders
*Hi Guys,Real glad you didn't get your feathers ruffled by my first post Gaby.Some 4X4 PT will rot through and through in less than 10 years when encased in concrete below grade here in OR. There are many variables in PT woods that I don't think I'll get into now.Wood rots when these conditions are present.A non sterile enviroment. A givenHigh moisture content. Unsure of precise amount but if it feels wet it is wet.An aerobic enviroment. This is not found at the bottom of lakes and rivers which is why it is so hard for us to breath there.Tempertures between about 50 deg F and something less than boiling.Like Lawrence I'm a big advocate of gravel encasement and believe that compacted gravel develops enough compressive strength for most lateral forces. Engineers calculate such stuff because they have to.Red Cedar lasts about 10 to 30 years below grade around here. Our PT lumber is almost exclusively Hem Fir. You folks using SYP PT have a much better product for rot resistance.joe d
*Per a UMass wood technology site, wood starts to rot when the mositure content reaches about 28% (mold starts at about 20%).Bob
*We're pretty close to a bay community and several rivers.I've seen alot of submerged posts on piers and boat landings that were soft at the water line but solid above and below this point. I always told myself this was because of floating debris abrading the post and ice forming at this point (I guess no in the bay though)Interesting topic.
*Please excuse the lenghty post,but I think it will pretty clearly demonstrate what worked and what did not work with Gabby's idea.In north carolina there is a huge lighthouse( Cape Hatteras Light). Last year this gigantic masonry structure was jacked up and moved about a mile I think( There was actually a pretty cool web site at the time showing the move---remember this thing was several hundred feet tall and they had a camera at the top) What makes the structure pertinent to our discussion is that it was built on a WOOD foundation.It seems that the builders(like a hundred some years ago)dug down into the sand maybe 80 feet. They pumped the hole dry and laid in some wood cribbing(Yellow pine I think). Anyhow they built this cribbing up pretty high but still well below the surface they built a stone foundation and then the brick lighthouse on top of that. So all this time that huge,historic building,has been resting on untreated pine maybe 60 feet below sea level. The wood has been continuosly wet,bathed in salt water out of the reach of sunlight or plant action.The reason the building had to be moved was that it sits on a barrier island which is slowly drifting eastward.When it was originally built I believe it sat something like 1500 feet back from the shore,but at the time of the move it was only a few feet from the sea. several previous attempts to prevent erosion were unsuccessfull.As you might imagine this was a major controversy with a big National Park service vs. THE LOCALS thing going on.So,the end result is that untreated wood can last indefinitely if kept continuosly submerged and out of reach of sun and plant life.I may be a little off on the depths,or lumber species used. My 10 year old son has ALL the details memorized,but he is in school right now and un-available for consultation.Good Luck All,Stephen
*My experience with this subject in Northern Illinois is that posts don't rot in concrete. They rot, if and when, at the wood/concrete foundation "joint" (at ground level). In order for rot to occur there has to be moisture and air present. (This explains why timbers can be retrieved unscathed after 100 yrs plus under water. (or encased in concrete for that matter.) I've had the best luck using 6 x 6 posts (minimum) and sloping the top of the conrete foundation away from the post for drainage. Periodic treatment with a penetrating sealer doesn't hurt either. It also helps to use a post cap or bevel the top to a point so water doesn't stand on the flat post top. Using a good post helps also. I can't believe the crap that passes for lumber, posts and beams these days.EB
*This is how I'm understanding everything from what I've. Posts don't rot beacause they are wet, they rot because of bacterial growth. For this to happen you need a moist environment but you need air aswell. This would explain why submerged trees are well preserved. This makes sense. The reason my test post didn't rot in the water was because of these reasons. However, by coating it in a plastic shell I'm prevent any air and water infiltration which my occur bellow ground level. When a post is encased in conmcrete it can stay wet longer than if it was held in place with compacted stone which allows for better drainage. Therefore the epoxy coat on the post would only help the portion of the post that is below grade and in the concrete. The portion just above the concrete (above grade) is still susceptable to rot. The best thing to do then is to bring the concrete above grade and slope the top away for the post and seal the protruding portion of the post with paint or sealer. I suppose using flexible caulking around the concrete/wood junction wouldn't hurt either because it will prevent water from getting in between the wood and concrete. All of what you guys have said made sense so did I get the "jist" of it or am I still missing something? If I did understand everything correctly then my experiment was a partial solution depending on what type of soil condition you are dealing with (sand, stone, clay, etc.)BTW, Joe I don't get offended anymore about anything. I learned my lesson here at Breaktime a while ago(Heh..Heh). I never pretend to know everything. I state facts and give opinions about what I've experienced. The title to this topic is "maybe found cure for rotting fence posts in cement". The key word being "MAYBE". I stated what actually happened then I asked for comments. As it turns out I was only thinking of one aspect of the problem (that being water). And now I appreciate all the comments because it makes that much more sense. So, let your comments fly because I'm here to absorbe your knowledge and share whatever I can. Although, I don't see a need for being harsh with someone and using words like "cockamamie", you mean person you! (just kidding dude!) LOLGaby
*Gaby...good rationalizations, however there are a few more factors. First of all, posts absorb moisture and or expel moisture (and swell and shrink accordingly). They do this by drawing moisture up through the end grains. You apparently used kiln dried lumber. Then you plugged up these end grains twice, first with your epoxy paint and then with your concrete. What in fact you did was stabilize your moisture content, and prevented your post from expanding or contracting. This is why the epoxy paint didn't shed, because it was bonded to a dry stable surface. This paint actually kept the moisture in the concrete and out of the post. Bravo. A method with definite advantages. Next, your post was likely quarter sawn. If you look at the end grain you will likely see the grain pattern. This cut will not crack all 4 sides like a cut which contains the core of the tree. However it will change shape slightly, (will become less than square). As it does this your coating will shed. If you seal the top of the post or give it a post cap that shed's water, you will stabilize the moisture content significantly. This is another reason why your finish did not fail. Had it been one of these core containing posts I would wager that the results would have been shedding finish and a very moist post. Concrete is porous, and transfers moisture very well. Therefore I still recommend keeping it away from ground level for a fence. Stay with me here... If you fill up the hole half way with concrete and top it up with gravel....moisture level is far less than in concrete. Secondly, in a situation where frost is present, the larger the footing at ground level, the greater the pull of the frost yanking your footing out of the ground. The surface area of a 4x4 or a 6x6 is far less than that of an 8" sonotube. Also,regarding a sonotube footing, since concrete holds more moisture than the planed side of a post, the ground actually freezes to the footing giving even more grip, to cause your footing to fail. Since the footing I discribe is significantly larger 2' down, it actually anchor's the post into the ground against the effects of frost. Third, if you neglect to use a sonotube and just slope your concrete to the outside of the hole...as I said before(see previous post), the footing will fail. L
*Well guys, I think that varying conditions make all the diffence in each situation.As for Lawrences Idea of gravel to keep water away, that is as wrong a concept as one could have. It is even worse thinking than Gaby's. People think that using gravel lets water escape like it does around foundations. Problem is that around foundations the gravels is part of the system with the DRAIN TILE. water will travel the easiest route. gravel underground leaves a "pocket" for water to escape into and their needs to be a drain tile to let it escape further.... without drain tile, you have a hole full of gravel collecting water with no place else to go. If you are not having water build up in your gravel holes, that is because you are above the water table and have at least decently draining soil.Pete Draganic
*A major threat to in ground posts that I have observed is damage from weed-whips. Especially cedar posts. Many of my customers use lawn services, and those industrial strength weed-whips really do a number on cedar. Metal sheilds or replaceable wooden sheilds seem to be the ticket to protect them.John
*All due respect pete...do you think I would give this information without checking to see if it works? I guess I had more respect for you than you for me. There are more reasons than those expressed above for my methods. If your water table is at ground level, and you get enough constant rain to keep this kind of footing at 23% moisture...I would guess a rainforest, or a swail about 300' long in Clearwater. I guess it isn't right for your area. (but aside from a metal fence spike that leans after a month...what would be?) Sorry for suggesting something too different to look at pete. If I am so far off base....would someone else stand up with some logic to convince me...PLEASE? I don't want to be stupid forever! L
*Lawrence,Don't get your panties in a bunch. The primary point I was trying to make, regarding your method of using gravel, is that gravel does more to invite water into the hole than it could ever do to expel it form the hole.Gravel on helps keep water away where it is a part of a system including drain tile for instance.I am not trying to insult you but this is a subject I have put a lot of thought into over the years. The idea is not too different to look, I have looked at it and my observation is posted herein.If I am wrong, please let me in on the logic or properties of this setup and what makes it work......Don't take it personally, but I have to strongly disagree with your gravel method.Pete Draganic
*Ok pete, here it is. What retains moisture, a rock, mud, concrete or air. Air is between the stones...(gravel). Stone does not retain moisture. Concrete and mud do. I think you may be equating drainage stone around a foundation which is not in contact with the air and does not allow evaporation. Go to a gravel yard 3 days after a rainfall, dig into the pile 2'. It will be dry.All soil even clay absorbs moisture, and all moisture does evaporate. Whatever moisture not absorbed into the ground, evaporates within days. Also during dry spells the soil around the post drys as well. Unless this footing is in constant contact with water...the advantages are obvious. Pete, it wasn't a personal attack, however I wanted to be sure to get a response...I need logic to retain this tenuous grasp on sanity(rough year), and I want to have a firm grasp of when exactly senility ends my ability to logically come to conclusions. Oh, but I could be entirely wrong! L
*Pete and Lawrence,Let me ask both of you this. Take to identical posts. One encased in a 10" concrete cylinder and put into a plastic container filled with water just below the top of the concrete. The other is put into the plastic container and filled with crushed stone, then water is poured in to fill the container just below the top of the crushed stone. Obviously the water has no place to go it is emptied after 2 days. The posts are then given 2 days to dry out in the bucket and the process is repeated over and over for a year. In both your opinions which post do you think will be better off?This is what I think will happen but then again I'm new to this kind of reasoning. The container with the crushed stone will let the water come in contact with the post. After 2 days the post will have absorbed as much water as it can in those 2 days. The post encased in concrete will not absorb as much water because the concrete will not allow the water to come in contact with the wood immediately(it may take some time for the moisture to migrate through). Given that both posts would have the same amount of time to dry out, it seems to me that the concrete encased post would be less moist for the majority of the time. The crush stone encased concrete will be completely wet every 2 days for a period of 2 days.As far as applying a coat of epoxy on the posts, I don't think I had the wrong idea. If you were to apply a water and airtight plastic shell on both of them, given their current situation they would both be better off. Remember that I am only talking about the condition of the post in either the concrete or the crushed stone. The condition for the portion above is the same for both in this hypothetical situation.I'd like both your opinions (or anyone else's for that matter) on this hypothetical case. Oh, and remember we're just shootin' the shit here so no need fer flyin' fur.Gaby
*Hey gabby, you are missing one factor. You had better drill a few holes in the container with the gravel...to simulate the absorption into the ground. The post encased in concrete will never dry out completely. It would take a week or two for it to dry. The post surrounded by gravel is dry within a couple of days. Dependant upon soil conditions I would expect the gravel topped post to last at least twice that of the concrete (Sonotube), footing. I have been using this method in Ontario for 8 years now. I think time will tell. I do know that I have replaced many, many concrete encased posts that there was nothing left of at ground level...they were shaped like great big toothpicks. (just an observation)
*hello fellas, just thought I might stick my nose out and see what happens. 1. I knew a rancher who fenced his own property and he used a combination of t-bars and railroad ties. the t-bars were standard but the railroad ties were spaced about 50 feet apart and set vertically in cement so as to "lend stabillity" to the fence. the key ingredient that he shared with me though is that he put a plastic garbage bag (shopped around for non-biodegradable) around the end set in concrete. (dirt/concrete/plastic/post like that) 2. if that is too much trouble then find a supplier for black locust fence post, they don't seem to rot (I just renovated a 90yr old house with blacklocust foundation post under it), bugs dont eat it , and if you dont plant them upside down they have a tendency to take root (not joking) the only draw back is that blacklocust is fatally poisonous to horses.
*Boys, boys, boys . . . If we all switched to PVC posts we wouldn't have to argue this point further! But seriously folks, there are several signifcant points made here though I don't think anyone has put them all together yet.First, concrete can be made water tight. This is not a joke. Look at the inside of your poured concrete foundation wall. Is it wet? I hope not!Second, stone will absorb water. The advantage to stone is that once the hole is no longer inundated, assuming that happens, there are significant air spaces. (You should use open graded or washed stone). This allows drying to occur in cycles.The wood post will reach moisture equilibrium with its surroundings. How quickly this happens depends on wood type. Jon Arno from across the alley could give a better (read more accurate) explanation of this phenomenon and what effects it has on the wood in question.I stand by my previous post (pun intended). If you use quality stock (6x6), high strength concrete (not post mix poured dry into the hole and wet down), and allow drainage away from the post/concrete joint, you'll have a fence that'll last longer than the memory of who installed it and when.Of course I could be full of sh*t. I post too often to have any credibility left. EB
*All this discussion stirred my memory a little. You know how it is you just can't remember every detail of every job right away. What I really like is a deep cylindrical hole with a poured pad at the bottom. The post is set and plumbed with crushed rock backfill just shy of the top of the hole. Then a thin (3-4") cap is poured just proud of grade.Of course the post here would be .60 to refusal LP22 or perhaps .40 for a fence.The pad way down at the bottom is resistant to frost heave or settling. The crushed rock develops sufficient psi and allows drainage. The top cap reduces water entering the crushed rock and aids resistance to lateral deflection at the most vulnerable point.Both pt and cedar failure below grade after less than ten years does sometimes happen here. A wet enviroment with tempertures in the rot range almost yer round are unique factors to the area.As usual your getting good mileage out of your topics Gaby.joe d
*Not a bad thought. It just dawned on me that permanent woodfoundation systems usually specify about 4" of porous 3/4 gravel (washed) or 1/2 crushed rock as footings for pressure treated plates. 6 mil poly sheeting is draped over the PT stud wall. There is an extensive table regarding types of soils and design properties ranging from well-graded gravels, gravel sand mixtures w/little or no fines being rated "good" for drainage to organic clays of medium to high plasticity, organic silts being rated unsatisfactory.The following should work:Use only 6" KDAT posts, not cut from the center of the treeHeat shrink (think electrical) one end closed tubes on post(UV proof, pliable in subfreezing cold, won't get all floppy with heat, tough enough to withstand weed wackers).Washed gravel in bottom of holeMixed concrete with fibers to hold post, trowel to shed.Flashing just above ground set in groove (like flashing on chimney)PVC tubes inserted into gravel and extending to ground level, ganged as a manifold.Temp and moisture sensors at bottom of PVCPhotovoltaic cells incorporated into fence boards to powersump pump or heater elements as needed (hardwire backup in cloudy environs).And then I woke up.................daydreaming again!Seems like I saw quarried stone fence posts along I-70 or I-80 in either Kansas or Nebraska.....a little tough to nail to but great for wire! Thor
*Gentlemen,I have given some serious thought to all of this, and the only thing that those who are having problems have in common is the frost/freezing, type of posts, and method of burying.My area has an extremely high water table, extremely humid and hot weather, and very nice quality syp pt posts.We did a percolation test in my back yard, and we were supposed to dig a hole 24" deep, and fill it with water. After filling, we were to document the amount of time it took for the water to soak into the surrounding soil. Well, after digging the 24" hole, we didn't have to fill it with water. It filled up on its own (about half way) This is of course during our rainy season. Totally freaked out the inspector.The reason I mention this is because I have noticed several people discussing how dry the ground is, and how deep the frost line goes. Well, we bury posts in 12" to 18" of concrete, with no backfill, no gravel, no nothing but concrete. We fill the hole, and build up about 2" above ground, then tpaer the concrete away from the post. We have never had the rot that you speak of. I have never seen it, and until recently, have never heard of it.The factors also include the type and quality of wood. We use .40 pt syp posts, and they are usually dripping wet with treatment chemicals. If you were to drive a nail, it would probably splatter you with droplets (no lie)The only things I see that seem to have a bearing on all of this is non syp pt posts, frost/freezing, and method of burying the posts.Beats the hell out of me!Just a thought...James DuHamel
*Mileage! No shit eh, Joe.Seems like everything I post causes some commotion. Must be because I'm Canadian.In any case there is a bunch of good information here so I hope everyone can get some benefit out of it. I know I have.Later!Gaby
*Hi Gaby,Yeh for you Kweebekcause that might be Klickage.
*Twenty years of dock building and now several years of tennis courts, with cedar and pressure treated fence posts....Oh and we allow for 4 foot frost and have even more in snowless years like this year....So out on a limb I go and share my thoughts...Cedar rots much faster than PT around here....Docks (that are not pressure treated) rot at the water line mostly, followed by the upper structure. Rarely are the timbers below a foot or more of water rotted even after many decades.Posts need to be set deep in the ground here, hopefully not into the water table, and the concrete should be larger at the bottom, bell shape so as to limit frost heaving...Soil must be kept away from the post with concrete that is sloped for rain drainage...Cuprinol if you can buy it can be sprayed on your cedar posts annually and it's a good idea to clear away leaves and other organics that build up at the base....Finally, if you want the posts to last even longer use living trees....or of course the new vinyl is looking like a great product even though you all hate vinyl siding...near the lake cutting back the ice to finish our latest crib dock rebuild,ajps...I have fooled with double sono tubes, gravel and other ideas...Depending on the conditions some of the ideas seam to work though my major concern is twenty years of frost heaving causing my tennis courts to lose a little curb appeal...Remember concrete is porous and things rot easily when covered with leaves (little compost piles!)
*
I think the rot comes as part of the wet and dry cycle outdoor installations involve. Above grade. where it essentially dry, you have no rot. 6-12 inches below grade, where it is always wet, you have no rot. At and just below grade, where it is sometimes dry and sometimes wet, you get rot. Somehow the trick is to keep it essentially dry or always wet. Maybe?