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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Cement shelf life
I want to fix (bodge) a fence post aand I've got some ready mixed mortar
rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! Can anyone advise, please - I have tried googling, but the answers cover such a wide range I'm not much wiser, and John Scmitt's FAQs don't seem to answer this one. mike |
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mike ring wrote:
I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! Can anyone advise, please - I have tried googling, but the answers cover such a wide range I'm not much wiser, and John Scmitt's FAQs don't seem to answer this one. mike should be ok. Normally it sets into a rock when its had it. NT |
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"mike ring" wrote in message . 1.4... I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! It absorbs moisture from the air and forms hard lumps. If it hasn't done this I still wouldn't recommend building a house with it but for a fence post go ahead. The worst it can do is refuse to set. |
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mike ring wrote:
I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Aren't you thinking of plaster? David |
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"Lobster" wrote in message ... mike ring wrote: I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Aren't you thinking of plaster? David I dont think so. Plaster when its old sets as soon as youve mixed it and steams |
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On Fri, 25 Mar 2005 21:34:16 GMT, "keith_765"
wrote: "Lobster" wrote in message ... mike ring wrote: I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Aren't you thinking of plaster? David I dont think so. Plaster when its old sets as soon as youve mixed it and steams I added some mortar plasticiser liquid, which I had lying around, to some old cement in a mix which kept it alive a bit longer. The bag was about 6months old and had been left open. |
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"Mike" wrote in :
Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! It absorbs moisture from the air and forms hard lumps. If it hasn't done this I still wouldn't recommend building a house with it but for a fence post go ahead. The worst it can do is refuse to set. That's the problem - it does seem to refuse to set, but I wanted to find out how long I need to wait. It's been 24hrs and my test bit is still toffeeish, it wouldn't hold up a post. I guess that means it's knackered, but with an undated bag, and it looking perfectly good, it's a bit hard for a muppet like me to tell. mike |
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Lobster wrote in
: It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Aren't you thinking of plaster? No, Supamix dry mortar mix. The bag says store in a dry place, which I have, but no mention at all of a shelf life or use by date. mike |
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"mike ring" wrote in message . 1.4... "Mike" wrote in : Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! It absorbs moisture from the air and forms hard lumps. If it hasn't done this I still wouldn't recommend building a house with it but for a fence post go ahead. The worst it can do is refuse to set. That's the problem - it does seem to refuse to set, but I wanted to find out how long I need to wait. It's been 24hrs and my test bit is still toffeeish, it wouldn't hold up a post. I guess that means it's knackered, but with an undated bag, and it looking perfectly good, it's a bit hard for a muppet like me to tell. It's dead :-) |
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The only way I've had cement go off on me was going hard or lumpy - whatever
wasn't rock solid would always set. The only problem I've really had was with some Wickes exterior tile which is quick setting normally but wouldn't set after 6 months in the open bag. I wonder if what you have isn't plain old sand and cement but something more like my tile cement? I'd give your test piece a bit more than 24 hours to go off though - give it another couple of days before you declare the stuff useless. Andy. |
#13
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In message , mike ring
writes wrote in news:1111777247.841760.134400 : I want to fix (bodge) a fence post aand I've got some ready mixed mortar rhat must be a year or two old. It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. should be ok. Normally it sets into a rock when its had it. NT That's what I thought, but considering the age I tried fixing a bit of pointing in my paving, and it doesn't seem to be going off. I've checked the bag, and can't find a date on it, but 6 months is bandied about as a life. But if *that's* so, how can I be sure I'm buying fresh if there's no date? And how long *should* it take to set hard - ish? Show it some porn - hard in no time -- geoff |
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mike ring wrote:
Lobster wrote in : It looks perfectly good, but I understand that cement has a short shelf life, even if kept warm amd dry; however mine looks perfect. Aren't you thinking of plaster? No, Supamix dry mortar mix. The bag says store in a dry place, which I have, but no mention at all of a shelf life or use by date. What I meant was, it's well known and indisputable that plaster has a short shelf life, cos old stuff goes off far too quickly when you try to use it - I, for one, had never heard that cement has similar properties so I just wondered if you were confusing the two. David |
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Lobster wrote in
: The bag says store in a dry place, which I have, but no mention at all of a shelf life or use by date. What I meant was, it's well known and indisputable that plaster has a short shelf life, cos old stuff goes off far too quickly when you try to use it - I, for one, had never heard that cement has similar properties so I just wondered if you were confusing the two. No, it's the opposite. It refuses to set, it'e *still* not gone orf at all, just dried to a stiff stodge! Of course, I've never played with plaster, I can't even work cement. It's a dry mix of sand and cement to some BS part xyz, which I take to mean it should work. It seems from googling to be assumed there is a shortish shelf life, but no-one has mentioned what it is, or why it dies while looking in good nick. I'll have to go and get some more, but I'd really like to know what's going on mike |
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#17
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In article , mike ring
writes Lobster wrote in : The bag says store in a dry place, which I have, but no mention at all of a shelf life or use by date. What I meant was, it's well known and indisputable that plaster has a short shelf life, cos old stuff goes off far too quickly when you try to use it - I, for one, had never heard that cement has similar properties so I just wondered if you were confusing the two. No, it's the opposite. It refuses to set, it'e *still* not gone orf at all, just dried to a stiff stodge! Of course, I've never played with plaster, I can't even work cement. It's a dry mix of sand and cement to some BS part xyz, which I take to mean it should work. It seems from googling to be assumed there is a shortish shelf life, but no-one has mentioned what it is, or why it dies while looking in good nick. I'll have to go and get some more, but I'd really like to know what's going on mike Cement will absorb moisture from the air and will hydrate (set) in the bag, often this will be seen as solid lumps but it can remain as a powder but will be a lot less reactive than new cement which is why it can take a long time to set and be fairly weak. I would get a new bag if its at all critical and I would count not losing face in front of your neighbour as being critical -- David |
#18
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On Sat, 26 Mar 2005 12:57:34 +0000,
wrote: you can sort old plaster out with Tartaric acid, Filed away for future reference... Mind you I think everyone ought to learn to plaster with old stuff, in small quantities. The fact it sets so fast forces you into the proper "whack it on and leave it" method of working rather than "put it up, smooth it, put more on in the hollows, smooth that, faff about, why won't that buldge smooth out any more? ah it's set..." -- Cheers Dave. pam is missing e-mail |
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#20
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"Dave Liquorice" wrote in
ll.com: you can sort old plaster out with Tartaric acid, Filed away for future reference... Mind you I think everyone ought to learn to plaster with old stuff, in small quantities. The fact it sets so fast forces you into the proper "whack it on and leave it" method of working rather than "put it up, smooth it, put more on in the hollows, smooth that, faff about, why won't that buldge smooth out any more? ah it's set..." YOU WERE WATCHING!! and that's just filling cracks! Thanks to all for the info, I wish they'd put it on the bag mike |
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In message om, Dave
Liquorice writes On Sat, 26 Mar 2005 12:57:34 +0000, wrote: you can sort old plaster out with Tartaric acid, Filed away for future reference... Mind you I think everyone ought to learn to plaster with old stuff, in small quantities. The fact it sets so fast forces you into the proper "whack it on and leave it" Had that happen to me several times - with "new" bags of plaster The problem is that, while nobody else notices, it leaps out at me every time I go past -- geoff |
#22
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mike ring wrote:
"Mike" wrote in : Just for interest, if it does deteriorate, could anyone explain the mechanism - it would ease the pain of shelling out for a new bag! It absorbs moisture from the air and forms hard lumps. If it hasn't done this I still wouldn't recommend building a house with it but for a fence post go ahead. The worst it can do is refuse to set. That's the problem - it does seem to refuse to set, but I wanted to find out how long I need to wait. It's been 24hrs and my test bit is still toffeeish, it wouldn't hold up a post. Will take a couple of days at this temp to set hard. I guess that means it's knackered, but with an undated bag, and it looking perfectly good, it's a bit hard for a muppet like me to tell. Its fine. You are just impatient. If it didn't turn to rock, its OK. I just used a half bag I had leftover from last year, and it went off allright in a coule of days, once I had sieved the rock hard lumps out of it and used a bit more than usueal for luck... Oh by teh way, there is not size dependent cire time for concrete. Its only depebndeint on temperature. generally it sets overnight in summer, and about 2 nights in winter, to the level it feels 'hard' and takes on full strength over a couple of weeks. It takes time to DRY OUT though... mike |
#23
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Better still, give up the addiction to Ordinary Portland Cement and
take up an enthusiasm for lime. |
#24
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In article , The Natural
Philosopher writes Its fine. You are just impatient. If it didn't turn to rock, its OK. I just used a half bag I had leftover from last year, and it went off allright in a coule of days, once I had sieved the rock hard lumps out of it and used a bit more than usueal for luck... This is not true, cement powder loses its reactivity and you will end up with a weak matrix, not critical as far as a post mix is concerned but could be critical elsewhere. Cement is at its most reactive just after its manufactured and gets slower and weaker from then on. Just because it has set doesn't mean its strong. Oh by teh way, there is not size dependent cire time for concrete. Its only depebndeint on temperature. generally it sets overnight in summer, and about 2 nights in winter, to the level it feels 'hard' and takes on full strength over a couple of weeks. You obviously don't work with structural concrete or even slabs that need to have achieved a certain strength before loading. Concrete has initial set (surface hard) and final set (hard all the way through), you are right to say that these can be dependant on temp but you can achieve a false surface set if you have severe drying conditions. The rate of strength gain of concrete is a well understood area and are usually measured at 1, 3, 7, and 28 day intervals. It takes time to DRY OUT though... -- David |
#25
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And plastering with lime is much better too. It sets slowly and gently
so you can work in a relaxed way, stopping for tea when the mood takes you. Give up OPC and gypsum. |
#26
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"Biff" wrote in message om... Better still, give up the addiction to Ordinary Portland Cement and take up an enthusiasm for lime. Hmm. I have some enthusiasm for lime but supporting posts whilst waiting for it to dry would test this enthusiasm well beyond it's limits :-) |
#27
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"Biff" wrote in message om... And plastering with lime is much better too. It sets slowly and gently so you can work in a relaxed way, stopping for tea when the mood takes you. And a three course dinner, day off sightseeing and then a weekend break before it's set :-) |
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