I've just spent a few back breaking days laying my new patio and decided that I wanted to use a coloured mortar. I followed the instructions for making a semi dry mortar mix and everything seemed to go OK. The weather was fine for the next 24 hours but the mortar has just remained very loose and crumbly. Since then it has been raining nearly non stop and the mortar has not set. The dye has also run a bit (I can live with that though as the slabs are the Yorkstone weathered look and so it isn't really noticeable).
It is now 3 days after doing the pointing and I can still scrape the mortar out just using my finger. I'm guessing that I'm going to have rake it all out and start again.
But before I go though it all again, I'd like some advice on where I could have gone wrong. The slabs had been soaking the day before I did the pointing (it had been raining for virtually the whole week) and so I don't see that it could have been them drawing the moisture out. Am I best to repoint using a wet mortar next time (I was trying to avoid this because of the staining problems)?
Coloured Semi Dry Mortar Mix Not Setting! - Do I need to do it all again?
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84-1093879891
There's all sorts of possible causes but the two most common reasons for mortar/concrete not setting, when in the hands of non-professionals are...
1 - Use of perished cement
2 - Contamination with sugar
...Perished refers to cement that has gone past its "Best Before" date. Even if kept in unopened bags, cement has a relatively short useful life. It 'acquires' moisture from the atmosphere and loses its potency. You'd be surprised just how many DIYers have a half-used bag of cement tucked away at the back of the shed and they daren't throw it away because they remain convinced that, one day, it will "come in handy".
Only ever use fresh cement. Anything more than 3-4 weeks old should be discarded. If you're ever in a BM's yard, you can tell which is the freshest cement by feeling the bags - freshly-made cement often retains its warmth for 3-4 days after manufacture.
Moving on to the second problem, many people don't realise just how damaging sugar, even in minute quantities, can be to cement and cement-based products in a plastic (unset) state. A single bag of sugar thrown into the drum of a concrete mixer wagon will prevent the concrete inside from setting for around 6 hours - this is one of the tricks the concrete wagon drivers use if they break down with a full load still in the drum. It means they have a chance to get repaired or towed to somewhere to discharge before the concrete starts to set.
If you've prepared your mortar or pointing mix with water that's been tainted with Vimto, an ice lolly, beer, a sweetened cup of tea, or anything with sugar in it, then that can play havoc with your work.
So: is there any chance 1 or 2 could be implicated in your mystery?
1 - Use of perished cement
2 - Contamination with sugar
...Perished refers to cement that has gone past its "Best Before" date. Even if kept in unopened bags, cement has a relatively short useful life. It 'acquires' moisture from the atmosphere and loses its potency. You'd be surprised just how many DIYers have a half-used bag of cement tucked away at the back of the shed and they daren't throw it away because they remain convinced that, one day, it will "come in handy".
Only ever use fresh cement. Anything more than 3-4 weeks old should be discarded. If you're ever in a BM's yard, you can tell which is the freshest cement by feeling the bags - freshly-made cement often retains its warmth for 3-4 days after manufacture.
Moving on to the second problem, many people don't realise just how damaging sugar, even in minute quantities, can be to cement and cement-based products in a plastic (unset) state. A single bag of sugar thrown into the drum of a concrete mixer wagon will prevent the concrete inside from setting for around 6 hours - this is one of the tricks the concrete wagon drivers use if they break down with a full load still in the drum. It means they have a chance to get repaired or towed to somewhere to discharge before the concrete starts to set.
If you've prepared your mortar or pointing mix with water that's been tainted with Vimto, an ice lolly, beer, a sweetened cup of tea, or anything with sugar in it, then that can play havoc with your work.
So: is there any chance 1 or 2 could be implicated in your mystery?
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HelenM
- Posts: 4
- Joined: Tue Aug 24, 2004 2:55 pm
Hi, Thanks for the quick reply.
The cement was unopened and I'd only bought it 2 days previously at B&Q, so I don't think it could have been that.
I used a hired cement mixer and didn't have to add any additional water as the sand was already wet (that was also brand new in an unopened bag) and the mixture seemed to be the right consistency without adding extra water. So unless the cement mixer was contaminated then I don't think it could it could have been that.
I'm going to rake it all out and try again at the weekend. I'm going to buy the mortar and cement from somewhere other than B&Q (just in case it was that). Am I more likely to have success using a wet mortar or do you recommend trying the semi dry mortar again?
The cement was unopened and I'd only bought it 2 days previously at B&Q, so I don't think it could have been that.
I used a hired cement mixer and didn't have to add any additional water as the sand was already wet (that was also brand new in an unopened bag) and the mixture seemed to be the right consistency without adding extra water. So unless the cement mixer was contaminated then I don't think it could it could have been that.
I'm going to rake it all out and try again at the weekend. I'm going to buy the mortar and cement from somewhere other than B&Q (just in case it was that). Am I more likely to have success using a wet mortar or do you recommend trying the semi dry mortar again?
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alan ditchfield
- Posts: 203
- Joined: Thu Jan 01, 1970 1:00 am
- Location: Preston / Lancashire
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84-1093879891
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HelenM
- Posts: 4
- Joined: Tue Aug 24, 2004 2:55 pm
I used a 3:1 mix.
I've just redone it all yesterday - again using a semi dry mix and (fingers crossed) it seems to be setting much better. There's some loose powder in the joints but underneath that it seems to be setting much harder.
If it doesn't work this time I'm giving up and going for one of those polymeric sands!
I've just redone it all yesterday - again using a semi dry mix and (fingers crossed) it seems to be setting much better. There's some loose powder in the joints but underneath that it seems to be setting much harder.
If it doesn't work this time I'm giving up and going for one of those polymeric sands!
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84-1093879891
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Alan Collinge
- Posts: 17
- Joined: Thu Jul 15, 2004 5:27 pm
- Location: Kearsley Lancs
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Alan Collinge
- Posts: 17
- Joined: Thu Jul 15, 2004 5:27 pm
- Location: Kearsley Lancs
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84-1089053830
Actually, I found that knackered bag of cement on the back of a Tranny Tipper belonging to one of the better paving and surfacing contractors in the UK!!
The lad driving the van, who shall reamin nameless for the time being, swore blind that he'd been meaning to sling it in a skip for the past week, but just hadn't had that chance.
And you're not the only one struggling a bit with v3 - there's a few things I want to change, but itls only be actually using the system that I can find out what does and what doesn't perfoform as required.
Any suggestions for improvement are always welcome.
The lad driving the van, who shall reamin nameless for the time being, swore blind that he'd been meaning to sling it in a skip for the past week, but just hadn't had that chance.
And you're not the only one struggling a bit with v3 - there's a few things I want to change, but itls only be actually using the system that I can find out what does and what doesn't perfoform as required.
Any suggestions for improvement are always welcome.