epsilonGreedy Posted September 1, 2019 Share Posted September 1, 2019 (edited) The other week I complimented a building pro on the consistency of his mortar mix. It was not sloppy but still had nice pliable bounce. As the conversation developed I realized he was using about 80% more plasticiser than recommended on the bottle which got me thinking about why there is a limit. Is it: The chemicals in plasticiser are detrimental to the strength of mortar? Excess plasticiser results in too many bubbles trapped in the mortar and above a certain threshold the percentage of permanently trapped air in the mortar will compromise its strength? Mortar with an excess of trapped air is susceptible to accelerated weathering? Edited September 5, 2019 by epsilonGreedy Link to comment Share on other sites More sharing options...
Declan52 Posted September 1, 2019 Share Posted September 1, 2019 It puts to much air into the mix which makes it go like fluff. Once it's hard you end up with voids in the motar so it's not as strong as it should be. With voids then frost can get into it and it will crumble. I always used this type where you have the small bit at the top to measure it out. Squeeze the main bottle to fill the small bit and drop it into a bucket of water then into the mixer. https://www.amazon.co.uk/Multicrete-One-Shot-Plasticiser-Concentrated/dp/B07BBJRT2C/ref=mp_s_a_1_1?_encoding=UTF8&qid=1567361968&s=gateway&sr=8-1&srs=5309686031 To get a good motar the secret is just to let it mix and mix and mix. If you just lash water in till it looks right but not properly mixed then it dries out to quick. 1 Link to comment Share on other sites More sharing options...
PeterW Posted September 1, 2019 Share Posted September 1, 2019 14 minutes ago, Declan52 said: To get a good motar the secret is just to let it mix and mix and mix. If you just lash water in till it looks right but not properly mixed then it dries out to quick We used to be able to tell when we were last drop on the readymix run vs first - mortar that has spent 4 hours on the wagon was much smoother and less watery. Link to comment Share on other sites More sharing options...
Brickie Posted September 1, 2019 Share Posted September 1, 2019 You’ll also see,when people have resorted to using washing up liquid instead of the real deal,pitted mortar deteriorating within a few years. And you know the hoddy was patting himself on the back as the compliments rolled in for his ‘lovely creamy mix.’ 1 Link to comment Share on other sites More sharing options...
Mr Punter Posted September 1, 2019 Share Posted September 1, 2019 I prefer hydrated lime to plasticiser. Link to comment Share on other sites More sharing options...
Oz07 Posted September 1, 2019 Share Posted September 1, 2019 That optimix is good but still not that clear on amounts. Between 5-10ml per 50kg cement. So that's max 5ml a bag, 2.5ml per mixer full. I squeeze bit into top then just put a tiny dash into bucket of water swish round before mixer. I understood plasticiser in right amount improves frost resistance as the air voids prevent frost attack like an airated block. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted September 5, 2019 Author Share Posted September 5, 2019 On 01/09/2019 at 20:47, Mr Punter said: I prefer hydrated lime to plasticiser. Does it also promote air entrapment in a mixed mortar or just change its consistency without air bubbles? Link to comment Share on other sites More sharing options...
epsilonGreedy Posted September 5, 2019 Author Share Posted September 5, 2019 On 01/09/2019 at 19:24, Declan52 said: To get a good motar the secret is just to let it mix and mix and mix. If you just lash water in till it looks right but not properly mixed then it dries out to quick. Lot of wisdom in that advice, I must be more patient. Anyone care to offer a minimum mixing duration? Link to comment Share on other sites More sharing options...
Mr Punter Posted September 5, 2019 Share Posted September 5, 2019 1 hour ago, epsilonGreedy said: Does it also promote air entrapment in a mixed mortar or just change its consistency without air bubbles? No but it does apparently help the mortar heal small cracks over its lifetime. Link to comment Share on other sites More sharing options...
Declan52 Posted September 5, 2019 Share Posted September 5, 2019 1 hour ago, epsilonGreedy said: Lot of wisdom in that advice, I must be more patient. Anyone care to offer a minimum mixing duration? It will take as long as it will take. Just get all the sand cement and water in quick then walk away and let it mix. Go and stack blocks or clean up just Don't stand and stare into the mixer like your watching TV. It will never mix with you watching it. Link to comment Share on other sites More sharing options...
joe90 Posted September 5, 2019 Share Posted September 5, 2019 I used to think my builder was wasting my electricity running the mixer fir ages with mortar in it but he explained the mix was a lot better after along mix. Link to comment Share on other sites More sharing options...
Vijay Posted September 5, 2019 Share Posted September 5, 2019 6 hours ago, Declan52 said: It will take as long as it will take. Just get all the sand cement and water in quick then walk away and let it mix. Go and stack blocks or clean up just Don't stand and stare into the mixer like your watching TV. It will never mix with you watching it. What's the min you would let it mix for 10, 20 minutes? Link to comment Share on other sites More sharing options...
Declan52 Posted September 5, 2019 Share Posted September 5, 2019 6 minutes ago, Vijay said: What's the min you would let it mix for 10, 20 minutes? It will depend on the size of the mixer for a start. A small belle mixer that just about fills a barrow will be 5 mins of mixing once it's filled. Then you have a proper site mixer that will fill maybe 5 barrows at least then your up to maybe 10-15 mins. It will all depend on things like how wet the sand is and how quick you are at getting the sand and cement into the mixer. Then it will all come to experience. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted September 5, 2019 Author Share Posted September 5, 2019 7 hours ago, Declan52 said: It will never mix with you watching it. How did you hack into my site security camera? Link to comment Share on other sites More sharing options...
epsilonGreedy Posted September 5, 2019 Author Share Posted September 5, 2019 1 hour ago, Declan52 said: It will depend on the size of the mixer for a start. A small belle mixer that just about fills a barrow will be 5 mins of mixing once it's filled. Mine is a middle sized electric Belle, a 150 litres I think. 1 hour ago, Declan52 said: Then it will all come to experience. My visible que for a good mix is when the mortar develops a reptilian looking surface as the drum turns which I take to mean a decent amount of air churned into the mix. Link to comment Share on other sites More sharing options...
Mr Punter Posted September 5, 2019 Share Posted September 5, 2019 5 minutes is OK. Depending on temperature you could leave it mixing for an hour or two. Link to comment Share on other sites More sharing options...
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