Nhl in bedding mix - Nhl mortars better for the environment?

[Thehandmadegarden]

Been catching up on the site and reading one of Tony's latest pages http://www.pavingexpert.com/light_flags_01.htm
This got me thinking about the use of Natural Hydraulic Limes in place of OPC in the bedding mix. Would an NHL mix create fewer problems with staining? My method of laying is pretty much as per the site. I haven’t had any problems with staining myself, but I’m aware it does occur. I know some prefer higher strength mixes and much wetter mixes than I use. I like the idea that my paving can be more readily recycled when the time comes and we have the next fashion change.
I’ve fancied having a go with NHL mixes and probably looking to do a lime mortar course at some point. I’m attracted to the fact that lime mortars are more environmentally friendly, using less energy to produce and absorb CO2 as they mature.
Has anyone used lime mortars and do you have any advice on there use?

Clive
www.thehandmadegarden.com

[msh paving]

as far as i'm aware, lime mortar is not for use underground as it does not set hard,do you mean replacing the OPC with lime?,I personally can't see any good reason for doing it,others might see it in a different light MSH

[Brucieboy]

Hydraulic lime mortar is most commonly used for masonry purposes. However, if you're really interested in using it for paving, I'd suggest you contact either Singleton Birch or Hanson (Heidelberg) to obtain the opinions of their Technical Departments. It's possible NHL 5 might be suitable in certain situations but it's more expensive than a conventional sand/cement bedding mortar. The mix proportions are nearer 2:1 to 3:1 sand/NHL 5.

[Carberry]

As brucie has said as far as I am aware NHL5 is the absolute minimum but everything is much more expensive, materials as well as labour involved. I assume it would take too long to cure for most people to use too.
Mason's mortar
Table showing strength of lime mortar
Note the NHL 5 in a 1:2 mix only has a compressive strength of 2.2 after 28 days.

If you were interested in it though could phone the guys, or email the guys in the first link, they're the go to people in Edinburgh for buying lime, matching mortar etc

[seanandruby]

When i started out learning the trade 40 years ago, we only ever used lime to lay on and a lime slurry swept into the joints.

[Carberry]

When i started out learning the trade 40 years ago, we only ever used lime to lay on and a lime slurry swept into the joints.

Yeah, lime was the binder of choice back in roman times :laugh:

[lutonlagerlout]

I brought this question up some years ago on a coarse i did working with lime
they run a similar one now but it is only 1 day now,it was 3 days then
basically the tutor said " not really"
curing times are far too long for paving
when building walls with lime putty or plastering you are looking at at least a week of misting,covering and basic faffing about
this would be unacceptable for flag/slab laying
I think sean may have been talking about hydraulic lime which goes off a lot faster

maybe bruce will know but PFA or BFGG which are by products of heavy industry may be available and have greater green credentials
however cement,lime,pfa and bfgg all involve very high temperatures and a lot of energy to burn out the CO2

i think crushing existing concrete and paving and using it as type 1 is probably a greener way forward

cheers LLL
link for lime course

[Thehandmadegarden]

Thanks for the reply's guys

I recently had a play with NHL 5 ready mix mortar when I was doing some repairs to my roof (stone built house) I have a mate that's a manager on the canals and they use it for repairing the stone work on the locks. I've herd a lot of negative comments about the mortars being to slow to set, but it doesn't seem to have been a problem on my roof and on their locks, so I'm keen to learn more.

Carberry I use a cement stabilised mix to bed, so like the 1:10 mix described on this site. I know some like to glue their flags down. I like to be able to lift the flags in the future, clean them off and reuse. Much as we do with old Yorkstone. Nothing pisses me off more than lifting big old Yorkstone to spend hours hacking off the bedding. I'm not sure then how the compressive strength compares with the NHL figures and what that means practically to bedding mix.

Sean What type of lime did you use and what were the pros and cons?

LLL In theory you can lay flags on grit only so once pointed a slow cure shouldn't be a major problem. I lay on a moist mix so with care you can step on the flags as soon as they're knocked down. When I've seen the wetter mixes used and I wouldn't want to be on them till set. As I understand with Natural Hydraulic Limes is that the firing is a lower temp and they reabsorb CO2 as they mature, so better for the environment. Thanks for the link that's not far from me now

Clive

[lutonlagerlout]

sorry missed the hydraulic bit
yes hydraulic sets even under water,but i dont really want my cement costing a tenner a bag
and sorry clive
but i totally disagree with your opinion about making the flags easily liftable
IMHO if they arent fairly stuck down then any water ingress will result in movement upon freezing
I have never had any problems with picture framing wicking or movement using my wettish mix

and IME flags are rarely taken up and reused
when flags used to be 3-5 inches thick this made sense
but when laying flags at 20-25mm thick they are basically tiles
cheers LLL

[Brucieboy]

Hi Clive - to produce lime, it is generally burnt at lower temperatures than cement (typically 900 and 1400 degC respectively), however what you have to consider is the overall carbon footprint. During production, cement produces about 850 kg of carbon per tonne whereas as pfa (aka fly ash) is about 10 kg per tonne and ggbs about 50 kg per tonne - these figures will vary slightly from producer to producer. This is why the concrete industry is under increasing pressure to use these "greener" replacement materials. Pfa is used at typically 30% replacement (range 25 - 55%) and ggbs used at 50% (range 30 - 70%). For general concretes, ggbs usually produces the "greenest". However, transport also plays an important part in the overall "cradle to grave" determination of the total carbon footprint, e.g. the cement source may be 1 mile away from the plant whereas the pfa or ggbs source may be 200 miles.

With regard to lime, it's production carbon footprint is about 150 kg of carbon per tonne. For aggregate it's typically 5 - 10 kg of carbon per tonne. Again, both figures may vary slightly from producer to producer.

As I mentioned previously, speak to Singleton Birch. To my knowledge they are the only actual producer of natural hydraulic lime in the UK. They may supplement information given by users of the product (as suggested by Carberry).

[Carberry]

Thanks for the reply's guys

I recently had a play with NHL 5 ready mix mortar when I was doing some repairs to my roof (stone built house) I have a mate that's a manager on the canals and they use it for repairing the stone work on the locks. I've herd a lot of negative comments about the mortars being to slow to set, but it doesn't seem to have been a problem on my roof and on their locks, so I'm keen to learn more.

Carberry I use a cement stabilised mix to bed, so like the 1:10 mix described on this site. I know some like to glue their flags down. I like to be able to lift the flags in the future, clean them off and reuse. Much as we do with old Yorkstone. Nothing pisses me off more than lifting big old Yorkstone to spend hours hacking off the bedding. I'm not sure then how the compressive strength compares with the NHL figures and what that means practically to bedding mix.

Sean What type of lime did you use and what were the pros and cons?

LLL In theory you can lay flags on grit only so once pointed a slow cure shouldn't be a major problem. I lay on a moist mix so with care you can step on the flags as soon as they're knocked down. When I've seen the wetter mixes used and I wouldn't want to be on them till set. As I understand with Natural Hydraulic Limes is that the firing is a lower temp and they reabsorb CO2 as they mature, so better for the environment. Thanks for the link that's not far from me now

Clive

Strength wise a 10:1 mix is 7.5 after 28 days compared to 2.2 for lime.

I'm not sure what that translates in to in real terms though, would need to get my brother on the case.

I agree with you on using a weaker mix and being able to reuse the flags.

[Brucieboy]

ps Just had a right ribbing from the wife. She's had her coat on and off three times since 1 o/clock waiting to go out. Reckons I'm on a porn website and nothing to do with paving. I told her if she doesn't stop moaning I'm going to build a snowman in front of her car similar to the one posted by mickg on the Craic. See you later (assuming I get home in one piece)!!

[Thehandmadegarden]

uhhh I do love a meat on an answer!
Thanks guys for taking the time to give such detailed and informative answers. The Brew Cabin is still the place to come for the info

Clive
www.thehandmadegarden.com