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Posted: Sat Mar 12, 2016 7:17 am
by KAMIKAZEE DIY
Is it correct that a salty air environment can cause damage to exposed mortars and concretes?
Why does this happen, and, what measures can be taken to fight the problem?
Cheers
Posted: Sat Mar 12, 2016 7:45 am
by lutonlagerlout
salt water is corrosive
most houses near coastlines are rendered and painted
mate worked in jersey a while back everything there is painted
LLL
Posted: Sat Mar 12, 2016 9:39 am
by seanandruby
Make sure any crumbling brickwork and joints are made good to stop salt getting in, paint timber and metalwork etc; regularly. Clean off any efflorescence with a stiff brush and a cleaner P&A
will advise more on that . I wouldn't seal brickwork as that could seal in the salts use sulfate resistent material below ground ie cement. Must keep up with general maintenance most of all.
Posted: Sat Mar 12, 2016 12:59 pm
by Brucieboy
As LLL says, corrosion to steel reinforcement in concrete is the biggest problem. This is dealt with in great detail in BS 8500 - the UK concrete standard. Specifiers must use this document to ensure the concrete is fit for purpose depending the exposure conditions. Added to the strength class of the concrete should be an attaching XS class - exposure (X) of reinforced concrete to chlorides from sea water (S):
XS1 - exposed to airborne salt but not in direct contact with sea water
XS2 - permanently submerged
XS3 - Tidal / splash and spray zones
For each XS class, there is a multitude of strength classes, cement types, minimum cement contents and maximum water/cement ratios depending on the cover (in mm) to reinforcement and intended working life (50 years or 100 years).
When an XS class is specified, the concrete producer will know what mix has to be batched although there is often lots of dialogue with the specifier / contractor beforehand as they rarely give the cover or intended working life with the enquiry / specification documents.
Unreinforced concrete is less onerous when exposed to sea water, with an XAS class being specified, again with various strength classes, cement types etc.
One of the problems with salt (chloride etc) is it's hygroscopic - it will suck more water into the pore structure of the concrete which then increases the potential for freezing resulting in a greater risk of spalling at the surface. The amount of spalling depends of the quality / grade of the concrete.
Posted: Sat Mar 12, 2016 11:57 pm
by KAMIKAZEE DIY
Thanks guys for taking time to reply.
Was hoping someone would suggest something I could add to mix that would fight salty environment.
So, I guess even the magical powers of SBR come off second best to salty environment and mother nature.
Problem is a rubble wall that was built maybe ten years ago and mortar work is starting to detiriorate , going to rermove old mortar and repoint.
Cheers
Posted: Sun Mar 13, 2016 1:14 am
by Brucieboy
SBR in your mortar will certainly help to improve its general durability and resistance to the effects of a salty environment by reducing the permeability, i.e. it will be more dense / less porous. If you're repointing, make sure you rake out a good depth and thoroughly brush / wash out any residue otherwise it won't bond properly. It's generally recommended to pre-soak the wall before repointing to avoid moisture being sucked out too quickly from the mortar. Do a trial area first before you proceed full scale to get the hang of it.
Posted: Sun Mar 13, 2016 8:14 am
by seanandruby
I was thinking an SBR ad mixture to the compo'.
Posted: Sun Mar 13, 2016 9:32 am
by Brucieboy
Just a thought - depending on the height and width of the wall and whether it's retaining or not, be careful when removing the old mortar. Being made from rubble, the joints are unlikely to be of uniform depth and width as conventional brickwork so removing too much mortar in one go could affect the stability of the wall. If in doubt, seek professional advice.