WICKES FROST PROOFER AND RAPID HARDENER

[newuser1]

Hello,

I am having an extension built and I have noticed that my builder has used this rapid hardener in the mortar mix for the walls due to the cold weather.

I wanted to know if this is an acceptable practice and whether there are negative effects of this on the brick/blocks/walls?

Many thanks in advance for the help and advice.

 

[xdave]

The Wickes admixture is one of a whole bunch of similar products which basically just replace some of the water with some clever chemical witchcraftery which increases the speed of the cement reaction so most of the water will have gone by the time night falls . That reduces the chance of it freezing and blowing the mortar or weakening the chemical bonds. Some of them claim to improve the cured characteristics (strength, etc) of the mortar and none claim to reduce them so I would worry about it.

However some rapid set admixtures are not suitable for use with embedded metals because the contained calcium chloride reacts with them and causes corrosion and it is mentioned in the Wickes data sheet for their product. I'm not sure if that restriction applies to stainless steel wall ties though as they may resist it.

 

[newuser1]

Thanks xdave,

Having looked on the product it states not recommended to use with embedded metals...I assume that could mean wall ties also.

I also checked the mortar and it still soft and hasn't set from yesterday so the stuff hasn't worked anyway.

My only real concern is longevity of the mortar and effects on the wall ties due to the additive and also the cold weather...

Is it worth me getting him to redo the wall or am I just worrying for no reason...I am spending a lot of money on the extension and I don't want to have issues in the future for myself or if I ever sell for the new buyers from poor workmanship.

 

[xdave]

I'm not sure if it applies to all embedded metals - if the ties are stainless then it might not affect them. Unless you have any calcium chloride to hand to test if they corrode then only the manufacturer of the wall ties can tell you that. You could probably mix some sodium chloride with water and test as the reactions will likely be similar. Some stainless grades are more susceptable to rusting in the presense of chloride salts, and I suspect most wall ties are a fairly low grade for cost reasons which will rust eventually anyway, but I don't know the chemistry as the mortar cures with these products and whether the added risk is removed quickly or extends for some time afterwards.

The rapid hardening admixture will only increase the intial cure (by up to 2/3rds if dosed correctly) the full cure with any cement will still take many days/weeks for the chemical bonds to form. In cold temperatures it will still take some time. Has the wall been pointed yet (assuming it will be visible?) as that will help to provide a hard external edge.

FWIW (which I know is very little when you are the one paying for it) - I have seen hardener used by a regional house builder when knocking up houses with wall ties and whilst I don't know if it was calcium chloride based it would appear to be quite a commonly done thing when the temperatures fall.

Others may be along with first hand experience and suggestions on what you should do, but if it was my extension I would raise my concern with the builder and ask his opinion, but phrase it so as not to lead the answer. e.g. "Is it ok to use this Wickes hardener admixture with wall ties?" and then ask why it is not ok to use it with rebar reinforced concrete. If they seem to give competant answers as to why one might be ok but not the other then I would not worry too much.

[ edit ]
BTW - how cold is cold? If the temps are falling below freezing the mortar will still need to be covered. These admixtures mitigate the risk of freezing damage to the chemical bonds but they do not remove it completely.

 

[newuser1]

Thanks xdave,

By sodium chloride you mean I can use normal salt to test?

I have asked the builder unfortunately his not too technical in these matters he just uses it to speed up the process.

The other thing puzzles me is that these wall ties are quite small things how much bearing they have on the structure of the building? need an engineer I suppose to explain?

Also I see in the old properties with double walls, there is a small cavity but no wall ties are present and these houses have been up for nearly 100 years...and with modern building materials I would hope the structures are much better whether with wall ties or not...

So I may just be worrying about nothing....but I suppose I am just trying to make sure my investment in my property would last a fair amount of time and not have problems prematurely.

I will try the sodium test to see what happens to the wall ties.

Once again many thanks for your help and advice.