wetting the bricks

[david s]

There has been some recent discussion on another thread regarding the benefits of wetting the firebricks prior to laying them. It seems that the topic was discussed, but the thread is old and difficult to relocate. So here is my two cents worth.

The porosity of firebricks can vary considerably. It is a function of the degree of vitrification. The more vitrified the bricks are the less porous they will be. Vitrification is controlled by silica content, fluxes present and temperature the bricks are fired to. Out of interest I tested the porosity of my firebricks and was surprised to find that they were the same porosity as the solid reds that I also have. House bricks are generally more vitrified and therefore more waterproof so they don't allow too much moisture into the house from the weather.

Regarding the slow curing of the mortar, I would agree that this is a good thing to aim for, as anything made from portland cement will benefit from increased strength if kept moist, but commercial builders never bother because it is not particularly practical to try to keep masonry, or render for that matter, damp. The bricks should not be so soaked that they are wet or the mortar will not adhere well.

This explains it in in more detail
http://www.lmcc.com/concrete_news/03...d_strength.asp

[david s]

Re: wetting the bricks

"Good start to a discussion, the link is broke...

Anyway, onwards.
I cant see the benefit of soaking the bricks, if the bricks are sucking the life out of the mortar then the mortar is at fault, not the bricks, adjust the mortar to suit the bricks and the weather conditions.

The last thing you need to be doing is adding more water to the oven which has to be evaporated out one way or another in the curing process." Brickie in Oz


I disagree with your first point because to achieve the maximum strength from the cement and the hydration process it requires adequate water. Adding more water to the mortar will only achieve this to a small extent. A dry porous fire brick will quickly wick away a small amount of extra water in the mortar. Because fire bricks are usually far more porous than a house brick, they easily wick away that required moisture. I find it hard to believe that your formal training as a bricklayer would not have included the effects of moisture content and porosity of bricks, or perhaps you were self trained. There appears to be a mountain of evidence to support the extended curing of Portland cement to increase strength.

Regarding your second point, I agree. Adding water to the bricks does mean that it will have to be removed, however if it means getting a slow cure in the mortar resulting in a stronger bond, I think that it is a fair trade off.

[Bacterium]

Re: wetting the bricks

I wet them as it gives me a chance to wiggle the brick around and make sure the mortar gets into every nook and cranny.........otherwise the moisture sucks out pretty quick and you cant move them around or it breaks the bond if you do.....or it disturbs the one next to it.

Sure wetting the mortar more would give a similar result (to a degree) but not being a brickie means working with sloppier mortar which I struggle with.

[oasiscdm]

Re: wetting the bricks

Ditto Damon I agree

David thanks for moving the discussion.

[stonecutter]

Re: wetting the bricks

...if it means getting a slow cure in the mortar resulting in a stronger bond, I think that it is a fair trade off.

This is the point that should dictate the methods for mortar use. Knowing what to do and when is the real trick, since materials, conditions, and applications are different not only project to project, but day to day.
Also, adding too much water to mortar or concrete is just as bad as letting it flash dry.

Generally, a properly hydrated mix that has cured a longer and slower makes for superior mortar or concrete.

[Bacterium]

Re: wetting the bricks

OK, I started into this so I'll keep going..........I might sound like I'm about to swing the other way here

I can see the point brickie in OZ was making about getting your mortar right. Last year I was chatting to "Tradee" (local brickie) and watching his techniques. For example very efficient in picking up the spoil (or "snots") from the brick just laid and dropping it where the next brick goes. Whereas I'm always moving mortar back and forwards to the pile. Which probably also dries it out somewhat etc. etc.

They don't really wet down bricks unless its like hot summer (which our climate is dry heat here) and if they do they might just give certain types a squirt (eg. more porous rather than glazed shiny looking ones).

Also to give my view context.........this time round I'm using Hi Temp mortar so that's the angle I'm coming from .....can't say I've used poor mans mix and be able to compare. I did notice there was an area in my current build (about 4 bricks in one spot) where I know I didn't soak them and there is a hairline crack below. Not sure if this was too dry or I just bumped them at the point where they were adhering.

[Bacterium]

Re: wetting the bricks

Just been typing as you responded stonecutter...... agreed its the conditions and not too wet and not too dry.

[Tscarborough]

Re: wetting the bricks

If you study the standards and specifications for masonry you will find that there is a large amount of leeway in how mortar is to be prepared and used. This is because of the large amount of variability in masonry units and the aggregates used in the mortar, NOT the cement itself.

Soaking bricks is called for in several instances, one being an extremely porous brick and the other in extreme weather conditions of heat and wind. In neither case are the brick soaked to the point of saturation.

In laying brick, if they are saturated you will get a very poor bond as the water contained in the brick plus the water in the mortar will create a bond-breaking film (that is what allows you to slide the brick around). You can wet the brick, but the water in the mortar needs to be sucked into the brick for proper bond.

It is better to have a slightly wet mortar than a wet brick almost every time.

[brickie in oz]

Re: wetting the bricks

For example very efficient in picking up the spoil (or "snots") from the brick just laid and dropping it where the next brick goes.

The mortar that squeezes out should be used for the next perpend, it saves dipping into the mortar on the board all day, saves time and your back.

Watch a real pro lay.

[brickie in oz]

Re: wetting the bricks

"Good start to a discussion, the link is broke...

Anyway, onwards.
I cant see the benefit of soaking the bricks, if the bricks are sucking the life out of the mortar then the mortar is at fault, not the bricks, adjust the mortar to suit the bricks and the weather conditions.

The last thing you need to be doing is adding more water to the oven which has to be evaporated out one way or another in the curing process." Brickie in Oz


I disagree with your first point because to achieve the maximum strength from the cement and the hydration process it requires adequate water. Adding more water to the mortar will only achieve this to a small extent. A dry porous fire brick will quickly wick away a small amount of extra water in the mortar. Because fire bricks are usually far more porous than a house brick, they easily wick away that required moisture. I find it hard to believe that your formal training as a bricklayer would not have included the effects of moisture content and porosity of bricks, or perhaps you were self trained. There appears to be a mountain of evidence to support the extended curing of Portland cement to increase strength.

Regarding your second point, I agree. Adding water to the bricks does mean that it will have to be removed, however if it means getting a slow cure in the mortar resulting in a stronger bond, I think that it is a fair trade off.

I deleted the post as I could see by your reply that you were mounting a witch hunt for me and my views on why not to wet bricks.
The copying and pasting into your post of my original reply (which I deleted) proves my point.
I will now add you the ignore list.

[david s]

Re: wetting the bricks

I deleted the post as I could see by your reply that you were mounting a witch hunt for me and my views on why not to wet bricks.
The copying and pasting into your post of my original reply proves my point.
I will now add you the ignore list.

Allan, i'm sorry you feel that way. I quoted your post as my reply depended on it and would not have made much sense without it.
Not a witch hunt, just information that hopefully can be useful to other builders.

[tonybaker]

Re: wetting the bricks

hey guys, keep things simple, remember the first ovens were made of mud! Surely it is easy enough to have just damp bricks and use a squirty bottle if necessary. Soaking them would seem to me to be overkill, the water has to get out somehow? For the newbie builder, sloppy mortar is quite difficult to handle, so a drier mix is easier to work with.

[david s]

Re: wetting the bricks

You are correct Tony. Note that in my first post I said that
"The bricks should not be so soaked that they are wet or the mortar will not adhere well."

[sandgroper]

Re: wetting the bricks

1. Dampen bricks only to create mechanical connection

2. The more water used in mortar by volume the more shrinkage occurs causing cracking

3. The more loam or clay in aggregate used in mortar the more shrinkage

4. Non-hydraulic lime may slow the setting rate

5. mix only what you need as cement mortar doesnt retemper once its life is passed. It causes cracking weakens the mortar.