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Are bricks and mortar safe to use as edging for vegetable gardens?

 
Travis Philp
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I have a modest pile of broken bricks that I picked up from a house that was under renovation.

It's grey bricks, longer than the typical red type, and was used in the basement. Not sure about the mortar. Does anyone know if its safe, or if it'll leach toxics into the soil?
 
John Polk
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Cement and mortar are very alkaline (limestone being the base).  Leaching would be a very slow process (unless you pulverized it).  I would be reluctant to use it around blueberries, or other acid loving plants, but otherwise, I see no problem.
 
Dale Hodgins
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Brenda Groth
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prunus and pear trees love rubble..so they would work well around those type of plants..avoid blueberries or other acid lovers
 
Ken Peavey
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Bricks
sure, go ahead
The overwhelming majority of bricks you would have access to from residential and commercial construction or demolition sites will be clay.  The vitrification process by which they are made pretty much locks the material together.  It would take decades for the bricks to begin to show signs of weathering.  You would get more disintegration as a result of frost than anything else, and all this does is break up the brick.  In these clay bricks there is no real concern for contamination of soil.  Colors are dependent on the type of clay used and any additives, commonly a mineral pigment. 

There are some types of specialty brick which you may find, but this would be infrequent, and you may not find them in a lifetime of rummaging through bricks from homes.  Firebrick, for example, is rarely used, and when installed right will outlast the structure.  As with clay bricks, these have been fired to extreme temperatures which binds the material together.  What seperates fire brick from clay is the water problem-firebrick HATES water.  Water and heat together can result in the bricks crumbling rapidly.  Also, firebrick are designed to withstand heat rather than serve a structural purpose.  They can crumble in just a few years if, say, used to pave a driveway.  The material you would find in firebrick used in structures serving the general population would include alumina and silica.  There would be no effect when involved with soil, although there is a camp which claims negative effects from aluminum exposure, with Alzheimers at the top of the list of potential problems.

In an industrial setting, the types of bricks are quite diverse.  There are firebricks of course, insulators, carbon brick (black like a hole in the world), ruby brick, big bricks that weigh half a pound, and chromium bricks that weigh a ton.  Paul Wheaton would likely enjoy the cast iron brick!  While some of these brick can be harmful, it is important to realize they are designed for a purpose, and that purpose is often to control or contain some pretty noxious stuff.  What that stuff is and what it would do for you strawberry patch may not be known to the people doing the demolition.  Avoid this stuff completely is the best advise.  Chances are you'll never see these in your life as environmental concerns dictate the disposal methods of some of this stuff.

Mortar
Mortar ingredients are along the same lines as far as general public vs industrial.  Sand and portland cement is what will comprise pretty much all the mortar you would find.  Industrial mortar is another story.  Some of that stuff is pretty bad.  I've worked with hexavalent chromium mortars-they are a beautiful bright green but you'll want to wear some personal protective equipment!  Different requirements demand a solution, and you still have the contaminants from whatever process the mortar and bricks serve.

Sand and portland mortars are fairly uninteresting.  You've seen ivy growing up the sides of buildings.  I'm sure you have grown a bed of tulips right beside the house and it's brick foundation.  The only concern is when the bricks are broken up, and mortar remains on the brick, and this is used in a garden situation.  Weathering will be much faster on the mortar than on the brick.  The mortar is able to break up into smaller pieces in just a few years.  The cement is made with lime, and this will reduce the acidity of your soil.  The effect is slow and of low intensity.  Nonetheless, some plants could show some  negative response.  To counter the effect, you could mulch with a high acid material such as pine needles. 

Creosote
Old fireplaces can have creosote built up.  The most common reason is burning conifer wood at a low temperature.  The resins in the pine/spruce/fir does not fully combust.  As the smoke rises, these resins condensate on the brick of the chimney.  This is not the same as the much more toxic creosote wood preservative product used on such things as railroad ties-thats a petroleum based product.  As for the old chimney, there would not be too much build up or the chances of a chimney fire may have destroyed the structure.  Then again, maybe thats why the brick is being reclaimed!  Smash one of these bricks in half.  You will observe the black edge facing in to the flu will be just that-a thin line of black.  If the black has penetrated more than an 8th of an inch, it was probably not well fired.  If that be the case, the brick would likely crumble in a few years. 

Flu liners for chimneys started to come into more regular use shortly after WWII, and would be of different composition than the clay bricks.  Where a flu liner was used, the brick would be well protected from creosote build up.  Also, after WWII, the use of heating oil became the standard for new construction, replacing wood as a primary fuel. 

You can use creosoted bricks in a fire pit.  Get a good raging fire going, there is a good chance the stuff will burn off.  Do it a few times if you like.  When the material is burned off, a layer of ash would be the only thing remaining. 
 
John Polk
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Plaster of Paris is another type of mortar (which is comprised of gypsum).  Plaster of Paris is used as the binder in making tofu, so should not pose any threat to a garden.
 
Tyler Ludens
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John Polk wrote:
Plaster of Paris is used as the binder in making tofu



Gross!  I thought Tofu was made from soybeans and nothing else except some bacteria. 
 
gani et se
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No added bacteria in Tofu, and good tofu uses magnesium chloride (also called nigari) as a curdling agent. Calcium sulfate can be used.
Tempeh on the other hand is inoculated with mold. 

H Ludi Tyler wrote:

Gross!  I thought Tofu was made from soybeans and nothing else except some bacteria. 
 
Benjamin Burchall
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Location: Long Beach, CA
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John Polk wrote:
Plaster of Paris is another type of mortar (which is comprised of gypsum).  Plaster of Paris is used as the binder in making tofu, so should not pose any threat to a garden.


Yup! Tofu is made with soybeans turned into soymilk which is coagulated with

A salt like:
- gypsum for Chinese tofu,
- magnesium chloride for Japanese tofu,
- magnesium sulfate which is epsom salt)

or

An acid like:
- lemon juice,
- vinegar,
- Glucono delta-lactone

I used epsom salt when I used to make it.
 
Tyler Ludens
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Ok, thanks.

 
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