Shear Capacity of 1916 Mortar
Shear Capacity of 1916 Mortar
(OP)
In an existing brick wall of some 14 inches thick minimum,
is there a rational guide to determine the probable shear capacity of the mortar present? Is there a small compression test that can be applied to the mortar in place?
This is in an urban environment that probably had reasonably up to date practice as established at that time. So can information be developed that would be satisfactory to a Building Department?
is there a rational guide to determine the probable shear capacity of the mortar present? Is there a small compression test that can be applied to the mortar in place?
This is in an urban environment that probably had reasonably up to date practice as established at that time. So can information be developed that would be satisfactory to a Building Department?






RE: Shear Capacity of 1916 Mortar
I've checked Amrhein's 4th Edition of "Reinforced Masonry Engineering Handbook" and "Masonry Structures, Behavior and Design" by Drysdale, Hamid, & Baker. Amrhein gives a few allowable shear and tension values for different mortar types. The other authors give a range for ultimate tensile strength of "mortar." However, neither book addresses old mortar.
Anyone have any applicable information?
RE: Shear Capacity of 1916 Mortar
I do recommend some form of strength test however. (We have cut sections of demo'd wall to do so) Progressive demolition of areas within the building have shown that the interior wythes of the wall were laid with a different mortar than that of the outer wythe. Depending on how your floors and roof are connected to the walls, this could pose a problem for you.
Assume the worst because most of the mortar becomes way too brittle. Also, reduce the dead load in your calculations accordingly.
RE: Shear Capacity of 1916 Mortar
RE: Shear Capacity of 1916 Mortar
RE: Shear Capacity of 1916 Mortar
Maybe consider an insitu test using a small flat jack in the mortar joints as per this link:
http://www.ana-usa.com/flatjack.htm
HTH
RE: Shear Capacity of 1916 Mortar
I've only just received the book, so I have only skimmed it so far, but it seems worth the money to me!
RE: Shear Capacity of 1916 Mortar
RE: Shear Capacity of 1916 Mortar
The pure limes used today have no impurities to act as a hydraulic agent and require masonry cement or Portland Cement to achieve this. In early times, it is the impurities in the base material used for making the lime that provide the hydraulic properties required for a lasting mortar.
In early times (generally predating the 1900's), the skilled mason generally knew the sources of the limes used and which provided a better finished product. Although he may not have known about what specific impurities performed better than others, he was trained in the use of certain products. Because the sources of lime and the skills of the mason varied, there is a real 'scatter' in the strengths of mortar, how well it bonded, and how well it lasted.
The lime in some mortars lacking hydraulic impurities has dissolved leaving only a weak sand matrix while others have developed nearly the strength of the stone material used.
There is no manner to determine the strength, except by testing. The actual strengths vary from approximately 20psi to several hundred psi.
I've been involved in a fair amount of restoration work. If you post your eMail address to me: dikcoates@alpha.to, I'll send you a paper I've prepared on Historic Brickwork (not complete, yet, I want to include Terra Cotta and some other stuff). If you're re-doing a brick wall you may have to concern yourself with the porosity of the mortar (to wick moisture from within the building because of no vapour barrier) as well as ensuring that the strength of patching mortar is less than that of the brick (for durability).
RE: Shear Capacity of 1916 Mortar
My e-mail is revank@msn.com
Cannot seem to get your address to work with me.