Mortar mix crumbles like dry dirt


I didn't have stucco mix and didn't want to make an extra trip to Home Depot so I patched a small area on my exterior stucco wall with mortar mix instead. After a few days I rub my hand across on the patched area and the mortar mix crumbles like dry dirt. Why is this stuff strong between bricks and no good on stucco surface? It is possible for the cement migrated to the bottom of the bag and all I had mixed was mostly sand?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jack wrote:

How old was that mortar mix and how was it stored? If moisture was allowed to get near it in storage, that is likely to cause it to fail.
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have lots of stuff laying around in storage so its properly old but it was a full bag. The mixture was nice and loose so it didn't seem like much moisture gotten in but don't know for sure.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That'd be your problem -- old mortar. It doesn't last long, and it doesn't take much moisture to ruin it.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Since you "didn't want to make an extra trip to Home Depot," can we safely assume that you used a bag of mortar mix you already had at home? An open bag?
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jack writes:

Old material, "struck" in the bag. Still looks dry and powdery in the bag, but the particles of portland cement have lost their chemical activity from slow moisture intrusion over time.
If you want to use old cement products, test them first before committing costly labor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Don Young
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Even brand new type N mortar is not as strong as type S. It is only intended to bond bricks together and not to stand on it's own. Type S has a lot more portland in it and sets up harder.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.