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Re: Masonry Question

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This seems odd to me.

Type M mortar has the strongest compressive strength at a 28 day
strength of 2900 psi, minimum.  While Type S mortar has a compressive
strength of 2100 psi, minimum.

The mix ratios for the different types are as follows:
Type M: 1 Portland Cement, 1/4 Lime, 3.5 Sand
Type S: 1 Portland Cement, 1/2 Lime, 4.5 Sand
Type N: 1 Portland Cement, 1 Lime, 6 Sand
Type O: 1 Portland Cement, 2 Lime, 9 Sand

Mortar Types for Classes of Construction are:

Type M : Masonry subjected to high compressive loads, severe frost
action, or high lateral loads from earth pressures, hurricane winds, or
earthquakes. Structures below or against grade such as retaining walls, etc. 

Type S: Structures requiring high flexural bond strength, and subject to
compressive and lateral loads.

Type N: General use in above grade masonry. Residential basement construction 
 interior walls and partitions.  Masonry veneer and non-structural masonry 

Type O: Non-loadbearing walls and partitions.  Solid load bearing masonry 
with an actual compressive strength not exceeding 100 psi and not subject 
to weathering.

All of this is from James Amrhein's book Reinforced Masonry Engineering 

It looks to me like Type M is what you want and Type S is going backward.

Hope that helps,

On 3 Jun 2014 at 16:42, Tarek Mokhtar wrote:

> A plan checker wants me to change the mortar I am using for a little
> retaining wall from type M to type S. It has been a while since I
> delved into masonry specs, is their something I am missing? -- Tarek
> Mokhtar, SE
> ----------------------------------------------------------------------

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