What type of mortar should I use? 1

[skirj]

I'm looking to build a temperature sensing instrument that sits atop a mortar platform in between high and low tide on the ocean. This block of mortar will be regularly prone to wave energy and must be able to withstand constant wave forces up to ~100psi. It also must be fairly resistant to erosion and any effects of saltwater. I was thinking ASTM Type S would be appropriate, but are there any experts who have suggestions on specific brands or other types? Thanks!

 

[dik]

Why mortar and not concrete?

 

[skirj]

I'm looking for a material that has a similar thermal conductivity to granite but is more cost effective to use than granite itself. A materials scientist recommended mortar because of this factor. Does concrete have a similar thermal conductivity to granite too? I wouldn't imagine it would be that different.

 

[dik]

Concrete can be batched from light-weight to dense to provide a thermal conductivity of from 0.1 to 2.5 W/(m-K). Where does your granite or mortar fit. You should be able to come up with something similar. You might check with your materials guy again.

Dik

 

[rconner]

There is a great book that delves significantly into the subject of mortars and concretes for aggressive service e.g. marine exposures now in several editions entitled, "The Chemistry of Cement and Concrete", by Frederick M. Lea et al. [I believe you will find Lea at some juncture hints that it may not necessarily be the particular Type of cement that has great(est) influence on same but instead the "quality" of its construction e.g. high cement content, high density/good consolidation, and low initially placed water/cement ratio etc., resulting in high strength and low permeability etc.

 

[Ron]

If you will have wave action and wetting and drying cycles, mortar does not have the durability you need. As Dik notes, you can design the concrete mix for essentially any properties you want; however, durability will be your most significant concern. To achieve durability, you'll need a much higher strength than mortar will provide.