Sharp sand vs. building sand - why?

[inwood]

I note that many older properties were built using sharp sand with the aggregate exposed, which in my opinion looks much nicer.

Modern buildings however appear to be built using the finer building sand and have very flat looking mortar joints.

Is there a reason why one should use building instead of sharp sand and vica versa for a given situation?

 

[biffvernon]

Sharp sand, with it's gradation of grain sizes, gives a stronger mortar. Ideally the largest grains should touch each other, transferring the loads, while the smaller grains fill the spaces preventing the large grains from moving. The lime finishes the job by filling the tiny spaces with something solid.

With an Ordinary Portland Cement mortar, the cement is so strong that grain size distribution is less important, at least for general building work, and the individual grains may not even be touching each other. A soft sand, with small, even sized, rounded grains, makes for a mortar that is easily worked allowing the brickie to build up zillions of bricks per hour to produce ugly buildings quickly.

 

[Gervase]

A soft sand, with small, even sized, rounded grains, makes for a mortar that is easily worked allowing the brickie to build up zillions of bricks per hour to produce ugly buildings quickly.

I may be forced to steal that definition some time! :lol:

 

[Flyfisher]

Presumably, the practice of mixing sharp and soft sand for mortar is just to achieve a compromise between these two cases, or is there something else going on?

 

[biffvernon]

That reminds me of my windmiller friend complaining about a customer who said they made their bread with a mixture of white and wholemeal flour, "I go to the trouble of dressing white flour - if you wanted 70% extraction why didn't you say so?".

 

[inwood]

Thanks for that Biff a wonderfully concise answer!

 

[Penners]

allowing the brickie to build up zillions of bricks per hour to produce ugly buildings quickly.

Thank goodness for someone who can give a clear explanation without resorting to pejorative assertions.

You should consider a career in marketing, Biff.