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Selitre expert?


Charli2011
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6 hours ago, CHILLIN said:

The only expert which seems to work is Sr. Dynamite! Try a broader search under efflorescence and rising damp. It is actually not as much a problem here as it is in many parts of Europe. The Europeans are the experts.

This product might be worth exploring and they show distributors in Mexico:

http://www.drytreat.com/

I am going to try this stuff.  The only thing that I can associate my salitre with is that it is near a stone exterior wall.  Am going to try the drytreat on the exterior wall now that the interior wall has been fixed (or at least attempted to be as only time will tell)

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The best solution is to remove wall plaster, let it dry a couple of days. Apply muriatic acid (1 part acid to 3 water) to the wall, allow it to dry. Apply another hand. Replaster leaving a 1 inch gap at the bottomn apply acid to the plastered wall. Let it dry, and paint. After each acid application you have to wash the wall will water.

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The salitre in the walls is one thing and the crappy river sand is another culprit.  The natural ocurring salt peter mixed with black dirt found in all the sand here causes unnecessary problems.  Why doesn't a company here sell washed pure sand for construction?  Wouldn't pure clean sand work a lot better than the dirty sand they bring you straight from the river banks?

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Salitre, as in Sal, as in salt, not Selitre.

Having lived in Mexico for about 16 years and been involved in construction here, my own and others, I can tell you that I have never found any "expert" on dealing effectively with this, although many seem to claim they to know the fix. NachoOE's advise is pretty good, but you really should apply a good quality "sin salitre" product before painting. Stuff they sell at Comex and Prisa doesn't seem to work, Home Depot sells Sika brand, which is good and I believe Fester also puts out a good product.

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P.S. My house was all built with unwashed river sand and I did not have a speck of salitre anywhere for 8 years until my french drain got plugged up a couple years ago and that is the only place I now have salitre. You can't get rid of it for long until you actually eliminate the source of the moisture.

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I will say that sand of poor quality will cause you problems.  You can have all your walls knocked out and have it filled back in with that river sand and much of it will be ok for a while, but unfortunately, in a few places within a month you may see small sections  or spots that are not fairing well, that are puckering up.  Even if that is on a wall that you know that there isn't any moisture problem.  True salitre takes time to build up.  Dirty sand you will see problems very soon.  Well, that is my experience and we have been building on our house and remodeling it for the past 6 years.  Sometimes the sand will have an over abundance of that salty saltpeter mixed in it or black dirt and with just a little natural occurring moisture it will melt out and bubble up within a month or so of repair.

Home Depot sells bags of premixed cement like we get NOB, has anybody ever tried that?  Or is that too brittle for walls?

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One problem is that people want to paint walls too soon after they have been built or repaired. Cement takes a long time to cure. If you paint too soon, the moisture has nowhere to evaporate and you seal it inside the wall behind the paint. I waited about 6 months to paint my walls after they were plastered, and like I said, no salitre anywhere after 9 years except where my french drain failed (and it was dirty river sand I can assure you). Also, they like to mix paint and sealer together for the sealer coat here. Don't let that be done! Sealer is designed to absorb into the plaster, paint sits on the surface. One coat of sealer after the plaster has cured for months, then 2 coats of high quality paint is the way to go.

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5 hours ago, mudgirl said:

I waited about 6 months to paint my walls after they were plastered, and like I said, no salitre anywhere after 9 years except where my french drain failed (and it was dirty river sand I can assure you). 

Does any company around sell clean washed sand, that will be free of saltpeter and black dirt?  I am sure there are methods of washing sand to remove the salts and dirt.  We gutted much of the inside of our house and have been allowing it to dry out for almost a year now, soon we will have the money to re-plaster it and paint it again, but where can we get washed sand?  Also, another technique I've heard about is mixing loose fiber glass fibers into the sand mixture, that is supposed to strengthen the walls. We will be trying that also.  We live next to the arroyo and we have serious salitre problems. We had to sacrifice parts of our garden and fill it in with cement sidewalks to cut down on the moisture.  When they mix cement NOB they don´t mix sand in it, they just poor the cement mixture from a bag and add water, and they don´t have salitre.  

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You need silica sand. It is not only the cleanliness of the sand, it is also how "sharp" it is. Portland cement is actually quite soft (around 600 p.s.i. for lower grades) so the strength and waterproofness depends on the aggregate used. The cement is just the glue which holds the aggregates in place, the aggregates lock together to do all the real work. The size of aggregates depends on the application - a sidewalk is different from a mortar or plaster. The concrete products which come out of the bag, are usually for things like fence posts and sidewalks - they have lots of pebbles in them.

Here is a company in Guadalajara which makes silica sand. I have no idea about delivery costs. If you do place an order let me know, I would like a few bags myself.

silica sand

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1 hour ago, CHILLIN said:

You need silica sand. It is not only the cleanliness of the sand, it is also how "sharp" it is. Portland cement is actually quite soft (around 600 p.s.i. for lower grades) so the strength and waterproofness depends on the aggregate used. The cement is just the glue which holds the aggregates in place, the aggregates lock together to do all the real work. The size of aggregates depends on the application - a sidewalk is different from a mortar or plaster. The concrete products which come out of the bag, are usually for things like fence posts and sidewalks - they have lots of pebbles in them.

Here is a company in Guadalajara which makes silica sand. I have no idea about delivery costs. If you do place an order let me know, I would like a few bags myself.

silica sand


Note that Chillin's advice only applies to new concrete, that's less than 7 days old.  

See how the official graph from years of testing of real cement (shown below) has Chillin's quoted '600 psi' for only about the first 4 days.

Then... by 7 days,  it's up to 2000 psi ....   3 times stronger than Chillin's claim of just '600 psi'

Why?   Gotta know some Chemistry:
When the correct amount of Portland cement is used,  the cement gets much stronger over time because it starts out with only tiny~small crystals formed when concrete is first hardening.   The crystal structure of cement in concrete continues to grow over time - interlinking the small crystals into bigger... and bigger ... and ultimately very STRONG big interlinked crystal structures:


curing_fig1.jpg?sfvrsn=2

Notice how the same concrete has really weak low Compressive strength for just the first week,  even though it has the same sand & gravel at 7 days as it has at 1 year.

Then notice that by 1 year ... the cement has strengthened from Chillin's claimed '600 psi'  ... and it can hard to 13 TIMES more strength ~8,000 psi~ by a year later of proper curing - due to the Portland cement crystals growing over time.

And YES,   adding salty sand, or dirty sand,  or smooth sand gives a weaker final product.

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Oh well - google is your friend. And this is a lot more complicated than he makes out -but, please, please don't add any more faux science. Do you have any clue what "proper curing" entails outside of a laboratory?

98% of the concrete here you can drive a nail into - so much for your theory.

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Just a warning! if you come across anyone who claims to have solved the problem...be careful.  We were told this new procedure was the best.  Little holes were drilled all along the wall. Then some gunk was put into the holes,ostensibly to form a barrier. Within 6 mos....all places affected again.   oh yes, they painted the inside of the house with outside paint.

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  • 1 year later...

There is no affordable cure, short of razing the structure and rebuilding.  Everything else is just a stop-gap measure to try to slow down the formation of salitre.  It is best to learn how to live with it, and how to scrape it, dig it, and re-plaster and re-paint it.  It is quite simple, but it is a nuisance in any masonry home built upon an absorbent foundation without any impermeable barrier between the foundation, walls and floors. The common use of incompletely washed sand does contribute unwanted minerals to all of the masonry products used in the construction and finishing.

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6 hours ago, Tiny said:

Has anyone heard of or had any experience with the company called Salitrex from Guadalajara?

Tiny, this company sounds like they have the European products. Call them for an appointment and estimate and come back here to let us know what they say. You might ask for Mexico references. It is a long existing problem looking for a cure.

https://translate.google.com.mx/translate?sl=es&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.salitrex.com.mx%2Fwp%2F&edit-text=&authuser=0

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14 hours ago, geeser said:

Tiny, this company sounds like they have the European products. Call them for an appointment and estimate and come back here to let us know what they say. You might ask for Mexico references. It is a long existing problem looking for a cure.

https://translate.google.com.mx/translate?sl=es&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.salitrex.com.mx%2Fwp%2F&edit-text=&authuser=0

They use a European product. They give a 15 year warranty. We have a quote from them. At first looking at the quote, it was a little shocking. Then I had to realize it was a quote for a complete job, from removing the top coat to the final painting. 

Our Mexican references are two engineers that work for construction companies in Guadalajara. One engineer worked with my wife and the other is my brother-in-law.

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  • 2 weeks later...

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