Spalling of Limestone

[Geophffrey]

We used leuders limestone for our pool coping. I live in Texas where it can get to 105 for months with no rain.

4 months after our pool completion, our limestone started spalling. At that time we had freezing temps, which causes spalling. At this time I had a chlorine puck pool. After about a year I converted to a SWG. It’s gotten worse since the SWG, but I don’t know if that’s the cause.

I did not initially seal the coping, but once is started spalling I sealed it 3 times with stone tech salt water sealant.

The coping is getting worse and worse. I need to replace it.

I’m curious if sealing all sides of limestone before installing would work or if I need a new coping altogether? I’ve read about Oklahoma stone, but it doesn’t fit our pool look.

Please let me know if new limestone sealed would work or if I need new coping, what kind should I install?


I’ve attached pictures. The stuff in my pool is my coping. I’ve attached what the stone should look like and what it looks like now.

Thanks for your help.

 

[ajw22]

Not all "limestone" is of the same quality. Quality and price vary widely depending on the stone source. Buying stone that you don't know its source and other customers experience with it is a gamble.

A good builder knows the source of the stone that he uses and that it lasts with his customers.

A bad builder buys stone from the lowest cost source and hopes the customer does not come back with warranty claims.

A stone sealer does not make low quality stone last.

 

[JamesW]

The stone looks like very low quality stone.

You need really good stone from a reputable dealer.

The stone should be very hard and dense.

A scratch test is usually helpful.

If the stone scratches easily, it is low quality stone.

Contact NPT for a sample of their stone.

Go to a local stone supplier and ask to see their stone so that you can see it in person and do a scratch test.

Get a specification document that shows the properties like density, hardness etc.

NPTHardscapes_Brochure

view.flipdocs.com

https://www.nptpool.com/hardscapes/handcrafted-stone/

Stone Supply Austin TX | Landscape Supply | Decorative Stone

Find Everything from Patio Stones and Boulders to Decomposed Granite and Other Landscape Supply Products at Our Stone Yard Locations in Austin, TX. When it comes to quality stone and landscape supply products, one name stands out among the rest … Continue reading →

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Bedrock Stone & Design, Austin's premier rock yard

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[JamesW]

Make sure that the stone is high density.

Verify with the supplier.

You can even measure the density of your current and new stone by checking the weight and volume of a piece.

The volume can be checked using water in a measuring container.

Measure the volume with and without the stone to find the difference, which is the volume of the stone.

The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk.

The density correspondingly ranges from 1.5 to 2.7 g/cm3.

Although relatively soft, with a Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa.

For comparison, concrete typically has a crushing strength of about 40 MPa.

Limestone - Wikipedia

en.wikipedia.org

Limestone is divided into three (sub-classifications) based on their densities as listed below:

Low Density: Limestone with a density ranging from 110 to 135 lb/ft3 (1760 through 2160 Kg/M3).

Medium Density: Limestone having a density greater than 135 but not greater than 160 lb/ft3 (2160 to 2560 Kg/M3).

High Density: Limestone having a density greater than 160 lb/ft3 (2560 Kg/M3).

Limestone

Limestone is defined as a rock of sedimentary origin composed mainly of calcium carbonate or the double carbonate of calcium and magnesium, or a combination of both minerals. Re-crystallized limest…

eurostonemarble.com

 

[JamesW]

NPT provides Indiana Limestone, which is generally well regarded.

It might be classified as type II.

Type 3 is best but check with the supplier for the actual specifications and for their recommendations for and outdoor stone.

You also want a low absorption by weight %.

The higher the absorption, the faster the stone will generally deteriorate.

The worst stone is low density, absorbs a lot of water and is soft.

The best stone is high density, low absorption and very hard.

You should also review the actual stone before taking possession or delivery to verify all properties and color etc.

Delivery should come with a delivery sheet that specifies the stone type and properties.

As you can see, there are 3 types of classifications for limestone.

Type III is the best with the highest density and highest strength.

Most likely, you got type 1, which is a very cheap stone.

Type 1 will deteriorate much faster than type 2 or type 3.

Make sure that your new stone is type 2 or type 3.

https://www.indystone.com/pdf/gs-limestone-fact-sheet.pdf

Here is a supplier that lists the type of stone and they also offer samples.

You need a supplier that can provide these details.

Spec, Details & Testing - Vetter Stone | Alabama Stone

www.vetterstone.com

If your supplier cannot quickly and easily provide these details, then they are incompetent and you need to check with a different supplier.

The Use and Overuse of Testing in Specifying Dimension Limestone – Indiana Limestone Institute of America

iliai.com

Our Stone

We supply several varieties of premium quality European stone to architects, interior designers and craftsmen for a broad range of applications including limestone flooring, fireplaces, sculpture …

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Standard Specification for Limestone Dimension Stone

AbstractThis specification covers the material characteristics, physical requirements, and sampling method appropriate to the selection of limestone dimension stone for general building and structural purposes. Dimension limestone shall include stone that

www.astm.org

Density: 2684 kg/m3, 150 lbs/ft3 (approx. 13.33 ft3 / ton)
Absorption: 0.50 (per cent in 24 hours)
Compressive Strength: 341 MPa
Crushing Strength: 49.373 PSI
Traverse: 10.01 MPa
Strength: 1455 PSI

Country Estate Limestone - Bedrock Natural Stone

Density: 2684 kg/m3, 150 lbs/ft3 (approx. 13.33 ft3 / ton) Absorption: 0.50 (per cent in 24 hours) Compressive Strength: 341 MPa Crushing Strength: 49.373 PSI Traverse: 10.01 MPa Strength: 1455 PSI A full coloured stone available in Grey, Buff, or Full Colour. It's warm colours and strong clean...

bedrocknaturalstone.com

Testing Standards for Natural Stone: What They Are, Why They Matter - Coldspring

Building a beautiful structure that will stand the test of time is the goal of most projects. But when a stone’s physical properties take a back seat to design and aesthetics, how that structure will look in five or 10 years (and beyond) may not be as impressive as it looks immediately following...

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ABSORPTION AND BULK SPECIFIC GRAVITY TESTING OF DIMENSION STONE

ASTM C97 tests two critical natural stone properties: absorption by weight and density, or how “heavy” the stone is. C97 is one of the most important and widely used ASTM tests. The testing involves drying test specimens of the stone in a ventilated oven for 48 hours and then weighing them. The specimens are then submerged in water for 48 hours and weighed again. The absorption value, expressed as a percentage, is the difference between the dry weight and wet saturated weight.

Note the stone’s absorption value is based on its weight, not its volume. For example, two stones of the same volume may have different weights, because one is denser than the other. Assuming both stones absorb the same amount of water, the denser stone will have a lower absorption value than the lighter stone, since the volume of water absorbed will make up a smaller percentage of the total saturated weight. The Materials Specifications also prescribe minimum densities for natural stone.

In the final portion of C97 testing, a fine wire suspends the stone, and it is then weighed. Comparing the stone’s weight to the unit weight of water, its specific gravity is determined. Specific gravity then helps testers obtain its density, which is an important property to know particularly when designing support systems, for example. Natural stones’ specific gravities range from 2 to 3. For example, a stone with a specific gravity of 2.6 is 2.6 times heavier than water.

 

[JamesW]

I tried to pressure wash it and I wound up creating grooves in the leuders.

This indicates that the stone is probably low quality.

Easily damaged stone is typically lower quality.

Unless you used excessive pressure, the stone should not have been seriously damaged.

Pressure washing is typically not recommended for softer stones as it can damage the stone.

 

[JamesW]

I would cut out a few cubic pieces of the existing stone and sand the stones smooth and then:

1) Weigh it.

2) Allow it to dry.

3) Weight it again.

4) Find the volume.

5) Calculate the density.

6) Allow it to soak in water for 48 hours and weigh it again to find the absorption.

7) Measure the CSA (Cross sectional area) and then apply a compressive force until the pieces fails.

8) Divide the force required at failure by the CSA to find the compression strength.

 

[Geophffrey]

I would cut out a few cubic pieces of the existing stone and sand the stones smooth and then:

1) Weigh it.

2) Allow it to dry.

3) Weight it again.

4) Find the volume.

5) Calculate the density.

6) Allow it to soak in water for 48 hours and weigh it again to find the absorption.

7) Measure the CSA (Cross sectional area) and then apply a compressive force until the pieces fails.

8) Divide the force required at failure by the CSA to find the compression strength.

Wow James! Thank you so much for all of this information. I had no idea. Is there a specific type of stone I should be looking at? Or is a good quality limestone sufficient for a salt water pool?

 

[JamesW]

These numbers look good assuming they are accurate.

Density: 2684 kg/m3, 150 lbs/ft3 (approx. 13.33 ft3 / ton)
Absorption: 0.50 (per cent in 24 hours)
Compressive Strength: 341 MPa
Crushing Strength: 49.373 PSI
Traverse: 10.01 MPa
Strength: 1455 PSI

Maybe ask for a sample.

A type III limestone or maybe a quartzitic sandstone should do well.

Country Estate Limestone - Bedrock Natural Stone

Density: 2684 kg/m3, 150 lbs/ft3 (approx. 13.33 ft3 / ton) Absorption: 0.50 (per cent in 24 hours) Compressive Strength: 341 MPa Crushing Strength: 49.373 PSI Traverse: 10.01 MPa Strength: 1455 PSI A full coloured stone available in Grey, Buff, or Full Colour. It's warm colours and strong clean...

bedrocknaturalstone.com

 

[JamesW]

Check with NPT and some local dealers.

What color do you want?

 

[Geophffrey]

Check with NPT and some local dealers.

What color do you want?

James thank you so much for your help. Ideally a light gray stone. Is pre cast coping stronger than natural stone?

 

[JamesW]

Is pre cast coping stronger than natural stone?

You need to get the specs for each stone to check the properties like density, hardness, absorption, compressive strength etc.

Get a hard, dense stone with good compressive strength and low absorption

High absorption means that water easily penetrates the stone and this leads to stone failure if the water freezes and due to salts in the water.

 

[Geophffrey]

You need to get the specs for each stone to check the properties like density, hardness, absorption, compressive strength etc.

Get a hard, dense stone with good compressive strength and low absorption

High absorption means that water easily penetrates the stone and this leads to stone failure if the water freezes and due to salts in the water.

Thank you James. I’ll give NPT a call. I appreciate all of your information!

 

[JamesW]

NPT has precast coping as well.

Handcrafted Stone | Hardscapes Precast Coping | NPTpool.com

Precast Coping offers the look of natural stone as an easy-to-install. Precast Coping is also extremely durable and easy to maintain. For more Handcrafted Stone precast coping designs, Visit NPTpool.com

www.nptpool.com

Going to local stoneyards can be helpful because you can review the stones in person.

A good stoneyard will have datasheets on their stones and they should be able to advise about the suitability of the stones for use in your application.

Local shotcrete/gunite pool builders should also have some samples of different coping stones that you can check out.

Texas builders tend to think that SWGs destroy pool coping, so be ready to work around their beliefs without getting into an argument.

 

[Geophffrey]

NPT has precast coping as well.

Handcrafted Stone | Hardscapes Precast Coping | NPTpool.com

Precast Coping offers the look of natural stone as an easy-to-install. Precast Coping is also extremely durable and easy to maintain. For more Handcrafted Stone precast coping designs, Visit NPTpool.com

www.nptpool.com

Going to local stoneyards can be helpful because you can review the stones in person.

A good stoneyard will have datasheets on their stones and they should be able to advise about the suitability of the stones for use in your application.

Local shotcrete/gunite pool builders should also have some samples of different coping stones that you can check out.

Texas builders tend to think that SWGs destroy pool coping, so be ready to work around their beliefs without getting into an argument.

Definitely will do James. Thank you. And, you're right. Everyone I've spoken to already has said the issue is the salt in my pool and will not warranty any work they do unless I convert back to liquid chlorine or pucks....

 

[Newdude]

will not warranty any work they do unless I convert back to liquid chlorine

Sodium Hyperchlorite, huh ? Your season is loooooooooong and hot, and will use many jugs of sodium hyperchlorite. But call it bleach or chlorine and suddenly it doesn't damage stone like salt supposedly does.

It's OK. You aren't going to convince the ignorant, no matter how better an argument you have.

 

[Geophffrey]

Definitely will do James. Thank you. And, you're right. Everyone I've spoken to already has said the issue is the salt in my pool and will not warranty any work they do unless I convert back to liquid chlorine or pucks....

Hey @JamesW , how does this look to you?

 

[JamesW]

I would consider that to be a medium grade; not bad, but not the best either.

It is a travertine, which has a lot of holes, which I do not really like.

My preference is for a limestone that does not have the holes, but you have to choose whatever you like.

 

[Geophffrey]

Thank you James. They also have some pre cast coping that they recommended. I’ll see about the specs on that.

 

[JamesW]

Is that from NPT?

Ask about the limestone, not the travertine.

Maybe also consider the sandstone.

Have you seen the samples in person?