[dan deutekom]

A while back there was a discussion about limestone screening vs sand. In our area Unilock will not honour thier warranty if limestone screenings are used because they claim it causes the pavers to disingrate. I have taken some pictures of old lockstone pulled from a 15 to 20 year old pathway that was layed on limestone. There never was any salt applied to this surface. Sorry for the picture quality but I only had my camera phone with me.

[4seasons]

did it eat away at them?

[dan deutekom]

Yes. Only the bottoms of the brick are totally eaten away. One of them has only 1/4 inch of good material left. I have seen this damage often on older installations but only if laid on limestone screenings.

[Matt Kulp]

So...I'm guessing the damage comes from the moisture retention from the screenings? Or, do they claim the Limestone breaks down the concrete over time? I have been told many reasons not to use the Limestone screenings, but this is the first I have heard about the breakdown aspect.

[alcland1]

This is good to know. I would think the lime stone had a chemical reaction and i would also say depending on the location of some quarries stone dust may have a % of lime in it. Would this be why ICPI wants us all to use mason sand?

[Matt Kulp]

Originally Posted by alcland1

This is good to know. I would think the lime stone had a chemical reaction and i would also say depending on the location of some quarries stone dust may have a % of lime in it. Would this be why ICPI wants us all to use mason sand?

Not mason sand, washed concrete sand. Mason sand is too fine for bedding. ICPI has always said no stone dust due to the moisture retention, but I have never heard of the corrosion issue as seen above.

[4seasons]

If you think about it aren't pavers and wall stone made the same? We don't use sand under our walls. Maybe unilock has a quality issue, or maybe all my walls are going to fail?

[eastern1]

Limestone will react with the brick but it takes many years. I've only seen it once or twice that bad in the last 25 yrs or so.