[Rex Mann]

The sand used under pavers is to be 1 to 1 1/2 inches thick. It is also commonly called concrete sand. Do not use mason sand. If this type of sand is used, then you are likely to have movement and shifting.

Efflorescence is a natural process for all concrete products. There are ways to minimize it, but not eliminate it. Screenings have over 12% fines passing the # 200 sieve. Fines hold moisture. Moisture facilitates the efflorescence process.

When I took my first ICPI class it dispelled many of the same "wives-tales" I had about why we did or did not do things a certain way.

If you ever have the opportunity to attend an ICPI class, or better yet, sponsor one at your place, take it. And, if you do sponsor one I would be happy to come back east and teach it.

Peace,

Rex Mann

[Stonehenge]

Ok - I have an update - we may get to the construction of this test patio tomorrow. As I re-read this thread, it sounds like we want:

Geotextile under each test area

Hollandstone, running bond pattern.

1 test pavement with just our usual screenings as base

1 test pavement with 3/4-, 1" bedding sand (coarse concrete sand)

1 test pavement with just sand (?)

Each test area will be excavated to the same depth (8-9" below the top of the pavers).

Each area will be compacted in equal lifts of stone (or sand for the all sand prep), an equal number of times.

Each prepped area will be compacted with a Wacker 1550 vibratory compactor.

The same joint sand will be used across each pavement (no polymeric or organic binders will be used, to allow water to pass into the base to further test it's stability).

The same edge restraint will be used for each of the three sections.

Ok - I think I have everything down. Unless someone has something they think should be changed, we will tackle this project sometime this week, possibly tomorrow. It will be photographed and videotaped.

We will continue to test the pavement periodically during the season, by applying water to the pavement then subjecting it to loads. Measurements of deformation of both bond lines and base prep will be taken.

I haven't decided how I will make this information available. Seeing as we're incurring some costs to run these tests, I may opt to post the results in the Private Gardens.

[BJR]

I can't believe that you are all having this debate.

We, as an industry, had this discussion about 20 years ago in Australia.

We all use sand under our pavers as detailed by your ICPI method. Our standards were put out by the Clay and Masonry Segmental Paving Association. I will see if I can find a link to post.

Nearly every aspect of our construction has an Australian Standard or Industry Standard that you have to work to.

If not you may loose your licence to operate.

[Stonehenge]

There are some here, myself included, that do not believe sand to be the answer to a stable base. I'm of the opinion that the sand aids in fast installation, but not stability. But I'm open to new ideas and discussion, which is why I want to conduct these tests.

I hope that in those 20 years you've also continued to test and modify your procedures to make things even better today than they were 20 years ago. I'd be interested to hear what changes have come since then.

Have a great day,

Jeff

[BJR]

I have found that the basic design I use for segmental paving is superb. In all of the thousand os sq metres of pavers that I have laid with a compacted sub-base of what we call 20mmDGB (Road Base the same base used when constructing roads), this varies in thickness depending on traffic use, and the bedding layer of 30mm concreting sand, I have never had a failed job. That I know of.

I have however had failures when using different techniques.

One was a job for a local council that decided to construct a road deviation to stop drag racing along a straight stretch of road. The base was concrete, and then 30mm of concreting sand to lay the pavers on. I had my concerns from the beginning, because I have noticed on previous jobs that when passing the plate over the pavers laid on sand on a concrete base that the first pass beds the pavers in and the second pass actually loosens the pavers. I concluded that the concrete base did not absorb the vibrations as well as the road base. From then on I only passed the plate over the pavers once.

My concerns for this job were founded when the paving started to fail. It became loose and moved around, thus opening the joints. I repaired it 3 times without success. The Council finally lifted the paving and concreted the area.

Also back in my younger days there was a contractor who constructed his pavements with a fine road base. He would compact a 100mm (4in) layer first then place a thin loose layer on top to lay the pavers in. His finishes were never as even as other contractors and the jobs on steep drives always seemed to move.

There are projects around here that are tens of thousants of square metres in size, one being at the Olympic site in Sydney and others on shipping terminals where large folk lifts and trucks weighing over 40 tonne work on the pavers 24 hours a day. All of these jobs are on a road base and sand bed. These pavements are still in good shape today.

That little bit of sand that comes into the joint from the bottom must to something to strengthen the pavement. It must strengthen the paver interlock more than the fine sand that we vibrate into the joints.

So if something ain't broke why fix it.

Sure I have improved my techniques over the years, like screeding to a sand line, IE making grooves in the sand at either side of the job and screeding to these. We call it freehand screeding. It comes in handy when screeding jobs such as rolling driveways. I have improved the way we do the little things, but the basic design always stays the same.

Who am I to question thousands of dollars and years of research by qualified technitions.

[Rex Mann]

BJR,

Australia has had many more physical scientific studies on paving stones then any other country in the world. I'm positive your installation techniques have come about from Dr. Brian Shackel's work in this area. I would not hesitate to say he is one of the most respected people in our industry.

I once had the pleasure of hearing him speak at a seminar.
Then I was able to sit at his table during lunch. What a day!

He told a story of a simple lab test he conducted on vertical lockup.

I'll try to explain it the best I can.

They, him and some of his students, constructed a 1.5meter X 1.5 meter box using 2x4 lumber. It looked like a band, not a cube. they used one piece per side.

Next the put in 4x8's in a 90 degree herringbone while the 2x4 band was on the ground.

Next, they lifted up the box with a hoist to waist level.

They proceeded to hammer pavers out one at a time in preselected locations. Like the game "Don't Break The Ice"

After 5 pavers were removed the whole thing came crashing down.

For the second test they swept concrete sand, jointing sand, into the pavers from the top only.

Next they did the same thing. Using the same location of the pavers as they had in the first run.

This time 13 pavers were removed until it failed.

Then he went on to explain why he got the results he got in both scientific and layman's terms. He was not some old timer or piece of literature telling me to use concrete sand with no way to back it up. He tested his theory in the lab getting the same results time-after-time.

I was sold on using sand before I ever met him, however now I knew why I was using sand. The ICPI was about 2-years old when this happened. They were still getting tech-specs and classes in place.

Check out Dr. Shackel's web site.



http://www.brianshackel.com


Peace,

Rex

[Stonehenge]

I'll certainly have to check out that site. Thanks for the link, Rex.

Though the vertical lock of joint sand has a role, I have more of an interest in what goes below the pavers for the moment. If this test was similar to the game 'don't break the ice', it doesn't really address the base prep. I'm sure Dr. Shackel addresses it with other tests and other texts, but this test does not seem to apply to the question of base prep.

In any case, to your point, BJR...Who are you to question engineers who design specs for this work? Who, indeed. By your own statements you laid thousands and thousands of square meters of pavers - I think that makes you uniquely qualified. I guess having grown up with a PE in Mechanical (my father), married to a Chemical Eng with a Master's, and taking two years worth of engineering courses myself I'm a bit less mystified by engineers and their methods. What's more, I recognize that they are subject to many, if not more, of the same human character flaws as the rest of us, making their word (the PhD's, that is) not gospel, but the word of someone with a few more years of schooling, and a few less of practical experience. Which one is worth more? I guess it depends on the person.

I was in contact with the Civil Engineering department at my own alma mater last spring to get input on installing pavers over an asphaltic base. I was a bit surprised at some of the specs and information I received, thinking 'Jeez, I know more about this than this PhD does!' And this was someone that specialized in flexible pavements and taught this at the university level, at an engineering school that is among the top-ranked engineering schools in the Midwest (USA).

Am I saying I'm smarter than Dr. Shackel? Not at all. But I think that you do yourself a disservice to presume that you are simply the grunt labor, and they are the brains when it comes to hardscape design. I'm not fond of taking someone's word for something; I like to gather a bit of empirical evidence myself. So in running this test on this site, that's what I'm doing.

And then I'm sharing the results with everyone, that everyone might benefit. We may well end up singing the praise of the ICPI, Rex and Paul, and now you, BJR. But I want to see for myself before I start warming up my voice.

And I don't have any interest in any particular outcome - I just want us to be doing things the best way we know how. I've wanted to do this myself for awhile, now I get the chance to show everyone the results.

[BJR]

I, by no means seel myself short. I also started mechanical engineering at University and have recently found out that I have an IQ of around 150. Pretty unbelievable.

But I believe that the way I lay pavers is the correct way.

I am not quite sure exactly how you prepare your base and what you lay your pavers on. I believe that the entire pavement has to be flexible. I do not like the laying of pavers on sand over concrete on heavy vehicular traficed areas. I believe that they should be glued down, with suitable construction joints.

The way we prepare our base is to compact the ground first. Then a layer of road base is spread in 100mm layers and compacted to a standard specified for the project. In larger projects we actually have the compaction rate tested. Then we screed the concrete sand bed. Lay the pavers with a 2-3mm joint. edging is varied depending on the job. Then the pavers are straightened and a fine rendering sand is swept into the joints and a layer just enough to cover the pavers is left on. This must be powder dry. Then a vibrating plate with a urethane mat is passed over the pavers twice in overlapping runs. The sand is then swept off.

I have tried many different ways of doin paving, including one ignorant attempt to lay them into wet concrete. I was young and thought I knew better.

I always came back to the above method.

150! I can't even spell properly.

Still, I guess there has to be something in my big boof head.

[Stonehenge]

You didn't take one of the online IQ tests, did you?

Anyway, my process is very similar to yours. We're porbably doing something like 2-3" lifts of stone, instead of 4" (approx 100 mm). For pedestrian pavements we use the screenings pictured in the other thread, vehicular, or on less stable ground we always use some 3/4"-. No sand bed course - I like the screenings better - firmer, easier to lay the pavers, allows for more adjustment in seams/bond lines if you need it. We sweep in dry, bagged sand over the top and compact. We do this twice.

[BJR]

BUGGER

Don't tell me that IQ test results from 'I'm Smarter Than You.com' aren't accurate.

[Stonehenge]

[Stonehenge]

Here are a couple links that are full of good info:

http://www.buildcore.com/pdf/inte11se.pdf

http://www.countymaterials.com/ - for this link, click on the link to their e-Tek manuals. Lots of good stuff there.


Enjoy!

[AZTLANLC]

Please don't forget about this project and keep us posted.

[Stonehenge]

AZTLANLC, check out this thread for some follow up: How the forced failure phase 1 test was conducted