concrete sand or screenings?

Discussion in 'Landscape Architecture and Design' started by cody, Jan 31, 2002.

  1. cody

    cody LawnSite Member
    from 6
    Posts: 20

    hey fellas.I 've got a good one for you.We do a good amount of hardscaping here in s.e. Pennsylvania and I've seen alot of guys use screenings (stone cinders) instead of concrete sand.OK my question is why?We primarily use E.P. Henry and they really push sand.Am i missing some benefit to the screenings?Thanks for your help.
     
  2. Lanelle

    Lanelle LawnSite Bronze Member
    Posts: 1,361

    For interlocking concrete pavers, ICPI standards call for washed concrete sand. Screenings can break down over time and cause failure. I'll step aside now and let the rest at this one.
     
  3. cody

    cody LawnSite Member
    from 6
    Posts: 20

    Thanks Lanelle for the responce.We're on the same page.

    OK one more .
    A big problem I find is finding and keeping dry sand.
    Any suggestions?
     
  4. PAPS

    PAPS LawnSite Senior Member
    Posts: 404

    We've used stone dust for years and never had any problems with it yet.
     
  5. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Posts: 1,712

    Somebody is going to have to explain hard to convince me how stone particles break down faster than sand particles. Sounds like hokum to me.

    I've used both and love stone dust. My observation is a more stabil base eslily compacted and worked. The larger angular particles tend to fit together well and the sand particles tend to roll around. Just walk on the two while your working and see the difference under foot.

    We also went against convention and used less base than many for walks and patios. A 3" layer of stone dust over top landscape fabric did it for us. NO problems. The fabric is essential as it keeps fine soil below from co-mingling with the larger base over a period of time.
     
  6. Stonehenge

    Stonehenge LawnSite Bronze Member
    from Midwest
    Posts: 1,277

    Run a search for the thread 'patio base'...it says it all.

    I'd say more, but my brain is mush and my eyeballs have given out on me - website updating bonanza....
     
  7. Turfdude

    Turfdude LawnSite Bronze Member
    Posts: 1,900

    Sound to me like a lot of you guys in the SE Penn area/ South Jersey area would benefit from attending the EP HENRY MidAtlantic Hardscaping Trade Shows Feb 13-19 at the South Jersey Expo Center in Pennsauken. See what these guys have to say and get ICPI Certified!!

    BTW, even though I do not get into paver installation, I believe it goes Fabric, modified stone (quarry blend) added in 2" lifts and compacted (this is the most essential step as the base must be stable and the ground can't "pump"), then not more than 1" of sand 3/4" recommended, followed by the concrete paver.

    Again , I'm no expert, but you can go to www.ephenry.com and see what they have to say, or register fr their show!!

    Bob
     
  8. Rex Mann

    Rex Mann LawnSite Senior Member
    Posts: 621

    Only benefit to screenings is less ingredents in the recipe. The sand is used as a bedding layer. The purpose is to keep the pavers from shifing side-to-side. When you compact the pavers into this bedding layer you should be accomplising 2 things. The first is setting the pavers into the bedding layer. When I say into I mean they must make an indent into the material. The next task which should be accomplised is the bedding material forced up in between the pavers. When laying a tight pattern, a 90 degree herringbone, the screenings are to large to push up through the pavers. The bedding layer should allow water to effectively and effeciently drain through. Sand meets this criteria. Screenings do not.

    We repair about 2 projects a year orginaly installed by other contractors. They always have screenings under them. We remove the screenings, which by the way is like concrete to remove. Then use concrete sand. I find inexperianced installers using screenings because they are trying to save labor and materials.

    Also, always a must to use filter fabric under your base.


    Rex
     
  9. diginahole

    diginahole LawnSite Member
    Posts: 249

    Well I know this has been debated in depth before but I didn't pipe in on that thread. I'll take this opportunity to add my two cents.

    Bedding sand should be sharp and have symetrical particles not flat or elongated. Flat particles (found in most limestone screenings) do not compact completely and will settle unevenly over time.

    Locally, limestone screenings have a lot of very fine particles (passing the no. 200 screen test). Very fine particles cause an aggregate to hold water. Water lubricates the aggregate and causes rutting and uneven settlement.

    Limestone is very soft and makes for great landscape boulders. This is because it is weathered so easily with time and water. Limestone dissolves in water. It doesn't just erode it actually dissolves. The sand we have locally is much harder than limestone and therefore more suitable for constructing pavement bases. Softer materials may pulverize into finer particles under load and cause water retention. A quick test for hardness: if the larger sand particles cannot be scratched or brocken with a pocket knife then the sand is generally hard enough for pavement bases.

    A suitable bedding sand will be a coarse multi-grained sand with 0% ( or very close to zero) passing the No. 200 sieve. The fines are the most important factor in choosing a bedding sand. Bedding sand should conforn to ASTM C33- gradation for bedding sand OR CSA standard A231.1. Any quarry will be able to provide you with a current sieve analysis to compare to the standard.

    In case you are interested the standard for base material is ASTM C2940. This standard allows up to 8% passing No 200 sieve.

    Note: water will not pass through a NO. 200 sieve.
     
  10. diginahole

    diginahole LawnSite Member
    Posts: 249

    Geotextile fabric may be used in areas where soils are saturated. While not necessary in all applications, it can delay deformation of the base from loads. Fabric is particularily useful over fine soils such as clays and silts. They prevent soil from being pressed into the aggregate base, espcially when saturated.
     

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