huangyhg

diamond grinding of newly laid concrete slabs
i am looking at the option of specifying diamond grinding for a newly laid concrete slab surface. the alternative is to put down a screed on the slab, but this extends the construction programme. the screed will then require time to 'dry' to recieve the intended finishes.
i read somewhere that 'diamond grinding' is quicker and cheaper and yet have never seen it being used with newly laid concrete floors. the grinding is supposed to remove the 'softer concrete and laitance' at the slab surface exposing the much stronger concrete below. it is also suppose to give a better finish and level tolerance on the slab.
any expert views on the subject please?
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can't believe that this is quicker or cheaper than laying a screed (especially pourable self-levelling screeds). if you're grinding the top surface of the concrete then you will have a massive dust problem which will take an eternity to clean up.
if you are grinding, then to get a flat finish will require extremely good workmanship to prevent low spots forming under excessive grinding action. as aggregate is exposed it will tend to be chipped out of the cement matrix leaving pit marks.
this is just my opinion and is not based on experience of grinding floors (but have used sanders on timber floors - the problems would be similar i suppose).
andy machon


grinding will only work best when concrete has hardened past 28 days, thus time delays. cost will be more than wet finish. quality may not be as desired vs. the wet finish surface.
suqlain...ginger is right. not cheap and results variable.
i would prefer to specify and dense concrete, good compressive strength for the application, tight flatness specification, and tight finish specification. if you do this and enforce it, you should receive a very good surface without the laitance and softness you mention. laitance and "softness" of the surface are anomalies that result from poor mix control and/or poor finish techniques. they should not be accepted as the norm, with remediation required by diamond grinding.
grinding a floor slab is not cheaper than the original floor finishing operation. i have used a terrazzo grinder on floors as a repair method to fix problems like carbonization and to remove floor sealers and paint. it works great for that (better and safer than chemical removal), but the floors were basicly flat. a terrazzo grinder would take forever if the floor had any sizeable humps in it. shot blasting will also clean up a floor, but leaves the floor pretty rough. the best method, as outlined above by others, is a good, hard steel troweled finish followed by an appropriate liquid hardener or sealer.

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