When discussing how hard or soft concrete is to grind, many people confuse HARDNESS and STRENGTH. Strength is measured in MPa and is a measure of compressive strength. It is true that high compressive strength can be harder, but not always.
This is because the aggregate and sand in high MPa concrete are likely to be the same in low MPa concrete. The difference is in the amount of cement and water (slump). This is also why 40MPa concrete from the batching plant is not 40MPa when placed, if the contractor adds water; it could just as easily be 15MPa.
When we talk about hardness (to grind) it really is all about the kind of dust that is produced during the process.
This tends to produce ultra-fine, talcum powder-fine dust. This dust is very unabrasive; it does not wear the matrix of the diamond segment sufficiently. The result is that the diamond grit soon becomes hardly exposed so it grinds even finer, powdery dust; the segment ceases to grind, and the segments may even get hot and glaze over. (‘Exposed’ means; how much diamond grit is poking out of the segment.)
This can occur where there has been water damaged through the addition of extra water to the mix before discharging from the truck or rain damaged. It produces very soft, gritty, sandy, dust. This is too aggressive for most discs the dust may be abrasive and grind too well, open up the diamond segment too much and causing fast wear.
If you are unsure about hard or soft concrete, contact Con-Treat today. We can advise you on the best option for your needs.
* The above information is to be used as a guide only and Con-Treat accepts no responsibility for any consequence resulting from the advice contained herein or verbally.