Minimum Aggregate Size for Flatwork
Minimum Aggregate Size for Flatwork
(OP)
I have numerous school site projects in Southern California, that require new concrete flatwork. The specificatons, which I wrote, specify a mix design of compressive strength minimum 4000psi, W/C ratio 0.50 maximum, with 1 inch aggregate passing 95-100%. If it helps in this question, the specs are written per Green Book requirements for a mix design of 618-CLE-4000P.
The contractor has come back asking for a revised mix design that can be used in tight areas, inaccessible for a truck. His mix meets the compressive strength and W/C ratio requirements but his aggregate gradation passes a 3/8" size at 100%, or grade E per the Green Book. How much should the difference in aggregate size affect my decision on accepting this alternate mix design?
Thanks for the help - Canman
The contractor has come back asking for a revised mix design that can be used in tight areas, inaccessible for a truck. His mix meets the compressive strength and W/C ratio requirements but his aggregate gradation passes a 3/8" size at 100%, or grade E per the Green Book. How much should the difference in aggregate size affect my decision on accepting this alternate mix design?
Thanks for the help - Canman





RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
With a w/c ratio of 0.61 and a 3/8" coarse aggregate top size, this will be a high shrinkage mix. Further, because it has more cement in it, you will likely get faster setting times or at the least will get a very fast "end" set.
Your original mix design is much better for the application. There is no reason you can't pump a large aggregate mix. It is done every day. (but you can't do it with a 2" pump pulled behind a pick-up).
Stick to your guns and make them do it right.
RE: Minimum Aggregate Size for Flatwork
If the slab is only 4" thick, the 1" max aggregate seems large. Why not 3/4"?
RE: Minimum Aggregate Size for Flatwork
RE: Minimum Aggregate Size for Flatwork
Dik
RE: Minimum Aggregate Size for Flatwork
check this post...