Low Compressive Strength
Low Compressive Strength
(OP)
I am getting low compressive strengths for my C40 concrete.i use cubes to test the strengths.my 3day M Pa is 30 but this is using 600kg/m3 of cement. to me this is a bad result.I should be acheiving that strength using about 400kg/m3 of cement.My w/c ratio is very low;.32-.35.I cant figure out what could be wrong.





RE: Low Compressive Strength
RE: Low Compressive Strength
thanks for the response but this is using 600kg/m3 of cement.According to other designs ive seen, one should obtain that strength from about 400kg/m3
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
Have you looked at the sampling, sample preparation, handling, curing and testing practices?
Also is there a possible problem with excessive of fines in the aggregates? This can increase the amount of water also.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Low Compressive Strength
20mm 680
10mm 425
quarry dust 249
water 190L
RE: Low Compressive Strength
I don't know what "quarry dust" means, but I suggest you have an insufficient quantity of correctly graded fine aggregate. I would expect more than twice that amount to adequately fill the space between the coarse aggregates.
With a properly graded mix, and competent aggregates, you should be able to produce 40 MPa concrete with 400 kg/m3 cement. Is this mix based on any design calculations, or it is just trial and error?
By the way, all your components, including the water, only add to 2144 kg/m3, which is very light.
RE: Low Compressive Strength
RE: Low Compressive Strength
sand 500
cement 600
Quarry dust(fines)249
water 190
20mm 680
10mm 425
At 400KG cement/m3 I am not getting the 40MPa results.The 3 day results I got which was 30MPa was using 600kg cement /m3. This should not be ...ok heres a question...would 30MPa after 3 days be a good result for C60 concrete then?
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
1.Dirty Material
2.Mix Design
3.Handling/Curing Practices
Thanks
RE: Low Compressive Strength
Quarry dust is the fines from the crusher in the quarry where the aggregates are being crushed. This a perfectly good replacement for sand, but should still have a reasonable grading. Try comparing your quarry dust gradings against a standard sand and see how thay compare (have you got a standard for quarry dust grading?)
RE: Low Compressive Strength
The cement suppliers in most countries probably have volumes of daily reports on the chemistry, fineness and performance. - Contact the concrete supplier or the cement supplier for a quick answer if it is a time-critical application.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Low Compressive Strength
RE: Low Compressive Strength
Quarry dust is more correctly referred to as crushed rock fines and maybe googling this will be helpful.
RE: Low Compressive Strength
RE: Low Compressive Strength
RE: Low Compressive Strength
I think dirty aggregates are the problem and also you need to look at the grading of the quarry dust (crushed rock fines)
But many years ago I worked in West Africa and the local cement could not produce 40MPa concrete at a reasonable cement content. We imported cement from Europe.