I would appreciate some expert advice regarding a commercial concrete driveway we had installed about 30 months ago. It meant to be 32MPa (although we suspect it was not) – what results would we expect from core testing IF the concrete had been 32MPa?
Refer to the chart between compressive strength in MPa Vs age of concrete pavement.
Generally, the standard grade of concrete will gain a 16% strength on the first day, Remaining 40% in after 3 days and 90% after 14 days, and almost 90% after 28 days. And with an increase in time the rate of hydration decrease decreases which increases the strength with time Show us the strength of concrete pavement increases after 2 years.
Compressive strength Vs Age of concrete:
We know about the strength of concrete strongly depends on the gel to space ratio.
It has general application since the amount of gel present in the cement paste at any time is itself a function of age and time of cement as well.
Different type of cement requires a different time for the production of the same quantity of gel. Generally, find the strength characteristic of contract at its 28 days and some other properties of concrete as well often referred to the 28 days strength.
Actually, there is no scientific reason behind the choice of the age of 28 days it is simply that early cement gained strength slowly and slowly and hence it was necessary to paste the strength of the description on concrete in which significant hydration of cement had already taken place.
The particular choice of arm number of weeks was in all likelihood made so that testing like placing, would fall on a working day. In modern Portland Cements, the rate of hydration is much greater than in the past, both because they have a much higher fineness and higher amount of c3s content in it.
This is not necessary that in the case with all blended Cement It is obviously arguable that a shorter period than 28 days could be used for characterization of the strength but the age of 28 days since to have acquired it and a good position.
That pose compliance with the specification is almost invariably laid down in terms of 28 days strength.
If for some reason the 28 days strength is Rum estimated from the strength the determined at an early age as 7 days then the relationship between the 28 days strength and the seven days restaurant has to been established experimentally for the given mix proportion.
For this reason, various expressions for the ratio of two strengths are no longer thought to be reliable.
I hope so your doubt is clear. thank you.
It is increasing with its age.
Concrete strength does depend on its age. Because of its whole life, the hydration(hardening) process goes on. So the strength of concrete is increasing through its life
But after 28 days the hydration process is restarted at a very significant low level; so you notice very less increase in strength after 28 days.
But this hydration phenomenon is only acceptable for the concrete, which is pure. No shrinkage, creep is accrued to concrete.
The concrete strength is all dependent on the fraction, which is hydrated. All strength comes from these hydrated fractions only. And the fraction hydrated is increasing all its life as below graph.
And here is the strength development in cementicious materials