differences in concrete properties using 10mm to 20mm aggregate 3

[flyingdebris]

hi all,

what is the difference in concrete properties whether a 10mm or 20mm aggregate is used?

 

[Ron]

Depending on the mix design, either can be used to make essentially any range of concrete strengths.

When you use a smaller aggregate, such as the 10mm as your nominal coarse aggregate size, the specific surface area of the total volume of coarse aggregate is much higher than for the 20mm aggregate. This means that your mix will require more cement, more water and more fine aggregate in order to provide adequate paste coverage of the coarse aggregate and fill the high number of voids, even though the voids will be smaller in volume.

In response to this higher cement and water demand for the same water-cement ratio, you will experience more volumetric shrinkage from the mix from both drying shrinkage and from autogenous shrinkage. This means you will have to pay more attention to the timing and placement of control joints so that you mitigate the increased cracking potential.

 

[flyingdebris]

This makes perfect sense. Thanks Ron

 

[BigH]

and you will also develop a higher heat of hydration due to the additional cement

 

[Ron]

Thanks BigH....I forgot to mention that aspect.
As usual, you bail me out!!

 

[flyingdebris]

Great work guys. Thanks again

 

[BigH]

Ron - as you know, on a mass concrete dam, that is always our worry - the heat of hydration and density of concrete - not so much regarding strength except on spillways