Aggregate Size vs Type of Element

[slickdeals]

Folks,
IS there a preference to use larger aggregates (3/4",1") on flexural members and use smaller aggregate (3/8") on compression members?

I have heard from senior people here in my office that you are better off using larger aggregates for flexural members (beams) because they offer better crack control?

Any thoughts?

 

[BAretired]

That's a new one on me.

BA

 

[Ron]

For relatively small, prismatic sections like beams and columns, the argument is theoretical and academic. Yes, larger aggregate promotes less shrinkage. The reason being is that with larger aggregate you have less surface area to be covered by the paste, thus the paste quantity can be smaller. A smaller paste quantity has less cement, thus less shrinkage.

The phenomenon is significant when you are dealing with large, flat areas such as floor slabs and pavements. For smaller prismatic members with reinforcement, it has little or no value for that purpose and can be detrimental if significant reinforcement is involved, since the larger aggregate can promote underconsolidation in tight areas.