Question

7.4 What is your recommendation for the maximum size of coarse aggregate for the following situation? A continuously reinforced concrete pavement cross-section contains a layer of 19-mm reinforcing bars at 150 mm. centers, such that the steel is just above mid-depth of a 250 mm. thick slab. Cover over the top of the steel is therefore about 100 mm.

Answer 1

Given Data:

• Pavement Thickness : 250mm
• 19mm bar 150mm c/c
• Cover over the top : 100mm

Solution: Recommend Coarse aggregate size for concrete mix

• Aggregate in any particular mix of concrete are selected for their durability, strength, workability and ability to receive finishes.
• Aggregate are divided into either coarse or fine category.
• Most common size of aggregate used in pavement construction is 20mm in dia.
• For the 19mm bar spacing 150mm center, the 20mm aggregate size suit for this pavement construction as well.
• 20mm size of aggregate provide very durable concrete mix which is provided very good bond strength with the bar and having very good compressive strength for required load transfer to the soil.
• Larger size of aggregate reduce the quality of cement and water needed.
• 20mm dia coarse aggregate recommend for this pavement concrete mix.