A mix with a higher percentage of rock has the advantage of:

• A. Being less expensive.
• B. It increases durability
• C. Harder to place
• D. Prone to cracking

Answer: (A)

When you design a concrete mix, the cement portion is the most expensive part, while the aggregate (rock) is relatively inexpensive. Increasing the proportion of rock means more of the concrete’s volume is filled with aggregate and less with cement paste. Since you’re replacing costly cement with cheaper rock, the overall cost per cubic yard goes down. This is the main practical advantage of a mix with a higher rock content. Of course, changing the ratio can affect placement, strength, and durability, but the cost reduction is the primary reason this approach is advantageous.