Increasing the amount of sand in a concrete usually decreases the amount of water needed to make the concrete workable.

• A. True
• B. False
• C. Sometimes true
• D. Not related

Answer: (B)

More sand increases water demand. When you add more fine aggregate, you raise the total surface area of the solids that water must wet and coat. That extra surface area creates more friction and capillary effects between particles, making the mix stiffer if water stays the same. To achieve the same level of workability (slump), you typically need more water or a chemical modifier to reduce water demand. So the idea that adding sand would decrease the amount of water needed to make the concrete workable is not correct.