When using portland cement on an exterior, what is the proper ratio of cement to sand?

When using portland cement on an exterior, what is the proper ratio of cement to sand?

• A. 3:1
• B. 4:1
• C. 5:1
• D. 7:1

Answer: (A)

When you mix Portland cement for exterior work, the ratio of cement to sand determines how strong the mortar will be and how well it will bond to the surface. A three-to-one cement-to-sand mix uses enough cement to give good strength and a solid bond to the exterior substrate, while the sand provides bulk, workability, and helps control shrinkage as it cures. This balance helps the finished surface resist weather, cracking, and abrasion. Ratios with more cement, like four-to-one, five-to-one, or seven-to-one, become progressively stiffer and harder to work with and can increase brittleness and shrinkage cracks, which is not ideal for exterior conditions. Ratios with more sand (less cement) would be weaker and slower to gain strength, also not ideal for exterior applications where durability matters. So the three-to-one mix is chosen for a practical balance of strength, bonding, and workability.

When you mix Portland cement for exterior work, the ratio of cement to sand determines how strong the mortar will be and how well it will bond to the surface. A three-to-one cement-to-sand mix uses enough cement to give good strength and a solid bond to the exterior substrate, while the sand provides bulk, workability, and helps control shrinkage as it cures. This balance helps the finished surface resist weather, cracking, and abrasion.

Ratios with more cement, like four-to-one, five-to-one, or seven-to-one, become progressively stiffer and harder to work with and can increase brittleness and shrinkage cracks, which is not ideal for exterior conditions. Ratios with more sand (less cement) would be weaker and slower to gain strength, also not ideal for exterior applications where durability matters. So the three-to-one mix is chosen for a practical balance of strength, bonding, and workability.