How does aggregate grading affect plaster performance?

• A. It has minimal impact
• B. Proper grading ensures uniform strength, reduces voids, and improves texture
• C. It only changes color
• D. It weakens the plaster

Answer: (B)

Aggregate grading controls how the sand and other particles fit together in the plaster mix. A well-graded aggregate pack tightly, filling the gaps between larger particles, which reduces voids and creates a denser, stronger plaster. That uniform packing leads to consistent strength throughout the layer, so it’s less prone to cracking as it dries. Reducing voids also helps the surface finish—less porosity means a more stable texture and a smoother, more predictable finish. Workability follows from the right balance of particle sizes too, so the plaster can be spread evenly without segregating. When grading is poor—too many fines or too many coarse particles—the mix can have voids, weak spots, and surface defects.