The inspector assigned to watch the aggregate application should be positioned to have a good view of the aggregate as it leaves the discharge hopper. There should be a thin “curtain” of aggregate dropping through the gates. The curtain should be uniform across the entire width of the discharge hopper. The curtain of aggregate should be only one aggregate particle thick, and light should be easily seen through the curtain. Any dark streams suggest a gate is open too wide. Any unusually light streak means not enough aggregate is being released. If the aggregate appears to be stacking as it is placed on the asphalt, it is being applied too heavily.

The scalping grate on top of the discharge hopper should also be visually checked. There should be a steady flow of aggregate passing through it. An accumulation of clay balls, grass, or rocks on top of the grate indicates that the loader operator is picking up contaminants. This problem should be corrected immediately.

Behind the spreader, the pavement surface should be checked for contaminants and streaking of thin or thick rows of aggregates. If there is evidence of thick and thin alternating streaks running transversely (a ripple effect), it indicates that the spreader speed is too high.