Is Gravel Just Filler in Concrete? Many homeowners think gravel is just added to concrete to increase volume. But gravel is not just filler. Its size, cleanliness, shape, and grading can affect the strength, workability, and durability of concrete. In house construction, even the smallest material choices can affect the final result. That is why choosing the right gravel matters before concrete works begin. At WallPro Systems & Construction Inc., we help homeowners build with