ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 351

FIGURE 9.25 California kneading

compactor.

reheated while still in the mold; then a compression machine is used to apply
a static force to level the face of the specimen.
The Superpave gyratory compactor is used for the Superpave mix design,
whereas the Marshall hammer and the California kneading compactor are
used for the Marshall and Hveem methods of mix design, respectively. The
Superpave gyratory compactor produces specimens 150 mm in diameter and
95 mm to 115 mm high, allowing the use of aggregates with a maximum size of
more than 25 mm (1 in.). Specimens prepared with both Marshall and Califor-
nia kneading compactors, as well as some gyratory compactors, are typically
101.6 mm (4 in.) in diameter and 63.5 mm (2.5 in.) high.

■ 9.9.2 Density and Voids Analysis

It is important to understand the density and voids analysis of compacted as-
phalt mixtures for both mix design and construction control. Regardless of
the method used, the mix design is a process to determine the volume of as-
phalt binder and aggregates required to produce a mixture with the desired
properties. However, since volumes are difficult and not practical to mea-
sure, weights are used instead; the specific gravity is used to convert from
weight to volume. Figure 9.26 shows that the asphalt mixture consists of ag-
gregates, asphalt binder, and air voids. Note that a portion of the asphalt is
absorbed by aggregate particles. Three important parameters commonly used