AGGREGATES - Materials for Civil and Construction Engineers - page 165

(a) (b) (c)

(d) (e)

FIGURE 5.3 Particle shapes: (a) angular, (b) rounded, (c) flaky, (d) elon-
gated, and (e) flaky and elongated.

FIGURE 5.4 Angular and
rounded aggregates.

Figure 5.5. By determining the weight of the fine aggregate in the filled
cylinder of known volume, the void content can be calculated as the differ-
ence between the cylinder volume and the fine aggregate volume collected
in the cylinder. The volume of the fine aggregate is calculated by dividing
the weight of the fine aggregate by its bulk density. The higher the amount
of void content, the more angular and the rougher will be the surface texture
of the fine aggregate.

■ 5.5.2 Soundness and Durability

The ability of aggregate to withstand weathering is defined as soundness or
durability. Aggregates used in various civil engineering applications must be
sound and durable, particularly if the structure is subjected to severe cli-
matic conditions. Water freezing in the voids of aggregates generates stresses
that can fracture the stones. The soundness test (ASTM C88) simulates weath-
ering by soaking the aggregates in either a sodium sulfate or a magnesium