# Stone Matrix Asphalt (SMA) Determination of Dry Rodded VCA

### Stone Matrix Asphalt (SMA): Determination of Dry Rodded VCA

Standard AASHTO R 46-08

AASHTO R 46-08 specification covers the design of Stone Matrix Asphalt (SMA) based on the volumetric properties of the SMA in terms of air voids (Va), voids in the mineral aggregate (VMA), and the presence of stone-on-stone contact.

Voids in the Coarse Aggregate (VCA) is the volume between the coarse aggregate particles. This volume includes filler, fine aggregate, air voids, asphalt binder, and stabilizing additive (if used).
Coarse-aggregate fraction is that portion of the total aggregate blend retained on the 4.75-mm (No. 4) sieve for 12.5-mm (1/2-in.) and 19-mm (3/4-in.) SMA. For the 9.5-mm (3/8-in.) nominal-maximum aggregate size SMA, the coarse aggregate is that portion of the total aggregate blend retained on the 2.36-mm (No. 8) sieve.

For best performance, the SMA must have a coarse-aggregate skeleton with stone-on-stone contact. The condition of stone-on-stone contact within an SMA is defined as the point at which the VCA of the compacted mixture is less than the VCA of the coarse aggregate in the dry-rodded test.

The dry-rodded VCA of the coarse-aggregate fraction (VCADRC) is determined by compacting the stone with the dry-rodded technique in accordance with AASHTO T 19. VCADRC is calculated using the equation given below;

$V C A D R C = G C A γ w − γ s G C A γ w × 100$ where:
GCA = bulk specific gravity of the coarse aggregate, (AASHTO T 85);
γs = unit weight of coarse aggregate fraction in the dry rodded condition (AASHTO T 19), kg/m3 (lb/ft3); and
γw = unit weight of water, 1000 kg/m3 [62.4 lb/ft3].

## Stone Matrix Asphalt (SMA)

Hot Mix Asphalt (HMA) consisting of a coarse aggregate skeleton with coarse aggregate-on-coarse aggregate contact (stone-on-stone contact) and a rich asphalt binder mortar. The coarse aggregate is generally considered to be that fraction of the aggregate retained on the 4.75-mm (No. 4) sieve but may be designated as other sizes.

## Air Voids (Va)

Total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the bulk volume of the compacted paving mixture.

## Voids in the Mineral Aggregate (VMA)

The volume of the intergranular void space between the aggregate particles of a compacted paving mixture that includes the air voids and the effective binder content, expressed as a percent of the total volume of the specimen.

## Voids in the Coarse Aggregate (VCA)

The volume between the coarse aggregate particles, which includes the volume of filler, fine aggregate, air voids, asphalt binder, and stabilizing additive (if used).

## SMA Mortar

A mixture of asphalt binder, filler (material passing the 0.075-mm (No. 200) sieve), and stabilizing additive.

Either cellulose or mineral fiber.

DRY RODDED VOIDS IN COARSE AGGREGATE