The theoretical maximum specific gravity (GMM) of a Hot Mix Asphalt (HMA) mixture is the specific gravity excluding air voids.
Thus, theoretically, if all the air voids were eliminated from an HMA sample, the combined specific gravity of the remaining aggregate and asphalt binder would be the theoretical maximum specific gravity.
Theoretical maximum specific gravity can be multiplied by the density of water (62.4 lb/ft3 or 1000 g/L) to obtain a theoretical maximum density (TMD) or “Rice” density (named after James Rice, who developed the test procedure).
Theoretical maximum specific gravity is a critical HMA characteristic because it is used to calculate percent air voids in compacted HMA. This calculation is used both in Superpave mix design and determination of in-place air voids in the field.
Theoretical maximum specific gravity is determined by taking a sample of loose HMA (i.e., not compacted), weighing it and then determining its volume by calculating the volume of water it displaces.
Theoretical maximum specific gravity is then the sample weight divided by its volume.
The theoretical maximum specific gravity test is integral to Superpave mix design as well as field quality assurance.
Theoretical maximum specific gravity is used along with bulk specific gravity values from field cores and laboratory compacted specimens to calculate air voids and the in-place air voids of a HMA pavement.
It is also used to calculate the amount of asphalt absorbed in a HMA mixture (Vba) , which is then used in determining the effective asphalt content (Pbe).
The basic premise of the maximum specific gravity is to divide the mass of the sample by the volume of the sample excluding the air voids.
The mass is determined by measuring the dry mass of the sample either at the beginning of the test or after it has been dried at the end of the test.
The volume is calculated by weighing the mass of the water displaced by the sample and dividing by the unit weight of water.
The AutoRice is an automatic control unit for the Maximum Specific Gravity test.
Rice test results are critical for pavement quality, mixture design and laboratory mixture performance determination.
By pressing a button, the AutoRice starts the vacuum pump, regulates the vacuum pressure, precisely controls the vacuum time and monitors the shaker frequency and acceleration which is a parameter that is not currently monitored during the test.
Monitoring the three factors during the test can help agencies and contractors achieve better accuracy and repeatability. Data from the Rice test can be downloaded via the USB port.
AutoRice has to be connected with a compatible vacuum pump, vacuum pycnometer and electromagnetic vibro-deareator in order to perform the rice test as per standards.
- Controls and monitors Rice test (AASHTO T209 & ASTM D2041) vacuum pressure and vacuum time.
- Reduces operator errors improving accuracy and repeatability.
- Provides capability to enter weights and calculate max specific gravity results.
- Replaces vacuum gauge.
Technical Specifications
- Foot print: 12”x9”x4” (30x22x10 cm)
- Hose connection: 3/8” hose barb
- Max pump power: 3/4 HP
- Vacuum control: ± 0.4 mmHg at 27.5 mmHg
- Power supply: 110/220V
- Weight: 5 lbs (2.5 kg)