Broce Lab

The Superpave Gyratory Compactor (SGC) from PINE Instruments are used to compact asphalt mixes at a constant consolidation pressure, a constant angle of gyration and a fixed speed of gyration. The SGC device has an integrated computer control system, a control panel, two USB ports, a compaction chamber, an integrated angle of gyration measurement system and an extruder for removing compacted specimens. Generally, the device is used to compact specimens of two different diameters, namely, 150 mm and 100 mm diameter following AASHTO T 312 procedure. The consolidation pressure, angle of gyration and the mode of operation of compaction can be altered using the control panel.

The Linear Kneading Compactor from PMW, Inc. is used to produce slab or beam specimens that represents more of the compaction produced by rollers in the field. T The compactor is driven by a hydraulic unit placed next to it. The slab or beam samples required for Hamburg wheel tracking (HWT) test or beam fatigue test can be prepared using this compactor. In addition to compacting beam or slab specimens of asphalt mixes, the linear kneading compactor can be used to compact stabilized subgrade and other specimens for measuring flexural modulus and fatigue life.

Texas Gyratory Compactor, also known as Gyratory- Shear Molding Press, is used to prepare 4- inch diameter specimens required for Hveem method. The features of the compactor include the following: Bench space: W= 24 -inch, D= 15 -inch, H= 30 -inch, 3/4 hp, electric brake, 10/1 gear box and No. 50 chain drive. Asphalt samples are generally prepared using the “OHD L-8, Compacting Test Specimens of Bituminous Mixtures” test method using this compactor. It is also used in OHD L-8, Compacting Bituminous Mixtures for Stabilometer Value.

The Laboratory Bench Mixer, Hobart Model HL 120,  has a mixing capacity of 12-quart. (0.401 cu. ft.) and a 15-minute motor-driven timer. It is also known as a planetary mixer..The device consists of a stainless-steel bowl, a flat-type aluminum grid beater and an aluminum dough hook. The beater attached to the device ensures thorough blending and mixing. The rate of mixing can be adjusted using the selective agitator transmission having 3 speed settings.

Rutting and moisture susceptibility of hot mix asphalt (HMA) and warm mix asphalt (WMA) specimens are evaluated by conducting Hamburg Wheel Tracking (HWT). The Hamburg Wheel Tracking  device in Broce Lab is manufactured by PMW Inc. Typically, the AASHTO T 324 standard test method is followed for this purpose in which the specimens are submerged in a temperature-controlled water bath at 50°C and repetitively loaded using a reciprocating steel wheel with a  frequency of 52 passes/minute. The wheel load applied to the specimen is equal to 705 N. The average linear speed of the wheel is approximately 1.1 km/h and traveling approximately 230 -mm (9.05 -in.) before reversing the movement direction. Rut depths are measured along the length of the wheel path at 11 equally-spaced points. Different parameters such as post compaction deformation, creep slope, stripping inflection point (SIP) and stripping slope of an asphalt mix are determined from the HWT test. It is also used in OHD L-55, Hamburg Rut Testing of Compacted Hot-Mix Asphalt (HMA).

The Asphalt Mix Performance Tester (AMPT), earlier known as Simple Performance Tester (SPT), is a computer-controlled hydraulic testing device capable of producing cyclic loading over a range of temperature and frequency. The device available in Broce lab is known as AMPTPRO^® and was manufactured by IPC Global. The load capacity of AMPT is 19kN (static) and 17 kN (Dynamic) with a frequency ranging from 0.01 to 70Hz (sinusoidal loading). Asphalt mix specimens can be tested at a temperature between -5°C and +70°C using the temperature-controlled chamber of the AMPT. The AMPT is used to produce the required asphalt mix design parameters for the AASHTOWare PavementME Design software. Also, this device is used as a standalone device for other types of performance testing. Some of the major tests  conducted in the OU Broce laboratory using AMPT include the following:

1. AASHTO TP79 (NCHRP 9-29) - Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt Using the Asphalt Mixture Performance Tester (AMPT).
2. AASHTO TP107 / S-VECD - Determining the Damage Characteristic Curve of Asphalt Mixtures from Direct Tension Cyclic Fatigue Test.
3. ASTM D8044 - Evaluation of Asphalt Mixture Cracking Resistance using the Semi- Circular Bend Test (SCB) at Intermediate Temperatures.
4. AASHTO TP124 - Determining the Fracture potential of Asphalt Mixtures Using the Flexibility Index Test (FIT) Determining the Fracture.
5. Tex-248-F / ASTM WK26816 - Determining the Susceptibility of Asphalt Mixtures to Cracking using the Overlay Tester.                                                       

The Asphalt Performance Tester (GCTS ATM 100) is an advanced testing equipment for hot mix asphalt (HMA) and warm mix asphalt (WMA). This equipment can be configured to test asphalt specimens under variety of modes. The equipment includes an electro-hydraulic digital servo control system capable of producing a dynamic loading of 100 kN. Also, asphalt specimens can be tested at frequencies up to 70 Hz. The integrated environmental chamber houses the necessary accessories for various testing, such as dynamic modulus, flow number, flow time, indirect tension, beam flexural fatigue and resilient modulus.

The AccuFoamer from InstroTek^®, Inc. is designed to produce Warm Mix Asphalt (WMA) in the laboratory using the foaming technique involving injection of water. This device has separate pressurized chambers for binder and foaming. The bitumen chamber has a capacity of 5 liter (1.3 gallon) and can be heated accurately to 190°C (375°F). Using advanced electronics and software, the device adjusts the pressure and temperature, and makes foaming fast and accurate. 

Moisture Induced Stress Tester (MIST) from InstroTek, Inc., is used for laboratory simulation of stripping potential of asphalt pavements due to water intrusion and repeated traffic loading. The MIST device complies with the ASTM D7870 standard specifications. The device consists of a pressurized chamber to condition compacted asphalt mix specimens. The stripping mechanism is simulated by generating both pore pressure and action of an automobile tire on a wet surface with the help of pushing and pulling temperature controlled water through a compacted asphalt sample. The advantage of the MIST device is that, the tests can be performed at different pressures and temperatures in an accelerated manner, requiring less time compared to the conventional moisture sensitivity tests.

The AP-20 NCAT Asphalt Content Furnace from Global Gilson Company, Inc. is used to determine the asphalt content of asphalt mixes within 30-45 minutes. Asphalt content of a sample up to 5,000 g can be determined at once using this device. At first, the asphalt sample is weighed and divided into two screened baskets, and placed into the furnace chamber. The furnace is pre-heated before testing to a default temperature. A built-in electronic balance automatically monitors sample weight throughout the process. After completion of the test, the device automatically ends the test and prints the results. The results as a percentage are generally reported as asphalt content per weight of sample.

The CoreLok machine from InstroTek is used to seal asphalt samples for measurement of density by water displacement method. Using this device, asphalt samples can be automatically sealed with a puncture resistant polymer bag. Densities measured with the Corelok^® system have shown high reproducibility. This system is used in density measurements of asphalt and aggregate following ASTM D6752, ASTM D6857, ASTM D7063, OHD L-45 and OHD L-14. test methods.

The Temperature and Humidity Chamber from ESPEC is used to condition asphalt mix, stabilized soil, stabilized aggregate and other specimens at temperatures ranging from -35°C to 180°C. The chamber has a capacity of 8 cu. ft.  with a working space of 19.7 -inch x 23.6 inch x 29.5 inch. The heating and cooling rate of the chamber are 5.5°C/min and 5°C/min, respectively. Also, the humidity of the chamber can be controlled between 10% to 98% of the relative humidity to condition asphalt mix or other specimens. This chamber is used in moisture-induced damage evaluation of asphalt mixes using AASHTO T 283 method. This equpment is also used to determine freeze-thaw durability of stabilized soil and stabilized aggregate specimens.

The theoretical maximum specific gravity of an asphalt mix is determined using the Rice apparatus following AASHTO T 209 test method. A Rice Test Apparatus consists of a Rice test vibrator, a pycnometer, a deairing system and a manometer. The Vacuum Pycnometer is clamped with the Rice test vibrator from ELE International through adjustable clamps to hold the pycnometer securely to the base during vibration.

Broce lab has two Blue M series Mechanical Convection Ovens for heating and conditioning of aggregates, asphalt binders and asphalt mixes. These ovens are capable of producing a temperature ranging from 15°C above ambient to 350°C. These ovens are frequently used for drying of aggregates, production of asphalt mixes and conditioning of asphalt mix and other specimens.

The Heavy Duty Saws, one  from GCTS and the other from MK Diamond products, are used for cutting asphalt mix samples to desired shape and size as recommended by different test procedures. Also, these saws are used to make notches of desired depth as required for semi-circular bend specimens.

The Coring Machine or Core Drill is used to obtain cores of 4 -inch diameter sample by coring Superpave gyratory compacted specimens. Specimens required for dynamic modulus test, cyclic direct tension test etc. are prepared using this drill. The adjustable clamping mechanism holds the specimen securely to eliminate sample movement during coring. The drill utilizes a high-performance motor to ensure precise coring. 

The Testing Screens and Shaker from Global Gilson company, Inc. are  used extensively for processing aggregates for further testing and for producing asphalt mixes and stabilized aggregate specimens. A wide range of standard sieves are available for particle size determination of large samples of aggregate. Depending on material type, a batch of about one cubic foot (0.028m³) or more can be processed into required fractions in three to five minutes. The sieve analysis of the aggregate samples is conducted following AASHTO T27 and ASTM C136 test methods.

Mary-Ann Motorized Sieve Shaker and sieves from Humbolt are also for processing aggregates. Generally, sieves with 12 -inch diameter are used with Mary-Ann Motorized Sieve Shaker. This shaker promotes the sieving action by placing the sieves at an angle of 45° while rotating using a motor and tapping from hardwood-faced aluminum hammers. The sieve analysis of aggregate is conducted in accordance with AASHTO T27 and ASTM C136 test methods.

A universal Sample Splitter from Global Gilson Company, Inc. is used to produce representative specimens from bulk aggregate sample. The sample splitter has an adjustable chute system and a lever-release hopper. The adjustable-width chutes offer optimal versatility for reducing bulk samples and the lever-release hoppers enable samples to flow evenly across the entire width of chutes. With the help of a row of aluminum bar the splitter can direct equal amounts of aggregate or other bulk materials to each side of the splitter into sample collection pans. The sample splitter complies with the AASHTO T 248, AASHTO T 27, ASTM C136, ASTM C702, ASTM C778 and ASTM D75 standards.

The abrasion resistance and durability of mineral aggregates are determined using Micro-Deval Apparatus from Global Gilson Company, Inc. This apparatus consists of a two-tier unit with a sturdy steel frame. Each of the tier carries one 5 liter jar having an internal diameter of 194 mm and internal height of 170 mm with locking cover. The test time, total revolutions and rpm of jars are maintained accurately using an electronic controller with optical sensing system. The apparatus is compliant with AASHTO T 327, TxDOT 845-49-40, ASTM D6928 and ASTM D7428 specifications. Aggregate samples are placed in the steel jar with an abrasive charge of up to 5,000 g of 9.5 mm diameter stainless steel balls and water. The quality of the aggregate is determined by percentage loss from the gradation results after rotating the jar at a speed of 100 rpm for two hours.

The Los Angeles Abrasion test (also known as LA abrasion test) is a widely used test to determine the abrasion quality of aggregate. The test is conducted using the AASHTO T 96 and ASTM C131 test methods. The LA abrasion test measures the degradation of aggregate due to the combined actions of abrasion, impact and grinding in a rotating steel drum containing a specified number of steel spheres. The machine can rotate at a speed of 30-33 rpm. The number of spheres used for a test depends on the gradation of the aggregate. Generally, each steel sphere has a dimeter of 46-48 mm and twelve steel spheres weigh approximately 390-445 g. 

The portion of undesirable clay-like fines in granular soils and fine aggregates is determined by sand equivalent test using a motorized Sand Equivalent Shaker manufactured by Humbolt. The sand equivalent shaker has two separate electronic timers; one at 45 seconds and the other at 10 minutes for increased accuracy. The device delivers an 8 -inch (203 mm) stroke at a speed of 175 ±2 strokes per minute.

Bulk soil sample required for different soil tests such as Atterberg limit, particle size analysis and other standard laboratory tests is prepared using the Soil Grinder. This device preserves the true grain size while reducing agglomerations of soil to individual grain.

The Motorized Liquid Limit Device in the Broce lab is used to determine the Atterberg limits of soil specimens. The device consists of a liquid limit brail with geared motor to give proper operating speed and automatic counter. This machine supports the ASTM D4318, AASHTO T89 and AASHTO T90 test methods.

The Soil Dispersion Mixer is used for dispersing soil suspensions for hydrometer testing of subgrade soils. The mixer has a stirring apparatus with paddle and a dispersion cup. It can operate at a speed above 10,000 RPM. This device supports the ASTM D422 and AASHTO T88 test methods.

The Mechanical Compactor automatically compacts and rotates mold after each blow while keeping track of the number of hammer blows and shutting off once a preset number of blows is reached. The start/stop function of the compactor is independent of the counter. The unit can be used to perform standard or modified compaction tests using a 5.5 lb. (2.5 kg) hammer with 12 -inch (305 mm) height of drop or a 10 lb. (4.5 kg) hammer with 18 -inch (457 mm) drop. The hammer lift compensates the height of the drop for soil thickness in the mold during compaction. Hammer weight is concentrated at the foot, allowing free fall of the hammer.