Highways Research Group

University of Minho, Portugal

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Laboratory

 

The Laboratory of the Highways Research Group has equipment and facilities to:

  • Evaluate asphalt and aggregates properties

  • Produce asphalt mixes and samples to laboratory tests

  • Performe fatigue and permanent deformation tests

  • Evaluate pavement perfomance

 

The Highways Research Group has some formal statements, in the pavements area, with important official entities:

  • EP - National Road Administration

  • AENOR - North Highways

  • CM-STirso - S. Tirso City Council

 

Some of the laboratory equipment available in the Laboratory of the Pavement Research Group is presented in the following pictures.

 

 

Penetration test

 

One of the main tests for the characterisation of bitumen is the penetration test. It allows to classify indirectly the viscosity of pure bitumen. This test consists in measuring the penetration a needle with 100 grams of weight in a bitumen sample at a temperature of 25 ºC, after 5 seconds.

Softnening test

 

The “ring and ball” apparatus, used to evaluate the softening point of the bitumen, allows to classify the bitumen’s behaviour at higher temperatures. In this test the softening point is determined as being the temperature at which a sample of bitumen, subjected to a progressive increase of temperature and to the weight of a steel sphere, reach a consistence that leads to its flow through a ring of steel, until obtain a specific deformation.

Rolling thin film oven test

 

The Rolling Thin Film Oven Test (RTFOT), developed in 1963 by the California Division of Highways, consists in rotating glass containers with 35 grams of bitumen samples, inside an oven at a temperature of 163 ºC, during 75 minutes. In these conditions, the bitumen is aged in layers with a thickness of 1.25 mm.

1.    Determination of the initial characteristics of the pure bitumen

2.    Ageing of the bitumen in the oven:

3.    Determination of the characteristics of the aged bitumen

4.    Comparison with the initial characteristics of the bitumen to evaluate the ageing

Bituminous mixes production

 

The production of bituminous mixtures in laboratory is fundamental to the mix design and to the development of new bituminous mixtures. In the laboratory one can produce mixtures very similar to ones obtained in pavements. Different sections of the laboratory are used to product bituminous mixtures: i) the section where the aggregates and the bitumen are stockpiled; ii) the ovens where the aggregates and the bitumen are heated to achieve the temperature of mixture; iii) the section with the apparatus where the mixture is done; iv) the section where the mixture is compacted. In the laboratory, the mixture is usually compacted in slabs through the repeated passage of a light cylinder with vibration over the bituminous mixture. v) finally, the section where the slabs of bituminous mixture are sawed to produce cylindrical and prismatic specimens that will be tested.

Fatigue testing machine

  The fatigue testing machine is an apparatus manufactured by James Cox and Sons, CA, USA. The machine is controlled by a microcomputer using the ATS software that provides a feedback closed-loop control to the servohydraulic system, test temperature and data acquisition.
Although fatigue tests are normally executed at temperatures below 30 °C, the machine can provide temperature control between -20 °C and 70 °C, with an accuracy of 0.5 °C.
The closed-loop control of the servohydraulic system can execute tests of any frequency up to 20 Hz. The loading conditions include both the controlled-load and controlled-deformation modes. These capabilities allow the equipment to be used to define frequency response of a material over a wide range of temperatures, frequencies and strains.

Four point bending beam device

  The flexural beam device allows testing beam up to dimensions of 50 mm by 63 mm by 380 mm. The reaction points distance was set to 355.6 mm and the load points distance was set to 118.5 mm. This device is placed in the environmental chamber of the fatigue machine that maintains the test temperature by circulating air.

Shear testing machine

 

The shear testing machine is an apparatus manufactured by James Cox and Sons, CA, USA and introduced during the SHRP program. A microcomputer system using the ATS software provides feedback closed-loop control to the servo-hydraulic system, test temperature and data acquisition. The testing equipment can perform dynamic axial and shear loading with or without rest periods. Repetitive loading with sinusoidal, triangular, haversine or user defined patterns can be performed. The machine can provide temperature control between -20 °C and 70 °C, with an accuracy of 0.5 °C. The closed-loop control of the servohydraulic system can execute tests at any frequency from 0.01 to 20 Hz. The loading conditions include both the controlled-load and controlled-deformation modes. These capabilities allow the equipment to be used to define frequency response of a material over a wide range of temperatures, frequencies and strains.

Repetitive simple shear test at constant height

 

The repetitive simple shear test at constant height is a test introduced during the SHRP program performed on cylindrical specimens with either 15 cm diameter by 5 cm high or 20 cm diameter by 7.5 cm high can be used. The test specimens are glued to aluminum caps, top and bottom, using an epoxy resin. This process is made in an independent machine that ensure the parallelism between the two caps.
The test is performed applying a shear force measuring the permanent shear strain and correlating it with the rut depth.

Reflective cracking device

 

The RCD simulates the zone of the overlay layer that is subjected to reflective cracking, the zone above the existing crack of the old pavement. The RCD is composed by two U-shaped pieces where the specimen is fitted.The base of the device represents the existing pavement and the opening between the U-shaped pieces represents the crack width. The specimen is glued to the base of the device and pressed by pistons existing at the top of the device.

Rotary evaporator

 

The rotary evaporator together with a tube centrifuge is a fundamental device to the asphalt recovery procedure. The former allows binder extraction and recovery under controlled temperature and pressure. The latter allows fine aggregates extraction before solvent evaporation. The binder recovered may be used to perform tests such as penetration, ring and ball temperature, viscosity, etc., which are important either to check binder properties or to study their evolution with time.

 

Asphalt content

 

The TROXLER apparatus is used to measure asphalt content by means of asphalt combustion. It is very easy to use. The asphalt mixture is spread on mesh sample baskets and the basket assemblies are placed in the chamber. To begin the combustion process, it is necessary only to close the oven door and press the start key. Built-in scales automatically measure mass loss and percent loss. The results are used mostly to check asphalt content, namely within construction quality control systems.

 

 

 

Falling weight deflectometer

 

The Falling Weight Deflectometer is one of the most used devices to measure pavements deflection either at a network level or at a project level. The FWD produces a dynamic impulse load that simulates a moving wheel load, rather than a static, semi-static or vibratory load. FWD generated data, combined with layer thickness, can be used to obtain the "in-situ" resilient E-moduli of a pavement structure. This information can in turn be used in a structural analysis to determine the bearing capacity, estimate expected life, and calculate an overlay requirement.

Crack activity meter

 

The CAM is composed of two LVDTs (Linear Variable Differential Transformers), one placed vertically and the other placed horizontally, allowing the measurement of both differential movements.  The CAM is installed on a support on one side of the crack. On the other side, the horizontalsupport is placed on the vertical support. The CAM can be used to measure the crack activity of both transverse and longitudinal cracks. In both cases, the CAM is placed over the crack and as close to the track where the wheel load passes by as possible.  In each case, the wheel load should pass very close to the CAM to achieve the greatest crack movement, or activity.

Road Surface Profilometer
 

The Road Surface Profilometer (RSP) is designed to provide an advanced, automated, high quality pavement roughness and related measurements solution for engineers worldwide.
The RSP is capable of real time continuous highway-speed measurements of longitudinal profile (International Roughness Index (IRI) and Ride Number (RN)), transverse profile, rut depth, macro texture and geometrics (crossfall, curvature and gradient).
Measurements can be referenced to linear chainage or Differential Geographical Positioning System (DGPS), allowing easy integration to Geographic Information Systems (GIS).

The RSP is composed by 5 laser, 2 accelerometer, double wheel path version for measuring real-time IRI/RN and texture.

This equipment was acquired in the framework of the Programa Nacional de Re-equipamento Científico of the FCT (project REEQ/789/ECM/2005) and co-financed by the program POCI 2010 (fonte FEDER). The equipment is available for the scientific community. The conditions for this availability can be obtained through the e-mail:

sec-vias@civil.uminho.pt

 

Rotational Viscometer
 

The Viscometer combines traditional Brookfield accuracy, reliability and versatility with the advantages of continuous sensing, temperature measurement and data output to PC or printer. When controlled by PC, the DV-II+ PRO becomes a Rheometer with variable speed capability from 0.01 to 200 rpm. This instrument is the preferred choice for many Brookfield customers.

Main features includes: Continuous display of: Viscosity (cP or mPa·s), Temperature (°C or °F), Shear Rate, Shear Stress, % Torque, Spindle; Torque measurement accuracy: 1% of full scale range; Repeatability: 0.2% of full scale range; selectable speeds provide superior range of viscosity/shear measurements for use in stand-alone operation; Automate program control by PC; Automatic data collection; Built-in RTD temperature probe for sample monitoring

This equipment was acquired in the framework of the Programa Nacional de Re-equipamento Científico of the FCT (project REEQ/789/ECM/2005) and co-financed by the program POCI 2010 (fonte FEDER). The equipment is available for the scientific community. The conditions for this availability can be obtained through the e-mail:

sec-vias@civil.uminho.pt

 

GPS
 

The single frequency survey system (GPS) performs high accuracy static and kinematic data collection for the land surveyor.

The GPS is capable of centimeter accurate post-processed solutions, as well as sub-meter real-time Satellite Based Augmentation System (SBAS) solutions, such as WAAS and EGNOS. Built with an intuitive survey workflow that is both easy to learn and use, the SR20 offers the maximum in flexibility out of a GPS receiver. All of this coupled with the powerful Leica GPS technology makes this low-cost GPS receiver a great package.

Key Features: Powerful GPS engine that yields centimeter accurate results;  Flexible system to support a wide variety of Land Surveying and GIS requirements; Surveying applications including COGO and coordinate transformations; Leica Geo Office Software for powerful post-processing.

This equipment was acquired in the framework of the Programa Nacional de Re-equipamento Científico of the FCT (project REEQ/789/ECM/2005) and co-financed by the program POCI 2010 (fonte FEDER). The equipment is available for the scientific community. The conditions for this availability can be obtained through the e-mail:

sec-vias@civil.uminho.pt

Accelerated Polishing Machine
 

The PSV test calculates a Polished Stone Value for aggregates used in road surfaces, which gives a measure of the resistance to skidding.

The test is carried out by using two machines, S882 - the Accelerated Polishing Machine, and S885 - Skid Tester, (see separate Data Sheet for this machine). The Accelerated Polishing Machine polishes samples of aggregates, simulating actual road conditions.

This equipment was acquired in the framework of the Programa Nacional de Re-equipamento Científico of the FCT (project REEQ/789/ECM/2005) and co-financed by the program POCI 2010 (fonte FEDER). The equipment is available for the scientific community. The conditions for this availability can be obtained through the e-mail:

sec-vias@civil.uminho.pt

 

Accelerated Loading Facility

The Road Pavements Laboratory of the Department of Civil Engineering of the University of Minho joined together with the Road Pavements Laboratory of the Department of Civil Engineering of the University of Coimbra, in Portugal, are determined to build, commission and explore an “Accelerated Pavement Testing Simulator” to be used for research at university level. The expected conclusion of the facility construction is June 2007.

The testing system will have the following characteristics:

  • length of pavement under test: 12 m
  • width of testing pavement: 3 m
  • top testing speed: 15 km/h
  • vertical load (controllable): from 20 to 80 kN
  • vertical movement top speed: ≤ 10 mm/s
  • vertical movement stroke: >=80 mm
  • lateral “wander” movement stroke: ±250 mm (around centre point)
  • lateral “wander” movement top speed: ≤ 20 mm/s
  • wheels equiped with tyres:
    • single tyre: type 385R22,5
    • double tyre: type 245R17,5
 

 

 

 

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Last update: 13-Fev-2009