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03-302 Warsaw
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Pavement Diagnosic Laboratory - Activity PDF Print E-mail

  Pavement Diagnosic Laboratory

The activity of Pavement Diagnostics Laboratory covers tests, measurements and analysis of such pavement technical parameters like bearing capacity, longitudinal and transverse evenness, antiskid properties, pavement condition.
They issue expert appraisements and opinions based on the complex investigation of road network and road sections prepared for reconstruction. Pavement Diagnostics Division carries out research works in the following areas of road construction: materials used in pavement construction, structural design methods, road traffic safety.
In their work they apply modern research and analysis methods and profit from rich professional experience of the team.

EQUIPMENT

FALLING WEIGHT DEFLECTOMETER (FWD)
In most of the countries Falling Weight Deflectometer (FWD) is the most common device for bearing capacity assessment. Different types of pavements are assessed during and after the construction. Most of these are typical roads, airport pavements, but also large industrial surfaces. Currently, there are over 300 FWD devices on all over the world.

Research method
The analysis of load capacity is made on the basis of deflection bowl measurements. The pavement deflection caused by the load is measured with the use of sensors - geophones, which are situated in the pressure centre (plate bearing device) and in certain distances from the central point (e.g. 300, 600, 900, 1200, 1500 and 1800 mm). Knowing the pavement construction and the depth and shape of deflection bowl, we can assess pavement condition.
FWD device has the ability of the maximum force of 120 kN, it simulates the pressure made by a lorry moving at a speed of  35 - 40 km/h. The device is controlled automatically. The driver, who is simultaneously the operator, chooses the place and controls the course of the measurement process with the use of some additional devices (Distance Measuring Instrument, camera). FWD device is steered by the on board unit processor and the correctness of the results gained during the measurements is controlled by the computer.
The measurement results gathered by the device can be used not only on the project level but also on the level of road network. The network - level results can be used among other things in building up the data bank of the load capacity which is very helpful in the establishing of the proper budget, means division, selecting the sections that need repair or redevelopment and establishing the hierarchy of needs on the road network.

The main task of FWD is load capacity assessment. However, the measurement results can also be used in:
• relative comparing of the condition of particular pavement layers on the basis on deflection measurements
• identification of the resilient modulus of particular pavement layers
• direct calculations of the defection of flexible pavement
• structural assessment of bound base course
• load capacity assessment of unbound material


 

SKID RESISTANCE TESTER (SRT-3)
The device SRT-3 represents the third generation of skid resistance testers. The main part of the Skid Resistance Tester is a dynamometric trailer, which has an original kinematic scheme.
Since 1992 our SRT-3 has been taking part in different international trials organized by PIARC and FEHRL.
At present eleven sets of SRT-3 work in Poland and Lithuania.

APPLICATIONS
Measurement of friction coefficient at fully-locked test-wheel by two equivalent methods:
• through the measurement of a braking moment through the direct measurement of the force of friction - free from influences from a moment of inertia
• Measurement of peak friction
• Measurement of coefficient of friction on any curved bends
• Measurement of reaction in suspension of the trailer
• Possibility to determine longitudinal friction coefficient as a function of slip speed or relative slip in each breaking process


TECHNICAL DATA
 total mass    - 370 kg
 normal load on the tire  - 2943 N (300 kG)
  nominal test speed   - 60 km/h
 test speed range   - 30-120 km/h
 test wheel    - 165 R15/PIARC-Vredestain - smooth tyre with circular
 grooving (base test tyre) - 185/70 R14 Barum Bravura (Continental)
 hydropneumatic test-wheel braking system
 pneumatic system of control and pressing out the water
 regulated time of entering of the test-wheel into the blocking
 regulated real measurement time (time of setting avarage values)

SIR-20 - GROUND PENETRARING RADAR
DATA ACQUISITION SYSTEM
Ground Penetrating Radar SIR-20 represents developing technology in the field of nondestructive testing (NDT). System gives real time information about type of pavement, pavement layer thickness, homogeneous sections or anomalies in structure.
Ground Penetrating Radar SIR-20 can carry out measurements at highway speeds, which eliminates the needs for lane closures, and provides a safer working environment.

APPLICATIONS:
Surface quality control:
verifying new pavement layer thickness (acceptance testing),
Structure research:
pavement layers identyfication, determinig variability  in pavement structure, determining homogeneous sections, underground utilities location.
Bridge diagnostics:
determinig asphalt and concrete layer thickness situated under reinforcement

TECHNICAL DATA
• antenna frequency/max. deph of penetration
       2,2 Ghz / about 45 cm
       1,0 GHz / about 90 cm
        0,4 GHz / about 250 cm
• measuring speed - up to 100 km/h with 0,05 m measuring step
• possibility of measuring with two antennas simultaneously
• possibility of measuring in the toughest field  conditions by the survey cart
• vide record or GPS positioning as an option

RESEARCH METHOD:
The principle behind the test is one of applying high frequency electromagnetic impulses to the structure through the use of antennae. The wave produced may be travelling through a multi-layer system. The electromagnetic pulse will be partially transmitted and partially reflected at each change of interface represented by a change in the dielectric properties of the structure material. By recording the energy reflected from different interfaces, a representation of the subsurface may be built up. The data recorded are stored in the time domain and may be displayed either on a computer screen, printed out on a chart recorder or stored for future analysis on a computer.


ADDITIONAL EQUIPMENTS:
Within next year the following tools are to be purchased:
- laser deflactometer TSD
- dynamic deflactometer HWD
- system of automatic evaluation of the surface condition
- 3D radar system
- CPX system for pavement noise measurement