The test tracks of the PaveLab are constructed!

The construction of the test tracks is ended!

HVS Technology Transfer workshop

HVS Technology Transfer workshop 

Edgar Camacho-Garita
Fabricio Leiva-Villacorta, Ph.D.
Materials and Pavements Research Unit
edgar.camachogarita@ucr.ac.cr, 
fabricio.leiva@ucr.ac.cr
Key words: HVS, accelerated pavement testing, PAVELAB.

The National Laboratory of Material and Structural Models at University of Costa Rica (LanammeUCR) held a HVS Technology Transfer Workshop as part of the implementation process of its upcoming Accelerated Pavement Testing program. This workshop took place in January 2013 and covered the following topics:
• History and Program Establishment
• HVS Test Planning
• Logistics
• Instrumentation
• Data Handling & Analysis
• Correlations between Lab, APT and Field
• Reporting
• Coordination
This workshop had the participation of Mr. Louw du Plessis from the Council for Scientific and Industrial Research (CSIR) in South Africa, Dr. Wynand Steyn from the University of Pretoria also in South Africa and Mr. Salil Gokhale from Dynatest. Participants from LanammeUCR included Dr. Adriana Vargas, Ms. Paulina Leiva, Ms. Tania Avila, Mr. Edgar Camacho, Dr. Fabricio Leiva, Mr. Gustavo Badilla, Dr. Luis G. Loria and Dr. Jose P. Aguiar.

Construction of the Test Tracks at our Full Scale Facility for Accelerated Pavement Testing, the PaveLab

The construction of the test tracks at the full scale facily for accelerated pavement testing at the new buliding of the National Laboratory of Materials. and Structural Models of the University of Costa Rica. Six test tracks are being built, 3 are flexible and 3 semi-rigid using a CTB. The granular base was placed with finisher and the CTB mixed in a mixing truck and placed with a finisher as well!

This research effort corresponds to one of the most ambitious projects that have been developed in Latin America. The project team is integrated by 4 PhDs in pavements, 2 PhDs in geotechnical engineering, 2 PhDs in Hydraulics, and several engineers and chemist. The test tracks might have up to 84 sensors, including soil pressure gages, Multi-depth deflectometers, HMA pressure gages, LVDTs, among others. The testing device is a Heavy Vehicle Simulator (HVS) Mark VI from Dynatest. The experiment also will have a temperature chamber, and the test pit has also the capability of providing water-saturation through a piping system and a saturation chamber built beside the test tracks. Also, natural raining will be simulated through a special system. Therefore, full in-place conditions will be simulated and their effect on the pavement performance, assessed!

COMPACTION PROBLEMS OF THIN HMA LAYERS CONSTRUCTED ON WEAK PAVEMENTS

A Hot Mix-Asphalt (HMA) layer as the shown in the picture, having a thickness lower than 5 cm, placed over a weak pavement structure will be almost impossible to reach an optimum compaction level. In Costa Rica, LanammeUCR has recommended to the Maintenance Area of the Department of Transportation to pay this type of thin-layers based on samples on the volumetric properties go samples taken at HMA plant. Paying the material based on field air voids is a mistakes, since the weak pavement structure will not provide enough stiffness to function as a stable contraction platform, hence, the energy of the compactor will be dissipated within the weak pavement layers. Trying to apply more vibration to the compactor will break the bigger aggregate particles. In Costa Rica, layers compacted with less than 4 cm are call non-structural layers, however, there is a thin line to differentiate the behavior if the layer reaches up to 5 cm, when weaker pavements provide the base beneath the new HMA. An useful to determine the pavement stiffness is the Falling Weight Deflectometer (FWD) or the old, but still in use, Benkelman Beam. Both equipments, by means of the pavement deflection basin or the maximum deflection, provide important information on the structural condition of the pavement structure. Costa Rica has had 5 campaigns of evaluation of its paved national road network, of about 5,000.00 km. Among the evaluated parameters, FWD data is available for each meter of the national road network since 2004, therefore, the project engineer has a powerful tool to determine the pavement condition of his project and to define the strategy to apply. As we have insisted before, this type of decision requires a well prepared pavement engineer with sound knowledge to understand the pavement behavior, its design process, material properties and the expected performance. Those characteristics, plus good field experience will leave to the citizens the best project with the highest possible quality, according the available budget.