Volume 8, No. 16Journal 16

Freddy A. Reyes, Luis A. Mantilla, Oscar Reyes (Author)

Asphalt Mixtures. Dynamic characterization of a porous asphalt mix with added plastic waste using fatigue testing bench techniques

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This article describes the execution of both destructive and non-destructive dynamic laboratory tests on a porous asphalt material modified with recycled polyethylene strips derived from milk bags, with the objective of determining its properties and optimal temperature range for use.

The plastic material was introduced into the asphalt mixture during the blending of the aggregate and asphalt, in strips approximately 40 mm x 50 mm in size.

Dynamic modulus tests were carried out at 10, 20, and 30°C, and at frequencies of 1.6, 2.5, and 5.0 Hz. Fatigue laws were evaluated at three different strain levels and at temperatures of 15, 25, and 35°C. Rutting tests were performed using the LCPC (Laboratoire Central des Ponts et Chaussées, France) methodology at 60°C and 42 rpm.

The main results obtained included the optimal temperature ranges for using the material, as well as the improvement percentages in its rheological and drainage properties.

Pedro Romero, Leslie A. Myers (Author)

Structural pavement project. Characterization of the dynamic modulus of asphalt mixtures for mechanistic-empirical pavement design

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The new structural pavement design method based on mechanistic-empirical principles was recently developed in the United States through NCHRP Project 1-37A (Development of Mechanistic-Empirical Pavement Design). This method requires new types of testing for mixture characterization, such as dynamic modulus testing and indirect tensile strength, as well as detailed traffic and climate data.

Due to the novelty of the method, the need for new testing equipment, and the users’ lack of familiarity with the procedure, the method has not yet been officially adopted. To date, very few pavements have been designed using this new approach.

This study documents one of the first efforts to incorporate the required testing protocols for structural pavement design using the new mechanistic-empirical program.

The dynamic modulus of two 19-millimeter asphalt mixtures was determined using the tests proposed in NCHRP Report 465: Simple Performance Tests for Asphalt Mixtures (SPT). One of the mixtures was prepared with unmodified PG 64-28 asphalt, while the other was made with PG 58-34 asphalt modified with 25% TLA (Trinidad Lake Asphalt). Using the results from the SPT and the Superpave volumetric properties, the mechanistic-empirical pavement design method was applied to predict pavement performance under typical Utah conditions over a 20-year period.

Based on the results of this study, the economic benefits of asphalt modification were evaluated in terms of pavement lifespan under given traffic and climate scenarios. This lifespan was based on specific types of pavement distress, such as permanent deformation (rutting), thermal cracking, and others. With these new methods, highway agencies can more easily determine whether the additional cost of asphalt modification is justified based on the expected performance of the pavement. The adoption of the new mechanistic-empirical design system is recommended.

Breno Salgado Barra, Leto Momm, Liedi Légi Bariani Bernucci (Author)

Evaluation of the effect of water action on the physical and mechanical properties of asphalt mixtures from the Amazon region under conditions of induced moisture

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Being water one of the most detrimental natural agents affecting the maintenance of the physical and mechanical properties of pavements throughout their service life, the main focus of this study is to address the effect of water action on asphalt mixtures under conditions of induced moisture, using the theoretical principles proposed in the Modified Lottman Test (AASHTO T-283/89). The Amazon region, and particularly the State of Pará, was selected for material sourcing due to its high annual rainfall levels, ranging from approximately 2500 mm to 3000 mm. This high precipitation influenced the choice of materials used to formulate the mineral skeleton of the asphalt mixtures (senior granite aggregate, quartz sand, and limestone powder). The petroleum asphalt cement used (CAP 50/70) was sourced from the Lubricants and Petroleum Derivatives Refinery of the Northeast, located in the State of Ceará (LUBNOR/CE). A comparative analysis was conducted between asphalt mixtures produced using gradation curves formulated through the Fuller or Talbot Equation (referred to as theoretical curves) and those used in Brazil, such as the gradation curves from the National Department of Transport Infrastructure (DNIT). The DNIT Curve C was specifically explored, as it is widely used in the region for paving services.The study demonstrates the damaging effect of water in asphalt mixtures when present in the interstices of their composition, particularly under conditions of high thermal gradient.

Edgar Muñoz, Federico Núñez, Wilson Rodríguez, Camilo Otárola, Daniel Ruiz (Author)

Structural engineering: application of structural reliability principles for the evaluation of a steel bridge, supported by monitoring and instrumentation

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This article presents a structural reliability evaluation of the main components of one of the most important steel bridges on Colombia’s National Road Network. The assessment, based on structural reliability techniques, was supported by both field and office activities, including geometric surveying, mechanical testing, traffic counting, load testing, structural model calibration, instrumentation, monitoring, and numerical simulation. For the monitoring process, an electronic data acquisition system was implemented using a multipoint master-slave network (RS-485), incorporating signals from ten (10) strain gauges installed on the main structural elements of the bridge over a fifteen-day period. The monitoring allowed for a detailed analysis of the actual stress demands generated by traffic on the main bridge elements, which were compared against the design load (C40-95) specified by the Colombian Seismic Bridge Design Code (CCDSP). Significant overloads were identified on certain elements, posing safety concerns that require immediate corrective actions. Additionally, failure probabilities were calculated for some structural components, revealing values outside acceptable safety thresholds, thus compromising their stability and increasing the associated risk.

Julián Rivera, Edgardo Masciarelli (Author)

Traffic projections: methodology for estimating AADT for asphalt-related applications

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In studies involving asphalt mixtures—such as structural pavement design, service life estimation, suitability analysis, or mix design—it is essential to know the traffic volume that uses the roadway, expressed as AADT (Annual Average Daily Traffic), which represents the average daily volume over a full calendar year.

This value averages out traffic volumes generated by non-regular or intermittent activities (such as study, work, vacations, leisure, etc.). Due to this variability, continuous traffic counts are required to accurately determine the AADT, which often involves large-scale efforts and considerable resources.

In tactical and operational tasks (medium- and short-term), or in immediate-response situations where sufficient resources or data are not available, this becomes particularly challenging. For this reason, sporadic or short-term traffic counts are often used, and due to the lack of historical data, these are typically extrapolated subjectively by professionals who may not have a direct background in traffic engineering. This introduces a high degree of uncertainty, ultimately undermining the validity of other parameters that are otherwise based on accurate and reliable data, resulting in extremely low confidence levels in subsequent applications.

For these reasons, this master’s thesis aims to develop, disseminate, and apply an objective methodology for extrapolating short-term traffic counts into AADT values. The methodology is intended for application across a broad homogeneous region in Argentina, specifically the provinces of Buenos Aires, Santa Fe, Córdoba, Entre Ríos, and La Pampa.