Carlos Videla

Calibration and Validation of Condition Indicator for Managing Urban Pavement Networks

Deterioration indexes that may combine types of surface distresses, serviceability, and structural indicators are commonly used for pavement management at the network level. These indexes differ in the types of deterioration and criteria considered to quantify severity and density of distresses. Most of these indexes were developed for interurban road networks; therefore, their application to urban networks is complex and not representative. For this reason, there is a need for a better understanding of urban pavement behavior to enable collection of the distresses relevant to these types of pavements and development of an overall condition index for urban pavements that represents the mix of the more relevant distresses for use in network analysis. This study is part of a 3-year project developed in Chile: Research and Development of Solutions for Urban Pavement Management in Chile. The main objective of this study was to calibrate and to validate an urban pavement condition index (UPCI) representative of the overall condition of these pavements, according to objective measures of surface distresses and evaluations of an expert panel. The scope of this study included the development of distress evaluation guidelines for asphalt and concrete pavements considering manual and automated surveys, the application of these guidelines in different types of urban networks, and the assessment of these networks by an expert panel. Finally, three UPCI equations were obtained with satisfactory validation for asphalt pavements with manual and automated data collection and for concrete pavements with manual data collection.

An iterative approach for the optimization of pavement maintenance management at the network level.

Pavement maintenance is one of the major issues of public agencies. Insufficient investment or inefficient maintenance strategies lead to high economic expenses in the long term. Under budgetary restrictions, the optimal allocation of resources becomes a crucial aspect. Two traditional approaches (sequential and holistic) and four classes of optimization methods (selection based on ranking, mathematical optimization, near optimization, and other methods) have been applied to solve this problem. They vary in the number of alternatives considered and how the selection process is performed. Therefore, a previous understanding of the problem is mandatory to identify the most suitable approach and method for a particular network. This study aims to assist highway agencies, researchers, and practitioners on when and how to apply available methods based on a comparative analysis of the current state of the practice. Holistic approach tackles the problem considering the overall network condition, while the sequential approach is easier to implement and understand, but may lead to solutions far from optimal. Scenarios defining the suitability of these approaches are defined. Finally, an iterative approach gathering the advantages of traditional approaches is proposed and applied in a case study. The proposed approach considers the overall network condition in a simpler and more intuitive manner than the holistic approach.

Sustainable Pavement Management. Integrating Economic, Technical, and Environmental Aspects in Decision Making

Sustainability, which is founded on the reconciliation of economic, environmental, and social aspects, has become a major issue for infrastructure managers. The economic and environmental impacts of pavement maintenance are not negligible. More than

MODELING PORTLAND BLAST-FURNACE SLAG CEMENT HIGH-PERFORMANCE CONCRETE

400 billion are invested globally each year in pavement construction and maintenance. These projects increase the environmental impacts of vehicle operation by 10%. Because maintenance should be technically appropriate, infrastructure managers must integrate technical, economic, and environmental aspects in the evaluation of maintenance alternatives over the life cycle of a pavement. However, these aspects are normally assessed in measurement units that are difficult to combine in the decision-making process. This research examined and compared methods for the integrated consideration of technical, economic, and environmental aspects, and this study aimed to assist highway agencies, researchers, and practitioners with the integration of these aspects for the sustainable management of pavements. For this purpose, a set of maintenance alternatives for asphalt pavements was evaluated. Methods for the integration of these aspects were explored and led to recommendations for the most suitable methods for different scenarios. As a result of this analysis, the analytic hierarchy process (AHP) is recommended when the number of alternatives is small. In these situations, the AHP leads to results that are similar to those of the weighting-sum and multiattribute approaches that are frequently used for intuitive selection. However, when the number of alternatives is large, pair comparison becomes difficult with the AHP and the weighting-sum method becomes more appropriate.

Reducing concrete permeability by using natural pozzolans and reduced aggregate-to-pasteratio

This work focused on portland blast-furnace slag cement high performance concrete (HPC), with specified 28-day compressive strengths of 60-110 MPa. Compressive and flexural strength, elastic modulus, abrasion resistance, and shrinkage properties were studied. Lab test results showed it is possible to develop a general compressive strength model combining a hyperbolic equation for strength evolution and an exponential equation for mixture design parameters. It was also concluded that the measured moduli of elasticity are lower than the ACI predicted values, and that the square root of the compressive strength was not a good predictor of the flexural strength for the materials used. Also, it was concluded that the ASTM C 944-99 abrasion test is not an effective way to measure abrasion resistance of HPC. Autogenous shrinkage was shown to be a significant part of total shrinkage. An updated FIB 2000 model to local conditions was successfully developed to predict shrinkage of HPC.

Application of Markov chains and Monte Carlo simulations for developing pavement performance models for urban network management

AbstractImproved durability of concrete is mainly achieved with low-permeability. Permeability depends on permeability of the bulk cement paste (CP) and that of its interfacial transition zone (ITZ). Even though permeability of CP is well understood and can be adequately controlled, permeability of ITZ is not well understood yet. This paper shows that minimizing permeability of concrete requires minimizing permeability of CP by using a supplementary cementing material (SCM) such as natural pozzolans (NP) and minimizing ITZ by reducing aggregate content until maximum cement content. This was done by comparing performance of concrete made with ordinary Portland cement (OPC) and blended cement (OPC+NP) at the same w/b, and by comparing performance of concrete with different amount of ITZ at the same w/b. All of this was performed through testing of mechanical properties, air permeability, sorptivity, chloride ion diffusion, and aggregate specific surface. Results show that NP reduced air permeability by 84% ...

Laboratory study of mixture proportioning for pervious concrete pavement

Abstract Existing performance models developed for interurban pavements are not applicable to urban pavements due to differences in traffic demands and deterioration trends. The objective of the study was to develop performance models for the management of urban pavement networks. Markov chains and Monte Carlo simulation were applied to account for the probabilistic nature of pavements deterioration over time, using data collected in the field. One of the advantages of this methodology is that it can be used by local agencies with scarce technical resources and historical data. Eight performance models were developed and successfully validated for asphalt and concrete pavements in humid, dry and Mediterranean climates with different functional hierarchies. The resulting models evidence the impact of design, traffic demand, climate and construction standards on urban pavements performance. Predicted service life of asphalt and concrete pavements in primary networks are consistent with design standards. However, pavements in secondary and local networks present shorter and longer service life compared to design life, respectively. Climate is a relevant factor for asphalt pavements, where higher deterioration was observed compared to that expected. Opposite to this, no relevant differences between design and performance can be attributed to climate in concrete pavements.

Efecto del secado en ambiente de servicio en la evolución de las propiedades mecánicas de hormigones livianos estructurales

The present research shows the results of an equation that allows to dose pervious concrete in function of water to cement ratio and the required interconnected void content in hardened concrete. Eighteen different mixtures - with w/c ratio between 0.29 and 0.41- were analyzed using this equation. The samples were made in the laboratory and compacted with a heavy roller simulating site conditions. The results allow a good characterization of these mixtures both mechanical and hydraulic behavior. Relationships between void contents, infiltration rate and flexural strength were found.

Effect of lightweight aggregate intrinsic Strength on lightweight concrete compressive strength and modulus of elasticity

In this paper the effect of the ambient relative humidity at service on the compressive and splitting strengths and in the modulus of elasticity of structural lightweight concretes is evaluated. Also, relationships are proposed allowing estimating these properties as a function of the ambient relative humidity and drying time. The concretes were made with two types of coarse lightweight aggregates, pumice and fly ash pellets, and with normal density fine aggregate. The concretes were subjected to two different environmental service conditions: 90% relative humidity and curing at 90% relative humidity during the first seven days and then to 50% relative humidity until the age of testing. The samples were tested at 7, 28, 60 and 90 days of age. An important deterioration of the measured properties due to the effect of the drying conditions was observed; at 83 days of drying, the compressive and splitting strength losses were on average of 20% and 15%, respectively, and of the modulus of elasticity of 40% with respect to concretes at 90% relative humidity. It was concluded that there are two main variables that can explain the loss of strength of lightweight concrete due to the effect of a dry environment. The first of them is the water-cement ratio which controls, among others, the permeability of the mortar or resistant phase. The second one is the relative content of lightweight aggregate in the concrete.