Past Research

TXDOT 0-6740: Improvement of Construction Quality Control by Using Intelligent Compaction Technology for Base and Soil

Current practice for field compaction quality control and acceptance for base and soil layers is based on the compacted density and moisture content by nuclear density gauge (NDG). Since density measurements are truly spot tests, they cannot represent the quality and uniformity of compaction in a continuous manner. Intelligent compaction (IC) technique is a fast-developing technology for base and soil compaction quality control and acceptance. The primary objective of this project is to improve the process of accepting compacted materials to ensure quality, performance and durability using IC technology. Practical test protocols and specifications are being developed to improve the general quality and acceptance of compaction for subgrade, embankment, and base construction with available IC rollers.

NCHRP 10-84: Modulus-Based Construction Specification for Compaction of Earthwork and Unbound Aggregate

Earthwork and unbound aggregates are a significant portion of the construction of highway pavements and structures and play an important role in their performance. However, measurement of the dry density and moisture content of earthwork and unbound aggregates for construction control, while relatively straightforward and practical, does not provide as direct a connection between design and construction, as there could be if mechanical properties such as moduli were used. Several test methods and devices are available to determine the stiffness or modulus of earthwork and unbound aggregates in the field. Therefore, a rigorous modulus-based specification must provide criteria or limits related to long-term performance of the earthwork or unbound aggregate as well as to compaction at the time of construction. The objective of this research is in collaboration with the Louisiana Transportation Research Center and The University of Texas at Arlington to develop a straightforward, and well-defined modulus-based specification for compaction of earthwork and unbound aggregates that is based on field measurement of the stiffness or modulus and moisture content of the compacted earthwork, that can be correlated with design modulus values, and that is founded on a comprehensive review of the current literature on the long-term behavior of various soils and unbound aggregates in terms of the principles of unsaturated soil mechanics.

TxDOT IAC-NTP1: Assessing the Variability of Current Overlay Test Procedure

The main objective of the study was to investigate the sources of variability in the performance measures from overlay tests. The two main sources of variability, apart from material characteristics, are the specimen preparation process and the elapsed time between preparation and testing. A series of tests was conducted in accordance with Tex-248-F to quantify the OT variability in close collaboration with the TxDOT Flexible Pavement Branch: Construction Division from Austin, Texas. This study consists of testing samples at the Center for Transportation Infrastruc ture Systems (CTIS) asphalt laboratory at UTEP using two different OT systems. The resul ts obtained at UTEP will be compared with those carried on similar specimens at TxDOT Construction Division (CST). This study was performed in systematic approach to minimize the impact of variability introduced during specimen preparation

TxDOT IAC-NTP2: CTIS Tasked by TxDOT to Evaluate Interstate Highway 10 in El Paso

CTIS is assisting TxDOT with pavement evaluation of Interstate Highway 10 corridor in El Paso. CTIS staff are using ground penetrating radar (GPR) method to perform nondestructive evaluation of the IH10 to assess the structural health of the pavement and bridges. GPR method is an electromagnetic nondestructive testing method widely applied on bridge decks and pavements for evaluation of thicknesses, rebar arrangement and location, concrete deterioration and potential for delamination or debonding. The effort included testing on the bridge deck at Cotton Avenue. Another location of interest is a bonded concrete overlay section within the corridor. The team were locating debonded areas and trying to investigate areas where water is trapped in the concrete layers that can eventually lead to accelerated deterioration of pavement.

TXDOT 0-6679: Performance Life of Various Mixes in Texas

One of the important inputs into current pavement design programs is the performance lives of HMA mixes since they significantly impact the life cycle cost analyses and the ultimate selection of the HMA type., the estimated performance life of different HMA mixes (including the frequency of overlay) by the designers is currently subjective. The main goal of this project is to objectively recommend the most likely service lives of different mixes used in Texas as a function of the mix properties, type and quality of construction, pavement structure, frequency of preventive maintenance, traffic volume, and the environmental characteristics.

EPMPO: Development of a Sustainable Performance-Based Methodology for Strategic Metropolitan Planning Based on MAP-21​

A sustainable performance-based evaluation methodology with 26 performance measures has been developed for El Paso MPO. The methodology covers four planning scales: within community, community to community, community to region, and region to region. The implementation of this methodology will allow El Paso MPO to better achieve its strategic goals for the well-being of the community and the region.

Quantification of the Impact of Roadway Conditions on Emissions

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This project involves quantifying the impact of roadway conditions on vehicular emissions and developing detailed guidance to assist TxDOT in improving maintenance strategies to reduce these emissions. The researchers will quantify the vehicular emissions associated with different conditions of flexible pavement, continuously reinforced concrete pavement (CRCP), and jointed concrete pavement (JCP), and evaluate the effectiveness of different maintenance strategies in reducing emissions on these roadways. This research will demonstrate that roadway rehabilitation is an effective means of reducing vehicle emissions.

Seismic Testing for Track Substructure (Ballast and Subgrade) Assessment

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This project proposes to use seismic wave propagation principles (a non-destructive method) to develop a railroad track substructure (ballast and subgrade) condition assessment system. Currently there is no established tool or system available that quantitatively measures the mechanical properties of the layers comprising a track system. In cooperation with the Rail Transportation and Engineering Center at the University of Illinois at Urbana-Champaign and the University of Massachusetts at Amherst, a system for quickly, nondestructively, and quantitatively assessing the engineering properties of the track substructure (ballast and subgrade) is being developed. The resulting system will be used in conjunction with Ground Penetrating Radar (GPR) to not only measure engineering properties but also determine the cause(s) of the potential problem areas, i.e., degraded track or reduced performance.

FHWA DTFH61-12-R-00040: Pavement Structural Evaluation at the Network Level

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1) To assess, evaluate and validate the capability of the RWD and the TSD (and any other traffic speed continuous deflection (or other pavement response that can be reliably related to pavement structural condition) devices that may have been developed since these efforts) for pavement structural evaluation at the network level for use in pavement management application and decision making.

2) If one or more of the available devices are capable of meeting the above stated objective, to develop analysis methodologies for enabling their use in pavement management. If they do not have the capability to meet the objective, to develop recommendations to further develop promising device(s) and/or technologies.

TXDOT IAC-6658: Collection of Materials and Performance Data for Texas Flexible Pavements and Overlays

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TxDOT 0-6812: Updated Testing Procedures for Long Life Heavy Duty Stabilized Bases

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TxDOT is in the process of evaluating new approaches and laboratory test methods for characterization of the fatigue performance of the cement treated base layers. The new approach is required to be all inclusive for statewide application and incorporation into the new Mechanistic Empirical Design Guide (TexME). Three-point bending beam fatigue test is currently used for the determination of the modulus of rupture of the cement-treated mixes. This test proved to be impractical for lightly-stabilized systems as the specimen tends to disintegrate during transportation to the test setup. Additionally, discrepancies associated with specimen preparation and non-uniform density distribution in large samples were found to be an added concern that greatly jeopardizes the accuracy of the performance prediction models. Therefore, there is an urgent need for a simple and practical fatigue test that provides inputs to the TexME structural design program. This research project provides an alternative laboratory testing protocol for mechanistic characterization of the cement treated base layers to meet the need. This project will focus on identification, evaluation and validation of a practical laboratory testing protocol that will be implemented by TxDOT to characterize fatigue performance of the pavement structures with cement stabilized base layers.

TxDOT 464MITA047 IAC - FHWA Task 3e - EDC 2 National Deployment of Intelligent Compaction

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The main goal of this project is to collect necessary data for a comprehensive evaluation of the candidate intelligent compaction (IC) retrofit kits for compaction of hot mix asphalt (HMA), base, and subgrade layers. One of the key components of this project is two equipment rodeos. A test plan for conduction of the two rodeos is provided here. The test plan provides detailed information on installing and operating the IC retrofit kits on selected asphalt and soil rollers, performing side-by-side comparisons of retrofitted rollers and selected factory-supplied IC rollers, and implementing NDT spot tests (as well as sampling and coring if necessary) for correlation purposes. The main objectives of the equipment rodeos are the following items: - Demonstrating IC retrofit kit installation and operation to targeted DOTs - Identifying and addressing the potential challenges associated with retrofitting process and obtaining on-site GPS coordinates - Evaluating the proper installation of the retrofit kits with additional embedded geophones and installed accelerometers during the operation process - Establishing the variability of each specific IC roller as well as retrofitted rollers with respect to inherent field and materials variation, and - Investigating the correlation between selected NDT test results and IC data from retrofitted and factory installed IC kits.

Implementation of Improved Overlay Tester for Fatigue Cracking Resistance of Asphalt Mixtures

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