Manik Barman

Modeling the dynamics of asphalt-roller interaction during compaction

AbstractCompaction is one of the important steps in pavement construction that significantly affects the quality and long-term performance of asphalt pavement. Compaction of asphalt pavement is inf...

Accounting for Temperature Susceptibility of Asphalt Stiffness When Designing Bonded Concrete Overlays of Asphalt Pavements

AbstractA bonded concrete overlay of asphalt (BCOA), also known as whitetopping, is a thin concrete overlay placed upon a distressed asphalt pavement. The asphalt-resilient modulus is kept constant in current BCOA design procedures. This practice results in an underestimation of the damage as compared to when the hourly temperature variation of the asphalt is considered. The framework to establish an equivalent asphalt modulus involves generating a database of hourly middepth asphalt temperatures. This database should include hourly temperatures for different BCOA structures and a large range of geographical locations representing different climatic conditions. The hourly middepth asphalt temperatures are then used to generate hourly asphalt moduli using master curves. Through fatigue equivalency, the equivalent asphalt moduli are calculated for each month. In order to establish the relationship between the asphalt modulus and middepth temperature, the United States was divided into seven different zones ...

Characterization of Load Transfer Behavior for Bonded Concrete Overlays on Asphalt

A bonded concrete overlay on asphalt (BCOA) is a rehabilitation method for moderately distressed asphalt pavements by relatively thin plain cement concrete or fiber-reinforced concrete slabs. The joint load transfer behavior for BCOAs plays a significant role in the long-term performance. Poor load transfer across the joints of the concrete slabs initiates debonding of the asphalt layer from the concrete slabs, which promotes the development of corner cracks or longitudinal cracks. However, because of the tediousness involved in characterizing the joint load transfer behavior of BCOAs, this important aspect is not accounted for in many available mechanistic–empirical BCOA design procedures. The influences of joint load transfer behavior on the performance of BCOA are discussed. The joint load transfer behavior for BCOAs with 1.52- × 1.83-m (5- × 6-ft) slabs and 1.22- × 1.22-m (4- × 4-ft) slabs is analyzed with the finite element method. The load transfer contributed by the asphalt layer, as well as the concrete slab, is characterized as a function of the BCOA design features. Finally, a method is proposed to determine the nondimensional joint stiffness (AGG*) for BCOAs as a function of the structural design features of the pavement section. The AGG* is significant in that it is the factor commonly used to characterize joint load transfer behavior when pavements are designed with a mechanistic-based design approach.

Use of Intelligent Compaction in Detecting and Remediating Under-Compacted Spots During Compaction of Asphalt Layers

Under-compaction of asphalt layers results in premature distresses like rutting, localized depressions and pot-holes. Over-compaction may crush the aggregates which can result in unstable asphalt mixes. It is therefore highly important to achieve the required air voids or relative density (6–8% air voids or 92–94% relative density). Real-time monitoring of the relative density can certainly be helpful in achieving the required relative density. The traditional quality control procedure, which involves collecting cores and conducting volumetric analysis on them, does not provide any measure of the air voids or relative density level during the compaction itself, thus under-compacted spots, if any, remain undetected. Intelligent compaction methods are able to continuously monitor the air voids or density of asphalt layers during the compaction process. The University of Oklahoma has developed an intelligent compaction analyzer (ICA). The ICA is based on the hypothesis that the vibratory roller and the underlying pavement form a coupled system whose response during compaction is influenced by the stiffness of the pavement layers. The ICA is capable of generating as-built maps providing information on coverage and quality of compaction of the compacted asphalt layers. This paper discusses the principle of ICA, and its application in measuring the density of asphalt layers. Results from one demonstration are included in this paper. The ICA measured densities were validated by comparing them with densities obtained from cores. It was found that the ICA measured densities and core densities correlated well with an R2 between 0.85 and 0.93. Also, t-test conducted with the ICA-estimated densities and core densities verified that the difference between the above-mentioned two types of densities are insignificant at 95% confidence level. ICA was able to detect several under-compacted spots which were then remediated with additional roller passes. The application of the ICA certainly helped in achieving higher and uniform density throughout the test section.

Influence of interface bond on the performance of bonded concrete overlays on asphalt pavements

AbstractBonded concrete overlays on asphalt pavement (BCOA) offer a rehabilitation method for moderately distressed asphalt pavements. A performance review of the BCOA projects constructed in diffe...

Quality control of subgrade soil using intelligent compaction

Intelligent Compaction (IC) of subgrade soil has been proposed to continuously monitor the stiffness of subgrade during its compaction. Modern IC rollers are vibratory compactors equipped with (1) an onboard measuring system capable of estimating the stiffness of the pavement material being compacted, (2) Global Positioning System (GPS) sensor to precisely locate the roller, and (3) an integrated mapping and reporting system. Using IC, the roller operator is able to evaluate the entire subgrade and address deficiencies encountered during compaction. Continuous monitoring of quality during construction can help build better quality and long-lasting pavements. However, most of the commercially available IC rollers report stiffness in terms of Original Equipment Manufacturer (OEM) specified indicator, known as Intelligent Compaction Measurement Value (ICMV). Although useful, additional tests are required to establish the correlation between these ICMV values and the resilient modulus of subgrade (Mr). Since the mechanistic design of the pavement is performed using Mr, it is important to know if the design Mr is achieved on the entire subgrade during compaction. This paper presents a systematic procedure for monitoring the level of compaction of subgrade in real time using intelligent compaction (IC). Specifically, the Intelligent Compaction Analyzer (ICA) developed at the University of Oklahoma was used for estimating the modulus of the subgrade. Results from two demonstration studies show that the ICA is able to estimate subgrade modulus with an accuracy that is acceptable for quality control activities during the construction of pavements.

Intelligent Compaction of Stabilized Subgrade of Flexible Pavement

The long-term performance of a flexible pavement largely depends on the compaction level achieved in different layers during construction. Traditionally, the compaction level of the subgrade is monitored through spot checking of moisture content and dry density at some discrete points. However, this type of quality control work does not cover the entire pavement and may leave under-compacted areas. These under-compacted areas could likely lead to early failure of the pavement structure. Therefore, it is necessary to develop a real-time compaction monitoring tool that can provide an accurate measurement of the compaction level of the entire pavement. Such measurements could be used to identify and remediate under- compacted areas and provide adequate support to asphalt layers constructed on top of the prepared subgrade. The application of the Intelligent Compaction Analyzer (ICA) for real-time monitoring of compaction of a stabilized subgrade is addressed in this paper. Four case studies demonstrating the successful application of the ICA are included. The compaction level of the stabilized subgrade was monitored in terms of ICA density and modulus. In each case study, it was found that ICA could estimate the compaction level with a reasonable accuracy. It was also found that the ICA modulus and nuclear density gauge (NDG) measured density exhibits a good correlation with R 2 equal to 0.73.