Comparison of Stress Fields near Longitudinal Construction Joints of Tied and Doweled Sections in Portland Cement Concrete Pavements

In Portland cement concrete (PCC) pavements, tie bars are commonly used at longitudinal construction joints (LCJs) to prevent the lanes from separating. Meanwhile, the increase in multiple lanes due to greater traffic volumes has raised concerns about potential longitudinal cracking; this has led to the use of dowel bars instead of tie bars at LCJs. However, there is a paucity of studies focused on the comparison between the behaviors of concrete pavement based on the restrained conditions provided by tie and dowel bars at LCJs. In this study, we investigated the effects of the placement of tie and dowel bars at LCJs on the potential for longitudinal cracking in response to the increase in concrete stress that may occur when the lanes are tied together in PCC pavements. Field testing verified that the variation in concrete strain was more restrained in the case of a tie bar than a dowel bar, whereas it resulted in higher stress in the concrete element in the tie bar section. However, the use of dowel bars caused more movement in the transverse direction at LCJs as compared with tie bars. Thus, our results indicate that using dowel bars reduces the potential for longitudinal cracking; however, it may increase the potential for lane separation.

Long-Term Effects of Subsurface Drainage on Performance of Asphalt Pavements

This study investigated the effects of subsurface drainage on the long-term performance of pavements. The Specific Pavement Study 1 (SPS-1) experiment of the Long-Term Pavement Performance Program (LTPP) was selected to extract performance data. Four types of cracking, rut depth, and International Roughness Index (IRI) were used as the performance indicators. Other relevant factors affecting the pavement performance were also considered: surface thickness, base type, base thickness, subgrade soil classification, total thickness, age, and climatic conditions. The significant factors to long-term performance were identified using two methods: exploratory data analyses and mixed-effects models (MEMs). Results from the analyses showed that drainage only substantially affected the transverse cracking (TC) and rutting and had little effect on the other performance indicators. Sections in the dry and non-freeze region had the best riding quality and exhibited the least alligator cracking, non-wheelpath longitudinal cracking (NWPLC), and TC, but this climatic condition worsened the wheelpath longitudinal cracking (WPLC). The use of drainage in sections from the wet-freeze (WF) region significantly retarded the development of distress. For drained sections, the base comprising an asphalt-treated base over a permeable asphalt-treated base (PATB) better sustained the smoothness and resisted rutting. For undrained sections, the asphalt-treated base was a superior alternative. Sections on sites with fine subgrade showed less WPLC, NWPLC, and TC, while those on coarse subgrade sites showed less alligator cracking and better riding quality. Sections on sites with fine subgrade showed less WPLC, NWPLC, and TC, while those on coarse subgrade sites showed less alligator cracking and better riding quality.

Investigation of Longitudinal Cracking in Widened Concrete Pavements

Widened slabs, widely employed in many US states in concrete pavements, have suffered from unexpected longitudinal cracks. These cracks suddenly appeared within 0.60 m to 1.20 m from widened slab edges and could be detrimental to the long-term pavement performance. The primary objective of this study was to identify possible causes for such longitudinal cracking observed on widened concrete pavements. Both field investigation and Finite Element Analysis were performed. Degrees of curling and warping were measured using a Terrestrial Laser Scanner. Concrete cores were also extracted to achieve a better understanding of how the cracking had developed. Field survey and numerical simulation results indicate that such longitudinal cracks could be primarily caused by a combination of excessive traffic loads, a high degree of curling and warping, inadequate support from underlying layers, pavement ageing, and skewed joints. It was also found that 4.30 m widened slabs coupled with tied Portland Cement Concrete shoulders outperformed others in terms of producing less cracking, even when they had experienced higher levels of truck traffic. The sites constructed in late afternoons also showed significantly less longitudinal cracks.

Prediction of Longitudinal Cracking of Asphalt Pavements

Longitudinal cracking is one of the major structural distresses of asphalt pavement. These cracks appear on the pavement along the direction of moving traffic. This study makes an attempt to predict the extent of longitudinal cracking based on three parameters which are: asphalt binder content, traffic load repetitions and asphalt stiffness modulus. For the study, the data has been used from Long Term Pavement Performance (LTPP) database. Linear Least Square (LLS) regression method is employed to model the observed trends between the longitudinal cracking and the three parameters. The results of the analyses has shown that longitudinal cracking vary linearly with respect to each parameter. It is observed that (i) longitudinal cracking decreases linearly with increase in percentage asphalt binder content in asphalt concrete (ii) longitudinal cracking increases linearly with increasing traffic load repetitions and (iii) longitudinal cracking decreases linearly with increase in stiffness modulus of asphalt concrete.

Influence of Temperature on the Longitudinal Cracking in Multipurpose Precast Concrete Sleepers Prior to Their Installation

Prestressed monoblock railway sleepers are concrete elements with almost no reinforcement apart from the prestressing wires, which makes them very sensitive to any stress variation that can induce tensile stresses. In recent years, severe longitudinal cracking has been observed in a number of sleepers in hot regions of Spain, even before these elements were put in service. This work studies the problem while considering the thermal variation as the main factor affecting this cracking phenomenon. A non-linear static load-step analysis is applied on a non-linear finite element model to reproduce the problem and, after its experimental validation, the influence of three design parameters of the sleepers are studied: the nature of concrete aggregates, the dowel thickness, and the dowel material. The results show that all these three parameters may have significant influence on the problem, with the dowel material being the most important parameter. When the dowels are made of a material with a high elastic modulus and a high thermal expansion coefficient, the crack opening induced by a realistic thermal variation can reach significant values and result in longitudinal crack propagation. The changes of humidity are not considered in this study because they are beyond the scope of this work.