Accelerated Pavement Testing

Abstract: For a long time, standard Egyptian penetration grade 60/70 bitumen which is actually equivalent to (PG64-22), used to provide a satisfactory ACP performance with current combination of (18t IWL ,1.35 MPa tire pressure). However, by the recent changing the bitumen fractional composition due to bitumen’s origin or/ and different refining techniques, many shear related distresses has been reported. Moreover, top-down cracks (TDCs) have been also observed as one of the most surface distresses in this perspective. Moreover, creep has been reported also in (ACP) especially, in southern latitude airports, where surface layer is exposed excessively to high temperature ambient. In this decade, the criterion of admissible octahedral shear stresses (OSSs) in the flexible surface layer, has been used successfully as a judicious design tool, for the accurate assessment of ACP performance. Consequently, the aim of this work was to study the state of art of using bitumen products through different bitumen types modified by recycled low density polyethylene (LDPE), and its impact on the OSS resistance of ACP surface layer.
Keywords:  Airfields AC pavement distresses, Enhanced PG LPDE modified binder, Octahedral shear stress. 
Title: Improving the bitumen in HMA to resist the effect of Octahedral Shear Stresses on asphalt pavement surface layer
Author: Ahmed Eraky, H. S. Ayoub, Omar Osman, Mohamed E. Ouf , Abdel Zaher E.A. Mostafa
International Journal of Civil and Structural Engineering Research 
ISSN 2348-7607 (Online)
Vol. 10, Issue 1, Month: April 2022 - September 2022
Page: (1-13)
Published Date: 01-April-2022
Full Research Article Available at: https://www.researchpublish.com/papers/improving-the-bitumen-in-hma-to-resist-the-effect-of-octahedral-shear-stresses-on-asphalt-pavement-surface-layer
Publisher: Research Publish Journals
Website: www.researchpublish.com

The University of California, through the UC Pavement Research Center (UC-PRC) located at Davis and Berkeley, started conducting Accelerated Pavement Testing (APT) research in 1994. This research is conducted for the California Department of Transportation, which purchased 2 Heavy Vehicle Simulators (HVS) in 1994. Since then a significant amount of APT-related research has been carried out. As part of good business practice, and for continuous improvement of this research program, there is a need to identify, analyze, and quantify the direct and indirect benefits obtained from HVS testing. This paper provides a historical overview of previous benefit assessment investigations. Furthermore, it highlights the findings of a pilot study aimed at defining an appropriate method of measuring the impact of and benefits to be gained from HVS testing by the UC-PRC. This approach has also been tested through evaluation of a recent HVS study in California. The pilot study included qualitative a...

This study presents a comparison between the fatigue performance of field cores obtained from different layers (top and bottom) and laboratory produced–laboratory compacted specimens. The field cores were obtained from the Accelerated Pavement Testing (APT) facility at Turner-Fairbank Highway Research Center (TFHRC), located in McLean, Virginia, USA. Uniaxial push-pull (compression-tension) fatigue tests were conducted on samples obtained from the top 50 mm and the bottom 50 mm layers of 100 mm thick asphalt pavements. The samples were obtained by horizontally coring slabs extracted from six APT lanes. The damage characteristic curves (i.e., C versus S curve of the viscoelastic continuum damage (VECD) theory) and the fatigue lives of the field cores were compared with those of the laboratory specimens. The experimental test results and the subsequent analysis findings revealed comparable damage characteristic curves and fatigue lives for the top and bottom field specimens; meanwhile, the field and laboratory specimens exhibited different damage characteristic curves and fatigue lives.

The South African road network is severely impacted by the high costs associated with upgrading, maintaining and constructing road infrastructure in conjunction with the shortage of good quality construction materials. The Council for Scientific and Industrial Research (CSIR) has conducted extensive research on an innovative, cost-effective bituminous stabilising agent known as Nano-Organosilane Modified Emulsions (NMEs). These emulsions allow road engineers to design stabilised base and subbase layers using marginal materials which are normally considered unusable for road construction. For the purpose of determining the potential performance of NMEs, extensive advanced laboratory evaluations have since been conducted, most recently in the form of triaxial testing. This paper outlines the results and findings from both monotonic and dynamic triaxial testing conducted on NME materials, and draws correlations with Heavy Vehicle Simulator (HVS) test results. Compared to standard materials and designs, the initial results on the use of NMEs as a stabilising agent in road bases and subbases has since showed excellent performance and cost savings.

The Midwest States Accelerated Pavement Testing Pooled Fund Program, financed by the highway departments of Missouri, Iowa, Kansas, and Nebraska, has supported an accelerated pavement testing project to compare the performance of stabilized clayey embankment soil when portland cement, fly ash, lime, and a commercial product were used as stabilizing agents. The project aimed to determine if lime stabilization, the most common method used in Kansas for the chemical stabilization of embankment soils, is the optimum method. The experiments were conducted at the Civil Infrastructure Systems Laboratory of Kansas State University. The test program consisted of constructing four pavement structures and subjecting them to full-scale accelerated loading. The study indicated that cement and lime are the most effective stabilizers. These stabilizers resulted in lower vertical compressive stresses at the top of the subgrade and lower rut depth at the pavement surface than the stresses and depth ...

Upgrading, maintenance and rehabilitation of road infrastructure is expensive, especially in view of the growing scarcity and cost of suitable road building materials. In areas with high mica content and secondary minerals such as smectite in the natural materials, stabilisation with cement is not viable. The Council for Industrial and Scientific Research of South Africa has embarked on a research programme to evaluate the performance of substandard materials improved with anionic nano-silane modified bitumen emulsions for use in base and subbase layers. This work comprises laboratory testing as well as Accelerated Pavement Testing using the Heavy Vehicle Simulator (HVS). The results of a full-scale HVS test on a light pavement as well as initial analysis on a medium traffic road are discussed. It has been shown that stabilisation of available substandard materials using an anionic nano-silane modified bitumen emulsion compared with the standard approach of importing high quality crushed aggregate can lead to savings as high as 40%–50% for equivalent performance. In addition, there was also a significant reduction in construction effort and time.