This paper investigates the effect of loading level and loading rate on the damage development and strength of asphalt mixtures. Indirect tensile creep tests with different loading levels and strength tests with three loading rates were performed at three low temperatures for ten mixtures. An acoustic emission (AE) system with eight recording channels was used to monitor the development of micro cracking in the specimens for both tests for one mixture. The experimental results show that test temperature has a significant effect on the behavior of the material. Data analysis from the creep test indicates that the creep loading level significantly affects the response of the tested material. The AE rate analysis shows that no actual damage develops when a creep load is less than 20 % of the strength and significant micro damage accumulates when the applied creep load is more than 30 % of the strength value. The loading rate was found to have a significant effect on the measured tensile strength even at a relatively low temperature, and the measured tensile strength increases with the increase of the loading rate for all the test temperatures considered in this study. However, this effect was found to be diluted with the decrease of the test temperature. The AE analysis indicates that a damage zone develops in both the creep and strength tests. The damage zone decreases with temperature decrease and increases with the increase of the loading level applied during the creep test. The damage zone obtained from the strength test was approximately equal to that from the creep testing with a loading level about 25-50 % of the strength value.

s stated in the House Bill 62 Transportation Budget in Brief, roughly 5 billion dollars is spent yearly on road pavement construction in the state of Ohio, with a significant chunk for maintenance. Moreover, maintenance activities and their associated costs are increased in the colder regions of the US where damages and distress on roadways are associated to the Low Temperature Cracking (LTC) phenomena or at least in combination with other distress like rutting and fatigue cracking. Thermally induced internal cracking is a mechanism that occurs under low temperature conditions. Akentuna et al. (2017) postulated that the differential in Coefficient of Thermal Contraction (CTC) values in asphalt binder and aggregate gives rise to thermally induced internal cracking at low temperatures. Owing to its potential significance and effect on LTC modeling, this study investigated the thermally induced thermal cracking phenomena using the Indirect Tensile (IDT) test. The IDT test was selected since it is the test procedure used in fracture property investigation in the AASHTOWare Pavement Mechanistic Empirical (ME) Design program for low temperature cracking modeling. In addition, a study on the effect of loading rate and temperature on asphalt mixtures during the ITS test was also investigated. Although thermally induced internal cracking was observed by Li et al. (2007) using the acoustic emissions test and Behnia et al. (2014) using the Disc-shaped Compact Test (DCT), its quantified effect has not been studied. The results garnered from this study validated the occurrence of thermally induced internal cracking, evidenced by significant reduction in IDT peak strengths and energy at peak stress to averaged magnitudes of 4% and 12% respectively. The second objective of this study on varying loading rate and temperature during the IDT strength tests proved that the standard test loading rate of 12.5mm/min rate was too fast and not representative of field loading rate. In addition, knowing that LTC could occur even at lower stress compared to the IDT strengths, ‘Creep to fail’ tests were performed to analyze the behavior of mixtures in such circumstances. Results showed that creep loads at extremely lower percentages of IDT strengths still fractured asphalt samples with output parameters offering valuable information on crack behavior under low temperature conditions. Time to fracture and crack speed parameters were shown to decrease 62% and increase 46% in thermally induced internal cracking samples.

Introduction and Research Approach -- Findings -- Interpretation, Appraisal, and Applications -- Conclusions and Recommendations -- References -- Appendixes.

Green and Intelligent Technologies for Sustainable and Smart Asphalt Pavements contains 124 papers from 14 different countries which were presented at the 5th International Symposium on Frontiers of Road and Airport Engineering (IFRAE 2021, Delft, the Netherlands, 12-14 July 2021). The contributions focus on research in the areas of "Circular, Sustainable and Smart Airport and Highway Pavement" and collects the state-of-the-art and state-of-practice areas of long-life and circular materials for sustainable, cost-effective smart airport and highway pavement design and construction. The main areas covered by the book include: • Green and sustainable pavement materials • Recycling technology • Warm & cold mix asphalt materials • Functional pavement design • Self-healing pavement materials • Eco-efficiency pavement materials • Pavement preservation, maintenance and rehabilitation • Smart pavement materials and structures • Safety technology for smart roads • Pavement monitoring and big data analysis • Role of transportation engineering in future pavements Green and Intelligent Technologies for Sustainable and Smart Asphalt Pavements aims at researchers, practitioners, and administrators interested in new materials and innovative technologies for achieving sustainable and renewable pavement materials and design methods, and for those involved or working in the broader field of pavement engineering.

Aging phenomenon of asphalt material exists in the course of mixing, spreading, and rolling of asphalt mixture, as well as the use in the asphalt pavement. The indirect tensile strength test was used to evaluate the performance of asphalt mixtures at low-temperature under different aging conditions. As compared with the results from the original short-term aging and the long-term aging asphalt mixtures, the results show that the original asphalt mixture cannot reflect the real performance of the asphalt mixture in the field. The short-term aging specimens are more sensitive than long-term aging specimens in evaluating the performance of the asphalt mixture at low temperature. Tests results also indicate that the consideration of aging during the evaluation of asphalt pavement performance is necessary.

This book forms the Proceedings of an International RILEM Symposium, the fourth in the series, on Testing of Bituminous Mixes in Budapest, Hungary, October 1990. The aim of the Symposium is to promote tests for the characterization, design and quality control of bituminous mixes which combine the best features of traditional and modern approaches. Among the topics covered are specimen preparation, tests with unique loading (Marshall test, uniaxial tension and creep tests etc), which are used for mix design or control of mechanical properties, and tests with repeated loading, which give information on fatigue, permanent deformation and moduli, especially for mix design.

The indirect tensile test is commonly used to evaluate crack and fatigue resistance of asphalt mixtures. However, laboratory tests are time-consuming and laborious in general. Numerical simulation provides a technical way for studying the mechanical behavior of asphalt mixtures. In this research, a laboratory test and discrete element method were used to explore the effects of temperature, air void content, loading rate, and the homogeneity of a mixture on the splitting strength of asphalt mixtures. For asphalt mixtures, a three-dimensional random modeling method and two-dimensional modeling method based on X-ray computed tomography and digital image processing were developed. Also, a homogeneity evaluation index based on ring segmentation was proposed. The results show that an increase in loading rate and decrease in temperature resulted in a significant increase in splitting strength. With an increase in voids, the splitting strength of an asphalt mixture decreased. The Pearson correlation coefficient indicates that there seems to be no clear connection between splitting strength and homogeneity, but there is a significant correlation between the homogeneity and differences in the splitting strength.