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The optimum asphalt content (OAC) in a hot-mix asphalt (HMA) is an important parameter that affects pavement performance and durability. To obtain it, it is essential to consider variables associated with the action of the climate and the rate of load application. The traditional way of obtaining the OAC through the Marshall test does not consider these variables. Additionally, this test is more appropriate to evaluate the performance of HMAs in high-temperature climates (mainly to evaluate rutting resistance) and does not consider the types of distresses that predominate in temperate and/or cold climates (e.g., fatigue cracking). This study analyzed the influence of asphalt binder content on the performance of an HMA by performing indirect tensile strength (ITS) and resilient modulus (RM) tests, considering temperatures of 10, 20, and 40 ºC, with load application rates of 10, 30 and 50 mm/min for the ITS test, and loading frequencies of 2.5, 5.0 and 10.0 Hz for the RM test. From the ITS test, the peak load (P), the slope at the inflection point (m), the stiffness (St), and the work of fracture (Wf) were obtained. The performance of the HMA based on these parameters was evaluated and an OAC was defined and compared with that obtained traditionally by the Marshall test. Additionally, these values were compared with the results obtained from resilient modulus (RM) tests. A mathematical correlation between the ITS and RM tests was reported. Temperature, speed of load application in the ITS test, and frequency of load in the RM test affected the performance of the HMA. P, ITS, St, Wf, and RM increased when temperature decreased and loading speed or frequency increased. The opposite was true for parameter m. For the HMA evaluated in the present study, the results show that the OAC obtained from ITS and RM tests is 0.5% higher than that obtained from the Marshall test. In other words, HMA design methods should include ITS and RM tests to help reduce susceptibility to cracking in temperate climates and rutting in high-temperature climates. It's suggested to conduct similar studies using different aggregates, asphalts, and gradations. • The effect of asphalt binder content, temperature, and loading rate on an HMA was studied by ITS and RM tests. • The fracture properties of an HMA were evaluated in the ITS test. • The OAC obtained from the Marshall test differs from the ITS and RM tests. • There is a mathematical correlation between the results of the ITS and RM tests. • For temperate climates, the design of HMAs is recommended by performing Marshall, ITS, and RM tests together. [ABSTRACT FROM AUTHOR]

Two grades of paving asphalt, AC 80-100 and AC 60-70, were studied to determine changes in their physical and chemical properties caused by exposure to water. This experimental study’s primary hypothesis is that the interaction between the water oxygen molecules and asphalt, known as oxidation, changes the asphalt properties, resulting in increased damage from mechanisms such as humidity and aging for mixtures in service. The chemical responses of both asphalts were measured, and the flow activation energy concept was used to understand the resulting changes in the physical and rheological properties after immersion in distilled water for one year. [ABSTRACT FROM AUTHOR]

Highlights: [•] UV radiation produces either atomic ionization or free radicals within asphalts. [•] Sara fractions change its composition due to aging process. [•] Rheological behavior depends on chemical changes in asphalts by asphaltenes growth. [•] MSCR test is a good tool to observe the behavior of deformation asphalt after aging. [•] A period after STA and before LTA produces recovery on penetration, ductility and G*. [ABSTRACT FROM AUTHOR]

• HMA containing several contents of RCA from different sources were studied. • Results showed that the mixes with RCA exhibited a similar behavior to that of conventional HMA. • HMA mix-design with coarse RCA fraction satisfied the requirements of national specifications. • Performance of mixes with RCA was found to be highly dependent on the source and dosage of RCA. The waste generated by the construction industry generally has an undesired negative impact on both human and animal life as well as the environment. Among these wastes, recycled concrete aggregate (RCA), due to its good residual physical, mechanical, mineralogical, and chemical properties, has attracted promising potential for re-use and incorporation in the construction of new infrastructural elements. These infrastructure applications include construction of sidewalks, curb and gutters, subbase/base layers, and/or as a partial replacement of natural aggregates (NA) in the production of hot mix asphalt (HMA) mixtures. In this laboratory study, experimental research work was conducted to evaluate the influence of RCA on the mechanical properties and performance of RCA modified HMA mixtures against a control HMA mixture without any RCA. RCAs were obtained from two different concrete sources, namely: (a) one from the demolition of a building (RCAB), and (b) another one from the rehabilitation of a Portland cement concrete pavement (RCAP). Both NA and RCA were characterized taking into account physical and mechanical properties. HMA mixtures were produced using the Marshall mix-design method by replacing 0.0% (control), 15%, 30%, and 45%, respectively, of the coarse NA fraction with RCA. Thereafter, laboratory testing (i.e., Scanning Electron Microscopy [SEM], resilient modulus, indirect tensile strength, etc.) including material property characterization and performance evaluation were conducted on HMA samples. Overall, the laboratory test results showed that the RCA modified mixtures exhibited a similar behavior to conventional HMA mixtures, but with greater environmental benefits and potential cost savings through the recycling and reuse of waste concrete aggregates. However, it was observed that the laboratory performance of RCA modified mixtures is strongly dependent on the RCA source and dosage, with RCAP exhibiting superior performance over RCAB. HMA mixtures produced with RCA provided higher optimum asphalt-binder content (OAC) than that of mixes with NA. [ABSTRACT FROM AUTHOR]