Mechanical Properties Of Hot Mix Asphalt Research Articles

A Review Study on the Improving the Hot Mixture Asphalt Properties by Using Different Types of Polymers as Additive for Asphalt Material

By integrating the design of high-performance material with solid structural design, flexible pavement performance can be increased and the service life extended. In the context of creating highways the topic of asphalt polymer modification and the incorporation of polymers in asphalt material by mechanical mixing or chemical reaction, has received substantial scholarly coverage. A wide range of polymers types are used in the method of changing asphalt material and subsequently enhancing hot mixed asphalt. The main objective of this paper is to review prior research on employing polymer materials to develop the qualities of asphalt cement and hot mixed asphalt. This study reviews three different types of polymers. These polymers are Styrene-butadiene-styrene (SBS), polytetrafluoroethylene (PTFE), and polyvinyl chloride polymers (PVC). According to earlier studies in this area, these polymers are elastomers and plastomers that are utilized to enhance the mechanical properties of hot-mix asphalt while also increasing the stability, elasticity, and stiffness of asphalt binders. The overall performance of asphalt pavement can be achieved by reducing the possibility of rutting in the summer and cracking in the winter.

Effects of nominal maximum aggregate size and compaction effort on the mechanical properties of hot-mix asphalt (HMA)

Considering the potential rutting distress and excellent fatigue performance of small nominal maximum aggregate size (NMAS) mixes, this study explored the function of number of design gyrations (Ndes) variable in the design, and attempted to balance the high-temperature and fatigue performance of these materials. Therefore, one experimental group (9.5 mm NMAS mixes under Ndes = 80 cycles) and three control groups (9.5 mm/13.2 mm/16 mm NMAS mixes under Ndes = 60 cycles) were designed. The uniaxial penetration shear test, the uniaxial compressive modulus test, the British pendulum test, the indirect tensile cracking test, and the indirect tensile fatigue test were then conducted. It can be found that through increasing the Ndes by 20 cycles, the rutting resistance of 9.5 mm NMAS mixes improved significantly, and can reach the same level as that of 13.2 mm NMAS mixes. Moreover, under this design, the 9.5 mm NMAS mixes can still perform a longer fatigue life than 13.2 mm NMAS mixes. In addition, increasing the Ndes also helps to improve the cracking resistance and dynamic modulus of these materials. Specifically, with the increase of Ndes by 20 cycles, the fracture energy and dynamic modulus of 9.5 mm NMAS mixes can improve by almost 516 J·m−2 and 1860 MPa (10 Hz and 21 °C), respectively. These results may indicate that selecting a suitable Ndes is helpful to balance the properties of small NMAS mixes.

Characteristics of Recycled Mineral Fillers and Their Effects on the Mechanical Properties of Hot-Mix Asphalt When Used as Limestone Filler Replacements

AbstractThis study was designed to analyze the characteristics of two recycled fillers, hollow concrete block (HCB) powder and brick powder (BP), and to assess their respective impacts on the mecha...

Effect of clay and lime nano-additives on the freeze–thaw durability of hot mix asphalt

Durability of hot mix asphalt (HMA) against freeze–thaw cycles is mostly related to bitumen-aggregate adhesion. Improving the bonding quality between aggregates and bitumen would reduce the HMA moisture susceptibility and increase its durability. This study focused on the effects of nano-additives, including nano-clay (NC) and nano-lime (NL) on the durability of HMA. Limestone and granite aggregates were used to prepare the HMA specimens. Nano-additives were blended with 60/70 penetration grade bitumen at different rates, including 3%, 6%, and 9% by weight of bitumen. The mechanical properties of HMAs were determined using indirect tensile strength (ITS) and resilient modulus tests before and after one, three, and five freeze–thaw conditioning cycles. Afterwards, the moisture damage of mixes were evaluated using the surface free energy (SFE) concept. The SFEs of unmodified and modified bitumens were measured using the Wilhelmy plate test. Likewise, the SFEs of aggregates were evaluated by a universal sorption device procedure. Based on the results obtained, the addition of proper NC and NL content will enhance the tensile strength and resilient modulus ratios. The optimum NC and NL contents were determined as equal to 3% and 6%, respectively. The difference between the bitumen-aggregate and water-aggregate SFEs showed peak points, which were obtained at the optimum additive content. These peak points were mostly in accordance with the peak of ITS and resilient modulus tests before and after conditioning cycles.

Mechanical properties of hot-mix asphalt made with recycled concrete aggregates coated with bitumen emulsion

The incorporation of recycled concrete aggregates (RCA) in hot-mix asphalt (HMA) could be a way to promote sustainable construction. To date, several investigations have examined the use of this type of waste material in HMA. Several researchers have observed that due to the action of water, the use of this material proved to have insufficient durability. In this investigation, a laboratory characterisation of HMA made with RCA from construction and demolition waste (CDW) for base layers in road pavements was conducted. Percentages of 5%, 10%, 20% and 30% of RCA in place of natural aggregates were analysed. To improve the water resistance of the mixes, the RCA were coated with 5% of bitumen emulsion prior to the mixing process. The results indicated that the mixes comply with the Spanish water resistance specifications required for base layers. The stiffness, permanent deformation and fatigue of the mixtures were also studied. The results indicated that HMA made with RCA coated with bitumen emulsion exhibited mechanical properties similar to those obtained for conventional mixtures.

Investigation of Mechanical Properties of Short- and Long-Term Aged Asphaltite Modified Asphalt Mixtures

AbstractIn this study, the effects of asphaltite and long-term aging (LTA) on the mechanical properties of hot-mix asphalt were investigated. The asphaltite entrained as filler at five different proportions into the hot-mix asphalt samples, and the obtained results were compared against the control mixtures. The pure and asphaltite-containing compacted mixtures were exposed to LTA in an oven. Marshall stability, resistance to moisture-induced damage, and resistance to crack propagation tests in accordance with the principles of elastic-plastic fracture and linear-elastic fracture mechanics were carried out on the mixtures. It was determined that the optimal proportion of asphaltite usage as filler with respect to volumetric design is 3% by weight. The test results demonstrated that asphaltite use enhances resistance against permanent deformation, moisture-induced damage, and crack propagation, especially at normal temperatures, albeit at the cost of causing the hot-mix asphalt to exhibit a more brittle be...

Impact of Polypropylene Application Method on Long-Term Aging of Polypropylene-Modified HMA

The effect of polypropylene application method on long-term aging of hot mix asphalt (HMA) was investigated. Three different application methods were considered within this paper, namely, the coating method (where aggregate surface was coated with polypropylene), the dry method, and the wet method. Constant polypropylene content of 0.7% by weight of total mix was adapted. Laboratory aging program was set up to simulate the aging process of asphalt pavement occurred in the field. The mechanical properties of aged and unaged mixtures prepared using the three different polypropylene application methods were evaluated based on Marshall quotient, the indirect tensile strength, fracture energy, and unconfined compressive strength. Experimental testing has revealed the enhancement in the mechanical properties of HMA when polypropylene was added. The polypropylene additive has managed to counteract the effect caused by long-term aging of HMA. A comparison between the three polypropylene application methods indicated that the coating method has caused a considerable improvement in the indirect tensile strength and fracture energy of HMA under aged and unaged conditions. Marshall quotient and compressive strength of tested mixtures have shown less dependency on the polypropylene application method.

Precision of Shear Tests in Evaluating Asphalt Mixtures

Various methods exist to measure the mechanical properties of hot-mix asphalt (HMA). To be useful such a test not only must measure a property that controls performance but also must be repeatable. The Strategic Highway Research Program developed tests with the Superpave® shear tester that have been shown to be related to HMA performance. To date, repeatability has not been quantified. The results of a repeatability study for the measurement of shear stiffness (frequency sweep) and of permanent shear strain (repeated-load, constant-height testing) are reported.