Comparative Study on Complex Modulus and Dynamic Modulus of High-Modulus Asphalt Mixture

In the French high-modulus asphalt mixture design system, the complex modulus of the mixture under the conditions of 15 °C and 10 Hz is taken as the design index. However, in China, the dynamic modulus under the conditions of 15 °C, 10 Hz, 20 °C, 10 Hz and 45 °C, 10 Hz was taken as the stiffness modulus index of high-modulus asphalt mixture. The difference in modulus values between the two systems caused the pavement structure layer to be thicker and the construction cost to be higher in China. In order to find out the appropriate modulus value of high-modulus asphalt mixture suitable for China’s modulus parameter conditions to better carry out the reasonable design and evaluation of high-modulus asphalt mixture in China, the modulus of four types of high-modulus asphalt mixtures under the two systems through the two-point bending complex modulus test of the CRT-2PT trapezoidal beam and the SPT uniaxial compression dynamic modulus test were analyzed in this paper. Under the premise of meeting the stiffness modulus index of the French high-modulus asphalt mixture, the relationship conversion models between the dynamic modulus and complex modulus of high-modulus asphalt mixture under different temperatures were established. According to the conversion models, the design evaluation value range of dynamic modulus suitable for China’s condition was recommended. It is recommended that the dynamic modulus of China’s high-modulus asphalt mixture at 15 °C and 10 Hz is not less than 16,000 MPa, the dynamic modulus at 20 °C and 10 Hz is not less than 14,000 MPa, and the dynamic modulus at 45 °C and 10 Hz is not less than 2500 MPa. Five kinds of high-modulus asphalt mixtures used in actual road engineering were tested to verify the reliability of the recommended dynamic modulus values based on the modulus conversion model, and the results are consistent with the recommended value range of the model.

SUPERPAVE design mixture performance evaluation using Epolene modifier for cold semi-arid climatic region of Saudi Arabia

Purpose: To evaluate the superpave design performance using Epolene (EE-2) as modifier, since SUPERPAVE design is a modified and sophisticated aspect as compared to previous mix design for asphalt mixtures. This is primarily due to the fact that superpave design mix also takes into consideration properties of materials beside asphalt. Design/methodology/approach: This study was conducted using Epolene (EE-2) as modifier in order to evaluate the performance of SUPERPAVE suitability for construction of roads in Alfaraa campus (King Khalid University) Abha, in Asir Province of Saudi Arabia. Glow number test, dynamic modulus test and indirect tensile strength test were conducted to evaluate the performance of EE-2 modifier against the control mixture. Findings: The mixture modified with EE-2 gave better performance in terms of temperature-based performance and resistance to moisture damage. Also, larger values of E*/sinφ were obtained for EE-2 modified mixture at various loading frequencies and temperature in comparison to control mixture. Research limitations/implications: The Epolene modifier successfully enhances and improves the SUPERPAVE mixture performance. Further studies are required to evaluate the performance of EE-2 modifier at much lower temperature ranges. Practical implications: The results of the study allow us to recommend the investigated asphalt mixture for applied for the construction of roads in the Alfaraa (new campus of King Khalid University), Abha, Asir province, Saudi Arabia. Originality/value: A modified asphalt mixture has been proposed that has better performance at higher and lower temperatures. The developed asphalt mixture is more resistant to moisture damage than the compared to control mixture.

Rutting Performance of Semi-Rigid Base Pavement in RIOHTrack and Laboratory Evaluation

Through a simple performance dynamic modulus test (SPT), standard rutting test, Hamburg rutting test, French rutting test and asphalt pavement analyzer rutting test, the rutting resistance of asphalt mixtures in the middle and lower courses of three semi-rigid base asphalt pavement of Beijing full-scale test track road in China was evaluated. The test results show that the rutting resistance of asphalt mixtures of the middle and lower courses can be greatly improved by using low-grade asphalt, especially 30# asphalt. The rutting resistance of SBS modified asphalt mixtures is also better. The SPT dynamic modulus test can indirectly characterize the rutting performance of the asphalt mixture. The rutting test results of a laser road detection vehicle and 3 m ruler show that the asphalt grade has a significant impact on the rutting performance of semi-rigid base asphalt pavement. Compared with 70# asphalt used in the middle and lower courses, the rutting resistance of the pavement structure can be improved by more than 20%. The result also show that the APA rutting test results can closely characterize the full-scale test track results, which is an optimal test method for evaluating the rutting performance of semi-rigid base asphalt pavement. The research results can provide a theoretical basis and reference for the rational design and rutting evaluation of semi-rigid base asphalt pavement.

Experimental studies on the dynamic viscoelastic properties of basalt fiber-reinforced asphalt mixtures

To study the influence of basalt fibers on the viscoelastic mechanical properties of asphalt concrete (AC) mixtures, unconfined compressive dynamic modulus tests were performed on styrene–butadiene–styrene (SBS)-modified AC mixtures reinforced with various contents of basalt fibers ranging from 0.2 to 0.5% by weight at five temperatures and six load frequencies, and the dynamic moduli and phase angles of the mixtures were measured. Compared with the test results of the control mixture (with no basalt fibers), the data show that the high-temperature dynamic modulus of the mixtures initially increases and subsequently decreases with increasing fiber content and reaches its maximum value when the basalt fiber content is 0.3%, while the low-temperature dynamic modulus decreases monotonically with increasing fiber content. Furthermore, the phase angle of the mixtures initially decreases and later increases with increasing fiber content and reaches its minimum value when the basalt fiber content is 0.3%. These behaviors indicate that the addition of basalt fiber improves the high-temperature rutting resistance and low-temperature cracking resistance of the SBS-modified AC mixtures. In addition, the results of the wheel rut test exhibit a good correlation with the results of the dynamic modulus test, revealing the reliability of the dynamic modulus test for evaluating the high-temperature rutting resistance of basalt-fiber-reinforced AC mixtures.

The Discrete and Continuous Retardation and Relaxation Spectrum Method for Viscoelastic Characterization of Warm Mix Crumb Rubber-Modified Asphalt Mixtures

To study the linear viscoelastic (LVE) of crumb rubber-modified asphalt mixtures before and after the warm mix additive was added methods of obtaining the discrete and continuous spectrum are presented. Besides, the relaxation modulus and creep compliance are constructed from the discrete and continuous spectrum, respectively. The discrete spectrum of asphalt mixtures can be obtained from dynamic modulus test results according to the generalized Maxwell model (GMM) and the generalized Kelvin model (GKM). Similarly, the continuous spectrum of asphalt mixtures can be obtained from the dynamic modulus test data via the inverse integral transformation. In this paper, the test procedure for all specimens was ensured to be completed in the LVE range. The results show that the discrete spectrum and the continuous spectrum have similar shapes, but the magnitude and position of the spectrum peaks is different. The continuous spectrum can be considered as the limiting case of the discrete spectrum. The relaxation modulus and creep compliance constructed by the discrete and continuous spectrum are almost indistinguishable in the reduced time range of 10−5 s–103 s. However, there are more significant errors outside the time range, and the maximum error is up to 55%.

Evaluation of the Rutting Performance of the Field Specimen Using the Hamburg Wheel-Tracking Test and Dynamic Modulus Test

Rutting is a major distress occurring in the service life of the asphalt pavement, especially in hot weather areas. A laboratory-produced specimen is widely used for rutting performance evaluation which may not be completely represented by the field situation. The objective of this study is to evaluate the rutting performance of field specimens from the Chongqing highway by utilizing the Hamburg wheel-tracking test (HWTT) and dynamic modulus test. Different test conditions were conducted on the HWTT by investigation of the actual local weather condition. The results showed that rutting depth was different under different test conditions, and 10000 loading cycles were recommended as the maximum loading cycles. Particularly, several factors that influence the rutting depth were investigated, and the specimen height of 6 cm is more appropriate for the HWTT. Additionally, different test conditions were proposed as the HWTT test condition for different asphalt concrete (AC) layers in the Chongqing area. Rutting contribution of each AC layer to the pavement structure was analyzed. Moreover, the dynamic modulus at 54.4°C, 5 Hz and 54.4°C, 1 Hz could effectively represent the rutting performance of the asphalt mixture, and the dynamic modulus test is recommended for the rutting performance evaluation of the full-thickness AC layer.

Impact of Temperature Changes and Freeze—Thaw Cycles on the Behaviour of Asphalt Concrete Submerged in Water with Sodium Chloride

One of the main applications of salt in civil engineering is its use as a de-icing agent on roads in cold areas. The purpose of this research is to find out the mechanical behaviour of an asphalt concrete when it is subjected to temperature changes and freeze–thaw cycles. These temperature interactions have been carried out for dry specimens, specimens submerged in distilled water and specimens submerged in salt water (5% of sodium chloride, NaCl). An AC16 Surf D bituminous mixture was evaluated under three types of temperature interaction: three reference series remained at a controlled temperature of 20 °C, another three series were subjected to five freeze–thaw cycles and the last three series have been subjected to one year outside in Santander (Spain). The mechanical behaviour of the mixture was determined by Indirect Tensile Strength Test (ITS), Water Sensitivity Test (ITSR) and Wheel Tracking Test, Dynamic Modulus Test and Fatigue Tests. The results of the tests show that, although the temperature changes have a negative effect on the mechanical properties, salt water protects the aggregate-binder adhesive, maintains the mechanical strength, increases the number of load cycles for any strain range and reduces the time that the mixture is in contact with frozen water.

Performance evaluation and viscoelastic model establishment of recycled hot mix asphalt

In this paper, the pavement performance of recycled hot mix asphalt with 30% recycled asphalt pavement (RAP) content is studied by mix design, splitting test, freeze-thaw splitting test and dynamic modulus test. The results show that the recycled hot mix asphalt with 30% RAP content has better high-temperature deformation resistance than hot mix asphalt, but low temperature performance is slightly worse, and the water stability is not much different. It is proved that the road performance of recycled hot mix asphalt with 30% RAP content is the same as that of hot mix asphalt. Recycled hot mix asphalt with 30% RAP content can be widely used. The flexural creep test data at different temperatures were fitted to the exponential decay function, which proved that the recycled hot mix asphalt conformed to the generalized Maxwell model, and provided parameters for the establishment and analysis of the viscoelastic mechanical model of the recycled hot mix asphalt.

Characterization of the Adhesive and Cohesive Moisture Damage for Asphalt Concrete

Durability of asphalt concrete is significantly influenced by moisture damage, resulting in early degradation of asphalt pavements. There are several tests and conditioning methods adopted by agencies and researchers to identify the susceptibility of asphalt mixtures to the moisture damage. However, there is a need to develop predictive models that account for the impacts of moisture on fundamental mechanistic properties of asphalt concrete. In this regard, the focus of this paper is to develop an adhesive and a cohesive moisture damage model that enable the prediction of the amount of induced damages due to the moisture diffusion in the asphalt concrete. The models are developed based on intermolecular bond energy/force, and the mechanisms of cohesive and adhesive failures. They assume water vapor diffusion as the dominant moisture transport mode in asphalt pavements. The models are calibrated and validated by conducting dynamic modulus test on Fine Asphalt Matrix mixtures as well as Bitumen Bond Strength test on the adhesive bond between aggregate and asphalt binder. The results of validation process show the competence of the proposed models in predicting the adhesive and cohesive moisture damage of asphalt mixtures.

Effect of MSCR Percent Recovery on Performance of Polymer Modified Asphalt Mixtures

The AASHTO M332 specification includes a relationship between the non-recoverable creep compliance at 3.2 kPa ( Jnr3.2) and the percent of elastic recovery ( R3.2) from the multiple stress creep and recovery (MSCR) test. Justification for the exact position of this curve based on binder performance is largely undocumented in the technical literature as is the singular effect of higher or lower R3.2 values on mixture performance. In this study, nine binders were tested to evaluate the effect of R3.2 on the performance of asphalt mixtures. Binders with similar Jnr3.2 and varying MSCR R3.2 were divided into four groups based on their Jnr3.2 value. Comparisons were made based on results obtained from the dynamic modulus test, Hamburg wheel tracking test, and axial fatigue test. Based on these tests, it was shown that R3.2 had a strong relationship to the dynamic modulus of asphalt mixtures especially at intermediate and high temperatures. Binders with lower R3.2 had a higher dynamic modulus but showed no correlation to phase angle. Both modulus and phase angle of the mixture correlated to the binder shear modulus and phase angle. Binders with high R3.2 had a greater fatigue resistance and the effect is quite noticeable. However, R3.2 was shown to have little to no effect on the rutting resistance of the asphalt mixtures for the temperatures tested in this study. Finally, an alternative Jnr3.2 versus R3.2 relationship based on the results of this study is also presented.