| dc.description.abstract | The design of asphalt pavement has an impact on a country’s economic and environmental development. The main factors limiting the service life of flexible pavements are severe weather and increasing traffic volumes. Rutting and cracking of flexible pavement are two common types of distress that affect the serviceability and quality of the world’s transportation network. This subject has been studied extensively for decades, and it has evolved into a serious challenge that has yet to be fully resolved. Multiple research efforts have been undertaken around the world to increase pavement service life to fulfil future demand for economic expansion and community development. Multiple options for developing sustainable and cost-effective asphalt mixes with extended service life are being investigated. Although improving the characteristics of the asphalt binder has been shown
to be a promising strategy.
Geopolymer research is gaining a lot of attention these years because it can be employed in a variety of applications, such as geopolymer concrete and mortar, soil stabilization, and pavement construction. The geopolymer is formed when the aluminosilicate source, such as fly ash, reacts with the alkaline solution. Geopolymers are environmentally friendly materials that emit minimal CO2 during manufacture and can be used to eliminate waste and by-product materials like fly ash. It has also demonstrated its potential to rapidly acquire mechanical properties, improve fire resistance, and reduce energy use and greenhouse emissions. Despite, the use of geopolymer materials as a modifier for asphalt binder and mixture has gotten minimal attention, which could be due to the lack of research linking the effect of temperature and curing time on geopolymer performance and asphalt binder rheological behavior. Thus, considering these effects could motivate scientists to employ various types of geopolymers using by-products and waste materials, which would have significant financial and environmental benefits.
This research aimed to evaluate the effects of geopolymers on the rheological and performance of asphalt binder, considering the impact of temperatures, frequencies, and stresses. The rheological and performance properties of neat and modified asphalt binder were investigated using Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Environmental Scanning Electron Microscopy (ESEM) imaging devices. Also, the Viscoelastic Continuum Damage (VECD) model with the Linear Amplitude Sweep (LAS) was utilized to evaluate the fatigue behavior of the asphalt binder. Moreover, the Multiple Stress Creep Recovery (MSCR) test was conducted at various temperatures and stresses to calculate the non-recoverable creep compliance (Jnr) and the percent strain recovery (R). Furthermore, the Hamburg Wheel Rut Test (HWRT), dynamic/complex modulus, and moisture damage evaluation tests were conducted to evaluate the effect of additives on the performance of asphalt mixes.
On the other hand, the interactive effects of geopolymer content and temperature on non-recoverable creep compliance (Jnr) and creep recovery percentage (R) of geopolymer-modified asphalt binders were investigated and predictive mathematical models were developed using the Response Surface Method (RSM) and regression method. Also, the Artificial Neural Networks (ANNs) model was developed to predict the recovery and non-recovery performance of asphalt binders using five input parameters (temperature, frequency, storage modulus, loss modulus, and viscosity) and one hidden layer with five neurons. To implement a backpropagation learning process in a feed-forward neural network, Scaled Conjugate Gradient (SCG), Levenberg-Marquardt (LM), and Bayesian Regularization (BR) training algorithms were performed.
The results showed that fly ash and glass powder could be used as an aluminosilicate source during the preparation of geopolymer as an asphalt modifier, which has an essential influence on the rheological and performance of asphalt binder. While increasing the percentage of the geopolymer does not seem to affect the microstructure of the asphalt binder. The geopolymer has a significant impact on the binder’s sensitivity to temperature, whereby the temperature sensitivity for both unaged and RTFO-modified asphalt binders decreases. While adding the geopolymer to SBS enhances the binder’s ability to withstand extremely heavy traffic under high stress and temperature, the permanent deformation of the asphalt mix decreases by 82% compared with using the neat asphalt binder. Therefore, the combination of geopolymer and SBS could be used to improve the rutting resistance capability of asphalt concrete in hot climate countries. Furthermore, it was noted that the
ANNs model is appropriate to predict the percent recovery and non-recovery compliance of modified asphalt binder using unaged or aged binders at different temperatures. | en |
