In this paper, the combined effect of adding polyphosphoric acid (PPA) and distillate aromatic extracts (DAE) oil on rheological and mechanical characteristics of neat asphalt binder at high and low temperature is investigated. PPA was added to neat asphalt binder with three different contents of 0.5, 1, and 2% by weight of asphalt, and DAE was added to neat and PPA-modified asphalt binders to the extent of 10%. In total, one neat and seven modified asphalt samples were investigated in this research by implementing dynamic shear rheometer and bending beam rheometer for evaluating high and low temperature respectively. Using superpave protocol criteria, high and low service temperature of all specimens are determined. In addition, an extension of the simple fractional viscoelastic model is developed as a generalized fractional viscoelastic model to determine and describe low temperature parameters of all samples including damping ratio and dissipated energy ratio. Results show that using 1% of PPA in conjunction with 10% of DAE can balance high and low temperature appropriately to obtain a modified asphalt binder of PG70-28 from a neat asphalt binder of PG64-22. Also, implementing the generalized fractional viscoelastic model successfully resolved shortcomings of simple fractional element, especially for capturing variation of damping ratio and phase angle versus frequency.

The dynamic shear rheometer was used to investigate the effect of polyphosphoric acid (PPA) and styrene-butadiene-styrene (SBS) modification on the rheological and mechanical behavior of asphalt binder and asphalt mastic. In this research, three SBS contents (2%, 4%, and 6%) and three PPA contents (0.5%, 1%, and 2% by weight of neat asphalt binder) were used. Also, two volume fractions (18% and 35%) of silica filler were selected to fabricate asphalt mastic samples. In total, 1 neat asphalt binder, 6 modified asphalt samples, and 12 modified asphalt mastics were investigated. By using storage and loss moduli data of all samples in a frequency range between 0.1 and 100 Hz at various temperatures between −25°C and 22°C, the Cole-Cole and black space diagrams were plotted and analyzed. The results clearly show that the linear viscoelastic behavior of asphalt mastic is directly related to asphalt binder because of the identical forms of the Cole-Cole curve. An optical microscope was also used to see filler particle distribution in the bitumen structure. The stiffening phenomenon for a volume fraction of 35% was observed in comparison with a volume fraction of 18%, consistent with other previous research work. Adding PPA causes extra stiffening related to formation of the strong structure of PPA between filler particles.

After a comprehensive experimental program on asphalt mastic modified with styrene-butadiene-styrene (SBS) and polyphosphoric acid (PPA) with two filling ratios of 18% and 35%, in this paper, a biphasic finite-element method was implemented to simulate asphalt mastic as a heterogeneous medium consisting of aggregate particles as inclusions within the asphalt binder as the matrix. For this purpose, linear viscoelastic properties of neat and modified asphalt binders including complex shear modulus ($G^{*}$ ) and phase angle ($\delta$ ) were obtained from the results of dynamic shear rheometer tests in frequency sweep mode, and the generalized Maxwell model was used to prepare material properties for inputting in ABAQUS, which was used to solve the problem numerically. In this research, the structure of aggregate particles was randomly generated, thanks to the custom software MOA (French acronym for random object modeler), based on the aggregate’s grading curve. Comparing the results of numerical modeling with experimental test results showed that, for a filling ratio of 18% by volume, random generation of inclusions can successfully simulate linear viscoelastic behavior of original and modified asphalt mastic. However, with respect to the higher difference between numerical results and experimental observation of asphalt mastic samples with a filling ratio of 35%, a phenomenon known as stiffening effect was captured by using optical microscope pictures and simulated in a numerical model, which positively eliminated the error of numerical modeling.

The utilization of Ordinary Portland Cement as the primary material of choice in the construction industry has had its drawbacks due to the large amounts of pollution Portland cement’s production causes. Significant findings have been discovered, and alkali-activated materials have been implemented as an alternative cementitious material to the traditional concrete of today. Alkali-activated materials can be formulated using industrial wastes, making them eco-friendly and a more sustainable replacement for concrete. This study aims to assess whether alkali-activated materials can be implemented in infrastructural fields and seeks to evaluate the possibility of alkali-activated materials acting as pavement-quality concrete in infrastructural applications. This review presents the results of various studies, demonstrating that alkali-activated materials can meet the requirements for pavement-quality concrete with the proper incorporation of industrial wastes. This outlines the viability of alkali-activated materials (AAMs) as a green alternative for pavement applications as most AAMs attain required mechanical properties, mostly reaching compressive strength values higher than the required 40 MPa, all while simultaneously adhering to the needed durability, workability, drying shrinkage, and abrasion resistance attributes. Using industrial waste-based alkali-activated materials renders the material eco-friendly and sustainable, all while enhancing the material’s characteristics and properties necessary for large-scale infrastructural applications. This review highlights AAMs’ suitability as a durable and eco-friendly solution for pavement construction.