The influence of steel slag expansion level on the early stage performance of hot mix asphalt (HMA) is evaluated. Initially, samples of Linz-Donawitz type steel slag with different levels of expansion (6.71%, 3.16%, 1.33%) were submitted to physical, mechanical, and morphological characterization to assess the effects of expansion on individual material properties. Steel slag was then used as aggregate in HMA to verify the effects of its expansion characteristics on the volumetric and mechanical performance of the asphalt mixture. Four different asphalt mixtures were designed based on Marshall mix design, using asphalt cement (pen. grade 50/70), natural aggregate (granite), and steel slag (in three different levels of expansion). The mechanical characteristics of the asphalt mixture were evaluated based on results from Marshall stability, indirect tensile strength, and resilient modulus testing. A modified Pennsylvania testing method (PTM) was also performed on the studied asphalt mixtures to verify the potential of asphalt binder film to minimize the expansive reactions of steel slag. It was observed that the level of steel slag expansion changes some of the material’s individual properties, which can affect the volumetric parameters of the mix design. The use of steel slag as aggregate in HMA also improves the mechanical properties of non-aged asphalt mixtures. Moreover, the expansive characteristics of this material could be minimized when combined with other asphalt mixture components.

The use of soil stabilization in place of cutting out and replacing the existing subgrade soil can save significant amounts of resources in roadway construction projects. Also, the possibility of stabilizing a low-grade soil using by-products is economically and environmentally attractive. Considering that, the main objective of this study is to show the technical feasibility of using desulfurization steel slag from the Kambara reactor process (KR slag) as a soil stabilizer. A total of nine soil mixes were evaluated in the laboratory, varying the type of soil and the percentage and type of additives (KR slag and portland cement) used. After laboratory evaluation, two field sections were constructed. The trial sections were subject to repetitive traffic loading using a heavy-vehicle simulator (HVS). Weekly measurements were taken according to the following tests: Benkelman beam, British portable tester, and rutting depth measurements. The soil-KR mix designed with 20% KR slag addition and a poor-grade soil (clay) performed as well as the typical soil modified by cement solution designed with a better-quality soil (sand) modified by 3% cement. The clay soil did not meet standard requirements even when mixed with 10% portland cement. However, the clay soil modified by KR slag not only presented satisfactory laboratory results for roadway use in the base and/or subbase utilization, it also showed excellent field performance.

Although waste plastic (WP) application as a paving material has drawn increasing attention from scholars, there is a lack of studies that summarize the latest development of WP research. Considering there is no standard procedure to incorporate WPs in asphalt mixtures, it is important to document the major findings from the available literature to identify knowledge gaps to tackle in future research and advance knowledge on this subject. Using a bibliometric analysis method, this study carries out a holistic review of WP articles published from 2003 to 2023, focusing on incorporating WP in asphalt mixtures via the dry method. This study particularly focused on identifying and evaluating individual types of WP mostly used in asphalt mixtures via the dry method and how their most common characteristics (size, shape, and melting point) affect the mixing procedure and the overall mixture’s performance. The analysis highlighted China, the USA, and India as leading countries in WP-related publications. Typically, low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polyethylene terephthalate (PET) were the most utilized WPs in the dry method. Smaller WP particle sizes (<2.36 mm) were considered more suitable in asphalt mixtures. In general, studies employing procedures involving WP melting, typically by introducing WP to pre-heated aggregates at temperatures surpassing its melting point, resulted in improved asphalt mixtures with enhanced resistance to rutting, cracking, and moisture damage. In this context, positive performance outcomes were notably observed in studies using HDPE or LDPE, potentially because of their low melting point. The key knowledge gaps identified were the lack of a consistent procedure applicable across studies, a feasibility assessment for scaling laboratory-based procedures to field applications, and laboratory evaluations utilizing advanced performance tests as suggested in the Balance Mix Design (BMD) approaches.