Solutions for safer, more durable infrastructure are required in light of increasing traffic and severe weather in Iraq. The most significant road conservation and maintenance challenges are the pavement's low resistance to dynamic loads and short service life. As a result, vast sums of money are spent annually to enhance the road service capacities in Iraq. Thermoplastic electrometric polymers for bitumen modification create long-lasting, cost-effective roadways. This study aims to determine how the mechanical properties of neat asphalt binder change when styrene butadiene styrene (SBS) is added as a modifier. The current research investigates adding three percentages of SBS (3, 5, and 7% of the weight of bitumen). Both neat and polymer-modified bitumen (PMB) were subjected to a series of physical laboratory and Superpave tests, including a dynamic shear rheometer tester (DSR) and a storage stability test. In addition, a chemical analysis test was conducted to identify any change in the neat binder chemical composition due to the addition of SBS polymer. The results indicated that 5% of SBS polymer was the optimum addition percentage to the local asphalt in Iraq. Additionally, it reduced the susceptibility of bitumen to temperature changes and enhanced its characteristics in all laboratory tests. The obtained PMB significantly improved rutting and fatigue factors compared to the neat asphalt binder. Based on the DSR tester and the storage stability test, the ratio of 5% SBS met the requirements of class PG76-10, used in the central and southern governorates of Iraq. Using SBS polymer on the surface course in Iraq reduces road damage due to the scorching summer sun, reduces the likelihood of rutting and fatigue cracking, and works well in hot regions, resulting in roads that last longer, provide comfortable riding, and require less maintenance.

Semi-flexible pavement (SFP), also known as grouted pavement, is a type of pavement structure consisting of a porous asphalt skeleton with air voids between 25 and 35% injected with cementitious grout materials. The special skeleton of SFP provided enhanced durability and resilience, making it a promising option for the construction of road surfaces in high-traffic areas and severe conditions. The main aim of the current research is to investigate the rutting behavior and moisture resilience of SFP-containing sustainable grout using ceramic waste powder (CWP). This research introduced the use of CWP as a replacement for conventional grout (cement) in SFP for the first time. CWP partially replaced cement at ratios of 15, 20, 30, 40, and 50% of the cement weight. Indirect Tensile Strength (ITS) and Hamburg Wheel Tracking Tests (HWTT) were used to evaluate the performance of SFP to reduce the detrimental effect of moisture. The grout modified with CWP shows excellent results in the ITS and Tensile Strength Ratio (TSR), and all modified SFP mixtures give higher values in these tests compared with Control Mix (CM). In the HWTT, the minimum rut depth of the modified SFP was 2.8 mm and 3.10 mm. Compared to CM, rutting decreased by 73%–76% for CWP mixes with 20% and 30% replacement. This indicates the high fluidity of CWP, which enabled it to penetrate all voids in the porous pavement (PA) and form a dense microstructure due to its excellent pozzolanic interaction, making it a strong structure capable of bearing rutting.

The use of waste, recycled, and modified materials is increasingly popular in roadway construction for sustainability and pavement longevity. This research examines the combination of steel slag (SS) and low-density polyethylene (LDPE), commonly used in plastic bags and steel manufacturing by-products, to mitigate environmental pollution. LDPE was tested as a binder modifier in two bitumen grades, 60–70 and 80–100, at concentrations of 3%, 5%, and 7% by weight. SS was used as a replacement for coarse aggregate. The physical properties of both modified and unmodified bitumen grades and SS were analyzed before creating and testing hot-mix asphalt (HMA) samples. The dynamic modulus of these samples was measured at temperatures of 4.4 °C, 21.1 °C, 37.8 °C, and 54.4 °C with frequencies of 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz. Master curves were developed, and the dynamic modulus data underwent design of experiment (DOE) and computational intelligence (CI) analyses. Using KENPAVE, a mechanistic–empirical tool, the analysis assessed the design life and enhancements in damage ratio for each modifier and grade. The results showed that adding LDPE increases the softening point and penetration grade but decreases ductility due to increased bitumen stiffness, leading to premature fatigue failure at higher LDPE levels. Both 3% LDPE and 3% SS-modified LDPE improved Marshall Stability and dynamic modulus across all temperature and frequency ranges. Specifically, 3% LDPE enhanced stability by 13–16% and 3% SS-LDPE by 30–32%. The KENPAVE results for 3% LDPE showed a design life improvement of 19–25% and a damage ratio reduction of 15–18%. In comparison, 3% SS-LDPE demonstrated a design life improvement of 50–60% and a damage ratio reduction of 25–35%. Overall, this study concludes that 3% LDPE- and 3% SS-LDPE-modified HMA in both bitumen grades 60–70 and 80–100 provide optimal results for improving pavement performance.

In last years, a new type of pavement has gained popularity, this type is called Semi-Flexible Pavement (SFP). It consists of porous asphalt with high air voids between (25-35) % filled with cementitious grout materials. This type of pavement substance offers substantial advantages over both common types of pavements (concrete and flexible) such as good resistance to rutting and durability. SFP is considered an alternative pavement to exceed the drawbacks that occur for both flexible and concrete pavements. SFP has good features against permanent deformation, oil spillage, and fatigue resistance. Previous studies have shown that it can be used in a variety of applications such as highways, motorways, bridge deck pavement, tunnels, industrial areas with industrial equipment traffic, airport aprons, and stations. The goal of this research is to identify and compile the most significant research papers using the Web of Science (WOS), analyze the data using the VOS viewer software, as well as learn which countries and institutions had published the most articles relating to the subject of cementitious grout material as it relates to semi-flexible. It was also done to learn more about the authors and their collaboration. In addition to knowing the keywords that will aid researchers in their research on this topic, using these studies to better understand the elements that affect how well semi-flexible mixtures and grouts perform such as porous asphalt Mixture gradation and grout material components.

The exploitation of locally available and abundant natural resources such as silica sand and its use as a supplementary cementitious material in the production of grout used in semi-flexible pavement (SFP) surfaces is of paramount importance in reducing transportation costs and emissions, contributing to more sustainable development practices, and reducing the overall environmental impact of cement plants. SFP or injected pavement, is a porous asphalt structure with 25–35% voids, filled with cementitious grout. SFP is distinguished by its robustness, resistance to deformation, and exceptional longevity, enabling it to endure substantial traffic loads and extreme weather conditions, hence offering a strong and dependable road surface that is comparatively simpler to maintain than other road construction types. This study focuses on developing a novel sustainable cementitious grout for SFP by partially substituting traditional cement with quartz silica sand powder (QSP) in different proportions (10%, 20%, and 30%). The grout mixtures were evaluated for flow and mechanical properties. Also, SFP samples were made by adding a 5% SBS modifier to a hot mix porous asphalt (HMPA) and then filling the holes with a predesigned cement-based grout then these samples were assessed for Marshall stability and moisture damage resistance tests. The results demonstrated that replacing cement with more than 10% of QSP reduces compressive strength and stability. This is due to the reduction in workability caused by water absorption in the grout mixture. This, in turn, increases the water-to-cement ratio to achieve the required fluidity, as well as increasing the porosity and decreasing the volume of hydration products. Therefore, this study suggests that 10% of QSP is the optimum replacement ratio as it achieves the required fluidity and increases the compressive strength, stability, and tensile strength ratio by 20.7%, 13.4%, and 12.0% respectively at 28 days of curing compared to the reference grout mixture. This mixture is considered suitable as it combines the properties of durability and environmental objectives by reducing the grinding energy and its use in severe conditions.