This paper presents the study carried out to assess and compare the performance of marginal soils, namely marl, sabkha and dune sand stabilised with emulsified sulphur asphalt (ESA) with the mixtures of the same soils stabilised with conventional emulsified asphalt (EA) to be used as a base layer for road layers. The mixtures of ESA and EA for the three marginal soils were designed utilising 2% Portland cement and were optimised to meet dry and wet Marshall stability requirements. Designed mixtures were assessed for dry indirect tensile strength (ITS), static triaxial (shear strength) and dynamic resilient modulus at 22°C. Results indicate that ESA decreased the stability and shear strength of the treated soils compared to the conventional EA. On the other hand, there was an improvement in ITS, especially for marl and sabkha soils, and an increase in the resilient modulus of soils–ESA mixtures compared with standard soils–EA mixtures. ESA can be used successfully to construct base layers for roads from available marginal soils since it fulfilled the specification requirements.

The deficiency of high-quality soils in Saudi Arabia’s southern and northern regions, as well as along the Arabian Gulf coasts, is regarded as one of the most common issues with the construction of roads. High compressibility, low shear strength, substantial volume change (particularly in Sabkha), and low bearing capacity are the most typical issues with these problematic soils. In this study, finite element simulations were performed using the Plaxis 3D software v20 to simulate the performance and study the critical responses (fatigue, rutting strains, and damage ratio) of an enhanced pavement structure with a geogrid reinforcement resting on the naturally problematic Sabkha subgrade. A normal asphalt concrete layer, a base layer of Sabkha soil stabilized with Foamed Sulfur Asphalt (FSA), and a sand dune subbase layer comprised the pavement structure. For each layer, the model’s input parameters were a mix of laboratory and literature data. The simulation was performed on a pavement structure without reinforcement and on another section enhanced with a geogrid positioned at various locations to determine the ideal placement for lowering the important responses such as fatigue, rutting stresses, and damage ratio. The nonlinear behavior of an FSA–Sabkha base, sand subbase layer, and Sabkha subgrade was simulated using the hardening soil model, whereas the asphaltic concrete layer and geogrid material were simulated using the linear elastic model. The findings of the simulations demonstrated that placing geogrid reinforcement at the top of the subgrade layer resulted in the greatest reduction in horizontal tensile (fatigue) and vertical compressive (rutting) strains, as well as vertical displacement (32.71%, 13.2%, and 14.2%, respectively). In addition, geogrid reinforcement greatly reduced the fatigue damage ratio (33% to 55%), although the reduction in the rutting damage ratio was slightly lower (14% to 30%). The simulation results were validated using a wheel tracking machine and it was clear that there is a reasonable agreement between the results.

People are forced to use all types of soil, especially bad soils, as infrastructure demands grow. Different procedures must be used to ameliorate these poor soils, which are fragile during building. Natural resource depletion and the rising costs of available materials force us to consider alternative supplies. For several years, researchers have investigated the use of by-products from industry and associated approaches to improve the qualities of various soils. Coarse Aggregate Crushing Waste (CACW) is a waste product that results from the primary crushing of aggregates. Massive amounts of CACW are produced in the business, posing serious issues from handling to disposal. As a result, the widespread use of CACW for diverse purposes has been recommended in the civil engineering profession to address these concerns. Because some natural resources, such as gravel, are nonrenewable, it is vital to decrease their consumption and replace them with recycled, cost-effective, and ecologically acceptable alternatives. This research aimed to investigate the possibility of reusing CACW to improve the geotechnical properties of silty sand (SM) soil available in the Najran region. In this research, soil samples were collected from Najran city and subjected to a variety of lab experiments to determine their characterization. Mixes were designed for a parent soil with a range of percentages of CACW with/without 2% cement. The designed mixes were examined through a set of lab tests to obtain the optimum design for use in road construction. The findings of the tests showed that the optimum dosage is 10% CACW with 2% cement, raising the undrained shear strength of silty sand soil by 323%, CBR by 286%, and P-wave by 180%. The durability tests show that soil mixed with 10% CACW and 2% cement fulfills the requirements and stays within the 14% weight loss limit imposed by the Portland Cement Association (PCA). The microscopic investigation results confirmed the outcomes obtained by macro tests. As a result, the carbon footprint values decrease when CAWA is added, making this treatment approach almost carbon neutral. This study clarifies the long-term effects of CACW on improving the geotechnical characteristics of silty sand soil in the Najran Region of the Kingdom of Saudi Arabia and other comparable soils globally.

Earth is the most common and important building material used in the construction industry, since it is found in almost every country in the world. Modern earthen construction is alive and well, and is spread over an enormous geographical area. This technique utilizes various earthen materials and numerous methods, and features many benefits for both construction in general and buildings in particular. Najran, a city located in the south of Saudi Arabia, is distinguished by its heritage of earthen architecture, which displays many advantages and a marvelous variety of types and exterior designs. Many weaknesses of the material, however, along with a lack of knowledge and rapid development have caused the uplifting and destruction of many of Najran’s mud and heritage buildings during the last few generations. Not all soil types are suitable for every building need. Soil specification is thus very important in order to ensure that the materials used in construction meet all requirements. The main goal of this study was to invistegate the suitability of local soils for the earthen building construction. Thus, available local materials of common quality were taken from local sites in Najran. Laboratory experimentation and testing was then performed to determine the properties of those materials. The results showed that local soil properties are suitable for using in the earthen block construction since they satisified the specifications. The results were then recorded for use in further studies, as well as to explore heritage building and rehabilitation, and to improve modern earthen building materials and techniques.