Integrating wheat straw and silica fume as a balanced mechanical ameliorator for expansive soil: a novel agri-industrial waste solution.

Resource utilization of agricultural and industrial wastes with minimal screening is highly desirable in the context of sustainable development and environmental protection. In this regard, the current study proposes a novel solution of integrating milled wheat straw (WS) with minimal screening and silica fume (SF) in the form of composite binary admixture (CBA) for the stabilization of highly expansive soils. The optimum amount of WS and SF to produce CBA was determined based on a series of Atterberg's limit tests. The mechanical performance of CBA-treated soil was assessed based on the unconfined compression, direct shear, and flexural tests which showed that unconfined compressive strength (qu), cohesion (c), and flexural strength (f) were increased by 94.3%, 65.7%, and 90.7%, respectively, with an addition of 16% of CBA and 28 days of curing. Furthermore, the CBA-treated soil underwent only a 26% reduction in deformability index (ID) with an addition of 24% CBA. Furthermore, volumetric change response was assessed based on ID consolidation and swelling tests which showed that compression index (Cc), recompression index (Cr), swell potential, free swell index (FSI), and swell pressure were reduced by 72.5%, 47.7%, 59%, 35.8%, and 65%, respectively, with an addition of 16% CBA in the soil and 28 days of curing. In addition, wetting-drying (W-D) cycle tests demonstrated that CBA-treated soil was less vulnerable to W-D seasons as compared to untreated soil. Mineralogical and microstructural tests revealed that the balanced Ca:Si and Ca:Al environment created by CBA within the soil matrix produces cementing compounds, i.e., CSH and CAH, imparts strong bonds, and causes aggregation improving the mechanical response of expansive soil.

Remediation methods of heavy metal contaminated soils from environmental and geotechnical standpoints.

Heavy metal contaminated soil (HMCS) threatens world health and sustainable growth, owing to which numerous remediation methods have been devised. Meanwhile, environmental sustainability and geotechnical serviceability of remediated HMCS are important considerations for reusing such soils and achieving sustainable development goals; therefore, these considerations are critically reviewed in this article. For this purpose, different onsite and offsite remediation methods are evaluated from environmental and geotechnical standpoints. It was found that each remediation method has its own merits and limitations in terms of environmental sustainability and geotechnical serviceability; generally, sustainable green remediation (SGR) and cementation are regarded as effective solutions for the problems related to the former and latter, respectively. Overall, the impact of remediation techniques on the environment and geotechnical serviceability is a developing area of study that calls for increased efforts to improve the serviceability, sustainability, reusability and environmental friendliness of the remediated HMCS.

Toward a better understanding of the impact of mass transit air pollutants on human health.

Globally, modern mass transport systems whether by road, rail, water, or air generate airborne pollutants in both developing and developed nations. Air pollution is the primary human health concern originating from modern transportation, particularly in densely-populated urban areas. This review will specifically focus on the origin and the health impacts of carbonaceous traffic-related air pollutants (TRAP), including particulate matter (PM), volatile organic compounds (VOCs), and elemental carbon (EC). We conclude that the greatest current challenge regarding urban TRAP is understanding and evaluating the human health impacts well enough to set appropriate pollution control measures. Furthermore, we provide a detailed discussion regarding the effects of TRAP on local environments and pedestrian health in low and high traffic-density environments.