Maryam Naeimi

Alkali-activation materials (AAM) have been used to produce inorganic cements for over a century, as a means of valorizing wastes or industrial by-products derived from different commercial activities. Due to their potential benefits, research focused on its application as soil stabilizers. Among AAM, olivine was mentioned as the most influential one. Therefore, the current study reviews the potential application of olivine in geotechnical engineering by considering its application for sand movements mitigation due to wind erosion. However, in order to obtain the environmental aims, it is essential to use activators that were produced cleanly and sustainably in which two various activators have been used. The results of the present study indicated the unconfined compressive strength (UCS) increment of soil samples treated using NaOH compared to KOH by the rate of 47 to 60% after 28 days. Moreover, raising the percentage of olivine by the rate of 2, resulted in the UCS of samples to be increased by more than 70%, while all the treated samples showed 100% protection to wind erosion. Hence, due to the regulations of the Department of the Environment by minimum strength of the stabilizers to be more than 200 kPa, the application of olivine was recommended to combat wind erosion.

Considering the presence of 274 dusty days in 2021 in Zabol city, Iran, the present study aimed to evaluate the feasibility of using treated sewage effluent (TSE) for dust mitigation with natural methods of increasing land cover. Hence, first of all, the identification of sewage treatment facilities along with the volume and chemical status was carried out and compared to the various national and international legislation. Then, field investigation on land use and land cover, along with literature review on dust origins, sand detachment areas, and sand corridors in the study area will be assisted for optimal area suggestion. Note that, in the present study it was assumed that the application of TSE for wetting the surface to vegetation restoration resulted in wind erosion control in critical foci. The results showed that, so far, a total of 39,000 m³/day could be treated, in the whole study area. The TSE volume calculated based on two scenarios consisting, (1) data obtained from the related organization, and (2) based the capacity of the wastewater plant is 2.8 and 5.1 mcm/year, respectively. Additionally, the study of TSE quality and its comparison to various regulation such as FAO, USEPA, INS, and CWQI indicated the applicability of transforming TSE to 14 km away from the WWT planet daily for rehabilitation of Hammon Hirmand through irrigation ofT.strictato increase the vegetation cover to above 30%.

Biogeotechnology, is one of the most notable methods of soil improvement techniques. Along with the use of calcium-based biocement, the probability of using an inventive approach through the iron salts precipitation was also investigated. The present study discussed the feasibility of iron-based biocement using the combination of chemically and microbially source of ferrous cations. The method was introduced as an economical and green method using a cheap and accessible source of iron ore. A biocement treatment test via iron-based process was used to investigate the suitability of using three methods to improve geotechnical properties of loose sand and determine their respective hydraulic conductivity. The results of this study demonstrated that 1% of cation salts in sand was sufficient to reduce the hydraulic conductivity to 10-7 m/s as the bioclogging was performed mainly in the channels between sand particles. Moreover, the precipitation of iron salts was also seen between sand grains in the SEM images.

Climate change is considered the major environmental challenge for the world. Cement and lime production is a highly energy-consuming, heavily polluting process, and the CO₂ emissions are very substantial. Alkaline environment, high temperature, and long processing time lead the researchers to work on alternative soil improvements. Microbially induced calcite precipitation (MICP) has been introduced as a technique for modification of geotechnical properties of sand. The main purpose of the present study was to focus on the efficiency and environmental impact of conventional and microbial grouting. Samples were treated with three chemical stabilizers, namely Portland cement, lime, and cement and lime. The stabilizers were injected with flow gravity and constant head which are almost the same as microbial grouting. Then, the results of conventional grouting were compared with the results of biocement samples which were gathered from previous studies to discuss the efficiency and environmental impacts. The results for treated samples were discussed and compared based on 1 m³ of soil and a final target of 700 kPa. It was found that in order to obtain the same compressive strength, the cost and calcium carbonate consumption of the cement injection method were 2.5 times more than those of the microbial method. Biocementation has some advantages over existing technologies, such as less calcium usage in the same unconfined compressive strength (UCS).