فهرست مطالب amirreza goodarzi

The cement-based stabilization/solidification (S/S) method is widely used in modifying soils polluted by heavy metals (HMs), although it may face technical, economic, and environmental limitations. Therefore, the present work was designed to investigate the effectiveness of a type of geopolymer based on the steel slag (SGP) and its combination with microparticles of zeolite (SGPZ), compared to cement (as a traditional additive), in enhancing the stability of S/S products. In so doing, different percentages (0 to 250 mg/g-soil) of SGP, SGPZ, and sole cement were separately added to the S/S samples containing different concentrations of lead (including 5000, 10000, 20000 and 40000 mg/kg-soil). After adequate curing (up to 28 days), a set of macro and micro scale experiments were performed to assess the long-term performance of the amended soil samples using a laboratory accelerated aging procedure that simulated 25, 50, 75 and 100 years of exposure to the acid rain and wet and dry (W-D) cycles in the field. It was found that, while low amounts of cement (PC) would greatly reduce the initial bioavailability of pollution in the pore fluid of soil, increasing the contact time of the PC-treated specimens upon harsh conditions, especially in the presence of high level of Pb, would dramatically diminish the efficiency of the precipitation mechanism as well as the degree of encapsulation process which play a significant role in increasing the ability of S/S sample to release the toxic ions stabilized/solidified previously. At simulated 100 years, the toxicity characteristic leaching procedure leached Pb from the PC-treated sample with 250 mg/g-soil binder would exceed the permitted threshold of pollution leaching (≥ 5 mg/L) by 508%, indicating that meeting the S/S regulation limits requires a large consumption of cement. The study showed that, unlike treatment conditions with the same level of PC, the use of novel cement-free S/S binders (especially SGPZ) would significantly limit the negative influences of the environmental changes on HM remobilization risks. In addition, the mechanical characteristics of those series of samples were sometimes up to 1.4 times higher than that of the soil modified with cement alone. Based on the X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images, this enhancement can be mainly due to i) reduction in the adverse HM-binder interactions, ii) intensification in the level of hydration reactions, iii) formation of secondary complex hydrated phases (e.g., Hydrotalcite: Mg6Al2CO3(OH)16.4H2O), and iv) creation of a three-dimensional network of solidification in the system containing geopolymer, wrapping the matrix of S/S products against the structure disintegration upon contact to the aggressive environments. Therefore, under the destroying impacts of acid attack and W-D scenario, adding 25% SGPZ composite could pass the S/S regulation limits. In general, based on the obtained results, the use of geopolymer (especially containing zeolite) is suggested as an effective and environmentally friendly alternative for sustainable soil improvement, even with the high contents of HM ions. Following the USEPA and UKAE standards to achieve the safe S/S performance, the optimal dosage of GP binder was determined to be approximately 6 mg/g-soil per 1 g/kg of lead in the sample.

Atmospheric aerosols are a colloid of solid particles or liquid droplets suspended in the atmosphere. Their diameter is between 10-2 to 10-3 micrometers. They directly and indirectly affect the global climate by absorbing and scattering solar radiation, and they also have a serious impact on human health by emitting harmful substances. In addition, high concentrations of aerosols on a local scale due to natural or human activities have adverse effects on human health, including cancers, pulmonary inflammation, and cardiopulmonary mortality. Monitoring the temporal and spatial variability of high concentrations of aerosols requires regular measurement of their optical properties such as aerosol optical depth (AOD).

Algeria is a large country with little knowledge of the spatial and temporal diversity of AOD, and the low spatial resolution of existing products makes it very difficult to predict aerosols (airborne particles) at the local scale, especially in arid southern regions. As a result, AOD recovery with data with higher spatial resolution is crucial for determining air pollution and air quality information. Several AERONET stations have been installed in Algeria. The Tamanrasset_INM station has been selected based on its location and the availability of historical AOD data for the period (2015-2016).
In this study, Landsat-8 / OLI image from tile 192/44 was used for satellite images. To this end, 23 TOA-corrected L1G-level Landsat-8 / OLI cloudless scenes were downloaded from January 2015 to December 2016 in the study area. DN values ​​are converted to TOA reflections using the scaling factor coefficients in the OLI Landsat-8 metadata file. In this study, the minimum monthly reflectance technique was used to recover AOD in this area. As a result, LSR images were used in the recovery process in different months of 2015 and 2016. The process of selecting reference LSRs was initially based on the selection of clear, foggy / cloudless sky images. The selected images were then used to construct artificial images in which each pixel corresponds to the second lowest surface reflection of all selected monthly images to be the LSR pixel for the respective month. The AOD retrieval method developed in this study is based on a LUT, using the 6S radiative transfer model. The advantage of using the 6S model is its ability to estimate direct components and scattering using a limited number of inputs for each spectral band in the entire solar domain. The effect of the viewing angle is limited because Landsat data are usually obtained with a fixed viewing angle. Surface reflectance can be estimated from a pre-calculated LSR database. The accuracy of AOD recovery depends on the use of the appropriate aerosol model. A continental model was selected from the available aerosol models. Other atmospheric parameters such as ozone, carbon dioxide, carbon monoxide and water vapor are considered by default. The AOD values ​​used to make LUT are set as follows: 0.0, 0.05, 0.1, 1.5, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 and 1.5. The zenith angles of the sun and the sensor range from 0 to 70 degrees with a step of 5 degrees and the range of azimuth angles from 0 to 180 degrees with a step of 12 degrees. Using these parameters, the radiative transfer equation was run in forward to obtain the TOA reflection. Different combinations of input and TOA output parameters are stored in LUT. AOD retrieval is based on a comparison between the TOAs estimated with the model and the observed items using the best fit approach. Using such an approach, the estimated AODs are simulated in accordance with those used in the production of TOAs, using a competency function that minimizes the distance.

In this study, the AODs recovered at 550 nm in a 5-by-5-pixel window around the AERONET site were averaged. The considered AERONET values ​​are the average of all measurements taken within ± 30 minutes of image acquisition time. Observation regression results (AOD from Landsat 8 images and AERONET stations) showed that the correlation coefficient is about 84%. This study shows a good fit of the model on the research data and shows the high capability of the model. This study showed a strong recovery of AOD against AERONET data of more than 70% at . The differences can be attributed to a limited number of points or hypotheses related to the aerosol model used in this study. The assumption of using a pre-calculated LSR does not limit the accuracy of this method because we have shown that in arid regions where the change in land cover in different months of the year is small, a pre-calculated LSR image can be representation used the share of surface reflection in the radiative transfer model throughout the month.

In this study, an AOD derived from a high-resolution satellite at an urban scale was produced in the city of Tamanrasset, Algeria. The developed method assumes that the change in land cover is minimal and the temporal change in LSR is not significant. A pre-calculated LSR image is created to show the surface reflection in the retrieval process. Based on the 6S radiative transfer model, an LUT was constructed to simulate the TOA reflection of the built-in LSRs and a set of geometric and atmospheric parameters. The retrieved AODs were compared with the AERONET ground data. The results show that this approach can achieve reasonable accuracy in AOD recovery, which reaches about 70.9% at . In addition, this approach is suitable for estimating AOD in urban areas compared to existing AOD products with low spatial resolution. The results of this study show a 4% improvement compared to the results of Omari et al. (2019). The results of this study showed that ignoring the monthly changes in LSR values leads to good results in AOD recovery.

In the present study, the effectiveness of a new combination of industrial wastes including calcium carbide residue (CCR) and silica-fume (SF) along with polypropylene fiber was investigated in comparison with cement for improving soft clays and increasing their durability. The results showed that in normal curing conditions, the use of CCR alone has little effect on the soil geo-mechanical performance. On the other hand, despite the initial favorable performance of cement, the W-D cycle with the failure of cement nanostructures can lead to the disturbance and even complete loss of the soil-bearing capacity. In contrast, the combination of CCR with SF had a prominent role in the stabilization process and a much lower deterioration potential was observed in the presence of the optimal ratio of CCR-SF. According to SEM-EDX and XRD analysis, expansion of solidification and reduction of voids were evaluated as the main factors of the more appropriate response of the recent system. Adding fiber to this series of samples had a significant effect on the growth of tensile strength, better absorption of energy, reduction of cracking ability, and as a result, improving the stability of the soil matrix. Following such a condition, the strength of the reinforced sample containing a 15% additive was found to be about 1.8 times the threshold allowed for successful stabilization. This can be attributed to the synergism of CCR-SF and fibers in improving the particle conjunction and reducing the access of voids for soil-water interaction. Based on the obtained results, the use of an optimal combination of CCR-SF with fiber can be recommended as a low-cost, environmentally friendly, and efficient option in improving the behavior of problematic soils and reducing their post-failure potential.

Nano-structures of Cobalt Metal-Organic Complex (Co-MOC), [Co(NCS)2(L)(H2O)2.3(L)] {1} (L=2,5-dimethyl pyrazine), have been synthesized under different experimental conditions. Micrometric crystals (bulk) or nano-sized materials have been obtained depending on using the branch tube method or sonochemical irradiation. All materials have been characterized by Scanning Electron Microscopy (SEM), Powder X-Ray Diffraction (PXRD), FT-IR spectroscopy, and elemental analyses. Single crystal X-ray analyses on 1 display that Co2+ ions are 6-coordinated and 0D coordination complex and two organic ligands (L) are not coordinated to Co(II) in the crystal lattice. Moreover, the impacts of the following parameters were investigated: ultrasonic power, reaction temperature, and reactant concentrations on structural and morphological features of the obtained materials. In the following step, the size of the nanomaterials was investigated based on SEM images. Finally, the intermolecular interaction of molecular crystals of 1 was also studied by Hirshfeld surface analysis.

Electrokinetic (EK) remediation is a very effective option for the soil decontamination; however, its efficiency depends on several factors. In the present study, the ability of Ethylene-diaminete-traacetic-acid (EDTA) and pulse current to improve this method for treating fine-grained soils containing heavy metals (HMs) was investigated. In so doing, first, the studied sample (mainly kaolinite) was mixed with a concentration of 5000 mg/kg zinc (Zn) and lead (Pb) and then subjected to an electrokinetic test with voltage gradient of 2 V(DC)/cm2 (in the form of continuous current and pulse) under 7, 14 and 28 days. The pulse current used was ON for 30 minutes and OFF for 10 minutes. In this process, different concentrations of EDTA (including a concentration of 0.1 M and 0.2 M) were also added to the anode and cathode reservoirs, separately and simultaneously. The obtained results showed that in the conditions of continuous current and without EDTA addtion (the common EK method), the EK removal efficiency, especially for lead, was not noticeable. According to the changes in the microstructure of soil sample and its electrical conductivity (EC) between the anode and the cathode electrodes, the reason can be ascribed to the decrease in current density due to precipitation of pollutants in the soil matrix and decresing the HMs transportation in the cathode side, as clearly confirmed by the XRD patterns and EC tests. In this case, increasing the test time from 7 to 28 days (despite more energy consumption) mainly caused the change of the pollution position in the around of anode side and the HMs removal in the cathode side is not enhanced, indicating that there is a limited effect (about 20%) on the total efficiency of the EK tests. It was found that the addition of EDTA only in the form of catholyte solution, even with the equivalent concentration of soil pollution, has a low effect on improving the electrokinetic response. On the other hand, the presence of the chelating agent in both reservoirs of the EK device, especially by applying the pulse current (with a frequency equal to 36 cycles/day) accelerates the treating process of EK remediation. In fact, as the results of macro-structural tests, scanning electron microscope (SEM) images and X-ray diffraction (XRD) analyses indicated, such improvement can be attributed to two major changes in soil-pollutant interaction. First of all, the presented EK method, by developing the penetration of the acid front towards the cathode side and limiting the polarization ability of clay particles, causes the formation of flocculation and reduces the soil ability to keep pollutants. Also, this system greatly reduces the contribution of insoluble phases through the processes of redissolution and formation of the stable complexes as well as generates a disturbance in the initial formation of metal precipitation due to the reduction in the hydrolysis reaction of the cathode part. Synergy of these changes has an prominent role in accelerating the EK mechanisms; so that compared to the conventional EK model, while reducing energy consumption by 25%, it can also increase the removal efficiency by nearly 2.6 times.

Amoxicillin (AMX) is one of the commonly used commercial antibiotics due to its high resistance to bacteria and its large spectrum against a wide variety of microorganisms, which it´s existence in the wastewater from pharmaceutical industries and hospital effluents causes unpleasant odor, skin disorder, and microbial resistance among pathogen organisms, and it can lead to the death of microorganisms which are effective in wastewater treatment. Therefore, this study was conducted to investigate of removal efficacy of AMX from aqueous solutions using GO@Fe3O4@CeO2.

In this descriptive study, GO@Fe3O4@CeO2 was synthesized and then used as a photocatalyst for the removal of AMX from aqueous solution. GO@Fe3O4@CeO2 was characterized using X-Ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), SEM-EDX elemental analysis, Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM) methods. Additionally, the influence of variables including pH (3-11), amount of photocatalyst (0.006-0.04 g), contact time (0-150 min), and temperature (25-55 °C) was assessed on the efficacy of AMX removal. 

The results indicated that removal efficiency increased up to 90 min contact time, 0.02 g of photocatalyst, and at the temperature of 25 °C. The optimum pH for AMX removal was 10.

GO@Fe3O4@CeO2 could be an effective and available photocatalyst for the removal of AMX from industrial wastewater under UV light.

Although cement stabilization is used extensively to modify the soft clays, it may show limited success in some applications. Hence, this paper presents a multiscale investigation on the viability of employing zeolite and fiber to enhance the durability of cement treated soil against the freezing-thawing (F-T) cycles. In so doing, a wide range (0 to 30%) of additives including sole cement and cement-zeolite mixture (CZ) with different cement replacement were separately added to a soft soil sample and then mixed with the optimal fiber content of 0.75% (by weight), which was determined by the indirect tensile strength test. A set of experiments at various curing days (up to 90 days) were performed to study the mechanical and microstructural changes of the stabilized soils. The results indicated that while a low level of cement can modify the geo-mechanical parameters of soil sample, the compressive strength of cemented soil could decay up to 60% when the specimens exposure to the successive F-T cycles. Such changes may be ascribe to the F-T-induced particles rearrangement and degradation of the cementation structure-bonding, forming many new voids and cracks subsequently decreasing the interlocking of matrix. As a result, to get the strength guidelines threshold and make the composite water proofing a high dosage of sole cement and a long time of curing (at least 28-day) are needed, which may be uneconomical and lade to the brittle behavior. Adding zeolite (≤ 25% proportion) to supplant part of cement could effectively enhance the engineering properties of cement-mixed soil, due to an increase in the cementitious products [e.g. Calcium-aluminate-hydrate (CAH) and Calcium-silicate-hydrate (CSH)] induced by the pozzolanic activity, subsequent reduction of the inter pore-spaces and eventually a more compacted microstructure, as confirmed by the X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images. It should be emphasized that the zeolite/cement ratio is a very influential factor on the behavior of cement-zeolite mixture. Therefore, the cemented soil mixes with Zopt showed a further (up to 1.3 folds) resistance relative to the mere cemented soil as well as a greater tensile strength; however, the binary system was still vulnerable under the F-T action. In this case, the insertion of fiber could significantly enhance the soil durability (decrease the degree of damage by an average value of 50%), which was more evident at the small binder dosage and early stage of curing time. Incorporating fiber into the system also led to a higher tensile strength (nearly 1.5 times) than those deduced from the stabilization alone. Moreover, this strategy was effective to overcome the brittle nature of stabilized mixes, resulting an increase the post-strength up to 270%. These observations can be justified by the extended cementing gels formation and the enhanced interlocking of matrix through the CZ-fiber application. Overall, the combination of CZ blend and fiber can be considered as an effective technique for the soft soil modification with the fact that triggered a prominent reduction (~ 30%) in the needed amount of cement an time of curing (up to 3 folds) for the successful treatment against the F-T cycles.

Despite the wide application of de-icing substances to the roadways, the sewage produced can have negative impacts on local ecosystems. Hence, the present study was conducted for assessing the effects of road salt use throughout the winter in Hamedan on the hydro-chemical quality of Hamedan-Bahar basin. Hamedan is one of the major tourist destinations and one of the main agricultural poles in Iran, and thus, its water resources contamination may pose serious risk to the health of the whole country.

The modeling of under-ground water flow paths in the study area revealed that the flow of rain and snow water in the city is mainly towards Hamedan-Bahar basin (as one of the main drinking water and agricultural water supplies in the region). Therefore, the 24 wells in the study area were sampled and the hydro-chemical characteristics of the obtained water samples as well as their changing trends over the past 10 years were determined and analyzed.   

The results indicated a gradual increase in the minerals and solid materials in the water of the basin. This, considering the meaningful correlation values obtained (R2≥0.89) between the salt contents and Cl- and Na+ concentrations, could be attributed to the use of de-icing materials. The rate of pollutants in some of the samples was found to be 10 times as much as the permissible national standard and international values. Moreover, based on the Wilcox diagram, the water in most stations could be classified as C3S1 (decreasing the soil fertility and resulting in ecophysiological abnormalities in crops) and even as C4S1 (completely harmful for irrigation). A similar distribution of de-icing compounds and arsenic were observed in the under-ground water of the basin. 

The increase in the pollution and the decline in hydro-chemical properties of the basin due to the accumulation of de-icing materials, not only pose direct hazardous effects to human health and agricultural lands but can also intensify the mobility of the heavy metals in soil-water profiles of the region. Therefore, it is suggested that winter operations in the city be planned and carried out using modern methods and facilities (such as anti-icing program, eco-friendly deicers, asphalt mixture with anti-icing additives, hydronic heating pavement), so that the negative environmental impacts can be controlled as much as possible.

In this study, the effects of two types of by-product materials resulting from the manufacture of iron including GGBS and BOFS on the hydro-mechanical performance of a lime-stabilized clayey soil were investigated. The results indicate that the addition of slag particularly of GGBS has a less impact on the soil engineering properties as compared to lime treatment. It was found that the lime-slag (LAS) combination decreases the water retention potential, controls the soil settlement and causes a considerable increase in the mechanical capacity. The composite clay sample containing LAS exhibits a better performance than that of lime-treated soil particularly at short time of curing.

Stabilization/solidification (S/S) has emerged as a cost-effective method for treating a variety of wastes, particularly heavy metal (HM) contaminated soils. Among the many available fixing agents, Portland cement (PC) has been used extensively for the remediation of contaminated sites. However, there are significant environmental and technical impacts associated with PC application. Thus, the present research was conducted to address the efficacy of cement and nano-clay mixture in enhancing the S/S process. In so doing, artificially contaminated soils were first prepared by mixing kaolinite with zinc (Zn) at levels of 0 to 2%. Afterward, tow type of nano-clay (Na-Montmorillonite and Na-Cloisite), cement and cement/nano-clay (CNC) were separately added to the sample, and then, a set of macro and micro level experiments including batch equilibrium, pH, toxicity characteristic leaching procedure (TCLP), unconfined compression strength (UCS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analyses were carried out at various curing periods (1, 7 and 28 days) to assess the effectiveness of the additives. The results obtained show that the addition of nano-clay can increase the HM retention capability of soil; however, this may be partly lost when the treated soil are subjected to acidic TCLP solution. In addition, with increasing the HM content, due to the decrease in buffering capacity of system and the restructuring of the clay particles, the soil remediation potential at presence of nano-clay is decreased considerably. It was found that the application of sole cement may significantly enhance the HM retention capacity of soil. But in this case, the physicochemical reactions of Zn ions with cement could hinder and/or reduce the generation of hydration products phases such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), resulting in the degradation of cementation structure-bonding of S/S matrix, as clearly confirmed by the formation of calcium zincate and the diminution in the cementitios compounds peak intensity in the XRD patterns of cement-treated soils. Therefore, the leaching characteristics and the mechanical properties of the S/S material with sole cement are adversely affected by increasing the amount of HM ions. As a result, a large quantity of cement (20 wt% per one percent of HM) and a long time of curing (≈ 28 days) should be employed to meet the full needs of HM immobilization in contaminated soil and give the EPA-acceptable UCS value (≥ 0.35 MPa). The TCLP and XRD test results indicate that the cement/nano-clay combination can expedite the S/S process and alleviate the deleterious influences of metal ions and acidic attack on the stabilized sample. The EDX analyses also support the increase in the development of hydration reactions and the formation of cementing materials in the presence of CNC, providing the enhancement of binding capacity that will lead to the greater strength (up to 50%) in comparison to cement application. Hence, the CNC binary system is more efficient in modifying the contaminated soil with a lower amount of binder (to about 40%) and shorter curing ages (by nearly 4 times) than that of the sole cement. Overall, it is concluded that the cement/nano-clay mixture can be utilized as an effective S/S amendment and CNC content of 15 wt% per 1% of HM can successfully remediate the contaminated soil after 7 days of curing.

In the CFRD dams, a concrete-face with a finite thickness is placed on the upstream side of the dam, which prevents water leakage from the reservoir. The construction of these dams with different heights and various specifications of materials have been welcomed a lot. Therefore, construction of CFRD is appropriate in pumped-storage reservoirs. However, due to the important role of concrete-face, the necessity of optimal studies in order to evaluate the behavior of this type of dams is obvious. In this research, the lower reservoir of Siah Bishe was studied by finite element method in order to investigate the interaction between rock-fill materials and simulated concrete-face and by an appropriate behavioral model in a three- dimensional mode that can simulate the behavior of materials in the body of the dam well. In this research, Plaxis software was used for modeling and static analysis was performed to determine deformations and stresses made in the dam and concrete slab. The elastoplastic behavioral model of Mohr-Coulomb was used to model the behavior of the materials and the technical specifications of the materials used in the body of the dam and concrete-face slab have been applied. The maximum value of settlement calculated by the software from the beginning of the constriction to filling the reservoir under the effect of gravity is 670 millimeter and the maximum settlement after phase 3 in the mode of the full reservoir in long term is 32 millimeter and the maximum horizontal displacement is 52 millimeter. Finally, the results of the settlements were compared to results of the instrumentation. The results indicate the approximation of results of the numerical modeling with results obtained from instrumentation.

Expansive clayey soils can undergo periodic volumetric changes in the form of ground heave and settlement when subjected to moisture fluctuations. Such changes may lead to exert stress and serious problems to geotechnical structures if not adequately taken care of. Lime continues to be commonly used for treatment of these type soils; however, some restrictions are associated with its application. Therefore, in the present study a series of macro and micro level tests including swelling potential, unconfined compression strength (UCS), consolidation, pH and electrical conductivity (EC), adsorption, X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were carried out at various curing periods (1, 7, 28 and 90 days) and different temperatures (10, 20, and 40 °C) to assess the effects of environmental condition and SiO2-nanoparticles (NS) on the performance of lime treatment. To achieve the stated objective, lime and lime/NS (LNS) mixture were separately added to highly expandable clay at wide ranges from 0% to 30% by mass, respectively. The results obtained show that the environmental temperature, especially in the initial time of curing, has a prominent role on the geo-mechanical properties of lime treated soil samples. It was also found that the reduction in the temperature particularly at inadequate curing (lower than 28 days) provides a deleterious impact on the pozzolanic activity and decrease the formation of cementing compounds such as Calcium-Silicate-Hydrate (CSH) and Calcium-Aluminate-Hydrate (CAH) gels. In this case, the process of soil modification is mainly due to the short-term reactions (i.e. cation exchange and increase in osmotic pressure), increasing the amount of additives (up to two times) to control the swelling power. On the other hand, the incorporation of SiO2-nanoparticles into the binder system causes a reduction in the detrimental effects of low temperature on the engineering parameters of lime-treated products and decreases their sensitivity to the time of curing. The samples amended with the LNS blend exhibit a continuous development of soil mechanical capacity as the additive content increased. They are less deformable and show a decrease in their compression index by nearly 40% as compared with sole lime. Based on the XRD and SEM experiments, the superior influences of LNS are mainly ascribed to the higher and faster formation of cementitious compounds. In fact, at the presence of LNS, due to direct interaction of lime and silica from NS, the silicate gel can be immediately formed to coat and bind the clay particles together; whereas, with the addition of lime alone, the gel produces only by the removal of silica from the clay minerals that needs further time to complete its formation and hence the lower modification was occurred, especially at curing time shorter than 28 days. Moreover, NS reduces the pores sizes and serves to distribute the new crystalline phase (e.g. CSH gel) in a more homogenous fashion in the available space. This micro-structural reorganization upon the LNS treatment could rapidly block off the soil voids and greatly interlock the clay particles together that provide higher environmentally-stable materials with lower cost and energy as compared to standalone lime. It is finally concluded that the utilization of LNS mixture gives a promising way for increasing the efficiency of lime stabilization and decreasing the additive consumption.

The continuous accumulation of toxic materials such as heavy metals in soil due to interaction with industrial and domestic wastes has contributed to an extensive health hazards. Therefore, the aims of this study are to evaluate the ability of cement (as a chemical adsorbent) in remediation of contaminated soil and to compre the obtained results by the physical adsorption method through the addition of active smectite clay mineral.
To achieve the mentioned objectives, kaolinite soil in the laboratory conditions was contaminated with solutions containing 0 to 1 M concentration of Pb (NO3)2 in 1:10 ratio. Adding different percentages of cement and smectite to each sample, and after equilibrating, changes in pH and concentrations were determined. Tests of hydraulic conductivity (permeability), unconfined compression strength (UCS), toxicity characteristic leaching procedure (TCLP) and SEM were also performed to evaluate the impact of adsorbent type on reduction of the of pollution transportation potential.
Findings: The results indicate that at low concentrations of contaminants (up to 50 cmol/kg.soil), the type of absorbent does not have much influence on the heavy metals removal from contaminated soils. It was found that with the increase of the pollutant concentration and due to the buffering capacity reduction and the restructed clay mineral, the possibility of soil remediation through the physical absorption method is greatly decreased. Unlike the smectite limitation encountering with contaminated soil containing the heavy metals, the cement has a high adsorption capacity to adsorbe heavy metals. In the same content of adsorbent and with the increase of the Pb concentration, the amount of its reduction in the presence of cement is 15 times more than what observed in the presence of smectite. In addition, it can be seen that the particles solidification in the samples containing cement improves the engineering properties of materials, causes to trap the pollutants within the soil mass and consequently reduces the leaching and emission capability of pollutants as compared to the physical attraction method.
According to the results, using the physical adsorption to remove the heavy metals from contaminated soils (particularly at high concentrations of contaminant) is not recommended. Unlike the smectite limitation encountering with contaminated soil, application of cement is very effective to remove contaminants from the soil due to the combination of two mechanisms of stabilization and solidification. In appropriate remediation condition and with respect to EPA criteria, application of 0.1% of cement per 1 cmol/kg.soil contamination leads to safe remediation of the heavy metals from in contaminated soils.

The electrokinetic (EK) approach is one of the popular choices for the extraction of inorganic contaminants (e.g. heavy metals) from a soil matrix. On the other hand, many factors can affect the performance of EK contaminant remediation. Therefore, in the present study a series of macro and micro level tests including electrokinetic experiments, pH and electrical conductivity (EC), adsorption and desorption, X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were performed to investigate the effects of time and pore fluid characteristics on the efficiency of EK remediation. For this purpose, the kaolinite clay was separately infected with different solutions containing zinc nitrate and lead nitrate in concentrations of 20 and 40 cmol/kg and then electrokinetic experiments on a laboratory scale were conducted at 2 V/cm voltage gradient in time periods of 3, 6, 12, 24 and 48 days. Nitric acid was also used as a catholyte solution to enhance the soil remediation process. The results obtained show that the soil response to the EK remediation is a function of the contaminant characteristics, the pH of soil-electrolyte system and the time of testing. In EK contaminant remediation from a soil matrix, it is significant to pay particular attention to the effect of the concentration and type of contaminant on the applicability and efficiency of this method. The results reveal that under the same conditions, especially in the low times, extraction efficiency from samples containing lead was measured approximately 70 percent of the samples containing zinc. This is because the lead tends to more adsorbe on the clay surface and has a greater tendency to form precipitate. In addition to the type of contaminants, it was found that the increase in concentration of contaminants in the soil through a series of physical-chemical reactions accelerates clean up capabilities, particularly in the initial time period of the EK experiments. Catholyte conditioning with acidic solution enhanced the removal of heavy metals, which is mainly due to microstructural changes and an increase in the mobility of pollutants. In fact, based on the X-ray diffraction and scanning electron microscope analyses, the microstructural characteristics and the arrangement of the clay particles have an important role in the process of electrokinetic soil remediation. The formation of flocculated structure decreases the retention capacity of the clay particles and also increases the flow path, which enhance the efficiency of pollutant extraction. It was found that the soil remediation, especially in the parts close to the anode, greatly enhanced with increase the time of EK test; however, the further increase in time had a limited impact on results, especially in the samples containing high concentrations of zinc. This indicates that there is an optimum time in the process of cleaning up heavy metals from the soil by EK method, which depends on the type and concentration of contaminant. Moreover, it was seen that the extent of contaminant removal from anode side towards the cathode side is considerable when catholyte conditioning with acidic solution is used. In other words, reducing the pH of soil-electrolyte system has a significant impact in increasing the efficiency of pollutant extraction.

Expansive clayey soils، which are predominantly distributed throughout the world، have complicated behavior. Heaving and settling in these soils may pose considerable problems and severe damage to structures that come into their contact or constructed out of them and consequent distress to people if not adequately taken care of. Granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOS) are two types of by-product materials resulting from the manufacture of iron that are produced in large amount throughout the world. The proper disposal of such byproducts is one of the major issues for environmentalists since leaving them to the environment directly may cause health problems. Hence، the aim of this study is to investigate the potential use and effectiveness of expansive soils treatment using GBFS and BOS. To achieve the objectives، the admixtures were added to the clay smectite samples in proportion of 0 to 30% by weight and tests of the pH value، electrical conductivity (EC) measurement، Atterberg limits، swelling، unconfined compression strength (UCS) and X-ray diffraction analysis were performed on those samples at different curing period (i. e. 1، 3، 7، 14، 28، 45 and 90 days). Lime as a conventional additive was also used to evaluate the performance of GBFS and BOS. The results reveal that in the limited curing condition (i. e. less than 3 days) and with the addition of 20% slag، the swelling could be eliminated mainly due to the short term reactions (i. e. cation exchange and osmotic pressure increasing). On the other hand، based on the X-ray graphs it was found that with appropriate curing (more than 7 days) and due to the growth of the cementation compounds such as calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH)، especially in samples containing BOS، the needed slag to control heave potential will be declined up to 4 times. The presented results indicate that highly expansive clayey soils can be stabilized satisfactorily by lime and following adequate curing due to development of the pozzolanic reaction. Beside، with a further increase in the lime content، the pozzolanic activity can not continuously take place and the excessive addition of lime caused a reduction in the mechanical capacity. On the other hand، the samples containing slag show a progressive increase in the strength with increasing the additive content and could overcome the difficulties associated with the use of lime. For example، the USC of smectite sample with 30% BOS and after 90 days of curing was almost 12 times higher than the untreated sample. However، in the presences of GBFS due to lower solubility and limitation of pozolanic activity the lower change was observed. The The macro and micro level experiments results of this study indicate that the utilization of iron and steel slags especially basic oxygen furnace slag (BOF) is a good alternative for lime stabilization which reduces the cost of soil treatment project and help the management of these byproducts.

Researchers use smectite in different geotechnical and geo-environmental projects, such as industrial/municipal waste disposal sites and cut-off walls due to its specific properties. On the other hand, previous researches show that the load conditions, and pore fluid properties may significantly affect the behaviour of clayey soils. In spite of several researches that have been conducted on the engineering behaviour of smectite clays, there has been little attention to the influence of pore fluid changes and temperature increase on the geotechnical and geo-environmental properties of smectite. In this research, the influence of pore fluid properties changes and temperature on thephysico-mechanical behaviour of smectite has been Experimentally investigated. This study has been performed from micro-and macro-structural points of view. Due to the vast applications of smectite in geotechnical and geo-environmental engineering projects, this study focuses on a smectitic soil sample behaviour. The geotechnical properties of soil were determined based on the ASTM Standard [1]. The geo-environmental engineering properties of soil were measured by the method presented by Yong et al. [2]. The pore fluid analysis was performed by GBC 932 Plus atomic absorption spectrophotometer. Tables 1 and 2 show the geotechnical and geo-environmental engineering parameters of smectite sample. To investigate the possibility of changes of smectite behaviour due to the changes of pore fluid properties, the influence of calcium and sodium ions upon smectite behaviour was studied. These two cations are the most common cations that might be found in different sites. For this purpose, calcium sulfate and sodium sulfate in concentration of 0 to 1 normal was used. In addition, due to the importance of swelling and water retention properties of smectitein its application as barrier in geotechnical and geo-environmental projects, a part of experiments has focused upon swelling properties change of smectite sample. Finally, by performing a series of experiments related to the interaction process of soil-water including suction and swelling, the change in smectite behaviour due to thetemperature effect was investigated. For this purpose, saturated smectite samples were kept in four different. The achieved results indicate that due to the interaction of smectite with different electrolytes and with increasing the electrolyte concentration, the density of samples increase while the external load kept constant. This increase in density is attributed to the smectite-electrolyte interaction. A reduction in repulsive forces among clay particles was responsible for such a decrease in soil void ratio at constant external loading. Furthermore, the achieved XRD results indicate that after the interaction of clay particles with electrolyte, with increasing the electrolyte concentration, the position of basal spacing of smectite remains constant while theintensity of major smectite's peak decreases. This is attributed to the flocculated fabric due to the change in electrostatic forces among clay particles [3]. On the other hand, since hydraulic conductivity in clayey soils is a function of such a force among particles, the permeability of different smectite sample at different electrolyte concentration was evaluated. According to the results of Figure 1, the permeability may increase as much as 100 times after exposure of sample to different electrolyte concentration. In the last section of this research, the free swelling of smectite samples was measured after different levels of heat treatment from 25 to 200 oC. The results show a 16% reduction in swelling percentage of smectite after heat treatment. The achieved results of this study show that due to the interaction of different electrolytes and due to the temperature change, the water retention of smectite and its mechanical behaviour will be changed. This change in some cases was more than 50%. The results of micro-structural experiments show that the main reason for these changes in smectite behaviour after the interaction with electrolyte and temperature rise, was due to the change in morphology and new soil structure of smectite particles. In fact, the micro-structural change has affected the macrobehaviour of smectite.