جستجوی مقالات مرتبط با کلیدواژه « حرارت » در نشریات گروه « عمران »

Bentonite is commonly used as a liner in landfills to prevent the leaching of the waste leachate to the groundwater (Yong et al., 1992; Abollino et al., 2003; Zhan et al., 2022). Sodium-bentonite and calcium-bentonite are among the useful materials for this purpose. On the other hand, in several cases clayey soils are exposed to high temperature in engineering and geo-environmental engineering projects (Tan et al., 2004). Dehydration and de-hydroxylation are the two major phenomena during heating process of clayey soils (El Warid et al., 2022). In spite of several researches on the interaction of heavy metals and clayey soils, there are lack of research on the subject of mutual effect of temperature and double layer cation type on the adsorption of heavy metals in clayey soil. Therefore, the main objective of this paper is to investigate on the impact of temperature and type of double layer cation on adsorption of copper heavy metal by the clayey soils with high plasticity index. To achieve the above mentioned objective, calcium chloride salt was used to make homo-ionic bentonite. Several types of geo-environmental engineering experiments were performed to address and to achieve the above mentioned objective.

In this paper, the performance of box steel columns with corrosion is investigated. Thus the steel columns are made with different defect locations (6 modes) and are subjected to temperatures of 20 °C and 700 °C. Then, two retrofitted methods (CFRP composites and steel plates) are used in the defect area in order to improve the performance of columns. Afterwards, bearing capacity of all column specimens (38 specimens) has been obtained. The results indicate a decrease in the bearing capacity of the columns and weakness in their performance due to the two factors of defect and heat so that the greatest decrease in the column compression strength is about 32% and 35% due to defect and high temperature, respectively. Also, the comparison of retrofitting methods indicates that the use of composite is more effective in improving the performance of steel columns. Finally, For further investigation, 5 specimens are modeled in ABAQUS finite element software and the results are compared with similar experimental results.

At about 8.00 am of 20th December 2015, a fire started in a shop in Plasco building, located in center of Tehran, which resulted in tragic collapse of the building and claimed the lives of 22 fire fighters and other people. According to the findings of the investigations, the main reason of ignition was non-permitted extension of cablings in the shop of origin of fire; for use of electrical heating devices. This incident took the attention of Iranian society, Engineers and authorities to the need of improvement of fire safety of buildings. Plasco was collapsed after about three and a half hours of the ignition. Therefore the question was arisen how the scenario of the fire growth and temperature rise in the building was. The place of the building and depot of debris were visited and examined by special teams. Steel, concrete and other materials, which some of them were molten due to high temperature, was taken from the debris for further experimental works. Different tests were carried out on the samples. Heat release rate of textiles was discussed in another article. In this paper; the results of physical, mechanical and XRD/XRF tests and mineralogy/petrography examinations have been presented. The most tests carried out on the concrete samples taken from the ceiling system of the building. For comparison purposes, samples were also taken from the apparently non exposed ceilings. A number of these un-exposed samples were tested in a fire resistance furnace and their changes were utilized as a reference for comparison with samples of burnt sections of the building. The results revealed that the concrete cores taken from the fire exposed ceilings had experienced temperatures between 500-700 ᵒC. Taking the thermal and physical properties of concrete into account; this revealed that the gas temperature of fire in Plasco was much higher than these amounts. This was in agreement with findings of FDS modeling, which was presented in another paper and showed temperatures of about 1000-1100 ᵒC occurred in some parts of the building in fire. On the other hand, molten blends of different materials were seen in the debris, comprising molten metal, glass and cementitious materials. It showed that temperatures about 1400 ᵒC could be occurred in the incident. But these temperatures are not usually seen in enclosure fires; rather it must be happened under the debris. Fifteen stories were collapsed at the end of tragedy. In that time, the massive amounts of textiles and other combustibles were burning in five upper stories, while there were still large quantities of textiles and clothes in the lower stories. So, after the collapse of the building, all combustible materials and even gasoil fuel stored in tanks in the basement could be burnt under the debris, approved by observations in next days during the operation of extinguishment and removal of debris. The failed construction systems comprised large panels and steel elements; therefore air flow was possible under the debris for supporting the combustion. On the other hand, large amounts of debris made a relative thermally insulated condition, especially in lower parts, which could produce a temperature rise considerably higher than recorded in enclosure fires. The observation of molten blends of cementitious materials supported this assumption and it was also in agreement with possible maximum temperatures in adiabatic combustions of hydrocarbons, which are far higher than these figures.

Temperature changes the engineering behavior of clay soils. Clay soils are used as a protective cover for burial of high-level wastes (HLWs), where the soil is exposed to medium to high temperature regimes. Marls are a type of sedimentary deposits consisting of clay minerals and calcium carbonate. These two components can substantially influence the behavior of marl soils from an engineering standpoint. The present study focuses on the engineering characteristics of marl soils under various temperature regimes with an emphasis on the microstructural changes in permeability coefficient, settlement, and compressive strength Therefore, after determining the geotechnical properties of the marl soil, its samples were exposed to temperatures from 25℃ to 900℃. The changes in marl soil properties were analyzed via mechanical tests (measuring permeability, consolidation, and uniaxial compressive strength), and microstructural tests (measuring pH and X-Ray diffraction), and scanning electron microscopy (SEM). The microstructural analysis of marl soil samples indicates that due to the deterioration and formation of new minerals as well as soil particle arrangement and microscopic texture; temperature regimes increase the permeability coefficient. However, at 700℃ the formation of cement compounds reduces permeability coefficient by an approximate factor of 50,000.

Sandstone shrinks on heating, and therefore, it counteracts to some extent the expansion of the quartz grains. The loss in strength of sandstone mortars on exposure to fire is, however, often high, and therefore sandstone does not form a good fire-resistant aggregate. This paper deals with an experimental study on the post-heat performance of cement mortars containing silica fume and granulated blast-furnace slag (GBFS). In doing so, the mortar specimens were provided in standard formworks to perform compressive, tensile and flexural tests containing 7, 14 and 21% of pozzolanic materials as a replacement for cement. Moreover, for the sake of heating process, the specimens were placed in an electric furnace exposed to temperatures of 25, 100, 250, 500, 700 and 9000c with standard temperature increment and once the heating process ended and the specimens were cooled, the tests were carried out on them. Based on the results obtained, the maximum effect of utilizing granulated blast-furnace slag (GBFS) and silica fume respectively takes place in low (up to 2500c) and high (5000c and greater degrees) temperatures. Quantitatively, the compressive, tensile and flexural strengths were raised by 73 and 180%, 45 and 100%, 106 and 112%, respectively in low and high temperatures. In addition, as the temperature rises, the particles of specimens containing silica fume and granulated blast-furnace slag (GBFS) shrinks less in size compared to the reference specimen.

In this paper, the effect of adding fiber to lightweight (containing Light Expanded Lica Aggregate) self-compacting concrete under high-temperature conditions (25-100, 250-500, 700 ° C) was investigated in the form of compressive, tensile and flexural strength tests. In these experiments, 3 types of fibers, including steel fiber, and polypropylene and steel springs, were used for 0.4% volumetric rate of concrete. In general, the results indicate that the use of steel fiber and spring increases the compressive strength of concrete by up to 20%. Polypropylene fiber can be used to improve the tensile strength of concrete, because it increases up to 70% tensile strength after high temperature conditions. Also, at a temperature of 700 °, the flexural strength of all samples was negligible and were destroyed due to their own weight. Also, due to the severe drop in resistance after a temperature of 500 ° C, after this temperature, self-compacting concrete is not serviceable.

Use of common bers, in addition to increasing ductility, toughness, rst point cracking, and ultimate strain, plays a major role in preventing shrinkage and thermal cracks. The role of temperature in ber bridging and change of material structure has been investigated in previous studies. Use of waste materials in structural materials can decrease further pollution of ecosystem. On the other hand, increase in oil and polymer-based waste materials, caused some concern in the international community because of the adverse environmental impact of this material. For this reason, in this research, steel ber (0.4, 0.5 and 0.6), Polypropylene ber (0.03, 0.05 and 0.1), and recycled Polyethylene terephthalate (PET) ber (0.2, 0.3 and 0.4) percent of the concrete mixture volume were used. The results of the rheological (V-funnel, T50, Slump and L-Box), mechanical properties (e.g., compressive, exural, and splitting tensile strength) and Ultrasonic Pulse Velocity (UPV) Test of self-compacting concrete exposed to temperatures of 20, 200, 300, 400, and 600 showed that high contents of bers did not satisfy some rheological and mechanical aspects of self-compacting concrete. Steel bers increased the compressive, exural, and splitting tensile strengths of concrete with maximum amount of 9.8% and two other bers cause 15% decrease in strength of unheated specimens at most. Fiber reinforced specimens had an increase in resistance in the range of 8 to 21% by heating specimens to600 . The exural strength of steel ber reinforced specimens had an increase of maximum 30% for unheated ones. PET and P.P. ber reinforced specimens had 9 to 20% increase in exural strength. The presence of bers increases the mechanical strength, toughness, and ductility of concrete and prevents loss of strength and spalling phenomenon at high temperatures, as well as having a fundamental role in the reduction of heat, microcracks, and retaining fundamental structure of concrete.

The use of fiber reinforced polymer (FRP) composites is ever growing in the construction industry. High strength- weight ratio, corrosion resistance and suitable durability are the main criteria for FRP selection and design. However, in case of high temperature exposure, change in the material properties affects the overall structure performance. The aim of this study is to evaluation the effect of cement and epoxy adhesives on the thermal performance of concrete flexural specimens strengthened with basalt (BFRP) and glass (GFRP) fabrics. Therefore, 105 flexural specimens (100 × 100 × 500 mm) were made by a constant water-cement ratio; and were kept under the 50°, 100° and 200°, for a period of one and three hours, respectively. The results show that increasing the temperature led to decreased flexural strength of unreinforced specimens by 48%. Also, flexural strength of cement and epoxy adhesives impregnated specimens decreased up to 47% and 60% respectively. Results from the presented model shows at temperatures lower than 100 0C, flexural strength of cement adhesive impregnated specimens was lower than epoxy adhesive impregnated specimens; but at 200 0C, flexural strength of specimens strengthened with basalt and glass fabrics increases 1.3 and 1.15, respectively. Also, curve for flexural strength of specimens strengthened with basalt fabrics compared to glass fabrics had an ascending trend, while it had a descending trend for epoxy adhesive impregnated specimens.

The most fundamental subject in applicable studies of fire in civil engineering is to evaluate fire load, which is affected by life style and consumable objects of the users. This subject has been considered more in countries like India, New Zealand, Canada and Finland, due to usage of structures sensitive to fire, like wooden structures. In this article, while defining the criteria for fire load evaluation and sampling from a number of residential buildings in Shiraz, the results of the researches done in other countries on fire load is compared with the results achieved in our country, Iran. Meanwhile various approaches of counting burning calories of different places and different household materials are explained. The results of this research are presented in different categories like the area of the residency, story number, sexuality of the users, application of the room and etc. plus a formula for evaluation of fire load in Iranian residential buildings is provided. This Formula, named after main writer of this article, Haji Beig Tehrani, is provided based on statistical studies, using different coefficients and the average fire load of a residential building in Iran. Concluding from this research, fire load in Iranian residential buildings is 541.8 Mega joules per square meter in average which is a high value, compared to other countries.

C‌l‌a‌y‌e‌y s‌o‌i‌l‌s m‌a‌y b‌e e‌x‌p‌o‌s‌e‌d t‌o d‌i‌f‌f‌e‌r‌e‌n‌t h‌e‌a‌t g‌r‌a‌d‌i‌e‌n‌t‌s w‌h‌i‌c‌h c‌a‌u‌s‌e p‌e‌r‌m‌a‌n‌e‌n‌t o‌r s‌e‌m‌i-r‌e‌v‌e‌r‌s‌i‌b‌l‌e v‌a‌r‌i‌a‌t‌i‌o‌n‌s i‌n t‌h‌e‌i‌r e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g b‌e‌h‌a‌v‌i‌o‌u‌r. T‌h‌e u‌s‌e o‌f c‌l‌a‌y‌e‌y s‌o‌i‌l i‌n c‌o‌n‌s‌t‌r‌u‌c‌t‌i‌o‌n m‌a‌t‌e‌r‌i‌a‌l‌s a‌n‌d t‌h‌e a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n o‌f b‌e‌n‌t‌o‌n‌i‌t‌e a‌s b‌a‌r‌r‌i‌e‌r m‌a‌t‌e‌r‌i‌a‌l i‌n a‌t‌o‌m‌i‌c w‌a‌s‌t‌e d‌i‌s‌p‌o‌s‌a‌l a‌r‌e a‌m‌o‌n‌g c‌a‌s‌e‌s i‌n w‌h‌i‌c‌h c‌l‌a‌y‌e‌y s‌o‌i‌l‌s a‌r‌e s‌u‌b‌j‌e‌c‌t‌e‌d t‌o h‌e‌a‌t g‌r‌a‌d‌i‌e‌n‌t f‌r‌o‌m l‌o‌w t‌o h‌i‌g‌h r‌a‌n‌g‌e‌s. T‌h‌e r‌e‌v‌i‌e‌w o‌f p‌r‌i‌o‌r r‌e‌s‌e‌a‌r‌c‌h i‌n‌d‌i‌c‌a‌t‌e‌s t‌h‌a‌t p‌r‌e‌v‌i‌o‌u‌s s‌t‌u‌d‌i‌e‌s h‌a‌v‌e m‌a‌i‌n‌l‌y f‌o‌c‌u‌s‌e‌d o‌n t‌h‌e m‌e‌c‌h‌a‌n‌i‌c‌a‌l a‌n‌d m‌a‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌a‌l b‌e‌h‌a‌v‌i‌o‌u‌r o‌f s‌o‌i‌l. I‌n o‌t‌h‌e‌r w‌o‌r‌d‌s, t‌h‌e‌r‌e i‌s l‌i‌t‌t‌l‌e r‌e‌s‌e‌a‌r‌c‌h e‌m‌p‌h‌a‌s‌i‌z‌i‌n‌g t‌h‌e s‌o‌i‌l m‌i‌c‌r‌o‌s‌t‌r‌u‌c‌t‌u‌r‌e i‌n t‌h‌i‌s p‌r‌o‌c‌e‌s‌s. T‌h‌i‌s r‌e‌s‌e‌a‌r‌c‌h i‌s a‌i‌m‌e‌d t‌o i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e t‌h‌e c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c c‌h‌a‌n‌g‌e‌s o‌f k‌a‌o‌l‌i‌n‌i‌t‌e a‌n‌d b‌e‌n‌t‌o‌n‌i‌t‌e d‌u‌e t‌o h‌e‌a‌t t‌r‌e‌a‌t‌m‌e‌n‌t f‌r‌o‌m m‌i‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌a‌l a‌s‌p‌e‌c‌t‌s. T‌o a‌c‌h‌i‌e‌v‌e t‌h‌i‌s o‌b‌j‌e‌c‌t‌i‌v‌e, t‌h‌e s‌o‌i‌l s‌a‌m‌p‌l‌e‌s w‌e‌r‌e e‌x‌p‌o‌s‌e‌d t‌o d‌i‌f‌f‌e‌r‌e‌n‌t h‌e‌a‌t r‌e‌g‌i‌m‌e‌s; f‌r‌o‌m 25 t‌o 1100 c‌e‌n‌t‌i‌g‌r‌a‌d‌e. A‌f‌t‌e‌r m‌e‌a‌s‌u‌r‌i‌n‌g t‌h‌e v‌a‌r‌i‌a‌t‌i‌o‌n‌s g‌e‌n‌e‌r‌a‌t‌e‌d i‌n t‌h‌e u‌n‌c‌o‌n‌f‌i‌n‌e‌d c‌o‌m‌p‌r‌e‌s‌s‌i‌o‌n s‌t‌r‌e‌n‌g‌t‌h o‌f t‌h‌e h‌e‌a‌t‌e‌d s‌a‌m‌p‌l‌e‌s, b‌y a s‌e‌r‌i‌e‌s o‌f X‌R‌D a‌n‌d S‌E‌M e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌s, t‌h‌e m‌i‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌a‌l c‌h‌a‌n‌g‌e‌s i‌n t‌h‌e s‌o‌i‌l s‌a‌m‌p‌l‌e‌s w‌e‌r‌e e‌x‌a‌m‌i‌n‌e‌d a‌n‌d t‌h‌e‌i‌r i‌m‌p‌a‌c‌t u‌p‌o‌n t‌h‌e m‌a‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌a‌l b‌e‌h‌a‌v‌i‌o‌u‌r w‌a‌s a‌d‌d‌r‌e‌s‌s‌e‌d. T‌h‌e r‌e‌s‌u‌l‌t‌s i‌n‌d‌i‌c‌a‌t‌e t‌h‌a‌t t‌h‌e i‌n‌t‌e‌r‌p‌r‌e‌t‌a‌t‌i‌o‌n o‌f v‌a‌r‌i‌a‌t‌i‌o‌n‌s i‌n t‌h‌e s‌t‌r‌e‌n‌g‌t‌h o‌f t‌h‌e h‌e‌a‌t‌e‌d s‌a‌m‌p‌l‌e‌s c‌a‌n b‌e e‌v‌a‌l‌u‌a‌t‌e‌d b‌y m‌o‌n‌i‌t‌o‌r‌i‌n‌g t‌h‌e s‌o‌i‌l m‌i‌c‌r‌o‌s‌t‌r‌u‌c‌t‌u‌r‌e, s‌u‌c‌h a‌s d‌e-h‌y‌d‌r‌o‌x‌y‌l‌a‌t‌i‌o‌n, a‌n‌d t‌h‌e f‌o‌r‌m‌a‌t‌i‌o‌n o‌f n‌e‌w m‌i‌n‌e‌r‌a‌l‌s a‌f‌t‌e‌r h‌e‌a‌t t‌r‌e‌a‌t‌m‌e‌n‌t. A‌c‌c‌o‌r‌d‌i‌n‌g t‌o t‌h‌e a‌c‌h‌i‌e‌v‌e‌d r‌e‌s‌u‌l‌t‌s, t‌h‌e e‌x‌t‌e‌n‌t o‌f t‌h‌e i‌n‌f‌l‌u‌e‌n‌c‌e o‌f h‌e‌a‌t t‌r‌e‌a‌t‌m‌e‌n‌t u‌p‌o‌n s‌o‌i‌l b‌e‌h‌a‌v‌i‌o‌u‌r i‌s a f‌u‌n‌c‌t‌i‌o‌n o‌f t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e l‌e‌v‌e‌l a‌n‌d c‌l‌a‌y m‌i‌n‌e‌r‌a‌l t‌y‌p‌e. F‌u‌r‌t‌h‌e‌r‌m‌o‌r‌e, b‌y i‌n‌c‌r‌e‌a‌s‌i‌n‌g t‌h‌e t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e u‌p t‌o d‌e-h‌y‌d‌r‌o‌x‌y‌l‌a‌t‌i‌o‌n l‌e‌v‌e‌l, a‌n i‌n‌c‌r‌e‌a‌s‌e i‌n s‌o‌i‌l s‌t‌r‌e‌n‌g‌t‌h i‌s o‌b‌s‌e‌r‌v‌e‌d. T‌h‌i‌s i‌s m‌o‌r‌e n‌o‌t‌i‌c‌e‌a‌b‌l‌e f‌o‌r b‌e‌n‌t‌o‌n‌i‌t‌e, d‌u‌e t‌o t‌h‌e p‌r‌e‌s‌e‌n‌c‌e o‌f a‌c‌t‌i‌v‌e c‌l‌a‌y a‌s i‌t‌s m‌a‌i‌n c‌l‌a‌y f‌r‌a‌c‌t‌i‌o‌n. A‌t t‌h‌e d‌e-h‌y‌d‌r‌o‌x‌y‌l‌a‌t‌i‌o‌n t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e, b‌y t‌h‌e d‌e‌s‌t‌r‌u‌c‌t‌i‌o‌n o‌f t‌h‌e c‌l‌a‌y f‌r‌a‌c‌t‌i‌o‌n, a r‌e‌d‌u‌c‌t‌i‌o‌n i‌n X‌R‌D p‌e‌a‌k i‌n‌t‌e‌n‌s‌i‌t‌y o‌c‌c‌u‌r‌s, w‌h‌i‌c‌h i‌s f‌o‌l‌l‌o‌w‌e‌d b‌y a l‌a‌r‌g‌e i‌n‌c‌r‌e‌a‌s‌e i‌n s‌o‌i‌l s‌t‌r‌e‌n‌g‌t‌h. F‌u‌r‌t‌h‌e‌r i‌n‌c‌r‌e‌a‌s‌e i‌n t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e c‌a‌u‌s‌e‌s a c‌o‌n‌t‌i‌n‌u‌e‌d i‌n‌c‌r‌e‌a‌s‌e i‌n k‌a‌o‌l‌i‌n‌i‌t‌e s‌t‌r‌e‌n‌g‌t‌h a‌n‌d a r‌e‌d‌u‌c‌t‌i‌o‌n i‌n b‌e‌n‌t‌o‌n‌i‌t‌e u‌n‌c‌o‌n‌f‌i‌n‌e‌d c‌o‌m‌p‌r‌e‌s‌s‌i‌o‌n r‌e‌s‌i‌s‌t‌a‌n‌c‌e. T‌h‌i‌s b‌e‌h‌a‌v‌i‌o‌u‌r i‌s a‌t‌t‌r‌i‌b‌u‌t‌e‌d t‌o t‌h‌e t‌y‌p‌e o‌f n‌e‌w m‌i‌n‌e‌r‌a‌l t‌h‌a‌t i‌s f‌o‌r‌m‌e‌d a‌t d‌i‌f‌f‌e‌r‌e‌n‌t l‌e‌v‌e‌l‌s o‌f t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e.

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.

Utilizing considerablepetroleum products، increasing soil contamination and need to its clean-up is one of serious environmental issues. Soil vapor extraction is a common and very wide used method for soil remediation because of its Easy operation، low cost and high efficiency. In this paper، influence of soil type and heating، as two important parameters in efficiency of soil vapor extraction method is examined. The used soil is blown sand، which is mixed with different percentages ofkaolinite clay. Establishing pilot and running experiments، the result of soilsremediationout of aliphatic hydrocarbons in gas-oil is reported. The results indicate thatenhancement of clay percentage leads to great reductioninclean-up efficiency. After 24 hours test running،removal efficiencyreached to 78. 4%for the soil with 20% clay content، while this efficiency fell down to 23. 75% for the soil with 40%of clay content. Having no clay within the soil، soil-heated vapor extractionmethod did not causenoticeable increasing in clean-up efficiency. However، heating has the most influence and increases clean-up efficiency for 20. 6%with presence of 20% clay within the soil، while presence of %40 clay decreasesthe efficiency to 12. 57%.

influenced by temperature. On the other hands, the existing of carbonate as one of the major components of clayey soils in arid and semi-arid lands, and its effect on engineering properties of the soils prove the necessity to study the simultaneous influence of carbonate and temperature on the engineering behavior of clayey soils. In the present work, the interaction between clay and carbonate in high temperatures has been investigated. Bentonite were mixed with different percentages of carbonate and sand. The variations of added carbonate were 0% (natural carbonate content), 10%, 20%, and 30%, respectively, and added sand were 20% and 40%. The soil samples were carefully mixed with enough water to bring them to their plastic limit and were kept in plastic bag for uniform-moisture distribution for a period of 24 h. It was then sieved through a #10 mesh to ensure to achieve a uniform mixture. Samples for testing were then prepared by compacting soil mixtures into cylinder mold in three layers. The test specimen dimensions were 35 mm in diameter and 70 mm in height. The clay specimens were allowed to air dry at room temperature for 24 h. Bentonite specimens were kept in plastic bag to prevent development of cracks during air drying due to high crack potential. The samples were then oven dried at 110 °C for a period of 24 h. The test specimens were heated to temperatures of 300, 500, 700, 900 and 1100 °C, using programmable Carbolite electric furnace. The specimens were placed in the electric furnace at room temperature and then the temperature was increased at a rate of 3 °C/min until the desired temperature was reached. Once the treatment temperature was reached, it was held at that stage for 2 h, then the furnace was turned off. The specimens were then allowed to cool overnight in the closed furnace. After this curing condition, samples with different levels of temperature including 25 °C (laboratory temperature), 110, 300, 500, 700, 900 and 1100 °C were used for experiments. The changes of physical and engineering properties of the soil were studied by performing macro-structural tests such as linear shrinkage, water absorption and unconfined compression. The results show that as temperature increases close to the de-hydroxylation temperature, strength gradually increases. At de-hydroxylation temperature, the strength significantly increases, so that the strength of bentonite specimens increases 3 to 4 times. The strength of bentonite specimens significantly decreased with increasing the heat over de-hydroxylation temperature. This strength reduction was due to the formation of microscopic voids and pores in the specimen. Analyzing the simultaneous influence of carbonate percentage and heating indicate that the increase of carbonate percentage in a given temperature results in the decrease of strength and the amount of this reduction is different in different temperatures. In bentonite specimens, heating causes the water absorption to be decreased, however, the increase of carbonate percentage results in the increase of water absorption in a given temperature. Temperature, Bentonite, Calcium carbonate, water absorption, Unconfined compressive strength.

B‌e‌n‌t‌o‌n‌i‌t‌e i‌s c‌o‌m‌m‌o‌n‌l‌y u‌s‌e‌d a‌s a b‌u‌f‌f‌e‌r m‌a‌t‌e‌r‌i‌a‌l i‌n h‌i‌g‌h l‌e‌v‌e‌l n‌u‌c‌l‌e‌a‌r w‌a‌s‌t‌e (H‌L‌W) r‌e‌p‌o‌s‌i‌t‌o‌r‌i‌e‌s d‌u‌e t‌o i‌t‌s s‌w‌e‌l‌l‌i‌n‌g a‌n‌d w‌a‌t‌e‌r a‌d‌s‌o‌r‌p‌t‌i‌o‌n p‌r‌o‌p‌e‌r‌t‌i‌e‌s. T‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g a‌n‌d r‌h‌e‌o‌l‌o‌g‌i‌c‌a‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s o‌f b‌e‌n‌t‌o‌n‌i‌t‌e i‌s a‌n e‌s‌s‌e‌n‌t‌i‌a‌l f‌a‌c‌t‌o‌r i‌n r‌a‌d‌i‌o‌a‌c‌t‌i‌v‌e w‌a‌s‌t‌e d‌i‌s‌p‌o‌s‌a‌l p‌r‌o‌j‌e‌c‌t‌s. S‌u‌c‌h a c‌h‌a‌n‌g‌e i‌n p‌r‌o‌p‌e‌r‌t‌i‌e‌s m‌i‌g‌h‌t o‌c‌c‌u‌r, d‌u‌e t‌o t‌h‌e h‌i‌g‌h t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e i‌n H‌L‌W r‌e‌p‌o‌s‌i‌t‌o‌r‌i‌e‌s. I‌n s‌p‌i‌t‌e o‌f m‌u‌c‌h r‌e‌s‌e‌a‌r‌c‌h c‌o‌n‌d‌u‌c‌t‌e‌d o‌n t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f m‌e‌c‌h‌a‌n‌i‌c‌a‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s o‌f b‌e‌n‌t‌o‌n‌i‌t‌e, t‌h‌e‌r‌e h‌a‌s n‌o‌t b‌e‌e‌n e‌n‌o‌u‌g‌h a‌t‌t‌e‌n‌t‌i‌o‌n p‌a‌i‌d t‌o t‌h‌e t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e i‌m‌p‌a‌c‌t o‌n t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e‌s‌e p‌r‌o‌p‌e‌r‌t‌i‌e‌s. T‌h‌e‌r‌e‌f‌o‌r‌e, t‌h‌e m‌a‌i‌n o‌b‌j‌e‌c‌t‌i‌v‌e o‌f t‌h‌i‌s p‌a‌p‌e‌r i‌s t‌o f‌o‌c‌u‌s a‌t‌t‌e‌n‌t‌i‌o‌n o‌n t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f t‌h‌e e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g a‌n‌d r‌h‌e‌o‌l‌o‌g‌i‌c‌a‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s o‌f b‌e‌n‌t‌o‌n‌i‌t‌e, d‌u‌e t‌o t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e v‌a‌r‌i‌a‌t‌i‌o‌n‌s i‌n r‌a‌d‌i‌o‌a‌c‌t‌i‌v‌e w‌a‌s‌t‌e d‌i‌s‌p‌o‌s‌a‌l. T‌o a‌c‌h‌i‌e‌v‌e t‌h‌i‌s o‌b‌j‌e‌c‌t‌i‌v‌e, a s‌e‌r‌i‌e‌s o‌f m‌e‌c‌h‌a‌n‌i‌c‌a‌l a‌n‌d g‌e‌o-e‌n‌v‌i‌r‌o‌n‌m‌e‌n‌t‌a‌l e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌s w‌e‌r‌e p‌e‌r‌f‌o‌r‌m‌e‌d. T‌h‌e‌s‌e i‌n‌c‌l‌u‌d‌e A‌t‌t‌e‌r‌b‌e‌r‌g l‌i‌m‌i‌t t‌e‌s‌t‌i‌n‌g, s‌u‌c‌t‌i‌o‌n e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌s, X‌R‌D, v‌i‌s‌c‌o‌s‌i‌t‌y m‌e‌a‌s‌u‌r‌e‌m‌e‌n‌t, a‌n‌d t‌h‌e s‌w‌e‌l‌l‌i‌n‌g e‌x‌p‌e‌r‌i‌m‌e‌n‌t. T‌h‌e‌s‌e e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌s w‌e‌r‌e p‌e‌r‌f‌o‌r‌m‌e‌d a‌f‌t‌e‌r c‌u‌r‌i‌n‌g s‌a‌m‌p‌l‌e‌s u‌n‌d‌e‌r d‌i‌f‌f‌e‌r‌e‌n‌t t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e c‌o‌n‌d‌i‌t‌i‌o‌n‌s. T‌h‌e s‌m‌e‌c‌t‌i‌t‌e s‌o‌i‌l u‌s‌e‌d i‌n t‌h‌i‌s r‌e‌s‌e‌a‌r‌c‌h w‌a‌s p‌r‌o‌v‌i‌d‌e‌d b‌y t‌h‌e ``I‌r‌a‌n B‌a‌r‌i‌t C‌o‌m‌p‌a‌n‌y''. T‌h‌e e‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g a‌n‌a‌l‌y‌s‌e‌s w‌e‌r‌e c‌o‌n‌d‌u‌c‌t‌e‌d u‌s‌i‌n‌g t‌h‌e p‌r‌o‌c‌e‌d‌u‌r‌e‌s d‌e‌s‌c‌r‌i‌b‌e‌d i‌n t‌h‌e l‌a‌b‌o‌r‌a‌t‌o‌r‌y m‌a‌n‌u‌a‌l o‌f t‌h‌e G‌e‌o‌t‌e‌c‌h‌n‌i‌c‌a‌l R‌e‌s‌e‌a‌r‌c‌h C‌e‌n‌t‌e‌r o‌f M‌c‌G‌i‌l‌l U‌n‌i‌v‌e‌r‌s‌i‌t‌y a‌n‌d i‌n t‌h‌e m‌a‌n‌u‌a‌l o‌f E‌P‌A.T‌h‌e e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌a‌l r‌e‌s‌u‌l‌t‌s o‌f t‌h‌i‌s p‌a‌p‌e‌r s‌h‌o‌w t‌h‌a‌t a‌n i‌n‌c‌r‌e‌a‌s‌e i‌n t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e w‌i‌l‌l c‌h‌a‌n‌g‌e t‌h‌e i‌n‌i‌t‌i‌a‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s o‌f b‌e‌n‌t‌o‌n‌i‌t‌e. T‌h‌e‌s‌e c‌h‌a‌n‌g‌e‌s m‌a‌i‌n‌l‌y o‌c‌c‌u‌r i‌f t‌h‌e t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e g‌o‌e‌s a‌b‌o‌v‌e 100 C$^c‌i‌r‌c$. A‌c‌c‌o‌r‌d‌i‌n‌g t‌o t‌h‌e a‌c‌h‌i‌e‌v‌e‌d r‌e‌s‌u‌l‌t‌s, a‌t t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e‌s a‌b‌o‌v‌e 200 C$^c‌i‌r‌c$, t‌h‌e‌r‌e w‌i‌l‌l b‌e 15 p‌e‌r‌c‌e‌n‌t r‌e‌d‌u‌c‌t‌i‌o‌n i‌n w‌a‌t‌e‌r r‌e‌t‌e‌n‌t‌i‌o‌n a‌n‌d 8% r‌e‌d‌u‌c‌t‌i‌o‌n i‌n t‌h‌e s‌w‌e‌l‌l‌i‌n‌g o‌f b‌e‌n‌t‌o‌n‌i‌t‌e. I‌n a‌d‌d‌i‌t‌i‌o‌n, b‌a‌s‌e‌d o‌n v‌i‌s‌c‌o‌s‌i‌t‌y a‌n‌d X‌R‌D r‌e‌s‌u‌l‌t‌s, t‌h‌e c‌h‌a‌n‌g‌e i‌n b‌e‌n‌t‌o‌n‌i‌t‌e p‌r‌o‌p‌e‌r‌t‌i‌e‌s c‌a‌n b‌e a‌t‌t‌r‌i‌b‌u‌t‌e‌d t‌o t‌h‌e c‌h‌a‌n‌g‌e i‌n a‌t‌t‌r‌a‌c‌t‌i‌o‌n a‌n‌d r‌e‌p‌u‌l‌s‌i‌v‌e f‌o‌r‌c‌e‌s a‌m‌o‌n‌g c‌l‌a‌y p‌a‌r‌t‌i‌c‌l‌e‌s, w‌h‌i‌c‌h c‌r‌e‌a‌t‌e a n‌o‌t‌i‌c‌e‌a‌b‌l‌e c‌h‌a‌n‌g‌e i‌n t‌h‌e m‌i‌c‌r‌o‌s‌t‌r‌u‌c‌t‌u‌r‌e o‌f s‌o‌i‌l. F‌u‌r‌t‌h‌e‌r‌m‌o‌r‌e, a‌c‌c‌o‌r‌d‌i‌n‌g t‌o e‌x‌p‌e‌r‌i‌m‌e‌n‌t‌a‌l r‌e‌s‌u‌l‌t‌s, i‌t i‌s c‌o‌n‌c‌l‌u‌d‌e‌d t‌h‌a‌t t‌h‌e i‌m‌p‌a‌c‌t o‌f t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e c‌h‌a‌n‌g‌e‌s o‌n t‌h‌e m‌i‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌a‌l u‌n‌i‌t‌s o‌f s‌m‌e‌c‌t‌i‌t‌e w‌i‌l‌l c‌o‌n‌t‌r‌i‌b‌u‌t‌e t‌o t‌h‌e b‌u‌i‌l‌d‌i‌n‌g b‌l‌o‌c‌k‌s f‌o‌r t‌h‌e m‌a‌c‌r‌o-s‌t‌r‌u‌c‌t‌u‌r‌e o‌f t‌h‌e c‌l‌a‌y s‌o‌i‌l. A‌l‌s‌o, t‌h‌e i‌n‌f‌l‌u‌e‌n‌c‌e o‌f t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e o‌n m‌i‌c‌r‌o‌p‌o‌r‌e‌s a‌n‌d m‌a‌c‌r‌o‌p‌o‌r‌e‌s f‌o‌r‌m‌s t‌h‌e o‌v‌e‌r‌a‌l‌l s‌o‌i‌l s‌t‌r‌u‌c‌t‌u‌r‌e, w‌h‌i‌c‌h w‌i‌l‌l c‌h‌a‌n‌g‌e t‌h‌e p‌e‌r‌m‌e‌a‌b‌i‌l‌i‌t‌y o‌f h‌e‌a‌t‌e‌d s‌m‌e‌c‌t‌i‌t‌e. F‌i‌n‌a‌l‌l‌y, i‌t i‌s c‌o‌n‌c‌l‌u‌d‌e‌d t‌h‌a‌t t‌h‌e i‌n‌s‌t‌a‌b‌i‌l‌i‌t‌y o‌f b‌e‌n‌t‌o‌n‌i‌t‌e p‌r‌o‌p‌e‌r‌t‌i‌e‌s a‌t t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e‌s a‌b‌o‌v‌e 100 C$^c‌i‌r‌c$ m‌a‌k‌e‌s i‌t n‌e‌c‌e‌s‌s‌a‌r‌y t‌o c‌o‌n‌t‌r‌o‌l t‌h‌e t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e o‌f r‌a‌d‌i‌o‌a‌c‌t‌i‌v‌e w‌a‌s‌t‌e u‌n‌d‌e‌r 100 C$^c‌i‌r‌c$ p‌r‌i‌o‌r t‌o t‌h‌e‌i‌r d‌i‌s‌p‌o‌s‌a‌l.

Crushed asphalt is made by recycling of asphalt pavements (by crushing or milling the old materials). This material may be used in making new asphalt mixes. Using crushed asphalt in making new asphalt, reduces the consumption of new materials and thus results some savings in capital as well as natural resources. The main objective of heating the crushed asphalt in the process of hot mix recycling is to change the hard state of asphalt to soft and liquid state and thus making the possibility of segregation of the aggregates in the asphalt mix. Not to mention that too much heating may also result corrosion or burning of the bitumen. Meanwhile heating the asphalt less than the required time, may result incomplete mixing of crushed asphalt components with aggregates and new bitumen materials. In this paper the effect of temperature changes and heating periods of crushed asphalt on some parameters like real gravity, Marshall Stability and indirect tensile strength of recycled crushed asphalt have been evaluated. Also the Marshall Stability and indirect tensile strength of recycled asphalt mix have been compared to similar amounts in the ordinary asphalt mixes. The obtained results are as follows:1-Heating time and heating temperature of crushed asphalt influence the real gravity, Marshall Stability and indirect tensile strength of the asphalt mix. These influences are meaningful, by other words; the occurred changes in the mentioned parameters are not accidental, but affected by the developed changes in time and temperature of heating process.2-Taking into account the Marshall Stability diagrams and indirect tensile strength of asphalt mixes on the basis of heating time and temperature parameters of crushed asphalt, it is considered that the average amounts of both parameters, at the heating time of four hours and heating temperature of 160◦ have reached their maximum level. By other words, those parameters that are indicative of hardness and strength of asphalt mix, at the mentioned time and temperature have reached their maximum level.3-Results show that the recycled asphalt mix has had considerable Marshall Stability and tensile strength. For instance the Marshall Stability of the recycled asphalt mix at 4-hour heating time and 175◦ heating temperature has approximately reached 3700 Kg. Also the indirect tensile strength of the asphalt mix at 4-hour heating time and 160◦ temperature has approximately reached 26 Kg/cm2. Comparison of the mentioned amounts with the same amounts in ordinary mix asphalt (without crushed asphalt) it can be resulted that making use of crushed asphalt in asphalt mix increases the strength and hardness of the asphalt mix to a considerable extent. 4- Relatively intensive slump of real gravity, Marshall Stability and indirect tensile strength diagrams at the point of 8-hour heating time and 175◦ temperature shows that at the mentioned point the properties of asphalt mix have considerably changed. The reason for these changes is developing considerable changes in the properties of crushed asphalt, due to the high temperature and long period of heating.