Background The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent genera... more Background The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during reprocessing by co-precipitating uranium, plutonium and other actinides, as well as some other radioactive species, with iron as iron hydroxide flocs. In the UK, these flocs are classed as Intermediate Level Waste (ILW), with the preferred method of disposal being encapsulation in cementitious systems [1]. A composite cement based on the partial replacement of ordinary Portland cement (OPC) with pulverised fuel ash (PFA) is used. This provides advantages over using neat OPC including reduced permeability and lower heat of hydration [2-4]. Despite extensive use in the water processing industry, there is little literature on encapsulating iron hydroxide compounds in cementitious systems. It has however, been reported that ferric hydroxides retard the setting of cement [5].
The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during ... more The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during reprocessing by co-precipitating uranium, plutonium and other actinides, as well as some other radioactive species, with iron to form an iron hydroxide floc. Four different flocs with different chemical compositions are produced depending on the source of the feed material. In the UK, these flocs are classed as Intermediate Level Waste (ILW), with the preferred method of disposal being encapsulation in cementitious systems [1]. A composite cement based on the partial replacement of ordinary Portland cement (OPC) with pulverised fuel ash (PFA) is used. This provides advantages over using neat OPC including reduced permeability and lower heat of hydration [2-4]. Iron hydroxide flocs are used extensively in the water processing industry, but there appears to be little information in the literature on the subject of encapsulating iron hydroxide compounds in cementitious systems. It has howev...
This investigation attempts to determine the extent of errors, induced by various forms of acid a... more This investigation attempts to determine the extent of errors, induced by various forms of acid and neutral extraction of the cement content of the hardened concrete, upon the alkali content contributed by the cement. Four common New Zealand volcanic rocks (Basalt, Andesite, and Dacite) and a Greywacke were chosen to represent the types of aggregates likely to be present in concretes undergoing the alkali aggregate reaction. The following concrete extraction methods were tested: a) dilute nitric acid; b) hot water; and c) picric acid. Total alkali levels, and sodium and potassium levels were measured, as were the concentrations of trace alkalis such as lithium, rubidium and caesium. The results showed that: a) acid extraction methods cannot be used to determine cement alkalis of basalt aggregate because the large amount of alkalis contributed by the basalt cause unacceptable errors; b) the dilute nitric acid extraction method can be used for andesite, dacite and rhyolite aggregates;...
Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment ... more Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment to synthesize high performance cementitious construction materials with low environmental impact. The nature of the starting materials including mineral composition, chemical composition and crystal structure groups affects the formation of the geopolymer gel phase. In this paper, the pozzolanic activities of five natural pozzolans are studied.
Natural pozzolans are raw materials from geological deposits with a range of chemical composition... more Natural pozzolans are raw materials from geological deposits with a range of chemical compositions that when combined with suitable alkali activators can be converted to geopolymer cement for concrete production. In this paper the concept of adding mineral additives to enhance the properties of geopolymer cement is introduced. Taftan andesite, a natural Iranian pozzolan, was used to study the effect of adding mineral additives such as kaolinite, lime and other calcined pozzolans on the compressive strength of geopolymer cement under both normal and autoclave curing. Scanning electron microscopy (SEM) / energy dispersive X-ray (EDX) was used to determine the composition of the gel phase in both alkali-activated Taftan pozzolan with and without mineral additions. The work has shown that deficiencies in SiO2, Al2O3 and CaO content in the raw natural pozzolan can be compensated for by adding mineral additives for enhanced properties.
The current study has investigated the interactions between well cements and one of the most comm... more The current study has investigated the interactions between well cements and one of the most common types of rocks found in geothermal environments, under hydrothermal conditions. Holes were drilled in blocks of ignimbrite rock and API class G cement with 0, 20 and 40% added silica flour, was poured into the cavities. The whole assemblage was autoclaved, under typical geothermal conditions at 150° and 300°C for 28 days. The results show that chemical reactions occur in the intertransition zone, which are dependent on both drilling fluid and temperature. The use of bentonite as a drilling fluid and the exposure to higher temperatures (300°C) when compared to 150°C, seem to exacerbate the reactions occurring in the ITZ. Consequently, there is formation of new crystalline products, which have worse performance when the physical bonding between the cement and the rock is considered. The effect of other variables such as CO2 exposure, the hydrothermal alteration of the rock and the curin...
Composite cement blends based on the replacement of ordinary Portland cement (OPC) with blast fur... more Composite cement blends based on the replacement of ordinary Portland cement (OPC) with blast furnace slag (BFS) are currently used as a matrix for the encapsulation of both solid and liquid intermediate level radioactive wastes (ILW) in the UK. Cements are used because they are
Studies of carbonation of geotheirmal grouts have shown that the physical criteria recommended by... more Studies of carbonation of geotheirmal grouts have shown that the physical criteria recommended by the American Petroleum Institute do not apply for durability in CO/sub 2/-containing fluids. The high silica binders, normally considered desirable because of their high strengths and low permeability, become permeable when carbonated. This allows further attack on the grout, and if the fluids are undersaturated with CaCO/sub 3/, then rapid corrosion will occur. On the other hand, grouts which contain appreciable amounts of calcium hydroxide have proved the most durable in CO/sub 2/-containing fluids despite their low strengths and high permeability. This is due to an impermeable layer of calcium carbonate which forms on the outside of the sample preventing further penetration of reactant species. Unless this layer is corroded, no further attack occurs.
Abstract The limited durability of the cement in acidic fluids is one of the main issues controll... more Abstract The limited durability of the cement in acidic fluids is one of the main issues controlling the lifetime of a geothermal well. The most critical region is the outermost layer of the cement adjacent to the formation. This paper provides insight into the way in which well cementing formulations interact with a common rock formation in geothermal environments, at 150 °C in brine, with and without CO2 exposure. The results show that chemical reactions occur in the ITZ, which are driven by Ca2+ and OH− migration from the cement into the rock, which are dependent on the type and amount of silica added to the cement. The presence of CO2 influences the extent of cement/rock interaction which is dependent on the cement formulation. The current work indicates that the carbonation in these systems is a very complex set of reactions, where poorly crystalline and amorphous calcium carbonates may form.
The lifetime of a geothermal well is strongly dependent on the long-term performance of the cemen... more The lifetime of a geothermal well is strongly dependent on the long-term performance of the cement used for its construction. The critical zones in well cements are the outermost layers, where the ...
The reduced lifetime of geothermal wells is one of the main issues facing the geothermal industry... more The reduced lifetime of geothermal wells is one of the main issues facing the geothermal industry, with cement durability being one of the main causes for shortening of a well's life. While most wells are cemented with American Petroleum Institute (API) class cements, alternative cementing systems are currently being considered. In this paper, the interactions of two alternative cement formulations with a typical geothermal rock formation are compared with a class A cement. This allows understanding of the most critical zone in the geothermal cement, which is the outermost layer where the cement encounters and, consequently, interacts with the exterior harsh environment, including the volcanic formation and brine. The faster setting of white cement and high-alumina cement compared with the well Portland cement seems to reduce the reaction extent with the rock. For all the cements tested, both the increased curing temperature (from 150°C to 290°C) and the use of bentonite as dril...
The discovery of a micrcporous oxide system based not on silicates but on aluminophosphates has p... more The discovery of a micrcporous oxide system based not on silicates but on aluminophosphates has proved very exciting and promises great potential for tailoring catalysts. These new materials are formed by hydrothermal treatment of a reactive aluminophosphate gel, in the presence of an organic base which acts as a structure directing species. Using several templating agents 31 different micrcporous structures have been currently reported. Many of these have analogues in zeolite chemistry but several are less thermally stable structures and are unusual in having 5-ccordinate aluminium. A wide range of elements can be substituted into the framework for either Al or P. These include transition metals such as Co, Zn, Mn or Fe which substitute for Al, and elements such as Si, Ge or Ti which seem to substitute for P. Both these types of substitution produce Bronsted acid sites so that these materials can be used as catalysts in a similar way to zeolites. Methods of characterising and quant...
Etude experimentale de la conversion de methanol en hydrocarbures sur une serie de zeolites ZSM-5... more Etude experimentale de la conversion de methanol en hydrocarbures sur une serie de zeolites ZSM-5 avec des teneurs en alumine allant de 0 a 5,9%. Determination des teneurs en hydrocarbures aromatiques C 7 -C 10 dans les hydrocarbures produits
This report was pnparcd as an account of work sponsored by an agency of the United States Governm... more This report was pnparcd as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or mponsibility for the accuracy, completeness. or usefulness of any information, apparatus, product, or pmcess disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spccific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise docs not n d y constitute or imply its endorsement. mommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
A-The first and second iouizetion ooustaats for hydrogen m&hide in aqueaua solution have been det... more A-The first and second iouizetion ooustaats for hydrogen m&hide in aqueaua solution have been determiued from 20 to 90°C by 8 spectrophotometria method. The velue of p&,8 decreases from 7.06 at 26°C to 0.5 at 90°C while pKas-decreases from 13.8 to 12.1 iu thie temperature interval.
Background The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent genera... more Background The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during reprocessing by co-precipitating uranium, plutonium and other actinides, as well as some other radioactive species, with iron as iron hydroxide flocs. In the UK, these flocs are classed as Intermediate Level Waste (ILW), with the preferred method of disposal being encapsulation in cementitious systems [1]. A composite cement based on the partial replacement of ordinary Portland cement (OPC) with pulverised fuel ash (PFA) is used. This provides advantages over using neat OPC including reduced permeability and lower heat of hydration [2-4]. Despite extensive use in the water processing industry, there is little literature on encapsulating iron hydroxide compounds in cementitious systems. It has however, been reported that ferric hydroxides retard the setting of cement [5].
The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during ... more The Enhanced Actinide Removal Plant (EARP) at Sellafield treats liquid effluent generated during reprocessing by co-precipitating uranium, plutonium and other actinides, as well as some other radioactive species, with iron to form an iron hydroxide floc. Four different flocs with different chemical compositions are produced depending on the source of the feed material. In the UK, these flocs are classed as Intermediate Level Waste (ILW), with the preferred method of disposal being encapsulation in cementitious systems [1]. A composite cement based on the partial replacement of ordinary Portland cement (OPC) with pulverised fuel ash (PFA) is used. This provides advantages over using neat OPC including reduced permeability and lower heat of hydration [2-4]. Iron hydroxide flocs are used extensively in the water processing industry, but there appears to be little information in the literature on the subject of encapsulating iron hydroxide compounds in cementitious systems. It has howev...
This investigation attempts to determine the extent of errors, induced by various forms of acid a... more This investigation attempts to determine the extent of errors, induced by various forms of acid and neutral extraction of the cement content of the hardened concrete, upon the alkali content contributed by the cement. Four common New Zealand volcanic rocks (Basalt, Andesite, and Dacite) and a Greywacke were chosen to represent the types of aggregates likely to be present in concretes undergoing the alkali aggregate reaction. The following concrete extraction methods were tested: a) dilute nitric acid; b) hot water; and c) picric acid. Total alkali levels, and sodium and potassium levels were measured, as were the concentrations of trace alkalis such as lithium, rubidium and caesium. The results showed that: a) acid extraction methods cannot be used to determine cement alkalis of basalt aggregate because the large amount of alkalis contributed by the basalt cause unacceptable errors; b) the dilute nitric acid extraction method can be used for andesite, dacite and rhyolite aggregates;...
Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment ... more Natural pozzolans can be activated and condensed with sodium silicate in an alkaline environment to synthesize high performance cementitious construction materials with low environmental impact. The nature of the starting materials including mineral composition, chemical composition and crystal structure groups affects the formation of the geopolymer gel phase. In this paper, the pozzolanic activities of five natural pozzolans are studied.
Natural pozzolans are raw materials from geological deposits with a range of chemical composition... more Natural pozzolans are raw materials from geological deposits with a range of chemical compositions that when combined with suitable alkali activators can be converted to geopolymer cement for concrete production. In this paper the concept of adding mineral additives to enhance the properties of geopolymer cement is introduced. Taftan andesite, a natural Iranian pozzolan, was used to study the effect of adding mineral additives such as kaolinite, lime and other calcined pozzolans on the compressive strength of geopolymer cement under both normal and autoclave curing. Scanning electron microscopy (SEM) / energy dispersive X-ray (EDX) was used to determine the composition of the gel phase in both alkali-activated Taftan pozzolan with and without mineral additions. The work has shown that deficiencies in SiO2, Al2O3 and CaO content in the raw natural pozzolan can be compensated for by adding mineral additives for enhanced properties.
The current study has investigated the interactions between well cements and one of the most comm... more The current study has investigated the interactions between well cements and one of the most common types of rocks found in geothermal environments, under hydrothermal conditions. Holes were drilled in blocks of ignimbrite rock and API class G cement with 0, 20 and 40% added silica flour, was poured into the cavities. The whole assemblage was autoclaved, under typical geothermal conditions at 150° and 300°C for 28 days. The results show that chemical reactions occur in the intertransition zone, which are dependent on both drilling fluid and temperature. The use of bentonite as a drilling fluid and the exposure to higher temperatures (300°C) when compared to 150°C, seem to exacerbate the reactions occurring in the ITZ. Consequently, there is formation of new crystalline products, which have worse performance when the physical bonding between the cement and the rock is considered. The effect of other variables such as CO2 exposure, the hydrothermal alteration of the rock and the curin...
Composite cement blends based on the replacement of ordinary Portland cement (OPC) with blast fur... more Composite cement blends based on the replacement of ordinary Portland cement (OPC) with blast furnace slag (BFS) are currently used as a matrix for the encapsulation of both solid and liquid intermediate level radioactive wastes (ILW) in the UK. Cements are used because they are
Studies of carbonation of geotheirmal grouts have shown that the physical criteria recommended by... more Studies of carbonation of geotheirmal grouts have shown that the physical criteria recommended by the American Petroleum Institute do not apply for durability in CO/sub 2/-containing fluids. The high silica binders, normally considered desirable because of their high strengths and low permeability, become permeable when carbonated. This allows further attack on the grout, and if the fluids are undersaturated with CaCO/sub 3/, then rapid corrosion will occur. On the other hand, grouts which contain appreciable amounts of calcium hydroxide have proved the most durable in CO/sub 2/-containing fluids despite their low strengths and high permeability. This is due to an impermeable layer of calcium carbonate which forms on the outside of the sample preventing further penetration of reactant species. Unless this layer is corroded, no further attack occurs.
Abstract The limited durability of the cement in acidic fluids is one of the main issues controll... more Abstract The limited durability of the cement in acidic fluids is one of the main issues controlling the lifetime of a geothermal well. The most critical region is the outermost layer of the cement adjacent to the formation. This paper provides insight into the way in which well cementing formulations interact with a common rock formation in geothermal environments, at 150 °C in brine, with and without CO2 exposure. The results show that chemical reactions occur in the ITZ, which are driven by Ca2+ and OH− migration from the cement into the rock, which are dependent on the type and amount of silica added to the cement. The presence of CO2 influences the extent of cement/rock interaction which is dependent on the cement formulation. The current work indicates that the carbonation in these systems is a very complex set of reactions, where poorly crystalline and amorphous calcium carbonates may form.
The lifetime of a geothermal well is strongly dependent on the long-term performance of the cemen... more The lifetime of a geothermal well is strongly dependent on the long-term performance of the cement used for its construction. The critical zones in well cements are the outermost layers, where the ...
The reduced lifetime of geothermal wells is one of the main issues facing the geothermal industry... more The reduced lifetime of geothermal wells is one of the main issues facing the geothermal industry, with cement durability being one of the main causes for shortening of a well's life. While most wells are cemented with American Petroleum Institute (API) class cements, alternative cementing systems are currently being considered. In this paper, the interactions of two alternative cement formulations with a typical geothermal rock formation are compared with a class A cement. This allows understanding of the most critical zone in the geothermal cement, which is the outermost layer where the cement encounters and, consequently, interacts with the exterior harsh environment, including the volcanic formation and brine. The faster setting of white cement and high-alumina cement compared with the well Portland cement seems to reduce the reaction extent with the rock. For all the cements tested, both the increased curing temperature (from 150°C to 290°C) and the use of bentonite as dril...
The discovery of a micrcporous oxide system based not on silicates but on aluminophosphates has p... more The discovery of a micrcporous oxide system based not on silicates but on aluminophosphates has proved very exciting and promises great potential for tailoring catalysts. These new materials are formed by hydrothermal treatment of a reactive aluminophosphate gel, in the presence of an organic base which acts as a structure directing species. Using several templating agents 31 different micrcporous structures have been currently reported. Many of these have analogues in zeolite chemistry but several are less thermally stable structures and are unusual in having 5-ccordinate aluminium. A wide range of elements can be substituted into the framework for either Al or P. These include transition metals such as Co, Zn, Mn or Fe which substitute for Al, and elements such as Si, Ge or Ti which seem to substitute for P. Both these types of substitution produce Bronsted acid sites so that these materials can be used as catalysts in a similar way to zeolites. Methods of characterising and quant...
Etude experimentale de la conversion de methanol en hydrocarbures sur une serie de zeolites ZSM-5... more Etude experimentale de la conversion de methanol en hydrocarbures sur une serie de zeolites ZSM-5 avec des teneurs en alumine allant de 0 a 5,9%. Determination des teneurs en hydrocarbures aromatiques C 7 -C 10 dans les hydrocarbures produits
This report was pnparcd as an account of work sponsored by an agency of the United States Governm... more This report was pnparcd as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or mponsibility for the accuracy, completeness. or usefulness of any information, apparatus, product, or pmcess disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spccific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise docs not n d y constitute or imply its endorsement. mommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
A-The first and second iouizetion ooustaats for hydrogen m&hide in aqueaua solution have been det... more A-The first and second iouizetion ooustaats for hydrogen m&hide in aqueaua solution have been determiued from 20 to 90°C by 8 spectrophotometria method. The velue of p&,8 decreases from 7.06 at 26°C to 0.5 at 90°C while pKas-decreases from 13.8 to 12.1 iu thie temperature interval.
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