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1.
石灰土作为路基填料代替宕渣是一种较为经济的方案,但灰土初始强度低、硬化速率慢、碳化时间长,不利于快速施工,需要进行改良研究。利用偏高岭土与石灰发生火山灰反应的原理改良灰土,通过单轴压缩试验和三轴压缩试验,分析改良灰土冻融循环条件下力学参数变化规律,利用图像处理技术提取改良灰土图像表面孔隙,建立孔隙率与强度的关系,并通过研究龄期、石灰含量和含水率变化规律,分析偏高岭土改良灰土的机制。结果表明：偏高岭土能够有效提高灰土材料反应速率,改善灰土力学特性;偏高岭土在一定程度上能够恢复冻融循环导致的灰土力学性能损失,降低冰晶体产生的孔隙;灰土强度达到最优后,其强度随着石灰的增加而降低,而经偏高岭土改良后其强度将继续增加;火山灰反应比灰土碳化过程消耗更多的水分,有效提高了灰土的抗冻性能。  相似文献   

2.
A common decay scenario in old and new buildings was simulated: the effects on masonry structures of salt efflorescence or subefflorescence produced by the rise of saline solution. Eight different types of masonry wall each made up of a combination of different construction materials (brick, calcarenite and four types of mortar were combined as follows: pure lime mortar, mortar + air entraining agent, mortar + pozzolana, mortar + air entraining agent + pozzolana) have been tested. These materials have different textures (strong anisotropy in brick, irregular-shaped pores in calcarenite, retraction fissures or rounded pores in mortars which also show a reduction of porosity along the contact area with the stone), different hydric behaviours (under total immersion brick + mortar specimens absorb water faster than calcarenite + mortar specimens) and different pore size distribution (brick shows unimodal pore distribution, whereas calcarenite and mortars are bimodal). In the salt weathering test, mortars interlayered with masonry blocks did not act as sacrificial layers. In fact, they allowed salts to rise through them and crystallize on the brick or calcarenite pieces causing the masonry structure to decay. Only the addition of an air-entraining agent partially hindered the capillary rise of the salt-laden solutions.  相似文献   

3.
This paper presents new petro-chemical data on some typical mortars found in many buildings in the historic city centre of Catania (Eastern Sicily). Extensively used in the architecture of the city from the second half of the nineteenth century until the mid-twentieth century, these mortars are characterised by a particular aggregate locally known as “agghiara” or “ghiara”. This is the product of thermal transformation induced by the heating undergone by palaeo-soils, originally rich in organic matter, covered by lava flows, which change their colour to reddish nuances. The volcanic origin of ghiara is a peculiar feature of the Etnean area. Mixed with lime, it gives to mortars an intense reddish colour, as well as hydraulic properties, which are comparable with those of the historically used pozzolana. This work aimed at complete characterisation of these ghiara mortars, for providing information on several important technological aspects. In order to get information on used raw materials, sampling of some ancient underground quarries, located both in the historic city centre and at the periphery, was also performed. Results led to the complete characterisation of the selected ghiara mortars and yielded information on some technological features and the composition of both newly formed and secondary phases, these latter due to alteration processes. The hydraulic properties of mortars have been related to the occurrence of amorphous phases within the ghiara aggregate, which were identified by means of SEM morphological observations. These phases, formed during the “firing” process of palaeo-soils, react with lime producing hydraulic compounds (C–S–H and C–A–H), which are responsible for the mortars durability.  相似文献   

4.
The sulfation of four types of calcitic and dolomitic lime mortars exposed to SO2 in the presence of particulate matter from diesel vehicle exhaust emissions has been investigated. The binders mineralogy and mortars texture are the main factors influencing the formation of deleterious sulfate salts. The type of binder also influences the pore size distribution and the total porosity of the mortars: for equal aggregate (quartz or dolomite), dolomitic lime mortars have smaller pores and higher porosity than calcitic ones. During the first 24 h exposure to SO2, calcitic lime mortars undergo a higher weight increase than dolomitic ones due to rapid formation of gypsum on their surface. However, at the end of the sulfation test (10 days), dolomitic mortars show a higher weight increase due to massive formation of epsomite and gypsum, which is facilitated by their higher porosity and the high reactivity of Mg phases in the porous and partially carbonated binder. Control samples (not covered with diesel particulate matter) also develop calcium and magnesium sulfates upon long term exposure to SO2. This is due to the presence of uncarbonated Ca and Mg hydroxides that promote SO2 fixation as sulfates. However, the amount and size of sulfate crystals are significantly smaller than those observed on samples covered with diesel particulate matter. These results show that diesel particulate matter enhances the sulfation of lime mortars and demonstrate that sulfation of dolomitic lime is an important mechanism for the in situ formation of highly soluble and deleterious hydrated magnesium sulfates (epsomite and hexahydrite). The use of dolomitic limes in the conservation of monuments exposed to air pollution in urban environments may therefore pose a significant risk.  相似文献   

5.
Summary About 90 samples of mortars from historical buildings in Pisa have been analysed and compared with some samples of ancient mortars characterized by pozzolanic aggregates. Chemical (XRF), mineralogical (XRD) and petrographical (optical microscopy) data have been collected on bulk samples. An X-ray energy-dispersive system (EDS) attached to a SEM was used to determine the chemical compositions of binder, clots and pozzolanic grains (whenever present). The binder components which could not be directly assessed (CO2, H2O+) have been indirectly derived through a computation method.Data collected suggest that the main stock of analysed samples (i.e., mortars from Pisa monuments) contains two principal types of binder: the first type corresponds to a common carbonated lime; the second type is a hydraulic lime, where the carbonate component is associated with an important silicate fraction, which constitutes 13 to 89 wt% of the total binder (on average 47%). This hydraulic type had a widespread application in the construction of ancient monuments in Pisa; for example, it was constantly employed in the building of the famous Leaning Tower. This study shows that the silicate fraction of such hydraulic mortar, which is amorphous to X-ray diffraction, is made up by a hydrated calcium alumino-silicate having a very low Al2O3/SiO2 ratio (on average 0.125). On the basis of chemical and optical characteristics of hydraulic mortar binders from Pisa and the results of laboratory tests, as well as through comparison with the characteristics of ancient hydraulic mortars having pozzolanic aggregates, it is concluded that such mortars were prepared most likely by mixing slaked lime with a reactive, highly siliceous material such as a diatomaceous earth.
Über Bindemittel in antiken Mörteln
Zusammenfassung Etwa 90 Mörtelproben von historischen Gebäuden in Pisa wurden analysiert und mit Proben von antiken Mörteln, die durch pozzolanische Aggregate charakterisert sind, verglichen. Chemische (XRF), mineralogische (XRD) und petrographische (optische Mikroskopie) Daten wurden an den Gesamtproben ermittelt. Ein an ein SEM angeschlossenes energiedispersives System (EDS) wurde für die Bestimmung der chemischen Zusammensetzung des Bindemittels, der Mörtelklümpchen und der pozzolanischen Körner (sofern vorhanden) verwendet. Die Komponenten des Bindemittels, die nicht direkt gemessen werden konnten (CO2, H2O+) wurden indirekt durch ein Berechnungsverfahren ermittelt.Die gesammelten Daten belegen, dass die meisten untersuchten Proben (i.e. Mörtel von Monumenten aus Pisa) zwei Typen von Bindemittel enthalten: Der erste Typ entspricht einem gewöhnlichen karbonatisierten Kalk. Der zweite Typ ist ein hydraulischer Kalk, in dem die Karbonatkomponente mit einer mengenmäßig bedeutenden Silikatfraktion assoziiert ist, die 13–89 Gew.% des gesamten Bindemittels ausmachen kann (durchschnittlich 47%). Dieser zweite Typ wurde häufig beim Bau alter Monumente in Pisa verwendet, z.B. wurde er ständig beim Bau des Schiefen Turms herangezogen. Diese Studie zeigt, dass die Silikatfraktion dieses hydraulischen Mörtels, die röntgenamorph ist, aus einem hydratisierten Aluminosilikat mit einem niedrigen Al2O3/SiO2 Verhältnis (im Durchschnitt 0.125) besteht.Auf Basis der chemischen und optischen Charakteristika des hydraulischen Mörtel, die pozzolanische Aggregate führen, schließen wir, dass diese Mörtel höchstwahrschein lich durch Mischung von Löschkalk mit sehr reaktivem, silikatischen Material, wie etwa Diatomeenerde hergestellt wurden.
  相似文献   

6.
A record of mortar and salt analyses from the last 20 years on various monuments in Saxony demonstrates the close relation between the occurrence of magnesium sulphate salts and the use of dolomitic lime mortars in a regional frame. The regional distribution scheme of dolomitic lime in historic mortars depends on the geological setting of the territory, i.e. the natural occurrence of dolomite deposits. Sulphation of these mortars with the formation of magnesium sulphate and gypsum is mainly due to environmental pollution, as can be shown by sulphur stable isotope analyses. Exposure of the sulphated mortar surfaces to rain leads to the preferential dissolution and advective transport of the novel formed magnesium sulphate salts, which effloresce or subfloresce on the mortar surface or can be accumulated in the structure of adjoining porous building materials like natural stones. These processes may cause severe damages in mortars by the weakening of the binder and in porous stones by salt crystallisation of phases like epsomite and hexahydrite.  相似文献   

7.
In this study, an investigation was performed to determine if lime-stabilized sand–bentonite mixtures are appropriate for the construction of sanitary landfills liners. For this aim, the hydraulic conductivity tests were conducted in the laboratory on sand–bentonite mixtures and lime-stabilized sand–bentonite mixtures to evaluate the effect of wetting–drying cycles. The hydraulic conductivity tests were performed to see if their hydraulic conductivities are affected by wetting–drying cycles. First series of specimens have been prepared as a mixture of sand and bentonite only. In the first series of specimens, sand was mixed with bentonite in proportions of 20, 30, 40, and 50 %. In the second series of the specimens, lime in proportions of 1, 2 and 3 % by weight was added to the mixtures of sand–bentonite in proportions of 20, 30, 40, and 50 %. From the results of the tests, it was observed that while optimum water content increased, maximum dry density decreased with addition of lime to the sand–bentonite mixtures. Generally, the hydraulic conductivity increased with the addition of lime to the mixtures but at low percentages of lime (1–2 %), however, slight decreases in k were recorded. It was also observed that the wetting–drying cycles on the permeability test indicate cure effect on specimens with addition of lime which resulted in decreased the hydraulic conductivity.  相似文献   

8.
An experimental study was performed to investigate the effect of perlite and perlite–lime admixtures on classification, shear strength, and durability properties of an expansive soil containing smectite clay minerals. Two types of mixtures, namely soil–perlite and soil–perlite–lime, were prepared with different percentages of perlite and compacted with standard Proctor energy at their optimum water contents. Samples of 38 mm diameter and 76 mm height for durability tests and square samples of 60 mm edge for shear box test were taken and preserved until test time in a desiccator. Disturbed samples were also taken to determine liquid and plastic limits. The expansive soil shows behavior of fine sand and silt due to pozzolanic reactions in microstructure caused by addition of lime and perlite. Although apparent cohesion of treated soil decreased with increasing amount of perlite for both types of samples, perlite–lime-treated samples had higher apparent cohesion than only perlite-treated samples. Large increments in angle of shearing resistance were obtained with increasing usage of perlite. Samples stabilized with only perlite could not show enough durability at the durability tests based on volumetric stability and unconfined compression strength. However, samples stabilized with lime and more than 30 % perlite proved to have enough durability and shear strength.  相似文献   

9.
Pozzolanic fly ash as a hydraulic barrier in land fills   总被引：2，自引：0，他引：2  
The liner plays an important role in controlling migration of contaminants present in the leachate in waste containment systems such as land fills and impoundments. Although questions have been raised about the performance of clay liners, they are increasingly used singly or as double liners in disposal sites. Though the clay liners possess many advantages such as low permeability and large attenuative capacity, they also possess high shrinkage potential and hence can crack under unsaturated conditions causing instability and increase in leakage rates. Further, the permeability of the clay linear can increase due to clay–pollutant interaction. This study examines the potential of pozzolanic fly ash as a hydraulic barrier in land fill. The behaviour of three different types of fly ashes, showing a range of physical properties and chemical composition from three different sources are reported in the study. Geotechnical properties, needed to evaluate the use of fly ashes as barriers, such as shrinkage, compaction, permeability, consolidation and strength characteristics are reported. The results show that fly ashes possess low shrinkage and hence do not crack. Compacted fly ashes undergo very little volume changes. They also show that pozzolanic fly ashes develop good strength properties with time. Pozzolanic fly ashes containing sufficient lime develop strength even without addition of lime. Non-pozzolanic fly ashes do not develop strength even on addition of lime. Fly ashes generally consist of silt size particles and consequently possess high permeability. However, pozzolanic fly ashes with lime exhibit low permeability on curing because of the formation of gelatinous compounds which block the pores. Thus, pozzolanic fly ashes appear to be promising for construction of liners to contain alkaline leachate.  相似文献   

10.
Lime treatment of loess in foundation engineering modifies the soil structure, leading to changes in mechanical and hydraulic properties of soil, which in turn will affect the flow of water and transport of contaminants in the loess. In light of this, it is essential to identify the dominant effects of different lime treatments on hydraulic conductivity, and to ascertain the optimum lime treatment. For this purpose, we investigated the effects of dry density and lime content on changes in hydraulic conductivity and microstructure of loess in Yan’an City, China. The results indicate that hydraulic conductivity has a log negative correlation with dry density, and lime addition can result in a decrease of hydraulic conductivity of loess at the same dry density. Under a given degree of compaction, however, lime addition can lead to a decrease in dry density due to an increase in flocculation and aggregations. The significant decrease of dry density leads to an increase in hydraulic conductivity when lime content (in mass percentage) is lower than 3%. Nevertheless, when lime content is higher than 3%, the reactions between loess particles and lime will be intensified with an increase in lime content, and become the primary factors affecting pore characteristics. These reactions can further decrease the hydraulic conductivity of lime-treated loess, and the lowest hydraulic conductivity was obtained for lime-treated loess with 9% lime content. The excess lime (above 9% lime content) dramatically increased pore size, leading to a significant increase in hydraulic conductivity. Therefore, 9% is the optimum lime content for loess treatment, and the degree of compaction in engineering should be higher than 95%. In addition, statistical analysis of microstructure of lime-treated loess shows that the distribution trends of macro- and meso-pores coincided with that of saturated hydraulic conductivity, which indicates that lime content affects saturated hydraulic conductivity of lime-treated loess by changing the soil structure, especially the properties of pores larger than 8 µm.  相似文献   

11.
Gypsum-based mortars were widely used during the Mudejar artistic period in Spain from the 12th to 16th century. During restoration works, compatibility between the new repair mortars and the original components is essential for an adequate intervention on the monument. The increasing interest of knowing the properties of the gypsum-lime-based mortars for restoration purposes justifies the research carried out. Different mortars compatible with traditional building materials were elaborated by varying the binder proportions, the type of aggregates, the binder/aggregate ratios and the curing time. The main goal of this paper is to characterize the mechanical behaviour and the pore structure of the mortars as a function of curing time. The influence between the different variables used to prepare the mortars and the development of the carbonation process over time is also considered. Mechanical strength and porosity measurements as well as X-ray diffraction and thermal analysis were performed after curing times of 1, 28 and 90 days. The results obtained confirmed a progressive increase in mechanical strength linked to the carbonation of the mortars prepared. Less lime binder and also aggregate contents showed the highest rise in strength over time, related to the highest initial porosity which favoured the carbon dioxide flow. The use of siliceous aggregates (GL-QS mortars) obtained the best results in the development of physico-mechanical properties over curing time. The knowledge obtained from the studied mortars provides practical information to establish a suitable mortar mixture for restoration works on historic buildings and modern architecture where gypsum-lime-based mortars are used.  相似文献   

12.
Repair mortars with different B/Ag (binder/aggregate) ratios and natural stone were studied in order to understand the influence of limestone aggregate on the properties of mortar and to check the compatibility of repair mortar with a porous limestone. Three different types of mortars with three different aggregate contents were evaluated by using mercury intrusion porosimetry (MIP) and water saturation method (WSM). Changes in density and uniaxial compressive strength as a function of aggregate content were also recorded. For comparison the properties of the porous limestone were also tested, since it is used in monuments and also as aggregate in the mortar. Tested mortars had average porosities of 27.0 % (±2.0), while oolitic limestone has higher average porosity of 32.2 % (±1.9). The limestone has mainly medium and large pore radii (1–100 μm) while the repair mortars even with high aggregate content has predominantly smaller pores. All but one pure repair mortars have higher uniaxial compressive strength than that of the oolitic limestone. The strength decreases while porosity increases with increasing aggregate content.  相似文献   

13.
Water (in the solid, liquid and vapour state) is one of the main factors that drive construction materials to deterioration. To assess the quality and durability of a repair rendering mortar, thus ensuring its protective function in the masonry structure, it is fundamental to study the behaviour of this mortar towards water. Mortars were elaborated with a calcitic dry hydrated lime, a calcareous aggregate, a pozzolan, a lightweight aggregate, a water-retaining agent and a plasticiser. The effect of different binder-to-aggregate proportions on the mortars’ hygric behaviour was assessed by performing free water absorption and drying, capillary uptake, hydraulic conductivity and water vapour permeability tests. Another aspect that was considered in the assessment of mortar quality was the drying shrinkage that was measured by means of a non-standardised device. It has been found that a larger amount of water is absorbed by mortars with higher lime content, whilst faster drying and higher permeability to water and water vapour are obtained in mortars with higher aggregate content. The hygric behaviour as well as the drying shrinkage of mortars has been interpreted taking into account the differences in microstructure and pore system between mortars.  相似文献   

14.
Melting experiments have been performed at 3 GPa, between 1150 and 1450 °C, on a phlogopite-peridotite source in the garnet stability field. We succeeded to extract and determine the melt compositions of both phlogopite-bearing lherzolite and harzburgite from low to high degrees of melting (? = 0.008–0.256). Accounting for the presence of small amounts of F in the mantle, we determined that phlogopite coexists with melt >150 °C above the solidus position (1150–1200 °C). Fluorine content of phlogopite continuously increases during partial melting from 0.2 to 0.9 wt% between 1000 and 1150 °C and 0.5 to 0.6 wt% between 1150 and 1300 °C at 1 and 3 GPa, respectively. The phlogopite continuous breakdown in the lherzolite follows the reaction: 0.59 phlogopite + 0.52 clinopyroxene + 0.18 garnet = 0.06 olivine + 0.23 orthopyroxene + 1.00 melt. In the phlogopite-harzburgite, the reaction is: 0.93 phlogopite + 0.46 garnet = 0.25 olivine + 0.14 orthopyroxene + 1.00 melt. Melts from phlogopite-peridotite sources at 3 GPa are silica-undersaturated and are foiditic to trachybasaltic in composition from very low (0.8 wt%) to high (25.6 wt%) degrees of melting. As observed at 1 GPa, the potassium content of primary mantle melts is buffered by the presence of phlogopite, but the buffering values are higher, from 6.0 to 8.0 wt% depending on the source fertility. We finally show that phlogopite garnet-peridotite melts are very close to the composition of the most primitive post-collisional lavas described worldwide.  相似文献   

15.
The study focused on the feasibility of high NH4 +–N (400–600 mg/L) and COD load at two different hydraulic retention times (HRTs = 36 and 24 h) in two identical aerobic–anoxic sequencing bioreactors which were constructed in series in a single system using a specifically designed single biomass containing autotrophic nitrifying and heterotrophic denitrifying bacteria. Internal recirculation of synthetic wastewater from one tank to other was not carried out like the conventional aerobic–anoxic processes. Cycles of 15 days under sequences of aerated and non-aerated periods of three hour each were repeated during each continuous flow experiment conducted. Sodium bicarbonate and sodium acetate were selected as the appropriate inorganic and organic carbon sources. The results showed that the HRT may not affect the simultaneous nitrification and denitrification processes. Average nitrification ratio was obtained to be above 20 mg/L NH4 +–N/h daily. Results of 90 days’ operation also showed high removal efficiencies of ammoniacal nitrogen of about 83% daily. The main advantage of this process includes efficient ammoniacal nitrogen removal without separated aerobic and anoxic tanks, decrease operating costs due to the lesser oxygen concentration requirement in the bioreactors.  相似文献   

16.
Gypsum Induced Strength Behaviour of Fly Ash-Lime Stabilized Expansive Soil   总被引：1，自引：1，他引：0  
Physical and engineering properties of soil are improved with various binders and binder combinations. Fly ash and lime are commonly used to improve the properties of expansive soils. An attempt has been made, in this paper, to examine the role of gypsum on the physical and strength behaviour of fly ash-lime stabilized soil. The change in strength behaviour is studied at different curing periods up to 90 days, and the mechanism is elucidated through pH, mineralogical, microstructural and chemical composition study. The strength of soil-fly ash mixture has improved marginally with the addition of lime up to 4 % lime and with curing period for 28 day. Significant increase in strength has been observed with 6 % lime and enhanced significantly after curing for 90 days. The variations in the strength of soil with curing period is due to cation exchange and flocculation initially, and binding of particles with cementitious compounds formed after curing. With addition of 1 % gypsum to soil-fly ash-lime, the strength gain is accelerated as seen at 14 day curing. The accelerated strength early is due to formation of compacted structure with growth of ettringite needles within voids. However, strength at curing for 28 day has been declined due to annoyance of clay matrix with the increase in size of ettringite needle; and again increased after curing for 90 days. The rearrangement of clay matrix and suppression of sulphate effects with formation of cementitious compounds are observed and found to be the main responsible factors for strength recovered.  相似文献   

17.
The geochemical characteristics of melt inclusions and their host olivines provide important information on the processes that create magmas and the nature of their mantle and crustal source regions. We report chemical compositions of melt inclusions, their host olivines and bulk rocks of Xindian basalts in Chifeng area, North China Craton. Compositions of both bulk rocks and melt inclusions are tholeiitic. Based on petrographic observations and compositional variation of melt inclusions, the crystallizing sequence of Xindian basalts is as follows: olivine (at MgO > ~5.5 wt%), plagioclase (beginning at MgO = ~5.5 wt%), clinopyroxene and ilmenite (at MgO < 5.0 wt%). High Ni contents and Fe/Mn ratios, and low Ca and Mn contents in olivine phenocrysts, combining with low CaO contents of relatively high MgO melt inclusions (MgO > 6 wt%), indicate that Xindian basalts are possibly derived from a pyroxenite source rather than a peridotite source. In the CS-MS-A diagram, all the high MgO melt inclusions (MgO > 6.0 wt%) project in the field between garnet + clinopyroxene + liquid and garnet + clinopyroxene + orthopyroxene + liquid near 3.0 GPa, further suggesting that residual minerals are mainly garnet and clinopyroxene, with possible presence of orthopyroxene, but without olivine. Modeling calculations using MELTS show that the water content of Xindian basalts is 0.3–0.7 wt% at MgO = 8.13 wt%. Using 20–25 % of partial melting estimated by moderately incompatible element ratios, the water content in the source of Xindian basalts is inferred to be ≥450 ppm, much higher than 6–85 ppm in dry lithospheric mantle. The melting depth is inferred to be ~3.0 GPa, much deeper than that of tholeiitic lavas (<2.0 GPa), assuming a peridotite source with a normal mantle potential temperature. Such melting depth is virtually equal to the thickness of lithosphere beneath Chifeng area (~100 km), suggesting that Xindian basalts are derived from the asthenospheric mantle, if the lithospheric lid effect model is assumed.  相似文献   

18.
The effects of rate of strain on strength and deformation characteristics of soil–lime were investigated. Five strain rates (0.1, 0.8, 2.0, 4.0 and 7.0 %/min), five lime contents (0, 3, 6, 9 and 12 %) by dry soil weight and three cell pressures (100, 200 and 340 kN/m2) were carried. Triaxial tests, under unconsolidated condition, were used to study the effect of strain rate on strength and initial modulus of elasticity of soil and soil–lime mixture after two curing periods 7 and 21 days, respectively. A total of 405 triaxial specimens have been tested, where 225 specimens have been tested with first curing period (7 days). The testing program includes nine specimens for each strain rate, and each lime content was carried out, including natural soil with zero lime content. Another set of triaxial tests with a total of 180 specimens for the second curing period (21 days) was prepared at optimum moisture content, and the corresponding maximum dry density was also tested. The effects of strain rate and curing period on each of stress–strain behavior, type of failure, deviator stress at failure, cohesion and angle of internal friction and initial modulus of elasticity were studied thoroughly for the natural soil as well as soil–lime mixtures. For natural soil, the test results showed that the undrained shear strength, the initial modulus of elasticity and the cohesion increase significantly as the strain rate increase, while for soil–lime mixture at different curing periods, the undrained shear strength, initial modulus of elasticity and the cohesion increases to a maximum and then decreases as the strain rate and lime content increase. Also, the same variables and angle of internal friction increase with increasing curing period.  相似文献   

19.
The decomposition of phenol and trichlorophenol (TCP) by using granular ferric hydroxide (GFH) as a photo-Fenton catalyst was investigated and compared with homogeneous photo-Fenton process. Experiments were conducted in a batch mode, duplicate for the degradation of phenol and TCP in the presence of solar light for both the processes. The effect of operating variables for heterogeneous photo-Fenton process like pH, peroxide concentration and GFH concentration on the degradation of the model compounds was optimized by univariate approach. The optimum conditions for the degradation of phenol and TCP were pH 3.0 ± 0.2, peroxide concentration 29.4 mM for phenol and 14.7 mM for TCP at GFH concentration of 0.5 g/500 mL. At optimum conditions, the mineralization efficiency of phenol and TCP by heterogeneous process was compared with homogeneous process. The mineralization efficiency for phenol and TCP was 96 and 86 %, respectively, for heterogeneous photo-Fenton process, while almost complete mineralization (~96 %) was observed for homogeneous process. In heterogeneous photo-Fenton process, longer reaction time was witnessed for complete mineralization of the compounds studied. Low molecular weight aliphatic acids like oxalic acid, acetic acid and inorganic chloride ion (in case of TCP) were observed during both the processes. In these processes, the reaction proceeds by hydroxyl radical (·OH) abstraction of the model compound studied. The mineralization of phenol and TCP obeys pseudo-first-order kinetics irrespective of the processes studied. The results indicate that GFH can be an effective heterogeneous photo-Fenton catalyst for the degradation of phenol and TCP.  相似文献   

20.
Epidote-rich eclogitic metagabbro forms a small body within the Lanzada Window, upper Val Malenco, where it is associated with serpentinites and supracrustal rocks of the Lanzada–Santa Anna Zone (LSZ), which lies structurally beneath the Malenco unit. Conventional garnet–clinopyroxene geothermometry and garnet–clinopyroxene–phengite geobarometry indicate that the peak-metamorphic mineral assemblage (garnet + omphacite + epidote + phengite + titanite + apatite + pyrite) equilibrated at ca. 2.0 GPa and 525 °C. The bulk composition is Ca-rich (wollastonite-normative), suggesting that the rock underwent Ca-metasomatism prior to high-P metamorphism. The presence of eclogite within the LSZ strengthens the correlation of the LSZ with the blueschist-bearing Avers Bündnerschiefer, and confirms the former existence of a southerly-dipping subduction zone beneath the Malenco unit.  相似文献   

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