伊利石的开发与应用

伊利石与叶蜡石不仅外观相似 ,物理性能相近 ,而且在浙东南 ,它们的地质成矿条件和分布区域也大致相同。有些地质专家将它们都归入“广义的蜡石”之列。叶蜡石的资源丰富 ,储量大 ,开发利用早 ,对伊利石的开发应用起到一个先导的作用。但深度开发是目前两个矿种面临的共同课题。

Effect of particle size and grain composition on two-dimensional infiltration process of weathered crust elution-deposited rare earth ores

The two-dimensional infiltration experiment was carried out by means of digital image technology.The evolution process of the wetting body was described.The wetted front distance and the time show a very significant power function relationship.The horizontal wetted distance is larger than the vertical wetted distance in the initial stage.Then,the vertical distance of the wetted body gradually approaches to the horizontal distance.The infiltration distance decreases as the content of fine particles increases.The wetted front migration rate curve shows a three-stage change law,and it increases with the increase of coarse particle content.The directional velocity ratio is defined.The initial value of horizontal infiltration rate is larger than that of vertical one,and then the vertical infiltration rate is gradually close to the horizontal value.The empirical relationship between the characteristic particle size and the stable infiltration rate is established,which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.

Soil−water characteristics of weathered crust elution-deposited rare earth ores

The permeability of the weathered crust elution-deposited rare earth ores directly affects the efficiency of in-situ leaching.The soil−water characteristic curve(SWCC)is an important constitutive relation for calculating the permeability of ore body,which is related to many factors.Soil−water characteristic tests of rare earth ore samples considering different factors were carried out by using the pressure plate instrument.Effects of dry density,particle size and solution leaching on water holding behavior and the mechanism were investigated.The experimental observations indicate that with the decrease of dry density,the pore ratio increases gradually,and the saturated water content increases.Under the same matric suction,the water content decreases gradually with the increase of particle size,thus decreasing water holding capacity of ore accordingly.In the same water content,matric suction is inversely proportional to particle size.Under the same matric suction,the water content of ore samples after leaching is less than that of the ore samples before leaching,indicating that solution leaching can decrease water holding capacity of ore.

Particle Size Distribution of Kaolinite and Halloysite in Weathering Products of Granite and Its Implications for Pedogenesis

The kaolins collected from a profile of weathered granite at Yichun County, Jiangxi Province have been subjected to particle size fractionation by the conventional sedimentation method and examined by XRD,SEM and TEM. All of them exhibit a mixture phase of poorly crystallized kaolinites and halloysites (0.7 nm) occurring as the main clay minerals. Electron micrographs reveal that plate kaolinites are the principal constitution in the coarse fraction, and more tubular and curled halloysite (0.7 nm) in the fine fraction. Both of them show normal probability curves in particle size distributions. The ratios of kaolinite and halloysite (0.7 nm) in different size fractions are examined by X-ray diffraction with a series of X-ray patterns characterized by three main peaks at d(001), d(002) and d(020),varying in intensity. Therefore, an index Qhm, expressed as (Id(001) + Id(002))/(2×Id(020)), is designed to indicate relative ratios of the two clay minerals in a number of mixture phases. Because kaolinite and halloysite (0.7nm) commonly occurred, respectively, in low and medium leaching microenvironment, the index Qhm can be used to indicate weathering and pedogenic.conditions of a weathering crust.

Effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on chloride migration through concrete subjected to repeated loading

The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and 5%,10% SF,respectively.Five times repeated loadings were applied to specimens,the maximum loadings were 40% and 80% of the axial cylinder compressive strength(f′c),respectively.Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured.The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete,but 40% GGBFS replacement increases the transport number of chloride.Five loadings at 40% f′cor 80% f′c increase the transport number of chloride for all mixes investigated in this study.5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′cor 80% f′c.

Effects of Al_2O_3 nanoparticles on properties of self compacting concrete with ground granulated blast furnace slag (GGBFS) as binder

In this work, strength assessments and percentage of water absorption of self compacting concrete containing ground granulated blast furnace slag （GGBFS） and A1203 nanoparticles as binder have been investigated. Portland cement was replaced by different amounts of GGBFS and the properties of concrete specimens were investigated. Although it negatively impacts the physical and mechanical properties of concrete at early ages of curing, GGBFS was found to improve the physical and mechanical properties of concrete up to 45 wt% at later ages. A1203 nanoparticles with the average particle size of 15 nm were added partially to concrete with the optimum content of GGBFS and physical and mechanical properties of the specimens were measured. A1203 nanoparticle as a partial replacement of cement up to 3.0 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca（OH）2 amount at the early ages and hence increase strength and improve the resistance to water permeability of concrete specimens. The increase of the A1203 nanoparticles＇ content by more than 3.0 wt% would cause the reduction of the strength because of the decreased crystalline Ca（OH）2 content required for C-S-H gel formation. Several empirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of the peaks related to hydrated products in X-ray diffraction results, all indicate that A1203 nanoparticles could improve mechanical and physical properties of the concrete specimens.

Sorption of Water-Extractable Organic Carbon in Various Clay Subsoils: Effects of Soil Properties

Clay-rich subsoils are added to sandy soils to improve crop yield and increase organic carbon （C） sequestration; however, little is known about the influence of clay subsoil properties on organic C sorption and desorption. Batch sorption experiments were conducted with nine clay subsoils with a range of properties. The clay subsoils were shaken for 16 h at 4 ℃with water-extractable organic C （WEOC, 1 224 g C L-1） from mature wheat residue at a soil to extract ratio of 1：10. After removal of the supernatant, the residual pellet was shaken with deionised water to determine organic C desorption. The WEOC sorption was positively correlated with smectite and illite contents, cation exchange capacity （CEC） and total organic C, but negatively correlated with kaolinite content. Desorption of WEOC expressed as a percentage of WEOC sorbed was negatively correlated with smectite and illite contents, CEC, total and exchangeable calcium （Ca） concentrations and clay content, but positively correlated with kaolinite content. The relative importance of these properties varied among soil types. The soils with a high WEOC sorption capacity had medium CEC and their dominant clay minerals were smectite and illite. In contrast, kaolinite was the dominant clay mineral in the soils with a low WEOC sorption capacity and low-to-medium CEC. However, most soils had properties which could increase WEOC sorption as well as those that could decrease WEOC sorption. The relative importance of properties increasing or decreasing WEOC sorption varied with soils. The soils with high desorption had a low total Ca concentration, low-to-medium CEC and low clay content, whereas the soils with low desorption were characterised by medium-to-high CEC and smectite and illite were the dominant clay minerals. We conclude that WEOC sorption and desorption depend not on a single property but rather a combination of several properties of the subsoils in this study.

Modulation of Soil Particle Size and Nutrient Availability in the Maize Rhizosheath

Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field experiments.The results showed that there was a significant size decrease of soil particles in the rhizosheath.Meanwhile,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of maize.The contents of Fe and Mn were also differentially altered in the rhizosheath.Rhizosheath development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental period.The formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient availability.The subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.