Microstructural characteristics,porosity and strength development in ceramic-laterized concrete

Interfacial bonding between constituent materials and pore sizes in a concrete matrix are major contributors to enhancing the strength of concrete. In a bid to examine how this phenomenon affects a laterized concrete, this study explored the relationship between the morphological changes, porosity, phase change, compressive, and split tensile strength development in a ceramic-laterized concrete. Varying proportions of ceramic aggregates, sorted from construction and demolition wastes, and lateritic soil were used as substitutes for natural aggregates. Strength properties of the concrete specimens were evaluated after 7, 14, 28 and 91 days curing, but morphological features, using secondary electron mode, were examined only at 7 and 28 days on cured specimens, using Scanning electron microscope (SEM). From all the mixes, selected samples with higher 28 day crushing strength, and the reference mix, were further characterized with more advanced analysis techniques, using the mercury intrusion porosimetry (MIP), thermogravimetric analysis (TGA), X-ray Diffractometer, and SEM (backscatter electron mode-for assessment of the interfacial transition properties between aggregates and paste).The reference mix yielded higher mechanical properties than the concrete containing secondary aggregates, this was traced to be as a result of higher peaks of hydration minerals of the concrete, coupled with its low tortuosity and compactness. However, a laterized concrete mix containing both 90% of ceramic fine and 10% of laterite as fine aggregate provided the optimal strength out of all the modified mixes. Although, the strength reduction was about 9% when compared with the reference case, however, this reduction in strength is acceptable, and does not compromise the use of these alternative aggregates in structural concrete.     

Enhancing mineral liberation of a Canadian rare earth ore with microwave pretreatment

Liberation, as an attribute of mineralogy characteristic, whose impacts on finely disseminated Canadian rare earth ore was studied with microwave pretreatment. Samples of a light rare earth ore along with mostly ankerite and biotite as dominant gangue minerals as well as bastnaesite, strontianite and goethite as dominated minerals were exposed to further comminution by ball mill and microwave pretreatment fragmentation. Mineralogical characteristics were analyzed by using a mineral liberation analyzer (MLA). The results indicated that tight association mutually penetrates among dominated minerals in the range size of ?300 + 212 μm and ?212 + 150 μm and gangue minerals in the form of adjacent type, fine vein type, shell type and packing type. Temperature in the ore samples pre-treated by microwave can rapidly rise to 250 °C with microwave power of 0–1.5 kW and microwave time of 0–2 min. Applying the microwave pretreatment merely reduces the hardness of the ore causing the fracture of rare earth ore, but this does not transform or change the original mineralogy characteristics of the ore samples. On the basis of above study, the liberation value of bastnaesite, strontianite and goethite with microwave pretreatment is greater than with conventional comminution when the liberation class is above 75%. The distribution of particle size of rare earth ore samples is better with microwave pretreatment than with conventional comminution for particle size of 7.4 × 10^?5 m. With microwave pretreatment, the theoretical grade–recovery of bastnaesite, strontianite and goethite in the rare earth ore attains better results than with conventional comminution at a given grade.     

Stabilized Dredged Material. III: Mineralogical Perspective

The prior two papers in this series reported on the geoenvironmental and geomechanical properties of 20 stabilized dredged material (SDM) blends using dredged material (DM) from the U.S. Army Corps of Engineers Craney Island confined disposal facility. The pozzolans included lime, cement kiln dust (CKD), class F fly ash, and two cements (portland and slag cement). This paper reports on the mineralogical evolution of the SDM blends over a 6-month curing period using techniques new to mainstream geotechnical engineering: X-ray diffraction (XRD) with Rietveld quantification analysis which allows direct quantitative mineralogical comparisons between soil samples. Despite being classified as a high plasticity clay-organic clay (CH/OH soil), XRD showed that the DM contained no montmorillonite, illite or kaolinite, and was thus mineralogically unreactive. The quartz, feldspar, and mica contents were numerically tracked and were shown to remain stable 6 months after blending. The chlorite (in DM) content decreased over time and with the fly ash served as the sources of soluble silica and alumina for pozzolanic reactions especially in the lime-based SDM blends. Lime in the lime-based blends persisted in significant quantities (3%) as unreacted portlandite [Ca(OH)2] even at 6 months curing, indicating that the solubility of silica in the DM was the limiting factor for strength development. New (ettringite and hydrocalumite) mineral formation was quantified. CKD provided high early strength (7 and 28 days) when used in combination with small amounts of lime that provided prolonged pH buffering; CKD alone or in combination with fly ash did not maintain elevated pH (>10.8) over 6 months. Overall, the unconfined compressive strength, pH, and mineralogy results at 6 months were substantially different compared to the standard curing time of 28 days, confirming similar findings of previous long-term stabilization-solidification studies.     

辽宁野猪沟铁矿石工艺矿物学研究

系统地研究了辽宁野猪沟铁矿石的化学组成、矿物组成及嵌布特征。结果表明：矿石以鲕状构造为主,具有典型的同心环带结构。矿石中铁、锰矿物主要以粉末状和致密块状两种状态存在。粉末状赤铁矿、褐铁矿、氧化锰多形成松散的土状集合体,致密块状的赤铁矿则分布于石英砂粒周围;磁铁矿多包裹石英砂粒。矿石的上述特性造成有用矿物难以单体解离并易于泥化,因而使矿石难选。     

Hydrodynamics of Bubble-Mineral Particle Collisions

Abstract

This chapter surveys the hydrodynamic interactions between particles and bubbles in flotation. Some new approximate equations are given for collision efficiency. It is shown that collision processes of particles with bubbles are less effective than sliding processes because of their short duration and the strong deformation of the bubble at the collision point. Methods are suggested to estimate collision and sliding times. During contact between a particle and a bubble, the just forming thin liquid film must drain off and rupture. Therefore, possible ways of calculating film drainage time are discussed. Furthermore, possible experimental methods to determine these quantities are briefly described and recent experimental results presented.     

金厂沟梁金矿氰化原矿的工艺矿物学研究

金厂沟梁金矿氰化原矿的工艺矿物学研究是在原矿金赋存状态研究基础上进行的．通过研究查清了氰化原矿的微量元素的特征、粒度的分布特征和氰化原矿的矿物成分．确定了金的赋存状态,进而对选治工艺进行了讨探,为提高金的选冶回收率提供了可靠的依据．     

Geochemistry of the Detroit River Sediments

The objectives of the investigation were to provide information on the concentration and distribution of metals in bottom sediments of the Detroit River and to study the association of metals with various sediment components. Concentrations of major elements (Si, Al, Ca, Mg, Na, K, Fe, Mn, and P) and metals (Co, Cr, Cu, Ni, Pb, and Zn), particle size distribution, and mineralogical composition were determined in 20 surficial sediment samples collected along the Detroit River in 1983. Significantly higher concentrations of metals in the Detroit River sediments than those reported in Lake St. Clair and Lake Erie sediments indicated input from sources in the river's drainage basin. Poor relationships exist between the metals and organic C and the metals and the silt-clay size fraction (< 63 μm). The association of metals with sediment particles was investigated by a separation of sediment into seven size fractions ranging from < 13 to > 63 μm. Zn, Ni, Cr, and Pb were accumulated in the < 13 μm size fraction. However, Cu and Cr concentrations were highest in the < 13 and 48 to 63 μm fractions. Quartz, feldspars, and calcite were found in the > 63 μm fraction. Dolomite, feldspars, and quartz were in the 13 to 63 μm fraction and the clay minerals illite, chlorite, and kaolinite were in the < 13 μm fraction. Concentrations and relationships among major elements reflected the mineralogical composition of different particle size fractions.     

Evaluation of reduction roasting and magnetic separation for upgrading Mn/Fe ratio of fine ferromanganese

Low grade ferromanganese tailing was subjected to different mineralogical techniques, reduction roasting and magnetic separation to establish whether commercially acceptable manganese qualities and high Mn/Fe ratio could be obtained, and also to determine the best processing route for beneficiating this ore. The main manganese mineral within the feed sample is birnessite, with minor amounts of pyrolusite and todorokite. Size by assay analysis conducted presented a result with a yield of about 35.75% and Mn grade of 27.63% to coarse (?3.35 + 1 mm) and yield of 20.24% and Mn grade of 27.71% to (?1.18 + 0.50 mm) fraction. Two-stage high induced magnetic separations at 16,000 and 11,000 G produces Mn grades with similar grade to that obtained from the ferromanganese feed sample. Reduction roasting followed by magnetic separation on ?1.18 + 0.50 mm at 1000 G recovered 72.31% Mn with a grade of 58.44% Mn, 2.52% Fe and 3.29% Si at Mn/Fe ratio of 23.22. This study reveals the influence of roasting in converting the hematite and goethite to magnetite and the response of the roasted fraction to magnetic separation.     

X-ray powder diffraction-based method for the determination of the glass content and mineralogy of coal (co)-combustion fly ashes

The relevance of Al-Si glass in a number of fly ash applications, such as use as a pozzolanic material, zeolite synthesis, and geopolymer production, necessitated research towards investigation of methods for an easy and consistent determination of the glass content in this coal (co)-combustion by-products. A glass standard-addition X-ray powder diffraction (XRD)-based method is proposed in this study as an alternative to the non straightforward procedure of conventional methods for determining the amorphous components, mainly by difference of the total mass and the addition of quantified crystalline species. A >99% Al-Si glass slag sample was selected as a standard for glass. A number of glass standard/fly ash mixtures were performed on Fluidized Bed Combustion (FBC) and pulverized coal combustion (PCC) fly ashes and subsequently analyzed by XRD. The method provides results closer to quantitative proportions of the Al-Si amorphous material of this (co)-combustion by-product, with a range of values <3% when compared with those obtained by the conventional Reference Intensity Method (RIM) method, demonstrating suitability and consistence of the procedure. Furthermore, by the proposed method, the requirement of previous determination of the mineral phases of conventional techniques is avoided. Coupled with the easy calculations, this allowed a fast determination of the glass content of (co)-combustion fly ash. The mineralogy of FBC and PCC fly ash was also investigated using the RIM method. The occurrence and proportions of the crystalline components in fly ash are in line with the combustion technology and their inherent operational parameters, especially the (co)-combustion temperature. The FBC fly ash shows the highest content of relic phases from feed coal (quartz, illite, calcite, and feldspars) and lower contents of amorphous components. The PCC fly ash are characterized by the highest proportions of mullite and Al-Si glass and low contents of quartz an other relict phases. The occurrence and distribution of anhydrite and Fe-oxide species appears to be related to the content of Ca and Fe in the feed fuels, showing slightly higher contents in FBC than in PCC fly ash.     

Process Control in metallurgical plants—From an Xstrata perspective

Some history and modern practice of Process Control in metallurgical operations is reviewed. Clearly the early deliverables from the pioneer days in the 1950s through to the 1970s and early 1980s were under-appreciated. The discipline has since grown into a more visible, sophisticated and accepted practice as a result of the assembly of appropriately recruited and trained individuals and teams, who have successfully negotiated deliverable projects that impact all metallurgical performances beyond early milling processes. The skill set in these individuals and teams essentially includes organisational behaviour in addition to their specialist technical attributes. A strong network to internal and external specialists and experts is essential. Furthermore, instrumentation and control technology has improved immensely. The challenge in the current modern practice is to win support of senior management in operations for the project cost, schedule and deliverables of Process Control. Once gained, this acceptance then amounts to the logistics of project scope and delivery—a track record well-demonstrated by the Xstrata Process Control Group.