Search Documents

By Bruce H. Mason

Lightweight aggregates are classified as those minerals, natural rock materials, rock-like products, and byproducts of manufacturing processes that are used as bulk fillers in lightweight structural concrete, concrete building blocks, precast structural units, road surfacing materials, plaster aggregates, and insulating fill. Other uses include architectural wall covers, suspended ceilings, soil conditioners, and other agricultural uses (Mason, 1989). One unusual agricultural use recently reported was for bedding on a crocodile farm on the south coast of Natal. It seems that female crocodiles became upset because there was no vermiculite in which to lay their eggs due to the late arrival of a consignment of vermiculite. The vermiculite was being used as a substitute for river sand to nest crocodile eggs (Griffiths, 1989). The various lightweight aggregate materials may be classified into four groups as follows: 1. Natural Lightweight Aggregate Materials-prepared by crushing and sizing natural rock materials, such as pumice, scoria, tuff, breccia, and volcanic cinders. 2. Manufactured Structural Lightweight Aggregates-prepared by pyroprocessing shale, clay, or slate in rotary kilns or on traveling grate sintering machines. 3. Byproduct Lightweight Aggregates-prepared by crushing and sizing foamed and granulated slag, cinders, and coke breeze. This group of lightweight materials, with the exception of slag, has become less significant and will not be discussed in this chapter. Other lightweight aggregates are beginning to appear in the marketplace. Some are the result of manufacturing processes on industrial byproducts and/or waste products, such as fly ash and incinerator residue (Bigner, 1992). 4. Manufactured Insulating Ultralightweight Aggregates-pre- pared by pyroprocessing ground vermiculite, perlite, and diatomite. The application of diatomite in brick and in extruded and aggregate forms has declined in recent years (Kadey, 1983) and will not be considered in this chapter. Lightweight aggregates for structural concrete and concrete masonry units, according to the American Society for Testing and Materials (1986) consist of "aggregates of low density used to produce lightweight concrete, including: pumice, scoria, volcanic cinders, tuff and diatomite; expanded shale, clay, slate, perlite, vermiculite or slag; and end products of coal or coal combustion" (Mason, 1989). Lightweight aggregates are distinguished from other mineral aggregate materials by their lighter unit weights-1 281 to 1 602 kg/m3 or less for loosely packed lightweight aggregates-as com- pared to 2 002 kg/m3 or more for crushed stone, sand, gravel, air-cooled slag, and other common mineral aggregates. The specific gravities of these lightweight aggregates are also used to classify them for use in concrete; they range from the extremely light materials, used for insulative and non-structural concrete to expanded shale, clay, slate, and slags used for structural concrete. Vermiculite and perlite are sometimes referred to as super light- weights. Insulating concrete (non-load bearing) weighing as little as 240 kg/m3 can be made with these aggregates. Natural aggregates such as pumice, pumicite, and scoria are normally made into concrete weighing about 400 to 480 kg/m3. Expanded shale, clay, and slate produced in a rotary kiln make structural concrete ranging from 1 201 to 1 842 kg/m3. Expanded shale and clay produced by sintering make concrete that ranges from 1 442 to 1 922 kg/m3. Air-cooled slag produces concrete ranging from 2 162 to 2 403 kg/m3. The low density lightweight aggregates are used primarily for insulating purposes. They have relatively low compressive strength. The middle density aggregates are used for insulation and for fill. Those at the upper end develop excellent compressive strength and are used in many structural applications (Anon., 1971). In recent years, the production of lightweight aggregates in the United States for all uses (including insulation and construction materials) has averaged about 19 Mtpy (Table 1). The production and consumption of lightweight aggregate is closely tied to the fortunes of the construction industry and the need to construct energy efficient buildings. Recent years have seen the production of lightweight aggregate approach the levels of the early 1970s. The period of 1979 to 1981 was a low point in production levels. The low levels of production were caused by significantly higher plant energy costs due to the large amounts of fuel and energy used in the production of most types of lightweight aggregate. Lower levels of construction activity also affect production levels. This chapter focuses on the use of natural lightweight aggregates and manufactured insulating ultralightweight aggregates, and on both the production and use of manufactured structural light- weight aggregates. Some additional comments are made on byproduct materials. Separate commodity chapters on vermiculite, perlite, pumice, and volcanic cinders are elsewhere in the volume. Discussion of the commodities covered elsewhere in the book will be limited to observations on their utilization and relation to other lightweight aggregate materials.

Jan 1, 1994

By Surendra K. Mishra

Recent land ban act has put pressure on industry to decontaminate the waste streams before they could be discharged. However, for both metal and organic contaminated wastes, there are commercial incentives to recover usable resources. Recent technology developments have helped meeting such objectives. This paper reviews developments in treatment technologies for industrial wastes. Major chemical groups used in waste treatment are summarized.

Jan 1, 1994

By James M. Barker, Richard O. Y. Breese

The recognition of perlite as a distinct volcanic glass, and of the arcuate fractures that often characterize these natural glasses, dates back at least to the late 19th century and perhaps into the 18th century (Howell, 1974). Some authors suggest that recognition of perlite dates considerably further into antiquity, perhaps to the 3rd century BC (Caley and Richards, 1956). Most recent definitions identify perlite by the presence of vit¬reous, pearly luster and by the presence of characteristic concentric or arcuate perlitic fractures. As discussed more fully below, arcuate fractures in perlite need not be megascopic. The textures of perlite which commonly occur in deposits range from dense to highly vesiculated to pumice-like. Thus, the classical definition of perlite is descriptively restrictive compared to the natural range of textures and neglects to address the issues of genetic origin and geologic occurrence. In spite of the petrological usage of the term perlite, the in¬troduction of expanded perlite aggregate into industrial markets caused the term to be applied as well to the lightweight, cellular aggregate that is produced through the rapid thermal expansion of milled perlite ore. Perlite is distinguished petrologically from other natural glasses by a silicic or rhyolitic composition by the presence of 2 to 5 wt% total chemical water held within the glass structure and often by the presence of pearly luster and onionskin-like perlitic fractures. Worldwide, occurrences are associated with Tertiary through early to middle Quaternary volcanics and with the glassy portions of silicic domes and flows, with vitric tephra, with the glassy chill margins of dikes and sills, and with the glassy portions of welded ash flow tuffs. Less commonly, perlite is reported in association with the glassy portions of volcanic plugs and lacco¬liths. The perlite carapaces that partially or fully comprise extru¬sive domes and flows are often thick and areally extensive, and thus provide commercially attractive targets for low cost open pit mining. Perlite tuffs and tephras are also important commercial sources. Mining costs are minimized by open pit quarrying and by either bulldozer ripping or blasting. Crushing and sizing facilities are generally close to the pits. Due to the low weight and large volume of expanded perlite, unexpanded perlite that has been crushed and sized is usually shipped nationwide directly to local markets where it is expanded and processed for distribution to end users. The vast majority of international trade is in unexpanded perlite. In the United States, the evolution of the expanded perlite industry can be traced to the late 1930s and early 1940s when expanded perlite aggregate was introduced into gypsum plaster and concrete markets as a substitute for vermiculite (Schundler, Jr., oral communication, 1991) and was promoted for use in a much broader spectrum of products (Howell, 1974). By the early 1950s, end user markets were well established and small expanders were numerous east of the Mississippi River. Today, mining and expan¬sion is undertaken throughout the world. Worldwide production of perlite is dominated by the former Soviet republics, the United States, and Greece. Total worldwide production of processed perlite during 1990 is estimated at roughly 1 778 000 tons (Davis, 1991). The physical properties of expanded perlite that give this prod¬uct unique commercial value include: low bulk density, chemical inertness, high insulating ability, nonflammability and fire resis¬tance, and its ability to retain water. These and other physical properties give expanded perlite value in such uses as: lightweight acoustical and thermal insulating aggregate; component in plaster, insulating cements and lightweight concrete; loose fill insulation; as aggregate in horticultural applications; and in milled form as filter aid. In the United States and Europe, the largest end use is within building construction products.

Jan 1, 1994

By O. Ozcan

Oleic acid has been almost invariably used in the flotation of siliceous fluorite ores. The performance of oleic acid, however, deteriorates with carbonaceous fluorite ores. Oleoyl sarcosine developed recently has been found to produce results superior over oleic acid with ores containing high calcite contents. While the mechanism of oleate adsorption is usually considered as chemisorption involving calcium oleate formation on both calcite and fluorite, no mechanism has been so far proposed to explain the adsorption mechanism of oleoyl sarcosine. In this study, the selectivity of oleoyl sarcosine, as inferred from flotation, zeta potential and infrared measurements, is ascribed to the interaction of fluorine ion to the nitrogen via hydrogen bonding.

Jan 1, 1994

By William E. Cutcliffe, John A. Ames, John D. MacFadyen

Webster's dictionary nearly equates portland cement with its current primary definition of cement. Although such equation may be a triumph of common usage, the confusion between the terms cement and concrete unfortunately is very widespread. Full definition of cement properly would extend to many substances, but for purposes of this chapter cement is restricted to varieties of portland cement including portland-pozzolan cement. Among the usually recited historical notes concerning cement is that it was developed by the Romans. Their use of cement in the great structures of Rome, and even in the far comers of their Empire, such as Hadrian's Wall in the north of England, testifies to the antiquity of a major cement industry. From English sources we know of John Smeaton's carefully proportioned hydraulic cement mixed in 1756 and of Joseph Aspdin's patented cement to which, in 1824, he gave the name portland cement. (He claimed that his cement mortar looked like the famous dimension limestone quarried from the Isle of Portland on England's south coast.) The year 1971 marked the centennial of portland cement manufacture in the United States. A fair historical account of the many real contributors to the cement industry since 1756 unfortunately would be too extensive for this chapter. Development of rotary kiln practice and burning at higher temperatures clearly was the major move into today's technology. Cement manufacture is the processing of selected and prepared mineral raw materials to produce the synthetic, mineral mixture (clinker) that can be ground to a powder having the specified chemical composition and physical properties of cement. Cement making incorporates a number of distinct steps, but it is characterized by the key pyroprocessing (or burning) step, which brings about the necessary changes in the raw materials. This pyroprocessing is a chemical process. Conversion of large volumes of mineral raw materials into specification-controlled cement at relatively low cost is the objective. Statistics on the cement industry are of uneven quality. The US Bureau of Mines (USBM) is the principal collector of available data. These statistics can be only as good as the quality of information supplied by the reporting companies. The data perhaps most often questioned relates to productive capacity of the industry. The questions submitted by USBM are valid, nevertheless, and the information gained from them, as good as is available, is what is generally used. The Portland Cement Association also is a source of much quality information. In analyzing cement industry production rates, it is well to keep in mind that measurement of raw materials requires the reader to recognize that approximately 1.6 t of dry raw materials are required to make 1 t of clinker. This number can vary depending on the amount of kiln dust wasted. Also that to produce 1 t of portland cement required .94 to .96 t of clinker, the remainder being gypsum or anhydrite. A ton of masonry cement or pozzolanic cement re- quires considerably less clinker.

Jan 1, 1994

By Randall M. Wheeler

It is important to be able to quantify the effects of blast delay designs on vibration characteristics. White was the first company to develop commercially available software, called Alpha-Blast, for this purpose. The program can indicate relative amplitude and frequency results to be expected from the use of particular delay intervals. If enhanced vibration effects from delays are a problem, a technique to evaluate this situation will be invaluable.

Jan 1, 1994

Improve the dust-control effectiveness of the Rotoclone1 dry-dust collection systems used on surface coal mine drills.

Jan 1, 1994

By Richard D. Christie, K. Jay Pillai

In the past, it was not unusual for coal preparation plants to discard fine run-of-mine coal. This practice has changed due to increasing quantities of fine material, improvements in beneficiation methods, and the need to recover revenue from these fines. It is in this context that the coal industry has increasingly been turning to froth flotation for fine coal beneficiation. Reagent schemes have been developed to promote coal flotation and to treat the resulting refuse material. While reagent technology has improved, however, most plants rely on manual control of reagent dosing and circuit operation. This often results in misuse of reagents, loss of coal recovery, and consequent loss of revenue. Fine coal circuit operations can be dramatically improved through automation. Intelligent process control systems are now in use which are capable of optimizing reagent usage, maximizing coal recovery, and minimizing chemical costs associated with refuse handling. This paper describes a type of control system currently used in preparation plants, and provides data and information on the significant improvements such systems can produce.

Jan 1, 1994

By Rick W. Bellenie, Ronald L. Woolf

The Gregg River mine is located 40 kilometres (25 miles) south of Hinton, Alberta, approximately 330 kilometres (205 miles) west of Edmonton and lies against the Front Range of the Rocky Mountains.

Jan 1, 1994

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

By Harold A. Taylor

The first use of graphite is lost in the mists of time. It was used by primitive man to make drawings on the walls of caves and by the Egyptians to decorate pottery. As early as 1400 AD graphite crucibles were being made in the Haffnerzell District of Bavaria. Through the Middle Ages graphite was confused with other minerals, especially galena and molybdenite. Two common names that are still being used for the mineral are plumbago, meaning lead-silver, and black lead. The latter name implied that graphite is either composed of lead or at least contains a large percentage of it. Gessner is credited with having recognized it as a separate mineral in 1565, but its composition was not determined until 1779, when Scheele demonstrated that graphite oxidized to carbon dioxide, thus proving its carbon constitution. In 1789, Werner named it graphite from the Greek word graphein, meaning to write. The United States has long relied on foreign countries for its graphite supplies. This reliance has been due more to the lack of suitable domestic graphites than to any particular preference for buying minerals overseas. Sri Lankan graphites were imported as early as 1820, and Madagascar graphites have been imported since the properties on that island were opened up about a hundred years later. Mexico has long supplied the United States with most of its requirements for amorphous graphite.

Jan 1, 1994

By Lu Jun

Up to now, much data on marine minerals, as well as on marine geochemistry, have been accumulated. Modem computer databases provide optimum flexibility and power for manipulating these data. The best worldwide marine mineral database is currently the Marine Minerals Bibliography and Geochemical Data Base created by Carla Moore et al. at the National Geophysical Data Center in the United States. In fact, in the course of studying marine minerals and geochemistry we may collect not only digital-character type data but also graph and image (black-white, grey and color image) data types. For instance, correlation diagram between chemical compositions of minerals, spectroscopic graphs, (e.g. infrared spectra, Mossbauer spectra, etc.), grey or color images from both optical and electron micro- scopes (scanning or transmission electron microscopes) as well as seabed photographs. Charles L. Morgan et al. (1993) reported that 10,000 photographs and some video images of the seabed in the Clarion-Clipperton region of the northeastern tropical Pacific have been collected by the Ocean Minerals Company. If both graphic and analytical information were stored in a database, it would be very useful and convenient to marine geologists. This system would not only be able to search for all the data based on one parameter, but also for both size and composition distributions. If possible, geostatistical methods could be combined with fractal dimensional methods. Of course, this would require enormous efforts. Before multimedia technology emerged, it was very difficult to create image databases. The emergence of large-capacity compact discs, high-speed central processing units, and high-speed digital signal processing techniques makes it possible to establish multimedia database management systems (DBMS), image-text DBMS, that involves graphs, text, images, and sound. In order to store image fields in a DBMS, we have to take into account two problems: (1) image access format and (2) image compression code standard.

Jan 1, 1994

By J. E. Gebhardt, J. A. Herbst, K. Y. Lee

Benefits of proper control of reagent usage in flotation circuits are typically improved metallurgy and savings in reagent costs. Improved metallurgy can mean more consistent product quality, i.e., final concentrate grade, better recovery of product values from the feed, or higher plant throughput at existing target recovery, and grade values. Flotation performance is sensitive to a variety of process disturbances which occur in operating plants, such as changes in flow rate, percent solids, size distribution. flotability of mineral species, etc. A way to handle these variations is to fully understand the dynamic flotation responses to disturbances and to implement a suitable control strategy to compensate for these disturbances. Depending on the objectives of the control system, various types of control strategies are available which employ different levels of refinement to achieve the desired performance. Typically, variables such as collector and frother dosages and reagent addition points can be manipulated to affect the performance of the circuit. In the case of sulflde mineral flotation, manipulation of the process electrochemical potential, in flotation and in grinding, offers another degree of process control. Because of the complex and interactive nature of flotation process variables, optimized reagent control requires consideration of all, or at least the most important, interactive variables of the flotation circuit. Model- based optimizing control provides a framework to handle the complex and dynamic nature of flotation reagent process control.

Jan 1, 1994

By David A. Bacca

Hydraulically powered submersible borehole dewatering pumps and emulsion/ANFO blends evolved at about the same time and for the same reasons. Mining operators needed safe, efficient dewatering systems and water resistant products.

Jan 1, 1994

By Lindbeck K

The mining industry in Western Australia is a large sector of the WA economy providing $12 billion (1993) of the export income for the State. Historically, mining in WA developed from traditional prospecting in the late-1880s leading to major underground operations by the turn of the century. Large open pits were developed in WA following World War II and became increasingly common since the gold boom of the 1980s. With the development of the open pits has been concomitant evolution of mining legislation, principally the Mining Acts of 1904 and 1978, which has been also accompanied by a practical evolution of the administrative system within the Department of Minerals and Energy. The mining industry has recognised the need for sound environmental management at mine sites, taking up the challenge and becoming a world leader in rehabilitation techniques. Any environmental management program in the industry has three stages: approval by government; management by the industry; and return to the State in an environmentally acceptable condition. The WA environmental requirements, procedures and industry performance in these three stages are discussed.

Jan 1, 1994

Thank you for asking me to address you. The topic may sound formidable. Those of you with determination to go somewhere in your careers will understand that by taking geoscience, mining and metallurgy courses as students, you are declaring your intere

Jan 1, 1994

By P. Müller, W. J. Przybylowicz, V. M. Prozesky, D. de Bruin

"Abstract -The common style of gold mineralization in the Basal Reef and other auriferous conglomerates of the Witwatersrand Supergroup comprises clusters of gold grains occurring interstitially to quartz and pyrite pebbles as well as gold accumulations attached to the surface of and infilling hairline cracks and fractures in round, compact, detrital pyrite. The latter textural association is generally interpreted as a result of remobilization of originally detrital gold during regional metamorphism and related hydrothermal fluid circulation. There is general agreement that, although gold solubility was Iow, ore modification occurred during the metahydrothermal event, but uncertainty exists about the magnitude and scale of gold remobilization .Micro-textural and chemical investigation of compact round pyrite and associated gold accumulation has established that gold is preferentially deposited on chemically heterogeneous pyrite surfaces. Combinations of alternating high- and low-As zones in pyrite result in mixed np-type conductivity accompanied by electron exchange and the reduction-driven deposition of gold at the cathode. This mode] does not explain gold accumulations which are not immediately linked to chemical heterogeneities and it is inferred that an additional control on the deposition of gold was exerted by physical defects which lead to zones of increased charge density and/or areas of focussed conductivity. The inferred precipitation mechanisms suggest that submicrocopic physical and chemical controls are the important factors that determined the sites of gold nucleation and that precipitation mechanisms based on physicochemical changes of the hydrothermal system were not involved. The Basal Reef contains on average close to 5% of round, detrital, chemically zoned pyrite which provides a large number of electrochemically active pyrite surfaces. The extremely effective electrochemical precipitation mechanism together with the low solubility of gold in Witwatersrand fluids is the main reason for the spatially restricted remobilization of gold in the conglomerate reefs."

Jan 1, 1994

By Thomas O. Llewellyn

This U.S. Bureau of Mines (USBM) report presents a concise review on sources, processes, supply, and historical use patterns of domestic cadmium. It also covers a preliminary estimated cadmium material flow for the year 1989. This preliminary study contains information on cadmium and cadmium-bearing products in the United States. The data in this report were obtained from both published and/or unpublished sources of information. However, in order to estimate the fate of cadmium in each operation or application stage, some assumptions, judgments, and correlations were made by the USBM in an attempt to determine the material flows losses.

Jan 1, 1994

Incidental to the progress of a geological survey of the Kalgoorlie goldfield during 1927 - 1928 a number of specimens of telluride minerals were obtained, chiefly with the help of Mr F G Brinsden, general manager of the South Kalgoorlie mine, and Mr Ernest Williams, general manager of the Boulder Perseverance mine. This collection was supplemented by a number of small specimens, including the rare copper telluride, which were collected and preserved from the Kalgoorlie mine by Mr A E Paton, and also by a few miscellaneous specimens from the collection of MrS F C Cook, of the Palace Hotel, Kalgoorlie.An extensive knowledge of the rare tellurium-bearing minerals was compiled during the last century from occurrences in Transylvania and Colorado. The recognition of different species has been based on chemical analyses and crystallographic measurements. In a few species there has been an absence of crystalline form, and these, together with the discoveries in this century of rickardite and 'weissite', muthmannite and empressite, have depended chiefly on the chemical analysis for identification. On the other hand, the crystalline form of nagyagite and stiitzite has been described in detail, while their precise chemical formulae were doubtfully defined.The announcement of the occurrence of tellurides at Kalgoorlie by A G Holroyd in the Kalgoorlie Mine on 29 May 1896, followed by their discovery in comparative abundance, stimulated the further study of these minerals. In this locality there is a general absence of well-formed crystals, and the knowledge gained has been confined to the record and description of previously known, but exceedingly rare, species.No new species has been recorded, but the intimate association of various species resulted in early description of two supposedly new species, kalgoorlite and coolgardite. These have been discredited since the investigation by L J Spencer in 1903, based on a collection of specimens donated to the British Museum.Spencer's list of species at Kalgoorlie comprises calaverite, sylvanite (or krennnerite), petzite, coloradoite, 'and altaite, and does not include hessite, previously mentioned by Krusch. In 1912 melonite and a copper telluride were added by J A Thomson and the presence of hessite confirmed. In 1912 there also appeared a full and detailed account by E S Simpson on behalf of the WA Geological Survey, which embraced his earlier notes on the tellurides, and which represents the state of our knowledge of the Kalgoorlie minerals, practically as far as can be attained without the use of the reflecting microscope.The position has been stationary for about 18 years, and it was thought. that the best use to which the present collection of tellurides could be devoted was an attempt by mineragraphic methods to study the mineral relationships, not only of the tellurides among themselves, but also to gold and other associated minerals. The precise mineral content and relationships become a factor of added importance with the development of flotation methods of treatment at Kalgoorlie.Moreover, the study would supplement the description of the ore deposits of the Boulder Belt that has recently been published.

Jan 1, 1994

By M. Niinae, Y. Nakahiro, T. Wakamatsu

In some cases, the extraction and separation efficiency of metals with a combined extractant are better than those with either extractant alone. However, the extraction and separation efficiency of metals with a combined extractant are not always better than those with either extractant alone. As part of the fundamental studies on the extraction and separation of metals with combined extractants, the extraction and separation efficiency of Au and Fe(III) added as an oxidizer in the leaching of Au from a sulphuric acid solution containing thiourea, and the extraction and separation efficiency of Nd and Sm from hydrochloric acid and sulphuric acid solutions were examined. The combined extractants for Au and Fe(III) were di(2-ethylhexyl) phosphosphoric acid (D2EHPA)/tri-n-butyl phosphate (TBP), D2EHPA/trioctyl phosphine oxide (TOPO). tri-n-octylamine (TOA)/TBP and TOA/TOPO, and those for Nd and Sm were D2EHPA/TOA. D2EHPA/TOPO. 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA)/TOA and EHPNA/TOPO

Jan 1, 1994