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By Kristen E. Coose

Concrete is a mixture of a fine aggregate (sand), a coarse aggregate (gravel), cement, and water. Cement itself is the most expensive of the ingredients but generally amounts to only about 10% of the concrete mixture. Cement raw materials include calcium, alumina, iron oxide, silica, and gypsum. They are heated and chemically changed into clinker "minerals," which are then ground and shipped as cement. Each of the four main clinker minerals-tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite-impart specific strength and compositional properties to the final concrete product. During hydration of the cement, chemical changes produce new minerals that include calcium silicate hydrate gel (C-S-H, the main constituent of hydrated cement paste), calcium hydroxide, and calcium, sodium, potassium, and sulfate ions, among others. Two main reactions can occur that may be deleterious to concrete. Normal cement pore solutions, in a hydrated cement, contain sodium hydroxide and potassium hydroxide. If these alkali concentrations are too high, they can react with the siliceous aggregate (alkali-silica reaction, or ASR) to form an alkali-rich calcium silicate hydrate gel (C-N+K-S-H), which, upon prolonged contact with water, can expand to crack the concrete. The other deleterious reaction occurs when the mineral ettringite (Ca6A12(S04)3OH12. 26H20) forms after the concrete is hardened (delayed ettringite formation) and cracks the concrete. Many of the concrete bridges and structures built in New Mexico in the past 20 years are in need of replacement due to deterioration. Many others constructed very early on in the century are still sound. By collecting and analyzing samples of both old and new concrete and good and bad concrete, we compared their differences on both a microscopic and macroscopic scale. Samples taken from concrete sidewalks, parking lots, drainage canals, spillways, and a railroad-trestle foundation have construction dates that range from 1923 to 1997. They were analyzed by electron microprobe and by petrographic microscopy. Cracks, air voids, and aggregate alteration were primary locations for investigation and analysis. Using the electron microprobe, ettringite was found in voids of most of the samples, both in good and bad concrete. This leads us to believe that ettringite formation is not causing distress in the concrete. There was one exception in which ettringite was found lining a crack. In this instance, ettringite may have the ability to further the cracking and cause distress. No alkali-silica gel was identified with the microprobe. Using the petrographic microscope in cross-polarized light, a light-brown material was observed that lined some of the air voids and cracks; however, exact mineralogic identifications were not made. Although many instances of chalcedony and other deleterious quartz phases were found, no clear evidence of ASR-gel deterioration was present in our samples using these methods. However, positive identification of the ASR gel was made on an in-place concrete near one of our sample sites and in several sample cores using a newly developed chemical test for the soluble potassium ions associated with the gel. The chemical used in this test is sodium cobaltinitrite, Na3Co(NO2)6.

Jan 1, 1999

By John R. Hoskins

The Bureau of Mines conducted an investigation to more exactly define the influence of some end conditions on the laboratory-determined uniaxial compressive strength of rock samples. Limestone, marble, sandstone, and granite were used to provide a range of specimen modulus of elasticity from 2.7 X 106 psi to 10 x 106 psi. Four variables were studied: Nonparallelism and surface texture of specimen ends were the specimen variables investigated; the end platen size and the adjustable or spherical head friction were the machine variables studied. It was concluded that the loading ends of small laboratory models and samples should be prepared with surface irregularities that do not vary from a plane surface by more than 0.001 inch. It was also concluded that nonparallelism of the specimen ends should not exceed 8 minutes for a rigid head load or 15 minutes for an adjusting head load. The measured compressive strength of specimens prepared with these tolerances will be statistically the same with any diameter or thickness of platen and any degree of head friction if initial alinement of the specimen is assured.

Jan 1, 1968

By J M. Gibbs

Craigmont Mines Limited mine 50,000 tons of ore and waste per day from the open pit at Merritt, British Columbia. An electric-powered "down-the-hole" drill, a diesel-powered rotary drill and two electric-powered rotary drills have been used. All primary drilling, as a result of cost and operating experience, is now performed with two electric-powered rotary drills. Trials with various loading techniques have increased the amount of AN-FO and decreased the amount of commercially prepared slurries used for primary blasting. Approximately 95 per cent of the primary blasting is accomplished with AN -FO, mixed at the hole. Introduction THE Craigmont mine is located near the village of Merritt, B.C., 240 miles northeast of Vancouver. The concentrator has been in production since September of 1961. Craigmont is a combined open-pit and underground operation. To date, slightly more than 95 per cent of the mill feed has been mined from the open pit. As underground development proceeds, the ore requirements from the open pit will decrease. The average milling rate from September, 1961, to April, 1964, was approximately 4,900 tons per day.

Jan 1, 1965

By Fredrick L. Johnson

The Bureau of Mines, under Congressional mandate, conducted a mineral survey on the Park Range WSA (Wilderness Study Area) in 1984 and 1985. The WSA, located about midway between Tonopah and Ely, encompasses 47,268 acres. No mineral resources were delineated, nor were workings found, during the investigation. There has been, however, exploration in and near the north end of the study area. ASARCO is actively exploring a block of 41 claims for hot-spring type, low-grade, large-tonnage gold deposits. Their claim block is almost entirely in the study area. The Morey mining district, 7 miles southwest of the study area, produced silver and lesser amounts of gold and lead sporadically from the mid-1860's through the mid-1960's. The WSA is underlain by Tertiary rhyolitic and latitic volcanic rocks and by Paleozoic sedimentary rocks. The Paleozoic rocks have been faulted, silicified, brecciated, and hydrothermally altered, and have anomalous concentrations of precious metals and pathfinder elements. Additional exploration in the north part of the Park Range WSA may lead to delineation of gold resources.

Jan 1, 1986

By H. -F. Krausse

Roof failures in underground coal mines are related to the lithology and geologic structure of the roof. There are two distinct suites of roof rock above the Herrin (No. 6) Coal in Illinois, and each has distinctive patterns of structure and roof failure. In black shale-limestone roof areas, roof instability is correlated with thinning of limestone beds and presence of faults and clay dikes. In gray shale roof regions, the prime roof hazards are posed by rolls, shear bodies, and presence of coal or carbonaceous partings in the roof. Most structural features examined are believed to have formed during early stages of sediment diagenesis and compaction. Structural trends and lithologic patterns are strongly interdependent for this reason. In many cases geologic patterns are so complex and locally variable that prediction of roof stability far in advance of mining is difficult. The need for greater flexibility in roof control planning is apparent.

Jan 1, 1979

By R. Gallinger, B. Kelley

"In 1997, a group of Canadian mining companies met to review the Mine Environment Neutral Drainage (MEND) program and to consider future activities. They concluded that (1) that Canadian industry and Natural Resources Canada (NRCan) should fund a small secretariat in Ottawa to support technology transfer in Canada and, (2) that it was important for industry to continue the momentum of MEND on an international scale.The need for the International Network for Acid Prevention (INAP) was strongly endorsed by consultants, company, university, and government experts from Australia, Canada, and the United States who convened in Vancouver in February 1998. The initial focus was the development of a solid knowledge base covering the collective experience of INAP’s members to promote the dissemination of successful practices, the identification of knowledge gaps, and the formulation of effective research proposals. The sharing of information on past successes and failures alone was viewed assufficient justification for the formation of INAP.INAP was officially launched in October 1998, and is now an effective, industry-based initiative to globally coordinate research and development in the management of sulphide mine waste. Significant improvements in the management of sulphidic mine materials through knowledge sharing, research, and development of technology by INAP will reduce liability associated with acid drainage.This paper will explore the international efforts and activities of INAP."

Jan 1, 2005

By R. Dippenaar

The emergence of new steel grades is largely driven by the need to produce high quality steel at a competitive price. The principal aims are to attain ultra-high purity, (especially low interstitial elements) and ultra-cleanliness (by the control of the inclusion content and size). Whereas the steel used to build the Titanic contained 650 ppm sulphur, resulting in MnS stringer-inclusions 25 mm in length, modern quality requirements for arctic pipelines would only allow 10 ppm of sulphur and inclusions in ball-bearing steels must be smaller than 5µm. Most developments are aimed at hot-metal treatment before refining and ladle treatment after decarburisation. Because ferroalloys are added during or after the refining step, it is the secondary (ladle) refining production technologies that are of specific interest to the ferroalloy producer. Through ladle treatment, hydrogen and nitrogen contents are reduced, ultra-low levels of solute impurities are attained and the shapes as well as the composition of inclusions are modified. Steelmakers are concerned about the cost effectiveness of the use of ferroalloys such as consistent product analysis and delivery, improved financing arrangements and technical support. Minimal variation in product sizing is vital because it impacts on handling problems and because particle size determines the rate of particle dissolution. The required ferroalloy product quality depends on the specific use but in general sulphur, phosphorous and nitrogen contents are of concern. Apart from the presence of trace and impurity elements, ferroalloys also contain inclusions. For example, ferromanganese may contain MnO-MnS-SiO2 inclusions while high-carbon ferro-chrome may contain different kinds of Cr-Mn-spinels. The presence of these impurities and inclusions has a significant impact on steel production techniques and cost and hence, on the selection and use of ferroalloys. The interrelationship between ferroalloy quality and steel production technology is plant and product specific and hence, effective communication between ferroalloy suppliers and steel producers is essential.

Jan 1, 2004

By J. S. Harington

Our purpose is to record and to explain the widely changing numbers of the huge total of black workers on the gold mines of South Africa over the century from 1896 to 1996. These men were recruited from up to twenty territories, and their contributions are examined. The major areas providing labour over this long period have been Lesotho, the former Transkei within South Africa and Mozambique. From 1989 to 1996, for instance, these three areas accounted for over sixty per cent of the total labour force (tlf). Our principal Figure 1 shows the tlf fluctuating through time to reach a peak of 480 000 in 1988. Irregular falls are also documented with the most serious in 1995 to 180 000. Based on this graph we consider the political, economic, sociological and historical reasons behind these changing employment opportunities. These have included external world-scale events such as war or depression, as well as internal changes of national economy and policy. We show the importance for numbers employed of the discovery of gold in the Orange Free State in 1946, the influence generally of the ?Winds of Change? and the firm maintenance by the State of law and order. Varying gold production costs and profitability against high tax rates, allied with increasing wages and a lack of development capital, have led in the last decade to employment falling by fifty per cent, despite an actually higher value of gold output. Finally, this analysis considers the role of the migrant labour system as it affects, and is affected by, conditions in the gold mining industry, with special reference to its less than humane consequences in the numerically dominant territories of Lesotho and Transkei.

Jan 1, 2004

By P K. Smith, R J. Ryan, W R. H Ramsay, D C. Arne, F P. Bierlein

Turbidite-hosted, mesothermal lode gold deposits in Paleozoic metasedimentary rocks of the Buller Terrane, western South Island have a similar geological history and genesis to the Paleozoic lode gold deposits ofVictoria, Australia and Nova Scotia, Canada. In all three regions the gold deposits are hosted by interbedded meta-sandstone and meta-argillite that have been folded and regionally metamorphosed to greenschist facies, and locally in Nova Scotia to amphibolite facies. The gold deposits are typically narrow, structurally controlled quartz veins associated with dilatant zones in reverse faults or fold-related fractures. The principal vein types include: bedding parallel or concordant veins, discordant veins, saddle reefs, and stockwork veins. En-echelon and "ac" type veins are sometimes also gold-bearing in Nova Scotia. The contrasting competency of the host meta-argillite and meta-sandstone beds is an important factor in vein formation, particularly for the bedding parallel veins, which are typically developed within meta-argillite beds or along the contacts between meta-argillite and meta-sandstone. Veins found within meta-sandstone units are generally discordant. The deposits in Victoria are well known for their bedding-parallel veins, saddle reefs ( Bendigo ) and leather jacket reefs (Ballarat). Bedding-parallel veins are also common in Nova Scotia , along with a few examples of saddle reefs. In contrast, vein formation probably occurred later in the deformation history of the Reefton and Lyell goldfields, with most veins being bedding discordant and more typically aligned with the axial plane cleavage of the folds rather than bedding planes. The quartz lodes in one deposit, Globe-Progress, strike approximately perpendicular to the bedding and fold axes. No saddle reefs have been recorded from the Buller Terrane. Mesothermal vein morphology reflects the amount of fmite strain, the strain rate, competency contrasts, lithotypes, and the confirming pressures to which the system was exposed. On the basis of comparable depositional depths and rheologies of the host rocks, a controlling factor influencing the development of different vein styles (and timing) might be finite strain, as exemplified by the tightness of folding in the host rocks. Folding appears to be tighter in the Victorian rocks than in either the Buller Terrane or Nova Scotian rocks.

Jan 1, 1999

The National Institute for Occupational Safety and Health (NIOSH) conducted a monitoring field study to optimize the rib control plan in a room-and-pillar coal mine. The study mine is located in the Central Appalachia coal basin. Two monitoring sites were selected at different sections in the study mine. The selected sites have different overburden depths and geologies. The instrumentation plans at study sites include borehole pressure cells installed at various depths in studied pillars, rib and roof extensometers and load cells mounted on number of the rib bolts. The instrumentation results and observed geology for one of the study sites showed great potential for optimizing the rib bolt plan at that section of the mine. Therefore, a rib support optimization study was followed using numerical modeling technique. A calibrated threedimensional model was developed using the instrumentation results of the optimization section. The calibrated model was used to determine the optimum rib support for expected overburden depths and rib heights. Baseline rib bolt patterns were assumed for the optimization study. Additional rib bolts, above and beyond the baseline bolting parameters, were outlined and identified as solutions to contain the rib fracturing identified by the modeling results.

Jul 28, 2020

The increased focus on best practice environmental management has led to mining and mineral processing companies developing a variety of procedures to ensure that the environmental impacts of their operations are minimised, and that company managements are fully aware of these impacts and the policies and procedures established to ensure this process. Parallel to this, international standards for the development and implementation of environmental management systems are being promoted as necessary for companies to demonstrate their due diligence. Good environmental management systems should be built upon the systems already established within companies, and should ensure that the process of continual improvement is integral to their operation. An outline of the basic components of environmental management systems is provided, along with examples of the way various mining companies have implemented such systems. The benefits of best practice environmental management to mining companies are also considered.

Jan 1, 1995

By G. Smith

This paper describes the allure of diamonds over time and highlights the magic and mystery of famous diamonds. Consideration is given to the effectiveness of marketing in the diamond industry. It is concluded that diamonds are held as cherished possessions, valued far above their real market price, retained as valued heirlooms, and widely used as a form of highly liquid currency. In order to sustain value, both from an investment and jewellery perspective, demand has been stimulated to keep pace with growing global supply while the illusion that ?diamonds are forever? has been fostered to ensure that most diamonds, once sold, do not re-enter the market.

Jan 1, 2003

By Richard J. Mainiero

The Bureau of Mines has developed a prototype nonincendive explosive rock-breaker charge that can be fired unconfined in underground bituminous coal mines without the danger of igniting a flammable atmosphere that might be present. At present, unconfined shooting in underground coal mines is prohibited, but there are situations where the use of such shots would yield an overall improvement in safety. The charge consists of l-1/2 lb of permissible water gel explosive in the form of a short cylinder 7 inches in diameter and 7/8 inches high, surrounded by a l/2-inch-thick layer of damp salt, and encased in latex rubber reinforced with cheese cloth. The latex rubber housing provides a charge package that is strong enough to resist rough handling yet is pliable enough to conform to an irregular stone surface. A charge of this shape was found to be more effective at breaking rock than charges with lined or unlined cavities. Incendivity tests in a gallery have shown that the prototype charge will not ignite a flammable methane-air atmosphere when fired. Rock- breaking tests made with limestone boulders indicate that the charge will satisfactorily break stone slabs weighing 1 to 2 tons, and that two or more charges might be effective for slabs weighing up to 10 tons. In cooperation with the Mine Safety and Health Administration (MSHA), a test protocol for the certification of these charges as "permissible" for use in flammable atmospheres is being developed.

Apr 1, 1982

By J. D. Ramsdell

To obtain information on the effects of cobalt on microstructure and tensile properties of titanium-vanadium-cobalt alloys, the composition ranges of 4 to 16 percent vanadium with 1 to 4 percent cobalt have been studied. The beta phase was not completely retained with vanadium additions up to 16 weight-percent or in the same alloys containing up to 4 percent cobalt.

Jan 1, 1960

The Bureau of Mines has sponsored a comprehensive research program to enhance the safe, effective, and efficient use of blasting technology by the mining industry. Recent research results of the surface mine blasting program were presented at a seminar on April 25, 1987, in Chicago, IL. Many of the topics discussed at the seminar are presented in this proceedings. The new research described in these papers includes computer monitoring of rock motion, the influence of blast delay times on rock fragmentation, blasting effects on Appalachian water wells, blast vibration measurement near structures, and the reduction of accidents through improved blasting safety.

Jan 1, 1987

By D. Ng

A facility to evaluate the fire endurance of mine stoppings was constructed by the Bureau of Mines in the multiple entry section of the Bruceton (PA) Experimental Mine. Stoppings up to 6 by 18 ft can be tested in a manner simulating mine conditions. The stopping is subjected to a 70-min liquid fuel tray fire with an energy output of 75,000 Btu/min. The stopping and adjacent areas are instrumented with thermocouples and heat flux gauges. Data acquisition is by an automatic data logger capable of continuously recording over 100 channels of information. Two 8-in-thick concrete block stoppings and a galvanized steel stopping were tested. A crack developed on the fire side surface of the block stoppings where the flames were most intense. However, the temperatures of the unexposed surfaces of the stoppings never exceeded 800 C and the surfaces were undamaged. The steel stopping retained its structural integrity during the test. The temperature of the unexposed steel surface reached 5000 C, but combustible materials located 1 ft from the surface did not ignite. A 3/4-in-thick coating of construction plaster was applied to the fire side of the previously tested uncoated steel stopping. The quantity of heat energy transmitted across this coated metal stopping was reduced approximately 50%. All stoppings prevented the passage of flame and smoke.

Jan 1, 1988

By Oliver C. Ralston

[This paper is an expanded revision of a report entitled "Froth Flotation and Agglomerate Tabling of Nonmetallic Minerals, " published in Transactions of the Canadian Institute of Mining and Metallurgy (vol. 40, November 1937, pp- 691-726) and prepared a year previously. Revisions embodied herein brine the data up to January 1, 1938. References have also been added to make the earlier paper more complete for the period it covered.]

Jan 1, 1938

The placer mining industry of the West Coast region of the South Island is based largely around the production of alluvial gold, although other valuable minerals are also present. Since the first major discoveries in 1864-65, reported gold production has totalled around 264 t (8.5 Moz). During the past 10 years, annual production has totalled around 1460 kg (47,000 oz). It is anticipated that gold production over the next three years will continue at a level of 1400-1800 kg.   Annual gold production peaked during 1866 at approximately 17,170 kg (550,000 oz) and has not exceeded 100,000 oz since 1885. This reflects the ease with which gold was won from shallow, rich deposits that were present at many localities. Subsequently, there has been a general decline in the availability of this type of deposit, a trend that will continue in the future. This paper outlines the present state of placer mining in the West Coast region, gives some historical background to the industry and briefly predicts future trends.

Jan 1, 1997

By J. E. Fraley

Full-column anchored resin bolts were first used in underground mines in 1972. These bolts appear to improve support in many roof bolt applications, as indicated by the use of about 30 million resin bolts in 1980. In the mid-1970's, Bureau of Mines in-vestigators began looking for a substitute for resin because of its short supply and rapidly increasing price. The investigators selected accelerated gypsum plaster (CaSO. ·1/2H20), which becomes gypsum (CaSO.· 2H20) when mixed with water. Gypsum makes an effective alternate grout material because it hardens quickly, is readily available, and is inexpensive in comparison with other cementitious materials. The Bureau received a patent (U.s. patent 4,096,944) for a system combining water capsules (wax-encapsulated water) with plaster into cartridges resembling resin cartridges. This report presents the results of tests conducted by the Bureau on the plaster, the water capsules, and their combined use in cartridges. The tests were designed to determine how the gypsum-plaster water capsule bolting system performs and what happens in the hole while the bolt is being inserted through the cartridge. The test results indicate that water capsule plaster cartridges are a workable alternative to resin cartridges under normal or dry conditions.

Jan 1, 1987

By Oliver C. Ralston

[This paper is an expmded revision of a report entitled "Froth Flota- tion and Agglomerate Tabling of Honmetdlic Idinerds, " published in Trans- actions of the Canadian Ir-stitute of Iriining and !,letdlurgy (vol. 40, November 1937, pp- 6? 1-726) and al'enared a year pr~viousl:~. Revisions en'oodied herein brinc the &ta I:T to Jn?uac"g 1, 193;. References have also been added to make the earlier paper more complete for the period it covered. This paper is an expmded revision of a report entitled "Froth Flota- tion and Agglomerate Tabling of Honmetdlic Idinerds, " published in Trans- actions of the Canadian Ir-stitute of Iriining and !,letdlurgy (vol. 40, November 1937, pp- 6? 1-726) and al'enared a year pr~viousl:~. Revisions en'oodied herein brinc the &ta I:T to Jn?uac"g 1, 193;. References have also been added to make the earlier paper more complete for the period it covered.]

Jan 1, 1938