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By S. Kahraman

The prediction of rock properties from indirect testing methods is important, particularly for preliminary investigations since indirect tests are easier and cheaper than the direct tests. In this study, we investigate the predictability of the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) of rocks from the indentation hardness index (IHI) obtained using point load apparatus. Forty-six different rock types, 14 of which were igneous, 15 were metamorphic, and 17 were sedimentary were tested in the laboratory. The UCS and BTS values were correlated with the corresponding IHI values and the results were statistically analysed. The influence of rock classes on the relationships was also investigated. A strong correlation between UCS and IHI was found for all data. The correlation between BTS and IHI is not as strong as the correlation between UCS and IHI. However, it is in the acceptable limits. When the regression analyses were repeated for igneous, metamorphic, and sedimentary rocks, the correlation coefficients were generally increased. The results show the UCS and BTS can be estimated from IHI. In addition, the effect of rock classes on the relationships between IHI and both UCS and BTS is important.

Jan 1, 2012

Grains are subject to contamination by mycotoxins which are metabolic by-products of various fungi. The fungal infestations produce local concentrations of the mycotoxins thousands of times higher than the average. These facts make the sampling of the grain for assessment of the mean mycotoxin levels potentially very difficult. In the context of sampling theory, this morphology of the infestations creates a very high distributional and intrinsic heterogeneity of the grain shipment. The distributions of mycotoxin concentrations in seaborne shipments that exist at loading and the number and intensity of infestations that develop under shipping conditions are unknown. All grain shipments carry spores that may give rise to mycotoxin-producing colonies; moisture and temperature determine the final extent of the problem. This paper develops the value of the sampling constant with respect to intrinsic heterogeneity based on data on observed Ochratoxin A (OTA) concentrations in individual wheat kernels. A useful relationship between the distribution of mycotoxin concentrations on a kernel to kernel basis and the distribution of concentration over subsamples is developed.

Jan 1, 2009

By Kedikilwe Oageng

Effective perimeter control during drilling and blasting is critical not only to blasting results but also to the overall stability of the pit over its entire life span. A pit where perimeter control is not given enough attention when conducting drilling and blasting operations, often experiences over-break or back break beyond final pit wall limits, and therefore has a relatively high probability of failure. Such a pit also becomes unsafe, sometimes not easily accessible, has increased loading costs due to production of oversize, longer cycle times and often problems are encountered when blasting subsequent benches. All these are undesirable consequences, which have negative cost implications. Specialised blasting techniques such as trim blasting and pre-splitting have over the years proved to be effective perimeter control measures. However, the success of these techniques is directly attributable to the time and effort given to the processes. This paper presents results of a project undertaken to monitor, review and optimize the trim blasting and pre-splitting processes at Orapa Diamond Mine in Botswana. The project was specifically incepted to improve the final wall conditions, which continued to deteriorate due to persistent over-break during blasting. The paper also analyses the results obtained against a benchmark of results taken prior to project implementation. Specific blast design parameters which are critical to blasting results were identified as problem areas after auditing of the pre-implementation drilling and blasting practices. These include drill-hole depth, spacing, splitting factor for pre-splits and timing of trim blasts. The impact of different rock types on the results was also studied, and recommendations were made at different phases of the project and results obtained after implementation analysed until optimum results were achieved.

Jan 1, 2008

By T. van Heerden

A range of supported gold catalysts was prepared by ion exchange, varying many of the preparation variables, including concentration in the precursor solution, washing procedure, as well as drying and calcination procedures. These catalysts have been characterized extensively. TEM images show essentially the same crystallite size distributions, between 2?5 nm, for almost all catalysts, the only exception being catalysts not washed in ammonia, which did not show any small crystallites. Additional characterization with SEM yielded an interesting discovery. Catalysts that appear identical on the TEM also contain some large crystallites in the range of 50?500 nm. Differences in dispersion due to the drying procedure not seen on the TEM can now be observed. Oxygen chemisorption is being investigated as an additional method to characterize gold based catalysts to complement the typically used electron microscope techniques.

Jan 1, 2012

By I. Ince, S. Kahraman, M. Rostami, B. Dibavar

The density, porosity, and strength of rocks are fundamental in the design of geo-engineering projects. Determining these properties requires the preparation of smooth core samples, which is usually impossible for soft rocks. Besides, only fragmented samples may be available in some projects. A method for predicting rock properties from rock particles such as drilling debris would therefore be useful. This study was undertaken to develop prediction equations for compressive strength (UCS), tensile strength (BTS), density, and porosity values from the crushability index (CI) obtained from rock fragments. The results showed that UCS, BTS, density, and porosity were strongly correlated with the CI. The physical characteristics and strength of rocks may be predicted with the help of the derived equations. The CI test is a valuable tool for estimating rock properties in drilling projects and in situations where core specimens are not available.

Mar 14, 2024

By G. R. Drennan, N. J. Wagner, M. J. T. Sebola

The Soutpansberg Coalfield hosts South Africa's hard coking coal reserves. However, coals in this region are understudied compared to other coalfields in the country. This study characterizes the properties of fine-float fraction samples extracted from a wide diameter borehole core in the Makhado Project, Tshipise sub-basin, Soutpansberg coalfield. Conventional analyses were used to determine the coal quality, petrographic composition, mineralogy, geochemistry (including trace element and rare earth element composition), and free swelling index of samples from six coal horizons and three partings from the economic No.6 Seam. The coal samples are classified as medium rank bituminous C coals (0.88 %RoVmr, 0.92 %Rmax) and are highly vitrinitic in composition (97 vol% mineral matter free (mmf)). The samples show strong caking potential (FSI of 9). The total rare earth concentrations range between 570 and 3193 ppm in the ash samples. Preliminary analysis show all but two samples are promising sources of rare earth elements as the total concentrations exceeded the 1000 ppm cut-off grade. Further research is required to confirm these preliminary findings.

Aug 2, 2022

By Y. Tanaka, H. Miki, Y. Aoki, H. Okamoto, G. P. W. Suyantar, T. Hirajima

Due to environmental limitations and the scarcity of freshwater, flotation using seawater or desalinated seawater as process water becomes more common for mining operations. On the other hand, seawater has been reported to affect the flotation behavior of sulfide minerals. Few reports are available on influence of pyrite depression, recycled seawater and lime consumption on flotation by using seawater. In this study, the flotation tests were performed using ore sample to investigate the effect of pH with seawater and process water used in plant on the flotation behavior in a laboratory-scale flotation cell and a pilot plant-scale. The results of laboratory scale flotation indicated that copper and molybdenum flotation kinetics decreased with increasing pH. Furthermore, the iron (mainly pyrite) recovery decreased with increasing pH. The pilot plant-scale flotation test showed that water with a higher concentration of magnesium and calcium (plant processes water) consumed a higher amount of lime. Because of low lime consumption and high copper and molybdenum recovery and grade, pH 8 is suitable compared with pH 8.5 for flotation. Keywords: seawater, process water, copper-molybdenum rougher flotation, pH, pilot test

Jan 1, 2020

Robert Rampton Porter died on 8th September, 1985, in Salt Lake City, Utah, at the age of 75. Bob Porter was born in Salt Lake City in 1910, and he attended the University of Utah, where he obtained an M.Sc. degree in metallurgy. Galvanizing In conjunction with the National Institute for Materials Research of the CS I R, the South African Hot-Dip Galvanizers' Association has organized the First International Conference on Galvanizing in South Africa. This event will take place at the C SIR Conference Centre in Pretoria from 3rd to 7th November, 1986. Environmental effects of mining A one-day meeting entitled 'The environmental effects of mining and restoration' will be held on 23rd September, 1986, at the University of Manchester Institute of Science and Technology, Manchester, England.

Jan 1, 1986

By B. M. Munyungano

Rössing Uranium Mine operates a recovery circuit with continuous ion exchange followed by solvent extraction. Serious organic degradation problems were encountered during 1985/6, 2000 and 2005 in the solvent extraction plant. The preferential loss of the tertiary amine extractant was observed during the above-mentioned period. Previous investigations revealed that the tertiary amine was breaking down to nitrosamine, which cannot take part in the exchange reaction with U3O8. A reduction in the redox potential of the solvent extraction plant feed to below 500 mV halted this preferential loss. A lot of effort has been made to try and understand the actual mechanism for nitrosamine formation. Current understanding for the degradation is that formation is due to high nitrates on the strip side of the circuit emanating from nitrates from the precipitation process using ammonia. It is the current belief that pH lower than 3.7 on the strip side results in loading of nitrates onto the solvent. If oxidizing conditions prevail on the extraction side of the solvent extraction circuit, the tertiary alamine will then degrade into nitrosamine. This phenomenon is yet to be established and verified. It has, however, been established that the above process is brought about the following conditions ?High redox potential greater than 550 mV predominately caused by a high Fe3+/Fe2+ratio (4:1) ?Perception that if Fe2+<0.5 g/lit will contribute to high redox ?High concentrations of NO-3 in the conc eluate (feed to SX)/ammonium sulphate (NO-3> 4 g/l based on historic values) ?Presence of Mo as a catalyst ?Tests also have proved that the presence of nitrous acid in a concentration of 1 g/lat 550 mV leads to formation of nitrosamines from alamine.

Jan 1, 2007

By T. Nyakudarika

The Unki Platinum Mines concentrator, employing an MF2 circuit configuration which includes fully-autogenous primary milling of run-of-mine (ROM) ore, was commissioned in November 2010. The project was Anglo American Platinum?s first PGM concentrator in Zimbabwe and would form a significant contribution to the group?s platinum production. The project financials demonstrated that the project was operating-cost sensitive. After reviewing the metallurgical testwork, mineralogical examinations, and the history of similar operations, it became apparent that the Unki ore characteristics rendered it amenable to autogenous milling. The primary ball mill, structurally designed for 30 per cent steel load, could be operated at the required initial phase throughput with fully-autogenous primary milling, realizing savings in both power requirements and grinding media consumption. The original mill sizing had been done with fully-autogenous milling in mind, but allowing for flexibility and mitigation in case of varied mining fragmentation. Since attaining steady state, target grinds have been achieved. This paper looks at the Unki ore characterization programme, design considerations, and the operational and control philosophy for a successful comminution circuit, and discusses the design to produce a flexible, low opex, mitigated comminution and overall MF2 flowsheet that is easily expanded in line with the potential for optimum exploitation of the orebody.

Jan 1, 2012

By J. W. Latilla, J. J. van Wijk

In late 1997 a request was received to assist with determining the powered support unit (shield) load capacities for the planned 2 seam short wall. This project had a number of aspects which made it attractive to utilize numerical modelling in conjunction with other more conventional design tools in the design of the shields. Amongst these were: The 2 seam panels were to be laid out about 25 m below the previously short walled 4 seam, the 4 seam had in turn been over-mined by the 5 seam long wall, the proposed face height of the 2 seam short wall was 5.5 m while the 4 seam had been mined at 4 m. The top seam in the area (5 seam) had been mined at between 1.5 and 2.2 m high, the face conditions with about 95 m of broken material applying dead weight loading to the 2 to 4 seam inter-burden septum were hard to predict and cyclical loading due to the presence of strong sandstone bands in the 2 to 4 seam inter-burden. The basic thrust of the study was to take the known, and successful, situation (4 seam short wall) and carry out comparative modelling to enable prediction of likely 2 seam conditions. Some two dimensional aspects studied were: 5 m goaf hanging up behind shields, stresses in beams to determine likely first goaf roof span, stresses in cantilever beams to asses cyclical loading due to sandstone bands in the interburden being loaded by the overlying goaf and stresses on chain and crush pillars adjacent to the goaf edge. Three dimensional aspects that were investigated included: Load distribution along face for close goafing and 5 m goaf hang-up and load in a 1 m wide rib modelled in the position of the powered support units. From the modelling it was possible to determine the optimal shield leg capacity of the new 2 seam equipment. These outputs were used when drawing up the technical specifications for manufacture of the new equipment. The face was successfully commissioned in August 2002. Fin 1997, requête fut faite pour aider à la détermination des capacités de charge pour l’unité de soutènement mécanisée (bouclier) pour la couche 2 courte taille en projet. Certains aspects de ce projet le rendaient intéressant pour utiliser la modélisation numérique en même temps que d’autres méthodes conventionnelles pour la conception des boucliers. Parmi ces aspects se trouvaient : Les panneaux de la couche 2 devaient être placés environ 25 m au dessous de la couche 4 courte taille ; la couche 4 avait été remplacée par la couche 5 longue taille ; la hauteur de taille proposée pour la couche 2 courte taille était 5.5 m, tandis que la couche 4 avait été exploitée à 4 m. La couche supérieure de la région (couche 5) avait été exploitée entre 1.5 et 2.2 m de hauteur ; il était difficile de prédire les conditions de taille, avec environ 95m de matériaux cassés ajoutant une charge morte à la plaque de séparation entre les couches 2 et 4 et un chargement cyclique causé par des bandes de grès dans l’entre-fardeau 2-4. L’idée principale de l’étude fut de prendre la situation connue et réussie (couche 4 courte taille) et de faire une modélisation comparative pour prédire les conditions probables de la couche 2. Certains des aspects à double dimension qui furent étudiés étaient : Un accrochage de remblai de 5m derrière les boucliers ; contraintes dans les poutres pour déterminer le premier intervalle probable entre remblai et toit ; contraintes dans les poutres en porte-à-faux pour évaluer le chargement cyclique causé par les bandes de grès dans l’entre-fardeau qui est accablé par le remblai et les contraintes sur les piliers par chaîne et d’écrasement adjacents au bord du remblai. Aspects à trois dimensions qui furent étudiés : Distribution de la charge le long de la taille pour les remblais proches et l’accrochage de remblai de 5 m et la charge dans une nervure de 1 m de large modelée dans la position des unités de soutènement mécanisées. La modélisation a permis de déterminer la capacité de portée optimale du bouclier du dispositif nouveau pour la couche 2. Ces résultats furent utilisés pour dresser les spécifications techniques pour la fabrication de l’équipement nouveau. La taille fut commissionnée avec succès en août

Jan 1, 2003

By G. Akdogan, S. M. Bradshaw, A. P. Van Wyk, T. Punt

Recycling has become an important part of the lithium-ion battery (LIB) life cycle due to the growing demand for energy storage in applications like electric vehicles and renewable energy. Recycling spent LIBs provides a secondary source for strategically scarce metals, like lithium and cobalt, helping to reduce the environmental impact of LIBs. Organic acids have been proven to be effective lixiviants with the benefit of reduced environmental impacts, amongst which citric acid has shown to exhibit similar extraction performance when compared to mineral acids. Leaching LCO and NMC batteries with 1.5M citric acid and 2 vol.% H2O2 at 95°C, 20 g/L for 20 minutes achieved 93% Al, 90% Co, 96% Li, 94% Mn and 94% Ni dissolution. The strong chelating property of citric acid affects the separation of the metals, providing unique extraction opportunities. The first extraction uses 12 vol.% D2EHPA at a pH of 2.5 and O/A ratio of 2 to separate 96.4% Mn and 100% Al from the PLS in two counter-current stages. Stripping the loaded organic with 1.25M citric acid at an A/O ratio of 3 allows for up to 91% stripping of the manganese in a single stage. The second extraction then separates 96.5% Li from the PLS in three counter-current stages using 20 vol.% D2EHPA at a pH 5.5 and O/A ratio of 5. The raffinate remaining after the second separation contains 48.4 wt.% Co and 50.3 wt.% Ni. Keywords: Hydrometallurgy, lithium-ion batteries, metal recycling, citric acid, solvent extraction

Jan 1, 2020

By M. Kumral, S. Li, M. Balci, Z. Shao

Main haulage roads play an important role in the performance of underground mines because of the cost of transportation of the extracted ore, equipment, and workers. During mine development, these roads are designed through manual tools or CAD-based software. However, the optimisation of these roads is still a complex problem due to some constraints such as minimum turning radius and maximum gradient. By utilising Dubins path theory, three elevation cases; namely low, medium and high are defined, considering gradient constraint as well as the minimum turning radius in a three-dimensional space. The shortest path between two points can then be found by the three-dimensional Dubins path algorithm with elevation constraint. As a further step, a three-dimensional Dubins path algorithm with elevation constraint for multiple points is also developed for multi-point cases. The effectiveness of these algorithms is tested through case studies in order to determine the optimal path between different points.

Sep 1, 2021

By S. T. L. Harrison, A. Kotsiopoulos, M. D. Maluleke, E. Govender-Opitz

In the extraction of base metals from printed circuit boards (PCBs) using bioleaching, the accumulation of metal ion stress in solution has been shown to inhibit the microbial regeneration of ferric iron. This poses a challenge for the development of this technology for e-waste treatment. The paper explores the application of a microbial immobilisation system in a two-stage bioleaching system consisting of a chemical leaching reactor in series with a microbial ferric iron regenerating reactor to mitigate microbial inhibition and to enhance base metal extraction. A mixed microbial culture dominated by L. ferriphilum, L. ferrooxidans and At. Caldus was maintained over a period of two months in the presence of polyurethane foam which acted as the biomass support particle. Microbial metabolic activity of immobilised cells and their tolerance to inhibitory Cu ions was investigated. Results showed that immobilised microbial cells maintained higher ferrous iron oxidation activity compared to planktonic cells in the presence of increasing Cu2+ concentrations up to 6 g/L. This presents an opportunity for microbial immobilised systems to be adopted in two-stage bioleaching system. Keywords: Bioleaching, microbial immobilisation systems, microbial inhibition and ferrous iron oxidation

Jan 1, 2020

By A. C. Lawrence

A new approach to the -study of human factors in stope productivity by A. C. LAWRENCE B. Econ., D. Com. (S.A.) (Member) The extent of the improvement in mean performance which could be achieved by reducing the variance between stoping gangs is examined, and it is shown that a worthwhile gain would result if variance were reduced by as little as 5 to 15 per cent. The problem of identifying human factors which contributed towards variance in gang performance was examined in one gold mine. A total of 342 &apos;observations&apos; on 49 stoping gangs were gathered, each observation consisting of a set of figures for 36 variables for one gang for one week. The variables included &apos;stope factors&apos; such as face length, &apos;gang factors&apos; such as the ethnic composition of the gang, and &apos;supervisory factors&apos; such as the experience of the miner. These variables were related to &apos;tons trammed per week&apos; as a measure of work performance. The findings showed that certain of the predictor variables accounted for 66 per cent of the variance in gang performance and about two thirds of this could be attributed to gang and supervisory factors, that is to the &apos;human factors&apos;. The method suggests a basis for a new approach to the identification of human factors and is a promising step towards optimizing gang performance.

A powerful, interactive metallurgical process simulator for use on micro- computers has been developed in the Department of Metallurgy and Materials Engineering at the University of the Witwatersrand. MICROSIM presently allows simulation of all ore-dressing flowsheets and a selection of hydrometallurgical unit operations, and is extendable to all such processes. MICROSIM is written in Pascal. This modern language provides very versatile data structures which can be effectively used to solve the major problem in generalised simulation programs, namely storage and transmission of data relating to liquid and solid phases. Dynamic memory allocation allows optimal utilisation of computer storage space. The simulator utilises very efficient precalculation algorithms that determine the tear streams for optimal sequential modulator calculation convergence. Microcomputer graphics simplifies flowsheet specification, and form-filling data capture with supplied default values eliminate most common input errors.

Jan 1, 1987

By Roger A. Blais, Michel David

"Matheron&apos;s geoslalislical method for the estimation of ore reserves has been developed to the point at which real-life problem may be handled effectively. The steps involved in the method are:(i) obtalning the variogram,(ii) fitting a model, and(iii) producing block estimates.All three steps may cause difficulty, and would-be users need a deep understanding of the theory if failure is to be avoided.To illustrate these points, specific cause are considered:(i) two almost equidimensional porpbyry deposits, one drilled randomly and the other regularly; and(ii) two iron formation, one drilled extensively and being mined, while the other is still at the stage of early estimation."

Jan 1, 2014

By D. Hu, J. Xu, N. Liao, C. Wu, J. Ye

The vertical stirring mill’s fine grinding equipment is affected by the operating conditions during the grinding process. The grinding media has a great influence on the energy consumption and particle size distribution. This paper investigates the fine grinding performance of nano-ceramic balls and steel balls of the same weight for magnetite by a wet grinding process in a vertical stirring mill, where 15 mm nano-ceramic balls and 12 mm steel balls are used as grinding media to carry out batch grinding tests. We have observed that the newly qualified particle content of the nano-ceramic balls is higher than steel balls of the same weight at the same specific energy. The reason may be the advantage of a greater surface area and volume filling rate with the nano-ceramic balls. Moreover, the specific energy of nanoceramic balls is less than steel balls of the same weight under the same grinding fineness. In addition, energy efficiency indicates that the nano-ceramic ball has a higher energy efficiency than a steel ball of the same weight. This is due to the light bulk density of nano-ceramic balls. The application of a nanoceramic ball in a vertical stirring mill will improve iron ore grinding performance. Keywords: Steel balls, nano-ceramic balls, vertical stirring mills, fine grinding, particle size distribution, energy consumption

Jan 1, 2020

NOTICES PROCEEDINGS OF THE SECOND INTERNATIONAL CLEAN AIR CONGRESSThis massive volume of 1,380 pages contains all the papers presented at the congress held in December 1971. INDEX TO SOUTH AFRICAN PERIODICALS This bibliographical work has been produced by the Johannesburg Public Library since 1945, and is of interest to all our readers. THE CONTROL OF GASEOUS SULPHUR COMPOUND EMISSION An international conference on this theme will be held at the Salford University from 10th to 12th April, 1973. COLLOQUIUM ON SLlMES DAMS The South African Institute of Mining and Metallurgy have great pleasure in advising members that two-day colloquium on Slimes Dams is being arranged for the 14th and 15th November, 1973. NATIONAL INSTITUTE FOR METALLURGY / NASIONALE INSTITUUT VIR METALLURGIE REPORT. VERSLAG No. 1424 REVIEW OF THE WORLD&apos;S FLUORSPAR INDUSTRY, WITH PARTICULAR REFERENCE. TO SOUTH AFRICA Ist August, 19n Investigator: H. H. Gossling SYNOPSIS The consumption of fluorspar has increased significantly during the last three years, and a consumption of approximately 5,76 million tonnes per annum is projected for 1975. REPORT. VERSLAG No. 1432 LABORATORY METHOD No. 44/2 THE DETERMINATION OF RUTHENIUM AND OSMIUM IN THE RESIDUES RESULTING FROM THE LEACHING OF MATTES 5th July, 19n Investigators: Magdalena M. KrUger R. V. D. Robert SYNOPSIS The method described involves the sintering of the residue with barium peroxide, and the distillation of ruthenium and osmium from the sinter. REPORT. VERSLAG No. 1439 THE REACTION OF SULPHIDE MINERALS WITH THIOL COMPOUNDS 29th June, 19n Investigator: L. A. Goold SYNOPSIS A selected group of thiol reagents was reacted with a wide range of sulphide minerals, and products that were formed at the surface were extracted and identified by infrared spectrophotometry.

By P. R. Jochens, D. D. Howat, C. W. Wolhuter

Prof D. D. Howat (Member): I am a man with a grievance this afternoon. The other authors of the paper entered into a conspiracy to ensure that I presented the paper, and finally even had the audacity to say that this was the least that could be expected from me as I had done so little of the other work. Looking at the distinguished audience here that includes some figures who have forgotten more about cement that some of us have ever learned, I realise how right the other authors were. I feel very much cast in the role of the fool who was pushed in where angels fear to tread. I hesitate to say, Sir, that I would not use the word angels in any definition of the authors of this paper. In presenting the paper, may I try to put forward a few simple points about cement that are probably as little known to the majority of the audience as they were to me-at least until very recently. Concrete, made by mixing Portland cement, sand, crushed rock and water is the most widely used constructional material in the world. Generally the production of actual Portland Cement is about two-thirds that of steel and by the time this is formed into concrete the total is about five times the world tonnage of steel produced. A very rough approximation suggests that world consumption of concrete is about one ton per person per annum. Apart from fresh water mankind consumes no other material in such quantities. What mankind originally required was a mortar to be used for joining blocks of stone or bricks. Such mortar was originally made from limestone burned in a kiln and then mixed with water. Production of mortar of this type began over 5,000 years ago. Some samples from pyramids in Egypt have shown this mortar to be in good condition although over 4,500 years old. The progress of technological development was very slow until 1824 when an English bricklayer, Joseph Aspidin, patented a new mortar material which he made by burning limestone and clay together in his kitchen stove. Aspdin called his product &apos;Portland Cement&apos; because, in colour, it resembled a well-known building stone quarried in the Isle of Portland on the south coast of England. Aspid&apos;s same types of raw materials are used today in modern cement production and the product is still referred to as Portland cement. A lime-containing material such as chalk or shell and a clay-type material such as shale, slate or clay itself, are mixed in the required proportions, ground and fed to a kiln where the minimum burning temperature is about 1,500°C. The raw materials react to form hard chunks of a material known as &apos;clinker&apos;. About 5 per cent of gypsum is added to the clinker and the mixture is then ground to a very fine powder, the function of the gypsum being to control the rate of setting of the concrete. The key oxides in cement production are lime, silica, alumina and iron oxide. The possible reactions occurring during and the products of the burning process are shown in Table I.

Jan 12, 1968