جستجوی مقالات مرتبط با کلیدواژه "سیمان" در نشریات گروه "مهندسی معدن"

Considering the consumption of more than 25% of energy by raw mill materials in cement plants, providing a suitable plan for blending different mining zones can be an effective approach in reducing the energy consumption. The purpose of this paper is optimizing the plan of blending limestone mining zones to reduce milling energy consumption raw mills (ball mill and HPGR). The geomechanical properties of different mine zones have been identified by performing the bond work index, drop weight, and uniaxial compressive strength (UCS) tests. Also, to comply with cement production standards, cementing modules including S.I.M, A.L.M, and L.S.F have been calculated for different mine zones. Mining production planning with the aim of achieving the minimum comminution energy and transportation costs has been developed by the Goal programming method. Planning constraint equations are also considered to regulate cement modules. Finally, utilizing windows Quantitative System for Business software, the necessary calculations have been carried out. Based on the results, the extraction order and blending values of different mine zones are adjusted regarding cement modules and minimizing transportation costs, leading to a reduction in energy consumption of raw mills.

Cement-based solidification/stabilization is one of the common methods for increasing the stability of heavy metals in contaminated soils. However, the presence of some of the heavy metals such as lead ions causes a delay and prevention in cement hydration which makes this method as an inapplicable. Enhancement of contaminated clayey soils by NaOH can remove the problems associated with cement hydration delay in presence of heavy metal ions. The main objective of this paper is to determine the impact of enhancement on solidification/stabilization of contaminated soils in extreme acidic and alkaline environment. To achieve the above mentioned objective, samples of contaminated bentonite by 50 and 100 cmol/kg-soil of lead nitrate at two different conditions of enhancement by NaOH and without enhancement were solidified/stabilized by 10 and 50 percentages of cement. The extreme acidic and alkaline conditions simulated by performing of equilibrium soil washing, endorsed TCLP test in solidified/stabilized cured samples. In addition, series of XRD experiments were performed to address the rate and quantity of CSH formation. The achieved results indicate that at extreme alkaline conditions the enhancement of contaminated bentonite has decreased the leach-ability of lead ions around 96%. With a decrease in pH of samples to the quantities less than 5, the use of enhanced samples has reduced the quantity of leachate in enhanced samples in comparison to unenhanced samples around 90%. This is attributed to the contaminant retention by clay fraction of bentonite and contaminant solidification by CSH gels.

Nowadays, modern and environmentally friendly methods have been used to stabilize soils and to improve soil engineering properties. One of these methods is formation of calcium carbonate precipitation in soil pores for increasing strength, cohesion, hardness of soil and decreasing soil permeability. Since most studies have been performed on the formation of calcium carbonate precipitation by using urea hydrolysis by bacteria. In this study, calcite precipitation was made by direct use of urease enzyme. In this method there is no limitation like using of bacteria and also there is no harmful effects on planting. This study investigated the effect of adding urease enzyme to cement and zeolite-stabilized sandy soils as well as the effect of fine aggregates. The results of the uniaxial strength tests showed that with 10% replacement of zeolite instead of cement while 10% fine grains were used, more resistance was observed to the samples without zeolite and with less fine grains. On the other hand, by adding urease enzyme with 4% cement, 10% fine grains and urease enzyme in the comparison of samples without enzyme increased the compressive strength at 14 and 28 days, 5.12 and 4.107, respectively.

The main purpose of this study is to investigate experimentally the quality of Pozzolanic prospects hosted in the Eocene pyroclatic succession of the Tarum magmatic range in the Zanjan province، northwest Iran. These prospects were discovered regionally in our previous work using Mineral Potential Mapping، MPM، as an integrated exploration method، consisting of the remote sensing analysis، geologic data، field observation and GIS modeling. During our previous study، some rock samples were collected for the detailed laboratory examinations. Regarding our plan، the samples have been analyzed using Petrography، XRD، XRF، physical tests and pozzolanic activity respectively. The careful petrography studies indicated five possible samples as suitable and promising targets. Further، the results of the physical tests suggest an appropriate conformity between the samples and international standards for evaluating the pozzolanic samples. Though، the samples could not meet the required standards for the pozzolanic activation test. Our further examination indicated that the combination of tuffs of the area from which the samples have been taken were generally andesitic. However، this study characterized that despite existence of some glass phase and also zeolite indications، the discovered pozzolanic prospects may not be suitable for industrial consume to produce the pozzolanic cement

The existence of swelling soils causes irretrievable damages to buildings all over the world. Due to the swelling property of the gypsum soils, located in South West of Mashhad, many problems such as cracking in building, heaving of walls, and pavement and bulging of floors have been reported. The soil in this region is generally fine and based on Unified Classification is predominantly ML and CL. In the present research, 6 typical samples, among many gathered samples, with identical gradation but different amount of gypsum, were selected. After determination of main geotechnical properties of samples (including gypsum percent, Atterberg limits, natural unit weight and density), the effect of gypsum amount on the swelling potential and swelling pressure was investigated. Considering the influence of degree of compaction, on the swelling potential and swelling pressure, 10 samples for each of 6 typical soils, with identical moisture content but different unit weight were prepared and the variation of the swelling potential and swelling pressure were studied. The results of this research indicate the harsh effect of the gypsum amount, degree of compaction and moisture content on the swelling potential and swelling pressure. The improvement of such soils which are a type of problematic soils has been of many researchers interest. In the present research a sample with 10.57% gypsum and unit weight of 1.83 g/cm3 and with a determined swelling potential was improved using three different methods, including mixing with lime, double mixing with lime and mixing with cement. The amount of admixture for all three methods was 1, 2, 3 and 4 percent. The results of this research indicate that mixing with cement is able to reduce considerably the swelling potential and to improve the swelling specifications of this type of soil.