New Data on Coal, Gypsum, Iron and Silica Sand Deposits and Geochemical Exploration (Pakistan): Revision of 25 Years History of Dinosaur Discoveries from Pakistan

Discoveries of many coal seams at depths by drilling carried by Geological Survey of Pakistan in Sor Range and Harnai Gochina, extended the coal seams at depth which is challenge for mine owners to exploit feasibly. Bed to bed gypsum samplings (and their chemical analyses) of huge gypsum deposits from Sulaiman foldbelt is a base for industrialist and also planers to develop cement and gypsum industries to increase export and foreign exchange for the development of area and Pakistan. Low and high grade sedimentary iron deposits, silica sand and uranium host rocks and their extensions in Sulaiman and Kirthar foldbelts are presented. Anomalies of a few base metals arise as a result of geochemical exploration carried at part of Loralai District of Balochistan. Theropod dinosaurs were frequent in India, while Poripuchian titanosaurs (Sauropoda, Dinosauria) were frequent in Pakistan. Besides some ichnotaxa, many bone taxa such as 1 titanosauriform, 14 titanosaurian sauropod (including one new titanosaur), and 3 theropod dinosaurs are established from Pakistan. Among these 12 titanosaur species and 3 theropod species are named in about 10 km2 area of Vitakri dome and 2 titanosaur species are named in about a few hundred square meter area of Mari Bohri (Kachi Bohri) which is about 10 km westward from Vitakri dome. Pakistan is a unique country which discoverd 14 diversified titanosaurs in a short area and also in a short period (67 - 66 million years ago/Ma). About 400 bones found from a few meter thick upper part of upper shale horizon of latest Maastrichtian Vitakri Formation which is base for titanosaur taxa. Cranial material is in low fraction (but include significant diverse snouts), caudal vertebrae are prominent, the cervicals, dorsals and sacrals have significant numbers, forelimb and hind limb bones have balanced fraction. Humeri, femora and tibiae are most common. To know the position of Pakistani titanosaurs among titanosaurs and sauropods, there is a need to extend list of characters for phylogenetic analyses. This broad feature list should include main characters of titanosaurs from Pakistan and also from global world.

Effect of elevated temperature and silica sand particle size on minimum fluidization velocity in an atmospheric bubbling fluidized bed

The impact of temperature and particle size on minimumfluidizing velocity was studied and analyzed in a small pilot scale of bubbling fluidized bed reactor.This study was devoted to providing some data about fluidization to the literature under high temperature conditions.The experiments were carried out to evaluate the minimum fluidizing velocity over a vast range of temperature levels from 20℃ to 850℃ using silica sand with a particle size of 300-425μm,425-500μm,500-600μm,and 600-710μm.Furthermore,the variation in the minimumfluidized voidage was determined experimentally at the same conditions.The experimental data revealed that the Umf directly varied with particle size and inversely with temperature,whileεmf increases slightly with temperature based on the measurements of height at incipient fluidization.However,for all particle sizes used in this test,temperatures above 700℃ has a marginal effect on Umf.The results were compared with many empirical equations,and it was found that the experimental result is still in an acceptable range of empirical equations used.In which,our findings are not well predicted by the widely accepted correlations reported in the literature.Therefore,a new predicted equation has been developed that also accounts for the affecting of mean particle size in addition to other parameters.A good mean relative deviation of 5.473% between the experimental data and the predicted values was estimated from the correlation of the effective dimensionless group.Furthermore,the experimental work revealed that the minimum fluidizing velocity was not affected by the height of the bed even at high temperature.

Mechanism of Increase in Strength of Sodium Silicate-bonded Sand by Silica Sand Surface Modified in High Temperature.

With the aid of XRD, SEM and EDS etc., there is absorbed film on sand grain surface, high temperature modify makes the film sintered firmly on sand grain surface. Thus it changes physical and chemical characteristics of the film and sand grain surface, improves the wetting properties greatly, makes the fracture features of bonding bridge change from the adhesive to the cohesive and raises the strength of sodium silicate-bonded sand.

Production of High-Purity Silica Sand from Ivorian Sedimentary Basin by Attrition without Acid Leaching Process for Windows Glass Making

To produce high-purity silica sand usable for glass making, the present study was carried out. The objective of this work was to increase the silicon dioxide (SiO2) content to at least 99% using a simple process without chemical input. The raw sand samples were taken from the Ivorian sedimentary basin, from Maféré and Assinie areas, Côte d’Ivoire. Wet sieving and attrition technique were used for the purification process. The results from the energy dispersive spectrometer (EDS) analyses of the raw and treated samples show a significant increase of silica content and a significant reduction of impurities. The silica content (SiO2) of the sand of Maféré increases from 98.73% ± 0.15% to 99.92% ± 0.05%. And the sand of Assinie increased from 98.82% ± 0.67% in the raw samples to 99.44% ± 0.27% after treatment. The rate of iron oxide and alumina is reduced in these sands. Moreover, the sand of Maféré contains 53.2% of grains of size lower than 500 microns and that of Assinie contains 29.30%. Regarding the chemical composition of these purified sands, they meet the standard BS2975s, the American Ceramic Society and the National Bureau of Standards for window glass making.

The Development and Characterization of Zirconia-Silica Sand Nanoparticles Composites

The present study aims to develop zirconia-Silica sand nanoparticles composites through powder processing route and to study the physical properties, mechanical properties and microstructure of the composites. Zirconia based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% were developed through powder processing technique and sintered at 1500 ℃ for two hours. A decreasing trend of green density however an improvement in sintered density was observed. Also the addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 12.45 GPa and microstructures indicated the diffusion mechanism of silica sand nanoparticles into pore sites of the composites.

DEM Modeling of Particle Breakage in Silica Sands under One-Dimensional Compression

A Discrete Element Method （DEM） model is developed to study the particle break- age effect on the one-dimensional compression behavior of silica sands. The ＇maximum tensile stress＇ breakage criterion considering multiple contacts is adopted to simulate the crushing of circular particles in the DEM. The model is compared with published experimental results. Com- parison between the compression curves obtained from the numerical and experimental results shows that the proposed method is very effective in studying the compression behavior of silica sands considering particle breakage. The evolution of compression curves at different stress levels is extensively studied using contact force distribution, variation of contact number and particle size distribution curve with loading. It is found that particle breakage has great impact on com- pression behavior of sand, particularly after the yield stress is reached and particle breakage starts. The crushing probability of particles is found to be macroscopically affected by stress level and particle size distribution curve, and microscopically related to the evolutions of contact force and coordination number. Once the soil becomes well-graded and the average coordination number is greater than 4 in two-dimension, the crushing probability of parent particles can reduce by up to 5/6. It is found that the average contact force does not always increase with loading, but increases to a peak value then decreases once the soil becomes more well-graded. It is found through the loading rate sensitivity analysis that the compression behavior of sand samples in the DEM is also affected by the loading rate. Higher yield stresses are obtained at higher loading rates.

Assessment of strength development in stabilized soil with GBR PLUS and silica sand

This paper investigates the potential use of a nano polymer stabilizer, namely CBR PLUS for stabilization of soft clay and formulation of an optimal mix design of stabilized soil with CBR PLUS and silica sand. The highway settlements induced by the soft clay are prob- lematic due to serious damages in the form of cracks and deformation. With respect to this, soil compaction and stabilization is regarded as a viable method to treat shallow soft clayey ground for supporting highway embankment. The objectives of this paper are： i） to stabilize the compacted soil with CBR PLUS and silica sand in the laboratory; and ii） to evaluate the permeability, strength and California bearing ratio （CBR） of the untreated and stabilized soil specimens. The suitability of stabilized soil was examined on the basis of standard Proctor compaction, CBR, unconfined compression, direct shear, and falling head perme- ability tests. Furthermore, the chemical composition of the materials was determined using X-ray Fluorescence （XRF） test. It was found that the optimal mix design of the sta- bilized soil is 90% clay, I% CBR PLUS, 9% silica sand. It is further revealed that, stabilization increases the CBR and unconfined compressive strength of the combinations by almost 6- fold and 1.8-fold respectively. In summary, a notable discovery is that the optimum mix design can be sustainably applied to stabilize the shallow clay without failure.

纳米硅溶胶改良辽宁台安砂土的抗液化性能研究

辽宁台安砂土属于易液化砂,提升其抗液化性能具有重要的工程意义。文章针对纳米硅溶胶(CS)对辽宁台安砂土抗液化性能的改良效果进行探究,通过不排水动三轴试验,对纯砂样和改良砂样的液化特性进行对比研究,分析CS浓度和固化时间两个参量对改良砂样动力特性的影响。研究结果表明:(1)CS能够显著提升台安砂土的抗液化性能,在动载作用下改良砂样均未发生液化破坏。(2)随CS浓度和固化时间的增加,试样动孔压u_(d)、动应变ε_(d)呈现先迅速下降后趋于平缓的发展规律;当CS浓度增至4%、固化时间达到3周后,试样抗液化性能的提升效果不再明显。(3)改良砂样的滞回曲线变得更加稳定。随CS浓度增加,阻尼先降低后趋于稳定,动弹性模量逐渐增大并趋于平缓,但伴随有一定的波动;随固化时间增大,阻尼呈减小趋势,动弹性模量呈增大趋势。研究成果可为辽宁台安地区砂土液化治理提供参考依据。

硅砂、陶粒砂和宝珠砂铸造工艺性能研究

研究了鄂尔多斯硅砂、通辽硅砂、海南海砂、陶粒砂和宝珠砂的形貌,用其做原砂的碱酚醛树脂砂的抗拉强度,原砂抗机械破碎和粉化能力等。结果表明:鄂尔多斯硅砂形貌最差,呈尖角、片状;通辽砂、海砂较好,呈圆形、多角形;陶粒砂和宝珠砂最好,呈圆形。型砂24 h时抗拉强度,鄂尔多斯硅砂最低,只有0.277 MPa;通辽硅砂和海砂较高,接近0.6 MPa;宝珠砂最高,接近0.9 MPa;陶粒砂为0.667 MPa,高于硅砂,低于宝珠砂。经机械搅拌破碎试验得出:鄂尔多斯硅砂强度较低,抗破碎能力最差,易破碎粉化,粉尘含量由0.03%提高到0.812%;通辽硅砂和海砂强度都较好,粉化较轻,粉尘含量由0.016%提高到0.32%;陶粒砂强度也较好,粉化较少,粉尘含量由0提高到0.195%;宝珠砂破碎和粉化率极低,粉尘含量基本无变化。

Quantification of Silicon (SI) and Silicon Dioxide (SiO2) from the Nafud Desert-Al-Qassim Region, Kingdom of Saudi Arabia Using XRD Analysis

This research was conducted in the Qassim region, Kingdom of Saudi Arabia. The goal of this research is to determine the percentage of silicon in the Rub al-Khali desert. Samples were collected from four cities located in the Al-Qassim Region of Saudi Arabia (Uyun Al-Jawa, Al-Fuwailiq, Al-Sulaibiya, and Al-Qawara), from three distinct depths (the earth’s surface, 50 cm, and 100 cm). The percentages of silicon in these places vary between the highest value for silicon dioxide, which is 74.47 m/m%, and 34.8 m/m% for silicon in Al-Qawara city at a depth of 100 cm. We used an x-ray fluorescence (XRF) instrument to evaluate the samples. There are high percentage of both silica and silicon in the Nafud desert. Studies have shown that these ratios can help investors benefit from an element of Silicon and silicon dioxide, so the sands of the Nafud desert is sufficient for extracting Silicon and silica in huge quantities. This may transform the Kingdom into a leading country in the global computer technology industry that depends on silicon extracted from the desert sands, the most important of which are microcomputer data processing devices.

X射线荧光光谱法对硅砂中主要成分的检测

建立了一种对硅砂中成分进行快速测定的方法。样品经过碳化钨的研磨,制成能通过200目(筛孔径0.075 mm)标准筛的粉末,经1000℃灼烧2 h,去除里面含有的碳以及有机物。按照特定的比例在1050℃的高频熔样炉中制成玻璃片。标准物质采用日本耐火材料技术协会系列标准物质,按照说明书800℃灼烧后,按照和样品同样的熔样方法制作玻璃标片,在XRF光谱仪中选定待测元素的2θ角以及PHD能级范围,进行测定。标准曲线制作完毕后,用国家标准物质进行检测,经检测,该方法检测精确度高,误差小,能够满足化学分析的要求,结果令人满意。该方法适用于硅质砂岩以及铸造用砂。

Evaluation of the microstructure, secondary dendrite arm spacing, and mechanical properties of Al–Si alloy castings made in sand and Fe–Cr slag molds

The microstructure and mechanical properties of as-cast A356（Al–Si） alloy castings were investigated. A356 alloy was cast into three different molds composed of sand, ferrochrome（Fe–Cr） slag, and a mixture of sand and Fe–Cr. A sodium silicate–CO_2 process was used to make the necessary molds. Cylindrical-shaped castings were prepared. Cast products with no porosity and a good surface finish were achieved in all of the molds. These castings were evaluated for their metallography, secondary dendrite arm spacing（SDAS）, and mechanical properties, including hardness, compression, tensile, and impact properties. Furthermore, the tensile and impact samples were analyzed by fractography. The results show that faster heat transfer in the Fe–Cr slag molds than in either the silica sand or mixed molds led to lower SDAS values with a refined microstructure in the products cast in Fe–Cr slag molds. Consistent and enhanced mechanical properties were observed in the slag mold products than in the castings obtained from either sand or mixed molds. The fracture surface of the slag mold castings shows a dimple fracture morphology with a transgranular fracture nature. However, the fracture surfaces of the sand mold castings display brittle fracture. In conclusion, products cast in Fe–Cr slag molds exhibit an improved surface finish and enhanced mechanical properties compared to those of products cast in sand and mixed molds.

掺珊瑚砂粉砂浆抗硫酸镁侵蚀性能研究

本文研究了硫酸镁作用下掺珊瑚砂粉(CSP)和辅助胶凝材料(SCMs)砂浆的抗硫酸镁侵蚀性能。在5和20℃硫酸镁溶液中侵蚀至365 d,通过外观、长度变化、抗压强度,结合X射线衍射谱和傅里叶变换红外光谱分析砂浆的抗硫酸镁侵蚀性能。发现在5℃的硫酸镁溶液中侵蚀至365 d时,掺CSP砂浆发生严重劣化。掺20%(质量分数)CSP的抗硫酸盐硅酸盐水泥比掺20%(质量分数)CSP的普通硅酸盐水泥表现出更好的抗硫酸镁侵蚀性能。在5℃下粉煤灰和矿渣有助于改善掺CSP砂浆的抗硫酸镁侵蚀性能,然而在20℃下硅灰降低其抗硫酸镁侵蚀性能。在5℃下掺CSP砂浆主要发生镁盐和碳硫硅钙石型硫酸盐侵蚀并伴随少量石膏生成,在20℃下主要发生镁盐和石膏型硫酸盐侵蚀。

Effect of Silica Fume on Compressive Strength of Oil-Polluted Concrete in Different Marine Environments

In the present research, effect of silica fume as an additive and oil polluted sands as aggregates on compressive strength of concrete were investigated experimentally. The amount ofoil in the designed mixtures was assumed to be constant and equal to 2% of the sand weight. Silica fume accounting for 10%, 15% and 20% of the weight is added to the designed mixture. After preparation and curing, concrete specimens were placed into the three different conditions： fresh, brackish and saltwater environments （submerged in fresh water, alternation of exposed in air ＆ submerged in sea water and submerged in sea water）. The result of compressive strength tests shows that the compressive strength of the specimens consisting of silica fume increases significantly in comparison with the control specimens in all three environments. The compressive strength of the concrete with 15% silica fume content was about 30% to 50% higher than that of control specimens in all tested environments under the condition of using polluted aggregates in the designed mixture.

Reactivity of Fine Quartz in Presence of Silica Fume and Slag

Dune sand is a very abundant material in south of Algeria. Its high silica content gives a partial pozzolanic reactivity due to its crystalline state. This paper investigates the evolution of cement hydration based on a binary addition particularly the reactivity of dune sand finely ground in the presence of an amorphous addition: silica fume or blast furnace slag. Thus, four combinations of binary additions by substitution have been chosen. The X-ray diffraction analyses performed on cement pastes containing additions have shown the importance of the mineralogy and silica content of additions on their pozzolanic reactivity. Dune sand becomes reactive at long term, especially when associated up to 10% of amorphous addition (blast furnace slag or silica fume). It results an increasing in mechanical strength of Ultra High Performance Concrete (UHPC) and an improvement of the microstructure.

钙质砂介质中爆炸波传播规律的试验研究

开展了一系列钙质砂和石英砂的地面爆炸试验,主要对比分析了两种砂土介质中爆炸波的传播规律,包括峰值压力、弹塑性波速及升压时间、爆坑尺寸等。试验结果表明,爆炸波在钙质砂中的传播与在石英砂中存在较大差异:地面爆炸作用下钙质砂爆坑较石英砂爆坑的直径和深度更小,且成坑形状为两阶同心圆;钙质砂中弹性波速为236~300 m/s,石英砂中弹性波速为218~337 m/s,弹性波速和塑性波速均随炸药质量增加而增大;爆炸波在钙质砂中的升压时间随比例距离的增加而增加,而在石英砂中升压时间随比例距离变化不明显,且较钙质砂中升压更迅速;在地面爆炸作用下,低含水率钙质砂的衰减系数为2.86,石英砂为2.79。

海绵城市背景下硅砂透水砖性能研究

采用氢化双酚A型环氧树脂改性硅砂透水砖,探究硅砂粒径(35目、50目、70目)与环氧树脂掺量(2%、4%、6%、8%)对硅砂透水砖的强度、透水性能、保水性能、滤水性能以及防滑性能的影响规律。试验结果表明:当硅砂粒径为50目、环氧树脂掺量为4%时,硅砂透水砖的抗压、抗折和防滑性能最好,透水速率为1.5 mL/(min·cm^(2))、保水率为0.068 g/cm^(3),滤水率为90.2%。

页岩石粉加气混凝土砌块的制备与微观分析研究

新产出粉煤灰不足以供应加气混凝土企业的生产,故与省内某大型加气混凝土企业共同研究硅砂-炉渣-页岩石粉加气混凝土的力学性能与微观分析。选用水胶比、生石灰掺量、硅砂掺量、炉渣掺量、石膏掺量、铝粉掺量、减水剂掺量、页岩石粉粒径、页岩石粉掺量作为影响因素,进行正交试验,测得试样的抗折、抗压强度、干密度。试验结果得出抗折、抗压强度均较高的试样配合比。且进行X射线衍射(XRD)、扫描电子显微镜(SEM)微观分析,得到矿物组成成分与抗折断裂表面的微观结构。这些均为加气混凝土企业研发并制备新型加气混凝土砌块的配合比及相应的力学性能、微观分析提供参考。