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1、Portland cementPortland cement (often referred to as OPC, from Ordinary Portland Cement) is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout. It is a fine powder produced by grinding Portland ceme
2、nt clinker (more than 90%), a limited amount of calcium sulfate (which controls the set time) and up to 5% minor constituents as allowed by various standards such as the European Standard EN197.1 ASTM C 150 defines portland cement as hydraulic cement (cement that not only hardens by reacting with wa
3、ter but also forms a water-resistant product) produced by pulverizing clinkers consisting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition. Clinkers are nodules (diameters： 0.2-1.0inch 525mm) of a sintered material
4、 that is produced when a raw mixture of predetermined composition is heated to high temperature. The low cost and widespread availability of the limestone, shales, and other naturally occurring materials make portland cement one of the lowest-cost materials widely used over the last century througho
5、ut the world. Concrete becomes one of the most versatile construction materials available in the world. Portland cement clinker is made by heating, in a kiln, a homogeneous mixture of raw materials to a sintering temperature, which is about 1450 C for modern cements. The aluminium oxide and iron oxi
6、de are present as a flux and contribute little to the strength. For special cements, such as Low Heat (LH) and Sulfate Resistant (SR) types, it is necessary to limit the amount of tricalcium aluminate (3CaO.Al2O3) formed. The major raw material for the clinker-making is usually limestone (CaCO3) mix
7、ed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or SiO2 is used. The CaCO3 content of these limestones can be as low as 80%. Second raw materials (materials in the rawmix other than limestone) depend on the purity of the lime
8、stone. Some of the second raw materials used are: clay, shale, sand, iron ore, bauxite, fly ash and slag. When a cement kiln is fired by coal, the ash of the coal acts as a secondary raw material History Portland cement was developed from natural cements made in Britain in the early part of the nine
9、teenth century, and its name is derived from its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England. The Portland cement is considered to originate from Joseph Aspdin, a British bricklayer from Leeds. It was one of his employees (Isaac
10、 Johnson), however, who developed the production technique, which resulted in a more fast-hardening cement with a higher compressive strength. This process was patented in 1824. His cement was an artificial cement similar in properties to the material known as Roman cement (patented in 1796 by James
11、 Parker) and his process was similar to that patented in 1822 and used since 1811 by James Frost who called his cement British Cement. The name Portland cement is also recorded in a directory published in 1823 being associated with a William Lockwood, Dave Stewart, and possibly others.Aspdins son Wi
12、lliam, in 1843, made an improved version of this cement and he initially called it Patent Portland cement although he had no patent. In 1848 William Aspdin further improved his cement and in 1853 he moved to Germany where he was involved in cement making. Many people have claimed to have made the fi
13、rst Portland cement in the modern sense, but it is generally accepted that it was first manufactured by William Aspdin at Northfleet, England in about 1842. The German Government issued a standard on Portland cement in 1878. ProductionThere are three fundamental stages in the production of Portland
14、cement:1. Preparation of the raw mixture 2. Production of the clinker 3. Preparation of the cement To simplify the complex chemical formulae which describe the compounds present in cement, a cement chemist notation was invented. This notation reflects the fact that most of the elements are present i
15、n their highest oxidation state, and chemical analyses of cement are expressed as mass percent of these notional oxidesRawmix preparationThe raw materials for Portland cement production are a mixture of minerals containing calcium oxide, silicon oxide, aluminium oxide, ferric oxide, and magnesium ox
16、ide, as fine powder in the Dry process or in the form of a slurry in the Wet process. The raw materials are usually quarried from local rock, which in some places is already practically the desired composition and in other places requires the addition of clay and limestone, as well as iron ore, baux
17、ite or recycled materials. The individual raw materials are first crushed, typically to below 50mm. Formation of clinkerThe raw mixture is heated in a cement kiln, a slowly rotating and sloped cylinder, with temperatures increasing over the length of the cylinder up to a peak temperature of 1400-145
18、0 C. A complex succession of chemical reactions takes place (see cement kiln) as the temperature rises. The peak temperature is regulated so that the product contains sintered but not fused lumps. Sintering consists of the melting of 25-30% of the mass of the material. The resulting liquid draws the
19、 remaining solid particles together by surface tension and acts as a solvent for the final chemical reaction in which alite is formed. Too low a temperature causes insufficient sintering and incomplete reaction, but too high a temperature results in a molten mass or glass, destruction of the kiln li
20、ning, and waste of fuel. When all goes according to plan, the resulting material is clinker. On cooling, it is conveyed to storage. Some effort is usually made to blend the clinker because, although the chemistry of the rawmix may have been tightly controlled, the kiln process potentially introduces
21、 new sources of chemical variability. The clinker can be stored for a number of years before use. Prolonged exposure to water decreases the reactivity of cement produced from weathered clinker.The enthalpy of formation of clinker from calcium carbonate and clay minerals is about 1500 to 1700 kJ/kg.
22、However, because of heat loss during production, actual values can be much higher. The high energy requirements and the release of significant amounts of carbon dioxide makes cement production a concern for global warming.Cement grindingIn order to achieve the desired setting qualities in the finish
23、ed product, a quantity (2-8%, but typically 5%) of calcium sulfate (usually gypsum or anhydrite) is added to the clinker and the mixture is finely ground to form the finished cement powder. This is achieved in a cement mill. The grinding process is controlled to obtain a powder with a broad particle
24、 size range, in which typically 15% by mass consists of particles below 5 m diameter, and 5% of particles above 45 m. The measure of fineness usually used is the specific surface area, which is the total particle surface area of a unit mass of cement. The rate of initial reaction (up to 24 hours) of
25、 the cement on addition of water is directly proportional to the specific surface area. Typical values are 320380 m2kg1 for general purpose cements, and 450650 m2kg1 for rapid hardening cements. The cement is conveyed by belt or powder pump to a silo for storage. Cement plants normally have sufficie
26、nt silo space for 120 weeks production, depending upon local demand cycles. The cement is delivered to end-users either in bags or as bulk powder blown from a pressure vehicle into the customers silo. In industrial countries, 80% or more of cement is delivered in bulkUseThe most common use for Portl
27、and cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Users may be in
28、volved in the factory production of pre-cast units, such as panels, beams, road furniture, or may make cast-in-situ concrete such as building superstructures, roads, dams. These may be supplied with concrete mixed on site, or may be provided with ready-mixed concrete made at permanent mixing sites.
29、Portland cement is also used in mortars (with sand and water only) for plasters and screeds, and in grouts (cement/water mixes squeezed into gaps to consolidate foundations, road-beds, etc.). When water is mixed with Portland Cement, the product sets in a few hours and hardens over a period of weeks
30、. These processes can vary widely depending upon the mix used and the conditions of curing of the product, but a typical concrete sets in about 6hours and develops a compressive strength of 8MPa in 24hours. The strength rises to 15MPa at 3days, 23MPa at 1week, 35MPa at 4weeks and 41MPa at 3months. I
31、n principle, the strength continues to rise slowly as long as water is available for continued hydration, but concrete is usually allowed to dry out after a few weeks and this causes strength growth to stop. Cement plants used for waste disposal or processing Due to the high temperatures inside ceme
32、nt kilns, combined with the oxidizing (oxygen-rich) atmosphere and long residence times, cement kilns are used as a processing option for various types of waste streams: indeed, they efficiently destroy many hazardous organic compounds. The waste streams also often contain combustible materials whic
33、h allow the substitution of part of the fossil fuel normally used in the process. Waste materials used in cement kilns as a fuel supplement Paint sludge from automobile industries Waste solvents and lubricants Meat and bone meal - slaughterhouse waste due to bovine spongiform encephalopathy contamin
34、ation concerns Waste plastics Sewage sludge Rice hulls Sugarcane waste Used wooden railroad ties (railway sleepers) Portland cement manufacture also has the potential to remove industrial by-products from the waste-stream, effectively sequestering some environmentally damaging wastes Slag Fly ash (f
35、rom power plants) Silica fume (from steel mills) Synthetic gypsum 波特兰水泥硅酸盐水泥(OPC),通常是指从普通硅酸盐水泥)是最常见的一种水泥在世界各地的一般用途,因为它是一种基本成分的混凝土、砂浆、粉刷、最非专业浆液。它是一种细粉磨硅酸盐水泥熟料生产的(90%以上),限定的硫酸钙(可控制设定的时间)和5%,小成分作为所允许的各种标准如欧洲标准波特兰水泥ASTM(美国材料试验协会)C 150定义为“液压水泥(水泥,不仅与水反应,产生变硬,但也形成了一个防水的产品)所产生的制粉熟料包含基本液压钙硅酸盐,通常含有一个或更多的形式的硫
36、酸钙作为国米地面加法。”熟料是结节(直径：0.2-1.0英寸【5 - 25 mm】)的烧结材料,原料混合后,会产生对未知成分是高温加热。低成本和普遍的可用性的石灰石、页岩,和其他自然形成的物质使硅酸盐水泥材料的广泛使用成本上个世纪世界各地。在这个世界混凝土成为最多才多艺的建筑材料。波特兰水泥熟料是通过加热,在一个窑、均匀混合的原料,烧结温度,这是一个关于标准稠度用水量1450C对现代。氧化铝和氧化铁的存在作为磁链和起太大作用的力量。为特别的水泥,如低热量(LH)和硫酸盐抗性(SR)类型,有必要限制在一定数量的铝酸三钙(3CaO.Al2O3)形成。主要原料为熟料决策通常是石灰岩(碳酸钙)混有第二
37、种材料硅铝硅酸盐含粘土作为源的。通常,一种不稳定的石灰石含有黏土或二氧化矽使用。碳酸钙含量的这些石灰岩可以低至80%。第二原料(材料以外的rawmix石灰岩)取决于纯净的石灰石。一些第二所用原材料是:粘土、页岩、沙子、铁矿石、铝矾土、粉煤灰及矿渣。当水泥窑是燃煤电厂，对煤炭灰作为辅助原料历史普通硅酸盐水泥,是发展自英国制造的自然水泥早期的19世纪,公司的名字却来自其相似度到开拓者的石头,是建筑物的形式被开采出来的石头在曼岛在多塞特郡波特兰的英格兰水泥被认为是源于Joseph Aspdin,一个英国泥瓦匠。这是他的一个员工(艾萨克约翰逊),但是,产品的生产工艺,开发了一个更加fast-harde
38、ning水泥具有更高的抗压强度。这一过程在1824年获得发明专利。他是一个人工水泥水泥在性质上的相似的物质被称为“罗马水泥”(专利1796年詹姆斯帕克)和他的过程相似,使用专利1822年以来由詹姆士弗罗斯特1811人给他水泥”英国水泥”。 命名为“波特兰水泥“也记录在1823年出版的目录正在与一个威廉洛克伍德，戴夫史都华，可能还有其他相关的。 Aspdin的儿子威廉,于1843年,当时提出了一种改进的版本,这使他当初水泥和普通硅酸盐水泥,称之为“专利”,虽然他没有专利。1848年, William Aspdin进一步改进了他的水泥和1853年他移居德国。在那里他参与了水泥制造。许多人都声称取得
39、了在现代意义上的第一个硅酸盐水泥，但普遍认为它最初是由威廉诺斯夫利特，英国阿斯平丁在大约1842年制造的。德国政府发行的1878年对波特兰水泥标准。生产有三个基本阶段生产硅酸盐水泥。1。制备原料的混合物2。熟料生产3。制备水泥为了简化复杂的化学公式，描述了该化合物在水泥目前，水泥化学家符号被发明出来。这种符号反映了事实，即大多数元素都是目前的最高氧化状态，和水泥化学分析，因为这些名义氧化物质量百分比表示Rawmix制备硅酸盐水泥的生产原料是一种含有氧化钙，氧化硅，氧化铝，氧化铁，氧化镁和矿物质的混合物，如干进程的细粉或在泥浆中的湿进程的形式。原材料通常是从当地开采石头，这在一些地方已几乎想要的
40、组成和在其他地方需要粘土和石灰石此外，还有铁矿石，铝土矿或再生材料。个体首先是原料粉碎，通常低于50毫米。熟料形成原料的混合料加热,一个慢速转动水泥窑筒体,与温度及斜的长度增加到钢瓶的峰值温度的1400-1450C。一个复杂的化学反应，连续发生（见水泥窑）随着温度的升高。峰值温度的调节，使产品含有烧结硬块但不融合。烧结包括了25-30的熔融材料的质量。由此产生的液体提请剩下的固体颗粒在一起的表面张力，并作为最终的化学反应中alite组成溶剂的行为。温度过低会导致不完整的反应烧结和不足，但过高的熔融体中的一个或玻璃，窑衬的破坏，浪费燃料温度的结果。当一切都按计划进行，由此产生的材料是熟料。对冷却
41、，它传达给存储。一些努力通常是由融合的熟料，因为虽然rawmix的化学物质可能已被严密控制，窑过程的化学变化可能引入新的资金来源。熟料可以保存的数年内后再使用。长时间暴露于水中可以降低水泥生产的反应性风化反映。熟料形成了从碳酸钙和粘土矿物焓约1500至1700千焦耳/公斤。但是，由于在生产过程中的热损失，实际值可能要高得多。高能源需求和二氧化碳的大量释放，使水泥生产为全球变暖的关注。水泥胶砂为了实现在成品所需的设置素质，是硫酸钙（通常石膏或硬石膏）数量（2-8，但一般为5）被添加到熟料和磨细的混合物形成的成品水泥粉。这是实现水泥磨机。研磨过程控制，以获得具有广泛的粒度范围的粉末，通常15的质量
42、直径小于5微米，5微米以上的颗粒45uM的颗粒组成。细度测量通常采用的是“比表面积“，这是总的水泥颗粒表面单位质量面积。初始反应关于加水水泥（最多24小时）的速度是成正比的比表面积。典型值是一般用途的水泥320-380平方米公斤- 1，和450-650平方米kg的“快速硬化“水泥- 1。水泥是由皮带或粉末输送泵到一个储存筒仓。水泥厂一般有1-20周筒仓生产足够的空间，根据本地需求周期而定。水泥是交付给最终无论是在包装袋或散装粉状从一到客户的筒仓压力车辆被炸用户。在工业化国家，80以上的水泥散装交付使用 波特兰水泥的最常见用途是在混凝土的生产。混凝土是一种复合材料，集料（砂石），水泥和水组成。作
43、为结构材料，混凝土可转换几乎任何形状所需，一旦硬化，可以成为一个结构性的（承载）元素。用户可能参与了预制厂生产的单位，如板，梁，道路设施，或作出现浇混凝土现浇上层建筑，如建设，道路，水坝。这些可能随现场搅拌混凝土的，也可能与“预拌“在永久性混合用地作出具体规定。波特兰水泥也用在抹灰和找平砂浆（只用沙和水）和水泥浆（水泥/水混合成的差距压缩到巩固基础，路床等）。当水相混合,产品集硅酸盐水泥在几小时内和变硬经过几周。这些过程都可能有很大的依赖混合使用和养护条件下的产品,而且是典型的混凝土集在大约6个小时和开发出一种抗压强度在24小时内8MPa。上升到15MPa的力量在3天,23 MPa在1周、4周
44、后35兆帕,41%的MPa在3个月。原则上，实力继续缓慢上涨，只要继续水化水可用，而是具体的，通常让其干燥后几个星期，导致强度增长停止查看字典详细内容水泥工厂用于处理废弃物或加工由于在水泥窑的高温，与氧化剂（氧气丰富）的气氛和长停留时间相结合，水泥窑是用来作为各类废物处理选项流：的确，他们有效地摧毁许多有害的有机化合物。废物流也常常包含允许的通常在使用过程中部分替代化石燃料的燃烧材料。应用于水泥窑废料作为燃料的补充油漆污泥汽车产业废溶剂和润滑油肉类和骨粉-屠宰场的下脚料，由于牛海绵状脑病污染问题废塑料污水污泥稻壳甘蔗废物用于木制铁路枕木（铁路枕木）波特兰水泥生产也有可能消除，产品从废物流，有效地隔绝了一些破坏环境的工业废料渣粉煤灰（发电厂）硅粉（从钢铁厂）合成石膏
