混凝土的基础知识

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在其最简单的形式中，混凝土是糊剂和聚集体的混合物。由波特兰水泥和水组成的糊状物，涂上精细和粗聚集体的表面。通过称为水合的化学反应，糊状物强化并增益强度以形成称为混凝土的岩石状物质。

在这个过程中，将钥匙伸展到混凝土的显着特色：当硬化时，它是新混合，坚固耐用的塑料和可塑性。

混凝土的耐用性，实力和相对较低的成本使其成为全球建筑和基础设施的骨干，学校和医院以及机场，桥梁，公路和铁路系统。地球上最具产物的材料只需要更多的需求，例如，例如，发展中国家变得越来越城市，极端天气事件需要更耐用的建筑材料，其他基础设施材料的价格继续上升。

Even construction professionals sometimes incorrectly use the terms cement and concrete interchangeably. Cement is actually an ingredient of concrete. It is the fine powder that, when mixed with water, sand, and gravel or crushed stone (fine and coarse aggregate), forms the rock-like mass known as concrete.

用混凝土安全地工作
混凝土易于使用，多功能，耐用，经济。通过观察一些基本的预防措施，它也是安全的最安全的建筑材料之一。多年来，参与混合，处理和整理混凝土的人相对较少遭受伤害。

混凝土的形式

混凝土以四种基本形式生产，每种基本形式都有独特的应用和性质。

1. 现成混凝土，远是最常见的形式，占所有混凝土的近四分之三。它在当地的植物中批量，以便在熟悉的卡车中交货，带有旋转鼓。
2. 预制混凝土产品铸造出厂设置。这些产品受益于生产厂可实现的紧密质量控制。预制产品范围从混凝土砖和铺路石到桥梁，结构部件和墙板。混凝土砌体的另一种制造混凝土，可用于其传统的8×10×16英寸块。今天的砌体单元可以模塑成大量的形状，配置，颜色和纹理，以满足无限的建筑应用和建筑需求。
3. 基于水泥的材料代表了蔑视“混凝土”标签的产品，却分享了许多品质。该类别中的常规材料包括砂浆，灌浆和磨石。土壤 - 水泥和滚子压实混凝土 - 混凝土的“表兄弟”用于路面和水坝。此类别中的其他产品包括可流动的填充和水泥处理的基础。
4. 新一代先进产品包括纤维和特殊骨料，以创建屋顶瓷砖，摇瓦，圈壁板和台面。

如何制作水泥

波特兰水泥是混凝土的基本成分。混凝土形成与波特兰水泥形成糊状物，水与沙子和岩石结合到硬化。

Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients.

Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.

Leeds的Bricklayer Joseph Aspdin，英格兰首先在19世纪早期制造了波特兰水泥，在他的厨房炉中燃烧粉状石灰石和粘土。通过这种粗糙的方法，他为一个行业奠定了基础，该行业每年每年处理石灰石，粘土，水泥岩石和其他材料的山脉进入粉末，所以它会通过能够持有水的筛子。

水泥厂实验室通过频繁的化学和物理测试检查波特兰水泥制造的每一步。实验室还分析和测试成品，以确保其符合所有行业规范。

The most common way to manufacture portland cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about six inches. The rock then goes to secondary crushers or hammer mills for reduction to about three inches or smaller. The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln.

The cement kiln heats all the ingredients to about 2,700 degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special firebrick. Kilns are frequently as much as 12 feet in diameter—large enough to accommodate an automobile and longer in many instances than the height of a 40-story building. The large kilns are mounted with the axis inclined slightly from the horizontal.

The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.

随着材料通过窑移动，某些元件以气体的形式驱动。剩余的元素团结一致形成一种叫做熟料的新物质。熟料从窑出来的灰球，关于大理石的大小。
熟料从窑的下端排出炽热，一般被带到各种类型的冷却器中的处理温度。来自冷却器的加热空气返回到窑炉，这是一种节省燃料并提高燃烧效率的过程。

After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum and limestone. Cement is so fine that one pound of cement contains 150 billion grains. The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects.

虽然干法是制造水泥最具现代和最受欢迎的方式，但美国的一些窑炉使用潮湿的过程。除湿法外，这两个过程基本上是相似的，原材料用WATE研磨r前进入窑。

HOW CONCRETE IS MADE

In its simplest form, concrete is a mixture of paste and aggregates, or rocks. The paste, composed of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.

在这个过程中，将钥匙伸展到混凝土的显着特色：当硬化时，它是新混合，坚固耐用的塑料和可塑性。这些品质解释了为什么一种材料，混凝土可以建造摩天大楼，桥梁，人行道和超高速公路，房屋和水坝。

比例为
实现强大的耐用混凝土的关键是仔细按比例和混合的成分。不具有足够糊状物来填充聚集体之间所有空隙的混合物将难以放置，并将产生粗糙的表面和多孔混凝土。具有过量水泥浆料的混合物将容易放置并将产生光滑的表面;然而，所得到的混凝土不具有成本效益，并且可以更容易地破裂。

波特兰水泥的化学在水的情况下栩栩如生。水泥和水形成涂层的糊状物，涂层每种颗粒和沙子 - 聚集体。通过称为水合的化学反应，水泥浆料硬化并增长强度。

糊状物的质量决定了混凝土的特征。反过来，糊剂的强度依赖于水与水泥的比例。水柱比例是混合水的重量除以水泥的重量。通过在不牺牲新鲜混凝土的可加工性的情况下，通过降低水水泥比来生产高质量的混凝土，使其能够适当地放置，整合和固化。

A properly designed mixture possesses the desired workability for the fresh concrete and the required durability and strength for the hardened concrete. Typically, a mix is about 10 to 15 percent cement, 60 to 75 percent aggregate and 15 to 20 percent water. Entrained air in many concrete mixes may also take up another 5 to 8 percent.

其他成分
几乎所有的自然水drinkable and has no pronounced taste or odor may be used as mixing water for concrete. Excessive impurities in mixing water not only may affect setting time and concrete strength, but can also cause efflorescence, staining, corrosion of reinforcement, volume instability, and reduced durability. Concrete mixture specifications usually set limits on chlorides, sulfates, alkalis, and solids in mixing water unless tests can be performed to determine the effect the impurity has on the final concrete.

Although most drinking water is suitable for mixing concrete, aggregates are chosen carefully. Aggregates comprise 60 to 75 percent of the total volume of concrete. The type and size of aggregate used depends on the thickness and purpose of the final concrete product

Relatively thin building sections call for small coarse aggregate, though aggregates up to six inches in diameter have been used in large dams. A continuous gradation of particle sizes is desirable for efficient use of the paste. In addition, aggregates should be clean and free from any matter that might affect the quality of the concrete.

水合开始
结合聚集体，水和水泥后，混合物开始硬化。所有波特兰水泥是通过与水呼叫水合的化学反应设置和硬化的液压水泥。在该反应期间，节点在每个水泥颗粒的表面上形成。节点增长并展开，直到它与来自其他水泥粒子的节点连接或粘附到相邻的聚集体中。

Once the concrete is thoroughly mixed and workable it should be placed in forms before the mixture becomes too stiff.

During placement, the concrete is consolidated to compact it within the forms and to eliminate potential flaws, such as honeycombs and air pockets.

对于平板，混凝土留在架子上，直到表面湿膜消失，然后使用木材或金属手工用来光滑混凝土。浮动产生相对均匀，但略微粗糙，质地具有良好的防滑性，并且经常用作外部板的最终饰面。如果需要平滑，硬，致密的表面，漂浮后却将钢撕开。

在混凝土的暴露表面硬化以抵抗抗蚀剂后，始终始终始终。固化可确保水泥的持续水合，使混凝土继续增加力量。通过用水雾喷洒混凝土表面，或使用水分保留织物如粗麻布或棉垫。其他固化方法防止通过用称为固化化合物的塑料或特殊喷雾密封表面来蒸发水。

在极冷或炎热的天气中用于保护混凝土的特殊技术用于固化混凝土。混凝土保持潮湿的时间越长，它将变得越来越耐用。硬化速率取决于水泥的组成和细度，混合比例和水分和温度条件。混凝土继续变得更强壮，因为它变老了。大多数水合和强度增益发生在混凝土生命周期的第一个月内，但是水合率较慢的速率f或多年。

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