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1、1,Chapter 6 Reinforced Concrete,Chapter 6,2,Conversation 1.Our concrete material is mixed in a rotating-drum batch mixer at the job site. 我们用的混凝土是在现场的间歇式转筒搅拌机中搅拌的。 2. Quality of concrete depends on proper placing, finishing, and curing. 混凝土的质量取决于适当的灌注、抹光和养护。 3. The workers tend to start the final fi
2、nishing now. 工人们现在打算开始最后的抹光作业。 4. The concrete can be made stronger by pre-stressing in our factory. 在我们厂里可以使混凝土通过预加应力得到增强。,Chapter 6,3,5. Most of construction material can be tested in our laboratory. 我们的实验室可以检验大部分建筑材料。 6. We shall finish the civil work by the end of the year. 在年底前我们将完成土建工作。 Cement
3、 steel and timber are the most important construction materials used in civil engineering. 水泥、钢材和木材是土建工程中最重要的建筑材料。 7. These are the anchor bolts (rivets, unfinished bolts, high-strength structural bolts) for the structure. 这是用于结构的锚定螺栓（铆钉、粗制螺栓、高强度结构用螺栓）。,4,8. The holes of anchor bolts will be grouted
4、 with normal (Portland, non-shrinkage) cement mortar. 这些地脚螺孔将灌入普通（波特兰，无收缩）水泥砂浆。 9. We usually measure the strength of concrete at 28 days after which has been cast. 我们通常在混凝土灌注后28天测定其强度。 10. The average compressive strength of samples is 500kg/cm2. 试样的平均抗压强度为500公斤/平方厘米,Chapter 6,5,Text Reinforced con
5、crete is concrete in which reinforcement bars (“rebars”) （钢筋）, reinforcement grids（钢筋网）, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that
6、is reinforced with iron or steel. 钢筋混凝土是由混凝土，钢筋（钢筋），钢筋网（钢筋网），钢板网，钢板或纤维组成，这些被用来加强混凝土的张力。 它由法国园丁约瑟夫莫尼尔于1849年发明，并于1867年获得专利。混凝土仅指用钢或钢加固的混凝土。,Chapter 6,6,Other materials used to reinforce concrete can be organic and inorganic fibres as well as composites in different forms. Concrete is strong in compres
7、sion, but weak in tension, thus adding reinforcement increases the strength in tension. In addition, the failure strain of concrete in tension is so low that the reinforcement has to hold the cracked sections together. For a strong, ductile and durable construction the reinforcement shall have the f
8、ollowing properties: 其他用于加固混凝土的材料可以是有机和无机纤维以及不同形式的复合材料。 混凝土压缩强度大，但抗拉性弱，因此加入钢筋可增加抗拉强度。 另外，混凝土的拉伸破坏应变很小，依靠钢筋拉力来控制裂缝。 对于坚固，延展性和耐用的结构，钢筋应具有以下特性：,7,High strength 高强度 High tensile strain 高拉伸应变 Good bond to the concrete 与混凝土结合良好 Thermal compatibility 热兼容性 Durability in the concrete environment 在具体环境中的耐久性,C
9、hapter 6,8,In most cases reinforced concrete uses steel rebars that have been inserted to add strength. 在大多数情况下，钢筋混凝土采用钢筋加入以增加强度。 Use in construction Concrete is reinforced to give it extra tensile strength; without reinforcement, many concrete buildings would not have been possible. 增强混凝土的抗拉强度; 没有钢
10、筋水泥，许多混凝土建筑物将不可能实现。,9,Reinforced concrete can encompass many types of structures and components, including slabs, walls, beams, columns, foundations, frames and more. 钢筋混凝土可以包括许多类型的结构和构件，包括平板，墙，梁，立柱，基础，框架等等。 Reinforced concrete can be classified as precast or cast in-situ concrete. 钢筋混凝土可以分为预制或现浇混凝土
11、。,10,Much of the focus on reinforcing concrete is placed on floor systems. Designing and implementing the most efficient floor system is a key to creating optimal building structures. Small changes in the design of a floor system can have significant impact on material costs, construction schedule,
12、ultimate strength, operating costs, occupancy levels and end use of a building. 大部分建筑注重加强混凝土的地板系统。 设计和实施最高效的地板系统是创建最佳建筑结构的关键。 地板系统设计的微小变化会对建筑物的材料成本，施工进度，最终强度，运营成本，入住率和最终用途产生重大影响。,11,Behavior（性能）of reinforced concrete Materials Concrete is a mixture of of Coarse (stone or brick chips) and Fine (gener
13、ally sand) aggregates with a binder material (usually Portland cement). When mixed with a small amount of water, the cement hydrates form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid structure. 混凝土是粗粒（石块或砖块）和细粒（通常是沙粒）与粘结材料（通常是波特兰水泥）的混合物。 当与少量水混合时，水泥水合物形成微观
14、不透明晶格，将聚集体封装并锁定在刚性结构中。,Chapter 6,12,Typical concrete mixes have high resistance to compressive stresses (about 4,000psi (28MPa); however, any appreciable tension (e.g., due to bending) will break the microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, ty
15、pical non-reinforced concrete must be well supported to prevent the development of tension. 典型的混凝土混合料对压缩应力具有很高的抵抗力（约4,000 psi（28 MPa）; 然而，任何可观的张力（例如由于弯曲）都会破坏微观的刚性格子，导致混凝土开裂和分离。 出于这个原因，典型的无筋混凝土必须被很好地支撑以防止张力的发展。,13,If a material with high strength in tension, such as steel, is placed in concrete, then
16、 the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A reinforced concrete section where the concrete resists the compression and steel resists the tension can be made into almost any shape and size for the construction industr
17、y. 如果钢筋等高强度的材料置于混凝土中，则复合材料钢筋混凝土不仅能抵抗压缩，还能抵抗弯曲和其他直接拉伸作用。 钢筋混凝土部分的混凝土抗压缩和钢筋抗张力可以制成几乎任何形状和大小的建筑构件。,Chapter 6,14,Key characteristics Three physical characteristics give reinforced concrete its special properties. 三种物理特性赋予钢筋混凝土其特殊性能。 First, the coefficient of thermal expansion of concrete is similar to t
18、hat of steel, eliminating large internal stresses due to differences in thermal expansion or contraction. 首先，混凝土的热膨胀系数与钢相似，消除了由于热膨胀或收缩差异而产生的巨大内部应力。,15,Second, when the cement paste within the concrete hardens this conforms to the surface details of the steel, permitting any stress to be transmitted
19、efficiently between the different materials. Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel. 其次，当混凝土内的水泥浆硬化时，钢筋表面的构造，可以在不同材料之间有效地传递任何应力。 钢筋通常是粗糙的或波纹状的，以进一步改善混凝土和钢之间的粘结或内聚力。,Chapter 6,16,17,Third, the alkaline（碱性的）chemical environ
20、ment provided by the alkali reserve (KOH, NaOH) and the portlandite (calcium hydroxide) contained in the hardened cement paste causes a passivating film to form on the surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions。 第三，硬化水泥浆中含有的碱性物质（
21、KOH，NaOH）和氢氧化钙（氢氧化钙）提供的碱性（碱性的）化学环境会在钢的表面形成钝化膜，比在中性或酸性条件下更耐腐蚀,Chapter 6,18,. When the cement paste exposed to the air and meteoric water reacts with the atmospheric CO2, portlandite and the Calcium Silicate Hydrate (CSH) （水化硅酸钙）of the hardened cement paste become progressively carbonated and the high
22、 pH gradually decreases from 13.5 12.5 to 8.5, the pH of water in equilibrium with calcite (calcium carbonate) and the steel is no longer passivated. 当暴露于大气中的水泥浆与大气中的二氧化碳发生反应时，硬化水泥浆体的硅酸钙水化硅酸钙（CSH）逐渐碳化，高pH值从13.5 12.5至8.5，与方解石（碳酸钙）的水的pH平衡并且钢也不再钝化。,19,As a rule of thumb, only to give an idea on orders
23、of magnitude, steel is protected at pH above 11 but starts to corrode below 10 depending on steel characteristics and local physico-chemical conditions when concrete becomes carbonated. Carbonation of concrete along with chloride ingress are among the chief reasons for the failure of reinforcement b
24、ars in concrete. 作为一个经验法则，只有在数量级上给出一个说法，钢在pH值高于11时受到保护，但在混凝土碳化时取决于钢的特性和局部物理化学条件而开始腐蚀到10以下。 混凝土碳化和氯化物侵入是混凝土中是钢筋破坏的主要原因。,Chapter 6,20,The relative cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some co
25、lumns. Reinforcing bars are normally round in cross-section and vary in diameter. Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture however, the size of and location of the cracks can be limited and controlled by reinforcement, placeme
26、nt of control joints, the curing methodology and the mix design of the concrete. Cracking defects can allow moisture to penetrate and corrode the reinforcement. This is a serviceability failure in limit state design. Cracking is normally the result of an inadequate quantity of rebar, or rebar spaced
27、 at too great a distance. The concrete then cracks either under excess loading or due to internal effects such as early thermal shrinkage when it cures. 混凝土部分的开裂是无法防止的; 然而，裂缝的大小和位置可以通过加固，控制缝的位置，固化方法和混凝土的混合设计来限制和控制。 开裂缺陷可能使水分渗透并腐蚀钢筋。 这是极限状态设计中的可维护性故障。 裂纹通常是由于螺纹钢数量不足或钢筋间距太大而造成的。 混凝土随后会在过载或由于内部影响（如固化时的
28、早期热收缩）而破裂。,Chapter 6,30,Ultimate failure leading to collapse can be caused by crushing of the concrete, when compressive stresses exceed its strength; by yielding or failure of the rebar, when bending or shear stresses exceed the strength of the reinforcement; or by bond failure between the concrete
29、 and the rebar. 当压缩应力超过其强度时，导致混凝土破碎的最终失效可能是由混凝土的破碎引起的; 通过屈服或失败的钢筋，当弯曲或剪切应力超过钢筋的强度时; 或混凝土和钢筋之间的粘结失败。,31,Carbonation Carbonation, or neutralisation, is a chemical reaction between carbon dioxide in the air with calcium hydroxide and hydrated calcium silicate in the concrete. The water in the pores of
30、Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5. This highly alkaline environment is one in which the embedded steel is passivated and is protected from corrosion. According to the Pourbaix diagram for iron, the metal is passive when the pH is above 9.5. 碳化或中和是空气
31、中的二氧化碳与混凝土中的氢氧化钙和水合硅酸钙之间的化学反应。 波特兰水泥混凝土孔隙中的水通常是碱性的，其pH值范围为12.5至13.5。 这种高度碱性的环境是嵌入钢钝化并防腐蚀的环境。 根据铁的普贝图，当pH高于9.5时，金属是不会被腐蚀的,Chapter 6,32,The carbon dioxide in the air reacts with the alkali in the cement and makes the pore water more acidic, thus lowering the pH. Carbon dioxide will start to carbonate
32、the cement in the concrete from the moment the object is made. This carbonation process will start at the surface, then slowly move deeper and deeper into the concrete. The rate of carbonation is dependent on the relative humidity of the concrete - a 50% relative humidity being optimal. If the objec
33、t is cracked, the carbon dioxide in the air will be better able to penetrate into the concrete. 空气中的二氧化碳与水泥中的碱反应，使孔隙水变酸，从而降低pH值。 二氧化碳将开始使混凝土中的水泥发生碳酸盐化。 这种碳酸化过程将从表面开始，然后慢慢地向混凝土深入。 碳化速度取决于混凝土的相对湿度 - 50的相对湿度是最佳的。 如果物体破裂，空气中的二氧化碳会更好地渗透到混凝土中。,33,When designing a concrete structure, it is normal to state
34、the concrete cover for the rebar (the depth within the object that the rebar will be). The minimum concrete cover is normally regulated by design or building codes. If the reinforcement is too close to the surface, early failure due to corrosion may occur. The concrete cover depth can be measured wi
35、th a cover meter. However, carbonated concrete only becomes a durability problem when there is also sufficient moisture and oxygen to cause electro-potential corrosion of the reinforcing steel. 在设计混凝土结构时，说明钢筋的混凝土保护层（钢筋的物体内部的深度）是正常的。 最小混凝土保护层通常由设计或建筑规范进行确定。 如果钢筋太靠近表面，可能会发生由腐蚀引起的早期失效。 具体的保护层深度可以用测量仪来测
36、量。 然而，碳化混凝土只有在有足够的湿气和氧气引起钢筋的电位腐蚀时才会变成耐久性问题。,34,One method of testing a structure for carbonation is to drill a fresh hole in the surface and then treat the cut surface with phenolphthalein indicator solution. This solution will turn pink when in contact with alkaline concrete, making it possible to
37、see the depth of carbonation. An existing hole is no good because the exposed surface will already be carbonated. 测试碳化结构的一种方法是在表面钻一个新的孔，然后用酚酞指示剂溶液处理切割表面。 与碱性混凝土接触时，该解决方案会变成粉红色，从而可以看到碳酸化深度。 现有的孔不好，因为暴露的表面已经被碳酸化了。,Chapter 6,35,Chlorides 氯化物 Chlorides, including sodium chloride, can promote the corrosi
38、on of embedded steel rebar if present in sufficiently high concentration. Chloride anions induce both localized corrosion (pitting corrosion) and generalized corrosion of steel reinforcements. For this reason, one should only use fresh raw water or potable water for mixing concrete, insure that the
39、coarse and fine aggregates do not contain chlorides, and not use admixtures that contain chlorides. 氯化物（包括氯化钠）可以促进嵌入式钢筋的腐蚀，如果其含量足够高。 氯阴离子引起局部腐蚀（点腐蚀）和钢筋腐蚀。 出于这个原因，应该只使用新鲜的原水或饮用水来搅拌混凝土，确保粗骨料和细骨料不含氯化物，不使用含氯化物的外加剂。,36,It was once common for calcium chloride to be used as an admixture to promote rapid se
40、t-up of the concrete. It was also mistakenly believed that it would prevent freezing. However, this practice has fallen into disfavor once the deleterious effects of chlorides became known. It should be avoided whenever possible. 氯化钙曾经作为混合物来促进混凝土的快速成型，这是很常见的。 它也被误认为会防止冻结。 然而，一旦氯化物的有害影响变得已知，这种做法就变得不受
41、欢迎。 应尽可能避免。,Chapter 6,37,The use of de-icing salts on roadways, used to reduce the freezing point of water, is probably one of the primary causes of premature failure of reinforced or prestressed concrete bridge decks, roadways, and parking garages. The use of epoxy-coated reinforcing bars and the a
42、pplication of cathodic protection has mitigated this problem to some extent. Also FRP rebars are known to be less susceptible to chlorides. Properly designed concrete mixtures that have been allowed to cure properly are effectively impervious to the effects of deicers. 在道路上使用除冰盐（用于降低水的冰点）可能是钢筋或预应力混凝
43、土桥面，道路和停车库过早失效的主要原因之一。 使用环氧涂层钢筋和阴极保护的应用已经在一定程度上缓解了这个问题。 已知纤维增强复合材料不易受氯化物影响。 正确设计的混凝土混合物已被正确固化，可有效地抵抗除冰器的影响。,38,Another important source of chloride ions is from sea water. Sea water contains by weight approximately 3.5wt.% salts. These salts include sodium chloride, magnesium sulfate (硫酸镁),calcium s
44、ulfate (硫酸钙), and bicarbonates. In water these salts dissociate in free ions (Na+, Mg2+, Cl-, SO42-, HCO3-) and migrate with the water into the capillaries of the concrete. Chloride ions are particularly aggressive for the corrosion of the carbon steel reinforcement bars and make up about 50% of the
45、se ions. 氯离子的另一个重要来源是海水。 海水含有约3.5的盐。 这些盐包括氯化钠，硫酸镁（硫酸镁），硫酸钙（硫酸钙）和碳酸氢盐。 在水中，这些盐在游离离子（Na +，Mg2 +，Cl-，SO42-，HCO3-）中解离并随水迁移到混凝土的毛细管中。 氯离子对碳钢钢筋的腐蚀特别具有侵蚀性，占这些离子的约50。,Chapter 6,39,In the 1960s and 1970s it was also relatively common for Magnesite, a chloride rich carbonate mineral, to be used as a floor-top
46、ping material. This was done principally as a levelling and sound attenuating layer. However it is now known that when these materials came into contact with moisture it produced a weak solution of hydrochloric acid due to the presence of chlorides in the magnesite. Over a period of time (typically
47、decades) the solution caused corrosion of the embedded steel rebars. This was most commonly found in wet areas or areas repeatedly exposed to moisture. 在二十世纪六十年代和七十年代，菱镁矿是一种富含氯化物的碳酸盐矿物，也被用作地面浇筑材料。 这主要是作为整平和消音层完成的。 然而，现在已知当这些材料与水分接触时，由于氯化镁存在于菱镁矿中，所以它产生了盐酸的弱溶液。 经过一段时间（通常为数十年），该解决方案导致嵌入式钢筋锈蚀。 这是最常见的潮湿地
48、区或反复暴露于潮湿的地区。,40,Words and Expression plate pleit n. 盘子，盆子;金属板 fiber faib n. 光纤;纤维，纤维物 patent ptnt n. 专利;专利品;专利权 composite kmpzit adj. 混合成的，综合成的; ductile dktail adj. 可延展的;有韧性的 coarse k:s adj. 粗鄙的;粗糙的;粗野的 hydrate haidreit n. 水合物; lattice ltis n. 格子框架,Chapter 6,41,roughen rfn v （使）变得粗糙，变得不平; cohesion
49、khi:n n. 凝聚，内聚;（各部的）结合 portlandite p:tlndait n. 氢氧钙石;羟钙石; neutral nju:trl adj. 中立的;（化学中）中性的 meteoric mi:tirik adj. 疾速的;令人眼花缭乱的 equilibriumi:kwilibrim n. 均衡；平静 magnitudemgnitju:d n. 大小；量级;光度 ingress inres n. 进入；入口；准许进入；入境 curvaturek:vt (r) n. 弯曲，数 曲率,42,distressdistres n. 危难，不幸；贫困；悲痛 impendimpend v. 迫近；悬空（impend的现在分词） specimenspesimn n. 样品，样本；标本 factored load n. 乘上系数的荷载，设计极限荷载 factored resistance n. 考虑阻力 thaw: n. 解冻；融雪 v. 使融解；使变得不拘束 penetratepentreit v 渗透；刺入；看透 serviceability s:visbiliti n. 可用性，适用性 sh