土木工程专业外语 Lesson15 Concrete placement.ppt

1、LESSON 15 Concrete Placement,Background Knowledge,所涉及到的课程：土木工程施工 混凝土的施工：钢筋混凝土结构中重要的分项工程施工，包括支设模板、混凝土的制备、运输、浇注与养护等工序。 本课文涉及到混凝土的浇注方法、混凝土的密实，竖向构件的浇筑、混凝土浇筑质量的检查。,The content of the text,The text can be divided into 6 parts.,Part 1 Introduction,The principles governing proper placement of concrete are:

2、Segregation must be avoided during all operations between the mixer and the point of placement, including final consolidation and finishing.,segregation ,seriein n. 离析 consolidation kn,slidein n. 密实，固结 finishing finii n. 完成，结束；最后的修整,Paragraph 1-5,The concrete must be thoroughly consolidated, and sho

3、uld fill all angles and corners of the forms. Where fresh concrete is placed on hardened concrete, a good bond must be developed.,Paragraph 1-5,form n. 模板,The temperature of fresh concrete must be controlled from the time of mixing through final placement, and protected after placement.,Paragraph 1-

4、5,冬季施工，混凝土浇筑后拆模前怎样进行保温？ 以前的做法是用草袋子覆盖， 现在是用塑料薄膜进行控温，然后在塑料薄膜内蒸汽加热，效果很好。,Concrete may be conveyed from a mixer to point of placement by any of a variety of methods and equipment, if properly transported to avoid segregation.,Part 2 Methods of Placing,Paragraph 6,convey knvei vt. 运输,Concrete pump,Select

5、ion of the most appropriate technique for economy depends on jobsite conditions, especially project size, equipment, and the contractors experience.,Paragraph 6,jobsite db,sait n. 工地现场,选择经济上最适宜的方法取决于工地现场的条件，尤其是项目规模、设备和承包商的经验。,In building construction, concrete usually is placed with hand or power-op

6、erated buggies; drop bottom buckets with a crane; inclined chutes; flexible and rigid pipe by pumping;,buggy bi n. 手推车、翻斗车 drop bottom bucket bkit 活底铲斗 chute u:t n. 斜槽；陡坡道,Paragraph 6,shotcrete, in which either dry materials and water are sprayed separately or mixed concrete is shot against the form

7、s; and for underwater placing, tremie chutes (closed flexible tubes).,shotcrete n. 喷浆混凝土 tremie chute 浇筑溜槽 tremie tremi n. 混凝土导管；漏斗管,Paragraph 6,Placing concrete under water,常用导管法，混凝土强度等级不低于C20，坍落度为1822cm。,concrete chute 混凝土运送溜槽,For mass concrete construction, side-dump cars on narrow-gage track or

8、belt conveyers may be used. For pavement, concrete may be placed by bucket from the swinging boom of a paving mixer, directly by dump truck or mixer truck, or indirectly by trucks into a spreader.,mass concrete 大块混凝土side-dump car 侧卸车 narrow gage track窄轨道 bucket bkit n. 铲斗 swinging boom 起重机回转臂 paving

9、 mixer 摊铺拌合机 spreader n. 建 撒布机,Paragraph 6,Even within the specified limits on slump and water-cementitious materials ratio, excess water must be avoided. In this context （关于这点）, excess water is present for the conditions of placing if evidence（迹象） of water rise (vertical segregation) or water flow

10、(horizontal segregation) occurs.,Part 3 Excess Water,Paragraph 7,specified limits on slump 坍落度规限 Method of test for slump of concrete slump n. 暴跌；衰退；消沉 cementitious ,si:mentis adj. 胶结的，似水泥的,就这个问题，如果明显的有水上升（竖向离析）或水流动（水平离析）发生，就表明在混凝土浇筑时有过剩水。,Excess water also tends to aggravate surface defects by incr

11、eased leakage through form openings. The result may be honeycomb, variations in color, or soft spots at the surface.,Paragraph 7,通过从模板开口处渗漏的增长，过剩水也会导致导致骨料表面缺陷。,In vertical formwork, water rise causes weak planes between each layer deposited. In addition to the deleterious structural effect, such pla

12、nes, when hardened, contain voids through which water may pass.,deposited adj. 存放的；堆积的 deleterious ,delitiris adj. 有毒的，有害的 Voids n. 空洞，孔洞；空隙率,Paragraph 8,In horizontal elements, such as floor slabs, excess water rises and causes a weak laitance layer at the top. This layer suffers from low strength,

13、 low abrasion resistance, high shrinkage, and generally poor quality.,laitance leitns n. 水泥浆 abrasion brein n. 磨损；擦伤；磨耗,Paragraph 9,The purpose of consolidation is to eliminate voids of air and to ensure intimate complete contact of the concrete with the surfaces of the forms and the reinforcement.,

14、Part 4 Consolidation,Paragraph 10,intimate intimt adj. 亲密的；精通的,Intense vibration, however, may also reduce the volume of desirable entrained air; but this reduction can be compensated by adjustment of the mix proportions.,Paragraph 10,entrained air 携入的空气 compensated kmpn,setv. 补偿（compensate的过去式）；偿还

15、mix proportions： 混合比 ；配合比,Powered internal vibrators are usually used to achieve consolidation. For thin slabs, however, high-quality, low-slump concrete can be effectively consolidated, without excess water, by mechanical surface vibrators.,surface vibrators 建公路 平面振动器,Paragraph 11,For precast eleme

16、nts in rigid external vibration is highly effective. External vibration is also effective with in-place forms, but should not be used unless the formwork is specially designed for the temporary increase in internal pressures to full fluid head plus the impact of the vibrator.,in-place inpleis 就地；原状；

17、在位,对流体水头加上振捣器的冲击所产生的临时增长的内部压力，进行了特殊设计,Paragraph 11,沈阳音乐学院 高支模板坍塌事故,Except in certain paving operations, vibration of the reinforcement should be avoided. Although it is effective, the necessary control to prevent overvibration is difficult.,Overvibration n. 过度振动,Paragraph 12,Also, when concrete is p

18、laced in several lifts（升距） of layers, vibration of vertical rebars passing into partly set concrete below may be harmful.,对通过下部半凝固混凝土的竖向钢筋进行振捣，也是有害的。,Paragraph 12,Note, however, that revibration of concrete before the final set, under controlled conditions, can improve concrete strength markedly and

19、 reduce surface voids. This technique is too difficult to control for general use on field-cast vertical elements, but it is very effective in finishing slabs with powered vibrating equipment.,Paragraph 12,finishing 表面加工,The interior of columns is usually congested; it contains a large volume of rei

20、nforcing steel compared with the volume of concrete, and has a large height compared with its cross-sectional dimensions.,Part 5 Concreting Vertical Elements,Paragraph 13 Columns,congested kndestid adj. 堵塞的，拥挤的,Therefore, though columns should be continuously cast, the concrete should be placed in 2

21、-to 4-ft-deep increments and consolidated with internal vibrators. These should be lifted after each increment has been vibrated.,Paragraph 13,increment inkrimnt n. 增加；增量,If delay occurs in concrete supply before a column has been completed, every effort should be made to avoid a cold joint. When th

22、e remainder of the column is cast, the first increment should be small, and should be vibrated to penetrate the previous portion slightly.,Paragraph 13,cold joint 虚焊；冷缝 remainder rimeind n. 余数，残余；剩余 penetrate penitreit vt. 渗透；穿透；洞察,In all columns and reinforced narrow walls, concrete placing should

23、begin with 2 to 4 in of grout. Otherwise, loose stone will collect at the bottom, resulting in the formation of honeycomb. This grout should be proportioned for about the same slump as the concrete or slightly more, but at the same or lower water-cementitious material ratio.,Paragraph 14 Wall,grout

24、raut n. 水泥浆；薄浆,这水泥浆的配比应设计成与混凝土有相同的或稍高的塌落度，有相同的或稍低的水灰比。,(Some engineers prefer to start vertical placement with a mix having the same proportions of water, cement, and fine aggregate, but with one-half the quantity of coarse aggregate, as in the design mix, and to place a starting layer 6 to 12 in de

25、ep. ),Paragraph 14,fine aggregate 细骨料，细集料 coarse aggregate 粗集料；建 粗骨料,When concrete is placed for walls, the only practicable means to avoid segregation is to place no more than a 24-in layer in one pass. Each layer should be vibrated separately and kept nearly level.,Paragraph 14,one pass 进行一轮 进行一轮,

26、For walls deeper than 4 ft, concrete should not be placed through vertical. The concrete should not fall free more than 4 ft or segregation will occur, with the coarse aggregate ricocheting off the forms to lodge on one side.,Paragraph 15,ricochet rikeit, ,rikeit vi. 跳飞 vt. 使跳飞 ricochet off 弹离 lodge

27、 ld vt. 寄存；借住；嵌入,（浇筑时），混凝土自由落体的高度不超过4英尺，否则就会发生离析，粗骨料从模板弹起，嵌在模板的一边。,Successive layers after the initial layer should be penetrated by internal vibrators for a depth of about 4 to 6 in to ensure complete integration at the surface of each layer. Deeper penetration can be beneficial (revibration), but

28、control under variable jobsite conditions is too uncertain for recommendation of this practice for general use.,Paragraph 15,successive layers 连续层,初始层后连续（浇筑）的各层，应该用内部振捣器深入下层4至6英寸，以保证在每层结合面处的整体性。,The results of poor placement in walls are frequently observed: sloping layer lines; honeycombs, leaking,

29、 if water is present; and, if cores are taken at successive heights, up to a 50% reduction in strength from bottom to top. Some precautions necessary to avoid these ill effects are:,Paragraph 16-19,层面倾斜；如果有水，则是蜂窝、渗漏，；若沿高度连续取芯，从底部到顶部混凝土强度降低高达50%。,precaution 美prknn. 预防，预防措施,Do not move concrete latera

30、lly with vibrators. For deep, long walls, reduce the slump for upper layers 2 to 3 in below the slump for the starting layer. On any delay between placing of layers, vibrate the concrete thoroughly at the interface.,Paragraph 16-19,对于深、长墙，与开始层、下部混凝土的塌落度相比，降低上层混凝土的塌落度2-3英寸。,Concrete should be inspect

31、ed for the owner before, during, and after casting. Before concrete is placed, the formwork must be free of ice and debris and properly coated with bond-breaker oil. The rebars must be in place, properly supported to bear any traffic they will receive during concrete placing.,Part 6 Inspection of Co

32、ncrete Placement,Paragraph 120,debris deibri: n. 碎片，残骸 bond breaker oil 黏合分隔材料油,Conduit, inserts, and other items to be embedded must be in position, fixed against displacement. Construction personnel should be available, usually carpenters, bar placers and other trades, if piping or electrical cond

33、uit is to be embedded, to act as form watchers and to reset any rebars, conduit, or piping displaced.,Paragraph 20,conduit kndit n. 导管；导水管；沟渠 embedimbed vt. 栽种；使嵌入， inserts n. 镶嵌件,As concrete is cast, the slump of the concrete must be observed and regulated within prescribed limits, or the specified strengths based on the expected slump may be reduced.,Paragraph 21,prescribe priskraib v. 规定,当混凝土浇注时，必须观察并控制混凝土的塌落度在控制限值之内，否则基于预定塌落度的规定强度可能会降低。,An inspector of placing who is also respo