1、LESSON 15 Concrete Placement,Background Knowledge,所涉及到的課程：土木工程施工 混凝土的施工：鋼筋混凝土結(jié)構(gòu)中重要的分項(xiàng)工程施工，包括支設(shè)模板、混凝土的制備、運(yùn)輸、澆注與養(yǎng)護(hù)等工序。 本課文涉及到混凝土的澆注方法、混凝土的密實(shí)，豎向構(gòu)件的澆筑、混凝土澆筑質(zhì)量的檢查。,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. 離析 consolidation kn,slidein n. 密實(shí)，固結(jié) finishing finii n. 完成，結(jié)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，混凝土澆筑后拆模前怎樣進(jìn)行保溫？ 以前的做法是用草袋子覆蓋， 現(xiàn)在是用塑料薄膜進(jìn)行控溫，然后在塑料薄膜內(nèi)蒸汽加熱，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. 運(yùn)輸,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. 工地現(xiàn)場(chǎng),選擇經(jīng)濟(jì)上最適宜的方法取決于工地現(xiàn)場(chǎng)的條件，尤其是項(xiàng)目規(guī)模、設(shè)備和承包商的經(jīng)驗(yàn)。,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. 手推車、翻斗車 drop bottom bucket bkit 活底鏟斗 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. 噴漿混凝土 tremie chute 澆筑溜槽 tremie tremi n. 混凝土導(dǎo)管；漏斗管,Paragraph 6,Placing concrete under water,常用導(dǎo)管法，混凝土強(qiáng)度等級(jí)不低于C20，坍落度為1822cm。,concrete chute 混凝土運(yùn)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 大塊混凝土side-dump car 側(cè)卸車 narrow gage track窄軌道 bucket bkit n. 鏟斗 swinging boom 起重機(jī)回轉(zhuǎn)臂 paving

9、 mixer 攤鋪拌合機(jī) spreader n. 建 撒布機(jī),Paragraph 6,Even within the specified limits on slump and water-cementitious materials ratio, excess water must be avoided. In this context （關(guān)于這點(diǎn)）, excess water is present for the conditions of placing if evidence（跡象） of water rise (vertical segregation) or water flow

10、(horizontal segregation) occurs.,Part 3 Excess Water,Paragraph 7,specified limits on slump 坍落度規(guī)限 Method of test for slump of concrete slump n. 暴跌；衰退；消沉 cementitious ,si:mentis adj. 膠結(jié)的，似水泥的,就這個(gè)問(wèn)題，如果明顯的有水上升（豎向離析）或水流動(dòng)（水平離析）發(fā)生，就表明在混凝土澆筑時(shí)有過(guò)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,通過(guò)從模板開(kāi)口處滲漏的增長(zhǎng)，過(guò)剩水也會(huì)導(dǎo)致導(dǎo)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；堆積的 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. 水泥漿 abrasion brein n. 磨損；擦傷；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. 親密的；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 攜入的空氣 compensated kmpn,setv. 補(bǔ)償（compensate的過(guò)去式）；償還

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 平面振動(dòng)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；原狀；

17、在位,對(duì)流體水頭加上振搗器的沖擊所產(chǎn)生的臨時(shí)增長(zhǎng)的內(nèi)部壓力，進(jìn)行了特殊設(shè)計(jì),Paragraph 11,沈陽(yáng)音樂(lè)學(xué)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. 過(guò)度振動(dòng),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.,對(duì)通過(guò)下部半凝固混凝土的豎向鋼筋進(jìn)行振搗，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，擁擠的,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 虛焊；冷縫 remainder rimeind n. 余數(shù)，殘余；剩余 penetrate penitreit vt. 滲透；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. 水泥漿；薄漿,這水泥漿的配比應(yīng)設(shè)計(jì)成與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 細(xì)骨料，細(xì)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 進(jìn)行一輪 進(jìn)行一輪,

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. 跳飛 vt. 使跳飛 ricochet off 彈離 lodge

27、 ld vt. 寄存；借住；嵌入,（澆筑時(shí)），混凝土自由落體的高度不超過(guò)4英尺，否則就會(huì)發(fā)生離析，粗骨料從模板彈起，嵌在模板的一邊。,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 連續(xù)層,初始層后連續(xù)（澆筑）的各層，應(yīng)該用內(nèi)部振搗器深入下層4至6英寸，以保證在每層結(jié)合面處的整體性。,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,層面傾斜；如果有水，則是蜂窩、滲漏，；若沿高度連續(xù)取芯，從底部到頂部混凝土強(qiáng)度降低高達(dá)50%。,precaution 美prknn. 預(yù)防，預(yù)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,對(duì)于深、長(zhǎng)墻，與開(kāi)始層、下部混凝土的塌落度相比，降低上層混凝土的塌落度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，殘骸 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. 導(dǎo)管；導(dǎo)水管；溝渠 embedimbed vt. 栽種；使嵌入， inserts n. 鑲嵌件,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. 規(guī)定,當(dāng)混凝土澆注時(shí)，必須觀察并控制混凝土的塌落度在控制限值之內(nèi)，否則基于預(yù)定塌落度的規(guī)定強(qiáng)度可能會(huì)降低。,An inspector of placing who is also respo