建筑施工混凝土裂縫的預防與處理外文翻譯

1、 南 京 理 工 大 學 紫 金 學 院畢業(yè)設計(論文)外文資料翻譯系： 機械系 專 業(yè)： 土木工程 (用外文寫)外文出處： canadian journal of civi engineering 附 件： 1.外文資料翻譯譯文；2.外文原文。 指導教師評語： 簽名： 年 月 日注：請將該封面與附件裝訂成冊。附件1：外文資料翻譯譯文建筑施工混凝土裂縫的預防與處理混凝土的裂縫問題是一個普遍存在而又難于解決的工程實際問題，本文對混凝土工程中常見的一些裂縫問題進行了探討分析，并針對具體情況提出了一些預防、處理措施。關鍵詞：混凝土 裂縫 預防 處理前言混凝土是一種由砂石骨料、水泥、水及其他外加材料混

2、合而形成的非均質(zhì)脆性材料。由于混凝土施工和本身變形、約束等一系列問題，硬化成型的混凝土中存在著眾多的微孔隙、氣穴和微裂縫，正是由于這些初始缺陷的存在才使混凝土呈現(xiàn)出一些非均質(zhì)的特性。微裂縫通常是一種無害裂縫，對混凝土的承重、防滲及其他一些使用功能不產(chǎn)生危害。但是在混凝土受到荷載、溫差等作用之后，微裂縫就會不斷的擴展和連通，最終形成我們?nèi)庋劭梢姷暮暧^裂縫，也就是混凝土工程中常說的裂縫?；炷两ㄖ蜆嫾ǔ６际菐Эp工作的，由于裂縫的存在和發(fā)展通常會使內(nèi)部的鋼筋等材料產(chǎn)生腐蝕，降低鋼筋混凝土材料的承載能力、耐久性及抗?jié)B能力，影響建筑物的外觀、使用壽命，嚴重者將會威脅到人們的生命和財產(chǎn)安全。很多工程的

3、失事都是由于裂縫的不穩(wěn)定發(fā)展所致。近代科學研究和大量的混凝土工程實踐證明，在混凝土工程中裂縫問題是不可避免的，在一定的范圍內(nèi)也是可以接受的，只是要采取有效的措施將其危害程度控制在一定的范圍之內(nèi)。鋼筋混凝土規(guī)范也明確規(guī)定：有些結構在所處的不同條件下，允許存在一定寬度的裂縫。但在施工中應盡量采取有效措施控制裂縫產(chǎn)生，使結構盡可能不出現(xiàn)裂縫或盡量減少裂縫的數(shù)量和寬度，尤其要盡量避免有害裂縫的出現(xiàn)，從而確保工程質(zhì)量?；炷亮芽p產(chǎn)生的原因很多，有變形引起的裂縫：如溫度變化、收縮、膨脹、不均勻沉陷等原因引起的裂縫；有外載作用引起的裂縫；有養(yǎng)護環(huán)境不當和化學作用引起的裂縫等等。在實際工程中要區(qū)別對待，根據(jù)實

4、際情況解決問題?；炷凉こ讨谐Ｒ娏芽p及預防:1.干縮裂縫及預防干縮裂縫多出現(xiàn)在混凝土養(yǎng)護結束后的一段時間或是混凝土澆筑完畢后的一周左右。水泥漿中水分的蒸發(fā)會產(chǎn)生干縮，且這種收縮是不可逆的。干縮裂縫的產(chǎn)生主要是由于混凝土內(nèi)外水分蒸發(fā)程度不同而導致變形不同的結果：混凝土受外部條件的影響，表面水分損失過快，變形較大，內(nèi)部濕度變化較小變形較小，較大的表面干縮變形受到混凝土內(nèi)部約束，產(chǎn)生較大拉應力而產(chǎn)生裂縫。相對濕度越低，水泥漿體干縮越大，干縮裂縫越易產(chǎn)生。干縮裂縫多為表面性的平行線狀或網(wǎng)狀淺細裂縫，寬度多在0.05-0.2mm之間，大體積混凝土中平面部位多見，較薄的梁板中多沿其短向分布。干縮裂縫通常會

5、影響混凝土的抗?jié)B性，引起鋼筋的銹蝕，影響混凝土的耐久性，在水壓力的作用下會產(chǎn)生水力劈裂影響混凝土的承載力等等?；炷粮煽s主要和混凝土的水灰比、水泥的成分、水泥的用量、集料的性質(zhì)和用量、外加劑的用量等有關。主要預防措施：一是選用收縮量較小的水泥，一般采用中低熱水泥和粉煤灰水泥，降低水泥的用量。二是混凝土的干縮受水灰比的影響較大，水灰比越大，干縮越大，因此在混凝土配合比設計中應盡量控制好水灰比的選用，同時摻加合適的減水劑。三是嚴格控制混凝土攪拌和施工中的配合比，混凝土的用水量絕對不能大于配合比設計所給定的用水量。四是加強混凝土的早期養(yǎng)護，并適當延長混凝土的養(yǎng)護時間。冬季施工時要適當延長混凝土保溫覆

6、蓋時間，并涂刷養(yǎng)護劑養(yǎng)護。五是在混凝土結構中設置合適的收縮縫。2.塑性收縮裂縫及預防塑性收縮是指混凝土在凝結之前，表面因失水較快而產(chǎn)生的收縮。塑性收縮裂縫一般在干熱或大風天氣出現(xiàn)，裂縫多呈中間寬、兩端細且長短不一，互不連貫狀態(tài)。較短的裂縫一般長20-30cm，較長的裂縫可達2-3m，寬1-5mm.其產(chǎn)生的主要原因為：混凝土在終凝前幾乎沒有強度或強度很小，或者混凝土剛剛終凝而強度很小時，受高溫或較大風力的影響，混凝土表面失水過快，造成毛細管中產(chǎn)生較大的負壓而使混凝土體積急劇收縮，而此時混凝土的強度又無法抵抗其本身收縮，因此產(chǎn)生龜裂。影響混凝土塑性收縮開裂的主要因素有水灰比、混凝土的凝結時間、環(huán)境

7、溫度、風速、相對濕度等等。主要預防措施：一是選用干縮值較小早期強度較高的硅酸鹽或普通硅酸鹽水泥。二是嚴格控制水灰比，摻加高效減水劑來增加混凝土的坍落度和和易性，減少水泥及水的用量。三是澆筑混凝土之前，將基層和模板澆水均勻濕透。四是及時覆蓋塑料薄膜或者潮濕的草墊、麻片等，保持混凝土終凝前表面濕潤，或者在混凝土表面噴灑養(yǎng)護劑等進行養(yǎng)護。五是在高溫和大風天氣要設置遮陽和擋風設施，及時養(yǎng)護。3.沉陷裂縫及預防沉陷裂縫的產(chǎn)生是由于結構地基土質(zhì)不勻、松軟或回填土不實或浸水而造成不均勻沉降所致；或者因為模板剛度不足，模板支撐間距過大或支撐底部松動等導致，特別是在冬季，模板支撐在凍土上，凍土化凍后產(chǎn)生不均勻沉

8、降，致使混凝土結構產(chǎn)生裂縫。此類裂縫多為深進或貫穿性裂縫，其走向與沉陷情況有關，一般沿與地面垂直或呈30-45角方向發(fā)展，較大的沉陷裂縫，往往有一定的錯位，裂縫寬度往往與沉降量成正比關系。裂縫寬度受溫度變化的影響較小。地基變形穩(wěn)定之后，沉陷裂縫也基本趨于穩(wěn)定。主要預防措施：一是對松軟土、回填土地基在上部結構施工前應進行必要的夯實和加固。二是保證模板有足夠的強度和剛度，且支撐牢固，并使地基受力均勻。三是防止混凝土澆灌過程中地基被水浸泡。四是模板拆除的時間不能太早，且要注意拆模的先后次序。五是在凍土上搭設模板時要注意采取一定的預防措施。4.溫度裂縫及預防溫度裂縫多發(fā)生在大體積混凝土表面或溫差變化較

9、大地區(qū)的混凝土結構中?；炷翝仓螅谟不^程中，水泥水化產(chǎn)生大量的水化熱，（當水泥用量在350-550 kg/m3，每立方米混凝土將釋放出17500-27500kj的熱量，從而使混凝土內(nèi)部溫度升達70左右甚至更高）。由于混凝土的體積較大，大量的水化熱聚積在混凝土內(nèi)部而不易散發(fā)，導致內(nèi)部溫度急劇上升，而混凝土表面散熱較快，這樣就形成內(nèi)外的較大溫差，較大的溫差造成內(nèi)部與外部熱脹冷縮的程度不同，使混凝土表面產(chǎn)生一定的拉應力。當拉應力超過混凝土的抗拉強度極限時，混凝土表面就會產(chǎn)生裂縫，這種裂縫多發(fā)生在混凝土施工中后期。在混凝土的施工中當溫差變化較大，或者是混凝土受到寒潮的襲擊等，會導致混凝土表面溫度

10、急劇下降，而產(chǎn)生收縮，表面收縮的混凝土受內(nèi)部混凝土的約束，將產(chǎn)生很大的拉應力而產(chǎn)生裂縫，這種裂縫通常只在混凝土表面較淺的范圍內(nèi)產(chǎn)生。溫度裂縫的走向通常無一定規(guī)律，大面積結構裂縫?？v橫交錯；梁板類長度尺寸較大的結構，裂縫多平行于短邊；深入和貫穿性的溫度裂縫一般與短邊方向平行或接近平行，裂縫沿著長邊分段出現(xiàn)，中間較密。裂縫寬度大小不一，受溫度變化影響較為明顯，冬季較寬，夏季較窄。高溫膨脹引起的混凝土溫度裂縫是通常中間粗兩端細，而冷縮裂縫的粗細變化不太明顯。此種裂縫的出現(xiàn)會引起鋼筋的銹蝕，混凝土的碳化，降低混凝土的抗凍融、抗疲勞及抗?jié)B能力等。主要預防措施：一是盡量選用低熱或中熱水泥，如礦渣水泥、粉煤

11、灰水泥等。二是減少水泥用量，將水泥用量盡量控制在450kg/m3以下。三是降低水灰比，一般混凝土的水灰比控制在0.6以下。四是改善骨料級配，摻加粉煤灰或高效減水劑等來減少水泥用量，降低水化熱。五是改善混凝土的攪拌加工工藝，降低混凝土的澆筑溫度。六是在混凝土中摻加一定量的具有減水、增塑、緩凝等作用的外加劑，改善混凝土拌合物的流動性、保水性，降低水化熱，推遲熱峰的出現(xiàn)時間。七是高溫季節(jié)澆筑時可以采用搭設遮陽板等輔助措施控制混凝土的溫升，降低澆筑混凝土的溫度。八是大體積混凝土的溫度應力與結構尺寸相關，混凝土結構尺寸越大，溫度應力越大，因此要合理安排施工工序，分層、分塊澆筑，以利于散熱，減小約束。九是

12、在大體積混凝土內(nèi)部設置冷卻管道，通冷水或者冷氣冷卻，減小混凝土的內(nèi)外溫差。十是加強混凝土溫度的監(jiān)控，及時采取冷卻、保護措施。十一是預留溫度收縮縫。十二是減小約束，澆筑混凝土前宜在基巖和老混凝土上鋪設5mm左右的砂墊層或使用瀝青等材料涂刷。十三是加強混凝土養(yǎng)護，混凝土澆筑后，及時用濕潤的草簾、麻片等覆蓋，并注意灑水養(yǎng)護，適當延長養(yǎng)護時間，保證混凝土表面緩慢冷卻。在寒冷季節(jié)，混凝土表面應設置保溫措施，以防止寒潮襲擊。十四是混凝土中配置少量的鋼筋或者摻入纖維材料將混凝土的溫度裂縫控制在一定的范圍之內(nèi)。5.化學反應引起的裂縫及預防堿骨料反應裂縫和鋼筋銹蝕引起的裂縫是鋼筋混凝土結構中最常見的由于化學反應

13、而引起的裂縫。混凝土拌和后會產(chǎn)生一些堿性離子，這些離子與某些活性骨料產(chǎn)生化學反應并吸收周圍環(huán)境中的水而體積增大，造成混凝土酥松、膨脹開裂。這種裂縫一般出現(xiàn)中混凝土結構使用期間，一旦出現(xiàn)很難補救，因此應在施工中采取有效措施進行預防。主要的預防措施：一是選用堿活性小的砂石骨料。二是選用低堿水泥和低堿或無堿的外加劑。三是選用合適的摻和料抑制堿骨料反應。由于混凝土澆筑、振搗不良或者是鋼筋保護層較薄，有害物質(zhì)進入混凝土使鋼筋產(chǎn)生銹蝕，銹蝕的鋼筋體積膨脹，導致混凝土脹裂，此種類型的裂縫多為縱向裂縫，沿鋼筋的位置出現(xiàn)。通常的預防措施有：一是保證鋼筋保護層的厚度。二是混凝土級配要良好。三是混凝土澆注要振搗密實

14、。四是鋼筋表層涂刷防腐涂料。 出自加拿大土木工程學報附件2：外文原文（復印件）building construction concrete crack ofprevention and processingabstractthe crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack prob

15、lem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure. keyword:concrete crack prevention processingforeword concretes ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition mat

16、erial of quality brittleness not and all material.because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make

17、 the concrete present one some not and all the characteristic of quality.the tiny crack is a kind of harmless crack and accept concrete heavy, defend shen and a little bit other use function not a creation to endanger.but after the concrete be subjected to lotus carry, difference in temperature etc.

18、 function, tiny crack would continuously of expand with connect, end formation we can see without the aid of instruments of macro view the crack be also the crack that the concrete often say in the engineering. concrete building and gou piece usually all take sewer to make of, because of crack of ex

19、istence and development usually make inner part of reinforcing bar etc. material creation decay, lower reinforced concrete material of loading ability, durable and anti- shen ability, influence building of external appearance, service life, severity will threat arrive peoples life and property safet

20、y.a lot of all of crash of engineerings is because of the unsteady development of the crack with the result that.modern age science research with a great deal of of the concrete engineering practice certificate, in the concrete engineering crack problem is ineluctable, also acceptable in certainly o

21、f the scope just need to adopt valid of measure will it endanger degree control at certain of scope inside.the reinforced concrete norm is also explicit provision:some structure at place of dissimilarity under the condition allow existence certain the crack of width.but at under construction should

22、as far as possible adopt a valid measure control crack creation, make the structure dont appear crack possibly or as far as possible decrease crack of amount and width, particularly want to as far as possible avoid harmful crack of emergence, insure engineering quality thus. concrete crack creation

23、of the reason be a lot of and have already transformed to cause of crack:such as temperature variety, constringency, inflation, the asymmetry sink to sink etc. reason cause of crack;have outside carry the crack that the function cause;protected environment not appropriate the crack etc. caused with

24、chemical effect.want differentiation to treat in the actual engineering, workout a problem according to the actual circumstance. in the concrete engineering the familiar crack and the prevention 1.stem suo crack and prevention stem the suo crack much appear after the concrete protect be over of a pe

25、riod of time or concrete sprinkle to build to complete behind of around a week.in the cement syrup humidity of evaporate would creation stem suo, and this kind of constringency is cant negative.stem suo crack of the creation be main is because of concrete inside outside humidity evaporate degree dis

26、similarity but cause to transform dissimilarity of result:the concrete is subjected to exterior condition of influence, surface humidity loss lead quick, transform bigger, inner part degree of humidity variety smaller transform smaller, bigger surface stem the suo transform to be subjected to concre

27、te inner part control, creation more big pull should dint but creation crack.the relative humidity is more low, cement syrup body stem suo more big, stem the suo crack be more easy creation.stem the suo crack is much surface parallel lines form or the net shallow thin crack, width many between 0.05-

28、0.2 mm, the flat surface part much see in the big physical volume concrete and follow it more in thinner beam plank short to distribute.stem suo crack usually the anti- shen of influence concrete, cause the durable of the rust eclipse influence concrete of reinforcing bar, under the function of the

29、water pressure dint would creation the water power split crack influence concrete of loading dint etc.concrete stem the suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. r

30、elevant. main prevention measure:while being to choose to use the constringency quantity smaller cement, general low hot water mire and powder ash from stove cement in the adoption, lower the dosage of cement.two is a concrete of stem the suo be subjected to water ash ratio of influence more big, wa

31、ter ash ratio more big, stem suo more big, so in the concrete match the ratio the design should as far as possible control good water ash ratio of choose to use, the chan add in the meantime accommodation of reduce water.three is strict control concrete mix blend with under construction of match rat

32、io, use of concrete water quantity absolute cant big in match ratio design give settle of use water quantity.four is the earlier period which strengthen concrete to protect, and appropriate extension protect of concrete time.winter construction want to be appropriate extension concrete heat preserva

33、tion to overlay time, and tu2 shua protect to protect.five is a constitution the accommodation is in the concrete structure of the constringency sew. 2.the su constringency crack and prevention su constringency is the concrete is before condense, surface because of lose water quicker but creation of

34、 constringency.the su constringency crack is general at dry heat or strong wind the weather appear, cracks much presenting in the center breadth, both ends be in the centerthin and the length be different, with each other not coherent appearance.shorter crack general long 20-30 cm, the longer crack

35、can reach to a 2-3 m, breadth 1-5 mm.it creation of main reason is:the concrete is eventually almost having no strength or strength before the ning very small, perhaps concrete just eventually ning but strength very hour, be subjected to heat or compare strong wind dint of influence, the concrete su

36、rface lose water to lead quick, result in in the capillary creation bigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again cant resist its constringency, therefore creation cracked.the influence concrete su constringency open

37、the main factor of crack to have water ash ratio, concrete of condense time, environment temperature, wind velocity, relative humidity.etc. main prevention measure:one is choose to use stem the suo value smaller higher huo sour salt of the earlier period strength or common the huo sour brine mire.tw

38、o is strict the control water ash ratio, the chan add to efficiently reduce water to increment the collapse of concrete fall a degree and with easy, decrease cement and water of dosage.three is to sprinkle before building concrete, water basic level and template even to soak through.four is in time

39、to overlay the perhaps damp grass mat of the plastics thin film, hemp slice etc., keep concrete eventually before the ning surface is moist, perhaps spray to protect etc. to carry on protect in the concrete surface.five is in the heat and strong wind the weather to want to establish to hide sun and

40、block breeze facilities, protect in time. 3.sink to sink crack and prevention the creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in the asymmetry sink to decline with the re

41、sult that;perhaps because of template just degree shortage, the template propped up to once be apart from big or prop up bottom loose move etc. to cause, especially at winter, the template prop up at jelly soil up, jelly the soil turn jelly empress creation asymmetry to sink to decline and cause con

42、crete structure creation crack.this kind crack many is deep enter or pierce through sex crack, it alignment have something to do with sinking to sink a circumstance, general follow with ground perpendicular or present 30 s-45 cape direction development, bigger sink to sink crack, usually have certai

43、n of wrong, crack width usually with sink to decline quantity direct proportion relation.crack width under the influence of temperature variety smaller.the foundation after transform stability sink to sink crack also basic tend in stability. main prevention measure:one is rightness loose soft soil,

44、return to fill soil foundation a construction at the upper part structure front should carry on necessity of hang solid with reinforce.two is the strength that assurance template is enough and just degree, and prop up firm, and make the foundation be subjected to dint even.three is keep concrete fro

45、m sprinkle infusing the foundation in the process is soak by water.four is time that template tore down to cant be too early, and want to notice to dismantle a mold order of sequence.five is at jelly soil top take to establish template to notice to adopt certain of prevention measure. 4.temperature

46、crack and prevention temperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete compare the earth area of the concrete structure.concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great de

47、al of of water turn hot, .(be the cement dosage is in the 350-550 kg/m 3, each sign square the rice concrete will release a calories of 17500-27500 kj and make concrete internal thus the temperature rise to reach to 70 or so even higher)because the physical volume of concrete be more big, a great de

48、al of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part an

49、d exterior hot the degree of the bulge cold suo dissimilarity, make concrete surface creation certain of pull should dint.when pull should dint exceed the anti- of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete und

50、er construction period.in the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concre

51、te be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crack usually just in more shallow scope of the concrete surface creation. the alignment of the temperature crack usually none settle regulation, big area structure the crack oft

52、en maneuver interleave;the size bigger structure of the beam plank length, the crack run parallel with short side more;thorough with pierce through sex of temperature crack general and short side direction parallelism or close parallelism, crack along long side cent the segment appear, in the center

53、 more airtight.crack width the size be different, be subjected to temperature variety influence more obvious, winter compare breadth, summer more narrow.the concrete temperature crack that the heat inflation cause is usually in the center the thick both ends be thin, but cold suo crack of thick thin

54、 variety not too obvious.the emergence of the this kind crack will cause the rust eclipse of reinforcing bar, the carbonization of concrete, the anti- jelly which lower concrete melt, anti- tired and anti- shen ability etc. main prevention measure:one is as far as possible choose to use low hot or m

55、edium hot water mire, like mineral residue cement, powder ash from stove cement.etc.two is a decrease cement dosage, cement dosage as far as possible the control is in the 450 kg/m 3 following.three is to lower water ash ratio, water ash of the general concrete ratio control below 0.6.four is improv

56、ement the bone anticipate class to go together with, the chan add powder ash from stove or efficiently reduce water etc. to come to reduce cement dosage and lower water to turn hot.five is an improvement concrete of mix blend to process a craft, lower sprinkle of concrete to build temperature.six is

57、 the in addition that the chan add a have of fixed amount to reduce water and increase su, slow ning etc. function in the concrete, improvement the concrete mix to match a thing of mobility, protect water, lower water to turn hot, postpone hot feng of emergence time.seven is the heat season sprinkle

58、 to build can the adoption take to establish to hide sun plank etc. assistance measure control concrete of wen sheng, lower to sprinkle temperature of build the concrete.eight is the temperature of big physical volume concrete should the dint relate to structure size, concrete structure size more big, temperature should dint more big, so want reasonable arrangement construction work preface, layering, cent the piece sprinkle to build, for the convenience of in spread hot, let up co