外文翻譯--混凝土裂縫的成因、預(yù)防及處理

1、<p>　　The causes, prevention and treatment of cracks in concrete</p><p>　　Abstract: </p><p>　　In the building construction concrete cracks a quality common problem, the causes of cracks in

2、concrete, prior prevention, as well as after the repair process is a more common phenomenon in the process of building production, should be taken seriously enough. The concrete is a brittle material of a gravel aggregat

3、e, cement, water and other additional material formed by mixing a non-homogeneous. Concrete construction and deformation constraints and a series of problems, there are a large number o</p><p>　　Keywords: ca

4、uses of cracks in concrete preventive treatment</p><p>　　In building construction, concrete cracks is a widespread problem, cracks solution is a more difficult problem. Cracks in concrete reasons are manifol

5、d, deformation: such as contraction, expansion, settlement and other causes cracks; external load caused by: improper maintenance of concrete; cracks caused by the external additive problems.</p><p>　　Concre

6、te cracks, if not prevention measures to solve, extending its further development will lead to the internal reinforcement corrosive, reducing the carrying capacity of the reinforced concrete structure, impermeability, du

7、rability useful life, and even affect people's lives and property safety . Crack is impossible to completely eliminate the engineering specification expressly provides some structure in which the different conditions

8、, allowing the existence of a certain width and depth of t</p><p>　　1.Causes and types of concrete cracks</p><p>　　The concrete is a brittle material of a gravel aggregate, cement, water and oth

9、er additional material formed by mixing a non-homogeneous. Hardening molding concrete concrete construction and deformation constraints there are a large number of micro-porosity, cavitation and micro-cracks, precisely b

10、ecause of the existence of these initial defects before the concrete showing some heterogeneity characteristics . Micro-cracks is usually a harmless cracks on concrete load-bearing, seepage and use the</p><p&g

11、t;　　Many cracks in concrete cracks caused by deformation: such as temperature change, shrinkage, expansion, uneven subsidence caused cracks; external load induced cracks; cracks caused by improper conservation of the env

12、ironment and chemical action, etc. .</p><p>　　Common cracks in the concrete are the following: (1) shrinkage cracks; ② plastic shrinkage cracking; (3) settlement cracks; ④ temperature cracks; ⑤ chemical reac

13、tion caused by cracks.</p><p>　　2.Concrete cracks and prevention</p><p>　　2.1 Shrinkage cracks and prevention of</p><p>　　Shrinkage cracks appear in a week or so after the end of t

14、he concrete curing period of time or after concrete pouring. The evaporation of the water in the slurry will produce shrinkage, and the shrinkage is irreversible. Drying shrinkage cracks are mainly caused due to the diff

15、erent degree of evaporation of the moisture inside and outside the concrete result of deformation of the type: concrete affected by the influence of external conditions, excessive surface moisture loss, large deformation

16、, </p><p>　　The main preventive measures:</p><p>　　Selection of a smaller amount of shrinkage cement, commonly used in low heat cement and fly ash cement, reduce the amount of cement.</p>

17、<p>　　Concrete shrinkage by water-cement ratio, the greater the water-cement ratio, the greater the shrinkage in the concrete mix design should try to control the selection of a good water-cement ratio, while mixin

18、g the water-reducing agent .</p><p>　　Strict control than with concrete mixing and construction, concrete water consumption must not be greater than the amount of water given by the mixture ratio design.<

19、/p><p>　　To strengthen the early curing of concrete and appropriate to extend the concrete curing time. Appropriate to extend the winter construction concrete insulation cover, and brushing curing agent curing.

20、</p><p>　　(5) Set the appropriate contraction joints in concrete structures</p><p>　　2.2 Plastic shrinkage cracks and prevention</p><p>　　The plastic shrinkage refers to the before

21、 condensation, the concrete surface due to rapid dehydration resulting contraction. Plastic shrinkage cracking is generally hot and dry or windy weather, the cracks mostly wide in the middle, both ends of the thin and va

22、ry in length, non-coherent state. Short cracks as long as 20 to 30cm the longer cracks of up to 2 to 3 m, width of 1 to 5 mm. Main causes: the concrete before the final setting almost no strength or intensity is very sma

23、ll or just the fin</p><p>　　The main preventive measures:</p><p>　　(1) Selection of shrinkage values ??smaller high early strength Portland cement or ordinary Portland cement.</p><p&g

24、t;　　(2) Strict control of water-cement ratio, to increase the slump and workability of the concrete, to reduce the amount of cement and water mixed with superplasticizer.</p><p>　　(3) Pouring concrete before

25、 watering the grass roots and templates evenly soaked.</p><p>　　(4) Timely covered by plastic film or wet straw, hemp sheet to maintain final setting of concrete the moist front surface or the surface of the

26、 concrete spraying curing agent for conservation.To set the sun and wind facilities .</p><p>　　(5) At high temperatures and windy weather, timely conservation.</p><p>　　2.3 subsidence cracks and

27、 prevention</p><p>　　Subsidence cracks caused by structural foundation soil is uneven, soft, or backfill or flooding due to uneven settlement; template stiffness, the template support spacing is too large or

28、 the bottom of the support as a result of loose, especially in the template support winter on the frozen ground, permafrost thaw uneven settlement, resulting in the concrete structure cracks. Such cracks are deep into or

29、 through the cracks, toward subsidence, generally along the perpendicular to the ground or in </p><p>　　The main preventive measures:</p><p>　　on the soft soil, filling foundation should be carr

30、ied out prior to the construction of the superstructure necessary compaction and reinforcement.</p><p>　　to ensure that the template has a sufficient strength and stiffness, and firmly support the foundation

31、 uniform force.</p><p>　　(3) prevent the process of concreting the foundation is immersed in water.</p><p>　　(4) template removal time can not be too early, and pay attention to the order form r

32、emoval.</p><p>　　(5) in the erection of the template on the permafrost to take certain precautions.</p><p>　　2.4 Temperature cracks and prevention</p><p>　　Temperature cracks occurr

33、ed in mass concrete surface or larger changes in temperature regions in concrete structures. Concrete pouring, in the hardening process of cement hydration reaction to produce large amounts of heat of hydration (when the

34、 amount of cement per cubic meter of concrete will release 17,500 27500kJ heat at 350 to 550 kg/m3, so that the internal temperature of the concrete SITA about 70 ° C or higher). Cause the internal temperature to ri

35、se sharply due to the larger volume of c</p><p>　　The trend of temperature cracks usually certain rules, often criss-cross a large area of ??structural cracks; the length of the beam and plate size larger st

36、ructures, cracks parallel to the short side; deep and penetrating temperature cracks are generally parallel or nearly parallel to the direction of the short side , cracks along the longest edge segments appear more dense

37、 middle. Crack width sizes, affected by temperature changes more obvious, summer, winter wide narrow. The high temperature </p><p>　　The main preventive measures:</p><p>　　(1) try to use low hea

38、t or moderate heat cement, slag cement, fly ash cement.</p><p>　　(2) reduce the amount of cement to try to control the amount of cement 450kg/m3.</p><p>　　(3) reduce the water-cement ratio, gene

39、rally water-cement ratio of concrete is controlled below 0.6.</p><p>　　(4) improve the aggregate gradation, fly ash or superplasticizer to reduce the amount of cement, lower heat of hydration.</p><

40、;p>　　(5) improve the concrete mixing process, "secondary air" traditional "cold" on the basis of new technology, reduce the temperature of concrete pouring.</p><p>　　(6)a certain amoun

41、t of concrete admixture having less water, plasticizers, retarding admixture role to improve the fluidity of the concrete mixture, water retention, reduce the heat of hydration, delaying the time of occurrence of the the

42、rmal peak.</p><p>　　(7)hot season puts up visor and other auxiliary measures to control the temperature rise of the concrete pouring, to reduce pouring concrete temperature.</p><p>　　(8)mass con

43、crete temperature stress associated with the structure size, the larger the size of the concrete structure, the greater the temperature stress, so reasonable arrangements for the construction process, hierarchical, block

44、 pouring, to facilitate cooling, reducing constraints.</p><p>　　2.5 chemical reaction caused cracks and prevention</p><p>　　Alkali-aggregate reaction cracks and steel corrosion cracks caused by

45、the most common due to the chemical reaction caused by cracks in the reinforced concrete structure. Concrete mixing will produce some of the alkaline ions, these ions produce a chemical reaction with certain reactive agg

46、regate and absorbs water in the surrounding environment and the volume increases, resulting in concrete crisp, expansion cracking. Such cracks usually appear in the concrete structure during use, in the event d</p>

47、<p>　　The main preventive measures:</p><p>　　(1) selection of the alkali reactivity of small sand and gravel aggregate.</p><p>　　(2) selection of low-alkali cement and admixtures of low-a

48、lkali or alkali.</p><p>　　(3) selection of a suitable admixture AAR with.</p><p>　　3 crack treatment</p><p>　　Cracks in concrete remedial measures mainly the following methods: surf

49、ace repair method, grouting, caulking closure method, structural reinforcement, concrete replacement method, electrochemical protection and legal bionic self-healing.</p><p>　　3.1 Surface repair method</p

50、><p>　　Surface repair method is a simple, common repair method, the action is in the cracks in the surface of the painting grout, epoxy mortar or concrete surface coating paint, anti-corrosion materials such as

51、 asphalt, concrete protection at the same time in order to prevent various The Effect of cracking, usually can paste in cracks in the surface of the glass fiber cloth and other measures.</p><p>　　3.2 groutin

52、g, caulking closure method</p><p>　　The grouting method is the use of pressure equipment cementing material is pressed into the cracks in the concrete, the cementing material hardened concrete to form a whol

53、e, and thus play the purpose of plugging consolidation. Top cementing material grout, epoxy, methacrylate, polyurethane and other chemical materials. The filleting gouges along the cracks in the tank filled, the plastic

54、or rigid sealing material, in order to achieve the purpose of closed cracks. Commonly used plastic materials </p><p>　　3.3 Structural reinforcement method</p><p>　　When the the cracks impact on

55、the performance of concrete structures, to take structural reinforcement concrete structure. Commonly used in the following ways: structural reinforcement to increase the cross-sectional area of ??the concrete structure,

56、 corner in the component outsourcing steel, prestressed Reinforcing paste the steel reinforcement, additional the fulcrum reinforcement and shotcrete reinforcement.</p><p>　　3.4 Concrete replacement method&l

57、t;/p><p>　　The concrete substitution method is an effective method for dealing with serious damage to the concrete, this method is deteriorated concrete is removed first, and then replaced into the new concrete

58、 or other materials. Top replacement materials: of Ordinary concrete or cement mortar, polymer or polymer modified concrete or mortar.</p><p>　　3.5 electrochemical Protection Act</p><p>　　Cathod

59、ic protection, chloride extraction, alkaline recovery method, the use of the electrochemical action of the applied electric field in the medium, to change concrete or reinforced concrete in which the state of the environ

60、ment, passivated steel, in order to achieve the purpose of anti-corrosion.</p><p>　　3.6 biomimetic self-healing legal</p><p>　　Bionic self-healing legitimate the traditional components of the co

61、ncrete in some special components such as liquid-core fibers or capsules containing binder, formed within the concrete the intelligent bionic self-healing neural network system, when the concrete cracks secreted part of

62、the liquid core fiber cracks can heal again.</p><p>　　Conclusion:</p><p>　　Cracks is a common phenomenon in the concrete structure, its appearance will not only reduce the impermeability of the

63、building, affect the use of the building, and would lead to corrosion of steel, concrete carbonation, reduce the durability of the materials, the impact the carrying capacity of the building, so to carefully study the co

64、ncrete cracks, be treated differently, using a reasonable method for processing to take effective preventive measures to prevent the emergence and development of</p><p>　　混凝土裂縫的成因、預(yù)防及處理</p><p>　

65、　摘要：在建筑工程施工中混凝土裂縫的產(chǎn)生是一項(xiàng)質(zhì)量通病，因此對(duì)混凝土裂縫的成因分析、事先預(yù)防，以及產(chǎn)生后的修補(bǔ)處理是建筑生產(chǎn)過(guò)程中較為普遍的現(xiàn)象，應(yīng)引起足夠的重視?；炷潦且环N由砂石骨料、水泥、水及其他外加材料混合而形成的非均質(zhì)脆性材料。由于混凝土施工和本身變形、約束等一系列問(wèn)題，硬化成型的混凝土中存在著眾多的微孔隙、氣穴和微裂縫等。作者結(jié)合自己工程工作經(jīng)驗(yàn)，總結(jié)了混凝土裂縫原因以及預(yù)防處理措施?！　?lt;/p><p&

66、gt;　　關(guān)鍵詞：混凝土 裂縫 成因 預(yù)防 處理</p><p>　　在建筑工程施工中，混凝土裂縫的產(chǎn)生是一個(gè)普遍存在的問(wèn)題，而裂縫的解決也是一個(gè)較為棘手的問(wèn)題。混凝土裂縫產(chǎn)生的原因是多方面的，有變形引起的：如收縮、膨脹、沉降等原因引起的裂縫；有外部荷載引起的：混凝土養(yǎng)護(hù)不當(dāng)；外添加劑問(wèn)題等引起的裂縫。</p><p>　　混凝土裂縫的產(chǎn)生若不加以預(yù)防采取措施解決，它的進(jìn)一步發(fā)展延伸會(huì)導(dǎo)致

67、內(nèi)部鋼筋等產(chǎn)生腐蝕，降低鋼筋混凝土結(jié)構(gòu)的承載力、抗?jié)B性能、耐久使用年限，甚至?xí)绊懭嗣竦纳柏?cái)產(chǎn)安全。在工程中完全消除裂縫是不可能的，規(guī)范中也有明確規(guī)定對(duì)有些結(jié)構(gòu)在所處的不同條件下，允許存在一定寬、深度的裂縫。但在施工過(guò)程中應(yīng)盡量采取有效的預(yù)防和技術(shù)保障措施來(lái)有效的控制裂縫的產(chǎn)生，盡量少產(chǎn)生或盡量減少裂縫寬度、深度，尤其要避免出現(xiàn)在關(guān)鍵部位或有害裂縫。</p><p>　　1.混凝土裂縫的成因及種類</p

68、><p>　　混凝土是一種由砂石骨料、水泥、水及其他外加材料混合而形成的非均質(zhì)脆性材料。由于混凝土施工和本身變形、約束等一系列問(wèn)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(wú)害裂縫，對(duì)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(huì)不斷地?cái)U(kuò)展和連通，最終形成我們?nèi)庋劭梢?jiàn)的宏觀裂縫，也

69、就是混凝土工程中常說(shuō)的裂縫。</p><p>　　混凝土裂縫產(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(hù)環(huán)境不當(dāng)和化學(xué)作用引起的裂縫等等。</p><p>　　混凝土中常見(jiàn)的裂縫主要有以下這些：①干縮裂縫；②塑性收縮裂縫；③沉降裂縫；④溫度裂縫；⑤化學(xué)反應(yīng)引起的裂縫。</p><p>　　2.混凝

70、土中常見(jiàn)裂縫及預(yù)防</p><p>　　2.1干縮裂縫及預(yù)防</p><p>　　干縮裂縫多出現(xiàn)在混凝土養(yǎng)護(hù)結(jié)束后的一段時(shí)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(huì)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(dǎo)致變形不同的結(jié)果：混凝土受外部條件的影響，表面水分損失過(guò)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

71、束，產(chǎn)生較大拉應(yīng)力而產(chǎn)生裂縫。相對(duì)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(xì)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(jiàn)，較薄的梁板中多沿其短向分布。干縮裂縫通常會(huì)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(huì)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(guān)。 <

72、/p><p><b>　　主要預(yù)防措施： </b></p><p>　?、龠x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。 </p><p>　?、诨炷恋母煽s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(shè)計(jì)中應(yīng)盡量控制好水灰比的選用，同時(shí)摻加合適的減水劑。 </p><p>　?、蹏?yán)格

73、控制混凝土攪拌和施工中的配合比，混凝土的用水量絕對(duì)不能大于配合比設(shè)計(jì)所給定的用水量。 </p><p>　?、芗訌?qiáng)混凝土的早期養(yǎng)護(hù)，并適當(dāng)延長(zhǎng)混凝土的養(yǎng)護(hù)時(shí)間。冬季施工時(shí)要適當(dāng)延長(zhǎng)混凝土保溫覆蓋時(shí)間，并涂刷養(yǎng)護(hù)劑養(yǎng)護(hù)。 </p><p>　?、菰诨炷两Y(jié)構(gòu)中設(shè)置合適的收縮縫。 </p><p>　　2.2塑性收縮裂縫及預(yù)防 </p><p>

74、　　塑性收縮是指混凝土在凝結(jié)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(fēng)天氣出現(xiàn)，裂縫多呈中間寬、兩端細(xì)且長(zhǎng)短不一，互不連貫狀態(tài)。較短的裂縫一般長(zhǎng)20～30cm，較長(zhǎng)的裂縫可達(dá)2～3ｍ，寬1～5mm。其產(chǎn)生的主要原因?yàn)椋夯炷猎诮K凝前幾乎沒(méi)有強(qiáng)度或強(qiáng)度很小或者混凝土剛剛終凝而強(qiáng)度很小的時(shí)候，受高溫或較大風(fēng)力的影響，混凝土表面失水過(guò)快，造成毛細(xì)管中產(chǎn)生較大的負(fù)壓而使混凝土體積急劇收縮，而此時(shí)混凝土的強(qiáng)度又無(wú)法抵抗其本身收

75、縮，因此產(chǎn)生龜裂。影響混凝土塑性收縮開(kāi)裂的主要因素有水灰比、混凝土的凝結(jié)時(shí)間、環(huán)境溫度、風(fēng)速、相對(duì)濕度等等。 </p><p><b>　　主要預(yù)防措施：</b></p><p>　　①選用干縮值較小早期強(qiáng)度較高的硅酸鹽水泥或普通硅酸鹽水泥。</p><p>　?、趪?yán)格控制水灰比，摻加高效減水劑來(lái)增加混凝土的坍落度和和易性，減少水泥及水的用量。

76、</p><p>　?、蹪仓炷林?，將基層和模板澆水均勻濕透。</p><p>　　④及時(shí)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(rùn)，或者在混凝土表面噴灑養(yǎng)護(hù)劑等進(jìn)行養(yǎng)護(hù)。</p><p>　?、菰诟邷睾痛箫L(fēng)天氣要設(shè)置遮陽(yáng)和擋風(fēng)設(shè)施，及時(shí)養(yǎng)護(hù)。 </p><p>　　2.3沉陷裂縫及預(yù)防</p><p

77、>　　沉陷裂縫的產(chǎn)生是由于結(jié)構(gòu)地基土質(zhì)不勻、松軟，或回填土不實(shí)或浸水而造成不均勻沉降所致；或者因?yàn)槟０鍎偠炔蛔悖０逯伍g距過(guò)大或支撐底部松動(dòng)等導(dǎo)致，特別是在冬季，模板支撐在凍土上，凍土化凍后產(chǎn)生不均勻沉降，致使混凝土結(jié)構(gòu)產(chǎn)生裂縫。此類裂縫多為深進(jìn)或貫穿性裂縫，其走向與沉陷情況有關(guān)，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(cuò)位，裂縫寬度往往與沉降量成正比關(guān)系。裂縫寬度受溫度變化

78、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。 </p><p><b>　　主要預(yù)防措施：</b></p><p>　?、賹?duì)松軟土、填土地基在上部結(jié)構(gòu)施工前應(yīng)進(jìn)行必要的夯實(shí)和加固。</p><p>　　②保證模板有足夠的強(qiáng)度和剛度，且支撐牢固，并使地基受力均勻。</p><p>　?、鄯乐够炷翝补噙^(guò)程中地基被

79、水浸泡。</p><p>　?、苣０宀鸪臅r(shí)間不能太早，且要注意拆模的先后次序。</p><p>　?、菰趦鐾辽洗钤O(shè)模板時(shí)要注意采取一定的預(yù)防措施。 </p><p>　　2.4溫度裂縫及預(yù)防</p><p>　　溫度裂縫多發(fā)生在大體積混凝土表面或溫差變化較大地區(qū)的混凝土結(jié)構(gòu)中?；炷翝仓?在硬化過(guò)程中,水泥水化反應(yīng)產(chǎn)生大量的水化熱，（當(dāng)水

80、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(dá)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(dǎo)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(yīng)力（實(shí)踐證明當(dāng)混凝土本身內(nèi)外溫差達(dá)到25℃～26℃時(shí)，混凝土內(nèi)便會(huì)產(chǎn)生大致在10MPa左右的拉應(yīng)力）

81、。當(dāng)拉應(yīng)力超過(guò)混凝土的抗拉強(qiáng)度極限時(shí)，混凝土表面就會(huì)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(dāng)溫差變化較大，或者是混凝土受到寒潮的襲擊等，會(huì)導(dǎo)致混凝土表面溫度急劇下降，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(yīng)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。 </p><p>　　溫度裂縫的走向通常無(wú)一定規(guī)律，大面積結(jié)構(gòu)裂縫?？v橫交錯(cuò)；梁板類長(zhǎng)度尺寸較大的結(jié)構(gòu)，

82、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(zhǎng)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(xì)，而冷縮裂縫的粗細(xì)變化不太明顯。此種裂縫的出現(xiàn)會(huì)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。 </p><p><b>　　主要預(yù)防措施：</b></p

83、><p>　?、俦M量選用低熱或中熱水泥，如礦渣水泥、粉煤灰水泥等。</p><p>　　②減少水泥用量,將水泥用量盡量控制在450kg/m3以下。</p><p>　?、劢档退冶?，一般混凝土的水灰比控制在0.6以下。</p><p>　?、芨纳乒橇霞?jí)配，摻加粉煤灰或高效減水劑等來(lái)減少水泥用量,降低水化熱。</p><p>

84、;　?、莞纳苹炷恋臄嚢杓庸すに?，在傳統(tǒng)的"三冷技術(shù)"的基礎(chǔ)上采用"二次風(fēng)冷"新工藝，降低混凝土的澆筑溫度。</p><p>　?、拊诨炷林袚郊右欢康木哂袦p水、增塑、緩凝等作用的外加劑，改善混凝土拌合物的流動(dòng)性、保水性，降低水化熱，推遲熱峰的出現(xiàn)時(shí)間。</p><p>　?、吒邷丶竟?jié)澆筑時(shí)可以采用搭設(shè)遮陽(yáng)板等輔助措施控制混凝土的溫升，降低澆筑混凝

85、土的溫度。</p><p>　?、啻篌w積混凝土的溫度應(yīng)力與結(jié)構(gòu)尺寸相關(guān)，混凝土結(jié)構(gòu)尺寸越大，溫度應(yīng)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。 </p><p>　　2.5化學(xué)反應(yīng)引起的裂縫及預(yù)防</p><p>　　堿骨料反應(yīng)裂縫和鋼筋銹蝕引起的裂縫是鋼筋混凝土結(jié)構(gòu)中最常見(jiàn)的由于化學(xué)反應(yīng)而引起的裂縫?；炷涟韬秃髸?huì)產(chǎn)生一些堿性離子，這些離

86、子與某些活性骨料產(chǎn)生化學(xué)反應(yīng)并吸收周?chē)h(huán)境中的水而體積增大，造成混凝土酥松、膨脹開(kāi)裂。這種裂縫一般出現(xiàn)中混凝土結(jié)構(gòu)使用期間，一旦出現(xiàn)很難補(bǔ)救，因此應(yīng)在施工中采取有效措施進(jìn)行預(yù)防。由于混凝土澆筑、振搗不良或者是鋼筋保護(hù)層較薄，有害物質(zhì)進(jìn)入混凝土使鋼筋產(chǎn)生銹蝕，銹蝕的鋼筋體積膨脹，導(dǎo)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)。</p><p><b>　　主要的預(yù)防措施：</b>

87、</p><p>　?、龠x用堿活性小的砂石骨料。</p><p>　?、谶x用低堿水泥和低堿或無(wú)堿的外加劑。</p><p>　?、圻x用合適的摻和料抑制堿骨料反應(yīng)。</p><p><b>　　3.裂縫處理</b></p><p>　　混凝土裂縫的修補(bǔ)措施主要有以下一些方法：表面修補(bǔ)法，灌漿、嵌縫封

88、堵法，結(jié)構(gòu)加固法，混凝土置換法，電化學(xué)防護(hù)法以及仿生自愈合法。</p><p><b>　　3.1表面修補(bǔ)法</b></p><p>　　表面修補(bǔ)法是一種簡(jiǎn)單、常見(jiàn)的修補(bǔ)方法，處理措施是在裂縫的表面涂抹水泥漿、環(huán)氧膠泥或在混凝土表面涂刷油漆、瀝青等防腐材料，在防護(hù)的同時(shí)為了防止混凝土受各種作用的影響繼續(xù)開(kāi)裂，通常可以采用在裂縫的表面粘貼玻璃纖維布等措施。</p&

89、gt;<p>　　3.2 灌漿、嵌縫封堵法</p><p>　　灌漿法是利用壓力設(shè)備將膠結(jié)材料壓入混凝土的裂縫中，膠結(jié)材料硬化后與混凝土形成一個(gè)整體，從而起到封堵加固的目的。常用的膠結(jié)材料有水泥漿、環(huán)氧樹(shù)脂、甲基丙烯酸酯、聚氨酯等化學(xué)材料。嵌縫法是沿裂縫鑿槽，在槽中嵌填塑性或剛性止水材料，以達(dá)到封閉裂縫的目的。常用的塑性材料有聚氯乙烯膠泥、塑料油膏、丁基橡膠等等；常用的剛性止水材料為聚合物水泥砂漿。

90、</p><p><b>　　3.3結(jié)構(gòu)加固法</b></p><p>　　當(dāng)裂縫影響到混凝土結(jié)構(gòu)的性能時(shí)，采取結(jié)構(gòu)加固法對(duì)混凝土結(jié)構(gòu)進(jìn)行處理。結(jié)構(gòu)加固中常用以下幾種方法：加大混凝土結(jié)構(gòu)的截面面積，在構(gòu)件的角部外包型鋼、采用預(yù)應(yīng)力法加固、粘貼鋼板加固、增設(shè)支點(diǎn)加固以及噴射混凝土補(bǔ)強(qiáng)加固。</p><p><b>　　3.4混凝土置換法

91、</b></p><p>　　混凝土置換法是處理嚴(yán)重?fù)p壞混凝土的一種有效方法，此方法是先將損壞的混凝土剔除，然后再置換入新的混凝土或其他材料。常用的置換材料有：普通混凝土或水泥砂漿、聚合物或改性聚合物混凝土或砂漿。</p><p>　　3.5 電化學(xué)防護(hù)法</p><p>　　主要有陰極防護(hù)法、氯鹽提取法、堿性復(fù)原法，利用施加電場(chǎng)在介質(zhì)中的電化學(xué)作用，改

92、變混凝土或鋼筋混凝土所處的環(huán)境狀態(tài)，鈍化鋼筋，以達(dá)到防腐的目的。</p><p><b>　　3.6仿生自愈合法</b></p><p>　　仿生自愈合法是在混凝土的傳統(tǒng)組分中加入某些特殊組分如含黏結(jié)劑的液芯纖維或膠囊，在混凝土內(nèi)部形成智能型仿生自愈合神經(jīng)網(wǎng)絡(luò)系統(tǒng)，當(dāng)混凝土出現(xiàn)裂縫時(shí)分泌出部分液芯纖維可使裂縫重新愈合。</p><p><

93、b>　　結(jié)束語(yǔ)：</b></p><p>　　裂縫是混凝土結(jié)構(gòu)中普遍存在的一種現(xiàn)象，它的出現(xiàn)不僅會(huì)降低建筑物的抗?jié)B能力，影響建筑物的使用功能，而且會(huì)引起鋼筋的銹蝕，混凝土的碳化，降低材料的耐久性，影響建筑物的承載能力，因此要對(duì)混凝土裂縫進(jìn)行認(rèn)真研究、區(qū)別對(duì)待，采用合理的方法進(jìn)行處理，并在施工中采取各種有效的預(yù)防措施來(lái)預(yù)防裂縫的出現(xiàn)和發(fā)展，保證建筑物和構(gòu)件安全、穩(wěn)定地工作。</p>