【正文】 控制和預防裂縫的措施進行等進行闡述。究其原因，我們對混凝土溫度應力的變化注意不夠是其中之一。其次，在運轉過程中，溫度變化對結構的應力狀態(tài)具有顯著的不容忽視的影響。后期在降溫過程中，由于受到基礎或老混凝上的約束，又會在混凝土內部出現拉應力。如養(yǎng)護不周、時干時濕，表面干縮形變受到內部混凝土的約束， 也往往導致裂縫。一般設計中均要求不出現拉應力或 者只出現很小的拉應力。這個階段的兩個特征，一是水泥放出大量的水化熱，二是混凝上彈性模量的急劇變化。溫度應力主要是外界氣溫變化所引起，這些應力與前兩種的殘余應力相迭加。如箱梁頂板混凝土和護欄混凝土。混凝土的徐變使溫度應力有相當大的松馳，計算溫度應力時，必須考慮徐變的影響，具體計算這里就不再細述。當混凝土溫度高于氣溫時應適當考慮拆模時間，以免引起混凝土表面的早期裂縫。只是對一般鋼筋混凝土有影響。但加筋后結構內的裂縫一般就變得數目多、間距小、寬度與深度較小了。 為保證混凝土工程質量，防止開裂，提高混凝土的耐久性，正確使用外加劑也是減少開裂的措施之一。 （ 2）水灰比是影響混凝土收縮的重要因素，使用減水防裂劑可使混凝土用水量減少25％。 （ 6）混凝土在收縮時受到約束產生拉應力，當拉應力大于混凝土抗拉強度時裂縫就會產生。 （ 9）摻外加劑混凝土和易性好，表面易 抹 平，形成微膜，減少水分蒸發(fā)，減少干燥收縮 . 許多外加劑都有緩凝、增加和易性、改善塑性的功能，我們在工程實踐中應多進行這方面的實驗對比和研究，比單純的靠改善外部條件，可能會更加簡捷、經濟。 2）防止混凝土超冷，應該盡量設法使混凝土的施工期最低溫度不低于混凝土使用期的穩(wěn)定溫度。 適宜的溫濕度條件是相互關聯的。因此混凝土澆筑后的最初幾天是養(yǎng)護的關鍵時期，在施工中應切實重視起來。 施工方法 2． 1 模板制作與安裝 由于防水混凝土特別強調密實性，所以對模板的制作和安裝也相應提高 了要求 ，即要求密實不漏漿，堅固不變形 ，吸水性要小 ，宜優(yōu)先選用竹膠板模板或鋼模板。 4)嚴格控制鋼筋保護層厚度。 2)當使用外加劑，應將外加劑制成一定濃度的溶液后加入攪 拌機內，不得將外加劑的干粉或高濃度溶液直接加入攪拌機內， 防止攪拌不均勻而局部集中，既失去外加劑作用 ，又影響混凝 土質量。 2． 4 施工中的注意事項 1)施工作業(yè)面的合理劃分。 3)堅持開門子下料或用串桶 (溜槽 )下料。 防水混凝土結構施 工中，常常是底板與豎壁分別施工，即在豎壁上做施工縫處理。t be ignored on the stress state of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack make a discussion in constructing this text. Reason of a crack Have many kinds of reasons to produce the crack in the concrete, it is mainly the changes of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is not up to standard (if the alkali aggregate react), the template is out of shape, the foundation does not subside etc. evenly . The cement emits a large amount of heat of hydration when the concrete is hardenned, inside temperature is rising constantly, cause the stress of drawing on the surface. In the course of lowering the temperature , is it congeal foundation pay restrain to mix always later stage, will present the stress of drawing within the concrete . Reducing of temperature can surface cause heavy stress of drawing very in concrete too. When these draw the stress and go beyond resisting the ability of splitting of concrete , namely will present the crack . A lot of inside humidity of concrete change very light or change relatively slow, surface humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing,contract surface there aren39。t out of shape and stress not cause not free. Such as case roof beam roof concrete and guardrail concrete. This two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequently. It is a more plicated job to want to analyse the distribution , size of the temperature stress accurately according to known temperature. In case of great majority , need to rely on the model test or the number value to calculate. To is it make temperature stress have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep , calculate concretly that no longer states thinly here. Control and preventing the measure of the crack of 3 temperature 土木建筑 學院 0504 班學生 高尚立 畢業(yè)設計 第 9 頁 共 14頁 濟南大學畢業(yè)設計用紙 For prevent crack , lighten temperature stress can from control temperature and is it is it set about to restrain terms from two to improve. The measure of controlling temperature is as follows: (1)Is it improve aggregate grade mix , is it do rigid concrete to spend , mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical ,etc. measure in order to reduce cement consumption of concrete to add。 (5)Stipulate rational form removal time, the temperature keeps warm the surface while lowering suddenly, in case that the rapid temperature gradient takes place in the concrete surface。 (3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time。s had guarded against reinforced bar protective layer deviation piece big mass mon failings. The concrete stirring and mixing makes and transports Since the waterproof concrete requires that higher closely knit , reason why stir and mix system also need to have the fairly good homogeneity , should be ready for burning as follows 土木建筑 學院 0504 班學生 高尚立 畢業(yè)設計 第 13 頁 共 14頁 濟南大學畢業(yè)設計用紙 almost for this purpose 1) ensures that mixing time , mixing at every time are secondary jump into a expect the general ejection of pact block of wood less than 2 mins. 2) should use the apposition agent , the solution queen who should manufacture certain thickness from apposition agent adds the mixer inner, the dried powder or high concentration solution will add an agent extra not to adds the mixer inner directly ,prevent from mixing is uneven but part concentrates, both lose the apposition agent effect, and affect concrete mass. 3) responds to the assured source of life degree having a spot test on the admeasurement concrete at the regular intervals collapsing in the process being under construction , construction is middle if Yu rains or other cause, respond to the ratio determining whose water ratio, and adjusting the position being under construction in time when change happened in sandstone moisture content. 4) project uses the modity concrete , has boundary have raised a concrete stirring mass and of all kinds effect apposition agent adulterating falls when amounts , the water ash having controlled a concrete strictly collapsing. 5) concretes concrete adopt a pump to have given handicraft , effective avoiding a concrete producing the phenomenon isolating Mi Shui and leaving out thick fluid in the process of transportation. Matters needing attention in being under construction 1) co