某工程框架柱表層剝落原因的分析的深層次原因.doc

某工程框架柱表層剝落原因的分析的深層次原因1、工程概況該工程位于某開發(fā)區(qū)西區(qū)，工程為三層框架結(jié)構(gòu)，2007年10月5日澆筑三層柱的部分混凝土（商品混凝土），當天澆筑完畢，第七天拆除模板，模板是三合板且比較陳舊，拆模時發(fā)現(xiàn)少數(shù)模板拆不下來，粘在混凝土上，能拆下來的柱子，混凝土表面只要輕輕地一刮，表面就有大量的疑似粉煤灰砂掉落。同一家商品混凝土公司的混凝土在澆筑其它層次的梁板柱時并未發(fā)現(xiàn)此類問題。2、原因的分析工程出現(xiàn)表面剝落問題后工程建設、監(jiān)理、施工各責任主體均高度重視，多次開會分析查找原因，并委托我公司對混凝土的強度進行檢測和分析，我公司到現(xiàn)場進行了詳細的了解，發(fā)現(xiàn)以下的幾點：同層澆筑的構(gòu)造柱不同澆筑日期外觀質(zhì)量完全不同，這一天澆筑65根柱，其中后澆的36根柱出現(xiàn)上述問題，這天澆筑柱現(xiàn)場條件養(yǎng)護的試塊強度代表值36.8Mpa，已經(jīng)達到混凝土設計強度C30的123%。混凝土的表面（柱角）石子很難看到，現(xiàn)場有少量模板粘在上面，沒有粘模板的只要輕輕一刮表面就掉落一層，掉落的成份基本上是砂、粉煤灰、水泥，沒有石子。模板材料為比較舊的三合板，表層脫落嚴重。根據(jù)以上幾點情況，我中心首先對該結(jié)構(gòu)柱混凝土強度進行檢測，在總共36根柱子中抽取了其中的10根進行了回彈，回彈的數(shù)據(jù)如下表1表1從測試結(jié)果分析，所抽測出的問題柱強度都達到了設計要求。我們還對另外一天澆筑的混凝土也抽取了10根構(gòu)造柱進行了回彈其結(jié)果如表2表2從表2中我們也出看出問題柱和正常柱在強度上都能滿足設計強度甚至問題柱的強度高于正常柱。我們檢查了商品混凝土公司的生產(chǎn)記錄發(fā)現(xiàn)兩天的生產(chǎn)配比完全一樣，且原材料在這兩天沒有新進即材料也完全一樣。通過對工程實體質(zhì)量進行了檢測和現(xiàn)場仔細觀察及數(shù)據(jù)的匯總，分析產(chǎn)生剝離的主要原因有如下三個方面：（1）在這一天所用的商品混凝土用水量過大即其坍塌落度過大混凝土坍落度過大易使混凝土產(chǎn)生離析，加上商品混凝土下料高度較高，石子較細，如果加上在震搗時不力，石子就容易堆積在中間，漿料流向四周，造成構(gòu)造柱四周只有漿料，難得看到石子。（2）砂率過大，粉煤灰用量過大通過對表面脫落的材料分析，看到其成份大多為砂和粉煤灰，由于商品混凝土為使其有良好的流動性和降低水泥用量和節(jié)約成本，普遍使用粉煤灰，粉煤灰由于比較輕，在坍落度大和粉煤灰用量多的情況下，往往易集聚在混凝土的表面，由于水泥較重俗話說容易“沉淀”。不易散開，砂就和粉煤灰積聚在混凝土的四周。（3）模板架好后未涂脫模劑，也未灑水同時在澆筑時天熱風大從拆下的模板和構(gòu)造柱的外觀來看，看不出有任何脫模劑的痕跡，在詢問立模人員后也確認沒有涂脫模劑，澆筑前也未在模板上灑水，當混凝土澆筑時，混凝土坍落大且混凝土表面四周集聚著大量的粉煤灰和砂，模板又沒有灑水，加上天熱風大，混凝土表面的水分很快被模板吸干，使表面的水泥無法水化，而表面水泥含量本身少，又無法水化，混凝土表面無法形成強度，當模板拆掉后表面就會一層浮砂層，這種情況并不影響混凝土內(nèi)部的強度，有時反而內(nèi)部強度還較高，從上面我們的檢測也證明了這一點。對于表面粘柱模板現(xiàn)象是模板上比較潮濕，混凝土表面的水化正常，其在表面形成一定強度，但由于模板沒有涂脫模劑，脫不下來?？傊?，這現(xiàn)象的形成是由于上述幾種原因共同作用的，缺少哪一種因素就不大可能出現(xiàn)這種情況3、表層剝落的防治措施及處理方案商品混凝土在滿足可泵性、和易性的前提下應嚴格控制水灰比及外加劑的摻量，盡量減小出機坍落度，降低砂率嚴格控制粉煤灰的摻量。施工單位在立好模板后一定要在模板上涂脫模劑，一是減少其吸水，二是脫模順利。在澆筑混凝土這前一定要在板了灑水，在澆筑混凝土之后要加強養(yǎng)護，在天熱風大的天氣下要噴水養(yǎng)護，必要要用塑料薄膜包裹，防止混凝土表面失水太快。處理方案.發(fā)生這種情況雖然混凝土的強度達到設計強度，但由 / / 于表層的剝落給工程的施工帶來了負面的影響，需要適當?shù)奶幚恚韺拥奶幚硎紫纫獙⒏∩皩忧謇砀蓛?，用水噴灑整個柱子，讓混凝土表面濕潤，然后再用砂漿處理，確保柱子的表層質(zhì)量。4.結(jié)論以上是對一次工程質(zhì)量事故的分析和總結(jié)，對于混凝土表層的剝落，我們在混凝土生產(chǎn)以及施工過程中要有針對性的采取預防措施，盡可能采取有效的技術措施來避免上述問題的出現(xiàn)，確保工程質(zhì)量。1, the engineering general situation Engineering for this project is located in development zone west, three layers framework structure, on October 5, 2007, three-layer column of concrete (concrete), pouring is completed in the day, the seventh day dismantling template, the template is a three-ply board and quite obsolete, open mold, it found that a few templates do down, stick on the concrete, can tear open come down to the pillars of the concrete surface as long as gently a blow, sand surface has a large number of suspected fly ash fall. The same commodity concrete of concrete during casting of other levels of beam board column did not find such problems. 2, the analysis of the reason Engineering surface spalling problems after all responsibility main body in project construction, supervision, construction, attaches great importance to the analysis to find reasons for the meeting for many times, and entrust my company to the strength of the concrete testing and analysis, our company has carried on the detailed understanding to the site, found the following points: Namely the appearance quality of the casting date of constructional column in different casting is completely different, the day pouring 65 post, which after pouring of 36 post appear afore-mentioned problems, the day pouring column field conditions of curing test block intensity represents a value of 36.8 Mpa, has reached 123% of C30 concrete design strength. The surface of the concrete column (Angle) stones are hard to see the site template have a small amount of glue on it, no glue template as long as gently scraping surface drops a layer, drop composition is basically sand, fly ash, cement, stone. Template materials to compare the old three-ply board, surface peeling badly. According to the above situation, I center first to test the strength of concrete structure column, in a total of 36 pillars of the 10 of them carried on the rebound, rebound of the data in the following table 1 In table 1 From the test results analysis, the problem of parking out column strength has reached the design requirements. We have one day to the other casting concrete in 10 also extract the root of constructional column springback results such as table 2 Table 2. We also see that problem from table 2 column and column on the strength can meet the design strength even question column strength is higher than normal column. We checked the commodity concrete production records found exactly the same as the ratio of production for two days, and raw materials in this two days have no new material also exactly the same. Through to the engineering entity quality tested and summary, careful observation and data analysis of stripping main reason has the following three aspects: (1) the commercial concrete used in the water is too large in this day that collapse to fall through Spent big easy to make concrete slump concrete segregation, plus the commercial concrete cutting height is higher, the stone is fine, if coupled with poor when vibrating, stones are easy to pile up in the middle, slurry flow around, causing the reduction only paste all round, its rare to see a stone. (2) the sand ratio is too large, dosage of fly ash is too large Through analyzing fall off the surface of the material, see the ingredients most for sand and fly ash, because of the commercial concrete in order to make its have good liquidity and reduce the dosage of cement and cost savings, widespread use of fly ash, fly ash due to the comparatively light, and in a slump and dosage of fly ash, more tend to cluster on the surface of concrete, cement due to the heavier as the saying goes precipitate easily. Is not easy to scatter, sand and fly ash accumulation around the perimeter of the concrete. (3) template frame after besmearing tuomoji, nor sprinkler day when pouring hot air at the same time From the point of the appearance of remove the templates and the reduction of the, dont see any traces of release agent, after asking LiMo personnel also confirm there is no coating mold release, or sprinkling water on the template before pouring, and when concrete pouring, the concrete slump large and gather around the concrete surface with large amounts of fly ash and sand, template and without water, plus a day hot big, concrete surface moisture blot, soon be template cannot on the surface of the cement hydration, the surface of the cement content is less, and cant hydration, strength of concrete surface cant form, when the template is removed after the surface is a layer of floating sand layer, this situation does not affect the strength of the concrete internal, sometimes rather internal strength is higher, from the above we test also proved this point. Phenomenon of column template for surface viscosity is relatively wet template, normal on the surface of the concrete hydration, the surface to form a certain intensity, but due to the template didnt apply release agent, cant get down. In a word, the formation of this phenomenon is due to the combination of the above several reasons, the lack of what kind of factors are less likely to appear this kind of circumstance 3, the surface spalling of prevention measures and treatment scheme Commodity concrete in satisfied pumpability, under the premise of workability should strictly control the water cement ratio and dosage of admixture, decrease as far as possible out of the slump, sand rate strictly control the dosage of fly ash. After the construction units in the set a good template, must apply release agent on template, one is to reduce the water absorption, 2 it is mold release smoothly. Before pouring concrete must be sprinkling water on the plate, to strengthen maintenance after casting concrete, the day hot weather to wet curing,