某工程框架柱表层剥落原因的分析的深层次原因.doc

某工程框架柱表层剥落原因的分析的深层次原因1、工程概况该工程位于某开发区西区，工程为三层框架结构，2007年10月5日浇筑三层柱的部分混凝土（商品混凝土），当天浇筑完毕，第七天拆除模板，模板是三合板且比较陈旧，拆模时发现少数模板拆不下来，粘在混凝土上，能拆下来的柱子，混凝土表面只要轻轻地一刮，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浇筑其它层次的梁板柱时并未发现此类问题。2、原因的分析工程出现表面剥落问题后工程建设、监理、施工各责任主体均高度重视，多次开会分析查找原因，并委托我公司对混凝土的强度进行检测和分析，我公司到现场进行了详细的了解，发现以下的几点：同层浇筑的构造柱不同浇筑日期外观质量完全不同，这一天浇筑65根柱，其中后浇的36根柱出现上述问题，这天浇筑柱现场条件养护的试块强度代表值36.8Mpa，已经达到混凝土设计强度C30的123%。混凝土的表面（柱角）石子很难看到，现场有少量模板粘在上面，没有粘模板的只要轻轻一刮表面就掉落一层，掉落的成份基本上是砂、粉煤灰、水泥，没有石子。模板材料为比较旧的三合板，表层脱落严重。根据以上几点情况，我中心首先对该结构柱混凝土强度进行检测，在总共36根柱子中抽取了其中的10根进行了回弹，回弹的数据如下表1表1从测试结果分析，所抽测出的问题柱强度都达到了设计要求。我们还对另外一天浇筑的混凝土也抽取了10根构造柱进行了回弹其结果如表2表2从表2中我们也出看出问题柱和正常柱在强度上都能满足设计强度甚至问题柱的强度高于正常柱。我们检查了商品混凝土公司的生产记录发现两天的生产配比完全一样，且原材料在这两天没有新进即材料也完全一样。通过对工程实体质量进行了检测和现场仔细观察及数据的汇总，分析产生剥离的主要原因有如下三个方面：（1）在这一天所用的商品混凝土用水量过大即其坍塌落度过大混凝土坍落度过大易使混凝土产生离析，加上商品混凝土下料高度较高，石子较细，如果加上在震捣时不力，石子就容易堆积在中间，浆料流向四周，造成构造柱四周只有浆料，难得看到石子。（2）砂率过大，粉煤灰用量过大通过对表面脱落的材料分析，看到其成份大多为砂和粉煤灰，由于商品混凝土为使其有良好的流动性和降低水泥用量和节约成本，普遍使用粉煤灰，粉煤灰由于比较轻，在坍落度大和粉煤灰用量多的情况下，往往易集聚在混凝土的表面，由于水泥较重俗话说容易“沉淀”。不易散开，砂就和粉煤灰积聚在混凝土的四周。（3）模板架好后未涂脱模剂，也未洒水同时在浇筑时天热风大从拆下的模板和构造柱的外观来看，看不出有任何脱模剂的痕迹，在询问立模人员后也确认没有涂脱模剂，浇筑前也未在模板上洒水，当混凝土浇筑时，混凝土坍落大且混凝土表面四周集聚着大量的粉煤灰和砂，模板又没有洒水，加上天热风大，混凝土表面的水分很快被模板吸干，使表面的水泥无法水化，而表面水泥含量本身少，又无法水化，混凝土表面无法形成强度，当模板拆掉后表面就会一层浮砂层，这种情况并不影响混凝土内部的强度，有时反而内部强度还较高，从上面我们的检测也证明了这一点。对于表面粘柱模板现象是模板上比较潮湿，混凝土表面的水化正常，其在表面形成一定强度，但由于模板没有涂脱模剂，脱不下来。总之，这现象的形成是由于上述几种原因共同作用的，缺少哪一种因素就不大可能出现这种情况3、表层剥落的防治措施及处理方案商品混凝土在满足可泵性、和易性的前提下应严格控制水灰比及外加剂的掺量，尽量减小出机坍落度，降低砂率严格控制粉煤灰的掺量。施工单位在立好模板后一定要在模板上涂脱模剂，一是减少其吸水，二是脱模顺利。在浇筑混凝土这前一定要在板了洒水，在浇筑混凝土之后要加强养护，在天热风大的天气下要喷水养护，必要要用塑料薄膜包裹，防止混凝土表面失水太快。处理方案.发生这种情况虽然混凝土的强度达到设计强度，但由 / / 于表层的剥落给工程的施工带来了负面的影响，需要适当的处理，表层的处理首先要将浮砂层清理干净，用水喷洒整个柱子，让混凝土表面湿润，然后再用砂浆处理，确保柱子的表层质量。4.结论以上是对一次工程质量事故的分析和总结，对于混凝土表层的剥落，我们在混凝土生产以及施工过程中要有针对性的采取预防措施，尽可能采取有效的技术措施来避免上述问题的出现，确保工程质量。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,