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关于T梁砼强度检测方法的分析报告 [复制链接]

WANGJUN2006
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  • 高级工程师
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  • 2006-07-29
优秀会员勋章忠诚勋章论坛元老
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发表于 2008-07-10 23:53 |只看楼主

关于T梁砼强度检测方法的分析报告 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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一、几种常用方法 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
1、 留样试块抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 优点：便于事中取样，验证生产配合比强度。在工序十分稳定情况下，随机取样，通常用以完善施工质量资料。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 缺点：工序覆盖面小，取样有选择性，人为加工制模和改变养生温度，不能反映现场振捣成型及养生等后续工序质量。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
2、回弹测试 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 优点：能反映实体强度和工序偏差，通过现场跟踪控制、调整工艺，利于发现问题，操作简便，构件实体覆盖面积大，无破坏性。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 缺点：表面硬度影响因素复杂。由于与内在整体强度相对误差在正负15%以内，所以现行规程的评定结果只能充分考虑标准偏差，取下界置信度进行强度评定，通常比其他检测方法的非统计数据结果偏低。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
3、钻芯抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 优点：能反映实体强度。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 缺点：抽样概率小，不便于统计分析，有破坏性。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
二、几种测试强度的相关分析 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
1、留样强度与回弹强度 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
从工地抽取不同强度的留样试块113块，在同一试件上做表面回弹强度（两个面测区平均值）与抗压强度对比试验 ，作相关分析图，如下图（1）： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
由图（1）可说明几个问题： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 由考虑偏差，取下置信度（-1.645*S），作回归曲线得回归方程式如下： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
R 2 =0.0499R O 1.8737                     式（1） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
    式中：R 2 为留样强度、R O 为回弹强度。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
N= 113   R=0.822 ≥ 相关检验值0.244 （取得保证率99%） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 其中值回归线与回弹检测规程所提供的线型关系基本一致。也就是说在不考虑偏差的情况下，回弹强度达到45MPa以上时，其抗压强度将会比回弹强度高出约5MPa。且砼标号越高，差距就越大。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
③ 回弹存在一定偏差，标准偏差为2.66，如果取双边置信度95%，即正负1.645*S时，上下波动值接近8MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
这说明，a、基本趋势与抗压相接近；b、由于砼配合比、表面砂浆分布等因素影响；c、由于回弹是在一个小点上进行的，存在骨料与空隙间砂浆的硬度影响差异，而抗压是整体进行的，必然产生偏差。d、事实上，在实际工程检验中，采用了单片梁评定方法，一般留样都未能采用数理统计，在强度判断时必然与回弹评定值存在差异。也可以说，就单块试件而言，其抗压强度勿用置疑。但同样砼取多组试块时，其强度偏差也同样会显现出来。从数理上讲，回弹评定值是直接在构件实体上取得的，减少了二次取样误差，其可靠度反而会显得更高一些。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
2、 钻芯强度与回弹强度 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
通过66次T梁回弹强度（平均值）与对应的钻芯抗压强度比较，作相关分析图，如下图（2）： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
由图（2）可知： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 由回归曲线得回归方程式如下： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
R 1 =25.138e 0.0163R O                  式（2） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
式中：R 1 为钻芯抗压强度、R O 为回弹强度平均值。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
N= 66  R=0.823   ≥ 相关检验值 0.320（取得保证率99%） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 由中值线回归，钻芯强度比回弹强度（平均值）一般高出7—10MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
③ 如果取95%下置信度，即考虑-1.645*S时，钻芯强度比回弹强度平均值还高出约3MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
④ 表面强度与内在强度存在如此大的差异的主要原因在于：砼在硬化过程中，水泥会产生很大的水化热，此时需要足够的水份和适宜的温度。但实际施工过程中，高温季节T梁表面易产生暴干暴湿，内外部湿度差别大；低温季节T梁表面的水化热相对降低，内外温度差别大；表面浮浆的厚薄、光洁度、骨料粗细都会给表面强度带来一定影响。然而，砼表面也是结构的一部分，其强度要求也不能太低。同时，钻芯取点极少（1—4个），在统计量上也与回弹存在很大的差异。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
3、回弹强度（评定值）与养生龄期 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
（1）搜集施工期在10—12月份、平均气温10 ℃ 、经过工艺改进、不同龄期的回弹强度评定值数据，作相关分析，如下图（3）： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
由图（3）分析： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 考虑偏差，取下置信（-1.645*S）回归曲线，即用最差施工水平估计，得回归方程式如下： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
  R O =7.4929Ln(d)+24.434                式（3） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
式中：R O 为回弹强度、d为龄期天。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
N=332，   R= 0.754 ≥ 相关检验值 0.181（取得保证率99%） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 28天龄期处中值线的回弹评定强度约为50MPa，如果考虑正负1.645*S，其强度偏差约为正负10MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
（2）参照国家建委检验标准，砼强度标准龄期以（28天）600 ℃ 天为准。说明砼强度与累计温度*天有关。如将实际温度天作标准温度天（20 ℃ ）换算，得回弹强度（评定值）与标准温度天相关图，图（4）如下： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
将图（4）与图（3）进行比较，标准温度20 ℃ 比实际温度10 ℃ 的28天强度明显提高了约5MPa。这就证明：同样温度时，龄期越长强度越高；同样龄期时，温度越高强度越高。这就为对龄期——温度进行变量分解提供了条件。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
4、不同试验方法（回弹、留样、钻芯）及龄期、温度与强度的综合相关分析： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
（1）、由式（2）、式（3）进行合并，得如下综合计算式（4）： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
R O =7.4929Ln(d)+(-0.0141* ℃ 2 +1.0158* ℃ +4.6829)  式（4） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
式中：R O 为回弹强度、d为龄期天、 ℃ 为温度。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
由式（4）计算绘制图（5），如下： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
砼龄期、温度与回弹评定强度相关图      图（5） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
（2）、由式（1）、式（2）、式（4）进行综合计算得下表（1） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

不同龄期、温度与回弹评定、钻芯强度关系表 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
结构名称：C50 T梁预制 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

龄期（d） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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检测强度（Mpa) šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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日平均温度 （℃ ） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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31.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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33.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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35.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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37.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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37.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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钻芯平均 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

37.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

39.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

41.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

43.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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45.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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46.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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46.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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试件抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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40.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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43.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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44.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

10 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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回弹评定 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

26.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

30.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

34.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

36.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

38.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

39.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

40.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

钻芯平均 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

38.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

41.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

43.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

45.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

48.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

48.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

试件抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

　 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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42.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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46.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

49.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

50.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

14 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

回弹评定 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

29.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

33.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

36.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

39.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

41.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

42.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

42.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

钻芯平均 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

40.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

43.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

45.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

49.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

50.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

50.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

试件抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

　 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

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šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

42.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

48.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

52.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

55.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

56.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

20 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

回弹评定 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

31.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

35.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

39.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

41.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

43.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

44.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

45.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

钻芯平均 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

42.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

45.1 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

49.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

51.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

52.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

52.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

试件抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

　 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

40.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

48.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

54.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

59.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

62.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

63.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

28 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

回弹评定 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

34.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

38.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

41.7 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

44.3 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

46.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

钻芯平均 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

44.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

47.0 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

49.6 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

51.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

53.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

54.5 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

54.9 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

试件抗压 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

　 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

46.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

54.2 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

60.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

65.8 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

69 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

70.4 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
※ 40 MPa以下无留样抗压数据，故空缺。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
三、由表（1）所列数据，可以说明如下问题： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
1、表（1）所列数据均为统一实行工艺改进后的数据，也就是说配合比、工艺参数都是较为规范的。如砂率28—32%、坍落度7—9cm、分层浇筑、附着式振动加插入振捣等。但所有计算公式都考虑下限值，也即按最差工艺水平加以考虑。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
2、各施工单位实际生产配合比的设计砼标号都大于50MPa，（一般57.7—60，个别甚至达65），但检验结构物实体还是以设计50MPa为准。因为设计富余标号的目的就是为了保证构件实体在经过各道工序波动和气候影响后，最终强度还不小于50MPa。更何况用-1.645*S评定值进行评定时，其保证率为95%，其中也还有5%不合格的小概率事件。如从上波动界线看，施工中经常出现强度极高的产品也是正常波动现象。如果工艺偏差较小时，不合格的可能性就不会出现。然而，钻芯强度没能考虑标准偏差问题，所得到的强度结果总是会比回弹评定值高出7—10 MPa。标准差越大误差越大。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
3、关于张拉龄期与张拉强度 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 规定张拉龄期不少于7天，张拉强度不小于设计强度0.8（50*0.8=40），可理解为双重控制。即使强度大于40MPa，但是，一方面张拉龄期是考虑砼收缩，防止张拉损失产生，另一方面也防止盲目将富余标号增大而掩盖砼收缩的影响。从表（1）所列数据看，由于砼早期强度较高，龄期在5天以上，温度15 ℃ 以上时，钻芯强度都能达到40以上，但不一定就可以张拉。至于在气温高于25 ℃ 时，5天龄期钻芯强度都能达到43MPa以上，是否可以张拉，也值得慎重研究决定。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 由表（1）可以看出，在10 ℃ 以上温度条件下，7天钻芯强度基本能满足40MPa的张拉强度。所以，在用同条件留样试块检验张拉强度的同时，可以考虑用回弹仪对构件进行检验。查表（1），在一定温度对应条件下，如果实测回弹评定值大于表中7天钻芯强度所对应的回弹评定强度时，即表示可以张拉。应该说，这个控制值，是实体的强度值，比少量的留样试块应更有代表性。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
4、关于吊装龄期与吊装强度 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 《公路桥涵施工技术规范》（JTJ041-2000）要求构件吊装强度不应低于设计文件的要求，设计无明确要求时，最低不低于设计强度的0.75；本工程设计文件虽然没有明确规定吊装强度，但要求存梁期为30天。前者的要求和本工程10天龄期以上实际能达到的强度相比，显得偏低。而后者的要求在实际施工中又难以做到。结合表（1）显示的结果平衡考虑，以标准温度（20 ℃ ）为基准，规定吊装强度不小于设计强度的0.9（50*0.9=45MPa）较为符合实际。由表（1）可以看出，在20 ℃ 以上温度条件下，10天钻芯强度都能满足这个要求。由于受7天张拉龄期的限制，张拉后还要压浆，而砂浆强度要求不小于30MPa，砂浆（设计强度同样为50MPa），借助表（1）数据，砂浆强度达到30MPa以上起码需3天，这就决定吊装龄期起码不得小于10天龄期。更何况，规范规定砼养生不得小于7天，也决定了吊装龄期不能少于10天。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 从表（1）看，在15 ℃ 以上温度条件下，10天龄期的钻芯强度也基本能满足设计强度0.9（45MPa）要求。但在15 ℃ 温度条件下施工时，则龄期要达到14天其钻芯强度才能满足吊装要求。换言之：温度20 ℃ 以上时，吊装龄期不少于10天；温度15 ℃ 时，吊装龄期不少于14天；温度10 ℃ 时，吊装龄期不少于20天；温度低于5 ℃ 时，应考虑加温、加湿养生。根据气象统计，在公安地区施工1月、2月、12月必须实行加温养生。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
据此类推，对应芯样强度45MPa，温度在20 ℃ 以上时，10天回弹评定强度达37MPa即可吊装。考虑累计计算误差适当提高到40MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
③ 查表（1），可以通过早期回弹检验进行强度控制，当回弹评定值大于表中所对应的钻芯强度值时，可以作为决定是否吊装的参考依据。因为不可能每片梁在吊装期都有留样试块或钻芯取样。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
④ 综上述，为简化起见，我们甚至可以认为在10 ℃ 温度时，统一规定10天以上龄期吊装，也不会出现不合格的风险。理由为： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
a、其强度不会低于设计强度的0.75。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
b、表（1）数据是按最低水平考虑的，只要加强工序管理，10天强度达到设计的0.9也不是十分困难。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
c、从图（3）温度为10 ℃ 的强度增长曲线看，即使十天强度只有40MPa，到满足600温度天（60天）时，其强度也完全能增长到50MPa以上。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
5、关于回弹检验 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
通过表（1）数据提出如下看法，供参考。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
① 砼28天回弹强度评定值一般都比钻芯强度小7—10MPa。其中，温度20 ℃ 时约小于7MPa；而温度15 ℃ 、10 ℃ 、5 ℃ 时 分别小约8MPa、9MPa、10MPa。这与温度越低其表面硬度越小的实际情况是基本相符的。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
② 只有在15 ℃ 温度以上，28天回弹强度评定值达到42 MPa以上时，其钻芯强度可达50MPa—55MPa，其试块抗压强度可达54MPa—70MPa，这与工地试验室大量的试验数据都是比较符合，也与这几种检验方法的特点较为相符的。同时也说明，不能盲目认为留样试块强度高，构件实体的强度也同样高，这里面有一个后续工序波动损失问题。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
③ 如果将表（1）龄期向更长方向顺延，可以得出如下结论。由下表列出各温度条件下，回弹评定强度达到50MPa所需要的实际龄期： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
表（2） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

温度（ ℃ ） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

15 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

20 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

25 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

30 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

35 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

龄期（d） šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

85 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

60 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

50 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

40 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

35 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»

šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
这表明： šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
a、当温度大于20 ℃ 、回弹评定强度大于约45MPa时，钻芯强度均能满足设计强度。其它温度条件，可查表（1）数据作参考标准。如果仍然以回弹评定值达到50MPa为标准，则养生龄期要增长，则按表（2）提供的龄期进行检验为宜。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
b、温度低于10 ℃ 时，回弹评定值到达50MPa的龄期将超过90天，不适于回弹检验，可考虑比28天强度低7—9MPa。因为其对应的钻芯强度和试块抗压强度均大于设计强度。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
c、因此，可以认为：在600个温度天内，当砼回弹评定强度大于45MPa时，可以不考虑再次进行钻芯验证。或者达到表（2）所列的龄期进行回弹检验（如温度20 ℃ 达60天），其回弹评定值不小于50MPa。一方面，其对应的钻芯强度都能高于50MPa；另一方面，现在各梁场在吊装前都实行了全数回弹检验，势必出现大量的钻芯试验，其工作量之大，构件损坏严重，影响正常施工进程。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
大量统计分析表明在累计温度天的龄期范围内，采用回弹检验的风险并不会比钻芯检验不考虑标准偏差而满足50MPa的风险大。从概率角度考虑，钻芯取点少，出现小概率的可能性很大，其保证率系数应大于1.645*S才能与回弹评定值具有可比性。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
④ 如果在没能满足表（2）所列温度——龄期时，笼统地要求所有构件砼回弹评定强度都能达到设计（50MPa）的要求，就不是十分合理。同时，也难以使施工配合比达到既质量可靠又相对经济的要求。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
⑤ 同时也要认识到，回弹评定强度低，与标准偏差大有关。施工时，各工序施工人员应熟悉工艺操作规程，按施工技术规范施工；要提高施工工艺和质量控制水准，尽量减小构件各部位的强度偏差；一般回弹强度偏差以控制在小于4MPa为宜。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
⑥ 为了保证准确的张拉、吊装龄期和强度，要求施工时T梁施工编号、浇筑日期、张拉日期、吊装日期都要由监理人员现场标记编号和做好监理记录。以防止以长龄期的构件冒充短龄期构件，而致使龄期增长强度达不到设计要求。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
⑦ 利用回弹检验能在早期进行工序质量控制和检测，防止不合格产品成批出现，及时进行配合比和工艺调整。只要按既定的规律办事，其检测结果是十分可靠的。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
⑧ 使用的回弹仪质量必须可靠，按规定经常校定，超过使用寿命的回弹仪，即使初始校正值在规定范围内，但在连续弹击过程中有弹力衰减现象，应该废止使用。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
四、结论 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
1、验证生产配合比和施工、监理抽样时，可随时抽样做留样试块。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
2、压浆强度用留样试块同条件养生，做抗压试验。龄期不少于3天、抗压强度不小于30MPa。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
3、T梁张拉龄期不少于7天，回弹评定值不小于30MPa，或对应的钻芯强度不小于40MPa。龄期和强度双重控制。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
4、T梁吊装龄期不少于10天，回弹评定值不小于40MPa，或对应的钻芯强度不小于45MPa。龄期和强度双重控制。当吊装龄期大于20天时，则回弹评定值不小于45MPa为宜。龄期达28天以上者应用式（4）计算其是否达到表（1）所对应的强度，60天内回弹强度能满足设计要求（也即钻芯强度大于设计）者，也可允许吊装。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
5、生产配合比设计要充分考虑施工控制检测所统计的标准偏差。当偏差过大，而又难以克服时，应相应提高其设计标号。 šBÙóÐG¢bbs.3c3t.comùz !œHÁ b»
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发表于 2008-07-11 18:24 |只看该用户

回复: 关于T梁砼强度检测方法的分析报告

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