商品混凝土强度非破损检测方法的研究
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摘要
一 概述
     在不破坏混凝土内部结构和使用性能的情况下,利用声、光、热、电、磁和射线等方法,测定有关混凝土性能方面的物理量,推定混凝土强度、缺陷等测试技术,统称为混凝土非破损检测技术。钻芯法、拔出法等局部破损检测方法,由于所造成的局部损伤不危害结构安全,所以广义的理解,也将其计入非破损检测范畴。
     非破损检测方法具有不破坏构件或建(构)筑物的机构,不影响其使用性能,能真实反映混凝土的质量和强度的优点。在实际工程应用上,它主要用于与结构安全直接相关的宏观力学性能和宏观缺陷测试。
     随着工程结构的日趋复杂和混凝土的商品化发展,混凝土掺合料、外加剂及高强混凝土在实际工程中得到普遍使用,混凝土组分和施工工艺与以往相比都发生了巨大变化,其各物理量与混凝土抗压强度的相关关系也与原来产生差异。原有的非破损检测方法测强曲线仅适用于强度在50MPa以下的普通混凝土,显然它所依据的物理量和混凝土抗压强度之间的相关关系已不适用于商品混凝土(尤其是50MPa以上的高强混凝土)。本文的研究目的是:1建立常用的4种非破损检测方法对强度在20MPa~80MPa范围内的商品混凝土进行非破损检测的地方测强曲线;2通过对4种非破损检测方法误差和精度的分析,对非破损检测方法进行比较、评价和建议。
     二 试验综述
     本试验采用6组分商品混凝土,实测强度范围为:24.8MPa~88.2MPa。
     试验构件长1500mm,宽600mm,高1200mm,共12个;制作时采用人工支模,振动棒振捣,自然养护。试块采用100mm×100mm×100mm,共168组;与试验构件同盘混凝土,在振动台上振动成型,共分为标准养护试块和自然养护试块两种。
     考虑试验操作的可行性和合理性及逻辑性,将试验操作顺序安排如下:
     1在构件上:回弹法试验→超声法试验→后装拔出试验→钻芯法试验;
     2在试块上:回弹法试验→超声法试验→抗压试验。
     三 钻芯法
     钻芯法是利用专用钻机,直接从结构或构件上钻取芯样,根据芯样的抗压强度推定
    
     郑州大学硕士学位论文
     结构或构件混凝士强度的一种局部微破损现场检测方法。它是一种直观且精度较高的检
     测手段,已为较多的国家所采用。目前,随着结构配筋率的增大,钢筋间距越来越小。
     根据现行钻芯法检测规程CECS 03:88,在芯样中很难避免不取到钢筋,而钢筋对芯样
     抗压强度的影响是一个尚未解决的复杂问题,极大地影响了钻芯法检测精度和可信度。
     因此,研究制定小直径芯样检测结构混凝土已经成为很迫切的课题。
     本次试验,以直径 100mm,高度与直径的比(简称高径比,记作 H/D)为 1的圆柱
     体作为标准试件,其强度可认为是构件混凝土的实际强度;直径73 mm,高径比在 1刀~
     2刀的小芯样作为非标准试件,其强度认为是试件的检测强度。每龄期每构件钻取不同高
     径比大、小芯样各1组,每组3个,整个钻芯试验以《钻芯法检测混凝土强度技术规程》
     (CECS 03:88)为依据。
     通过试验数据处理,回归分析、误差分析及试验结果的合理性分析,建立小直径芯
     样强度与构件实际强度的换算关系,并得出对于检测强度范围在20MPa~80MPa内的商品
     混凝土构件,钻取直径刀mm小芯样检测方法及其强度推定方法。
     四 后装拔出法
    ——
     后装拔出法是在混凝土硬化后埋入锚固件,测定混凝土抗拔力的检测方法,又叫
     CApO试验[q。它具有适应性强,测定精度较高、操作简单、费用较低的优点。目前,后
     装拔出法检测混凝土强度主要存在以下2个问题:一是混凝土强度范围发生变化;二是
     商品混凝土与普通混凝士的差异使混凝土抗拔力与抗压强度所遵循的规律发生变化。
     本试验采用YJ--erl型三点支承式拔出仪,依照不同龄期,在试件上进行后装拔出试
     验测出混凝土抗拔力,并在拔出测点位置钻取芯样,来获得试件混凝土的真实强度。整
     个试验严格按照国家《后装拔出法检测混凝土强度技术规程》(CECS 69:94)附录 A建
     立测强曲线的基本要求进行。
     综合考虑曲线回归分析参数、相对标准差和建立后装拔出法测强曲线的要求及商品
     混凝土的特点,建立了检测以碎石为主要骨料、强度范围在20MPa~80MPa以内的商品混
     凝土构件,且仅适用于河南省及郑州地区的后装拔出法测强曲线。
     五 回弹法和超声一回弹综合法
     回弹法是通过测定混凝土表面硬度来推算抗压强度的一种结构混凝土现场检测技
     术。超声一回弹综合法是利用超声仪和回弹仪,测试混凝土的超声声速值和回弹值两个
     参数推定混凝土强度。二者检测效率高、费用低廉,是混凝士无损检测的基本方法之一。
     混凝土组分的变化必将引起各物理量与混凝土抗压强度的相关关系。所以,现推行使用
1 .Intruduction
    The non-disrepair is the technic that using the sound, light, heat, electricity, magnetism and radial, mensurating some data about concrete performance and presume the concrete compressive strength, the lacuna of concrete and so on, without destroying the concrete structure and influencing its workability. The partial disrepair methods, as drilling method, pulling-out method and so on, also belong to the non-disrepair inspection methods in broad sense because that using this type methods to inspect buildings can't bring the safety problem.
    The technic play an important role in the aspects of ensuring the quality of the new buildings and evaluating the security of the old buildings and are used widely in the world.
    With the developments of the structure types and the commercial concrete, the components of concrete and the construction technics have been taking great changes. Comparing with the existing correlation, the relationship between the compressive strength of concrete and the data about concrete performance is also changed. The existing inspecting curves of the non-disrepair only apply to the common concrete of which the grade is below C50 and obviously can't be applicable for commercial concrete, especially for high strength concrete. The purpose of this paper is: 1 building the local inspecting curve of the 4 non-disrepair methods which are available to the commercial concrete with the grade from C20-C80; 2 comparing and evaluating the 4 non-disrepair methods and giving some advise.
    2.Experiment in brief
    On the behalf of the commercial concrete from Zhengzhou city, the experiment has been done. The actual strength of concrete is from 24.8MPa to 88.2MPa.
    In the test, the 12 pure block were used which are 1500mm long, 600mm wide and 1200mm high and cured in nature; the 365 cube samples are 100mm high and cured in nature and standard station. Considering the feasibility and rationality of the experiments, the order of the test is in following:
    1 On block: rebound test →ultrasonic test → pulling-out test → drilling test
    2On cube: rebound test →ultrasonic test → compressive stress test
    
    
    
    3.Drilling Method
    The drilling method is the partial disrepair inspecting method that using the special equipment, directly drilling cylinders from the structure and basing on the cylinder compressive strength to deduce the structure strength. The method provides us direct and credible inspecting results and has been used in many countries. In the modern concrete structure, the space between the steels is more and more small. According to inspection specification (CECS03:88), the steel maybe exit in cylinder samples when using the drilling method to inspect structure and the effect of the steel to cylinder compressive strength is very complex. So it is necessary to study on using the small cylinder to inspect concrete strength.
    In the test, the cylinder with 100mm diameter and HID (the ratio of the height divide diameter)=l is the standard sample and its compressive strength can be regard as the factual strength of the structure. The cylinder with 73mm diameter and ///D=1.0~2.0 is the non-standard sample and its compressive strength is the inspecting strength. In the experiment the cylinder of different diameter was be drilled in pairs.
    By data processing and error analysis, the formula used the compressive strength of the cylinder with 73mm diameter to calculate the structure concrete strength is gotten and can be applied to the high strength concrete.
    4.Pulling-out Method
    The pulling-out method is also the partial disrepair inspecting method that embedding anchor in sclerous concrete and measuring the pulling-out resistance, which is also called CAPO test. Now, it have two problem in using the method to deduce the structure strength: Ithe rang of the concrete strength has been changed; 2the correlation between the pulling-out resistance and compressive strength of concrete is also changed.
    In the test, the pulling-out apparatus with 3 points support was used. First, the pul
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