反弹锤试验提供了一种实用且经济高效的解决方案，用于估算置地的混凝土强度。最近的反弹锤的发展，以及改进的估计具体实力指南可以帮助结构工程师和条件评估专业人员准确分类具体实力，并在经济高效的框架中对核心的位置进行数据通知的决定。本文快速查看方法的历史和最近的发展。
How to Estimate Concrete Strength?
就地测试方法估计混凝土强度has been extremely popular among engineers and inspectors involved in the field of structure inspection, evaluation and condition assessment. Various non-destructive methods have been developed by different researchers over the past few decades to assess in-place strength of concrete.The rebound hammer, developed by Ernst Schmidt, provides an inexpensive and quick method for nondestructive testing and evaluation of the hardness of concrete. In this article, we will review the rebound hammer, how it works, and how rebound number is determined. Moreover, we will discuss how to估计混凝土强度using rebound hammer.
自1948年引入以来，该测试已被广泛使用。其普及背后的主要原因是其简单性，以及用于现场应用的便利性。自介绍以来，它已经广泛地由全球的几个研究人员研究过，并找到了进入不同标准和指导方针的方式ASTM C 805.“Standard Test Method for Rebound Number of Hardened Concrete”, andEN13791：2003.“Evaluation the Compressive Strength in Concrete Structures Using the In-situ Test Methods”, andACI 228.1R“估计混凝土强度的地理方法”。
What is Rebound Hammer (Schmidt Hammer) ?
反弹锤是一种非破坏性测试装置，由此在其与混凝土表面的冲击之后测量弹簧驱动质量的反弹。回弹锤的输出被称为回弹数，与混凝土的表面硬度相关。The internal mechanism of a typical Schmidt Hammer is illustrated in Fig. 1.T他的柱塞被推到垂直于表面的混凝土。当锤子朝向混凝土被推动时，使闩锁释放，并对混凝土产生冲击。此时，锤子会影响柱塞杆和篮板的肩部。在反弹过程中，滑动指示器从锤子质量移动，并记录回弹距离。锤子可以放置在许多配置中;向上，向下，水平垂直和任何中角。Commercial devices in the market use different means to display the rebound number after each strike. Older generation devices displays the rebound number through a mechanical slider. Nowadays, most modern hammers use electrical or even wireless means of displaying the results on data loggers, or smart devices such as a tablet.
How To Use The Rebound Hammer ?
反弹锤是一种非常简单的设备;但是，为了收集可靠和可重复的读数，应在测试之前满足某些条件。
1- Preparing Test Surface
Inspectors should pay attention to the following considerations prior to conducting a rebound hammer test:
- 测试表面的直径必须至少为150 mm。
- Ground concrete surface (until its flat) if it is heavily textured or contains loose mortar.Note:It is essential to know that the results from prepared surface are generally not comparable to those obtained from unprepared surfaces.
- If there is any free moisture or water on the concrete surface, it must be removed prior to testing.
- Do not test frozen concrete.Note:Concrete should only be tested after it has thawed, since frozen concrete tends to have high rebound numbers.
- 盖子厚度小于20毫米时，避免直接测试钢筋。建议使用钢筋定位器来避免在浅层深度上进行测试。
2 - 反弹锤方向
为了执行反弹锤试验，检查员应该通过牢固地握住仪器，并确保柱塞垂直于测试表面。录制仪器的方向对水平的速度至最接近的45度增量也很重要。如果仪器向上指向，则应使用正角度，如果仪器点向下，必须记录负角度。
3- Taking Measurements
Once the device is lined up, and the angle has been recorded, the inspector then gradually pushes the instrument toward the test surface until the hammer impacts. After impact, maintain pressure on the instrument and, depress the side button of the instrument to lock the plunger in its retracted position. The rebound number is then recorded to the nearest whole number.
In order to ensure accuracy,10 readings应该从每个测试区采取。此外，影响点之间的距离应至少为25 mm，并且构件的冲击点和边缘之间的距离应至少为50毫米。同样重要的是要注意，如果冲击压碎或破坏近近表面空气，则必须忽略读数，并且应该采取另一种读数。
正如前面提到的,由于不同的效果of gravity on the rebound as the test angle is changed, the rebound number will be different for the same concrete and will require separate calibration or correction charts.
How to Calculate Rebound Number
以下示例显示了如何计算并报告重击编号。让我们假设以下内容10 readingsare obtained from one test location:
36 |34 |36 |34 |37 |35 |36 |36 |43 |35
The average of these 10 readings is calculated:
Average 1 = (36+34+36+34+37+35+36+36+43+35)/10= 36.2.36
Now, discard the readings that differ from the average of 10 readings by more than 6 units and determine the average of the remaining readings.
上限：36 + 6 = 42
下限：36-6 = 30
通过调查原始读数，我们可以从列表中丢弃43（大于上限42），并且计算和报告的剩余读数的平均值为平均篮板号：
平均改性=（36 + 34 + 36 + 34 + 37 + 35 + 36 + 36 + 35）/9= 35.435
Note:If more than 2 readings differ from the average by 6 units, discard the entire set of readings and determine rebound numbers at 10 new locations within the test area.
Note:因此，十个读数的范围不应超过12。
Applications of Rebound Hammer
The main application of a rebound hammer is to measure the hardness of concrete using the rebound principle. However, researchers have tried to use the method to assess different properties of concrete. Among them, the following applications are widespread:
Assess the in-place uniformity of concrete
在劣质或劣化的混凝土的结构中描绘区域
As an in-place method to Estimate Concrete Strength
在这些应用中，使用反弹锤来估计混凝土的强度仍然是最有争议的使用。研究人员分为通过使用反弹锤来评估混凝土优势。
使用反弹锤估算混凝土强度（土工方法）
In this section, we will review how to Estimate Concrete Strength Using Rebound Hammer. Initially, this was made through certain calibration curves provided by manufacturers (see Fig below)
However, further research has showed little apparent theoretical relationship between the strength of concrete and rebound number (Malhotra和Carino，2004年). However, it is shown that if a relationship between concrete strength and rebound number for a given concrete is established, the rebound number might be used for in-place evaluation of strength.
如何建立混凝土力量与反弹号码之间的关系？
已经提出了不同的方法来建立回弹数和抗压强度之间的关系。下面描述了两个最广泛使用的方法来建立混凝土强度与回弹数之间的关系。
ACI 228.1R
In order to establish a relationship between rebound number and concrete strength, Inspectors should take a minimumof 2 replicate cores, from6 or more locations(12 concrete cores in total) with different rebound numbers. According to theASTM C805.应选择标准，测试位置，使得获得结构中的各种反弹数。按照测试方法C42 / C42M收集，准备和测试核心。强度关系将适用于相同的取向，如使用的反弹号码，如果在测试期间仪器的方向影响，则强度关系适用于用于获得相关日期的相同方向。
en 13791.
Theen 13791.requires only9 cores(taken from 9 different locations) in order to establish the relationship between strength and rebound number.Papworth等人。（2015）have reviewed how to use the rebound number ro estimate the compressive strength of concrete.
Note:According to theASTM C 805.,Locations where strengths are to be estimated using the developed correlation shall have similar surface texture and shall have been exposed to similar conditions as the locations.
Click here if you would like to learn aboutother non-destructive methods for on-site evaluation of concrete.
What Affects Rebound Hammer Readings
Although the rebound hammer provides a quick, inexpensive means of checking the uniformity of concrete, the results can be affected by the following parameters:
测试表面的光滑度
标本的尺寸，形状和刚性
Age of test specimens
Surface and internal moisture conditions of the concrete
Type of coarse aggregate
Type of cement
模具类型
Carbonation of the concrete surface
Concluding Remarks
The rebound hammer developed by Schmidt provides an inexpensive and quick method for nondestructive testing of concrete.
使用反弹锤时，应识别并考虑测试方法的局限性。
It is extremely important to note that the hammer must not be regarded as a substitute for standard compression tests but rather as a method for determining the uniformity of concrete in the structures, comparing one concrete against another, and reducing the number of core samples.
参考：
ASTM C805./ C805M-18, Standard Test Method for Rebound Number of Hardened Concrete, ASTM International, West Conshohocken, PA, 2018,www.astm.org.(DOI：10.1520/C0805_C0805M-18)
ACI 228.1R-03 In-Place Methods to Estimate Concrete Strength, American Concrete Institute Committee 228.1R
BS EN 13791:2007 Assessment of in-situ compressive strength in structures and pre-cast concrete components
M. Malhotra，V＆Carino，尼古拉斯。（2004）。CRC手册上混凝土无损检测。CRC按INC ..
Papworth, Frank & Corbett, David & Barnes, Reuben & Wyche, Joseph & Dyson, Jonathon. (2015). In-situ Concrete Strength Assessment based on Ultrasonic (UPV), Rebound, Cores and the SONREB Method. 10.1201/b18972-37.
Kya aap hindi me jankari de sakte h
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“Thanks for sharing such valuable information about a schmidt hammer. I always wondered how to use them for maximum efficiency of results.”
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What a great read. Laid out very well and answers a lot of questions.
感谢您分享有关施密锤的这些有价值的信息。
pingback：5现场评价混凝土强度的方法|欢迎您的加入FPRIMEC解决方案
在释放/剥离混凝土时，有多少立方码的混凝土是一个反弹测量。
pingback：结构条件评估的无损检测|欢迎您的加入FPRIMEC解决方案
pingback：混凝土梁裂缝的无损评价|欢迎您的加入Fprimec Solutions Inc.
在这个主题上，您将通过反弹锤尼泊尔了解估计混凝土强度。谢谢！我们一直在寻找这个信息。伟大的帖子!!这个资源sifco.co.nz/nailers/cordless-nailers我最近遇到过这个特定网站也很好。
我非常有趣，满意，我想知道如何计算数字锤的强度
How will schmidt hammer reading convert to psi? I mean how can we are judge the reading to convert the psi??
你在那里做了一些非常好的积分。我在互联网上查看了更多关于这个问题的信息，发现大多数人都会在这个网站上与您的观点一起使用。
你的帖子很棒。我可以告诉你努力发布，因为一切都经过精心地写下，所以我们对发生的事情或者在使用反弹锤估算混凝土力量时，我们没有任何疑问！
Very informative and important post, Reall your ideas about the estimate of concrete. also, your writing skill is great. thanks for sharing your thought with us.
great and valuable content, your topic is very great for everyone who’s using the hammer tool. Thanks