Rebound Hammer Test: |
Today, the Rebound Hammer is a widely used technique for measuring the compressive stress of in-place concrete. It has existed since the late 1940s. The instrument, created in 1948 by Swiss physicist Ernst Schmidt, uses the rebound principle to gauge the strength of concrete surfaces.
The spring-controlled mass of the rebound hammer rebounds when the plunger is forced on the surface of the concrete, and the amount of this rebound depends on the concrete's hardness.
The goal of the Test
Examine the concrete's compressive strength by relating the order to repair and the compressive strength. To evaluate the concrete's homogeneity. Using a rebound hammer is done to determine the concrete's quality based on the required criteria.The results show that the rebound hammer's estimate of compressive strength was accurate in the 48 to 58 MPa range, with an inaccuracy of 15.32%. Still, it tends to underperform the sample size strengths in the lower and higher areas.
There are various types of rebound hammers.
Depending on the impact strength they generate, there are two distinct varieties of cement rebound test hammers. Both are successful on concrete mixes with a comparable range of compressive forces.
The compressive force is a non - destructive testing tool that measures the mass's rebound after it strikes the surface of the concrete.
The outputs of a rebound hammer are known as the rebound number, which is connected to the concrete's surface hardness.
What technique is applied in the rebound hammer test?
The rebound hammer is just a non-destructive testing tool that measures the mass's rebound after it strikes the surface of the concrete. The outcome of the rebound hammer is known as the rebound number, which is connected to the concrete's surface hardness.
What benefits do concrete rebound hammer tests offer?
For geotechnical and geologic purposes, rebound hammers are used to assess the durability and uniformity of rock formations. These distinctive models assess the age, strength, and weathering of rock formations or predict the speeds at which tunnel boring equipment will penetrate the ground.
The in-situ concrete is struck with a season pin at a specified energy during the Schmidt hammer test, and the rebound is then gauged.
Utilizing test equipment, the rebound is determined by the concrete's surface hardness. Therefore, the Test's rebound result can be used to calculate the concrete's compressive strength by consulting a few conversion tables. However, earlier studies indicated a primary relationship between the concrete compressive strength and the rebound number.
Schmidt hammer testing is not an accepted method for determining the strength of concrete. It is merely a test for assessing the structural stability of concrete, and it is barely a suitable replacement for the compressive strength test.
Pile Integrity Test:
The term "pile integrity" often refers to a few aspects of pile foundation and piles, such as the physical dimensions of the pile, continuity of the pile and uniformity of the pile material.
These elements' unique geometry presents some construction-related difficulties:
Issues with Pile Formation,
Issues with Concrete Placement,
Problems with Steel Cage Installation,
these problems could lead to Pile Integrity flaws, such as discontinuities or abrupt changes in cross-section.
As pile elements are typically buried below, quality assurance and control of these pieces become a complex problem.
Over the years, numerous intrusive and non-intrusive techniques have been developed to provide engineers with quick, dependable, and affordable solutions.
The choice of test methodology is influenced by several factors, including:
Size of a Pile (cross-section, depth)
Condition of the strata and the pile type
The most used NDT techniques for assessing pile integrity include:
Test for Low-Strain Pile Integrity
Sonic Logging Thermal Integrity Test in a Crosshole
Test for Minimal Strain Pile Integrity
A popular non-destructive inspection method for assessing the integrity and quality of piles is the piling integrity test (PIT), also known as "small strain impacting examination of deep foundation." The testing can also determine the foundations' and piles' undetermined lengths.
What data is provided by small strain pile integrity testing?
The Concrete Cross Section Has Changed ,
Inconsistency in the Pile ,
Material consistency in the pile .
The test has some restrictions:
Testing of low-strain piles does not determine the pile's carrying capacity.
Over pile caps, the test is not applicable.
Two-hole Sonic Logging
Concrete integrity and homogeneity are shown through ultrasonic cross-hole sonic logging. Concrete pile quality control is possible using this technology. The drawback of strain rate impact integrity testing is removed by using this technique. During pile construction, tubes are used to make vertical holes (at least two). Water is put inside the tubes. One tube has a sound waves emitter transducer at the bottom, and the bottom of the other tube has an acoustic wave receiver transducer. The rate of upward pull on both transducers is constant. An ultrasonic profile of the pile's integrity is created after signal analysis. The test is conducted following ASTM D6760.
Cross Hole testing is a technique that can be used to locate faults and gauge their severity. The test applies to heaps with a wider diameter.
It requires installing tubes when building piles. The cost of data collection and processing may be high. Most applications require access to the wall's tip.
Thermal Integrity Profiling
To assess the integrity of foundations and deep foundations, Thermo Integrity Profiling (TIP) employs the thermal gradient of cementitious concrete material. This technique can be used to build various deep foundations and piles, such as punched shafts, punched stacks, segments, and sub, worked significantly block piles, continual flight augured piles, and drilled displacement piles. The idea behind all this technology is to keep track of temperature changes and past events as cement cures. This temperature is related to the sustainability of foundations and deep foundations and the provision of a positive of concrete. TIP provides several benefits:
The cement area outside the steel cage can be evaluated using thermal integrity profiling.
Thermal Integrity Profiling provides real-time information on pile quality, which can accelerate the construction process.
Data interpretation is not that difficult.
Limitations for Pile Integrity Tester:
It cannot be used to check the integrity of brand-new piles.
To compare recorded logs and evaluate integrity, a reference graph is needed.
Although the cement pile is sound, a change in mix design could provide a significant variation
when evaluated in the reference graph.
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