Quantifying Early-Age Stress Development and Cracking in Low Water-to-Cement Concrete: Restrained-Ring Test with Acoustic Emission

2003 ◽  
Vol 1834 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Akhter B. Hossain ◽  
Brad Pease ◽  
Jason Weiss
Keyword(s):  
Acoustic Emission ◽  
Stress Relaxation ◽  
Length Change ◽  
Ring Test ◽  
Early Age ◽  
Free Shrinkage ◽  
Stress Development ◽  
Complex Interactions ◽  
Degree Of Restraint ◽  
Restrained Ring Test

Early-age cracking has been found to occur in some concrete bridge decks, slabs, and pavements when the volumetric changes associated with drying, hydration, and temperature reduction are prevented. While free-shrinkage tests can quantify length change, they may not always be sufficient for detecting materials that are prone to cracking, since the potential for cracking is influenced by complex interactions of strength gain, stiffness development, creep, shrinkage, the degree of restraint, and toughness. The simplicity of the ring test enables it to be used as a comparative test to screen potential mixture designs. From the use of this test, AASHTO developed a provisional standard ring test that establishes specimen geometry; however, the provisional standard does not provide an approach for quantifying stress development or indicating how close a specimen may be to failure. Described is a simple stress solution for quantifying the results of the ring test. Issues related to ring and free-shrinkage specimen geometries are discussed to improve the fundamental understanding of the information provided by the ring test. Also described is how elastic stress and actual stress can be compared to measure the stress relaxation in a material. To better illustrate the microcracking and visible-crack development process, acoustic-emission testing was performed. These experiments indicated that specimens with a higher level of restraint exhibited more microcracking as a part of the stress relaxation process.

Determination of Tensile Creep and Stress Relaxation of Concrete by Ring Test

2014 ◽  
Vol 584-586 ◽  
pp. 1172-1175
Author(s):  
Si Chen Li ◽  
Ting Yao ◽  
Yu Jiang Wang ◽  
Hua Li ◽  
Jun Cheng ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Testing Machine ◽  
Tensile Creep ◽  
Ring Test ◽  
Shrinkage Stress ◽  
Early Age ◽  
Free Shrinkage ◽  
Binder Ratio ◽  
Creep And Stress Relaxation ◽  
Accurate Stress Analysis

The understanding of stress relaxation and tensile creep behavior is extremely important in accurate stress analysis and crack prediction of early-age concrete. The free shrinkage deformations of concrete with different strength grade were examined. The early-age tensile elastic modulus of concrete was investigated through temperature-stress testing machine. The tensile creep and shrinkage stress were obtained through the modified restrained ring test. The results indicate that the development of free shrinkage coordinates well with the inner strain of steel ring. Tensile creep decreases as water-binder ratio increases. Creep counteracts tensile stress of concrete by 28%~40% , decreases the possibility of cracking of concrete at early ages.

Evaluation of Recycled Aggregate Concrete Cracking through Ring Test

2012 ◽  
Vol 174-177 ◽  
pp. 1475-1480 ◽  
Author(s):  
Valeria Corinaldesi ◽  
Giacomo Moriconi
Keyword(s):  
Numerical Models ◽  
Creep Behaviour ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Tensile Creep ◽  
Ring Test ◽  
Early Age ◽  
Concrete Aggregate ◽  
Free Shrinkage

Cracks can reduce the service life of a concrete structure by allowing aggressive agents to penetrate through it in easy ways. Free shrinkage evaluation alone is not enough to determine if cracking can be expected in a structure since concrete creep behaviour, stiffness and toughness also influence the potential for cracking. Consequently, it is rather interesting to perform restrained shrinkage tests, such as the ring test according to ASTM C 1581–04. The testing procedure involves concrete ring specimens restrained by an inner steel ring on which strain gauges are placed to determine the age of cracking, since abrupt changes in the steel strain occur when concrete is cracked. Both the ring test and free shrinkage test should be carried out in the same exposure conditions, 21°C and 50% relative humidity. Moreover, compressive and tensile strengths of concrete were evaluated on cubic specimens at the time of its cracking and up to 28 days of curing. By means of analytical and numerical models of the ring specimen, some useful information on the stress induced in the material and on the tensile creep behaviour of concrete can be extrapolated thus allowing to better interpret the experimental results. This experimental procedure enables to study the influence of concrete mixture composition on the potential for early-age cracking of concrete. In particular, in this work the influence on early-age cracking of recycled-concrete aggregate partially replacing virgin sand was tested.

Evaluation of shrinkage and cracking in concrete of ring test by acoustic emission method

2015 ◽  
Vol 29 (06n07) ◽  
pp. 1540033
Author(s):  
Takeshi Watanabe ◽  
Chikanori Hashimoto
Keyword(s):  
Acoustic Emission ◽  
Portland Cement ◽  
Drying Shrinkage ◽  
Length Change ◽  
Ring Test ◽  
Emission Method ◽  
Expansive Additive ◽  
Free Body ◽  
Lime Stone ◽  
Methods Of Measurement

Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.

Hygro-mechanical modeling of restrained ring test: COST TU1404 benchmark

2019 ◽  
Vol 229 ◽  
pp. 116543 ◽  
Author(s):  
Vít Šmilauer ◽  
Petr Havlásek ◽  
Tobias Gasch ◽  
Arnaud Delaplace ◽  
David E.-M. Bouhjiti ◽  
...  
Keyword(s):  
Ring Test ◽  
Mechanical Modeling ◽  
Test Cost ◽  
Restrained Ring Test ◽  
Restrained Ring

Project rAn:  Games to promote awareness of natural disasters in young students

2021 ◽  
Author(s):  
Jose Saraiva ◽  
Priscila Doran ◽  
Rosa Doran
Keyword(s):  
Natural Disasters ◽  
Natural Disaster ◽  
Serious Game ◽  
Early Age ◽  
Human Settlements ◽  
Complex Interactions ◽  
The Earth ◽  
The Subject ◽  
Young Students

<p>The Earth is an amazing planet. However, it is also an unpredictable and wild one – part of its many charms. Atmosphere, hydrosphere, geosphere are alive, and can unleash awesome forces on the whole planet, including the biosphere, of which we humans are part. It’s important to make young students aware of the fact that we all live in a planet that was not made specifically for humans, and that it is absolutely imperative that our species learns to respect it and its rhythms and cycles.</p><p>Human settlements are often located in pleasant areas, with little or no concern about their vulnerability to natural disasters. Authorities, local, regional and national, should make preparations to prevent and mitigate their occurrence, of course. But at least as important is the need to create awareness in the citizens, so they can face any disaster and react in a calm and orderly way. That task must begin at an early age. Other than learning to deal with natural disasters and avoiding panic, schoolkids can exert a powerful influence in the adult members of their families and alert them to the measures they should adopt to prepare for any future occurrence.</p><p>In project rAn, EU-funded, we aim to develop a serious game, adjusted to the age of the targets, that will teach them about four types of natural disaster (earthquakes, floods, fires and storms) and make them aware of how to prepare and react in case of one of them striking their city or village. The game will be easy to play, and given the small age of the players will not feature complex interactions. It will include contributions from teachers and groups of students from all Europe, that will be challenged to create small games on the subject, using the Scratch language.    </p>

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