What is the relation between the elastic modulus of concrete in tension and in compression? In early days (up to 10 days from casting) and after 28 days? Any papers?
Most of the test results on the elastic modulus were conducted on compression, and the test results on tension are very rare due to the difficulty in conducting uniaxial tests.
Besides, there is contradiction between the some of the published test results, some conclude that the elastic modulus in tension is slightly higher than that in compression, while others conclude vice versa as for self-compacted concrete. However in most of the applications it is assumed that they are equal. The type of the investigated problem may dictate the search for a realistic and reliable test results.
Hi Bartosz,
I think you will find the following article most helpful in answering at least partly your question if not completely:
https://www.hindawi.com/journals/ace/2012/391214/
Best wisshes
Mr Reddy A.C., thank You for Your answer but it is not satisfactory. It is obvious that the stress-strain plots for concrete both in compression and tension are normally strainght lines, provided that the applied stress is not too high. My question was about the elastic modulus, defined as the slope of those straight lines in the elastic deformation region.
Mr Messaoud Saïdani,
Thank You for Your answer and paper. I have read it already and in fact this publication was the reason I asked this question in the first place. In conclusions authors wrote:
"The tensile modulus of concrete is approximately 1.0–1.3-times larger than its compressive modulus within the material’s first week of age."
And yet in publications:
Qingbin Li and Farhad Ansari: "High-Strength Concrete in Uniaxial Tension"
and
Faez Alhussainy , Hayder Alaa Hasan , Sime Rogic , M. Neaz Sheikh , Muhammad N.S. Hadi: "Direct tensile testing of Self-Compacting Concrete"
authors concluded, that the elastic modulus at 28 days from casting and more is even 2/3 lower in tension in comparison with the modulus in compression.
Is that possible?
In early ages Et higher than Ec
and after 28 days Et lower than Ec ?
Article High-strength concrete in uniaxial tension
Article Direct tensile testing of Self-Compacting Concrete
Hello Bartosz,
I think it is possible and I do believe it. This is because in the very early hours when the concrete has just been cast, it is very soft and weak in compression, and will be similar to the tension, and the fact that the tension modulus is slightly higher than that in compression is justified (even a needle can penetrate the soft concrete). However, as the concrete sets and hardens, it gains increased strength, and its modulus of elasticity in compression keeps increasing (see attached diagram), and therefore it will surpass the tension modulus.
Regards
Really, in early ages Et higher than Ec because of probability of stability loss of armatures at compression is relatively high. After concrete hardening the situation became another, the stability of armatures is improved and this is expressed as compression modulus increasing.
All the best.
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