The known compressive stress-strain curve of concrete corresponds to the negative strains despite the selected axis shift to the positive strains values.
The concrete tensile yield stress is known as a tenth (1/10) of the compressive concrete yield stress.
It is easier to measure with experiments the compressive case than the tensile one.
But in practical dynamics, several structures work from compressive to tensile stresses under cyclic loadings.
From these findings, can we conclude that all the tensile stresses are a tenth of their compressive stresses in the concrete stress-strain curve ranging from the negative values to the positive ones ?
Most people consider the theoretical compressive strength of concrete to be about seven to eight times larger than its tensile strength. This does not imply a consistent fixed relation between the compressive and tensile strength of concrete. In fact, the type of aggregate, the compressive strength range, the properties of the cement paste-aggregate transition zone, and many other parameters affect this relationship. So there is a relation between the two, but it is not a direct proportionality. For instance, the ratio of tensile to compressive strength tends to be lower for higher compressive strengths. Also, tensile strength is measured using different methods (direct tensile, splitting, flexure, etc.) and these produce diverse relations with compressive strength for the same concrete. Also, the tensile strength of concrete tends to be more sensitive to improper curing than the compressive strength. So the relation between the two is rather more complex than just assuming a constant ratio of 1/10.
The pure axial tensile stregth is abt. 1/10 of compressive strength, but the INITIAL Young's modulus E is roughly the same both for pure tension anh compression. The stress-strain curves,-apart from the very first section- are of course different, tending to a very different final stress value and to a much shorter strain value inthe case of tension.
Attila Erdélyi You have given the important behaviours of concrete material. the strength is for the maximum compressive stress as a yield stress.
I want to notice that concrete is considered as a heterogeneous paste by researchers and consequently it is roughly considered as an isotropic material with the same characteristics in all direction. This is an approximation when we consider its arbitrary located components. Another important remark is the hysterisis stress-strain curve given for steel by several widely used softwares. This is due to the returning path with the impossibility to reach the initial strain value.
Most people consider the theoretical compressive strength of concrete to be about seven to eight times larger than its tensile strength. This does not imply a consistent fixed relation between the compressive and tensile strength of concrete. In fact, the type of aggregate, the compressive strength range, the properties of the cement paste-aggregate transition zone, and many other parameters affect this relationship. So there is a relation between the two, but it is not a direct proportionality. For instance, the ratio of tensile to compressive strength tends to be lower for higher compressive strengths. Also, tensile strength is measured using different methods (direct tensile, splitting, flexure, etc.) and these produce diverse relations with compressive strength for the same concrete. Also, the tensile strength of concrete tends to be more sensitive to improper curing than the compressive strength. So the relation between the two is rather more complex than just assuming a constant ratio of 1/10.
Moncef L. Nehdi yes it is true for several aggregates and cements properties but for the same aggregates samples and their corresponding results we can assume that there is a relation for little deformations where as an example a bridge structure can deform from compressive to tensile deformations in one direction. The flexural bending can also contribute to these deformations. In these little deformations cases, an elastic deformation can be considered to get the E Young's modulus from the curve slope where E corresponds to the stress value for a unitary strain. I have given the published (1/10) coefficient. I am sure that this bridge structure deforms with little strains and it is away from severe loadings which are probabilistic cases. In practice researchers are always called to legally use published known formulas until a new method or formula is adopted and internationally published.
If one can plot the stress-strain curve one obtains a hysterisis curve which may not increase in its form because concrete is very stiffer than metals. It is also known that concrete doesn't have an initial strain value which can not be reached after the second path like steel.
I completely agree with Prof. Moncef L. Nehdi. Different factors influence the relationship between the compressive and tensile strengths of concrete. For example, coarse to the fine aggregate ratio in the two concrete mixes having the same compressive strength may have different compressive to tensile strength relationship.
1/10 is a bit of an optimistic guess. Moncif Nehdi has put it very well... Thanks to many researchers...there are now relationships that can predict tensile and flexural behavior of concretes as a function of compressive strength, water cement ratio, strength class, aggregate Volume, reinforcement indices, age.. it is better to consider these factors in the formulas that predict tensile strength.. but such relationships cannot be find in one single plate. In my experience, I would give weight to those equations which consider strength class. Moreover, actual experimental results are more reliable for tension critical structures.
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