I have seen that tensile strength of concrete is always lower than compressive strength values (generally 10-12 folds). How can we enhance the tensile strength of the concrete? Is it possible to enhance up to levels similar to compressive strength values either by addition of some SCMs, pozzolanic materials, admixtures, superplasticizers etc. or do we have to change the grade of concrete i.e. M20, M30....... M60 ....so on .., SCC, etc.?
Addition of steel fibers increases the tensile capacity of plain concrete. However the concrete is not plain at all. It become fiber reinforced concrete. By addition of fiber reinforcement of about 1% you can get 100% more tensile capacity for the concretes having compressive strength values between 40-70 MPa. (Enhanced tensile strength capacities are about 8-10 MPa)
Moreover, in recent years development of engineered cementitious composites (ECC) indicated that a cement based composite with high level of toughness, ductility, and tensile strength can be benefited for construction industry.
The tensile performance (strength and deformation) of plain concrete can be greatly enhanced using steel fibers. The increment depends on the dosage and the type of the steel fiber. However, I have not observed values of tensile strength of steel fiber reinforced concrete similar to those of compressive strength of plain concrete.
This could be an interesting research topic. As Julian said, different fibers such as steel, Aramid, glass, etc. can improve tensile behavior of concrete and make it follow a semi-strain hardening behavior against tensile loads. Polymer-modified concrete has the same effect as well. However, above techniques cannot increase tensile strength of the concrete up to its compressive strength.
Current technology failed to give us a cost effective concrete with noticeable tensile behavior.
Steel fibers and silica fume are used in ultra high performance concrete together with a reduction of the water-to-binder ratio. This will raise tensile strength of concrete, but never higher than compressive strength.
HI,
the tensile strength cannot be increased by adding steel fibres etc to concrete, only its toughness can be increased. the tensile strength theory is based on the flaw model and the first cracks are observed due to a flaw present in the concrete like a weak aggregate element etc. The tensile strength as of now cannot be increased to the levels of 20Mpa...there has been research in Reaction powder concrete, which has very high compressive strength of the order of 200-300Mpa, so the tensile strength is around 30Mpa., but it is expensive and not available easily. also if dolomite aggregates can increase the strength but not to 20Mpa, may be 10Mpa.
Addition of steel fibers increases the tensile capacity of plain concrete. However the concrete is not plain at all. It become fiber reinforced concrete. By addition of fiber reinforcement of about 1% you can get 100% more tensile capacity for the concretes having compressive strength values between 40-70 MPa. (Enhanced tensile strength capacities are about 8-10 MPa)
Moreover, in recent years development of engineered cementitious composites (ECC) indicated that a cement based composite with high level of toughness, ductility, and tensile strength can be benefited for construction industry.
Hi to you all,
I disagree with Aravind Tankasala: steel fibers do improve tensile strength of concrete, not only toughness, even though this increase is not so spectacular as regarding toughness. Review of literature dealing with this topic will show you that.
All mix proportionings known as ECC are interesting possibilities as well, they can be colloquially described as high-performance concretes to the limit: high fiber contents, high pozzolanic amounts, very low water-to-binder ratios, etc.
Regards.
As discussed as above, some techniques, such as fiber reinforced concrete, may help to enhance the tensile strength of concrete. These techniques also include polymer modified concrete. SCMs cannot enhance the tensile strength significantly, and sometimes make even lower tensile/compressive ratio. Normally, the tensile strength of concrete can never be enhanced to the level of its compressive strength, except for polymer concrete which uses epoxy as binder and sand/gravel as aggregate.
So far, it is very difficult to increase the tensile strength of concrete to level of it's compressive strength, mainly due to the brittle nature of concrete. However, the tensile strength can be improve significantly with the use of steel fibers and etc.
A high increase in the tensile strength of concrete can be observed by the use of steel slag coarse aggregate in concrete (ACI materials Journal, vol 109, no 4, pp 471-478, 2013). Although in special cases I obtained values one-third, it is still far away from compressive. If you managed to do that, please let me know.
The use nanomaterials in cementitious matrix can give increase of the tensile strength until 25%.
Tensile strength of concrete can be improved by adding steel and carbon fiber. However, this will be against the increase in cost.Despite the increase in tensile strength, but it remains less than compressive strength of the concrete.
you can refer to and benefit from this link
https://www.google.com/url?url=https://waset.org/publications/9997631/improving-concrete-properties-with-fibers-addition&rct=j&frm=1&q=&esrc=s&sa=U&ved=0ahUKEwjH-_v654rfAhWMECwKHW3XDYw4ChAWCBwwAw&usg=AOvVaw3WVfSB2HLlyQjJfJVjsoXi
I haven't gone through research related to ferro-cement, but I think exploiting that idea could help maximize the tensile strength. Some have already suggested use of fibers. What if we replace a certain percentage of aggregates with fibers that have higher tensile strength?
I don't think we can achieve tensile strength as high as compressive strength of concrete, but we may improve its performance in tension
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