I am conducting a study on ultra high performance concrete (UHPC) and I am doing a parametric study on a single column. Half of that column should be made of UHPC and the other half is normal strength concrete. I want to know if this is possible in real life.
Abdulrahman Elzainy, Yes, it is possible to use different concrete strengths in a single column. However, there are a few things to keep in mind when doing this:
- The two types of concrete must be compatible with each other. This means that they should have similar shrinkage and expansion properties, so that they do not crack or delaminate at the interface.
- The transition between the two types of concrete must be carefully designed and constructed. This may involve using special reinforcement or construction techniques.
- The column must be designed to take into account the different strengths of the two types of concrete. This will ensure that the column has the required load-carrying capacity and stiffness.
Overall, using different concrete strengths in a single column is possible, but it is important to carefully consider the design and construction implications.
Topic looks interesting. Normally column is subjected to compressive loads and moments also depending upon eccentricity and fixity at joints ( ends). While proposing variation of grade( quality) of concrete along the length of column, care should be taken to utilize the material properly, since your objective looks to achieve economy in material.
Instead of considering half length of concrete of different concretes in a single column as you mentioned, I am suggesting that the single column can be cast into three equal parts using different grades of concrete. Conduct research by placing
1. Normal grade concrete in middle third part and UHPC at end parts of column
2. UHPC at middle third part and normal grade concrete at end parts of column.
You can try with minimum percentage of main steel reinforcement based on normal grade concrete and stirrups with equal spacing.
To avoid mixing of both types of concrete during casting and compacting, necessary care should be taken for proper bonding and avoid damage to early cast concrete ( setting time need to be considered).
Columns joints are important as they are subjected to maximum moment and therefore we need to define a zone upto which changing strength is not advisable. Secondly, at higher stories it is a practice to reduce the size of columns to have more functional areas rather then keeping the same size of columns with reduced concrete strength.
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