Abstract
We wanted to test the strength of concrete in many variations and see just what is the best way to use concrete to create the most efficient form in order to create long lasting structures that wouldn’t fail no matter the weight and pressure put on them. This would ultimately help Engineers create better foundations for things like sidewalks, dams, apartment buildings, staircases, etc. We also wanted to test the reliability of concrete on its own and the level dependency that concrete has on rebar. If we include rebar in mixtures of concrete, then it could create a stronger foundation that can be used to build longer lasting and stronger architectural designs and other contraptions.
Introduction
A significant portion of constructions all around the world utilize concrete as one of their main foundations to build structures. Although concrete is widely used not only for apartment buildings, sidewalks, parking garages, dams and other architectural structures;alone concrete will not hold much due to different types of tensions like tensile stress and compressive stress. This is why before you see concrete being added to a construction site, you first see a lot of rebar set in either direction. The importance of rebar is truly significant because it is what allows concrete to sustain tons and tons of weight. Rebar is a type of steel rod that’s strength allows tensile stress that concrete takes from weight pressure from above to completely cancel out if there’s enough of the steel rods. Therefore, concrete and rebar go hand in hand to build the foundation of many structures.
Hypothesis
In this experiment the strength of concrete is tested with and without the reinforcement of rebar embedded into the concrete and also the strength of concrete when the rebar is pre stressed before the concrete dries and becomes solid. Because concrete is such a strong and common material used for construction we expected the concrete to sustain a lot of weight before cracking and ultimately breaking apart. We also expected the concrete to become three times as strong with rebar as reinforcement and even more strong when applying stress to the reinforcement before the concrete dries out.
Materials
.Rebar
.Pure concrete powder
.Water
.Mixing tool
.Wood to shape concrete to blocks
.Rebar tension tool
.Compressor machine
Methods
The methods we used to get this experiment underway were to create different sets of concrete blocks under different circumstances each. The first concrete block was simply just the concrete block. Next we made another concrete block but this time around we included two rebar rods vertically into the lower half of the concrete block, since that’s where the tensile stress is located and then put the new block on the compressor machine. Lastly we put the rebars in the same location but applied tension on the rods before the concrete dried up. All this means is that we “pulled” on each side of the steel rods in order to allow the compression to be more spread out throughout the block rather than just be concentrated in the center.
Results
For the first block the weak spot of the concrete came to be the tensile stress which is the stress caused at the bottom of the block or in other words the opposite side of where the pressure is being applied. This first block had a brittle failure which basically means the concrete failed to hold weight and broke without any physical warning like cracks on the concrete. However, when placing the second concrete block with the two steel rods on the bottom half where the tensile stress occurs, the failure changed to ductile failure which means that before the concrete snapped in half, there was physical damage like cracks that warned of the possible tragedy of the failure. On top of changing from brittle to ductile it sustained a lot more weight than just the plain concrete. Finally, the concrete block with the two beams that had tension on either side held a significantly higher amount of weight before snapping compared to the other blocks and this one also had ductile failure .
Discussion
The results 100% supported my initial hypothesis because although concrete is very strong on its own, having the help of the steel rods to basically cancel out the weakness concrete has, tensile stress. We also saw how the failure went from brittle, which happens with no warning, to ductile, which lets the constructors know that the structure is going to collapse. Some limitations in this experiment are not having consistent mixtures of the things you need in order to make concrete but the solution to that is just to make one big bucket of concrete mix in order to only use that one bucket for all blocks used in this experiment (3 blocks).
Conclusion
In conclusion, we saw how concrete by itself isn’t much of a building material but with rebar to help out on it’s weak spot, it comes out to be one of the greatest things for construction. With the help of this experiment we can demonstrate to people who are not experts in this field the intelligence and creativity that goes into building structures they see on a daily basis and just constructions all around them that they can be living in. We hope to reach those looking into the field of engineering or just those curious about what goes on in a construction site.
Reference Page
Unknown. “Why Concrete Needs Reinforcement.” Youtube, uploaded by Practical Engineering, 25 April. 2018, https://www.youtube.com/watch?v=cZINeaDjisY
