Hi, when do you guys reinforce slabs with reinforcement mesh and when with rebars only (no mesh)?
I have seen that for large spans (lets say 6 x 6 m) they usually reinforce slabs with rebars, but not meshes. Why is that? Maybe because of large tension forces in rebars which means we need larger lap lenght between meshes?
In my country rebars are up to 6 m long (12 m for special orders).
thank you for help
You'll hear this in a lot of ways, but most of us think mesh is worthless. It's just too hard to keep it supported. When the laborers pour the concrete, they push it down by walking on it. And that's where it stays. So you have a layer of reinforcing without sufficient cover or at the soil concrete interface. Whenever I've seen mesh reinforced concrete being demolished it's a layer of corroded metal at the very bottom of the concrete.
With reinforcing bars, they're hopefully supported sufficiently that the workers can walk on it without smashing it down.
If you wanted to generalize, I'd say that if the steel is there for strength and not just temperature and shrinkage, it's bars. Mesh is used for slabs on grade. It's a little more economical as it's "pre-tied" and probably lighter than reinforcing bars, but lighter means less steel.
- No technical basis for not using mesh so long as the rules are followed.
- Like the other guys said, there are practical issues associated with using mesh in North American markets.
In the past, when labor here was less expensive, things requiring craftsmanship like this were more palatable. I've seen examples where the mesh was even draped so that it could be both the top and bottom reinforcement. That seems almost unfathomable nowadays.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
Agree with KootK.
Save for some moment frame / shear wall restrictions related to high seismicity, usage of "welded deformed wire reinforcement" in ACI 318 is on equal ground to that of rebar. Design equations are the same. ACI does allow you to refine development length and lap splice dimensions by taking advantage of a welded crosswire in the development region, but if you are a traditionalist (and want to avoid the hassle of mats stacking at the lap locations) then you are permitted to simply ignore the welds and calculate these lengths the same as you would for rebar.
Now, as it relates to plain (smooth) wire, especially the commodity stuff that is darned-near unmanageably flexible due to tiny wire diameters, yeah, not a big fan.
I've designed structures using the larger-diameter welded deformed wire mats before. No issues. I guess it just depends on the designer and which end of the product spectrum they're referring to.
Fibers are an ideal ingredient for use in concrete and mortars as a method for improving these materials where they may otherwise have weaknesses. Concrete fibers reduce shrinkage crack formation and crack widths, while also increasing performance in energy absorption and fire resistance. Additional benefits, such as reduction or elimination of reinforcing steel and increased durability, can also be seen.
Read more
Sika® has developed a software tool, FiberSave™, for calculating the amount of SikaFiber® reinforcing using synthetic or steel macro fibers, required for a slab on grade. The tool will determine the optimum dosage of fibers required to reinforce the slab for the specified loading, slab thickness and concrete grade. This efficient tool is suited for professionals with knowledge in this application. SikaFiber® is the ideal solution for replacing bulky steel rebar or wire mesh reinforcement in concrete slabs, saving time and money in the construction process. Compared to steel reinforcement, macro-fibers are homogeneously distributed throughout the concrete - increasing durability, reducing cracks and shortening construction time.
The first step to choosing the right fiber is to understand the type of fiber required for your application. The main standards for fiber reinforced concrete are ASTM C and EN. Standard Specification for Fiber Reinforced Concrete, outlines four (4) classifications for fiber reinforced concrete:
- Type I - Steel fiber-reinforced concrete or shotcrete (ASTM A820)
- Type II - Glass fiber-reinforced concrete or shotcrete (ASTM C)
- Type III - Synthetic fiber-reinforced concrete or shotcrete (ASTM D)
- Type IV - Natural fiber-reinforced concrete or shotcrete (ASTM D)
Learn more about all of the fiber types below:
Related links:What metal plating should I choose for my coins - Signature Coins
If you want to learn more, please visit our website Hongtai.
Fiber performance is influenced by three characteristics; tensile strength, aspect ratio (calculated as the length/diameter) and anchorage (hooked, crimp, emboss, fibrillation, etc.). One characteristic does not outweigh another; all three items have to work together for optimal performance.
Fiber reinforced concrete is a composite material and therefore, all fibers are tested in the concrete to prove their performance.
The fibers then provide ductility and support by bridging cracks and thus providing post crack strength to the concrete. Fibers begin to function in a structural supportive manner when the concrete matrix starts to crack, just like traditional reinforcement. The crack has to occur for the load to switch from the concrete to the reinforcement.
If you want to learn more, please visit our website Reinforcing Concrete Mesh(th,es,it).
All Comments ( 0 )