CIVIL ENGINEERS?? URGENT HELP NEEDED.

Question

What are the main disadvantages of using concrete as a building material. could u outline them with some detail (too much is not necessary) it would also be helpful if you could list your sources plz :)

Answer 1

If you want me to answer your question soon, then I won't be able to give you too much detail. But here is what all civil engineers learn in their basic "Strength of Materials" and "Reinforced Concrete Design" class.

Disadvantages include:

1) Concrete is weak in tension - Dollar for dollar, concrete is one of the best materials for resisting compressive forces, but it is very weak resisting tensile forces (i.e. forces that pull apart). This is why structural concrete must be reinforced with steel, because steel is strong in tension.

2) Concrete doesn't keep well - It can be difficult sometimes to estimate just how much concrete you're going to need for a project. There is often some cost-saving advantages to pre-ordering your materials prior to construction, but doing so with concrete is always risky - particularly if you are pumping it into the ground to fill a hole. Coming up short isn't really that bad because you can always order more, but it needs to be delivered in a timely manner before the other concrete sets- especially if you're doing a single pour. The big problem is if you order too much. What do you do with it? It's not like you can take it back to your office and put it into storage like you can with other building materials.

3) It is difficult to alter precast concrete - If you need to tweek something in design or if the designs have changed, it is difficult to modify precast concrete. Why? It's already hard! It's a serious pain to cut because of all of the rebar in it. So if you're going to use precast concrete in your design, you'd better make sure your design is finalized and good before you order your precast.

4) Difficult to place CORRECTLY - Some would argue with this claim, but the key word is "correctly." Concrete is a high maintenance material that requires a lot of TLC during the curing process. Any amount of negligence on the part of the contractor can result in an inferior product.

5) Prone to sulfate attack - most concrete is prone to being attacked by sulfate, which is often present in things like sewage or industrial waste water. Sulfate also often exists naturally in the soil. There are special types of concretes that are not prone to sulfate attack, but they are usually much more expensive.  

Answer 2

just a lot of weight..

just study, it´s really like the basics!

Answer 3

Using concrete as a building material does not differ in concept with using masonry. Both do not sustain tensile stresses so you have to use arches, dooms, or folded plates designs to roof structures. Compression should be carried by walls rather than coloumns as concrete does not withstand tension generated from elastic lateral strain. However, using reinforced concrete changes the subject completely.