Written by : Engr Sami Ullah Stanikzai. (www.civilglobal.com)
What is Concrete:
Concrete is an engineering materials which becomes with the properties of rock and the combination of particles closely with each other. the concrete is simply a blend of aggregate. it is normally a kind of natural sand and crush rock.Concrete is very strong and its resist with compression.
Good concrete depends on good aggregate. Coarse aggregate can be as much as 75% of the volume in a mix. The best stone for making concrete is hard, durable particles with moderate absorption. The worst aggregate used to make concrete is friable, weakly cemented sandstone with high absorption. Where concrete is exposed to freeze/thaw cycles, lightweight cherts, ochres, shales, and weakly cemented materials such as conglomerate must be avoided.
The concrete is the most important material in construction works. And concrete is a good material we can get many types shape in mold. therefore we can design any thing easily with a good shape.
We have given quality of good concrete:
Resist Wear and Tear
The concrete should be strong in compression and it will be weak in tension. And concrete used in a construction of load carrying for different structures same like dames, construction of bridges, pair and abutment of bridges etc. In these structure we must be used steel bar with concrete to extend the strength of concrete. Then it will be able to resist the loads.
The concrete should be able to against of weather action, such a wind, rain, storm and variation of temperature. So when we used the concrete in the construction of dames, sewer line or in sea water then it should be able to withstand of the action of chemical salts. Then the concrete will be safe from environmental problems.
When we use the concrete In Construction of water like culvert , retaining wall , dames or in water canal so in these construction the use of concrete is very necessary so there for the concrete must be watertight the against of water. If the concrete is not watertight with construction of water palaces. then those steel bars which we used in the concrete it can be rust (corrosion). Then structure will become fail.
The concrete must be easily workable in using of construction. For that we have to use the water in limit. Then concrete will be workable and strong. But if the water ratio is max in the concrete so it’s making segregation of course aggregate and fine aggregate. And the max water ratio result is also bleeding of concrete. When the concrete making bleeding then the concrete strength is becomes loss.
The concrete must be compacted and there should be no voids or hollow left in the concrete. And the weight of concrete must be 3000kg/cu meter. So that is the good quality of concrete.
Resist to Wear and Tear
When we used concrete in the construction of road and floor, so the concrete must be able abrasive for well. If the concrete is not able to resist with different problems so that will be not the good properties of concrete.