The durability of concrete Essay Example | Topics and Well Written Essays - 3000 words

The durability of concrete - Essay Example This research will begin with the definition of concrete, as a construction material. Concrete is a basic construction material, it is made of mainly four constituents, cement, fine aggregate(sand), coarse aggregate and water. With the addition of water to the cement and other components in dry form, this addition of water makes the concrete fluid and this flow able mixture enables us to pore in the desired shape and size which is dictated by the moulds and formwork. During this the water chemically bonds with the cement and hydration takes place. The ultimate strength of concrete is a factor of water cement ratio and this is the reason a precise mix ratio of concrete is calculated and mix design is prepared. Finally the dry components are combined to form hardened matrix. This final product, the concrete is good in compressive strength but weak in tensile strength. To finish this weakness we provide steel reinforcement which has high tensile strength. This concrete is called the rei nforced concrete. The concrete’s quality is determined by the quality and care taken while the production phase of the concrete. As we are well aware of the fact that elasticity of concrete is all most the same at low stress levels but tends to decrease as the higher stress levels are attained as matrix cracking develops. At the very same time the concrete is very weak in thermal expansion and has a low value of coefficient of thermal expansion. The content of cementitious material, along with the water content determine the final strength, durability, abrasion resistance, shrinkage values and many other properties. But the most important property that is under discussion is the Durability of concrete. Definition of Durability: Concrete durability has been defined by the American Concrete Institute as â€Å"its resistance to weathering action, chemical attack, abrasion and other degradation processes† Durability can also be defined as â€Å"the quality of materials or structures of continuing to be useful after an extended period of time and usage†. Whereas according to PCA(Portland Cement Association),† Durability is the ability to last a long time without significant deterioration†. Summarizing the above definition the durability is the ability of concrete to maintain it size, shape and all other properties against adverse environment with respect to time. Now the next issue is that what factors affect the durability of concrete and how can the material be improved to get the highest efficiency and life. There are several aspects that govern the strength of concrete and its life but the most effective way to calibrate this is to understand the process of deterioration in the first place. The most common proof of the deterioration process is the formation of the cracks and the detail study of the types of cracks will enable us to decide and deduce the reason, mechanism and solution to the problem. These cracks can be formed by during the plastic state or the hardened state. The reason of which will be discussed in details in the next sections. Processes of Deterioration There are several ways in which the deterioration of the concrete can be studied and processes explained but I believe that the most comprehensive pattern to understand this process is to first understand the cracks and types of cracks and then the reasons for their formation. Concrete has two forms during its formation and service. Firstly it is in fluid state and then the hardened state. Now we will discuss the processes under the two states. Fluid State deterioration and Crack propagation The reasons for these cracks are mainly due to the poor workmanship and handling. The main reasons among this are plastic shrinkage, settlement and lastly movement of formwork and subgrade during the construction work.