Skip to main content

civil engineering-->>Durability of Concrete


Durability of Concrete


Concrete Durability

Durability is defined as the capability of concrete to resist weathering action, chemical attack and abrasion while maintaining its desired engineering properties. It normally refers to the duration or life span of trouble-free performance.
Different concretes require different degrees of durability depending on the exposure environment and properties desired. For example, concrete exposed to tidal seawater will have different requirements than indoor concrete.
Concrete will remain durable if:
  • The cement paste structure is dense and of low permeability
  • Under extreme condition, it has entrained air to resist freeze-thaw cycle.
  • It is made with graded aggregate that are strong and inert
  • The ingredients in the mix contain minimum impurities such as alkalis, Chlorides, sulphates and silt

Factors affecting durability of concrete

Durability of Concrete depends upon the following factors

Cement content

Mix must be designed to ensure cohesion and prevent segregation and bleeding. If cement is reduced, then at fixed w/c ratio the workability will be reduced leading to inadequatecompaction. However, if water is added to improve workability, water / cement ratio increases and resulting in highly permeable material.

Compaction

The concrete as a whole contain voids can be caused by inadequate compaction. Usually it is being governed by the compaction equipments used, type of formworks, and density of the steelwork

Curing

It is very important to permit proper strength development aid moisture retention and to ensure hydration process occur completely

Cover

Thickness of concrete cover must follow the limits set in codes

Permeability

It is considered the most important factor for durability. It can be noticed that higher permeability is usually caused by higher porosity .Therefore, a proper curing, sufficient cement, propercompaction and suitable concrete cover could provide a low permeability concrete

Types of Durability of Concrete

There are many types but the major Concrete Durability types are:
  1. Physical durability
  2. Chemical durability

Physical Durability

Physical durability is against the following actions
  1. Freezing and thawing action
  2. Percolation / Permeability of water
  3. Temperature stresses i.e. high heat of hydration

Chemical Durability

Chemical durability is against the following actions
  1. Alkali Aggregate Reaction
  2. Sulphate Attack
  3. Chloride Ingress
  4. Delay Ettringite Formation
  5. Corrosion of reinforcement

Comments

Post a Comment

Popular posts from this blog

civil engineering-->> overview of arches

Arches An arch is an opening spanned by a collection of wedge shaped pieces ( voussoirs ) which stay in position by pressing in on one another. The joints between the pieces appear to radiate from some central point lying within the opening, and sometimes from points which lie outside, so every type of arch has a characteristic curvature. The simplest and visually most natural shape for an arch is the semicircle but many other designs have been used. How an Arch "Works" The central voussoir ( keystone ) is traditionally the last to be set into position to "lock" the whole thing into a strong and stable structure. A keystone is not always necessary, however; there may be a joint at the apex instead, as is common in Gothic arches.  Gravity tries to pull the keystone downwards, but the thrust is carried on either side by the voussoirs immediately flanking it. These in turn have their total thrust carried through the whole semicircle of pieces in a sideways direc...
Post a Comment
Read more

civil engineering-->>Determinacy, Indeterminacy and Stability of Frames

Determinacy, Indeterminacy and Stability of Frames : Structural engineers must be able to apply judgment rather than stated rules. The most important aspect of structural design is not the ability to apply formulas or manipulate mathematics. The most important skill for the structural engineer is to be able to stand back, look at a drawing or sketch and determine whether a structure is stable, and if it is stable, to be able to determine how it will carry the applied loads. For a very complicated structure this might be more difficult and a computer can provide some help, but ultimately it is the skill and concern of a good structural engineer which produces good structural designs which have integrity. Another important closely related skill is the ability to determine whether, and to what degree, a structure is statically indeterminate. There really aren’t  many rules and rules may be difficult to apply in any case. For this reason, we need experience. A skilled structural...
1 comment
Read more

civil engineering-->> truss types

                                                                                                                           Modified-Queen-Scissors                                                          Baby Barn and Shed Trusses                                                                        floor truss       ...
1 comment
Read more