Foundation, Concrete and Earthquake Engineering

What is Impact of Over Vibration of Concrete Mix?

During mixing process of concrete air get entrapped into the concrete mix. This entrapping process also happened during transporting and placing of concrete. Here in this post we will discuss about over compaction of concrete using mechanical compactor widely known as vibrator. There have different types of vibrator. We will discuss the vibration impact in general irrespective of types of vibrator.

At first we will learn what is the purpose of using vibrator?

This is simple vibrators are used to remove entrapped air from concrete mix completely. Now come to the point over vibration. We are not concerned with the well proportioned and designed concrete mix. As such mix with normal weight aggregate generally do not require extended vibration and if extended vibration is undertaken it will not produce any harm to concrete mix. But for many conditions of placing concrete sometimes workability of the mix are expected to be high. Over vibration to such concrete mix is harmful. Here a list of conditions where over vibration are concerned are provided:
Accumulation of air bubble to the surface of  over vibrated concrete

A. Mortar quantity is much more than voids present in coarse aggregate.

B. Unexpected grading of aggregate

C. Too workable mix

The harm that over vibration does is segregation. These exceeding vibration results:

A. The smaller and lighter constituents of concrete mix come out to the surface.

B. Laitance phenomenon is observed on the surface.

C. Mortar is observed to leak through the formworks where they found defects in joints.

D. Poor abrasive resistance of concrete

E. Sometimes a weaken plane in concrete is observed

F. The concrete becomes weak against exterior agents of concrete deterioration like frost etc.

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