Analysis of Water Content in Bricks Using FFT (Fast Fourier Transform) Analyzer

Abstract

Each body, structure and material vibrates with certain frequency. It is necessary to know the nodal frequency of certain body, structure or material to know its certain characteristics like damping, resonance frequency, density, body features etc. It is useful for improving the design of a structure and reliability of the structure in design point of view. The vibrating characteristic of a specific body depends on its geometrical features like its length, breadth, height etc. Such a material in construction industry is brick.

Brick is one of the most used structural materials, so it is necessary to identify its durability and reliability before use in construction. Water absorption is one of the property of all types of bricks, the allowable water absorption for standard brick, after immersion in cold water for 24 hours, should not be more than 20 percent of its weight up to 2^nd and 3^rd class bricks and 15 percent by weight for higher class brick. So it is necessary to measure the water content of bricks before using in field of construction to avoid any problems.

The system we are using to measure the water content of brick is natural frequency, which is new in field of construction. Natural frequency is defined as the frequency within which the system vibrates when it is not intended to a repeated or continuous cycle of external force. The basic idea behind this technology is that modal parameters of brick like (geometrical parameters, material properties) are the functions of the physical properties of the brick. Variations in the physical properties will cause in the variations which are measurable in the modal properties. By use of natural frequency to detect water content will be very useful for onsite detection of moisture.