Title: Optical Moisture Measurement in Concrete Aggregates

Author(s): Taisto Haavasoja

Publication: NCR

Volume: 44

Issue: 4

Appears on pages(s): 45-54

Keywords: Aggregate, moisture, water content, optical sensor, infra-red spectroscopy.

DOI:

Date: 12/15/2011

Abstract:
We have studied feasibility of using optical means to measure aggregate moisture content. We measured optical response of some commonly used aggregates at around 1.5 μm wavelengths. The results suggest that this wavelength range enables nominal accuracy of about 0.1% in moisture by weight. One of the major benefits in optical technology is a noncontact measurement allowing practically a onetime calibration procedure and a long lifetime of the sensor due to solid state design. On the challenge side there is a need to protect the sensor window from dust and condensing of moisture. These issues have been field tested in concrete plants and a long term accuracy of 0.3% is realistic in practise. We also measured the optical response to a maximum variation in aggregate grading.