Reader, University of Sheffield, Sheffield,
Lecturer, National University of Singapore, Kent Ridge, Singapore,
The development of a three-dimensional conductivity probe, based on the measurement of electrical conductance between electrodes, to evaluate the setting time of fresh concrete and the variation of moisture content with time in hardened concrete is reported. The construction and calibration of the conductivity probe are described, and a calibration curve translating electrical conductance measurements into available moisture content is presented. Tests are then reported to evaluate the setting time of fresh concrete, and these are related to internal temperature variations. These tests are then extended to study moisture variations in hardened concrete under load and no-load conditions in both sealed and unsealed environments. These measurements taken for up to two years are related to internal humidity measurements. The results show that the conductivity probe is a simple and inexpensive device that gives quantitative information in any direction and possesses qualities of accuracy, reliability, long-term stability, and local resolution.
Paper ID: CCA10231J