Quick and nondestructive determination of curestate and water-to-cement (w/c) ratio in fresh Portland cementbased materials is an important issue in the construction industry since the compressive strength of these materials is significantly influenced by w/c ratio. This is especially true since current techniques are not reliable and require a priori testing of test specimens as calibration for subsequent on-site monitoring of a cast in-place structure. Recently, the sensing of Portland cementbased materials using microwave techniques has received much attention. Microwave nondestructive techniques have already shown the potential for determining w/c ratio, sand-to-cement (s/c) ratio and coarse aggregate-to-cement (ca/c) ratio in cured cement paste, mortar, and concrete. In this paper, the results of a study demonstrating the potential for early determination of cure-state and w/c ratio of Portland cement-based materials, using a near-field microwave inspection technique, are presented. This technique utilizes the reflection properties of an open-ended rectangular waveguide probe radiating into Portland cementbased materials at 5 GHz (G-band) and 10 GHz (X-band). The results demonstrate the ability of near-field microwave sensing techniques to determine the state of hydration of cement paste and concrete with 0.50 and 0.60 w/c ratios and varying aggregate contents. In fact, it is shown that cement-based materials that have been moist-cured for three days and then left to cure at ambient temperature and humidity for the remainder of the prescribed 28-day curing period, are fully cured after only 12 days. An empirical formula relating the magnitude of reflection coefficient to the curing time is presented. Using this empirical relationship, the w/c ratio of cement paste and concrete can be unambiguously determined when daily monitoring of the reflection properties of the specimens is performed. The potential for utilizing this technique for on-site monitoring of cure-state and w/c ratio (and compressive strength) determination is also discussed.


Electrical and Computer Engineering


National Science Foundation (U.S.)
Electric Power Research Institute

Keywords and Phrases

10 GHz; 5 GHz; G-Band; X-Band; Cement Paste; Cements (Building Materials); Compressive Strength; Concrete; Condition Monitoring; Construction Industry; Cure-State Monitoring; Curing Time; Fresh Portland Cement-Based Materials; Hydration State; Inspection; Microwave Inspection Technique; Microwave Reflectometry; Moisture Measurement; Near-Field Microwave Techniques; Nondestructive Determination; Nondestructive Testing; Onsite Monitoring; Open-Ended Rectangular Waveguide Probe; Reflection Coefficient; Reflection Properties; Varying Aggregate Content; Water-To-Cement Ratio Determination; Water/Cement Ratio; Infrastructure Testing And Cement-Based Material Evaluation; Material Characterization

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 1998 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jun 1998