Development of a Field-Portable Near-Infrared Water-Cement Ratio Meter. Phase I: Investigation of Spectral Feasibility
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1999-06-25
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Abstract:In order to accurately predict the strength and durability of an adequately mixed and compacted concrete mix it is useful, if not necessary, to know the water-cement ratio of the fresh concrete mix. In this work near-infrared reflection spectroscopy has been applied to the analysis of freshly mixed cement and concrete. This work shows that it is feasible to determine the water-cement ratio of a batch of cement or concrete provided that the temperature and hardening time (i.e., amount of time passed since mixing) of the mixture is known. In the case of cement, 14 out of 15 cases showed a positive correlation between water-cement ratio and the analyte band. In the case of concrete five out of five cases showed a positive correlation between water-cement ratio and the analyte band. The admixture agents Daravair and Daracem were undetectable when mixed at levels at three and 16 fluid ounces per 100 pounds of cement, respectively. The near-infrared spectra of concrete were not strongly affected by the presence of coarse aggregates. The effect of coarse aggregates on near-infrared spectra was to increase scattering that, in turn, increased baseline tilt at shorter wavelength. This effect can be overcome by baseline correction and does not necessitate the use of a probetip sheath. 10 Figures, 3 Tables, 2 appendices, 42p.
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