Cement Characteristics by Direct Phase Assessment

Worldwide, cement/concrete development and utilization represent significant measurable fractions of national GDP's. Over-reliance on dated modes of assessing materials composition and performance have impeded the accurate prediction, and enhancement, of concrete performance and service life. The recurring problem for the U.S. cement and concrete industry is that either appropriate performance-based standards do not exist, or that the existing standards are not based upon measurements that reliably relate to actual performance.

The major research goal is the accurate prediction of field performance metrics from accurate characterization of mineralogical composition and texture. Compounding characterization and prediction problems is the widespread reliance since the 1930's on the Bogue estimates of composition derived from bulk oxide measurements. This approach has long been known to be inaccurate owing to chemical composition biases and the presence of mineral species not specified in the paradigm. Over the past decade, NIST has been documenting the utility of direct X-ray diffraction analysis of cementitious materials as a superior alternative to the existing technology. X-ray diffraction enables the direct identification and quantification of the mineral phases, achieving significantly greater accuracy and precision than the Bogue method. An ongoing cooperative program of research and and development with ASTM and industry has included the following key elements:

1. clear documentation of the limitations of the Bogue methodology;
2. development and validation of training materials (SRM's 2686,2687,2688,2686a) using X-ray diffraction and scanning electron microscopy;
3. development of ASTM XRD-based test methods (ASTM C1365, Quantitative X-ray Powder Diffraction Analysis of Portland Cements, currently the only standardized technique for cement/clinker in the world)
4. calibration of the XRD techniques against the Bogue; and
5. deployment of the newer XRD techniques to predict key elements of material performance, such as heat of hydration.

Paul Stutzman, Stefan Leigh, Amelia Tebbe.
"Uncertainty Analysis of Bogue Calculations for Cement Phase Estimates and Classification".
Unpublished presentation. August, 2007.

Paul Stutzman, Stefan Leigh.
"Phase Composition Analysis of the NIST Reference Clinkers by Optical Microscopy and X-ray Powder Diffraction."
NIST Technical Note 1441, September 2002, 44 pp. 

Paul Stutzman, Germaine Lespinasse, Stefan Leigh.
"Compositional Analysis and Certification of NIST Reference Clinker Material 2686a."
NIST Technical Note 1602, September 2008, 48 pp. 

Paul Stutzman, Stefan Leigh.
"Phase Analysis of Hydraulic Cements by X-Ray Powder Diffraction: Precision, Bias, and Qualification."
Journal of ASTM International, 2007, vol 4., no. 5,
http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/JAI/PAGES/JAI101085.htm
2208 ASTM P.H. Bates Memorial Award. 

Paul Stutzman, Stefan Leigh.
"Statistical Calibration of ASTM C150 Bogue-Derived Phase Limits to Directly Determined Phases by Quantitative X-Ray Powder Diffraction."
Journal of ASTM International, 2010, vol 7., no. 7,
http://www.astm.org/DIGITAL_LIBRARY/JOURNALS/JAI/PAGES/JAI103046.htm
www.astm.org. 

Paul Stutzman, Stefan Leigh, Kendall Dolly, and Haleh Azari.
"Statistical Modeling of Heat of Hydration Using Phase and Fineness."
DRAFT REPORT for the National Cooperative Highway Research Program, Transportation Research Board, National Research Council.
April 2009.