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:
- clear documentation of the limitations of the Bogue methodology;
- development and validation of training materials (SRM's 2686,2687,2688,2686a) using X-ray diffraction and scanning electron microscopy;
- 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)
- calibration of the XRD techniques against the Bogue; and
- deployment of the newer XRD techniques to predict key elements of material performance, such as heat of hydration.