Quality control of autoclaved aerated concrete by means of X‐ray diffraction

Abstract

X-ray diffraction is a very powerful tool for the characterization of crystalline phases in multiphase materials. In recent years, this method has been established in numerous industrial branches for quality control in processes where materials consisting of crystalline phases are produced. For instance, cementitious materials exhibit up to 20 different phases of which each is responsible for certain physical and chemical properties of the product. Knowing and understanding the phase assemblage of a material and the effects on its behavior allows the optimization of a product with respect to properties, quality, and production costs. The cement industry is using this knowledge by characterizing the materials along the production chain from raw materials to the final products by means of X-ray diffraction. Autoclaved aerated concretes (AACs) consist mainly of crystalline and non-crystalline solids, and for that reason, they have been subject to many crystallographic studies using X-ray diffraction. Although the phase assemblage is regularly investigated, only little knowledge gained from these studies is transferred to production sites in order to monitor the manufacturing process. The crystallographic phase assemblage of autoclaved aerated concrete could be examined by X-ray diffraction on a routine basis in order to maintain constant product quality and, thus, even material properties. Another beneficial aspect of this method is that it enables choosing more economic raw materials and optimizing process parameters. K E Y W O R D Sphase assemblage, quality control, X-ray diffraction

Fast X-ray diffraction (XRD) tomography for enhanced identification of materials

“…On the flip side, there is much interest in XRD tomography for domains other than airport security, such as healthcare or manufacturing quality control. Examples include imaging defects in concrete 49 and metals 50 , especially for quality control in 3D printing 51 . Whereas transmission tomography has a resolution of , diffraction tomography can reveal details in the range.…”

Fast X-Ray Diffraction (XRD) Tomography for Enhanced Identification of Materials

“…The scan example that we have shown is fairly generic, and could be further optimized for more specific applications in domains other than security, for example healthcare or manufacturing quality control. Candidate areas include imaging defects in concrete [37] and metals [38], especially for quality control in 3D printing [39], as well as revealing the nanostructure of bones [40] and calcifications in soft tissues like breast [41]. The nanostructure of materials can be inferred by fitting a molecular model to the reconstructed diffraction pattern.…”

Gravel wash mud, a quarry waste material as supplementary cementitious material (SCM)

“…in [64], shows that the main crystalline phases identified were quartz, muscovite, followed by illite and kaolinite as clay minerals, hematite and the amorphous portions. The increase of the calcination temperature led to the transformation of the clay minerals into XRD amorphous phases.…”

“…Furthermore, the accurate and direct detection of non-crystalline matter in a powder sample is not possible with X-ray powder diffraction analysis, as those phases do not generate characteristic reflections peaks (X-ray amorphous). However, due to the likeliness of the presence of non-crystalline content (amorphous phases) in the GWM powders, its amorphous quantity is computed using quartz at 35% as an internal reference [64]. This procedure of quantitative phase analysis of amorphous content assumes that the internal reference quartz homogenously distributed within all powder samples, a narrow particle size distribution of all phases is ensured and a random orientation of the crystallites is assured to reduce preferred orientation effects [51,64].…”

“…However, due to the likeliness of the presence of non-crystalline content (amorphous phases) in the GWM powders, its amorphous quantity is computed using quartz at 35% as an internal reference [64]. This procedure of quantitative phase analysis of amorphous content assumes that the internal reference quartz homogenously distributed within all powder samples, a narrow particle size distribution of all phases is ensured and a random orientation of the crystallites is assured to reduce preferred orientation effects [51,64]. With the known amount of the internal reference Wref and its amount from the quantitative analysis Wq, the percentage of the amorphous content, Wamorphous, can be calculated as followed, adjusted from [51,64]:…”