Scanning X-ray Microdiffraction Research Articles

Multiscale structure of cellulose microfibrils in regenerated cellulose fibers

Cellulose in solution can be assembled into textile fibers by wet-spinning (Viscose etc.) or dry-jet wet spinning (Lyocell, Ioncell etc.), which leads to significant differences in the mechanical properties of fibers. We use scanning X-ray microdiffraction (SXM) to reveal regenerated fibers having a “skin-core” morphology. The “core” region comprises microfibrils (MFs) with ~100 nm in diameter. The cellulose forms elementary fibrils having a ribbon-like cross sectional shape of about 6 × 2 nm, which are packed into MFs. Our SXM studies demonstrate that MFs within Ioncell fibers are composed of elementary fibrils with homogeneous morphologies. Furthermore, the stacking of cellulose molecular sheets within elementary fibrils of Viscose fibers is preferentially along the 010 direction, while those of Ioncell fibers preferably stack in the 1–10 direction. The better structural regularities and distinct morphologies of elementary fibrils give Ioncell fibers enhanced mechanical properties and a wet strength far superior to those of Viscose fibers.

Variation in the hierarchical structure of lignin-blended cellulose precursor fibers

Regenerated cellulose fibers have been considered as potential precursor fibers for carbon fibers because of their balanced cost and performance. Increased attention has been paid to blending lignin with the regenerated cellulose to generate precursor fibers which render good mechanical properties and higher carbon yield. The mechanical properties of carbon fibers have been found closely correlated to the structure of precursor fibers. However, the effects of lignin blending on molecular- and morphological structure of the precursor are still unclear. This study aims at clarifying the structural information of lignin–cellulose precursor fibers from molecular level to mesoscale by scanning X-ray microdiffraction. We present the existence of a skin–core morphology for all the precursor fibers. Increase of lignin content in precursor fiber could reduce the portion of skin and cause obvious disorder of the meso- and molecular structure. By correlating structural variations with lignin blending, 30% lignin blending has been found as a potential balance point to obtain precursor fibers maintaining structural order together with high yield rate.

Scanning X-ray microdiffraction mapping of fibrillar polymorphs in Alzheimer's disease

Scanning X-ray microdiffraction mapping of fibrillar polymorphs in Alzheimer's disease

Mapping the Spatial Distribution of Fibrillar Polymorphs in Human Brain Tissue.

Alzheimer’s disease (AD) is a neurodegenerative disorder defined by the progressive formation and spread of fibrillar aggregates of Aβ peptide and tau protein. Polymorphic forms of these aggregates may contribute to disease in varying ways since different neuropathologies appear to be associated with different sets of fibrillar structures and follow distinct pathological trajectories that elicit characteristic clinical phenotypes. The molecular mechanisms underlying the spread of these aggregates in disease may include nucleation, replication, and migration all of which could vary with polymorphic form, stage of disease, and region of brain. Given the linkage between mechanisms of progression and distribution of polymorphs, mapping the distribution of fibrillar structures in situ has the potential to discriminate between mechanisms of progression. However, the means of carrying out this mapping are limited. Optical microscopy lacks the resolution to discriminate between polymorphs in situ, and higher resolution tools such as ssNMR and cryoEM require the isolation of fibrils from tissue, destroying relevant spatial information. Here, we demonstrate the use of scanning x-ray microdiffraction (XMD) to map the locations of fibrillar polymorphs of Aβ peptides and tau protein in histological thin sections of human brain tissue. Coordinated examination of serial sections by immunohistochemistry was used to aid in the interpretation of scattering patterns and to put the observations in a broader anatomical context. Scattering from lesions in tissue shown to be rich in Aβ fibrils by immunohistochemistry exhibited scattering patterns with a prototypical 4.7 Å cross-β peak, and overall intensity distribution that compared well with that predicted from high resolution structures. Scattering from lesions in tissue with extensive tau pathology also exhibited a 4.7 Å cross-β peak but with intensity distributions that were distinct from those seen in Aβ-rich regions. In summary, these observations demonstrate that XMD is a rich source of information on the distribution of fibrillar polymorphs in diseased human brain tissue. When used in coordination with neuropathological examination it has the potential to provide novel insights into the molecular mechanisms underlying disease.

Enabling curvable silicon photovoltaics technology using polycarbonate-sandwiched laminate design

Cracks in brittle silicon solar cells (wafers) are a major concern in the solar photovoltaics (PV) industry. Because of the slicing of the wafers from large ingots and further stressing during subsequent operations such as soldering and laser cutting, silicon (Si) solar cells often contain microcracks that may grow into larger cracks during cell integration into a PV module. Through our previous works on residual stress probing using synchrotron scanning X-ray microdiffraction (μSXRD) experiments, finite-element modelling of the manufacturing sequences (from cells to laminate) have been validated to predict the stresses highly accurately in the conventional PV module design (glass-cell-backsheet). In the present work, we use those validated finite element methodologies to predict the residual stresses in a novel PV module design in which silicon cells are sandwiched between polycarbonate (PC) sheets – the lightweight PC-cell-PC module. It is shown that the post-lamination residual stresses in the cells are highly compressive, which is good for inhibiting crack growth. This feature also enables the novel PV modules to be curved without the cells cracking, which favors its application to building-integrated or automotive-integrated PV modules. We demonstrate the basic feasibility of the concept – with mini curved PC-sandwiched laminates, showing the upper bounds of the achievable curvature (and their associated stress levels) without any observable cracks in the cells as determined by electroluminescence imaging. The curving here is utilized to demonstrate the larger extent of mechanical stresses the same silicon solar cells could withstand with the PC-PC design.

In Situ Studies of Fibrillar Polymorphs in Alzheimer's Disease

Aggregates of Aβ peptides and tau protein are defining features of Alzheimer's disease (AD) but the contribution of these structures to the etiology of disease remains uncertain. High resolution structures of fibrillar polymorphs have provided a basis for studies of disease, but fall short of defining the molecular mechanisms underlying disease progression. Evidence is accumulating that the peptide conformation within fibrils correlates with disease subtype and suggests that protofilament conformation represents the physical embodiment of a ‘strain’ of AD. Within a single strain the fold of peptides may be invariant. But the fibrils are capable of polymorphism that includes variation in the packing of protofilaments into fibrils; the pitch of the resultant fibrils and the higher order organization of plaques into which they aggregate. These intra-strain polymorphisms are divided by low-energy barriers allowing multiple configurations to coexist within a single preparation or tissue. Clinical presentation of different strains may be determined by variation in the way different protofilament structures generate relevant toxic species, be they monomers, oligomers or higher order structures. To better understand their role in disease, in situ studies of fibril structure have been carried out on histological thin sections of human brain tissue. Scanning x-ray microdiffraction is providing information on the variation of fibrillar polymorphism at sub-cellular length scales and makes possible mapping the distribution of polymorphs within tissue. Scattering in the wide-angle regime produces information on fibrillar twist. Scattering in the small-angle regime can be used to generate the cross-sectional shape of fibrils. Mapping the variation of these structural parameters across and among plaques and tangles in different regions of the brain provides insight into the development and evolution of neurodegenerative lesions.

Evidence of charge density wave transverse pinning by x-ray microdiffraction

Incommensurate charge density waves (CDW) have the extraordinary ability to display non-Ohmic behavior when submitted to an external field. The mechanism leading to this nontrivial dynamics is still not well understood, although recent experimental studies tend to prove that it is due to solitonic transport. Solitons could come from the relaxation of the strained CDW within an elastic-to-plastic transition. However, the nucleation process and the transport of these charged topological objects have never been observed at the local scale until now. In this paper, we use in situ scanning x-ray microdiffraction with micrometer resolution of a ${\mathrm{NbSe}}_{3}$ sample designed to have sliding and nonsliding areas. Direct imaging of the charge density wave deformation is obtained using an analytical approach based on the phase gradient to disentangle the transverse from the longitudinal components over a large surface $(90\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\text{m})$. We show that the CDW dissociates itself from the host lattice in the sliding regime and displays a large transverse deformation, ten times larger than the longitudinal one and strongly dependent on the amplitude and the direction of the applied currents. This deformation continuously extends across the macroscopic sample dimensions, over a distance 10 000 times greater than the CDW wavelength despite the presence of strong defects while remaining strongly pinned by the lateral surfaces. This two-dimensional quantitative study highlights the prominent role of the shear effect, which should be significant in the nucleation of solitons.

Investigation on phase transition from flow-induced oriented form II to I in isotactic polybutene-1 with in-situ microbeam X-ray diffraction technique

Spontaneously phase transition from form II to I in isotactic polybutene-1 (iPB-1) products during storage at room temperature after processing limited their application. Investigations on phase transition in iPB-1 have practical importance, especially on oriented iPB-1 as oriented form II generated during processing where intense flow field is always imposed. The effects of flow on phase transition were studied with synchrotron radiation scanning X-ray microdiffraction (SR-μSXRD) technique with beam size of 4.5 × 5.2 μm2 in the present work. Localized flow-field was imposed by pulling glass fiber through undercooled melt. Benefiting from the high resolution of SR-μSXRD technique, the formation of fibrillar and oriented form II (cIIf and cIIo) were identified. The transformation from cIIf to fibrillar form I (cIf) completed in about 40 min, while cIIo transformed into oriented form I (cIo) partially in about 186 min. Quantitative analysis on SR-μSXRD result showed that crystallographic lattice dimension of cIIf changed comparing with that of cIIo, where a and b increased while c decreased in cIIf. An obvious correlation between crystallographic lattice deformation and phase transition kinetics was is identified. Local internal stress plays an important role in promoting the phase transition kinetics, as the stress transmission efficiency in cIIf with rod-like morphology would be higher than that in cIIo with lamellar morphology.

Scanning X-ray microdiffraction of decellularized pericardium tissue at increasing glucose concentration.

Blood glucose supplies energy to cells and is critical for the human brain. Glycation of collagen, the nonenzymatic formation of glucose‐bridges, relates to diseases of aging populations and diabetics. This chemical reaction, together with its biomechanical effects, has been well studied employing animal models. However, the direct impact of glycation on collagen nano‐structure is largely overlooked, and there is a lack of ex vivo model systems. Here, we present the impact of glucose on collagen nanostructure in a model system based on abundantly available connective tissue of farm animals. By combining ex vivo small and wide‐angle X‐ray scattering (SAXS/WAXS) imaging, we characterize intra‐ and inter‐molecular parameters of collagen in decellularized bovine pericardium with picometer precision. We observe three distinct regimes according to glucose concentration. Such a study opens new avenues for inspecting the effects of diabetes mellitus on connective tissues and the influence of therapies on the resulting secondary disorders.

Thermomechanical residual stress evaluation in multi-crystalline silicon solar cells of photovoltaic modules with different encapsulation polymers using synchrotron X-ray microdiffraction

Photovoltaic (PV) module reliability issues, due to silicon cell cracking, are gaining more and more attention due to increasing demand for solar power and reduction of cell thickness to reduce cost. Recent reports show significant effect of encapsulation polymer material on cell cracks leading to the idea of tailoring encapsulation materials for more reliable PV modules. This paper investigates the effect of encapsulation modulus on the cell residual stress using Synchrotron scanning X-ray microdiffraction (µSXRD), which has been proven to be an effective technique to probe the stress in silicon solar cells, especially once they are encapsulated. The post lamination residual stress in the encapsulated multi-crystalline silicon (mc-Si) solar cells was reported for the first time using µSXRD in this manuscript and provide quantitative evaluation of the effect of encapsulation modulus on the cell residual stress. Further, simple approximate finite element (FE) model was also developed to evaluate the effect of the encapsulation polymer on the cell stress. The FE simulations predict the trend of the stress variation with encapsulation polymer modulus very well. Dynamic mechanical analysis and rheological testing of the encapsulation polymers was also performed to correlate the polymer behaviour with the experimental and simulated stresses. Both experimental and simulation results show a similar trend of significant cell stress variation with encapsulation polymer modulus. In the case of external loading, the temperature of load application is observed to be very significant as it dictates the elastic state of the encapsulant, leading to critical conclusion that the encapsulant needs to be selected based on elastic behaviour over the temperature history of the encapsulant during module fabrication and operation. The results and discussion presented are expected to be very useful for development of more reliable PV modules.

An Alternative Scenario on the Origin of Ultra-High Pressure (UHP) and Super-Reduced (SuR) Minerals in Ophiolitic Chromitites: A Case Study from the Mercedita Deposit (Eastern Cuba)

The origin of the assemblage of ultra-high pressure (UHP), super-reduced (SuR) and several crustally derived phases in ophiolitic chromitites is still hotly debated. In this paper, we report, for the first time, this assemblage of phases in ophiolitic chromitites of the Caribbean. We studied the Mercedita chromitite deposit in the eastern Cuban ophiolitic complexes. The mineral phases were characterized using microRaman spectroscopy, energy-dispersive spectroscopy with a scanning electron microscope (SEM-EDS), X-ray microdiffraction and electron microprobe analyses. Mineral concentrates were prepared using hydroseparation techniques. We have identified oriented clinopyroxene lamellae in chromite, oriented rutile lamellae in chromite, moissanite hosted in the altered matrix of the chromitite, graphite-like amorphous carbon, corundum and SiO2 hosted in healed fractures in chromite grains, and native Cu and Fe–Mn alloy recovered in heavy-mineral concentrates obtained by hydroseparation. This assemblage may correspond to UHP-SuR conditions, implying recycling of chromitite in the mantle or formation of the chromite grains at deep mantle depths, followed by emplacement at a shallow level in the mantle. However, the chromitite bodies contain gabbro sills oriented parallel to the elongation of the chromitite lenses, and these show no evidence of HP/UHP metamorphism. Therefore, the identified “exotic” phases may not be indicative of UHP. They formed independently as oriented clinopyroxene lamellae in chromite during cooling (clinopyroxene and rutile), in super-reduced microenvironments during the serpentinization processes, and by transference of subducted crustal material to the mantle wedge via cold plumes.

Shear-induced precursors in polyethylene: An in-situ synchrotron radiation scanning X-ray microdiffraction study

Localized shear flow was imposed by pulling glass fiber in polyethylene (PE) melt below and above its equilibrium melting point (141.6 °C). Immediately after the cessation of shear, the structure around the fiber was investigated with in-situ synchrotron radiation scanning X-ray microdiffraction (SR-μSXRD), which had spot area of 4.2 × 4.5 μm2 and step size of 6 μm. Results indicate that crystalline precursors are induced below equilibrium melting point, as evidenced by the occurrence of crystalline diffractions. Whilst at temperature above equilibrium melting point, no crystalline diffraction is observed. SR-μSXRD measurements on the crystallization behaviors at 127 °C after shearing at 145 °C suggest that non-crystalline precursors are induced, which is supported by three evidences. (i) The occurrence of crystallization near the fiber surface implies shear-induced formation of precursors at 145 °C since the fiber has no ability to induce crystallization at quiescent condition; (ii) No crystalline diffraction is detected immediately after cessation of shear at 145 °C; (iii) The necessity of induction time for the precursors to transform into crystalline nuclei further demonstrates the non-crystalline nature of precursors. The concentration of precursors is observed to reduce with increasing shearing temperature, as evidenced by twisting degree of lamellar crystals after isothermally crystallized at 127 °C.

Myelin structure in unfixed, single nerve fibers: Scanning X-ray microdiffraction with a beam size of 200 nm

Previous raster-scanning with a 1μm X-ray beam of individual, myelinated fibers from glutaraldehyde-fixed rat sciatic nerve revealed a spatially-dependent variation in the diffraction patterns from single fibers. Analysis indicated differences in the myelin periodicity, membrane separations, distribution of proteins, and orientation of membrane lamellae. As chemical fixation is known to produce structural artifacts, we sought to determine in the current study whether the structural heterogeneity is intrinsic to unfixed myelin. Using a 200nm-beam that was about five-fold smaller than before, we raster-scanned individual myelinated fibers from both the peripheral (PNS; mouse and rat sciatic nerves) and central (CNS; rat corpus callosum) nervous systems. As expected, the membrane stacking in the internodal region was nearly parallel to the fiber axis and in the paranodal region it was perpendicular to the axis. A myelin lattice was also frequently observed when the incident beam was injected en face to the sheath. Myelin periodicity and diffracted intensity varied with axial position along the fiber, as did the calculated membrane profiles. Raster-scanning with an X-ray beam at sub-micron resolution revealed for the first time that the individual myelin sheaths in unfixed nerve are heterogeneous in both membrane structure and packing.

The impact of alterations in lignin deposition on cellulose organization of the plant cell wall.

BackgroundCoordination of synthesis and assembly of the polymeric components of cell walls is essential for plant growth and development. Given the degree of co-mingling and cross-linking among cell wall components, cellulose organization must be dependent on the organization of other polymers such as lignin. Here we seek to identify aspects of that codependency by studying the structural organization of cellulose fibrils in stems from Arabidopsis plants harboring mutations in genes encoding enzymes involved in lignin biosynthesis. Plants containing high levels of G-lignin, S-lignin, H-lignin, aldehyde-rich lignin, and ferulic acid-containing lignin, along with plants with very low lignin content were grown and harvested and longitudinal sections of stem were prepared and dried. Scanning X-ray microdiffraction was carried out using a 5-micron beam that moved across the sections in 5-micron steps and complete diffraction patterns were collected at each raster point. Approximately, 16,000 diffraction patterns were analyzed to determine cellulose fibril orientation and order within the tissues making up the stems.ResultsSeveral mutations—most notably those exhibiting (1) down-regulation of cinnamoyl CoA reductase which leads to cell walls deficient in lignin and (2) defect of cinnamic acid 4-hydroxylase which greatly reduces lignin content—exhibited significant decrease in the proportion of oriented cellulose fibrils in the cell wall. Distinctions between tissues were maintained in all variants and even in plants exhibiting dramatic changes in cellulosic order the trends between tissues (where apparent) were generally maintained. The resilience of cellulose to degradative processes was investigated by carrying out the same analysis on samples stored in water for 30 days prior to data collection. This treatment led to significant loss of cellulosic order in plants rich in aldehyde or H-lignin, less change in wild type, and essentially no change in samples with high levels of G- or S-lignin.ConclusionsThese studies demonstrate that changes in lignin biosynthesis lead to significant disruption in the orientation and order of cellulose fibrils in all tissues of the stem. These dramatic phenotypic changes, in mutants with lignin rich in aldehyde or H-units, correlate with the impact the mutations have on the enzymatic degradation of the plant cell wall.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0540-z) contains supplementary material, which is available to authorized users.

Investigation of the inverse piezoelectric effect of trabecular bone on a micrometer length scale using synchrotron radiation

In the present paper we have investigated the impact of electro stimulation on microstructural parameters of the major constituents of bone, hydroxyapatite and collagen. Therapeutic approaches exhibit an improved healing rate under electric fields. However, the underlying mechanism is not fully understood so far. In this context one possible effect which could be responsible is the inverse piezo electric effect at bone structures. Therefore, we have carried out scanning X-ray microdiffraction experiments, i.e. we recorded X-ray diffraction data with micrometer resolution using synchrotron radiation from trabecular bone samples in order to investigate how the bone matrix reacts to an applied electric field. Different samples were investigated, where the orientation of the collagen matrix differed with respect to the applied electric field. Our experiments aimed to determine whether the inverse piezo electric effect could have a significant impact on the improved bone regeneration owing to electrostimulative therapy. Our data suggest that strain is in fact induced in bone by the collagen matrix via the inverse piezo electric effect which occurs in the presence of an adequately oriented electric field. The magnitude of the underlying strain is in a range where bone cells are able to detect it. Statement of SignificanceIn our study we report on the piezoelectric effect in bone which was already discovered and explored on a macro scale in the 1950. Clinical approaches utilize successfully electro stimulation to enhance bone healing but the exact mechanisms taking place are still a matter of debate. We have measured the stress distribution with micron resolution in trabecular bone to determine the piezo electric induced stress. Our results show that the magnitude of the induced stress is big enough to be sensed by cells and therefore, could be a trigger for bone remodeling and growth.

Myelin organization in the nodal, paranodal, and juxtaparanodal regions revealed by scanning x-ray microdiffraction.

X-ray diffraction has provided extensive information about the arrangement of lipids and proteins in multilamellar myelin. This information has been limited to the abundant inter-nodal regions of the sheath because these regions dominate the scattering when x-ray beams of 100 µm diameter or more are used. Here, we used a 1 µm beam, raster-scanned across a single nerve fiber, to obtain detailed information about the molecular architecture in the nodal, paranodal, and juxtaparanodal regions. Orientation of the lamellar membrane stacks and membrane periodicity varied spatially. In the juxtaparanode-internode, 198–202 Å-period membrane arrays oriented normal to the nerve fiber axis predominated, whereas in the paranode-node, 205–208 Å-period arrays oriented along the fiber direction predominated. In parts of the sheath distal to the node, multiple sets of lamellar reflections were observed at angles to one another, suggesting that the myelin multilayers are deformed at the Schmidt-Lanterman incisures. The calculated electron density of myelin in the different regions exhibited membrane bilayer profiles with varied electron densities at the polar head groups, likely due to different amounts of major myelin proteins (P0 glycoprotein and myelin basic protein). Scattering from the center of the nerve fibers, where the x-rays are incident en face (perpendicular) to the membrane planes, provided information about the lateral distribution of protein. By underscoring the heterogeneity of membrane packing, microdiffraction analysis suggests a powerful new strategy for understanding the underlying molecular foundation of a broad spectrum of myelinopathies dependent on local specializations of myelin structure in both the PNS and CNS.

Ion beam induced spinodal decomposition and amorphization in the immiscible bilayer system UMo/Mg

High density fuel uranium–molybdenum (UMo) alloy embedded in an Mg matrix has been investigated as a candidate material for high density fuel of research reactors. UMo/Mg bilayers were prepared and irradiated with swift heavy ions to simulate damages created by fission fragments during in-pile irradiation. Scanning transmission electron microscopy and X-ray microdiffraction reveal the micro-structural evolution during irradiation including amorphization and spinodal decomposition. Spinodal decomposition during irradiation results in a chessboard-like pattern with a U-rich and a U-poor phase. In addition, an irradiation-induced phase U0.9Mg0.1 has been found. In comparison to UMo embedded in an Al matrix, the diffusion reactions and the amorphous region are well detained.

Flow-Induced Precursors of Isotactic Polypropylene: An in Situ Time and Space Resolved Study with Synchrotron Radiation Scanning X-ray Microdiffraction

Shear-induced precursors obtained by fiber pulling with high shear rate in undercooled melts of isotactic polypropylene (iPP) at a wide temperature range were investigated by highly time and space resolved synchrotron radiation scanning X-ray microdiffraction (SR-μSXRD). X-ray diffraction patterns in spot area of 4.9 × 5.3 μm2 were obtained by scanning proximities around the fiber with step size of 7 μm immediately after shear and during the sequent crystallization process. The crystallinity derived from SR-μSXRD indicates that the structure of precursors was determined by shear temperature, providing a high shear rate was imposed. At shear temperatures around or below the melting temperature, the presence of crystal diffraction immediately after shear indicates the formation of crystalline precursors with reduced density by increasing shear temperature. At shear temperatures in between melting and equilibrium melting temperature, the formation of noncrystalline precursors is supported by three evidence: (i) formation of shear-induced ordered structure indicated by preference of crystallization on fiber surface; (ii) absence of crystal signal immediately after shear; (iii) induction time necessary for transforming noncrystalline precursor into crystal. The experimental results suggest that the structure of noncrystalline precursors probably is aggregates of partially ordered chain segments which orient along the shear direction.

Tensile strain mapping in flat germanium membranes

Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge.

Characterization of morphology and hydration products of high-volume fly ash paste by monochromatic scanning x-ray micro-diffraction (μ-SXRD)

The present study focuses on identification and micro-structural characterization of the hydration products formed in high-volume fly ash (HVFA)/portland cement (PC) systems using monochromatic scanning x-ray micro-diffraction (μ-SXRD) and SEM-EDS. Pastes with up to 80% fly ash replacement were studied. Phase maps for HVFA samples using μ-SXRD patterns prove that μ-SXRD is an effective method to identify and visualize the distribution of phases in the matrix. μ-SXRD and SEM-EDS analysis shows that the C-S-H formed in HVFA system containing 50% or more of fly ash has a similar structure as C-S-H(I) with comparatively lower Ca/Si ratio than the one produced in PC system. Moreover, coexistence of C-S-H(I) and strätlingite is observed in the system containing 80% of fly ash, confirming that the amount of alumina and silicate phases provided by the fly ash is a major factor for the formation of C-S-H(I) and strätlingite in HVFA system.