Microstructure of Steam Cured Concretes Deteriorated by Alkali-Silica Reaction

1994 ◽  
Vol 370 ◽  
Author(s):  
Jean Pierre Bournazel ◽  
Micheline Moranville-Regourd
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Thermal Cycle ◽  
Linear Expansion ◽  
Local Development ◽  
Alkali Silica Reaction ◽  
Steam Curing ◽  
Deterioration Process ◽  
Scanning Electron

AbstractIn order to know the main cause of the cracking of concrete ties we tried to reproduce the deterioration process in the laboratory, using the same thermal cycle and the same materials. Model concretes were first steam cured then examined for ASR using the CSA-A-23-2-14A accelerated test. Linear expansion of concrete prisms were measured and fracture surfaces of concrete after treatment were observed under scanning electron microscope. They showed ASR gels and secondary ettringite. A simultaneous thermal mechanical computation gave the global microcracking of concrete induced by steam curing. A second computation showed the accelerating role of temperature on the local development of ASR products.

scholarly journals The Carotid Siphon: A Scanning Electron Microscope Assessment of its Embolie Potential

1985 ◽  
Vol 12 (3) ◽  
pp. 263-266 ◽  
Author(s):  
F.W. Saunders ◽  
P. Shedden
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Clinical Studies ◽  
Carotid Bifurcation ◽  
Scanning Electron Microscope Study ◽  
Embolic Material ◽  
Carotid Siphon ◽  
Morphologic Data ◽  
Scanning Electron

ABSTRACT:The role of the carotid siphon as a source of embolic material has had limited morphological or clinical study. The morphologic data available suggests that the siphon plays only a small role in embolic cerebrovascular disease. Clinical studies, however, suggest that it has a significant ischemic potential. To clarify this apparent discrepancy, we have designed a scanning electron microscope study of the carotid siphon. Eighty percent of the specimens from the carotid bifurcation and 30% of the siphon specimens showed evidence of damaged endothelium with attached red cell and platelet debris. The embolic potential of the siphon is estimated to be between ⅓ to ½ that of the carotid bifurcation. This supports the most recent clinical studies.

scholarly journals The Role of Aragonite in Producing the Microstructural Diversity of Serpulid Skeletons

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1435
Author(s):  
Olev Vinn
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Powder Diffraction ◽  
Deep Ocean ◽  
X Ray ◽  
Prismatic Structure ◽  
Wide Range ◽  
Different Types ◽  
Scanning Electron

Aragonite plays an important role in the biomineralization of serpulid polychaetes. Aragonitic structures are present in a wide range of serpulid species, but they mostly belong to one clade. Aragonitic structures are present in a wide range of marine environments, including the deep ocean. Aragonitic tube microstructures were studied using a scanning electron microscope. X-ray powder diffraction was used to identify the aragonite. Aragonite is used to build five different types of microstructures in serpulid tubes. The most common aragonitic irregularly oriented prismatic structure (AIOP) is also, evolutionarily, the most primitive. Some aragonitic microstructures, such as the spherulitic prismatic (SPHP) structure, have likely evolved from the AIOP structure. Aragonitic microstructures in serpulids are far less numerous than calcitic microstructures, and they lack the complexity of advanced calcitic microstructures. The reason why aragonitic microstructures have remained less evolvable than calcitic microstructures is currently unknown, considering their fit with the current aragonite sea conditions (Paleogene–recent).

The Role of Alum in the Fabrication of Calcium Silicate for Dissolved Acetylene Cylinders

2011 ◽  
Vol 117-119 ◽  
pp. 870-872
Author(s):  
Shi Cai Cui ◽  
Zhao Bo Meng
Keyword(s):  
Phase Composition ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Powder Diffraction ◽  
Calcium Silicate ◽  
Filling Material ◽  
X Ray ◽  
Comprehensive Performance ◽  
Scanning Electron

Calcium silicate for filling material used in dissolved acetylene cylinders was prepared by adding alum as additive. Samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The effects of alum on the bleeding, shrinkage, strength, porosity, morphology and phase composition were studied. The experimental results show that the adding of alum can improve the comprehensive performance of samples. The mechanism was discussed in detail.

Mechanism of Using Mineral Admixtures in Concrete to Suppress Alkali-Silica Reaction

2006 ◽  
Vol 302-303 ◽  
pp. 111-119
Author(s):  
Xiao Xin Feng ◽  
Nai Qian Feng
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Pore Solution ◽  
Mineral Admixtures ◽  
Alkali Silica Reaction ◽  
Alkali Concentration ◽  
Alkali Ions ◽  
Scanning Electron

The mechanism of using mineral admixtures in concrete for suppressing alkali-silica reaction has been studied through analyzing pore solution and observing the surface of aggregates in mortar bars with scanning electron microscope (SEM). The results show that when mineral admixtures are used in the concrete, not only the alkali concentration in the pore solution can be reduced, but also the diffusion of alkali ions from the outside of concrete to the inside can be prevented, and the diffusion of alkali ions from the pore solution to the surface of the aggregates can also be prevented. Thus the attack of alkalis to aggregates is reduced, and the alkali-silica reaction is suppressed.

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