Funcionamiento de la pistola de perno cutivo

PHOTOMICROGRAPHS OF ARTIFACTS

Photograph 8-1 Grinding pits remaining on hastily polished surface of clinker appear somewhat like dark alkali sulfate. (S#A6717)

Polished section No etch

Field dimensions = 0.21x0.21 mm

Photograph 8-2 Exudation of polishing vehicle (propylene glycol) or cleaning medium (isopropyl alcohol) from an alite cleavage on polished section surface. The exudation could be misinterpreted as chemical attack of the alite crystal. (S#A6718) No etch

Field dimensions = 0.21x0.21 mm

Photograph 8-3 Etch halo around free lime nest observed after NH₄Cl etch (“H” in text, Chapter 3). The halo may be the result of etch interference by liquid exuding from the porous free lime crystals and nearby pores. (S#A6719)

Polished section

PHOTOMICROGRAPHS OF ARTIFACTS (CONTINUED)

Photograph 8-4 Residual liquid and halo (arrow) from polishing, cleaning, or etching, extending across alite into blue belite nest. (S#A6720)

Polished section Nital etch

Field dimensions = 0.21x0.21 mm

Photograph 8-5 Residual liquid from polishing or cleaning sample and halo of unetched belite surrounding central pore. Liquid could be

misinterpreted as free lime. Liquid eventually dried. (S#A6721)

Polished section Nital etch

Field dimensions = 0.21x0.21 mm

Photograph 8-6 Nonuniform nital etch on polished section. Cross-cutting stripes and patches in silicates could be misinterpreted as structural variations or aluminate concentrations. (S#A6722)

PHOTOMICROGRAPHS OF ARTIFACTS (CONTINUED)

Photograph 8-7 Polished section showing polishing marks, probably shallow scratches, extending across three blue alite crystals. (S#A6723)

Nital etch

Field dimensions = 0.21x0.21 mm

Photograph 8-8 Unidentified, presumably organic, crystals formed on unetched polished-section surface, perhaps as a result of mixing of propylene glycol, used as a polishing vehicle, and isopropyl alcohol used in cleaning. (S#A6724)

Field dimensions = 0.21x0.21 mm

Photograph 8-9 Residual polishing, cleaning, or etching liquids causing blotchy patterns (arrows) on blue alite crystals. Patterns removed after repolishing and drying before etching. Well-differentiated matrix of aluminate (C₃A) and ferrite is made clearly visible by application of nital over a previous KOH etch. (S#A6725)

Polished section

PHOTOMICROGRAPHS OF ARTIFACTS (CONTINUED)

Photograph 8-11 Residual liquid interference with

etch, producing dark blobs (arrow) on silicates. (S#A6727)

Polished section

KOH followed by nital etch Field dimensions = 0.21x0.21 mm

Photograph 8-10 Interference by residual liquid or

air bubble (arrow) on nital-etched, polished clinker surface. Note “ghost” boundary (arrow) transecting several alite crystals but not visible on the matrix. (S#A6726)

Although this publication is not designed to portray details of all the various methods and results of micro- scopical analysis, mention of some of the applications and possible pitfalls of the scanning electron micro- scope (SEM) and Electron Dispersive X-ray Analysis (EDXA) is appropriate. Most of the SEM and micro- probe studies to date have dealt with the general char- acterization of clinker phases, including their composi- tional variations. Among the articles describing use of the SEM in analysis of clinker microstructure is the work of Gouda (1979a, 1980) in which the various clinker phases are identified and described in order to interpret the manufacturing process. Other publica- tions in this field are those of Yamaguchi and Takagi (1968); Regourd and Guinier (1974); Skalny, Mander, and Meyerhoff (1975); and Grattan-Bellew, Quinn, and Sereda (1978). The latter publication emphasizes some of the possible problems in SEM analysis, including preparation techniques, surface charging, image dis- tortion, phase abundance, and other factors.

Use of the SEM and EDXA in this book has been primarily for phase identification, photography, and, in some cases, to gain specific compositional informa- tion. Much of the time spent with the SEM-EDXA has also been for the purpose of developing sample polish- ing and etching techniques to facilitate examination. A word of caution is given to workers who examine only fractured clinker surfaces with the SEM: Such surfaces may not present the observer with a representative cross section of the clinker’s many phases. Moreover, attention is too often directed to well-formed crystals projecting into clinker voids, which are ideal places to study deposition of alkali sulfates on previously formed crystal surfaces, but are poor localities for analysis of matrix-silicate relationships.

Used properly, the SEM-EDXA allows one to pre- cisely elucidate some of the microstructural and com- positional details unseen with other techniques of mi-

croscopy. Routine application of SEM-EDXA to daily production problems is not common. However, a semi- automatic SEM-EDXA system for routine production quality control may not be beyond the realm of possibil- ity and practicality. A computer-controlled method of SEM-EDXA was used by Minnis (1984) to determine the mineralogy of a sandstone thin section, the data expressed in volumetric percentages; the method also provides an approximation of phase grain size and a graphical description of grain locations.

Stutzman (1994) and Stutzman and Odler (1991) illustrated some of the profound implications in appli- cation of electron imaging in clinker and concrete analy- sis, demonstrating the details of microstructures at mag- nifications having resolutions of approximately 0.2 µm. Bonen and Diamond (1991) with image analysis comparisons of roller-milled and ball-milled cements illustrated that two major variants in cement perfor- mance are phase abundance and phase specific surface, particularly in the finer fractions. Roller mill cements differed from ball mill cements in having fewer very small particles, lower aspect ratios and shape factors, and differences in the content of particles of specific mineralogies. Alite was relatively enriched in the finest fractions of the ball-milled cement.

In a laboratory study of grinding techniques (ball mill vs. roller mill) Chen and Odler (1992) showed that roller mill cements exhibit inferior quality because of higher water demand, resulting from adverse packing characteristics developed during grinding. Microscopi- cally, clear cut differences were observed with regard to particle size, shape, Blaine, and additionally, dry bulk density and flow rates.

Sarkar and Samet (1994), utilizing x-ray diffraction and light and electron microscopy, concluded that an abundance of a potassium-calcium sulfate (from exces- sive insufflation) and unusually large belite crystals (from long residence times) were responsible for low