Sampling of clinker

Ono s method of cement kiln evaluation is based on observations of clinker or cement powder mounted in a liquid medium on a glass microscope slide. A polar ized-light microscope (the so called petrographic microscope) is an absolute necessity, and magniflca tions at approximately 400X are recommended. To determine the parameters of the kiln conditions in Ono s method as described in 1995, cement or clinker powder is sieved through a 100 pm screen (approxl mately U.S. Sieve No. 140), and a powder mount is prepared with a liquid of refractive index in the range of 1.705 to 1.715. The principal value of Ono s tech nique is that it can be employed by a competent, well trained microscopist on a small sample of clinker... 

Standard" samples of clinker, cement, and raw materials, studied microscopically, with the results of chemical analysis and x-ray diffraction, form the data base for subsequent comparisons. Study of acetic-acid residues is strongly recommended. "Half-sections" can replace thin sections, thus saving much time. 

Determination of free lime The determination of the uncombined CaO can be tackled in one of two ways. Historically this has been done using an acid-base titration after reaction of a weighed sample of clinker with ethylene glycol. The method is rapid and reliable and is still in common use. It is published in BS 4550 Part II. 

Bensted (B38) described the use of TG in the study of clinkers or unhydrated cements. At 4°Cmin in Nj with cements, losses normally occur at I00-200"C from gypsum or hemihydrate, 400-500°C from CH and 500-800°C from CaCOj. If a normal, open sample cup is used, the losses from conversion of gypsum to hemihydrate and from dehydration of hemihydrate are poorly resolved, making interpretation difficult. Better separation can be achieved by using a sample cup with a top that is closed except for a narrow exit (S32). 

The experimental considerations applying to calcium silicate pastes (Sections 5.1 and 5.2) are equally relevant to cement pastes. Of the methods so far used in attempts to determine the degrees of reaction of the individual clinker phases as a function of time, QXDA (C39,D12,T34,P28) has proved much the most satisfactory. Procedures are essentially as for the analysis of a clinker or unreacted cement (Section 4.3.2), but it is necessary to take account of overlaps with peaks from the hydration products, and especially, with the C-S-H band at 0.27-0.31 nm. The water content of the sample must be known, so that the results can be referred to the weight of anhydrous material. If a sample of the unhydrated cement is available, and its quantitative phase composition has been determined, it may be used as the reference standard for the individual clinker phases in the paste. 

When comparing the influence of the polymers, the most apparent result is the incomplete consumption of clinker phases in the c/PVAc samples, whereas in the c/PVA samples, the clinker phases are consumed in less then four days. It should be noted that the consumption of the clinker phases is the lowest for c/PVAc in pure water. The reason for this is the above mentioned hydrophobic nature of PVAc, which requires alkaline pH values for saponification before the polymer can be dissolved. Thus, the XRD measurements are consistent with the NMR measurements. Additionally, approx. 10% more amorphous material is formed in the case of c/PVAc. This is again a result of the hydrophobic nature of PVAc. As discussed in the NMR section, c/PVAc swells at a lower rate than c/PVA. This limits the access of water to the clinker phases, which hampers the formation of larger crystallite sizes. 

Wachtler and Jannsen [90] studied the material phase composition in the kiln with partial precalcinahon, and without its shut down. In the material from cyclone preheater spurrite, C2F and aluminates CA and and free CaO were found. In the samples also these phases and additionally C AF were present Then the gehlenite appears, C2S and C3A. Appearing of CjA is accompanied with the disappearing of C2F and CA. When C3S appears the samples have already the composition of clinker. 

One of the most popular methods involves crushing a random clinker sample of roughly a liter volume (1 to 2 kg) to approximately 2- to 4-mm-diameter par-... 

One problem with the crushing of clinker prior to examination is that microcracks seen in polished-section or thin section study are ambiguously interpreted. Microcracks that are not artifacts of sample preparation may, in some investigations, be related to strain caused by thermal stress (Hornain and Regourd, 1980), crystal reorganization, hydration, and expansion. 

The photographs in this section are illustrations of clinkers examined and interpreted by this writer, with emphasis on the use of Ono s interpretive table (Table 6-1). It is important to note that individual photographs may not depict all the microscopic features normally associated with the stated interpretation of kiln conditions, the interpretation having been drawn from the results of several techniques of examination and study of several clinkers in the sample. Designations such as 42.8 MPa in the photomicrograph captions indicate reported 28-day mortar-cube strength. 

Centurione and Kihara (1994) tested the application of F.L. Smidth s burnability equations and methods, including those of Fundal (1979), Theisen (1992), and Miller (1980), in an analysis of 12 samples of raw feed and corresponding clinkers. Cenfurione and Kihara used an hydrochloric acid digestion mefhod fo calculate Cj25 and concluded that coarse quartz (>45 pm) and limestone (>125 pm) should not exceed 2% and 6%, respectively, by weight of sample. 

Alternatively, the writer has found fhaf small portions of plastic fluorescent-light diffuser panels, containing multiple square chambers, can also be used for sample holders. The panel can be cut with a hacksaw into "2-hole," "3-hole," or "4-hole" containers, the latter arrangement particularly useful for studying the raw feed—the >125-pm fraction, the >45-pm insoluble residue from acetic acid and that from hydrochloric acid, and the feed as received, all in the same thin section. Small fragments of clinkers may also be encap-... 

If a clinker sample is to be subjected to the extraction, a random sample of 1- to 2-mm crushed clinker particles, taken from the same fraction as previously prepared for polished section examination, is further crushed in a mortar and pestle until all the subsample passes a 75- j,m screen (No. 200 mesh). If acement is to be treated, a random sample of approximately 10 grams is sieved to produce the 45- to 75-pm fraction (325 to 200 mesh) particles left on the 75- j,m screen could be further crushed to pass the screen or, perhaps, studied microscopically to determine belite nest percentage. Sieving, however, is an optional step the main benefit is that it provides a uniformly sized powder promoting a relatively uniform level of focus by removing "boulders" that may interfere with examination and particle manipulation. If sieve confaminafion is a likely problem, one can use disposable nylon with the proper mesh opening. 

The sample is made from 5 kg of clinker, crushed in a jaw crusher with a gap of 2 mm and screened on a 150-pm sieve. The fraction larger than 150... 

Chromy (1983), utilizing a 2000-point coimt on 22-mm diameter polished sections of a sieved crushed clinker sample, demonstrated the usefulness of the microscope in determining the mineralogical composition of clinker, the data from which were related mathematically to clinker and raw mix composition, and cement strength. He concluded, "If conversion constants linking the equilibrium clinker composition and strength are determined, it is not necessary to carry out the quantitative phase analyses of the clinker produced. Monitoring the free lime content will suffice."... 

Campbell, D.H., "Microscopical Description of Clinker Sample No. 44ICMA Sample Exchange Program," Proceedings of the 16th International Conference on Cement Microscopy, International Cement Microscopy Association, Richmond, Virginia, 1994a, pp. 377-380. 

Most of the photomicrographs were taken by the writer as part of a PCA research project (HR-1404, Microscopical Analysis of Clinker) in which samples of raw feed, clinker, and cement from approximately 51 North American kilns were studied and interpreted. 

The effectiveness of different forms of sulfate (at eqtral SO concentrations) and the susceptibihty of irrdividttal clinker phases and their blerrds to this ion are apparent from Table 20.1, which indicates the time it took to attain an expansion of the studied samples of 5 rtrm/m. 

The critical evaluation of the results in Table 9 leads to the following conclusion it seems that the mechanical behaviour of the cements formed improves when more red gypsum is added to the cements, thereby approaching the resistance values of the commercial cement. In faet, in the YC sample (10 % red gypsum) the mechanical resistance values are similar to those for the commercial cement. This is important, as it supports the use of red gypsum as an additive in the formation of cements and because it is possible to reduce the amount of clinker used, with all the economic benefits that tliis entails (cost savings). In this sense, it is necessary to remember that the commercial cement taken as reference in our study is approximately 97% clinker and 3 % natural gypsum. 

Samples of raw meal, clinker, dust, fuel and smoke gas ont of the kiln should be taken for analysis pnrposes. 

The residence time distributions were measured by pulse injection of a sample of calcined extrudates labelled with technetium-99m. The movement of the injected sample was followed with one scintillation detector in the solids feed line and three around the chute at the solids discharge end of the kiln (Fig. 1). The amount of injected radio-active material was too small for its passage through the kiln to be followed with detectors along the outside wall of the kiln, as has been done for measurement of the solids transport in rotary kilns used for production of clinker [26,27]. 

Figure 2.18 shows an example of the use of calorimetry to measure the activity of a biomass fly ash in water without portland cement at 20°C. This approach is sometimes useful to isolate the comparably low fly ash heat of hydration. Figure 2.19 shows a similar example where three different samples of high-calcium fly ash are hydrating in a simulated portland cement environment including 50% calcium hydroxide with 0.5 M NaOH at w/c of 1.0, thus using heat of fly ash hydration as a test method for fly ash activity in a well-defined chemical environment, excluding interference from Portland cement clinker. 

When the kiln material is cooled it forms into crystallized clinkers. These are rather large irregular pieces of the solidified cement material. These clinkers are ground and a small amount of gypsum is added (usually about 1.5 to 3%). The gypsum prevents flash setting of the cement and also controls free CaO. This final cement product is sampled, analyzed and stored. The actual commercial cement is usually a hlend of several different cements. This blending ensures a consistent product. 

Aliphatic solvents, alkyllithium compounds and, 14 250-251 Aliphatic sulfonates, 26 145 Aliquot samples, 13 413-415 analysis of, 13 416 Aliskren, 5 158 Alitame, 12 42 24 232 Alite, phase in Portland cement clinker, 5 471, 472t, 473t Alitretinoin, 25 790 Alizarin, color of, 7 331 Alizarin derivatives, 9 337 Alizarin pure Blue B, 4 361t Alkadienes, metathesis of, 26 923 Alkali/alkaline-earth cation recognition,... 

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