1.0 TitlePhase determination of unhydrated cement using X-ray diffraction.

2.0 Abstract/*Coming soon*/

3.0 IntroductionX-ray diffraction (XRD) is used to determine the crystalline structure and lattice parameter of materials. Using this information, it is possible to identify the material being analysed. This is due to the fact that each metallic element in the periodic table has a unique combination of lattice structure and parameter at room temperature (Citation needed).There are 2 principle means of generating x-rays. The first is by firing electrons at a target metal which will displace inner shell electrons of the metal. As the outer shell electrons replace the lost electrons, energy is released in the form of x-rays. The second method is by accelerating electrons using a synchrotron. As the electrons approach the speed of light, they emit electromagnetic radiation as x-rays (Moore & Reynolds, 1997).If a crystal substance is bombarded by x-rays of a certain wavelength, and at a certain angle, , then the interaction between the incident x-rays and the electron density around the atoms produces diffracted beams which yield diffraction patterns as shown in Figure 3.1 (Mitchell, 2004).

Figure 3.1. Illustration of incident radiation diffraction by a crystal lattice (Mitchell & Perez-Ramirez, n.d.).

The path difference of x-rays reflected from adjacent planes is 2d(sin ) and the constructive interference occurs when the path difference is an integer, n of the wavelength. The resulting Equation (3.1) is known as Braggs Law and states that bombarding a crystal lattice with x-rays of a known wavelength and at a known angle will produce diffracted x-rays of varying intensities that represent a specific interplanar spacing in the lattice (Bragg & Bragg, 1913).

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Harrington (1927), Hansen (1928) and Bronmiller & Bogue (1930) were among the pioneers of x-ray diffraction measurements of major cement phases. Ordinary Portland cement (OPC) contains four main phases known as alite (C3S), belite (C3S), aluminate (C3A) and aluminoferrite (C4AF). The crystallochemical characteristics of these major phases are summarized in Table 3.1. In addition, OPC may also contain free lime (CaO), periclase (MgO) and alkali sulfates.Table 3.1. Salient crystallochemical characteristics of cements major phases (Chatterjee, 2006).Name and compositionProportion in clinkerForeign elements generally presentApprox. impurity levelCrystallographic modifications known

Alite, C3S50-70%Al, Fe, Mg, Cr, Ti, S, P, Ba, Mn, Na, K4%3 triclinic + 3 monoclinic + 1 rhombohedral polymorphs in temperature range 620-1070C

Belite, C2S15-30%Al, Fe, Mg, Cr, Ti, S, P, Ba, Mn, Na, K, V6% (trigonal-hexagonal), H & L (orthorhombic), (monoclinic) and (orthorhombic) polymorphs in temperature range 500-1425C

Aluminate, C3A5-10%Fe, Mg, Ti, Na, K, Si10%No polymorphs. Foreign elements as solid solutions. Only alkalis cause change in symmetry

Aluminoferrite, C2(A,F)5-15%Mg, Cr, Ti, Mn, Si,13%C2F orthorhombic (pseudotetragonal)

A unique diffraction pattern exists for each phase of cement with the intensity of each pattern corresponding to the concentration of the phase in the mixture (Chatterjee, 2006). Therefore, it is possible to determine the composition of any given cement clinker by quantatively analysing its XRD pattern. However, due to complex and overlapping patterns, peak intensity measurement and selection of standard reference materials become an issue.Alite polymorphs most prominent in cement clinker are monoclinic and triclinic with the rhombohedral form occurring very rarely. The rhombohedral form is characterized by a singlet peak at 51.7 2.

4.0 Materials and Equipment

The material required for the experiment is ordinary Portland cement (OPC). The equipment required for the experiment include the following: XRD-6000 X-ray diffractometer Aluminium sample holder (25 mm diameter x 1 mm depth) Glass plate Oven

5.0 Method

The XRD-6000 will use copper (Cu) as the target metal to generate x-rays using a voltage of 40 kV and current of 30 mA. The wavelength, of the x-rays is 1.54056 or 1.54056 nm.

6.0 ProcedureThe cement was dried in an oven at 105C for at least 24 hours before the experiment to eliminate excess moisture. A small quantity of the cement was then placed on the aluminium sample holder. A glass plate was used to compact the cement into the sample holder to ensure that the cement will not fall out during the experiment. The sample holder containing the cement was transferred to the rotational sample stage RS-1001 inside the XRD-6000. The door of the XRD-600 was ensured to be properly closed before the machine was activated. After approximately 30 minutes, the machine outputs the results of the XRD on-screen as well as in a file to be processed by separate software.

7.0 ResultsThe results of the XRD performed on the cement sample are shown in Figure 7.1. A total of 47 peaks have been registered with the strongest 3 peaks occurring at peak number 12 (32.3193), 13 (32.6996) and 17 (34.4809) with intensities of 540, 353 and 345 counts respectively as shown in Table 7.1. Tabulated data of the 47 peaks may be found in Appendix A.

Table 7.1. Strongest 3 peaks and intensity count.Peak number2 (Degrees)Intensity (Count)

1232.3193540

1332.6996353

1734.4809345

Figure 7.1. XRD pattern of cement sample (wavelength, = 1.54056 ).

Using the data obtained from the XRD, a graph of peaks is plotted in Figure 7.2 to remove background and noise from the data so that clear comparisons may be made with other XRD profiles.

Figure 7.2. Peak positions and intensity of the XRD profile.

8.0 Discussion/*Coming soon*/

9.0 ReferencesBragg, W. H. & Bragg, W. L. (1913). The reflection of x-rays by crystals. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 88(605), 428-438.Bronmiller, L. T. & Bogue, R. H. (1930). The X-ray method applied to a study of the constitution of Portland cement. Journal of Research of the National Bureau of Standards, 3(233).Chatterjee, A. K. X-ray diffraction. In Ramachandran, V. S & Beaudoin, J. J. (Eds.), Handbook of analytical techniques in concrete science and technology (pp. 275-332). Delhi: Standard Publishers Disributors.Hansen, W. C. (1928). Further studies on Portland cement compounds by the X-ray diffraction method. Journal of the American Ceramic Society, 11(2), 68-78.Harrington, E. A. (1927). Diffraction measurements on some of the pure components concerned in the study of Portland cement. American Journal of Science, 13, 78.Mitchell, B. S. (2004). An introduction to materials engineering and science: For chemical and materials engineering. Hoboken, NJ: John Wiley & Sons.Mitchell, S. & Perez-Ramirez, J. (n.d.). X-ray diffraction [PDF document]. Retrieved January, 29, 2016 from http://cmirt.wcupa.edu/PDFs/PXRD/00-X-Ray-Diffraction-Mitchell-Catalysis.pdfMoore, D. M. & Reynolds, R. C. (1997). X-ray diffraction and the identification and analysis of clay minerals (2nd ed.). New York: Oxford University Press.

10.0 Appendices