Showing papers in "Reviews in Mineralogy & Geochemistry in 2012"

Supplementary Cementitious Materials

Abstract: The current widespread use of calcium silicate or aluminate hydrate binder systems in the construction industry finds its roots in the Antique world where mixtures of calcined lime and finely ground reactive (alumino-)silicate materials were pioneered and developed as competent inorganic binders. Architectural remains of the Minoan civilization (2000-1500 BC) on Crete have shown evidence of the combined use of slaked lime and additions of finely ground potsherds to produce stronger and more durable lime mortars suitable for water-proof renderings in baths, cisterns and aqueducts (Spence and Cook 1983). It is not clear when and where mortar technology evolved to incorporate volcanic pumice and ashes as a functional supplement. A plausible site would be the Akrotiri settlement at Santorin (Greece), where archeological indications of strong ties with the Minoan culture were found and large quantities of suitable highly siliceous volcanic ash were present. This so-called Santorin earth has been used as a pozzolan in the Eastern Mediterranean until recently (Kitsopoulos and Dunham 1996). Evidence of the deliberate use of this and other volcanic materials by the ancient Greeks dates back to at least 500-400 BC, as uncovered at the ancient city of Kamiros, Rhodes (Efstathiadis 1978; Idorn 1997). In the subsequent centuries the technological knowledge was spread to the mainland (Papayianni and Stefanidou 2007) and was eventually adopted and improved by the Romans (Mehta 1987). The Roman alternatives for Santorin earth were volcanic pumices or tuff found in neighboring territories, the most famous ones found in Pozzuoli (Naples), hence the name pozzolan, and in Segni (Latium). Preference was given to natural pozzolan sources, but crushed ceramic waste was frequently used when natural deposits were not locally available. The exceptional lifetime and preservation condition of some of the most famous Roman buildings such as the Pantheon or the Pont du …

Rietveld Quantitative Phase Analysis of OPC Clinkers, Cements and Hydration Products

Abstract: It has been more than twenty years since the excellent volume of Reviews in Mineralogy dedicated to Modern Powder Diffraction was published (Bish and Post 1989). That volume contained a series of key articles ranging from the basic of powder diffraction to sample preparation and synchrotron and neutron powder diffraction. Within that volume, quantitative phase analysis was extensively discussed in a specific chapter (Snyder and Bish 1989). Snyder and Bish (1989) discussed the Reference Intensity Ratio approach (also known as Chung method), the method of standard additions (also known as spiking method) and the full pattern-fitting approach using both the Rietveld method and the observed patterns method. The reader is referred to that volume for the basics of powder diffraction, and to the specific chapter by Snyder and Bish (1989) for the history of quantitative phase analysis from powder diffraction and for a discussion or the early findings. Quantitative phase analysis by X-ray powder diffraction dates back to 1925 (Navias 1925). In this work, the amount of mullite obtained by firing selected clays (and a feldspar) was determined by the direct comparison of the intensities of two diffraction lines of the fired samples with those of pure mullite. The patterns were recorded on photographic negatives after an X-ray exposure of 165 hours (almost a week). Quantitative phase analysis (QPA) from diffraction data can be obtained from a number of methods explained in classical books (Klug and Alexander 1974; Cullity 1978; Snyder and Bish 1989; Zevin and Kimmel 1995; Jenkins and Snyder 1996). However, it is now safe to say that QPA from powder diffraction data is nowadays mainly based on the Rietveld methodology (Rietveld 1969; Hill and Howard 1987; Bish and Howard 1988; Bish and Post 1993; Madsen and Scarlett 2008). Hence, …

Calcium Aluminate Cements - Raw Materials, Differences, Hydration and Properties

Abstract: High alumina cement was used widely in the UK after World War I, expressing its higher content of aluminum oxide in comparison to Portland cement. Several descriptions of investigations on calcium aluminate cements appeared, starting around 1850, with a first patent field in 1888 (Scrivener and Capmas, in Hewlett 1998). More widely known is the work of Bied (1909, 1926) filing a patent in 1909 for the fabrication of cement using bauxite or some similar aluminum or iron-rich material, with low SiO2-contents and limestone. In 1918, the trade name Ciment Lafarge Fondue was used for the first time. Meanwhile in the USA, Spackman (1908, 1910a,b) developed cementitious material marketed under the name of Alca natural cements. Several patents were applied and granted (Bates 1921). A description of non-Portland cements was given by Muzhen et al. (1992). The reason for looking into alternative cement materials was to develop cements with improved stability against sulfate corrosion. Nowadays, calcium aluminate cements are used specifically for their distinct properties (Brown and Cassel 1977), some of which are presented in Table 1. Calcium aluminate cements do have special applications and are therefore widely used despite the fact that worldwide fabrication is by no means comparable to OPCs (Hohl et al. 1936; Garces et al. 1997; George 1976, 1980a,b, 1983, 1990, 1997; George and Montgomery 1992; George and Racher 1996; Gartner et al. 2002). Scrivener and Taylor (1990) and Scrivener et al. (1997a,b) described calcium aluminate cements and their use and microstructural developments. The use for experimental purposes was described by Auer et al. (1995). Thermal analyses for thermogravimetry of CAC-fraction and formation was discussed by Chudak et al. (1982, 1987). The …

Deleterious Reactions of Aggregate With Alkalis in Concrete

Abstract: ### Concrete in the built environment The word “concrete ” is derived from the Latin concretus (compact, condensed), representing a conjunction of con (together) and the past participle of cresco (to grow; compare: crescendo ). Thus, concrete could be liberally translated as ‘grown solid together,’ alluding to the consolidation of a particulate aggregate material with a cement binder of some sort. Concrete containing aggregate has been used in construction by the ancient Greek and Romans, possibly as a further development of clay initially used by the Assyrians and Babylonians as a binder, later superseded by burnt lime and gypsum by the Egyptians. As a construction material, concrete allows architects and engineers to design a structure with only minimal constraints to its form. A complicated shape requiring great effort to chisel out from a piece of stone can simply be poured in a mold and reproduced as often as desired, also ex situ . Both the invention of Ordinary Portland Cement (OPC), first patented by British bricklayer Joseph Aspdin in 1824, and of reinforced concrete first patented by Parisian gardener Joseph Monier in 1867 (for making durable flower pots), contributed to the development of mechanically stronger concrete allowing yet slimmer and taller structures to be built. Today, concrete is the most popular building and construction material with an annual production volume exceeding 7.5 km3, or about 20 billion tonne. Concrete is the prime ingredient in the world’s largest and most prominent structures and landmark edifices, including hydropower dams (e.g., Three Gorges Dam, Yichang/CN; also see Charlwood and Solymar 1995), coastal defense works (e.g., Delta Works/NL), telecommunication (e.g., CN Tower, Toronto/CA), office skyscrapers (e.g., Burj Khalifa, Dubai/UAE), theatres (e.g., Opera House, Sydney/AU), hotels and casinos (e.g., Marina Bay Area, Singapore/SG), nuclear power plants, oil and gas drilling and productions rigs (e.g., Sakhalin/RU), sea ports and harbors (e.g., …

Microscopy of Clinker and Hydraulic Cements

Abstract: Microscopy has played an essential part in developing our knowledge of Portland cement clinker phase composition, and is routinely used to monitor kiln operating conditions to insure cement quality. Our developing understanding of the phase composition of clinker coincides with the early days of the polarized light microscope where the then-new instrument was used to resolve conflicting theories on the phase constituents of cement clinker, essentially a man-made rock formed through sintering a ground, blended mixture of limestone, clay, and iron oxides. The phase abundance, distribution and texture of cement clinker reflect the combination of proportioning, grinding, and homogenization of the raw materials, and the firing and cooling history of the clinkering process. The ability to visualize, record and quantify phase compositional and textural attributes of the clinker allowed cement chemists a view into this process, to develop a better understanding on clinker production, and to be able to identify problems in the preparation and firing of the raw materials for improved production of the clinker. Today, most microscopy uses polished sections of clinker and reflected light, and quantitative methods include the point-count analysis, as well as image processing and analysis. The development of certified clinker reference materials have facilitated the development of the first standard test methods for clinker microscopy and X-ray powder diffraction. The application of the scanning electron microscope (SEM) allows analysis of the fine-grained, multi-phase particles of hydraulic cements and pozzolans, expanded our view into their mineralogical and textural characterization. Modeling the hydration process has developed to the point where selected properties of cement performance may be predicted from a well-characterized cement through microscopy. Cement phase mineralogy and textural characteristics, captured through SEM imaging, and particle shape characteristics quantified through X-ray tomography has allowed the generation of 3D virtual cement particles that retain the phase and textural attributes, providing realistic inputs to cement hydration models.

Alternative Low-CO2 “Green” Clinkering Processes

Abstract: The world’s Portland cement production is the third largest emitter of anthropogenic CO2 after heating/cooling of houses and transport. If no measures are taken, 1 tonne of CO2 is emitted per tonne of clinker produced, where 60% comes from the raw meal (i.e., decomposition of limestone) and 40% from the fuel (most commonly coal). Limestone is the dominating calcium oxide source of Portland cement clinker consisting of about 60% CaO, and hence the cement plants are located near a limestone deposit as limestone constitutes about 80% of the raw meal fed to the rotating kiln for clinker production. In many areas, good limestone sources are close to depletion for several reasons (e.g., MgO should be < 5% in cement clinker), and the objective of this MSA short course contribution was to see if there are other Ca-bearing natural minerals available that can replace limestone, in particular non-carbonaceous minerals that also will lead to a reduction in CO2 emissions. The conclusion is that there is no material as widespread and abundant as limestone that can replace it on a global basis. However, there are some minerals in large deposits locally that may be utilized when new cement plants are to be localized. The most promising being wollastonite (CaSiO3) that also often occur together with limestone. The second being larnite (Ca2SiO4), but it only occurs in few places. Another mineral, anorthite (CaAl2Si2O8), is too high in alumina to play a significant role in Portland cement clinkering, and is also not of interest in calcium aluminate and calcium sulfoaluminate cements due to too high silica content. As a curiosity, gypsum may replace limestone in Portland cement clinkering, but then sulfur dioxide (SO2) is released rather than CO2, which in turn may be used for production of sulfuric acid. However, the demand of sulfuric acid is much less than the demand of Portland cement on a world basis, so this route is not viable and sulfuric acid can be obtained much cheaper from other routes (e.g., roasting sulfide ore).

Industrial X-ray Diffraction Analysis of Building Materials

Abstract: X-ray analysis of polycrystalline powder samples has grown beyond its roots in the world of laboratory research and is regarded as one of the most powerful industrial process-control tools in the field of building materials and minerals. This is the key to characterize the element and the phase composition of the material. This is largely due to the development of industrial X-ray analytical systems, which have transformed these advanced analytical techniques born in the laboratory into a robust, workmanlike and easy-to-use tool for today’s heavy industries. X-ray diffraction (phase analysis) opens enormous possibilities for process and quality control. Moreover, the recent development of ultra-high-speed X-ray detectors allows for “on the fly” quantitative X-ray diffraction analysis and truly interactive process control. Hydration of cements can be studied relative ease. Additionally Computed X-ray Tomography (CT) can yield valuable information in the study of mortars and concrete.