Cement science

Heidemann D (1994) In Colombet P, Grimmer AR (eds) Application of NMR spectroscopy to cement science. Gordon and Breach Science, Reading, p 77... 

What happens when water reacts with the different components of the cement powder is a central question in cement science. In order to answer this complicated question scientists have studied the rates of reaction and heat hberation when water has been added to the different compounds separately. 

Y. Ohama, M. Ota and H. Tatematsu Properties of polymer-modified mortars using redispersible polymer powders with nitrite-type hydrocalumite (in Japanese). Cement Science and Concrete Technology No.59/2005 (2006), pp.461-468. 

DSC (Differential Scanning Calorimetry) has also been used in cement science investigations to some extent. It is based on a power compensated system. In this technique the reference and the sample imder investigation are maintained at a constant temperature throughout the heating schedule. The heat energy required to maintain the isothermal condition is recorded as a function of time or temperature. There are some similarities between DTA and DSC ineluding the appearance of thermal curves. DSC can be used to measure the heat capacities of materials. DSC measures directly the heat effects involved in a reaction. 

It is an established fact that C3S is much more reactive than C2S. The relative reactivities of Ca in various compounds of interest in cement science were studied by the extent to which they reacted with silver nitrate.DTA was used in the cooling mode to estimate the unreacted silver nitrate by an exothermal transition at about 190°C. (See Table 3.) The reaction between CaO and AgN03 is almost stoichiometric. Calcium hydroxide also reacts stoichiometrically with silver nitrate. Only 0.81 mol out of 3 mols in C3 S has reacted with silver nitrate. This suggests that about 27% of tricalcium silicate is more reactive than the rest. Isothermal conduction calorimetric curves show that about the same amount of C3S is relatively more reactive. Thus, it seems that all Ca ions are not the same in the silicate. Dicalcium silicate phase has reacted about 6 % only and this... 

The binary, ternary, and quaternary systems containing oxides of relevance to cement science have been studied at ambient temperatures or under autoclaving conditions. Various hydrated products, crystalline as well as poorly crystallized, are formed. 

H. Sango, Characteristics of Cement Clinker Compounds Made from the Raw Material Containing Zinc Oxide. Cement Science and Concrete Technology. No.59 30-37 (2005). 

The calorimetric curve upon cement hydration, which is generally continuously monitored, provides valuable kinetic information. Thus, the hydration times can be identified when further discontinuous hydration experiments, e.g. using XRD or TGA, can be carried out. There have also been interesting combinations of isothermal calorimetry and other measurement techniques published (mainly in fields other than cement science), such as the measurement of pressure, ion concentration, pH, relative humidity, rheology and chemical shrinkage (Champenois et al. 2013 Johansson and Wadso 1999 Lura et al. 2010 Minard et al. 2007 Wadso and Anderberg 2002). Recent work focused also on the calculation of heat flow curves from in situ hydration experiments done by quantitative XRD analysis (Bizzozero 2014 Hesse et al. 2011 Jansen et al. 2012a,b). 

QPA by XRD has become a prominent characterisation technique in cement science and more recently also in cement production. Properties such as strength development or durability are closely related to the cement phase composition. Early analyses were mostly based on the Bogue calculation... 

Definitely, XRD analysis will find an even broader use and acceptance in the cement science community of the future as more researchers will secure access to the equipment and the supporting data analysis software will become ever more powerful and user friendly. This will not mean, however, that the cement-inherent challenges and practical problems will disappear. On the contrary, even more attention will need to be paid to the training and guidance of novices in the field to safeguard the quality of the results and to realise the full potential of XRD. 

Thermogravimetric analysis (TGA) is a widely applied technique in the field of cement science. Measurements of bound water and portlandite content by TGA are often used to follow the reaction of portland cement or to evaluate the reactivity of supplementary cementitious materials (SCMs), such as fly ash and blast furnace slags. TGA is able to identify X-ray amorphous hydrates, such as C-S-H or AHj, and can be used complementarily to other techniques such as X-ray diffraction (XRD). 

Nevertheless, unfortunately, SEM and TEM are probably the most widely misused techniques in cement science and a very high proportion of published images provide no useful information, representing countless hours of wasted research time. In this chapter we try to provide guidelines to the effective use of electron microscopy (both SEM and TEM) and explain how these techniques can be best used to study cementitious microstructures. 

A very common use of SEM in cement science is to look at the way the microstructure evolves over time during the hydration process, which transforms a fluid paste or concrete into a rigid solid. To look at samples at different times, first one has to stop the process of hydration by removing the free water. Even for hardened samples, free water must be removed before exposing samples to the high vacuum of the microscope chamber or as a first step in the polishing process. 

The procedure to prepare a hydrated paste for cryo-observation requires several additional steps and is beyond the scope of this chapter as the method is extremely rarely used in the field of cement science. The reader is referred to the aforementioned publications (Holzer et al. 2007 Zingg et al. 2008). 

Damidot, D., B. Lothenbach, D. Herfort and F. P. Glasser (2011). Thermodynamics and cement science . Cement and Concrete Research 41(7) 679-695. 

This edited volume provides the cement science community with a state-of-the-art overview of analytical techniques used in cement chemistry to study the hydration and microstructure of cements. Each chapter focusses on a specific technique, not only describing the basic principles behind the technique, but also providing essential, practical details on its application to the study of cement hydration. Each chapter sets out present best practice, and draws attention to the limitations and potential experimental pitfalls of the technique. Databases that supply examples and that support the analysis and interpretation of the experimental results strengthen a very valuable ready reference. 

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