Cementitious systems hydration

Cement hydration and epoxy polymerization occur simultaneously to form a structure that is similar to the latex-modified cementitious system. Epoxy systems develop high strength, adhesion and have low permeability, good water resistance and chemical resistance. A major advantage of this system is that it can be cured under moist or wet conditions. According to a recent study, the epoxy-modified mortars can be made without the hardeners with superior properties to those obtained with conventional epoxy mortars [89, 90]. 

Onysko SJ, Kleinmann RLP, Erickson PM (1984) Ferrous iron oxidation by Thiobacillus ferroxo-dans inhibition with benzoic acid, sorbic acid, and sodium lauryl sulfate with benzoic acid, sorbic acid, and sodium lauryl sulfate. Appl Environ Microbiol 48 229-231 Osterloh F, Saak W, PoU S, Kroeckel M, Meier C, Trautwein AX (1998) Synthesis and characterization of neutral hexanuclear iron sulfur clusters containing stair-like [Fe6(u3-S)4(u2-SR)4] and nest-like [Fe6(u3-S)2(u2-S)2(u4-S)(u2-SR)4]. Inorg Chem 37 3581-3587 Palamo A, Femaddez-Jimenez A, Kovalchuk G, Ordonez LM, Naranjo MC (2007) Opc-fly ash cementitious systems study of gel binder produced during alkaline hydration. J Mater Sci 42 2958-2966... 

Upon heating, hardened cement pastes undergo chemical reactions (for example, thermal decomposition of the hydrates present and a loss of chemically bound water). These processes may be associated with a decline or even a complete loss of strength, but in some cementitious systems an increase of strength may also be observed. 

In conclusion, the resistance of aluminous cement based concrete to most chemical corrosive agents is outstanding, provided that the mix is produced with a sufficient cement content and with a low water/cement ratio, and is properly compacted and cured. Like other hydrated cementitious systems, hardened calcium alununate cement pastes decompose and undergo chemical reactions upon heating ... 

Applications. Conduction calorimetry has been widely used for a study ofthe hydration reactions ofvarious cementitious systems. Tricalcium silicate, being the dominant compound in portland cement, determines to a large extent the strength and other properties of concrete. Conduction calorimetric curves of tricalcium silicate and portland cement show five steps during the hydration process (Fig. In the first stage, as soon as... 

Calcium chloride also has an effect on the hydration of various other cementitious systems such as pozzolanic cements, slag cements, expansive cements, high alumina cement, g q)sum, rapid hardening cement, etc. (See, for example. Refs. 1 and 40.)... 

Microhardness has been correlated with compressive strength for several cementitious systems.Figure 13 is a plot of microhardness versus porosity forthe following cement systems hydrated Reg Set cement paste with 0,1,2, and 5% CaCl2 and hydrated portland cement paste. The... 

It is very important to mention that the deformation capabihty of a given cementitious system also depends to a large extent on the degree of hydration of the cement. Consequently, the flexibility of different adhesives can only be compared at identical... 

Figure 2.17 Calorimetric curves of portland cement-slag blends (60 40 by mass) calibrated with SEM-IA. The left y axis shows the contribution of the slag to the heat of hydration the right y axis, the hydration degree of the slag as determined by SEM-IA. The values after 28 days were used for calibration. (Adapted from Kocaba, V., Development and evaluation of methods to follow microstructural development of cementitious systems including slags , PhD Thesis no. 4523, cole Polytechnique Federale de Lausanne, Switzerland, 2009.)...

Evju, C. (2003). Initial hydration of cementitious systems using a simple isothermal calorimeter and dynamic correction . Journal of Thermal Analysis and Calorimetry 71(3) 829-840. 

Mitchell, L. D., J. C. Margeson and P. S. Whitfield (2006). Quantitative Rietveld Analysis of Hydrated Cementitious Systems . Powder Diffraction 21 (2) 111-113. 

The present chapter outlines the main factors influencing TGA. The TGA signals of the most common minerals observed in cementitious systems are compared to each other and compiled as a reference database for phase identification. The quantification of bound water, portlandite and calcium carbonate and different hydrates is described in detail. Special attention is given to the methods of stopping hydration and their effect on TGA measurements and a step-by-step guideline for analysis of hydrated cements is given. 

In cementitious systems, TGA (or also DSC or DTA) is generally used to identify hydration phases, to confirm the presence of both crystalline and amorphous phases found by XRD, nuclear magnetic resonance (NMR) or scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) analysis and/or to quantify the amount of solids present. The discussion presented in this chapter will mainly focus on TGA only Section... 

Tommaseo, C. E. Kersten, M. 2002. Aqueous solubility diagrams for cementitious waste stabilization systems. 4. Mechanism of zinc immobilization by calcium silicate hydrate. Environmental Science and Technology, 36, 2919-2925. 

Just like the hydration of the cementitious component, the reaction of the ejq)ansive component with water is accompanied by a chemical shrinkage. Thus the resultant external expansion of the paste, which accompanies the hydration of an expansive cement, cannot be explained by an increase of the volume of the reactants formed in this chemical process. It is obvious that an expansion of the system would not take place if the hydration occurred in a simple through-solution reaction, in which the anhydrous starting component was readily dissolved and the hydration product precipitated randomly from the liquid phase. To produce an expansion a particular reaction mechanism seems to be required. Several hypothesis have been put forward to ejqrlain the expansion process ... 

Stable microcracking is not harmful to the cementitious material in the same drastic way as is the formation of discrete, visible cracks (cracks with widths from 5 ym and upwards). The stable microcracks just make the hep phase of the cementitious material slightly more porous and reduce its tensile strength and elastic modulus to some degree, but this cracking system is so fine that it will quite often heal again after some time by further hydration of the cement. 

This chapter describes the basic features and common practise of solid-state NMR in studies of portland cement systems and illustrates how this tool can be used to derive structural and quantitative information about cement components and cement hydration for both pure portland cement and Portland cements, including admixtures or supplementary cementitious materials (SCMs). Particular emphasis is given on the NMR techniques generally used in solid-state NMR studies of portland cement systems. However, a comprehensive overview of the NMR studies that have been performed so far or of the new chemical and physical knowledge derived from these studies will not be given. 

Several binary blends of cement with a supplementary cementitious material (SCM) are shown in Figure 8.22. All were hydrated at 20°C, with a water/binder of 0.4. In these systems IPcement refers to the inner product... 

The porosity of hydrated cementitious materials varies with many factors, such as cement fineness, w/c, mixing procedure and curing conditions. The present section aims to show typical MIP results for different cement-based materials. Contrary to the previous sections, measurement parameters are kept constant (contact angle 0 = 140°, step mode of pressurisation, constant pressurisation rate, 1 g sample mass) and only the MIP response to different materials is discussed/shown. This section aims to show general trends of MIP results across different sample systems. 

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