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Introduction The use of different types of alternative fuels, wastes or secondary raw materials in the manufacture of Portland cement represents an attractive approach for energy preservation and reduction of greenhouse gases
, quick hardening or expansive binders. Calcium aluminate cements are expensive materials, especially in comparison with Portland cement. That is why, it is aimed at reduction of amount of calcium aluminate cement in composite or its partial
Abstract
In this work two aluminic pozzolans (metakaolins) and a non-pozzolan were added to two Portland cements with very different mineral composition, to determine the effect on the rate of heat release and the mechanisms involved. The main analytical techniques deployed were: conduction calorimetry, pozzolanicity and XRD. The results showed that the two metakaolins induced stimulation of the hydration reactions due to the generation of pozzolanic activity at very early stage, because of their reactive alumina, Al2O3 r− contents, mainly. Such stimulation was found to be more specific than generic for more intense C3A hydration than C3S, at least at very early on into the reaction, and more so when 7.0% SO3 was added, and for this reason, such stimulation is described as ‘indirect’ to differentiate it from the ‘direct’ variety. As a result of both stimulations, the heat of hydration released is easy to assimilate to a Synergistic Calorific Effect.
, Brasil 1986 , pp. 279 – 285 . 7 Asaga , K. , Kuga , H. , Takahashi , S. , Sakai , E. and Daimon , M. , ‘ Effect of pozzolanic additives in the Portland cement on the hydration
Abstract
Thermogravimetry (TG) and derivative thermogravimetry (DTG) have been used by the authors as very effective tools to study hydration steps of cements used for solidification/stabilization of tanning wastes. The present paper presents a method which was applied to separate the peaks shown by DTG curves of type II Portland cement pastes, analyzed at different times during the first 4 weeks of setting. Through a specific software a more detailed study of the evolution of the cement hydration may be done, which allows the measurement of the amount of hydrated water present in tobermorite gel as well as in ettringite, which are the main phases formed from the original components of the cement. The number of moles of water present in the ettringite phase calculated by the method is in very good agreement with the values found in the literature, validating the method to calculate the same parameter in tobermorite gel. In the latter case the water content decreases significantly during the first day of hydration, then remains at a constant value over the rest of the analyzed period.
Early stages hydration of high initial strength Portland cement
Part I. thermogravimetric analysis on calcined mass basis
different water/cement ratio studied pastes. Materials For this study, a high-initial strength and sulphate resistant Portland cement (HS SR PC) [ 18 ] was used, which allows reaching high strengths still at the early hydration
react to form a binding material similar to that of Portland cement in the presence of water and calcium hydroxide, Ca(OH) 2 [ 2 – 4 ]. This pozzolanic reaction with Ca(OH) 2 occurs slowly due to Ca(OH) 2 has to be first produced as a result of
at 20 °C. However, in presence of fly ash, Baert [ 8 ] already recorded this peak for cement containing merely 7.5% C 3 A. When ordinary Portland cement (OPC) is partially replaced by blast-furnace slag (BFS), the reaction of BFS is activated
Summary Due to growing environmental concerns and the need to use less energy-intensive building products, alternatives and improvements to Portland cement (PC) are being actively researched worldwide. Use of supplementary materials is now a common practice where PC is the predominant component of inorganic building products. This study aims to investigate the potential of magnesia (MgO), derived from a naturally occurring raw material magnesite, as a supplementary material. Results from mortar samples prepared with 10 and 20% replacements of ordinary Portland cement (OPC) by MgO are presented. DTA-TG was used to study and characterise the hydration behaviour of MgO in OPC environment after 3, 7, 14, 28, 56 and 90 days of moist curing. Microstructural and compressive strength determinations providing additional information on the influence of hydrated phases are also reported.
delay [ 2 , 5 – 10 ]. Hardening of Portland cement paste is based on the hydration of mineralogical constituents of cement (C 3 S, C 2 S, C 3 A and C 4 AF, where C = CaO, S = SiO 2 , A = Al 2 O 3 and F = Fe 2 O 3 ). The main contribution to the
