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Cement
About: Cement is a research topic. Over the lifetime, 68440 publications have been published within this topic receiving 829356 citations.
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TL;DR: In this paper, a model for the formation of pozzolanic reaction products and the development of the pore structure is presented, and a critical examination of the "incubation period" is given.
346 citations
TL;DR: In this article, the interaction between limestone powder and fly ash in ternary composite cement is investigated, and the synergistic effect of fly ash and limestone powder is confirmed and it translates to improved mechanical properties that persist over time.
Abstract: The interaction between limestone powder and fly ash in ternary composite cement is investigated. Limestone powder interacts with the AFm and AFt hydration phases, leading to the formation of carboaluminates at the expense of monosulphate and thereby stabilizing the ettringite. The effect of limestone powder on OPC may be restricted due to the limited amount of aluminate hydrates formed by the hydration of OPC. The additional aluminates brought into the system by fly ash during its pozzolanic reaction amplify the mentioned effect of limestone powder. This synergistic effect between limestone powder and fly ash in ternary cements is confirmed in this study and it translates to improved mechanical properties that persist over time.
345 citations
TL;DR: In this article, the authors evaluated the properties of concrete made with crushed bricks replacing natural aggregates and found that the results indicated that ceramic residuals could be used as partial replacement of natural aggregate without reduction of concrete properties for 15% replacement and with reductions up to 20% for 30% replacement.
344 citations
TL;DR: Both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the setting reaction proceeded were responsible for the mechanical behavior of the cement.
Abstract: The combination of self-setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the setting and hardening mechanisms of a cement-type reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were alpha-tricalcium phosphate containing 17 wt% beta-tricalcium phosphate, and 2 wt% of precipitated hydroxyapatite as solid phase and an aqueous solution 2.5 wt% of disodium hydrogen phosphate as liquid phase. The transformation of the mixture was stopped at selected times by a freeze-drying techniques, so that the cement properties at various stages could be studied by means of x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Also, the compressive strength of the cement was measured as a function of time. The results showed that: (1) the cement setting was the result of the alpha-tricalcium phosphate hydrolysis, giving as a product calcium-deficient hydroxyapatite, while beta-tricalcium phosphate did not participate in the reaction; (2) the extent of conversion of alpha-TCP was nearly 80% after 24 hr; (3) both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the setting reaction proceeded were responsible for the mechanical behavior of the cement; and (4) the microstructure of the set cement consisted of clusters of big plates with radial or parallel orientations in a matrix of small plate-like crystals.
343 citations