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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 article, a self-compacting concrete (SCC) mixture was replaced with a Class C fly ash (FA) in various proportions from 30% to 60% and the results showed that 10% silica fume (SF) added to the mixture positively affected both fresh and hardened properties of high-performance high-volume FA SCC.
325 citations
Journal Article•
TL;DR: In this article, the authors present refinements for estimating the parameters of this equation that will provide a readily recognized means of choosing the proper amount of LWA and improving mixture proportioning.
Abstract: Internal curing is the process by which the hydration of cement occurs because of the availability of additional internal water that is not part of the mixing water. An equation has been developed in a previous study for calculating how much lightweight aggregate (LWA) is needed to supply water for internal curing of any given concrete mixture. This paper presents refinements for estimating the parameters of this equation that will provide a readily recognized means of choosing the proper amount of LWA and improving mixture proportioning. The two major factors to be considered are the variation of chemical shrinkage of cement with Portland cement phase composition and curing temperature, and the relevant value for the absorption of the LWA. In order to determine the amount of LWA needed, it is recommended that the mass composition of the cement clinker be obtained from either a detailed scanning electron microscope/X-ray image analysis or the Bogue calculation. Then, the expected chemical shrinkage of the cement at 25 deg C should be calculated. If the expected average curing temperature is above 25 deg C, the calculated value should be decreased by 0.0005 per deg C above 25 deg C. If the expected average curing temperature is below 25 deg C, the calculated value should be increased by 0.0005 per deg C below 25 deg C. The desorption of the LWA from a saturated state down to a relative humidity of relevance for the internal curing of concrete should then be measured. Finally, the determined values for chemical shrinkage and absorption of LWA should be substituted in the original equation to obtain the desired mass of lightweight fine aggregate in the concrete mixture.
325 citations
TL;DR: In this article, the early hydration of alkali-activated blast furnace slag cements was studied using isothermal conduction calorimetry, and the cumulative heat of hydration increases by increasing the n modulus as well as the dosage of water glass, but is still lower than that of Portland cement.
325 citations
TL;DR: In this paper, the authors investigated the use of coal ash in concrete to replace sand with bottom ash waste and cement with fly ash and concluded that those experimental concrete mixes can be used in several structures (foundations, subbases, pavements, etc.) which will minimize the cost, energy and environmental problems to a great extent.
324 citations
TL;DR: In this article, the effectiveness of locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures.
Abstract: Natural zeolite, a type of frame-structured hydrated aluminosilicate mineral, is used abundantly as a type of natural pozzolanic material in some regions of the world. In this work, the effectiveness of a locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures. The experimental tests included three parts: In the first part, the pozzolanic reactivity of natural zeolite and silica fume were examined by a thermogravimetric method. In this case, the results indicated that natural zeolite was not as reactive as silica fume but it showed a good pozzolanic reactivity. In the second part, zeolite and silica fume were substituted for cement in different proportions in concrete mixtures, and several physical and durability tests of concrete were performed. These experimental tests included slump, compressive strength, water absorption, oxygen permeability, chloride diffusion, and electrical resistivity of concrete. Based on these results, the performance of concretes containing different contents of zeolite improved and even were comparable to or better than that of concretes prepared with silica fume replacements in some cases. Finally, a comparative study on effect of zeolite and fly ash on limiting ASR expansion of mortar was performed according to ASTM C 1260 and ASTM C 1567. Expansion tests on mortar prisms showed that zeolite is as effective as fly ash to prevent deleterious expansion due to ASR.
323 citations