Topic
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, the effect of different amounts of silica fume (SF) and water to cement ratios (w/c) on the residual compressive strength of high-strength concrete after exposure to high temperatures was investigated.
Abstract: This paper presents the results of an experimental investigation on the effect of different amounts of silica fume (SF) and water to cement ratios (w/c) on the residual compressive strength of high-strength concrete after exposure to high temperatures. Based on the results obtained the rates of strength loss for concrete specimens containing 6% and 10% SF at 600 °C were 6.7% and 14.1% lower than those of the ordinary concrete. The dosage of SF had no significant effect on the relative residual compressive strength at 100 and 200 °C, whereas the amount of SF had considerable influences on the residual compressive strength above 300 °C similar to the response at 600 °C. The optimum dosage of SF and w/c was found to be 6% and 0.35, respectively.
246 citations
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01 Jan 2007TL;DR: In this paper, the authors considered the heterogeneity of the composition of its principle components, cement, water, and a variety of aggregates, the properties of the final product can widely vary.
Abstract: Concrete can be considered as a kind of artificial rock with properties more or less similar to certain natural rocks. As it is strong, durable, and relatively cheap, concrete is, since almost two centuries, the most used construction material worldwide, which can easily be recognized as it has changed the physiognomy of rural areas. However, due to the heterogeneity of the composition of its principle components, cement, water, and a variety of aggregates, the properties of the final product can widely vary. The structural designer therefore must previously establish which properties are important for a specific application and must choose the correct composition of the concrete ingredients in order to ensure that the final product applies to the previously set standards. Concrete is typically characterized by a high-compressive strength, but unfortunately also by a rather low-tensile strength. However, through the application of steel or other material reinforcements, the latter can be compensated for as such reinforcements can take over tensile forces. Modern concrete is based on Portland cement, a hydraulic cement patented by Joseph Aspdin in the early 19th century. Already in Roman times hydraulic cements, made from burned limestone and volcanic earth, slowly replaced the widely used non-hydraulic cements, which were based on burned limestone as main ingredient. When limestone is burned (or “calcined”) at a temperature between 800 and 900◦C, a process that drives off bound carbon dioxide (CO2), lime (calcium oxide; CaO) is produced. Lime, when brought into contact with water, reacts to form portlandite (Ca(OH)2) which can further react with CO2, which in turn forms back into calcite (CaCO3), or limestone, the pre-burning starting material. However, a major drawback of this non-hydraulic cement is that it will not set under water and, moreover, its reaction products portlandite and limestone are relatively soluble, and thus will deteriorate rapidly in wet and/or acidic environments. In contrast, portland cement produces, upon reaction with water, a much harder and insoluble material that will also set under water. For portland cement production a source of calcium, silicon, aluminum, and iron is needed and therefore usually limestone, clay, some bauxite, and iron ore are burned in a kiln at temperatures up to 1, 500◦C. The cement clinker produced is mainly composed of the minerals alite (3CaO.SiO2), belite (2CaO.SiO2), aluminate (3CaO.Al2O3), and ferrite (4CaO.Al2O3.Fe2O3), which all yield specific hydration products with different characteristics upon reaction with water.
246 citations
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TL;DR: In this paper, an investigation of alkali activation of Turkish slag (AAS) was carried out using sodium silicate and sodium hydroxide activators within the scope of this study.
Abstract: Investigation of alkali activation of Turkish slag (AAS) was carried out using sodium silicate and sodium hydroxide activators within the scope of this study. The objective of the present work is to determine the SiO 2 /Na 2 O ratios ( M S ) and Na 2 O contents of the solutions on the development of workability, setting times, mechanical properties, drying shrinkage, water absorption characteristics and microstructure of alkali activated slag cement binders. Test results showed that M S and Na 2 O contents of activator solution are of great importance on the properties of AAS. Portland cement free high performance composite with compressive strength values about 100 MPa can easily be achieved by activation of slag without heat curing. Moreover, in case of activation by optimum M S ratio, sodium silicate activated AAS mortars present higher compressive strength, lower water absorption, higher workability, lower porosity and a wide range of setting times compared to NaOH activated AAS mortars and Portland cement mortar. Consequently, it can be said that this new binder is likely to have enormous potential to become an alternative to Portland cement.
246 citations
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TL;DR: In this article, the performance and long-term durability of concrete where ground glassy blast-furnace slag (granulated and pelletized) has been used as a cementitious material is discussed.
Abstract: This paper summarizes the results of studies carried out at the Building Research Establishment in the UK, on the performance and long-term durability of concrete where ground glassy blast-furnace slag (granulated and pelletized) has been used as a cementitious material. Using data from tests on site structures and laboratory and exposure site studies, comparisons are made of the properties and performances of the slag cement concretes with normal Portland cement concretes of similar mixture proportions. A number of recommendations are given for the effective use of ground glassy blast-furnace slag in concrete. The many technical benefits available to the concrete user, such as reduced heat evolution, lower permeability and higher strength at later ages, decreased chloride ion penetration, increased resistance to sulfate attack and alkali silica reaction were affirmed. However, a cautionary warning of the importance of good early curing is made to ensure that the adverse effects of higher rates of carbonation, surface scaling and frost attack are minimized. The paper is intended to provide guidance for those concerned with the design, specification, application and performance of concrete in practice where slag can also help to reduce costs and energy demands in the production of cement compared with normal Portland cement.
246 citations
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TL;DR: In this article, a 30-year old well from a natural CO2 production reservoir was investigated and the results were used as part of the CO2 Capture Project's effort to assess wellbore integrity performance in CO2 storage sites.
245 citations