1,721,767 research outputs found
The influence of chemical activators on the hydration behavior and technical properties of calcium sulfoaluminate cements blended with ground granulated blast furnace slags
No full textThe manufacture of Ordinary Portland cement (OPC) generates around 8% of the global CO2 emissions related to human activities. The last 20 years have seen considerable efforts in the research and development of methods to lower the carbon footprint associated with cement pro-duction. Specific focus has been on limiting the use of OPC and employing alternative binders, such as calcium sulfoaluminate (CSA) cements, namely special hydraulic binders obtained from non-Portland clinkers. CSA cements could be considered a valuable OPC alternative thanks to their dis-tinctive composition and technical performance and the reduced environmental impact of their manufacturing process. To additionally reduce CO2 emissions, CSA cements can also be blended with supplementary cementitious materials. This paper investigates the influence of two separately added chemical activators (NaOH or Na2CO3) on the technical properties and hydration behavior of four CSA blended cements obtained by adding to a plain CSA cement two different ground granulated blast furnace slags. Differential thermal-thermogravimetric, X-ray diffraction and mercury intrusion porosimetry analyses were done, along with shrinkage/expansion and compressive strength measurements
Fabrication and Properties of Blended Calcium Sulfoaluminate Cements Based on Thermally Treated Reservoir Sediments
No full textIn 2021, approximately 4.1 billion tonnes of cement were globally produced and the annual
CO2 emissions from cement plants reached almost 2.8 billion metric tonnes. In recent years, many
efforts have been made to manufacture low-CO2 cements. In this regard, great consideration has been
given towards calcium sulfoaluminate (CSA) binders for both their technical features and sustainable
properties, principally connected to their industrial process. The use of blended cements composed
by CSA binders and supplementary cementitious materials (SCMS) can be an effective way to (a)
reduce the CO2 footprint and (b) produce greener binders. This scientific work studied the utilization
of different amounts (15–35 wt%) of calcined reservoir sediments (RS) as SCMS in blended CSA
binders, where the binders were cured for up to 56 days and characterised by various analytical
techniques. It was found that thermally treated RS were particularly noteworthy as their utilization
allowed for a dilution of the CSA clinker, thus implying a decrease in CO2 emissions and a reduction
in costs related to their production. However, compared to a plain CSA cement, the blended systems
showed rather similar volume stability levels, whilst their compressive strength and porosity values
were, respectively, lower and higher at all the investigated aging periods
Serpentinites-water interaction in the S. Severino area, Lucanian Apennines, southern italy
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Re-use of natural clayey waste as supplementary cementitious material
Full text linkIn 2015 total world cement manufacture was estimated at 4.6 billion tons and the CO2 emissions from cement plants were equal to approximately 3.7 billion metric tons, representing about 7% of the global anthropogenic emissions. The utilization of innovative cements and/or supplementary cementitious materials (SCMs) represent a powerful tool for both reducing the CO2 footprint and producing more durable environmentally friendly materials.This paper investigates the possibility of using clayey reservoir sediments (RSs) calcined at 830°C as SCMs in a blended Portland cement; this binder, together with a reference one containing natural pozzolan, was submitted to hydration and mechanical tests for curing times ranging from 2 to 56 days. It has been found that RSs are very interesting SCMs inasmuch as their utilization, allowing a clinker dilution, leads to both CO2 emission decrease and energy saving; furthermore, the hydration behaviour and the mechanical properties of the blended cement were positively affected by the RSs addition
- …
