This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects
generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions
and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack
as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or
siliceous and aluminous materials according to the ASTM C 618-94a.
The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio
in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was
used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak
also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic
ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine
fineness range, the reactive alumina (Al2O3r−) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO2r−) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is
due primarily to the chemical interaction between the gypsum and the C3A in the Portland cement and the reactive alumina (Al2O3r−) in the fly ash.
Fly ashes from the combustion of coal thermal power stations are commonly incorporated into portland cements and/or concretes
and mortars. The chemical and morphological composition of fly ashes, together with their particle size, make them suitable
as pozzolanic(non-calcic) or pozzolanic/hydraulic(highly calcic) additions to manufacture such building materials. This work
focuses on the incorporation of two different fly ashes (non-calcic but of very different Fe2O3(%) contents, fineness and morphology) to two ordinary portland cements (of very different mineralogical composition as well),
to determine the effects those have and the interactions they produce in the hydration reactions of portland cement. The main
techniques employed for this study have been: conduction calorimetry and Frattini test; secondary techniques applied have
also been: determination of setting times and analysis by X-ray diffraction and SEM. Analysis of the results obtained permitted
to find different effects of fly ash addition on the hydration reactions of portland cements. Thus, dilution and stimulation
effects augment with the increased fly ash percentage. Delay and acceleration of the reactions depend mainly on the type of
portland cement and are accentuated with increased fly ash contents. Their behaviour as concerns heat dissipation mainly,
depends on the type of fly ash used and is more pronounced with increased cement replacement. On the other hand, the pozzolanic
activity of these fly ashes has been revealed at 7 and 28 days, but not at 2 days. Finally, pozzolanic cements can be manufactured
using different portland cements and/or types of fly ashes, in the appropriate proportions and compatible qualities, depending
on the effect(s) one wish to enhance at a specific age, which is according to previous general conclusions drew out of sulphate
attack and chloride attack researches.
Dry mortars are an important group of building materials with a wide range of applications [ 1 ]. They represent dry mixtures of cement, aggregates, fillers and chemical additives [ 1 ]. The most common dry mortars
Lili Ország visited Italy five times between 1968 and 1972. During her travels she prepared numerous sketches and drawings, which are now held at the Archives of the Hungarian National Gallery. The six sketchbooks filled during her trips to Italy are dominated by registration of the Pompeii, Herculaneum and Naples experiences, nevertheless there are pages drawn full in Rome as well. So far art history literature has only briefly touched upon these sketchbooks. The present essay, through examples of those pages where the subject of sketches has been clearly identified, intends to analyse methods of picture construction and composition in the art of Lili Ország, and also to underline the importance of Italian, especially Pompeian experience in her works.
Preponderant majority of sketches — drawn with pencil, ball-point pen or marker as aide memoires — delineate painted walls of Pompeii, yet antique sculptures, some mosaics, and as an exception to the rule a few panel paintings and papyrus scrolls also come up in the sketchbooks. Latter also serve as specific examples for borrowing motifs.
Figural scenes among Pompeian frescoes hardly fascinated Lili Ország, it was rather the system of decorative wall-panes, their colours, the changing rythm of patches (that is the third Pompeian style), and also illusionistic architectural spaces (the second style) that made her trace them religiously. In her sketches she paid attention to exact representation of proportions and composition, the expressiveness of her outlines is exceptional. She registered colours in detail, using denominations that evoque material consistence. She precisely traced all injuries of walls, including abrasion, cracks or patches of mortar. She felt only those motifs (be human figures or objects) worth of treasuring for later use, that had an air of bizarre or peculiar. She loved pictures and sculptures with mystical influences, she was interested in instruments that could reach the desirable effect (worn down green walls, fragmented stuccoes).
The majority of sculptures drawn can be characterized by abundant drapery hiding the forms of human body. Representation of human figures in general can be marked by the lack of sensual visualisation, faces are scarcely ever individualised. Expressive power of figures, their emotions, states of mind are transmitted by postures and gestures.
While she had already lit on the basic elements of her paintings well before her Italian travels, the Pompeian experience was key to further development of her composing methods. This impulse unequivocally contributed to the creation of the Labyrinth-series. The division of the wall surface into smaller units, the lapsing system of picture panes, the rythm of coulorful, often pale patches served as essential sources of inspiration.
Gopalaratnam V. S., Abu-Mathkour H. J. (1987), Investigation of the pull-out characteristics of steel fibers from mortar matrices. Proceedings, International Symposium on Fiber Reinforced Concrete, Madras, Dec. 1987, pp. 2
Authors:SKM. Pothinathan, M. Muthukannan, N. Selvapalam, and S. Christopher Gnanaraj
dry curing shows the noticeable strength rise with 10% addition. L.K. Aggarwal [ 14 ] used epoxy emulsion and acrylic emulsion to modify the mortar and compared the workability and mechanical property. He noticed that the epoxy emulsion-based modified