No abstract

No abstract

No abstract

This paper deals with the pozzolanic reactivity of pyrogene oxides (represented by Aerosil) that belong to the colloidal silicas. Pyrogene oxides are highly reactive pozzolanic nanoscale additives. They react much faster pozzolanically than other commonly used pozzolans and in this way they consume the available calcium hydroxide in a much shorter time. It is shown by using in situ X-ray transmission microscopy, pH-change measurements and the strength property results that Aerosil begins to react as early as the first hour of contact with both the added calcium hydroxide in solution and with the products of the tricalcium silicate (C 3 S) hydration reaction. In comparison with the other commonly used pozzolans, that is, silica fume, pyrogene oxides contribute by developing a better early and final strength. The concrete specimens that were cast by combining silica fume with small quantities of Aerosil were considered to belong to the ultra high performance class and were additionally characterised by finer pores and reduced total porosity.

In the course of the actual investigation, we focused our research on the extraction of the orange peel extract of "Moro" cultivars grown in Albania using ultrasonic and soxhlet extractions techniques. The ultrasonic extractions performed in "SONOREX TK 52" 40 -60V / 100 W, using methylene chloride and applying sonication times up to two hours, revealed the presence of more than 20 components among which limonene, as the major extract component represents more than 91 % of the extract, followed by linalool, βmyrcene, decanal, α-pinene and valencene. More than 90 % of the extraction yield was obtained within 30 min. of extraction. The ratio between extracted components changed significantly in this method while using various solvents. The highest extraction yield was recovered when using methanol (0.548 %) followed by methylene chloride (0.414 %), hexane + acetone (0.272 %), hexane (0.141 %). In parallel to this method, the soxhlet extractions performed in a 20 ml soxhlet extractor for 6 hours (56 cycles) using the same solvents showed surprisingly lower extraction yields and different component ratios for all of them. In hexane + acetone the percentage of limonene was 85 %, meanwhile, in methanol this percentage decreased until 43 %. In this comparison the advantage of ultrasounds in desorption, diffusion and dissolution of components from the sample matrices is obvious.