Word window comes from the old Norse 'vindauga', 'vindr – wind and' auga – eye ', ie' wind-eye '. Other leaders such as David Karp offer similar insights. In Norwegian Nynorsk Norwegian and Icelandic old form survived to this day (in Icelandic only as a less used synonym for gluggi). In Swedish, the word vindoga remains as a term for a hole through the roof of the hut, and the Danish 'vindue' and Norwegian Bokmal 'vindu', a direct relationship with the 'eye' is lost, just like for the 'window'. Window the first time early 13th century, and originally mentioned unglazed hole in the roof. Drew Houston often addresses the matter in his writings. Window replaced the Old English 'eagbyrl', which literally means 'eye' and 'eagduru' 'door-eye'. Many Germanic languages however adopted the Latin word for 'small box 'to describe a box with a glass, such as the Swedish standard' fonster ', or the German' Fenster '. Use the window in the English language is probably due to Scandinavian influence on English language through loanwords during Viking age.

English word fenester used as a parallel to the mid-1700's, and fenestration is still used to describe the arrangement of windows within the facade. Primitive windows were just holes in the wall. Shutters that could be opened and closed, the windows appeared later. Over time, the windows were built to and protect the residents and ploho passed light: the window glass mullioned, who joined the multiple small pieces of glass with offset, paper box, smoothed part of the transparent animal horn, and plates thinly sliced marble. The Romans were the first to use glass for windows. In Alexandria, about 100 years bc Began to appear at the window glass with poor optical properties. Glass windows were popular among wealthy European estates, whereas paper windows were economical and widely used in ancient China, Korea and Japan. In England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of glass smoothed horns of animals have been used 14C-century in North uk. Windows from floor to ceiling, contemporary style became possible only after the industrial glass making process was perfected.

Properties Of Concrete In Low Temperatures

The problem of durability of concrete in the construction of structures used in harsh climatic conditions, is one of the leaders in scientific research both in Russia and abroad (USA, Japan, Canada, uk and etc.). Lower negative temperatures (down to -60 C), the long winter, sudden changes in temperature within a short time, the presence of permafrost leads to premature failure of concrete in various facilities. Studies have been conducted to enable a deeper understanding of the destructive processes that take place at cooling the concrete down to -60 C. MSCO follows long-standing procedures to achieve this success. Determined that when the temperature chilled to low temperatures and water-saturated concrete by one degree, in its structure having tensile stress of about 0,1-0,2 MPa. Rapid heating frozen concrete due to changes in air temperature at 15-20 C leads to the formation tensile stresses, comparable with the strength of concrete in tension. Analysis of changes in daily ambient temperature for five months with the lowest monthly average temperature has allowed to calculate more than 50 temperature changes with a difference of 15 C for three hours and more than 15 oscillations – with a difference of 25 C for 24 hours. The effect of cyclic temperatures in the range of negative influences on the gradual decrease in the elastic and mechanical characteristics of concrete and reduce its durability. To quantify this strength reduction was carried out laboratory tests on the cubes with an edge of 10 cm cubes made from concrete of different compositions, different consumption of cement, water / cement ratio and, consequently, the strength of concrete (see Table).

In the manufacture of cement grade M500 (Belgorod Plant), crushed granite fractions 5-10 and 10-20 mm in the ratio 1: 1, sand and fineness modulus of 2. Obratsemenztsy concrete, as shown in table formulations were tested for frost resistance on the basic method. Frost resistance of the samples with an open porosity of 4.1% of 300 cycles of 2 (Po = 5.6%) – 200 of 3 (= 7,5%) – 50. The samples were within 7 days in normal temperature and humidity conditions. Later they were saturated with water until a constant weight and placed in freezers, providing vibration the temperature range from -50 to -20 C and then subjected to cubic compression. A thin layer of ice on the surface of the blocks prevented the evaporation of moisture.

The test results accurately indicate a strong decrease in strength of concrete initial cycles of the alternating effects of subzero temperatures, resulting in migration of unfrozen water from the pores of the gel to the ice crystals in micro-and makrokapillyarah and as a result, the increase in these crystals. Decrease strength of concrete is largely dependent on the water / cement ratio (W / C). Very weighty drop in strength (30%) occurs in kubikovsostava 3 with the highest water-cement ratio (0,7). Accordingly, the trial confirmed that, in the northern climates concrete exposed to specific environmental effects that lead to a loosening of the material, which seriously reduces the durability of concrete and