Aerated concreteAir-entraining admixtures create a system of pores of different sizes in concrete. These pores, calledalso “effective air” serve as space for expansion to eliminate pressures developed duringcrystallization of ice or de-icing salts. In general, desirable size of pores is considered to be between25 – 300 µm; larger pores cause unproportional deterioration of mechanical properties of concrete.Method most often used to determine measure of entrained aeration is so-called pressure method,which is carried out with a sample of fresh concrete. Nevertheless, this method gives no informationof space distribution of pores in concrete or their sizes. Spacing factor is another method ofdetermination of air content in concrete. This method tests hardened concrete and, usingmicroscopic measuring and special software, it is capable of determining detailed and complexinformation about size and distribution of different air pores in hardened concrete [8].Once concrete hardens, air pores stay in the form of voids. This is usually called a “system of airbubbles – pores” in hardened concrete. Main parameters of air pores are total air content, averagespacing of pores and specific surface of pores. The effective air consists of small enclosed pores ofmicroscopic size with diameter 10 to 300 µm. These micro-pores are evenly distributed throughoutthe mass of concrete. Relative distance between pores is called the Spacing factor. It is the distanceof travel of water before it can enter an air pore – this decreases the pressure.
Aerated concrete<br>Air-entraining admixtures create a system of pores of different sizes in concrete. These pores, called<br>also “effective air” serve as space for expansion to eliminate pressures developed during<br>crystallization of ice or de-icing salts. In general, desirable size of pores is considered to be between<br>25 – 300 µm; larger pores cause unproportional deterioration of mechanical properties of concrete.<br>Method most often used to determine measure of entrained aeration is so-called pressure method,<br>which is carried out with a sample of fresh concrete. Nevertheless, this method gives no information<br>of space distribution of pores in concrete or their sizes. Spacing factor is another method of<br>determination of air content in concrete. This method tests hardened concrete and, using<br>microscopic measuring and special software, it is capable of determining detailed and complex<br>information about size and distribution of different air pores in hardened concrete [8].<br>Once concrete hardens, air pores stay in the form of voids. This is usually called a “system of air<br>bubbles – pores” in hardened concrete. Main parameters of air pores are total air content, average<br>spacing of pores and specific surface of pores. The effective air consists of small enclosed pores of<br>microscopic size with diameter 10 to 300 µm. These micro-pores are evenly distributed throughout<br>มวลของคอนกรีต ญาติห่างระหว่างรูขุมขนที่เรียกว่าปัจจัยการเว้นวรรค มันเป็นระยะทาง<br>ของการเดินทางของน้ำก่อนที่จะสามารถป้อนรูขุมขนอากาศ - นี้ลดความดัน
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