Preparation and properties of porous aerated concrete

INTRODUCTION Porous concrete, especially Aerated Autoclaved Concrete (AAC) was first developed by a Swedish engineer between the years 1920 and 1932 [1]. He was searching for a material with the properties of wood, but without the disadvantages of wood. Near the end of World War II, AAC became widely used. Vast areas of cities and industries lay in waste and tremendous rebuilding became necessary, particularly in Germany and England, where wood and steel were scarce. Since 1980, there has been a worldwide increase in the use of AAC materials and new production plants are being built in the United States, Eastern Europe, China, Bahrain, India, Australia and other contries in the world [2-4]. Hence, AAC is increasingly used by developers, architects and homebuilders [5]. The first plant in North America opened in 1996. Four major AAC plants now exist in the United States. It is now being produced in more than 420 factories around the world [1,6]. Concrete made with natural aggregate originating from hard rock has a density within a narrow range because the specific gravity of most rocks varies little. Thus, in practice, the density of normal weight concrete lies within the range of 2200 to 2600 Kg/m [7]. Using concrete with a lower density is possible. Therefore, result in significant benefits. The use of concrete with a lower density permits construction on ground with a low loadbearing capacity. Furthermore, with lighter concrete, the framework can withstand a lower pressure, when compared to normal weight concrete. Concrete, which has a lower density, also gives better thermal insulation than ordinary concrete [7]. Due to the growing demand of AAC, a present paper is underway to investigate production of high quality AAC with changes to specification, raw materials and production procedures. This paper presents a technical review of the process, lab scale production method and some preliminary data of AAC blocks.