Lightweight concrete performance after producing of artificial lightweight aggregates in early 20th century moved to a new phase, so that the use of lightweight concrete in deck slabs of High Rise Buildings, bridge decks and other similar cases such as special application of lightweight concrete in oil extraction deck and oil-drilling basements.
Wide range of lightweight aggregates is used for producing concrete. Using appropriate materials and methods lead to achieve concrete unit weigh of 300 to 1850 kg/m3 and its corresponding strength about 3 MPa and in some cases upon to 60 MPa.
Lightweight concrete may be made by using lightweight aggregates, or by using of foaming agents, such as aluminum powder, which generates gas while the concrete is still plastic. Natural lightweight aggregates include pumice, scoria, volcanic cinders, tuff, and diatomite. Lightweight aggregate can also be produced by heating clay, shale, slate, diatomaceous shale, perlite, obsidian, and vermiculite. Industrial cinders and blast-furnace slag that has been specially cooled can also be used.
Pumice and scoria are the most widely used of the natural lightweight aggregates. They are porous, froth-like volcanic glass which come in various colors and are found in the Western United States. Concrete made with pumice and scoria aggregate weighs from 90 to 100 pounds per cubic foot.
Iran is one of the most seismically active countries in the world, being crossed by several major fault lines that cover at least 90% of the country. As a result, earthquakes in Iran occur often and are destructive. Therefore there is a serious need to investigate about lightweight construction and retrofitting in most part of Iran. On the other hand, Iran has adequate resources of lightweight aggregates, so lightweight concrete can be produced with local materials.
Among its advantages are less need for structural steel reinforcement, smaller foundation requirements, better fire resistance and most importantly, the fact that it can serve as an insulation material! It can cost more that sand and gravel concrete, and it may shrink more upon drying.
So far, CMI has been done various investigations on this subject. These investigations can be classified as follow:
Investigation of strength capacity of lightweight aggregates and non-structural leca.
Effect of steel and propylene fibers on lightweight concrete properties made by leca and pumice.
Economical assessment of lightweight concrete performance in ordinary concrete structures.
Translation and publication of Lightweight concrete books .
Investigation on strength and mixture design of scoria lightweight aggregate.
Producing of Leca.