جمع شدگی بتن های سبک و روشهای اندازه گیری آن در استاندارده ا و ادبیات فنی..pdf

The use of lightweight concrete has become more prevalent in recent decades due to its economic benefits, improved energy efficiency, and reduced dead load on structures. Lightweight concrete can be categorized into two main types: lightweight aggregate concrete and aerated concrete. However, due to the low modulus of elasticity of lightweight aggregates and the lack of sufficient restraint in the cement paste structure, shrinkage in lightweight aggregate concrete increases. In aerated concrete, the porous structure allows for the formation of tensile stresses in the pores, increasing shrinkage compared to ordinary concrete. Shrinkage is a process that occurs with a reduction in concrete volume without external loading, which can cause cracking and damage in restrained members of a structure, such as slabs, walls, panels, and building components. Therefore, various standards have proposed different allowable shrinkage values for lightweight concrete. This article reviews the proposed measurement methods and allowable shrinkage values for lightweight concrete, comparing the results and conditions governing international and national standards. Additionally, the article collects and examines the various values reported in the technical literature for the shrinkage of different types of lightweight concrete, as well as the measurement methods and reasons for the differences in these values.