Effect of high strain rate and confinement on the compressive properties of autoclaved aerated concrete

Abstract

Autoclaved aerated concrete (AAC), also known as autoclaved cellular concrete, is a highly porous and light-weight material with a huge amount of closed air bubbles. It has been widely used in over 40 countries around the world to make masonry units such as infill walls or other nonstructural elements such as wall panels. Some structures during their service life might be exposed to blast and impact loads. Such extreme dynamic loads owing to their specific characteristics such as high amplitude and short duration induce very different structural responses and damage as compared to static and low-rate dynamic load. Understanding the properties of AAC material under dynamic and complex stress states is essential for accurate prediction of the response of structural components made of AAC subjected to highly dynamic loads. This study investigates the compressive behavior of AAC material under uniaxial quasi-static and impact and quasi-static triaxial loading tests. AAC material with nominal density of 500 kg/m3 was used to prepare specimens in all tests. For uniaxial compressive tests, the strain rate ranged from 3.3 × 10−5s−1 to 100 s−1 by using electric universal testing machine and INSTRON VHS 160/100–20 high-strain-rate testing system. A high-speed camera was used to capture the failure processes of AAC specimens during the tests. Based on testing data and high-speed camera images, the failure mechanism was investigated. Dynamic stress-strain curves under different strain rates were derived, and rate effects on the compressive strength were discussed. The corresponding empirical DIF (dynamic increase factor) relations were proposed. For quasi-static pseudo triaxial compressive tests, the deviatoric stress-strain curves of AAC specimens under different levels of confining pressure were obtained and compared. The damage induced by hydrostatic pressure and the corresponding failure modes were investigated. The compressive meridian and the empirical EOS (equation of state) relations were proposed based on the test data.