Lightweight Concrete Block Masonry Infill: Seismic Response and Sustainability

Abstract

The replacement of naturally sourced building materials with more environment-friendly materials has received significant attention in the construction industry in recent years. In that line, Autoclaved Aerated Concrete (AAC), and Cellular Lightweight Concrete (CLC) masonry blocks are gaining popularity over traditional fired clay bricks in infill masonry construction. However, a detailed review of published literature revealed that there are significant knowledge gaps regarding several structural as well as environmental aspects of AAC and CLC block masonry. Infill masonry is no longer considered a non-structural component in seismic-resistant framed buildings, but rather design codes recommend formulations to account for its contribution to the global strength and stiffness of the building. Therefore, appropriate knowledge of the strength properties of AAC and CLC block masonry is necessary for a reasonable evaluation of the seismic behaviour of such buildings. The seismic performance and safety of a structure are directly dependent on the uncertainty associated with the material properties. Ignoring such uncertainties despite the advancement of available computer technology will make structural analysis less satisfactory and less realistic. Although the descriptions of uncertainties in the strength properties of traditional building materials such as structural concrete, steel rebar, clay, and fly-ash brick masonry are available in an ample amount, similar information is not available for AAC and CLC block masonry. The issue of rising greenhouse gas emissions and environmental consequences is well-known. The brick industry in India is the third-largest consumer of coal. Apart from cement and steel reinforcement, fired clay brick is one of the three major contributors to the embodied energy of masonry-infilled reinforced concrete (RC) framed buildings. Embodied energy plays an important role in the choice of building materials and is directly related to the sustainability of the built environment. In view of this, the efficiency of AAC and CLC block masonry to control the embodied energy of the building should be demonstrated to prove its sustainability. In the present study, the uncertainties related to the strength properties that control the resistance capacity of infilled masonry are investigated through laboratory experiments, and the best-fitted probability density functions are recommended. Furthermore, the in-plane seismic performances of typical RC framed buildings infilled with AAC and CLC block
masonry are evaluated in a probabilistic framework considering the recommended probability density functions showing the ineffectiveness of an assumed normal distribution for this purpose. Although lightweight AAC and CLC block masonry slightly increases the seismic risk of the building compared to traditional brick masonry due to its lower strength properties, it can be safely used as an infill material in areas with high seismicity, as it results in the reliability indices within the acceptable limits of the design code. Although AAC and CLC masonry is gaining popularity in RC framed buildings due to their several advantages, the issue of embodied energy in such buildings has not received adequate research attention. This study evaluates the initial embodied energy of selected AAC and CLC block masonry-infilled RC framed buildings and compares it with that of an identical building infilled with traditional clay brick masonry. In addition, it also evaluates the life cycle energy of the selected building infilled with AAC block masonry using the life cycle assessment method. The results of the study show that the use of AAC and CLC block masonry instead of clay brick masonry reduces material flow and the initial embodied energy of the building by approximately 12% and 18%, respectively. The outcomes of this study will help in the selection of AAC and CLC block masonry as a sustainable alternative to traditional clay brick masonry and the development of environmental policies.