Page 32 - Demo

SCIENCE & INNOVATION32 SCIENCE & INNOVATION AAC WORLDWIDE %u2022 2.2025Testing of innovative aerating agentBio-aerated autoclaved concreteAutoclaved aerated concrete is a construction material which, due to its low density and thermal insu,lation properties, has found wide use in the construction industry worldwide. Its mix composition, which has virtually remained unchanged since its initial development at the beginning of the 20th century, involves the addition of an aerating agent (aluminium powder or paste) to the cement slurry, which, reacting mainly with calcium hydroxide, produces H%u2082 bubbles that result in leavening (rising) of the mix. The current article presents the research carried out by ENEA on a different aerating agent, based on the interaction between hydrogen peroxide and brewer%u2019s yeast. The results led to a patent called BAAC (Bio-aerated autoclaved concrete).Piero De Fazio, ENEA/Trisaia Research Centre, Rotondella, Italy Giorgio Leter, formerly ENEA/Casaccia Research Centre, Rome, ItalyThe European Green Deal [1] sets the goal of making the EU the world%u2019s first climate-neutral zone by 2050 by consolidating a new awareness of environmental issues caused by climate change, drawing attention to the urgent need to reduce CO%u2082 emissions [2]. Consequently, the European Commission has adopted a series of proposals to transform EU climate, energy, transport and taxation policies and to reduce net greenhouse gas emissions by at least 55% by 2030, compared to 1990 levels.It is well known how the global construction sector heavily impacts on the environment given the great carbon footprint of traditional materials such as cement, clay, steel, etc. The data show that the construction sector contributes 5 - 12% of the total greenhouse gas emissions, considering the entire supply chain from the production processes of building materials to the construction of new buildings and/or renovation of old ones and their operation (heating and cooling are responsible for consuming about 40% of the EU%u2019s energy consumption) and finally the management of waste related to the construction sector. Therefore, to follow up on policies to mitigate the climate impact due to the industrial construction sector, it is essential to act on each of the production segments in order to increase their degree of sustainability.In this context, autoclaved aerated concrete (AAC) is an interesting solution that is already widely used in building construction, due to its main intrinsic characteristic of having a low density and the ability to guarantee excellent thermal and acoustic insulation that contribute to improving the building%u2019s environmental qualities.AAC was first developed in Sweden in the 1920s by architect Axel Eriksson who patented a process for producing a mixture of cement, calcined shale and aluminium powder that was subsequently treated at high temperature and pressure in an autoclave. A few years ago, the centenary of the invention of this building material was celebrated. Its most obvious characteristic is its high and homogenous porosity, which results in a lower density and better thermal conductivity compared to conventional concrete.AAC is a structural material, belonging to the cellular concrete family, with raw materials consisting mainly of sand, lime, cement, water and an aerating agent, the most common and widely used of which is aluminium powder/paste. Over time, there have been variations in the original mix design of AAC in order to improve its sustainability, especially with respect to the source of materials such as limestone or silica. An example of this is the use of industrial by-