The possible use of sewage sludge ash (SSA) in the construction industry as a way towards a circular economy

The construction industry already recognises the strong business case for improving resource productivity. It is associated with circular economy system (CE), propagated by the European Union. Circular economy systems keep the added value in products for as long as possible and virtually eliminate waste. Transition to a more circular economy requires changes throughout value chains, from product design to new business and market models, from new ways of turning waste into a resource to new modes of consumer behaviour. These actions relate to all industries, including the construction industry. Nowdays, the increase in demand for construction materials as a result of development has called for an alternative way to develop or derive construction materials from different sources, including sewage sludge ash (SSA). SSA is produced after the firing process of sewage sludge, and it must be disposed by other means. Researches were already accomplished investigating the use of sewage sludge ash for the building materials manufacturing, such as produce bricks and tiles, as a raw materials for cement production, as aggregates for concrete and mortar, as a component of the synthesis of lightweight materials and as substitute for sand and/or cement in cement stabilized bases, subbases and embankments in road constuctions. A detailed description of each application as a way towards a circular economy is presented in this paper.