Concrete and environment
Overview
Concrete being the most used construction material, its durability and sustainability are important research topics. The Concrete and Environment group of Prof. dr. ir. Nele De Belie studies the interaction between concrete structures and the environment. This includes both the effect of the environment on the concrete material (durability) and the contribution of cementitious materials and concrete structures to environmental impacts (sustainability).
To fully understand how concrete resists chemical and physical environmental actions, a clear understanding of binder reactions, hydration assemblages, microstructure and transport properties in concrete are needed. In view of an improved sustainability, the use of supplementary cementitious materials (SCMs) is gaining attention. This includes the more traditional SCMs (fly ash, blast furnace slag, silica fume, natural pozzolans, etc.), but also industrial by-products that more recently have come into the picture (municipal solid waste incineration ashes, biomass ashes, non-ferrous metallurgy slags, modified copper slags, etc.). Partial replacement of the Portland clinker by those SCMs will affect hydration products, microstructure and durability. The research of the Concrete and Environment team contributes to an in-depth knowledge of the resistance of concrete with alternative binder systems to a variety of aggressive environments. This includes degradation by organic and inorganic acids, sulphates, chlorides, carbonation, alkali-silica reaction, etc. The combination of various environmental and mechanical actions is hereby also addressed.
The interaction of concrete and natural stone with micro-organisms has since long been a focus point of the Concrete and Environment group as well. This includes biodeterioration (e.g. biogenic sulphuric acid corrosion), biocolonization, but also bioconsolidation by microbial carbonate precipitation and biological cleaning. Furthermore, self-cleaning concrete by use of TiO2 photocatalysis, novel biocides and water repellents has been investigated.
The Concrete and Environment group is furthermore one of the world-wide pioneers in the research on self-healing cementitious materials (under supervision of Prof. dr. ir. Nele De Belie and Prof. dr. ing. Kim Van Tittelboom). From early age onwards, concrete is prone to cracking due to shrinkage phenomena, temperature changes, mechanical loads, etc. Small cracks will not necessarily impair structural stability, but will affect durability and service life of the structure. Self-healing of those cracks by the inherent presence of unhydrated binder particles, or by smart additions, is not a utopia. As for natural materials, self-healing concrete can manage the damage autonomously. Smart additions that have been developed for this purpose include superabsorbent polymers (SAPs), bacterial granules and macro-encapsulated polymers.
The environmental impact of novel binders and concrete types are evaluated by a profound life cycle assessment (LCA). This includes aspects of allocation of impacts to by-products, and functional units taking into account service life and strength. The research is aiming to contribute to a circular economy, hence design for recycling is an important objective. In this view, Completely Recyclable Concrete, that at the end-of-life can be recycled as clinker meal, has been designed.