PWO SG TECH Eco²-crete mortars: sustainable and ecological concrete repair
The 1960s and 1970s saw an explosion of reinforced concrete structures in Europe, partly due to the aftermath of World War II. The rebuilding of cities and growing economy demanded fast and sustainable construction methods, for which reinforced concrete offered an ideal solution. When a concrete structure is carefully designed, executed, post-treated, inspected and maintained according to the applicable standards, a minimum service life of 50 years can be expected for Class S4 structures. The design life has been reached of a large number of concrete structures by 2025, which means that a wave of concrete repairs awaits us in which many classic repair mortars will be used. As the demand for repair and consequently the demand for repair mortars (to reconstruct and protect the original concrete structure) increases, the demand for cement production also increases. Consequently, optimising repair mortars is crucial in sustainable concrete repair.Traditional cement-based repair mortars have a high Portland clinker content (on average, four times more than concrete) and are applied with a low water/cement factor. As a result, a traditional repair mortar has a high environmental impact and is susceptible to autogenous shrinkage. Autogenous shrinkage induces cracks that act as pathways for pollutants, often failing to achieve the desired service life extension (GLV). This not only greatly affects the performance and (technical and environmental) durability of the mortar itself, but also has an impact on the repaired concrete. Furthermore, the development of sustainable repair mortars is imposed from some policy programmes and ideologies: the circular economy (CE), the Flemish Concrete Agreement (2022), Flemish Energy & Climate Plan (2021) and the European Green Deal (2020). Alternatives must be found to reduce the clinker content so that the cement industry can become carbon-neutral by 2050, as imposed in the Flemish Concrete Agreement, for example, and without degrading the mortar's performance. Two problems are identified. There is a need for ‘sustainable/green’ repair mortars and a need for the flow of knowledge and experience on the safe application of these sustainable repair mortars to stakeholders in the sector. From DUBiT, the pressing question remains: how can concrete damage be dealt with in a sustainable way? Sustainability is considered in all its facets: technical, economic, ecological and circular. Use is made of the Cembureau's 5C approach (valuable strategy to reduce CO2 emissions in the construction sector): less CO2 in clinker production, less clinker in cement, less cement in concrete, less concrete in structures, and ultimately less structures. This research mainly focuses on less clinker and cement in mortar, which increases the impact at the material level.The aim of this research focuses on the impetus for creating durable repair mortars in terms of durability and sustainability. Durability refers to the performance requirements of the mortar, where the mortar must maintain its function over the GLV. Sustainability refers to reducing environmental impact by, for example, using alternative Portland clinker substitutes such as Supplementary cementitious materials (SCMs). By using SCMs (residual products) (slag, geopolymers or bottom ashes), the aim is to reduce the environmental impact of a repair mortar.
Besides being an alternative to clinker, superabsorbent polymers (SAPs, polymers with very high absorption capacity cf. nappies) can be added to address the cracking problem due to autogenous shrinkage and the adverse effect on the GLV. SAPs have proven their usefulness in classic concrete structures where they respond to reducing shrinkage and associated cracking behaviour to extend the service life of the concrete structure. The aim is to find out to what extent SAPs and SCMS can positively influence the behaviour of repair mortars through experimental and literature research. Within the research year, the aim is to create a survey showing mortar properties as a function of mortar composition (the type of SAPs/used clinker alternatives and the amount added/replaced) and application method.
How can sustainable repair mortars be developed and applied to optimise ecological and technical performance, taking into account material selection, environmental impact and cost efficiency?
What traditional and alternative (commercial) repair mortars and SAP materials are available on the market or described in literature, what are their compositions and properties, and what is the necessary knowledge and experience to apply these eco-mortars?How do alternative binders and SAPs affect the workability, shrinkage, mechanical properties, adhesion and sensitivity of repair mortars for different application techniques and substrate surfaces? (Tested according to applicable standards)
