Reinforced concrete is a unique material, the basis of our modern civilisation, enabling the construction of buildings, bridges, roads, harbours, tunnels and more, especially during the last century. Concrete is an outstanding material in terms of strength and resilience, cheap and relatively easy to produce.

However, concrete still has its limitations, including deterioration over time in some harsh exposure conditions like an acidic environment, to which some industrial facilities are submitted to. Hydrated cement products contained in concrete such as portlandite and C-S-H gel react with acid and a soft and loose residue is formed. As a result, the concrete is highly eroded, the porosity increases significantly, and the strength decreases drastically. Moreover, the steel reinforcement can become corroded, and the damage be accelerated, decomposing the whole concrete structure.

Some supplementary cementitious materials like fly ash or silica fume reduce permeability and increase resistance to acid attack but the effect is somehow limited. Protective coatings are another option with some disadvantages: they are expensive, prone to failure at any defect point and require periodic reapplication.

One promising alternative is the use of geopolymers. These materials show significant potential for resistance to acid attack, yet several scientific and technological challenges remain unresolved. Furthermore, the Spanish construction industry is not yet fully equipped to incorporate geopolymers into standard practice. Another consideration is the availability of geopolymer binders, which often come from industrial waste streams. Ideally, these waste streams should be locally accessible near the application site to reduce costs and environmental impact.

The challenge lies in developing a user-friendly geopolymer that can be seamlessly integrated into the existing concrete industry while offering maximum resistance to acid attack. Such a geopolymer should also be formulated using locally available waste streams in northern Spain, including the activator. Other out of the box solutions would be also considered.