Concrete production is a major contributor to global CO₂ emissions, responsible for approximately 80% of the emissions in the construction sector. This high emission level is primarily due to the use of clinker, an energy-intensive component of cement. Reducing the environmental impact of concrete therefore depends on producing and reusing high-quality residual cementitious fines (RCF) derived from End-of-Life (EoL) concrete. The process of obtaining high-quality RCF begins before concrete demolition, where identifying the cement type in existing concrete is crucial for high-value downstream processing. This study explores the suitability of currently available methods for identifying binder types in (destructively obtained) RCF and evaluates which of these methods could potentially be suitable for non-destructive identification of binder types in the original concrete. The methods investigated include handheld X-ray fluorescence (HXRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), titration and selective dissolution. To assess their binder type identification potential, RCF powder samples obtained from concretes of known composition were analysed first. Results show that all five methods can distinguish and identify three binder types (Portland cement, blast furnace slag cement and fly ash cement) based on variations in the chemical and mineralogical properties of the RCFs derived from their respective concretes. HXRF currently shows the greatest potential for rapid, non-destructive, in-situ identification of binder types present in EoL concrete, while XRD and FTIR also show potential.

Reducing CO2 emissions from concrete production requires effective recycling of cement, particularly its clinker component. Significant emission reductions depend on innovative techniques that extract high-quality cement fractions from recycled concrete, beginning with source separation strategies before demolition. This study developed a practical measurement approach using handheld X-ray fluorescence (HXRF) to identify cement types (i.e. cement classifications such as CEM I, CEM II/B-V, CEM III/B) in End-of-Life concrete. The research was conducted in two phases: First, laboratory testing of seven powder samples (milled river gravel and sand, three cement types: CEM I, CEM II/B-V and CEM III/B along with blast furnace slag and fly ash) and three cement paste prism types containing the three cement types established optimal measurement parameters and assessed moisture influence. Second, field measurements were taken on outdoor concrete blocks, containing the three cement types, after one year of weather exposure. Measurements were conducted on both the exposed surface and subsurface layers (after removing 0.1–5 mm of material). Results showed that powder samples can be accurately characterized with 10-second measurements, while concrete blocks require at least 20 s. HXRF measurements demonstrated good reproducibility with low coefficients of variation (CV) values, ensuring reliable cement type identification. Surface measurements are reliable only when the concrete is unaltered: coatings, paint, or weathering negatively affect accuracy, necessitating removal of the surface layer. Cement types were successfully distinguished using oxide concentrations (Al₂O₃, Fe₂O₃, P₂O₅, MgO) and their ratios (CEM III/B: Al2O3/Fe2O3 > 9.0, MgO/Fe2O3 > 3.0, MgO/CaO > 0.11, Fe2O3/Al2O3 < 0.11 and Fe2O3/CaO < 0.04; CEM II/B-V: P2O5/CaO > 0.005 and P2O5/Fe2O3 > 0.1; CEM I: P2O5/CaO < 0.005 and P2O5/Fe2O3 < 0.1). This study demonstrates that handheld XRF enables fast and reliable in-situ identification of the three studied cement types, supporting improved source separation and cement recycling strategies.

The clinker in cement largely determines the environmental footprint of concrete. Therefore, concrete recycling should focus on retrieving high-quality cementitious fractions to replace clinker. This requires a shift from current traditional recycling techniques towards innovative recycling methods, enabling recovery of not only clean secondary aggregates, but also residual cementitious fines (RCF), potentially eliminating the carbon dioxide emissions associated with them. The production and upcycling of RCF offer new implementation routes that were previously deemed unfeasible. However, the properties of RCF may vary based on their origin, affecting their replacement and upcycling potential. Consequently, assessing the original concrete quality, with a focus on the binder type, before demolition is important. A handheld x-ray fluorescence technique appears promising for this purpose. To achieve effective separation of clean secondary aggregates from the original cementitious content, innovative crushing and separation techniques are needed. Additionally, electrostatic separation shows significant research potential for further optimizing RCF.

The environmental footprint of concrete is largely influenced by the binder. It is therefore of high interest to investigate the potential reuse of the binder retrieved by modern separation techniques. However, studies found that the recycled cement fraction (RCF) still contained a certain amount of siliceous concrete aggregates, which forms an obstacle in the upcycling of RCF. In this study, the potential of electrostatic separation as a method to separate cementitious binder (hydrated and unhydrated) and sand (silica) is evaluated. Different cementitious powders and silica (sand) were prepared, resulting in a total of 9 powders and 8 mixtures. The mixtures consisted of a combination of silica and one of the cementitious powders (50/50 wt%) with a particle size of the components <125 μm. The potential of the studied technique was evaluated through charging measurements and x-ray fluorescence (XRF). Silica was assumed to contain no CaO and the detected CaO was therefore assigned to the cementitious powders. Results showed that silica and silica-rich fly ash (FA) particles became negatively charged, blast furnace slag (BFS) particles remained largely charge neutral and all other cementitious particles obtained a positive charge. Through electrostatic separation an enrichment of the cementitious binder fraction for all mixtures was obtained at the negative electrode. FA-Silica achieved the highest enrichment (89.9%), CEM III/B-Silica the lowest (4.7%) and the hydrates were enriched ranging from 28.0 to 31.8%.