Due to the high CO 2-footprint of ordinary Portland cement (OPC), the search for alternative binders is now in a full swing. Rankinite-which is a hydraulically inactive material and low in calcium, is a real alternative to OPC, as it absorbs the harmful greenhouse gas from the air through carbonation hardening. Nevertheless, the carbonation hardening has not yet been fully clarified and sufficiently investigated. In this study we show that rankinite achieves a final strength exceeding 100 MPa at 45 °C and 24 h, whereby the binder is only ~ 50% carbonated. The reaction is diffusion limited while a dense layer of carbonation products around the rankinite grains hinders a higher degree of carbonation. The carbonation reaction could be fully characterized by spatially resolved microanalysis such as LA-ICP-MS, NMR and XRD. Finally, durability tests show the excellent suitability of the rankinite binder for a wide range of applications, making it an attractive material not only from an environmental point of view. Concrete is the second largest processed commodity after water consumed annually by the population of Earth 1. Due to such vast demand for the building materials, ordinary Portland cement (OPC) industry is responsible for over 5% of global anthropogenic greenhouse gas emissions, with almost equal amount of CO 2 emitted to the atmosphere after production of one tonne of cement 2-4. Accordingly, the scientific community is struggling to find the solutions for greenhouse gas mitigation and reduction of the negative effect of the cement production. Even though, in the past decades many options to alleviate the adverse effect of OPC production to the environment were proposed 5 , however, recent studies have shown that strategies like clinker substitutions, alternative fuels and/or improved energy efficiency alone will not be sufficient enough to meet the target CO 2 reductions 6. Thus, finding alternative cementitious materials with lower CO 2 footprint than OPC is one the major challenges for the building material industry and the scientific community. At the moment, one of the most promising approaches is the production of low-lime calcium silicate cement (CSC) 7-11. This type of binding material not only requires lower amounts of limestone but also has lower production temperature, thereby resulting in much lower CO 2 emissions 12. Moreover, such binders are environmentally amicable not only due to lower CO 2 emissions, but also for the ability to permanently store CO 2 in the concrete structure in their carbonation hardening process 13. Implementation of such efficient carbonation technologies can potentially lead to cementitious materials becoming one of the largest global CO 2 sequestration sectors 14. Rankinite-Ca 3 Si 2 O 7-is one of such low lime calcium silicates that can be used as an alternative binder that gained more interest recently 7,15,16. Since the CaO/SiO 2 ratio of rankinite is almost twice lower than of ordinary cement, thus it requires lower amounts of calcareous raw materials. The fuel and...
In almost all applications of concrete components, both the transport of substances such as chlorides, sulphates, acids, CO2, etc. through the pore structure into the concrete and the resulting local chemical and physical processes have a negative effect on the lifetime of the structure. Most data are actually obtained from layer-by-layer mechanical sampling of, for instance, bore dust, followed by chemical analysis. Several groups have previously demonstrated the enormous potential of LA-ICP-MS for monitoring these multi element processes both qualitatively and quantitatively and with high spatial resolution. However, there has been no fundamental investigation of laser-material interaction, aerosol particle formation, fractionation analysis or the effect of cement-specific parameters such as the water to cement (w/c) ratio on signal intensity. This paper presents the ablation mechanisms of a frequently used 213 nm quintupled Nd:YAG ns laser operating on the HCP (hardened cement paste) multi-phase system in comparison with amorphous and well-characterized NIST 612 glass. It includes energy-signal considerations, crater evaluations after multiple shots using different energy densities and aerosol structures captured on filters. The investigation determined a linear energy to signal behavior in a range of 2–6 J/cm2, while the ablation mechanism is different to common mechanisms obtained for glass or brass. The aerosol captured on the filter material displays cotton-like structures as well as defined spherical particles, which is comparable to observations made with NIST glass aerosols.
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