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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - GeoDust (Utilization of secondary raw material in geopolymers production)

Teaser

Summary

Portland cement production consumes a lot of energy, natural resources and produces huge amounts of greenhouse gases and also waste in the form of so called cement kiln bypass dust (CBPD). Therefore, utilization of CBPD together with other industrial wastes or byproducts in building industry would be more sustainable thanks to the utilization of the wastes as well as thanks to the reduction in the demands for Portland cement. The solution can be alkali-activated materials which have many other advantages such as durability or resistance to elevated temperatures. However, they have also some drawbacks, particularly extensive shrinkage, related cracking tendency and often fast setting time. Furthermore, comprehensive research focused on utilization of CBPD in alkali-activated materials has not been conducted yet. Therefore, the topic of our project is at hand.

The main aim of this project is to contribute to common 2050 goal to reduce society CO2 footprint by 80%. Concrete, most widely used construction material, whose production has serious environmental impact due to high energy demands, consumption of raw materials and greenhouse gasses, needs a search for greener alternative.
The project is also important for society on personal level. Exchange of knowledge and experience between academia and industry (production and R&I) creates much better understanding of each working environment, which is highly beneficial for mutual cooperation.

The overall objectives of this project are to establish strong partnership between scientific and industrial institutions across the European Union able to solve this as many others actual issues
To develop non-traditional concrete based on industrial byproducts and wastes, particularly cement kiln bypass dust (CBPD) and blast furnace slag, and thus contribute to sustainability of building industry
To develop methodology that would be adopted for CBPD characterization. As well as to investigate the role of CBPD in alkali-activated systems

Work performed

During the first months of project implementation consortium members and particularly the leaders of the beneficiaries met each other and discussed the details of the work on the project, secondment possibilities, sharing of information etc
During the first year, the work done within the project was mainly focused on the characterization of the used raw materials with special attention to CBPD, which is waste from Portland cement manufacturing and has only very limited possibilities of utilization. The main goal was to find the best set of methods needed for the determination of chemical and mineralogical composition of CBPD as well as its physical properties like particle size distribution. Knowledge of these CBPD characteristics is essential for reasonable development of any new system for its usage. During this task, among others, consortium members tried to characterize the same sample of CBPD using their own techniques and methodology. On this basis, plenty of appropriate methods and setting of their specific parameters were discussed resulting to final most suitable methodology. Therefore, this task was successfully accomplished.
The second and very wide task is development of new type of concrete which would be an alternative to traditional Portland cement-based concrete in some application. Simultaneously, our effort is the use of secondary raw materials as much as possible. The solution is to use alkali-activated blast furnace slag (AAS)-based binders. Unlike Portland cement which hardens in presence of suitable amount of water, AAS needs also the presence of alkaline activator (e.g. alkaline hydroxides, waterglass etc.) which ensures the dissolution of slag particles to species that can build up new solid structure. Both fresh and hardened properties of the prepared AAS-based materials depend on many factors and their combinations, the crucial role play particularly the nature and dose of alkaline activator and composition and dose of CBPD. Therefore, effect of these and other factors were investigated in terms of consistency (how does the material flows), setting time (period from mixing until the material is no longer workable), strengths and length changes in various environments. Nowadays, we have plenty of results which are helping us during the development of the material acceptable in all these parameters. Moreover, the mixture has to be robust enough to deal with variations in CBPD composition, which is one of the main problems which we have to solve. Simultaneously, the preparation of the resulting material should be as simple as possible and as cheap as possible.
It can be summarized that CBPD will be used in AAS only in a limited amounts since its high doses accelerate the setting time so extensively that some mixtures set during the mixing and it is impossible to cast them into the moulds. Generally, the higher the activator dose, the more robust the mixture is and also the higher the early strengths are. On the other hand, mixtures with low activator content can reach higher strengths from the long-term point of view and somewhat lower suffer from shrinkage. Nowadays, we are working on optimization of our mixtures. After that they will be tested in terms of durability and in semi-operating conditions of cement plant.

Final results

In this research field, there is almost no information regarding the role of CBPD in AAS, so any progress in this topic is highly valuable. Our results such as those summarized in the previous chapters are further investigated in more detail using sophisticated instruments for chemical and structural analyses. Thanks to them we can explore the chemistry of our systems responsible for their macroscopic behaviour. Using this approach we are finding the relationships between the composition of our materials and its performance. We have already published some of these findings and many others are promising base for publication in the near future. We expect that thanks to these experiments we will be able to at least partially predict the behaviour of AAS/CBPD materials from the CBPD composition, which is, as was already mentioned, highly variable. These should help us to introduce AAS/CBPD into the practice.