During the first months of project implementation, consortium members met each other and discussed the details of the work, secondments, data sharing and other necessities for smooth running of the project.
In the first year, the work carried out within the project was mainly focused on the characterization of the raw materials with special attention to CBPD, which is a 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 the chemical and mineralogical composition of CBPD, as well as its physical properties, such as the particle size distribution. Knowledge of CBPD characteristics is essential for a reasonable development of any new system for its usage and helped us to proceed successfully during the following project stages.
Second and very wide task was development of a new type of cementless concrete, which contains CBPD and which will be usable instead of concretes based on Portland cement in some applications. At the same time, its preparation should be as simple and as cheap as possible, which relates to our efforts to use secondary raw materials as much as possible. Our concretes were based on alkali-activated blast furnace slag (AAS)-based binders, whose advantage is that they do not need curing at elevated temperatures. Unlike Portland cement, which hardens in the presence of a suitable amount of water, AAS also requires the presence of an alkaline activator (e.g. alkaline hydroxides, waterglass, etc.), which ensures the dissolution of slag particles to species that can build up a new solid structure with binding ability. Fresh and hardened properties of the prepared AAS-based materials depend on many factors and their combinations, where nature and dose of the alkaline activator and composition and dose of CBPD play crucial roles. Therefore, the effects of these and other factors were investigated in terms of consistency (how the material flows), setting time (period from mixing until the material is no longer workable), sufficient early and long-term strength, durability in various conditions, etc. Volume stability and tendency to surface cracking were also important aspects, as these belong to the most serious obstacles for wider utilization of AAS in practice.
This, was a real challenge, because by improving one parameter, another two were impaired. So, it was necessary to find a certain balance among all the desired aspects, without one significantly problematic. After optimization, we had to transfer our laboratory product to practice and verify its usability under conditions of larger scale of a concrete plant. Pilot production tests were successful and resulted in the production of various prefabricated products, such as concrete elements for railway marking or crash barriers. Along with these elements, many testing specimens were prepared to continue the testing of durability, strength, etc. Considerable attention was paid to the monitoring of the quality of the surface of our concretes, which resulted in further optimization and performance verification, during the pilot production tests. The advantage of developed concretes is that they can be produced using the devices and equipment commonly available in concrete plant.
It can be summarized that the project covered a wide range of scientific fields, from basic research with the participation of sophisticated instrumental techniques, to laboratory experiments with the pilot product produced on a large scale of concreting plants.
